xace-50

®

X ace ace 5.0 Online Help printed version

August 2006 Heat Transfer Research, Inc. 150 Venture Drive College Station, Texas 77845 USA © Heat Transfer Research, Inc.

Heat Transfer Research, Inc. (HTRI), the global leader in process heat transfer and heat exchanger technology, was founded in 1962. Today our industrial research and development consortium serves the engineering needs of over 600 companies in more than 45 countries. We conduct application-oriented research on pilot-scale equipment at our research facility. HTRI staff use this proprietary research data to develop methods and software for the thermal design and analysis of heat exchangers and fired heaters. In addition to research data and software, we provide technical support and offer training, consulting, and contract services to both members and non-member companies. Our expertise and dedication to excellence assure our customers of a distinct competitive advantage and a high level of operating confidence in equipment designed with our technology.

No part of this publication may be reproduced in any form without permission in writing from HTRI © Heat Transfer Research, Inc., All rights reserved.

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X ace ace Online Help, printed version

Table of Contents

Table of Contents Page X ace ace Online Help, printed version .......................... ............. .......................... .......................... .......................... .......................... .......................... .................... ................... ............ 1 X ace ace Overview......................................................................................................................................

1

Input Panels ........................... .............. ........................... ............................ ............................ ........................... ........................... ............................ ................... ................... ............................ ................ 3 Input Summary Summary panel ...................... ................................ ..................... ...................... ...................... ...................... ..................... ..................... ...................... .......................... ............... 4 Case Mode ........................... ............. ............................ ............................ ............................ ............................ ............................ ............................ ..................... ............... ........ 4 Geometry input panel group ........................... ............. ........................... ........................... ........................... ........................... ............................ .................... ........... ..... 5 Unit panel.............. panel......................... ..................... ..................... ...................... ...................... ...................... ..................... ..................... ...................... ................. .................. ............ 5 Unit type ........................... .............. ........................... ........................... ........................... ........................... ........................... ........................... ....................... ................ ...... 6 Fan arrangement....................... arrangement......... ............................ ............................ ........................... ........................... ............................ ............................ ................... ..... 7 Diagram of Fan Arrangements ........................... ............. ............................ ........................... ........................... ............................ ................ 7 Hot fluid location...................... location........ ............................ ............................ ............................ ............................ ............................ ............................ ................. ...... ... 7 Tube orientation ............................ .............. ............................ ............................ ............................ ............................ ............................ ........................... ............... 8 Flow type............. type ........................... ........................... ........................... ............................ ........................... ........................... ........................... ....................... ............... ..... 8 Diagram of Cocurrent Flow......................... Flow........... ............................ ............................ ............................ ............................ ...................... ........ 9 Diagram of Countercurrent Countercurrent Flow .................... ............................... ...................... ...................... ...................... ..................... ................ ...... 9 Number of bays in parallel per unit .................... ............................... ...................... ..................... ..................... ..................... .................... .......... 9 Number of bundles in parallel per bay .................... .............................. ..................... ..................... ..................... ..................... ................ ...... 9 Number of services ........................... .............. ........................... ........................... ........................... ........................... ........................... .......................... ............ 10 Number of tubepasses per bundle.................................................................................... 10 Nozzle database database ..................... ................................ ...................... ...................... ...................... ...................... ...................... ..................... ..................... .............. ... 10 Schedule ............................. ............... ............................ ............................ ............................. ............................. ............................ ............................ ................... ......... .... 10 Entry type/ Exit type .......................... ............. ........................... ............................ ........................... ........................... ........................... ......................... ............ 11 Diagram of Tubeside Nozzle Types Types ...................... ................................. ...................... ..................... ..................... ..................... .......... 11 Tubeside nozzle inside diameter :Inlet :Inlet ..................... ................................ ...................... ...................... ...................... ...................... ............. 11 Tubeside nozzle inside diameter :Outlet........................................................................... 11 Number of nozzles per bundle: Inlet Inlet ........................... ............ ............................. ............................ ............................ .......................... ............ 12 Number of nozzles nozzles per bundle: Outlet ..................... ................................ ..................... ..................... ..................... ..................... ............... .... 12 Fans panel........................... panel...................................... ...................... ..................... ..................... ...................... ...................... ..................... ..................... ............... .............. .......... 13 Number of fans per bay .................... ............................... ..................... ..................... ..................... ..................... ..................... ..................... ................. ...... 13 Fan diameter ............................ .............. ........................... ........................... ............................ ............................ ........................... ........................... ................... ....... .. 14 Radial fan tip clearance clearance ..................... ............................... ..................... ..................... ..................... ..................... ..................... ..................... ................ ...... 14 Total combined fan and drive efficiency............................................................................ 14 Fan

manufacturer.............................................................................................................. 14

Maximum sound pressure level ......................... ........... ........................... .......................... .......................... .......................... ........................ ........... 15 Number of fan shaft lanes per bundle............................................................................... 15 © Heat Transfer Research, Inc. All rights reserved. Confidential: For HTRI member use only.

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Fan shaft lane width.......................................................................................................... 15 Fan ring type ........................... .............. ........................... ............................ ............................ ........................... ........................... ............................ .................. ....... ... 16 Diagram of Fan Ring Types........................................................................................ 16 Optional Optional panel ..................... ............................... ..................... ..................... ..................... ..................... ..................... ..................... ..................... ................... ................ ........ 17 Steam coil present present ..................... ................................ ..................... ..................... ...................... ...................... ..................... ..................... ...................... ............. 17 Fan area blockage ......................... ............ ........................... ........................... ........................... ........................... ........................... ........................... ............... .. 17 Free area in hail screen ..................... ................................ ...................... ...................... ...................... ...................... ...................... ...................... ............. .. 18 Free area in fan guard .................... ............................... ...................... ...................... ...................... ..................... ..................... ...................... ................. ...... 18 Louvers present ........................... ............. ............................ ............................ ............................ ............................ ............................ ............................ ................18 Relative humidity................ humidity.......................... ..................... ...................... ..................... ..................... ...................... ..................... ..................... .................... .......... 18 Wet bulb temperature temperature .................... ............................... ..................... ..................... ...................... ..................... ..................... ...................... ................... ........ 18 Dew point temperature...................................................................................................... 19 Maximum Maximum ambient ambient temperature temperature .................... ............................... ...................... ..................... ..................... ...................... ..................... .............. .... 19 Minimum ambient temperature temperature .................... ............................... ..................... ..................... ..................... ..................... ..................... ................ ...... 19 Header box depth.............................................................................................................. 19 Diagram of Air-Cooled Exchanger Dimensions.......................................................... 19 Header box plate thickness............................................................................................... 20 Header box height............................................................................................................. 20 Header box width .................... ............................... ...................... ..................... ..................... ...................... ..................... ..................... ...................... ............... ....20 20 Total tubesheet tubesheet thickness thickness ..................... ................................ ...................... ..................... ..................... ...................... ...................... ...................... ........... 21 Number of intermediate tube supports.............................................................................. 21 Width of intermediate tube supports ........................... ............. ........................... ........................... ........................... ........................... .............. 21 Design pressure................................................................................................................ 21 Design temperature........................................................................................................... 22 Plenum chamber type .......................... ............ ............................ ........................... ........................... ............................ ............................ ...................... ........ 22 Ground clearance to fan blade.......................................................................................... 22 Diagram of Induced Draft Unit Unit Ground Clearance Clearance ......................... ............ ........................... ........................... ............... 23 Diagram of Forced Draft Unit Ground Clearance....................................................... 23 Bundle panel................... panel.............................. ..................... ..................... ...................... ..................... ..................... ...................... ..................... ..................... .................... ......... 24 Default bundle type .................... ............................... ..................... ..................... ..................... ..................... ..................... ..................... ..................... ............. ...24 24 Diagram of Bundle Layout Choices............................................................................ 25 Number of tuberows.......................................................................................................... 25 Tubes in odd rows............................................................................................................. 26 Tubes in even rows........................................................................................................... 26 Diagram of Tubes in Odd/Even Rows ............................ .............. ............................ ........................... ........................... ................. ... 26 Tube layout layout ..................... ............................... ..................... ...................... ..................... ..................... ...................... ..................... ..................... ..................... ............. ... 27 Diagram of Tube Layouts........... Layouts ..................... ..................... ...................... ...................... ...................... ..................... ..................... ................ ..... 27 Tube form.......................................................................................................................... 27 Page iv

© Heat Transfer Research, Inc. All rights reserved. Confidential: For HTRI member use only.

X ace Online Help, printed version

Table of Contents

Bundle width...................................................................................................................... 27 Diagram of Bundle Width............................................................................................ 28 Clearance, wall to first tube............................................................................................... 28 Side seals.......................................................................................................................... 28 Tube length ....................................................................................................................... 28 Total unfinned tube length ................................................................................................ 28 Additional unheated tube length ....................................................................................... 29 Equivalent tube length in tube bends for U-tubes............................................................. 29 Passes for Rows with Defined Passes Bundle Type Grid................................................ 29 Tube Types panel.................................................................................................................... 30 Add button......................................................................................................................... 30 Delete button..................................................................................................................... 30 Tube name ........................................................................................................................ 30 Tube type .......................................................................................................................... 30 Tube internals ................................................................................................................... 30 Tube Geometry page ........................................................................................................ 31 Tube material code..................................................................................................... 31 Tube thermal conductivity........................................................................................... 31 Tube OD ..................................................................................................................... 32 Wall thickness............................................................................................................. 32 Equilateral layout........................................................................................................ 32 Transverse pitch......................................................................................................... 33 Longitudinal pitch........................................................................................................ 33 Diagram of Tube Pitches ..................................................................................... 34 Table of Tube Pitches.......................................................................................... 35 f- and j-Curves page.......................................................................................................... 36 Outside/Airside f- and j-factors ................................................................................... 37 Tubeside f- and j-factors............................................................................................. 38 Twisted Tape page............................................................................................................ 38 Twisted tape thickness ............................................................................................... 38 L/D 360-degree twist .................................................................................................. 38 Twisted tape width...................................................................................................... 39 Micro-fin page ................................................................................................................... 39 Diagram of Micro-fin Tube Insert ......................................................................... 39 Number of fins ............................................................................................................ 40 Fin height....................................................................................................................40 Fin thickness............................................................................................................... 40 Tube inside diameter .................................................................................................. 40 © Heat Transfer Research, Inc. All rights reserved. Confidential: For HTRI member use only.

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Fin helix angle ............................................................................................................41 Fin apex angle............................................................................................................ 41 High Fins page .................................................................................................................. 41 Load from Databank button........................................................................................ 42 Dialog Box, Fin Geometry for High-Finned Tubes............................................... 42 Unset Bank Fin button ................................................................................................ 42 Bank fin code.............................................................................................................. 42 Bank Fin Codes.................................................................................................... 43 Fin type....................................................................................................................... 43 Diagram of Circular Fin ........................................................................................ 44 Diagram of Serrated Fin....................................................................................... 44 Diagrams of Rectangular and Plate (Continuous) Fin......................................... 44 Fin density .................................................................................................................. 45 Fin base thickness...................................................................................................... 45 Fin tip thickness.......................................................................................................... 45 Fin material................................................................................................................. 45 Fin material thermal conductivity................................................................................ 46 Fin bond resistance .................................................................................................... 46 Fin efficiency............................................................................................................... 46 Over-fin diameter........................................................................................................ 47 Diagram of Fin Measurements............................................................................. 47 Split segment height................................................................................................... 47 Split segment width .................................................................................................... 48 Height of rectangular section...................................................................................... 48 Width of rectangular section....................................................................................... 48 Low Fins page................................................................................................................... 48 Load from Databank button........................................................................................ 48 Load from Databank Dialog Box.......................................................................... 49 Databank type ............................................................................................................ 49 Tube dimensions ........................................................................................................ 49 Fins per unit length.....................................................................................................50 Fin root diameter ........................................................................................................ 50 Fin height....................................................................................................................50 Fin thickness............................................................................................................... 50 Outside area/length .................................................................................................... 51 Wall thickness under fins............................................................................................ 51 Stud Fins page .................................................................................................................. 51 Number of stud rings .................................................................................................. 51 Page vi



Table of Contents

Typical Stud-Finned Tube Geometry................................................................... 52 Number of studs in each ring...................................................................................... 52 Typical Maximum Stud Density............................................................................ 52 Stud length ................................................................................................................. 52 Stud diameter ............................................................................................................. 53 Bundle Layout panel................................................................................................................ 53 User defined tube pass layout .......................................................................................... 53 Legend Details .................................................................................................................. 54 Bundle Layout Tube Information....................................................................................... 54 Natural Draft panel .................................................................................................................. 55 Wind velocity..................................................................................................................... 56 Recovery (chimney) length ............................................................................................... 56 Recovery (chimney) width................................................................................................. 56 Recovery (chimney) height ............................................................................................... 57 Plenum length ................................................................................................................... 57 Plenum width..................................................................................................................... 57 Plenum height ................................................................................................................... 57 Diagram of Plenum Height ......................................................................................... 58 Diagram of Plenum Height, Forced Draft Units.......................................................... 58 Diagram of Plenum Height, Induced Draft Units ........................................................ 59 Process input panel........................................................................................................................ 59 Fluid name............................................................................................................................... 61 Fluid phase .............................................................................................................................. 61 Airside flow rate units .............................................................................................................. 61 Flow rates ................................................................................................................................ 62 Inlet fraction vapor ................................................................................................................... 62 Outlet fraction vapor ................................................................................................................ 62 Inlet temperature ..................................................................................................................... 62 Outlet temperature................................................................................................................... 63 Inlet pressure........................................................................................................................... 63 Allowable pressure drop .......................................................................................................... 63 Fouling resistance ................................................................................................................... 63 Fouling layer thickness ............................................................................................................ 64 Diagram of Fouling Resistance vs. Layer Thickness........................................................ 64 Exchanger duty........................................................................................................................ 66 Duty/flow multiplier .................................................................................................................. 66 Design input panel group ............................................................................................................... 66 Design Geometry panel........................................................................................................... 67 © Heat Transfer Research, Inc. All rights reserved. Confidential: For HTRI member use only.

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Bundle width checkbox ..................................................................................................... 67 Bundle width – Specified................................................................................................... 68 Bundle width – Minimum................................................................................................... 68 Bundle width – Maximum.................................................................................................. 68 Bundle width – Step Size.................................................................................................. 69 Tubepasses checkbox ...................................................................................................... 69 Tubepasses – Specified.................................................................................................... 69 Tubepasses – Minimum.................................................................................................... 70 Tubepasses – Maximum................................................................................................... 70 Tubepasses – Step Size ................................................................................................... 70 Face velocity checkbox..................................................................................................... 70 Face velocity – Specified ..................................................................................................70 Face velocity – Minimum .................................................................................................. 71 Face velocity – Maximum ................................................................................................. 71 Face velocity – Step Size.................................................................................................. 71 Longitudinal pitch checkbox.............................................................................................. 72 Longitudinal pitch – Specified ........................................................................................... 72 Longitudinal pitch – Minimum ........................................................................................... 72 Longitudinal pitch – Maximum .......................................................................................... 72 Longitudinal pitch – Step Size........................................................................................... 72 Transverse pitch checkbox ............................................................................................... 73 Transverse pitch – Specified............................................................................................. 73 Transverse pitch – Minimum............................................................................................. 73 Transverse pitch – Maximum............................................................................................ 73 Transverse pitch – Step Size............................................................................................ 73 Tube length checkbox....................................................................................................... 74 Tube length – Specified .................................................................................................... 74 Tube length – Minimum .................................................................................................... 74 Tube length – Maximum ................................................................................................... 74 Tube length – Step Size.................................................................................................... 75 Tuberows checkbox .......................................................................................................... 75 Tuberows – Specified ....................................................................................................... 75 Tuberows – Minimum........................................................................................................ 75 Tuberows – Maximum....................................................................................................... 76 Tuberows – Step Size....................................................................................................... 76 Tube outside diameter checkbox...................................................................................... 76 Tube outside diameter – Specified ................................................................................... 76 Tube outside diameter – Minimum.................................................................................... 76 Page viii



Table of Contents

Tube outside diameter – Maximum................................................................................... 77 Tube outside diameter – Step Size................................................................................... 77 Design Mode Control – Classic......................................................................................... 77 Design Mode Control – Grid ............................................................................................. 77 Design Mode Control – Rating.......................................................................................... 78 Design Mode Control – Simulation ................................................................................... 78 Design Constraints panel ........................................................................................................ 78 Velocity – Minimum........................................................................................................... 79 Velocity - Maximum........................................................................................................... 79 Pressure drop allowed in inlet nozzles.............................................................................. 79 Pressure drop allowed in outlet nozzles ........................................................................... 79 Design Warnings panel ........................................................................................................... 80 Minimum tube wall temperature........................................................................................ 80 Maximum tube wall temperature....................................................................................... 80 Control input panel group............................................................................................................... 80 Case description...................................................................................................................... 81 Problem description................................................................................................................. 81 Flow Maldistribution panel....................................................................................................... 81 Diagram of Flow Maldistribution .................................................................................82 Maldistribution control.......................................................................................................82 Check any blocked sides .................................................................................................. 83 Diagram of Blocked Sides .......................................................................................... 84 Temperature Maldistribution panel.......................................................................................... 84 Methods panel ......................................................................................................................... 85 Outside friction factor method ........................................................................................... 85 Tubeside friction factor method......................................................................................... 85 Pure component condensation ......................................................................................... 85 Condensable components ................................................................................................ 86 Condensation method....................................................................................................... 86 Mole fraction noncondensables ........................................................................................ 88 Momentum recovery to include......................................................................................... 88 Pure component boiling .................................................................................................... 88 Check film boiling .............................................................................................................. 88 Boiling method .................................................................................................................. 89 Boiling method components.............................................................................................. 90 Surface correction factor................................................................................................... 90 Air-cooler single increment ............................................................................................... 91 Force phase separation in tube headers .......................................................................... 91 © Heat Transfer Research, Inc. All rights reserved. Confidential: For HTRI member use only.

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Table of Contents


High fin tube heat transfer method.................................................................................... 91 High fin tube pressure drop method.................................................................................. 92 HTRI Research Geometry.......................................................................................... 92 Safety panel............................................................................................................................. 93 Hot sensible liquid coefficient............................................................................................ 94 Hot sensible vapor coefficient ........................................................................................... 94 Condensing coefficient...................................................................................................... 95 Cold sensible liquid coefficient.......................................................................................... 95 Cold sensible vapor coefficient ......................................................................................... 95 Boiling coefficient .............................................................................................................. 95 Critical heat flux................................................................................................................. 96 Fraction of critical flux for film boiling ................................................................................ 97 Hot fluid coefficient multiplier ............................................................................................97 Cold fluid coefficient multiplier .......................................................................................... 97 Outside friction factor multiplier......................................................................................... 98 Tubeside friction factor multiplier ...................................................................................... 98 User-Defined Methods panel................................................................................................... 98 Reference pressure for nucleate boiling curve ................................................................. 98 Constant A for nucleate boiling curve............................................................................... 99 Exponent B for nucleate boiling curve .............................................................................. 99 Add non-nucleate boiling components to this curve ......................................................... 99 Constant A for film boiling curve .......................................................................................100 Exponent B for film boiling curve ......................................................................................100 Convergence panel .................................................................................................................101 Overall pressure drop .......................................................................................................101 Overall heat transfer..........................................................................................................101 Unknown duty ...................................................................................................................101 Local wall temperature......................................................................................................102 CAPE-OPEN panel..................................................................................................................102 Maximum number of pressure-properties trials ................................................................ 102 Relative pressure tolerance ..............................................................................................103 Absolute pressure tolerance .............................................................................................103 Absolute temperature tolerance........................................................................................103 Default number of pressure sets.......................................................................................104 Default number of pressure sets.......................................................................................104 Default number of pressure sets.......................................................................................105 X ace Output Reports................................................................................................................................... 106 Report Heading Example...............................................................................................................106 Page x



Table of Contents

Output Report Line 4 ...............................................................................................................107 Output Summary................................................................................................................................... 107 Process Conditions ........................................................................................................................ 108 Exchanger Performance ................................................................................................................ 108 Unit Geometry ................................................................................................................................109 Tube Geometry .............................................................................................................................. 110 Fan Geometry ................................................................................................................................ 110 Fin Geometry .................................................................................................................................111 Airside Velocities............................................................................................................................111 Thermal Resistance ....................................................................................................................... 112 Airside Pressure Drop....................................................................................................................112 Output Summary for Multiple Services.................................................................................................113 Overall Exchanger Performance....................................................................................................115 Outside Process Conditions...........................................................................................................115 Unit Geometry ................................................................................................................................115 Fan Geometry ................................................................................................................................ 116 Maximum Airside Velocities ........................................................................................................... 116 Airside Pressure Drop %................................................................................................................116 Exchanger

Weights........................................................................................................................117

Fan Manufacturers ......................................................................................................................... 117 Bundle Summary............................................................................................................................ 118 Run Log ................................................................................................................................................ 118 Data Check Messages ......................................................................................................................... 118 Runtime Final

Messages...............................................................................................................................119

Results.........................................................................................................................................120

Process Data..................................................................................................................................122 Average Coefficients......................................................................................................................123 Overall Performance Data ............................................................................................................. 125 Messages.......................................................................................................................................125 Unit and Bundle Construction Information .....................................................................................125 Tube Information ............................................................................................................................ 127 Inlet Airside Velocities....................................................................................................................128 Fan Description and Fan Power ....................................................................................................128 Two-Phase Parameters ................................................................................................................. 129 Heat Transfer and Pressure Drop Parameters .............................................................................. 129 Thermal Resistance ....................................................................................................................... 131 Airside Pressure Drop....................................................................................................................131 Tube Nozzle ...................................................................................................................................131 © Heat Transfer Research, Inc. All rights reserved. Confidential: For HTRI member use only.

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Table of Contents


Mean Metal Temperatures.............................................................................................................132 Graphical Bundle Layout................................................................................................................132 Bundle Information ......................................................................................................................... 132 Outside Monitor .................................................................................................................................... 132 Tubeside

Monitor..................................................................................................................................134

Explanation of Items on Outside/Tubeside Incremental Monitors ................................................. 134 Temperature Monitor ............................................................................................................................137 Pressure Drop Monitor .........................................................................................................................137 API 661 Spec Sheet .............................................................................................................................139 Property Monitor ................................................................................................................................... 140 Heat Release Profile ...................................................................................................................... 141 Vapor Properties ............................................................................................................................ 141 Liquid Properties ............................................................................................................................141 Miscellaneous Physical Property Factors ......................................................................................141 Vapor Mole Fraction.......................................................................................................................141 Liquid Mole Fraction....................................................................................................................... 142 Stream Properties................................................................................................................................. 142 Maldistribution Monitor ......................................................................................................................... 143 Input Reprint ......................................................................................................................................... 144 X ace Test Cases......................................................................................................................................... 146 X ace Test Case 1 .................................................................................................................................147 X ace Test Case 1 Results .................................................................................................................... 148 X ace Test Case 1 Output ..................................................................................................................... 149 X ace Test Case 2 .................................................................................................................................150 X ace Test Case 2 Results .................................................................................................................... 151 X ace Test Case 2 Output ..................................................................................................................... 152 X ace Test Case 3 .................................................................................................................................153 X ace Test Case 3 Results .................................................................................................................... 154 X ace Test Case 3 Output ..................................................................................................................... 155 X ace Test Case 4 .................................................................................................................................156 X ace Test Case 4 Results .................................................................................................................... 157 X ace Test Case 4 Output ..................................................................................................................... 158 X ace Test Case 5 .................................................................................................................................159 X ace Test Case 5 Results .................................................................................................................... 160 X ace Test Case 5 Output ..................................................................................................................... 161 X ace Frequently Asked Questions.............................................................................................................. 162 X ace About This Version............................................................................................................................. 166 Boiling Methods .................................................................................................................................... 167 Page xii



Table of Contents

Version 5.0 ..................................................................................................................................... 167 Version 3.0 Service Pack 2............................................................................................................167 Version 3.0 ..................................................................................................................................... 167 Version 2.0 ..................................................................................................................................... 168 Calculation Procedures ........................................................................................................................170 Version 5.0 ..................................................................................................................................... 170 Version 4.0 Service Pack 3............................................................................................................171 Version 4.0 Service Pack 1............................................................................................................171 Version 4.0 ..................................................................................................................................... 172 Version 3.0 Service Pack 2............................................................................................................173 Version 3.0 Service Pack 1............................................................................................................173 Version 3.0 [back to top] ................................................................................................................ 174 Version 2.0 Service Pack 2............................................................................................................175 Version 2.0 Service Pack 1............................................................................................................176 Version 2.0 ..................................................................................................................................... 176 Condensing Methods............................................................................................................................178 Version 5.0 ..................................................................................................................................... 178 Version 4.0 ..................................................................................................................................... 178 Version 3.0 ..................................................................................................................................... 178 Version 2.0 Service Pack 1............................................................................................................179 Version 2.0 ..................................................................................................................................... 179 Data Input and Data Check .................................................................................................................. 181 Version 5.0 ..................................................................................................................................... 181 Version 4.0 Service Pack 3............................................................................................................181 Version 4.0 Service Pack 1............................................................................................................182 Version 4.0 ..................................................................................................................................... 182 Version 3.0 ..................................................................................................................................... 182 Version 2.0 Service Pack 1............................................................................................................182 Version 2.0 ..................................................................................................................................... 182 Graphical Interface ............................................................................................................................... 184 Version 5.0 ..................................................................................................................................... 184 Version 4.0 Service Pack 3............................................................................................................185 Version 4.0 ..................................................................................................................................... 185 Version 3.0 Service Pack 2............................................................................................................186 Version 3.0 Service Pack 1............................................................................................................186 Version 3.0 ..................................................................................................................................... 186 Version 2.0 Service Pack 1 .................................................................................................................. 187 Version 2.0............................................................................................................................................ 187 © Heat Transfer Research, Inc. All rights reserved. Confidential: For HTRI member use only.

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Miscellaneous.......................................................................................................................................189 Version 5.0 ..................................................................................................................................... 189 Version 4.0 Service Pack 3............................................................................................................189 Version 4.0 Service Pack 2............................................................................................................189 Version 4.0 Service Pack 1............................................................................................................189 Version 4.0 ..................................................................................................................................... 189 Version 3.0 ..................................................................................................................................... 189 Version 2.0 Service Pack 2............................................................................................................190 Version 2.0 Service Pack 1............................................................................................................190 Version 2.0 ..................................................................................................................................... 190 Physical

Properties...............................................................................................................................193

Version 2.0 ..................................................................................................................................... 193 Program Outputs .................................................................................................................................. 195 Version 5.0 ..................................................................................................................................... 195 Version 4.0 Service Pack 3............................................................................................................196 Version 4.0 Service Pack 1............................................................................................................196 Version 4.0 ..................................................................................................................................... 196 Version 3.0 Service Pack 2............................................................................................................198 Version 3.0 Service Pack 1............................................................................................................199 Version 3.0 ..................................................................................................................................... 199 Version 2.0 Service Pack 2............................................................................................................202 Version 2.0 Service Pack 1............................................................................................................203 Version 2.0 ..................................................................................................................................... 204 Single-Phase Methods .........................................................................................................................207 Version 5.0 ..................................................................................................................................... 207 Version 3.0 ..................................................................................................................................... 207 Version 2.0 ..................................................................................................................................... 207 Glossary ......................................................................................................................................................210 Index............................................................................................................................................................ 213

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X ace Online Help, printed version Xace Overview X ace, HTRI’s fully incremental software for designing, rating, and simulating air coolers and economizers, takes advantage of our proprietary research for its methods and calculations. Input Panels Output Reports Test Cases FAQs About This Version


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Input Panels

Input Panels The following parts designate input panels with accompanying items. Input Summary panel Geometry input panel group Unit panel Fans panel Optional panel Bundle panel Bundle Layout panel Natural Draft panel Tube Types Tubes page f- and j-Curves page High Fins page Low Fins page Stud Fins page Twisted Tape page Micro-fin page Process input panel Design input panel group Design Geometry Design Constraints panel Design Warnings panel Control input panel group Name panel Flow Maldistribution panel Temperature Maldistribution panel Methods panel Safety panel User-Defined Methods panel Convergence panel CAPE-OPEN panel


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Input Panels


Input Summary panel Fields on this panel provide a summary of entire input. Default values appear in fields that have defaults; red-outlined fields require input. Any values you enter on this panel also appear on subordinate data panels.

Case Mode Sets type of case to be run. Rating

For geometrically specified exchangers, a Rating case requires sufficient process information to determine exchanger duty: number of tubepasses, number of rows, bundle width, tube length, pitch, layout angle, tube diameter, and tube wall thickness.

Simulation

Rating and Simulation differ only in amount of process information supplied. A Simulation (unknown duty case) has fewer process information requirements. In a simulation, X ace calculates expected performance of exchanger. The final result of a simulation is maximum heat duty that can be achieved in unit.

Classic Design

X ace designs the smallest exchanger with minimum number of bays in parallel that fulfills given geometrical, process, and physical property constraints. Process constraints must include heat duty (either specified or implicit) and can include pressure drop and/or velocity restraints. The minimum exchanger geometries necessary are tube length, pitch, layout type, tube diameter, and tube wall thickness.

Grid Design

The grid design gives you more control over design process because you specify a range of critical parameters for X ace to investigate in the design. For example, you can specify a minimum and maximum number of rows to be investigated during the design. After design is completed, X ace selects smallest exchanger that meets process constraints requirements.

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Input Panels

Required: No Units:

None

Default:

Rating

Geometry input panel group Use Geometry panels to define all air-cooler exchanger geometry. Icons in the tree to the left of this panel display particular geometry panels.

Unit panel Fields on this panel define your bay unit geometry and size, number, and types of tubeside nozzles.


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Input Panels


Unit type Sets type of unit for your exchanger.

Choices Air-Cooled Heat Exchanger Natural Draft Air-Cooler

This option is same as Air-cooler with fans off

Economizer

Hot side can be inside or outside tubes

X ace automatically considers that enhancement of heat transfer arises from radiation effects using the two-gray-gas model from HTRI’s FH software. At elevated temperatures, these effects can be extremely important. Required:

Yes

Units:

None

Default:

Air-Cooled Heat Exchanger

Traditionally, an economizer is a rectangular bundle of tubes that typically is placed in a hot gas stream. This gas heats the material flowing inside the tubes. Also typically, tubes are plain, stud-finned, or serrated finned. Some applications mix bare tubes in the first few rows with finned tubes further down in the bundle. You can include up to sixty rows of tubes in the bundle, although most applications have fewer tube rows. X ace defines economizers more broadly. In addition to an economizer as described above, X ace does not limit placement of the hot gas stream, which can be inside or outside the tubes. In addition, the hot fluid is not restricted to a single-phase gas; it can be a liquid or a condensing vapor. The only restriction is that condensing and boiling are not permitted on the outside of high-finned and stud-finned tubes. If you have an air-cooled vaporizer, for example, a propane vaporizer, you can use the economizer option to calculate the unit’s performance. Simply enter your case as an economizer, but also enter fan information. X ace calculates the expected performance of the unit, including fan power requirements. The natural draft option has been validated using research data from two different high-finned tube geometries. Both used common air-cooler tubes. Number of Fins

Fin Thickness Fin Height

Root Diameter

Pitch

Tubes per Row

Number of Rows

354.3/m

0.4318 mm 15.24 mm

25.4 mm

63.5 mm

30

4

433/m

0.4064 mm 15.875 mm

25.4 mm

58.4 mm

40

4

For a wide range of operating conditions, duty achieved without fans ranged from 5 to 30 percent of duty with fans running. Use caution when requesting natural draft (fans-off) calculation for units with different tubes and/or different overall geometries. The method that X ace uses, as well as a comparison of prediction of program with available research data, is given in HTRI Report AC-9.

Page 6



Input Panels

Fan arrangement Defines arrangement of fans in exchanger. Forced

fan below unit

Induced

fan above unit

X ace does not use maximum permitted sound power level in internal calculations. The value is used only by manufacturer’s design software. Required:

No

Units:

None

Default:

Forced draft

Diagram of Fan Arrangements

Forced Draft

Induced Draft Hot fluid location Designates hot fluid as being inside tubes or outside tubes (shell side). © Heat Transfer Research, Inc. All rights reserved. Confidential: For HTRI member use only.

Page 7

Input Panels


This field is available only for economizers. Required:

No

Units:

None

Default:

Outside tubes

When you change fluid allocation, you need not change any other parameters. Process conditions, physical properties, and other properties automatically switch.

Tube orientation Specifies orientation of tubes in bundles. Horizontal Vertical (top inlet) Vertical (bottom inlet) Inclined If you choose Inclined, specify inclination angle (1-89 degrees) or slope of tubes (mm/m or in./ft) based on your selection. Required:

Yes

Units:

degrees

Default:

Horizontal

Inclined bundles are permitted only for tubeside condensation. Correlations are based on data obtained on horizontal tubes, vertical tubes, and tubes inclined up to twenty degrees from horizontal.

Flow type Sets first tubepass in cocurrent or countercurrent flow. Cocurrent

first tubepass at bottom of bundle

Countercurrent

first tubepass at top of bundle

Required:

Yes

Units:

None

Default:

Countercurrent

X ace always assumes outside flow enters exchanger from bottom of bundle.

Page 8



Input Panels

Diagram of Cocurrent Flow

Diagram of Countercurrent Flow

Number of bays in parallel per unit Sets number of bays in parallel. X ace allows from 1 to 99 bays in parallel per unit. A bay is a unit that is 1 fan wide. If you enter multiple fans, X ace assumes they are to be placed along length of tubes. Required:

Yes

Units:

None

Default:

1

For Design cases, X ace treats value you enter as a minimum value that can be increased depending on mean temperature difference, pressure drop, and heat transfer requirements. For Rating cases, X ace uses value as specified.

Number of bundles in parallel per bay Sets number of identical bundles in parallel. A bay is a unit that is 1 fan wide. If you enter multiple fans, X ace assumes they are to be placed along length of tubes. Required:

Yes © Heat Transfer Research, Inc. All rights reserved. Confidential: For HTRI member use only.

Page 9

Input Panels


Units:

None

Default:

1

You can specify one or more bundles in parallel in a bay. For Design cases, X ace uses the number for all bays that you specify.

Number of services Indicates that all bundles in parallel share a common outside stream and common fans, fan rings, hail screens, fan guards, and louvers. Required:

No

Units:

None

Default:

1 (one)

When you run a case with more than one bundle, multiple services is an option. The Multiple Services view displays, showing the status of the calculations as they are performed. By default, X ace runs a series of identical exchangers with different tubeside process streams.

Number of tubepasses per bundle Specifies number of tubepasses in exchanger bundle. The maximum number of tubepasses that X ace allows is 1440. Required:

Yes

Units:

None

Default:

0

For Design cases, this item is usually omitted. If specified, X ace treats value you enter as the only value permitted while designing exchanger.

Nozzle database Sets the database for X ace to use for your exchanger. X ace supports multiple standards for pipe sizes through the use of nozzle data files. When you select a nozzle database file and schedule, you can use any piping standard. Required:

No

Units:

None

Default:

ANSI B36.01 Schedule 40 pipe

You can easily add other piping standards to HTRI X changer Suite.

Schedule Sets the schedule for X ace to use.

Page 10



Input Panels

Some nozzle size data files support the concept of schedule. For example, both ANSI B36.10 and B36.19 have nozzle diameters based on the schedule. When you select the schedule, X ace builds a customized list of nozzle diameters for HTRI X changer Suite to use. Required:

No

Units:

None

Default:

Depends on Nozzle database selected

If the nozzle data file you select does not contain multiple schedules, the selection for Schedule remains blank. You can easily add other piping standards to HTRI X changer Suite.

Entry type/ Exit type Specifies type of tubeside nozzles. Perpendicular Axial with distributor Axial Required:

No

Units:

None

Default:

Perpendicular

X ace assumes that outlet nozzle exit type is the same as inlet type.

Diagram of Tubeside Nozzle Types

Perpendicular

Axial

Axial with inlet distributor

Tubeside nozzle inside diameter :Inlet Specifies nozzle inside diameter for tubeside inlet nozzles. Required:

No

Units:

SI: mm

Default:

Program-calculated

US: in.

MKH: mm

Tubeside nozzle inside diameter :Outlet Specifies nozzle inside diameter for tubeside outlet nozzles. Required:

No

Units:

SI: mm

Default:

Program-calculated

US: in.

MKH: mm


Page 11

Input Panels


Number of nozzles per bundle: Inlet Specifies number of inlet nozzles on inlet header for one bundle. Required:

No

Units:

None

Default:

1 (one) nozzle

X ace assumes that all bundles have same number of nozzles.

Number of nozzles per bundle: Outlet Specifies number of outlet nozzles on outlet header for one bundle. Required:

No

Units:

None

Default:

1 (one) nozzle

X ace assumes that all bundles have same number of nozzles. The nozzle design procedure depends on whether you input nozzle diameter , number of nozzles, or both. If you specify nozzle diameter , but omit number of nozzles

X ace assumes one nozzle and adds nozzles until pressure drop is less than allowed nozzle pressure drop. The limit for number of nozzles is 20.

If you specify number of nozzles but not nozzle diameter

X ace starts with a nozzle diameter based on velocity criteria (see V max ) and increases diameter in nominal increments until diameter is just less than header depth. If pressure drop or velocity is higher than allowable, X ace adds additional nozzles and repeats the calculation.

If you specify neither number of nozzles nor diameter and –

specify total allowable pressure drop

X ace starts with nozzle diameter based on velocity criteria (see V max ) and increases diameter in nominal increments until it is just less than header depth. If pressure drop is still higher than the allowable, X ace adds more nozzles and repeats calculations.

–

do not specify total allowable pressure drop

X ace starts with nozzle diameter based on velocity criteria (see V max ) and increases in nominal increments until it is just less than the header depth. If nozzle velocity is higher than allowable, X ace adds more nozzles and repeats the calculation.

Nozzle pressure drop design limits If you specify total allowable pressure drop, the default maximum nozzle pressure loss is 10% of the total allowable pressure drop. You can enter a value other than the 10% by expanding the Design panel group and selecting Design Constraints panel. Page 12



Input Panels

Nozzle velocity design criteria The maximum (V max ) velocity permitted in the nozzle during design is based on fluid condition. V max for liquid

=

3.05 m/s (10 ft/s)

V max for gas

=

0.2 * (Acoustic Velocity)

=

0.2 * 20.13 (Nozzle inlet pressure in psia/density in lb/ft³)^0.5 ft/sec

=

0.2 * 0.296 * (Nozzle inlet pressure in Pa/density in kg/m³)^0.5 m/sec

If no nozzle diameter is specified, X ace sets starting nozzle diameter so that velocity in the nozzle is less than V max .

Fans panel Fields on this panel define parameters specific to fans. This panel is not required for economizers and can be omitted. If you do not enter information on this panel, X ace performs no fan calculations. It is possible to rate an air-cooled heat exchanger without specifying any fans. X ace calculates fan performance for economizers if you enter values for fan diameter and number of fans.

Number of fans per bay Sets number of fans per bay. This number is 0 (zero) for economizers. Required:

No

Units:

None © Heat Transfer Research, Inc. All rights reserved. Confidential: For HTRI member use only.

Page 13

Input Panels

Default:


2 (0 (zero) for economizers)

Fan diameter Specifies diameter of fan. Required:

No

Units:

SI: m

Default:

40% of bundle covered by fan blade

US: ft

MKH: mm

Radial fan tip clearance Sets radial fan tip clearance. X ace uses this field in fan pressure drop calculations. Required:

No

Units:

SI: mm

Default:

Value based on API standards

US: in.

MKH: mm

Total combined fan and drive efficiency Sets total combined fan and drive efficiency. X ace uses this value to calculate motor power requirements. Required:

No

Units:

percent

Default:

65%

Fan manufacturer Specifies fan manufacturer’s software. This software is called for air-cooled heat exchangers and economizers with fans and air on the outside (pressure range of 8 – 15 psia), not for economizer bundles or natural draft exchangers. Each fan manufacturer also offers fan design software as a stand-alone package. X ace uses fan software supplied by manufacturers; HTRI has not modified it. Unspecified Hudson Howden Moore COFIMCO All Required:

No

Units:

None

Default:

Unspecified

X ace interfaces with fan selection software supplied by several fan manufacturers. If you request, X ace calls the fan selection software after rating and prints out suggested fans for the exchanger based on manufacturers’ recommendations. The manufacturers’ code uses the following information from X ace: the Page 14



Input Panels

fan diameter, X ace-calculated air inlet to the fan’s density, required airside volume, forced or induced draft, inlet fan ring type, and inlet temperatures. Hudson Products Corporation Hudson software searches its fan data bank and recommends all fans that meet specifications. If no fan exactly matches requirements, the closest fan is recommended Howden Cooling Fans Howden’s fan selection software returns two recommended fans: the first fan is the optimal solution based on Howden's criteria; the second fan is the quietest for this application. The Moore Company Moore software searches its fan data bank and recommends all fans that meet specifications. COFIMCO S.p.A. COFIMCO S.p.A. software searches the fan data bank and recommends all fans that meet specifications. The fans are listed in order of lowest to highest price.

Maximum sound pressure level Sets maximum permitted sound pressure level. Any entered value passes to manufacturer’s fan selection software. If possible, fan selection software recommends a fan that does not exceed specified level. Required:

No

Units:

dBA at standard distance of 1 m

Default:

No noise limit

Number of fan shaft lanes per bundle Specifies number of fan lanes across the bundle. If you enter a value in this field, you must also enter Fan shaft lane width; otherwise, X ace adds no fan lanes to the bundle. Required:

No

Units:

None

Default:

No fan lane

In induced draft units, a fan shaft lane is required when the motor is located below the bundle. You must specify one or more lanes. X ace makes the following assumptions: 1.

The lanes are distributed evenly across the bundle. If there is one fan lane, it is located in the center.

2.

All fan lanes are blocked; no air flow goes through the lane.

3. X ace assumes no clearance between the tube and the fan lane, which is exactly the value you enter. With a constant number of tubes in the rows, the presence of a fan lane decreases the face velocity slightly at a constant mass flow rate because the bundle is wider by the specified fan lane width.

Fan shaft lane width Specifies width of fan lane. X ace assumes a zero clearance from the fan lane to the adjacent tubes. Required:

If fan lane is specified © Heat Transfer Research, Inc. All rights reserved. Confidential: For HTRI member use only.

Page 15

Input Panels


Units:

SI: mm

Default:

None

US: in.

MKH: mm

If you enter this item, you must also enter Number of fan lanes; otherwise, X ace adds no fan lanes to the bundle. X ace assumes a zero clearance from the fan lane to the adjacent tubes.

Fan ring type Specifies fan ring type for air-cooler exchanger. Straight Flanged 15-degree cone 30-degree cone Bell-shaped Required:

No

Units:

None

Default:

Straight

Straight fan ring has highest pressure drop; Bell-shaped fan ring has lowest pressure drop.

Diagram of Fan Ring Types

Straight

Flange

30-degree cone

Page 16


15-degree cone

Bell


Input Panels

Optional panel Fields on this panel define miscellaneous geometry parameters. Use items on this panel to specify additional optional geometry details for air-cooled heat exchangers. Consult online help for each field to determine if you should enter a value. No fields on this panel are required input.

Steam coil present Specifies presence or absence of a steam coil. X ace assumes that the steam coil contains one row of high-finned tubes placed on a pitch equal to twice the pitch of the bottom row of exchanger tubes have a 25.4-mm (1-in.) root diameter with 433 fins/m (11 fins/in.) aluminum fins 15.748-mm (0.62-in.) high number of tubes is based on bundle width X ace calculates additional airside pressure drop due to steam coil. It does not calculate any change in air inlet temperature due to presence of coil.

Fan area blockage Specifies fan area blockage by motor and other items. Required:

No

Units:

percent

Default:

None

X ace calculates additional airside pressure drop duty to specified blockage.


Page 17

Input Panels


Free area in hail screen Specifies percent of free area in hail screen. Required:

No

Units:

percent

Default:

No hail screen present

X ace calculates additional airside pressure drop due to hail screen.

Free area in fan guard Specifies percent of free area in fan guard. Required:

No

Units:

percent

Default:

No fan guard present

X ace calculates additional pressure drop due to fan guard.

Louvers present Specifies presence/absence of a louver. Required:

No

Units:

None

Default:

No

Louvers increase airside pressure loss slightly. X ace uses several items in calculating additional airside pressure drop based on construction elements of the heat exchanger: steam coil, fan area blockage, hail screen, ground clearance, and louvers code. Auxiliary pressure drops appear on the Final Results report.

Relative humidity Defines relative humidity of inlet air. Required:

No

Units:

percent

Default:

Relative humidity

If you omit a value in this field, X ace assumes that inlet air has a moisture content of zero. If you enter a value in this field, the fields Wet bulb temperature and Dew point temperature are unavailable for input.

Wet bulb temperature Defines wet bulb temperature. Required:

No

Units:

SI: °C

Page 18

US: °F

MKH: °C



Default:

Input Panels

Relative humidity

If you omit a value in this field, X ace assumes that inlet air has a moisture content of zero. If you enter a value in this field, the fields Relative humidity and Dew point temperature are unavailable for input.

Dew point temperature Defines dew point temperature. Required:

No

Units:

SI: °C

Default:

Relative humidity

US: °F

MKH: °C

If you omit a value in this field, X ace assumes that inlet air has a moisture content of zero. If you enter a value in this field, the fields Relative humidity and Wet bulb temperature are unavailable for input.

Maximum ambient temperature Sets maximum normal operating temperature. Required:

No

Units:

SI: °C

Default:

None

US: °F

MKH: °C

Currently, X ace uses this value only for printouts, not for calculations.

Minimum ambient temperature Sets minimum normal operating temperature. Required:

No

Units:

SI: °C

Default:

None

US: °F

MKH: °C

X ace uses this value to calculate fan power under cold-weather operating conditions, when air is typically denser.

Header box depth Sets depth of header box. Required:

No

Units:

SI: mm

Default:

101.6 mm (4 in.)

US: in.

MKH: mm

Diagram of Air-Cooled Exchanger Dimensions


Page 19

Input Panels


Forced Draft Model

Header box plate thickness Sets thickness of header box. Required:

No

Units:

SI: mm

Default:

101.6 mm (4 in.)

US: in.

MKH: mm

If you omit this value, X ace estimates value based on fluid pressure.

Header box height Sets height of header box. Required:

No

Units:

SI: mm

Default:

None

US: in.

MKH: mm

If you omit this value, X ace assumes that the header box is as high as the tube bundle.

Header box width Sets width of header box. Page 20



Required:

No

Units:

SI: mm

Default:

None

Input Panels

US: in.

MKH: mm

If you omit this value, X ace assumes that the header box is as wide as tube bundle.

Total tubesheet thickness Specifies total thickness of front and rear tubesheets in exchanger. Required:

No

Units:

SI: mm

Default:

Program-calculated

US: in.

MKH: mm

Number of intermediate tube supports Specifies intermediate tube supports in exchanger. When you select User Set, you can also select the number of supports. None Program Set User Set Required:

No

Units:

None

Default:

None

X ace decreases the heat transfer area slightly due to the presence of intermediate tube supports.

Width of intermediate tube supports Specifies size of intermediate tube supports. Required:

No

Units:

SI: mm

Default:

None

US: in.

MKH: mm

Design pressure Enter gauge pressure. If you omit this value, X ace uses the larger of fluid inlet pressure and 1034 kPa gauge (150 psig). Required:

No

Units:

SI: kPa

Default:

Larger of fluid inlet pressure and 1034 kPa gauge (150 psig)

US: psig

MKH: kg/cm² A


Page 21

Input Panels


Design temperature Specifies design temperature. If you enter a value, X ace prints it on appropriate printouts. Required:

For airside fluid

Units:

SI: mm

Default:

None

US: in.

MKH: mm

Plenum chamber type Specifies plenum chamber type in exchanger. Box Tapered Required:

No

Units:

None

Default:

Box

X ace prints this value on appropriate printouts to indicate type of plenum chamber. Plenum type is used only in natural draft calculations.

Ground clearance to fan blade Specifies ground clearance for fan blade. For induced draft units, enter clearance from ground to tube bundle. Required:

No

Units:

SI: m

Default:

Ground clearance pressure drop effects not calculated

US: ft

MKH: mm

If fan is too near the ground, additional pressure drop occurs and fan requires additional power. X ace also uses ground clearance for natural draft calculation option and blockage maldistribution calculations.

Page 22



Input Panels

Diagram of Induced Draft Unit Ground Clearance

Diagram of Forced Draft Unit Ground Clearance


Page 23

Input Panels


Bundle panel Fields on this panel define bundle geometry of your heat exchanger. Enter Number of tube rows, Number of tubes in each odd/even numbered row, Bundle width, and Tube length; all other fields are optional.

Default bundle type Sets default layout for bundle. This field controls arrangement of tubepasses in bundle when you do not enter layout on Bundle Layout panel. For most bundles, this code sets up tubepasses to represent the exchanger correctly, making specification easier. Required:

No

Units:

None

Default:

Rows

Choices User-specified X ace uses layout given on Bundle Layout panel. If you enter no information on Bundle Layout panel, X ace treats bundle as if it has an equal number of tubes in each tubepass. Rows X ace sets up bundle using whole rows in each tubepass. If number of tubepasses is evenly divisible into number of tube rows, all tubepasses have same number of rows. Fewer tubepasses than rows: first tubepass must be set up with more rows than other passes Number of tubepasses evenly divisible into number of tube rows: all tubepasses have same number of rows Side-by-side X ace sets up bundle with all tubepasses side by side in bundle which can result in a non-standard layout that could not be manufactured. Modify the layout on the Bundle Layout panel, if necessary. Rows/Side-by-side X ace sets all rows except last to be in first tubepass. All other tubepasses are set up side by side in last (bottom) tube row. Equal count X ace sets up bundle so that number of tubes in each tubepass is approximately same.

Page 24



Input Panels

Diagram of Bundle Layout Choices

Number of tuberows Specifies number of tuberows in exchanger bundle. Required:

Yes (rating and simulation cases) No (design cases)

Units:

None

Default:

None (rating and simulation) Program-calculated (design)

X ace allows up to 60 tuberows. Using fewer than 4 rows is not good practice. © Heat Transfer Research, Inc. All rights reserved. Confidential: For HTRI member use only.

Page 25

Input Panels


Tubes in odd rows Specifies number of tubes in each odd-numbered row. If number is constant, enter same value for this item as for Number of tubes in each even-numbered row. Required:

Yes (not required for design case)

Units:

None

Default:

Program-calculated

Enter either this value or Bundle width. If you enter both values, X ace uses both values unless specified number of tubes does not fit in specified bundle width. In that case, X ace keeps number of tubes and recalculates bundle width.

Tubes in even rows Specifies number of tubes in each even-numbered row. If number is constant, enter same value for this item as for Number of tubes in each odd-numbered row. Required:

Yes (not required for design case)

Units:

None

Default:

Program-calculated

Enter either this value or Bundle width. If you enter both values, X ace uses both values unless specified number of tubes does not fit in specified bundle width. In that case, X ace keeps number of tubes and recalculates bundle width.

Diagram of Tubes in Odd/Even Rows

Page 26



Input Panels

Tube layout Specifies pattern of tube layout used in exchanger bundle: Staggered or inline. Required:

Yes

Units:

No

Default:

Staggered

Diagram of Tube Layouts

Tube form Specifies type of tube form: Straight or U-tube. Required:

Yes

Units:

None

Default:

Straight

Bundle width Specifies width of bundle in exchanger. The value is a distance between edges of bundle excluding any flanges. X ace uses this dimension as width of exchanger for face area calculations and for determining number of tubes by subtracting clearance specified to first tube from bundle width and dividing by tube pitch. Required:

Yes

Units:

SI: m

Default:

None

US: ft

MKH: mm


Page 27

Input Panels


If you enter this dimension, you can omit number of tubes in even- and odd-numbered rows. If you enter both this width and number of tubes in rows, number of tubes overrides bundle width if tubes do not fit into width entered.

Diagram of Bundle Width

Clearance, wall to first tube Specifies clearance from bundle wall to fin of first tube in top row of exchanger. X ace automatically adjusts clearance for other rows in staggered layouts. Required:

No

Units:

SI: mm

Default:

9.5 mm (0.375 in.)

US: in.

MKH: mm

Enter distance from bundle’s edge, not from flange to tube.

Side seals Specifies whether to bypass seals present in bundle. Required:

No

Units:

None

Default:

No

X ace corrects airflow velocity over tubes for presence of side seals. Seals usually increase airside pressure drop and heat transfer slightly.

Tube length Specifies total length of tubes in exchanger bundle. Required:

Yes

Units:

SI: m

Default:

No

US: ft

MKH: mm

Total unfinned tube length Specifies total unfinned tube length in exchanger. X ace uses this value in outside surface area calculations. Required:

No

Units:

SI: mm

Page 28

US: in.

MKH: mm



Default:

Input Panels

No

Additional unheated tube length Specifies additional unheated tube length in exchanger. This item excludes length inside tubesheet and length under tube supports (see Optional panel). Required:

No

Units:

SI: mm

Default:

Sum of tubesheet thickness plus length under any support strips

US: in.

MKH: mm

X ace uses this value in tubeside pressure drop calculations.

Equivalent tube length in tube bends for U-tubes Specifies equivalent length per tube. X ace uses this value in tubeside pressure drop calculations. Required:

No

Units:

SI: mm

Default:

Supplied by X ace, based on a long radius ell

US: in.

MKH: mm

Passes for Rows with Defined Passes Bundle Type Grid Specifies passes per row for Rows with Defined Passes bundle type. Pass combinations may not exceed 24 pass entries per row. Tubes in the row are equally divided into specified passes. Extra tubes are added one at a time to each pass (starting from the left) until all extra tubes are used. If you do not enter a row, X ace uses layout from the previous row. Layout for row one is not optional. Required:

Yes, for rows with defined layouts only

Units:

None

Default:

None

To activate the Defined Passes grid, you must select Rows with defined passes for the Default bundle type field.


Page 29

Input Panels


Tube Types panel This introductory panel allows you to choose tube types. Each tube type has different geometry and f-and j-curve input pages; high-finned, low-finned, stud-finned tubes and twisted tape inserts have further input pages.

Add button Adds a tube type to the list.

Delete button Deletes the highlighted tube from the list. To select a tube type, click the number in the first column.

Tube name Designates tube type plus number, i.e., TubeType1 is the first type of tube. Required:

Yes

Units:

None

Default:

TubeTypen where n is 1, 2, 3, 4, up to 9

Tube type Specifies type of tube used in exchanger bundle: Plain, low-finned, high-finned, or stud-finned (available only with economizers). Required:

No

Units:

None

Default:

Plain

If you specify other than Plain, you must furnish additional information on a subsequent panel.

Tube internals Defines geometry of tube internal devices (e.g., inserts): twisted tape micro-fin none Page 30



Required:

No

Units:

None

Default:

None

Input Panels

Tube Geometry page Fields on this page define tube geometry of your heat exchanger. Enter Tube OD, Wall thickness, and Transverse pitch; all other fields are optional. This page repeats for each tube type.

Tube material code Specifies material from which tube is made. Select from built-in list of materials. If you select , you must specify Tube thermal conductivity. Required:

No

Units:

None

Default:

Carbon steel

Tube thermal conductivity Specifies thermal conductivity of tube material. Use this field when your tube material is not in X ace's Tube Material Databank. Required:

No

Units:

SI: W/m °C

Default:

X ace uses the Tube Material Code in its thermal conductivity calculations and provides a default value unless you select Not in Databank.

US: Btu/hr ft °F

MKH: kcal/hr m °C


Page 31

Input Panels


Tube OD Specifies outside diameter of tubes. For low-finned tubes, this value is the plain end diameter. Required:

Yes

Units:

SI: mm

Default:

None

US: in.

MKH: mm

Wall thickness Specifies average wall thickness of tube directly or in terms of BWG (Birmingham Wire Gage) value. For low-finned tubes and tubes with imbedded fins, this value is the plain end wall thickness. Required:

Yes

Units:

SI: mm

Default:

None

US: in.

MKH: mm

The entered value must be less than half tube diameter. This value affects tubeside flow area. The button to right of this field displays a worksheet that allows you to specify wall thickness in terms of BWG.

BWG

mm

in.

10

3.4036

0.134

11

3.0480

0.120

12

2.7686

0.109

13

2.4130

0.095

14

2.1082

0.083

15

1.8288

0.072

16

1.6510

0.065

17

1.4732

0.058

18

1.2446

0.049

19

1.0668

0.042

20

0.8890

0.035

21

0.8128

0.032

22

0.7112

0.028

23

0.6350

0.025

24

0.5588

0.022

25

0.5080

0.020

Equilateral layout Forces equilateral tube pitch layout (longitudinal pitch = 0.866 * transverse pitch). Page 32



Input Panels

When the checkbox is selected, the program disables the longitudinal pitch entry and calculates the value from the transverse pitch. Required:

No

Units:

None

Default:

Unchecked

Transverse pitch Specifies transverse tube pitch. Required:

Yes

Units:

SI: mm

Default:

None

US: in.

MKH: mm

X ace automatically supplies transverse pitch for high-finned tubes selected from Automatic Tube Data Bank.

Longitudinal pitch Specifies longitudinal pitch. Longitudinal pitch is required for nonequilateral staggered and inline tube banks only. Enter zero (0) for equilateral staggered layouts. Required:

Yes

Units:

SI: mm

Default:

None

US: in.

MKH: mm

X ace automatically supplies longitudinal pitch for high-finned tubes selected from Automatic Tube Data Bank.


Page 33

Input Panels


Diagram of Tube Pitches

90°, Square

45°, Rotated Square

30°, Triangular

60°, Rotated Triangular

Page 34



Input Panels

Table of Tube Pitches Number of Fins

Wall Thickness

Fin Thickness

1/m

1/in.

mm

in.

mm

in.

mm

in.

mm

in.

BI

354.3

9.0

3.05

0.120

0.432

0.017

55.88

2.200

15.24

0.600

B2

354.3

9.0

3.05

0.120

0.432

0.017

55.88

2.200

15.24

0.600

B7

354.3

9.0

3.05

0.120

0.432

0.017

55.88

2.200

15.24

0.600

B8¹

354.3

9.0

3.05

0.120

0.432

0.017

55.88

2.200

15.24

0.600

B9

196.8

5.0

2.79

0.110

1.524

0.060

57.91

2.280

16.51

0.650

B10

315.0

8.0

3.30

0.130

0.432

0.017

50.80

2.000

12.70

0.500

B11

315.0

8.0

3.30

0.130

0.432

0.017

56.64

2.230

15.75

0.620

B12

437.0

11.1

2.67

0.105

0.406

0.016

50.80

2.000

12.70

0.500

B13

433.1

11.0

3.30

0.130

0.406

0.016

57.15

2.250

16.00

0.630

B16

433.1

11.0

1.90

0.075

0.432

0.017

56.64

2.230

15.75

0.620

B17

433.1

11.0

1.90

0.075

0.432

0.017

56.64

2.230

15.75

0.620

B18

433.1

11.0

1.90

0.075

0.432

0.017

56.64

2.230

15.75

0.620

B19

433.1

11.0

1.90

0.075

0.432

0.017

56.64

2.230

15.75

0.620

B20

433.1

11.0

1.90

0.075

0.432

0.017

56.64

2.230

15.75

0.620

B25

320.9

8.15

1.32

0.052

0.203

0.008

35.48

1.397

9.80

0.386

B27¹

433.1

11.0

2.13

0.084

0.305

0.012

56.92

2.241

15.77

0.621

B28

433.1

11.0

2.13

0.084

0.305

0.012

56.92

2.241

15.77

0.621

B29

433.1

11.0

2.13

0.084

0.305

0.012

56.92

2.241

15.77

0.621

B30

390.9

9.93

1.85

0.073

0.381

0.015

57.68

2271

15.41

0.607

B3I

389.8

9.9

1.84

0.073

0.381

0.015

57.28

2.255

15.06

0.593

C5

433.1

11.0

3.30

0.130

0.558

0.022

76.20

3.000

22.35

0.880

C8

275.6

7.0

3.43

0.135

1.270

0.050

63.25

2.490

12.70

0.500

C9

358.3

9.1

4.45

0.175

1.143

0.045

46.48

1.830

4.19

0.165

C10

417.3

10.6

3.56

0.140

0.457

0.018

100.08

3.940

30.73

1.210

C16

354.3

9.0

2.79

0.110

0.483

0.019

68.58

2.700

15.24

0.600

C17

354.3

9.0

2.79

0.110

0.483

0.019

68.58

2.700

15.24

0.600

C18

354.3

9.0

2.79

0.110

0.483

0.019

68.58

2.700

15.24

0.600

C19

370.1

9.4

2.92

0.115

0.356

0.014

69.85

2.750

15.75

0.620

C20

433.1

11.0

2.92

0.115

0.406

0.016

63.30

2.492

15.75

0.620

C21

354.3

9.0

2.65

0.105

0.635

0.025

70.05

2.758

15.98

0.629

D31

433.1

11.0

3.30

0.130

0.406

0.016

88.90

3.500

19.05

0.750

D32

346.5

8.8

2.54

0.100

0.610

0.024

101.85

4.010

24.13

0.950

D34

350.4

8.9

1.65

0.065

0.584

0.023

101.85

4.010

23.88

0.940

D35

350.4

8.9

1.65

0.065

0.584

0.023

101.85

4.010

23.88

0.940

D36

350.4

8.9

1.65

0.065

0.584

0.023

101.85

4.010

23.88

0.940

D41

350.4

8.9

1.65

0.065

0.584

0.023

101.85

4.010

23.88

0.940

F1

198.0

5.03

7.54

0.297

1.245

0.049

218.92

8.619

25.32

0.997

F2

198.0

5.03

7.54

0.297

1.245

0.049

218.92

8.619

25.32

0.997

Code

Over-fin Diameter

Fin Height

¹Equal velocity layout


Page 35

Input Panels


f- and j-Curves page Items on this page allow you to override internal heat transfer and pressure drop correlations. If you have more than one tube type in bundle, additional f- and j-curves pages appear for each tube type.

Outside f and j Factors The f- and j-factors are geometry-dependent. Take care to assure that values you enter are for tube and tube pattern specified.

Equation Forms The equation forms that X ace uses when you input outside f- and j-factors appear below:

j

ho Pr 2 3 C p G x

f

2g c 4G 2

h

P L D

where p C

Fluid heat capacity

g c

Gravitational constant

G x

Mass velocity

ho

Heat transfer coefficient

N rx

Number of tuberows crossed

P Pr

Pressure drop Prandtl number Fluid density Tube row correction factor

h

Page 36

Physical property correction factor © Heat Transfer Research, Inc. All rights reserved. Confidential: For HTRI member use only.


Input Panels

Tubeside f- and j-Factors When you enter tubeside f- and j-factors, X ace uses a Reynolds number based on plain inside diameter. Convert any values you enter to that basis.

Equation Forms The equation forms that X ace uses when you input tubeside f- and j-factors appear below:

ho Pr 2 3

j

C p G x

f

2g c 4G 2

h

P L D

where p C

Fluid heat capacity

D

Tube inside diameter

g c

Gravitational constant

G

Mass velocity

h

Heat transfer coefficient

k

Thermal conductivity

L

Length

Pr

Prandtl number

P

Pressure drop Fluid density Physical property correction factor

h

For more information on f- and j-factors, consult sections Single-Phase Pressure Drop and Single-Phase Heat Transfer in the Design Manual .

Outside/Airside f- and j-factors Overrides internal outside/airside heat transfer (j-factor) and pressure drop (f-factor) correlations. If you specify values, X ace calculates f- and/or j-factors using supplied values. Use this option to enter experimental data directly into program. Enter f- and j-factors in one of 2 ways: Specify values at 2 or 3 Reynolds numbers. OR Enter a and b constants as a function of Reynolds numbers. Required:

No

Units:

None

Default:

Use internal correlations

NOTE: This panel shows Outside for economizers and Airside for air-cooled heat exchangers.


Page 37

Input Panels


Tubeside f- and j-factors Overrides internal tubeside heat transfer (j-factor) and pressure drop (f-factor) correlations. If you specify values, X ace calculates f- and/or j-factors using your supplied values. Use this option to model some type of augmentation device or internal fins. Enter f- and j-factors in one of 2 ways: Specify values at 2 or 3 Reynolds numbers. OR Enter a and b constants as a function of Reynolds numbers. Required:

No

Units:

None

Default:

Use internal correlations

You can specify f-factors, j-factors, or both. If you specify only f-factor or j-factor, X ace calculates the other value from internal correlations.

Twisted Tape page Input items on this page define the geometry of twisted tapes. X ace supports twisted tapes for boiling, condensing, and single-phase fluids.

Twisted tape thickness Specifies thickness of a twisted tape insert. Required:

Yes (for twisted tape inserts)

Units:

SI: mm

Default:

None

US: in.

MKH: mm

To specify twisted tape inserts, you must enter values in this field, Length for 360-degree twist, and Twisted tape width..

L/D 360-degree twist Specifies longitudinal length for one complete rotation of twisted tapedivided by width of the tape (L/D). Required:


Units:

None

Default:

None

Page 38



Input Panels

To specify twisted tape inserts, you must enter values in this field, Twisted tape thickness, and Twisted tape width. Correlations are based on HTRI and industrial data for twisted tapes with an L/D from 8 through 16.

Twisted tape width Specifies the width of a twisted tape insert. Required:


Units:

SI: mm

Default:


US: in.

MKH: mm

To specify twisted tape inserts, you must enter values in this field, in Twisted tape thickness, and in Length for 360-degree twist.

Micro-fin page Use items on this page to define micro-fin geometry. This page appears only when you choose Highfinned on Tube Types panel. Currently, micro-fins are for single-phase fluids only. When you select micro-fins, X ace applies the EHT micro-fin multiplier on the same plain heat transfer and pressure drop methods used in EHT. Calculations done in X changer Suite are fully incremental and do use variable properties.

Diagram of Micro-fin Tube Insert

Di = inside diameter e = fin height t = fin thickness © Heat Transfer Research, Inc. All rights reserved. Confidential: For HTRI member use only.

Page 39

Input Panels


Number of fins Specifies the number of internal micro-fins. To specify micro-fin inserts, you must enter values in this field, Fin height, Fin thickness, and Fin helix angle. Required:

Yes (For micro-fin inserts)

Units:

None

Default:

None

Correlations are based on EHT micro-fin multiplier methods developed by Dr. John Thome. These multipliers are applied to the HTRI plain tube methods.

Fin height Specifies the height of internal micro-fins. To specify micro-fin inserts, you must enter values in this field, Number of fins, Fin thickness, and Fin helix angle. Required:


Units:

None

Default:

None


Fin thickness Specifies the thickness of internal micro-fins. To specify micro-fin inserts, you must enter values in this field, Number of fins, Fin height, and Fin helix angle. Required:


Units:

None

Default:

None


Tube inside diameter Specifies the inside diameter of the tube due to microfins. This value may be less than the plain tube inside diameter (due to wall thickness) if internal fins are extruded. If you do not specify this value, X ace used the calculated value using wall thickness and tube outside diameter. Required:


Units:

None

Default:

None


Page 40



Input Panels

Fin helix angle Specifies the helix angle for internal micro-fins. tan (helix angle) = p (tube I.D.)/[(axial fin pitch)(number of fins) Required:

No

Units:

None

Default:

None


Fin apex angle Specifies the apex angle for internal micro-fins. This value is used only for the portion of the internal microfins in the condensing region. Required:

No

Units:

None

Default:

None


High Fins page Use items on this page to define high-finned tube geometry. This page appears only when you choose High-finned on Tube Types panel.


Page 41

Input Panels


Load from Databank button Calls a dialog box to set fin geometry for high-finned tubes from X ace's internal databank, which contains actual fin dimensions from various tube manufacturers. Dialog Box, Fin Geometry for High-Finned Tubes

Unset Bank Fin button Clears the Bank fin code field. Each high-finned type in the databank file has a range of valid geometry parameters. You can set specific high-fin parameters outside prescribed limits in the databank by using the dialog box accessible from the Load from Databank button.

Bank fin code Sets fin geometric input for high-finned tubes from Xace's internal databank, which contains actual fin dimensions from various tube manufacturers. Select a databank type and tube dimensions. OR Enter all fin geometry values. You can override any values that X ace inserts as a result of your fin selection. Required:

No

Units:

None

Page 42



Default:

Input Panels

None

High Accuracy Automatic High-Finned Tube Geometry: If you enter an Automatic Tube Code for a highfinned tube, X ace supplies specific correlations based on HTRI research data. Bank Fin Codes

Code

Tube Description

105

I-foot high-finned tubes, 5 fins/in. (197 fin/m)*

108


109


110


111


205

L-foot high-finned tubes, 5 fins/in. (197 fin/m)*

208


209


210


211


*All tubes have aluminum fins 0.625-in. (15.875-mm) high and 0.017 in. (0.4318 mm) thick.

Fin type Sets relevant parameters that you can enter for a given fin type. Entries on panel are activated according to type of high fin you select here. Circular Serrated Rectangular and plate (continuous) Required:

Yes

Units:

None

Default:

Circular

Not all tube types are available in all tube materials. If you do not find the fin geometry you want, manually enter fin geometry values.


Page 43

Input Panels


Diagram of Circular Fin

Diagram of Serrated Fin

Diagrams of Rectangular and Plate (Continuous) Fin

Rectangular L-Foot

Page 44

Rectangular I-Foot



Input Panels

Continuous (Plate–fin) Sections Fin density Defines number of fins per unit length. The value you select for this field can have a significant effect on your exchanger’s performance. Required:

Yes

Units:

SI: fins/m

Default:

None

US: fins/in.

MKH: fins/m

If you select Auto code, X ace automatically supplies values for this field.

Fin base thickness Specifies fin base thickness. If fins have uniform thickness or if you know only average thickness, enter that value. Required:

No

Units:

SI: mm

Default:

None

US: in.

MKH: mm

Fin tip thickness Specifies fin tip thickness. If fins have uniform thickness or if you know only average thickness, enter that value. Required:

No

Units:

SI: mm

Default:

None

US: in.

MKH: mm

Fin material Specifies material from which fins are made. Select from a list of built-in materials, or specify fin material thermal conductivity. © Heat Transfer Research, Inc. All rights reserved. Confidential: For HTRI member use only.

Page 45

Input Panels


Required:

No

Units:

None

Default:

Aluminum 1060-H14

Fin material thermal conductivity Specifies thermal conductivity of fin material. Use this field when your tube material is not in X ace’s Fin Material Databank. Required:

No

Units:

SI: W/m °C

Default:

US: Btu/hr ft °F

MKH: kcal/hr m °C

X ace uses Fin Material Code in its thermal conductivity calculations and provides default value unless you select Not in Databank.

Fin bond resistance Specifies fin bond resistance. If you do not enter a value, X ace assumes no bond resistance. Required:

No

Units:

SI: m² K/W

Default:

None

Integral finned tubes

US: ft² hr °F/Btu

MKH: m² hr °C/kcal

These tubes have zero bond resistance.

Imbedded finned tubes These tubes have zero bond resistance. Tension-wound tubes

At elevated temperatures (typically above 176 °C (350 °F)), fin can separate from tube, resulting in marked decrease in heat transfer.

Bimetallic tubes

Any value you enter for fin bond resistance can be considered to be resistance between tube and sleeve. New bimetallic tubes have no bond resistance.

X ace adds entered value directly as resistance in overall heat transfer coefficient calculations. It is not added to calculated outside heat transfer coefficient and is not corrected for area ratio. Therefore, the value you enter must be based on extended surface area of tube and not actual bond area.

Fin efficiency Specifies fin efficiency. Usually you should not enter a value because X ace calculates it. However, if you input j-curves on f- and j-Curves panel and have already included efficiency in given j-factors, enter an efficiency of 100%. Required:

No

Units:

percent

Default:

None

Do not enter efficiency values as a fraction.

Page 46



Input Panels

Over-fin diameter Specifies over-fin diameter. Required:

No

Units:

SI: mm

Default:

None

US: in.

MKH: mm

Use this field for circular and segmented fins only. Diagram of Fin Measurements

Split segment height Specifies cut segment height. Required:

No

Units:

SI: mm

Default:

None

US: in.

MKH: mm

Enter 0 (zero) for non-serrated tubes. © Heat Transfer Research, Inc. All rights reserved. Confidential: For HTRI member use only.

Page 47

Input Panels


Split segment width Specifies split segment width. Required:

No

Units:

SI: mm

Default:

None

US: in.

MKH: mm

Enter 0 (zero) for non-serrated tubes.

Height of rectangular section Specifies length in direction of airflow. Required:

No

Units:

SI: mm

Default:

None

US: in.

MKH: mm

Rate continuous fin (plate-fin) units by specifying rectangular finned tubes with zero fin-tip clearance.

Width of rectangular section Specifies length perpendicular to airflow. Required:

No

Units:

SI: mm

Default:

None

US: in.

MKH: mm

Rate continuous fin (plate-fin) units by specifying rectangular finned tubes with zero fin-tip clearance.

Low Fins page Use items on this page to define low-finned tube geometry. This page appears only when you choose Low-finned on Tube Types panel. Either select a tube from the internal databank or enter low-finned tube geometry directly.

Load from Databank button Calls a dialog box to set fin geometry for low-finned tubes from X ace's internal databank, which contains actual fin dimensions from various tube manufacturers. Page 48



Input Panels

Load from Databank Dialog Box

Databank type Sets fin density and height for low-finned tubes from X ace's internal databank, which contains actual fin dimensions from various tube manufacturers. Select a databank type and tube dimensions OR Enter all fin geometry values. You can override any values that X ace inserts as a result of your selection. Required:

No

Units:

None

Default:

None

Not all tube types are available in all tube materials. If you do not find fin geometry you want, select Not in Databank and manually enter fin geometry values. When you select fin geometry in this field, you must also select an available tube size from Tube dimensions list. After you select a databank type, Tube dimensions list displays tube sizes for which that fin geometry is available. X ace automatically enters all geometry fields on panel when you select from Tube dimensions list. Select Not in Databank if you do not find fin geometry or tube dimension you want, and then manually enter fin geometry values in geometry fields on Fins panel. You can override individual geometry items after you select a databank type.

Tube dimensions Sets tube dimensions for low-finned tubes. After you select fin geometry from Databank type list, select tube OD, plain end wall thickness, and finned section wall thickness dimensions from list of valid tube sizes available for that fin geometry.


Page 49

Input Panels


X ace automatically inserts values in all geometry fields on Low Fins page. In addition, tube OD and plain end wall thickness override any value you entered on Tubes page. You can override individual geometry items after you select a databank type. Required:

If Databank type is selected

Units:

None

Default:

None

If you do not find fin geometry or tube dimension you want, select Not in Databank in Databank type and manually enter fin geometry values.

Fins per unit length Defines number of fins per unit length. The value you select for this field can have a significant effect on your exchanger’s performance. Required:

Yes

Units:

SI: fins/m

Default:

None

US: fins/in.

MKH: fins/m

If you select Databank type and Tube dimensions, X ace automatically supplies values for this field.

Fin root diameter Sets diameter of fin root, sum of Tube inside diameter and Wall thickness under fins. Required:

For low-finned tubes /high-finned tubes

Units:

SI: mm

Default:

None

US: in.

MKH: mm

If you select Databank type and Tube dimensions, X ace automatically supplies values for this field in Low Fins page. If you select Auto code, X ace automatically supplies values for this field in High Fins page.

Fin height Sets height of fin, measured from Fin root diameter to Overfin diameter. Required:

For low-finned tubes /high-finned tubes

Units:

SI: mm

Default:

None

US: in.

MKH: mm

If you select Databank type and Tube dimensions, X ace automatically supplies values for this field in Low Fins page. If you select Auto code, X ace automatically supplies values for this field in High Fins page.

Fin thickness Sets average thickness of fins. Required: Page 50

For low-finned tubes © Heat Transfer Research, Inc. All rights reserved. Confidential: For HTRI member use only.


Units:

SI: mm

Default:

None

Input Panels

US: in.

MKH: mm

If you select Databank type and Tube dimensions, X ace automatically supplies values for this field in Low Fins page.

Outside area/length Sets total outside finned surface area per unit length of tube. Required:

For low-finned tubes

Units:

SI: m²/m

Default:

None

US: ft²/ft

MKH: m²/m

If you select Databank type and Tube dimensions, X ace automatically supplies values for this field in Low Fins page.

Wall thickness under fins Sets wall thickness of tube under finned section. Required:

For low-finned tubes

Units:

SI: mm

Default:

None

US: in.

MKH: mm

If you select Databank type and Tube dimensions, X ace automatically supplies values for this field.

Stud Fins page Use items on this page to define stud-finned tube geometry. This page appears only when you design an economizer and choose Stud fin for Tube Type on Tube Types panel.

Number of stud rings Specifies number of stud rings per unit length of tube. © Heat Transfer Research, Inc. All rights reserved. Confidential: For HTRI member use only.

Page 51

Input Panels


Required:

For stud-finned tubes

Units:

SI: stud/m

Default:

None

US: stud/ft

MKH: stud/m

Typical Stud-Finned Tube Geometry

Typical Range Item

SI

Most Common Value

US

SI

US

Tube diameter

63.5 – 222 mm

2.5 – 8.75 in.

114.3 mm

4.5 in.

Stud diameter

6.35 – 12.7 mm

0.25 – 0.5 in.

12.7 mm

0.5 in.

Stud length

12.7 – 57.15 mm

0.5 – 2.25 in.

25.4 mm

1.0 in.

Fin material

Carbon steel, stainless

Carbon steel

Tube material

Carbon steel, stainless

Carbon steel

Number of studs in each ring Indicates number of studs per ring. Required:


Units:

None

Default:

None

Typical Maximum Stud Density

Tube Diameter

Maximum Studs per Row for Stud Diameters, mm (in.)

mm

in.

.0 (0.24)

0.0 (0.4)

12.0 (0.47)

12.5 (0.49)

219.0

8.625

51

38

34

32

168.3

6.625

39

29

26

24

141.3

5.563

33

25

22

20

114.3

4.5

26

20

18

16

101.6

4.0

23

16

16

15

88.9

3.5

22

14

14

12

73.0

2.875

17

12

11

10

60.3

2.375

14

10

9

8

50.8

2.0

12

8

7

7

Stud length Specifies length of studs welded to tube. Required: Page 52

For stud-finned tubes © Heat Transfer Research, Inc. All rights reserved. Confidential: For HTRI member use only.


Units:

SI: mm

Default:

None

Input Panels

US: in.

MKH: mm

Stud diameter Specifies diameter of stud. Required:


Units:

SI: mm

Default:

None

US: in.

MKH: mm

Bundle Layout panel Use items on this panel to set tubepass and tube type graphically for individual tubes or groups of tubes in bundle: select/deselect one or more tubes, change properties of selected tube(s), insert and delete rows from layout, and also display properties of selected tube(s). The figure below illustrates a typical bundle layout.

User defined tube pass layout Allows users to edit drawing directly. Required:

No

Units:

None

Default:

User defined drawing unchecked

If you right-click a tube or a row in the drawing and change the property of the tube or row, X ace selects User defined drawing, and other information at the top of the panel is not available for input. When you check this option, you can edit the drawing, which becomes the layout that X ace uses. The fields Number of tuberows/tubepasses, Number of tubes in each odd/even row, and Clearance, wall to first tube become unavailable for input. The only way to specify these items is by changing the drawing. © Heat Transfer Research, Inc. All rights reserved. Confidential: For HTRI member use only.

Page 53

Input Panels


To change the properties of a tube, click to select the row or tube, and then right-click and select properties from the menu that appears. When you uncheck User defined tube pass layout after changing the bundle, all changes you have made are discarded, and the bundle is laid out according the information at the top of the panel. The fields that were previously unavailable for input then become available. When this field remains unchecked, tube layout is based on the overall information and layout code entered on the Bundle and Bundle Layout panels.

Legend Details Bundle Information Bundle width Number of tuberows Number of tubes Minimum wall clearance Left Right Number of tubes per pass Tubepass #1 Tubepass #2 etc.

Bundle Layout Tube Information The table contains one line for each tube type in your exchanger. Printed headings without comments are self-explanatory. Name Type

Name for each tube specified on Tube Types panel Plain Low-finned High-finned Stud-finned

Outer Diameter

Fin root diameter for high-finned tubes

Wall Thickness Transverse Pitch Longitudinal Pitch Fin Height

Page 54

Zero for plain tubes



Input Panels

Natural Draft panel Use items on these panels to define plenum and chimney geometries for natural draft (i.e., fans-off) calculations, both forced and induced draft. These geometries are extremely important because they control calculated heat transfer and air circulation rates. The calculation method used for natural draft is outlined in HTRI Report AC-9. If you request a natural draft calculation and do not enter values on this panel, X ace makes the following assumptions: Plenum height is equal to fan diameter. Plenum width and length are same as bundle dimensions. Recovery (chimney) height is 0.3m (1 ft). Recovery (chimney) width and length are same as bundle dimensions. Forced Draft Exchanger


Page 55

Input Panels


Induced Draft Exchanger

Wind velocity At present, X ace does not use this field. Entries are ignored.

Recovery (chimney) length Specifies length of recovery. Forced draft units Chimney present

Enter length of bundle or chimney.

No chimney present

Enter 0 (zero).

Induced draft units with plenum on top Calculate effective chimney depth based on actual diameter of unit’s fan or chimney. For example, if chimney is round, calculate equivalent square with same free area and enter that value for both chimney depth and height. Required:

No

Units:

SI: m

Default:

No

US: ft

MKH: mm

Specifying a chimney can improve natural draft performance dramatically.

Recovery (chimney) width Specifies width of recovery. Forced draft units Chimney present Page 56

Enter width of bundle or chimney. © Heat Transfer Research, Inc. All rights reserved. Confidential: For HTRI member use only.


No chimney present

Input Panels

Enter 0 (zero).

Induced draft units with plenum on top Calculate an effective chimney width based on actual diameter of unit’s fan or chimney. For example, if chimney is round, calculate an equivalent square with same free area and enter that value for both chimney depth and height. Required:

No

Units:

SI: m

Default:

No

US: ft

MKH: mm

Specifying a chimney can improve natural draft performance dramatically.

Recovery (chimney) height Specifies height of recovery chimney. Increasing chimney height improves exchanger heat transfer. The most dramatic increase in heat duty takes place when first meter of chimney height is added. You can also use dimensions of recovery chimney for induced draft cases. Required:

No

Units:

SI: m

Default:

0.304 m (1 ft)

US: ft

MKH: mm

US: ft

MKH: mm

US: ft

MKH: mm

Plenum length Specifies length of plenum. Required:

No

Units:

SI: m

Default:

No

Plenum width Specifies width of plenum. Required:

No

Units:

SI: m

Default:

Bundle width

Plenum height Specifies height of plenum. To see a diagram of plenum height in a forced draft unit, click here. {bmc SHORTCUT.shg} To see a diagram of plenum height in an induced draft unit, click here. {bmc SHORTCUT.shg} © Heat Transfer Research, Inc. All rights reserved. Confidential: For HTRI member use only.

Page 57

Input Panels


Required:

No

Units:

SI: m

US: ft

MKH: mm th

Default: Based on 45 deg. plenum angle as defined in API Standard 661, 4 edition, ¶ 6.2.3.4 and ¶ 6.3.4.7

Diagram of Plenum Height

Diagram of Plenum Height, Forced Draft Units

Page 58



Input Panels

Diagram of Plenum Height, Induced Draft Units

Process input panel The Process panel has 2 versions: one for air coolers, and the other for economizers. Use these panels to specify process conditions for hot and cold fluids or tubeside and airside fluids. You must enter enough process conditions for X for X ace to ace to determine duty. Click an item on the figures below to learn more about it. {bmc procpnlac.shg} {bmc procpnlecon.shg}

Single-phase Hot

Cold

Flow rate

Flow rate (not required for air coolers)

Inlet temperature

Inlet temperature

Outlet temperature

Outlet temperature (not required for air coolers)

Two-phase Hot

Cold

Flow rate

Flow rate

Inlet temperature OR Weight fraction vapor

Inlet temperature OR Weight fraction vapor

Outlet temperature OR Weight fraction vapor

Outlet temperature OR Weight fraction vapor © Heat Transfer Research, Inc. All rights reserved. Confidential: For HTRI member use only.

Page 59

Input Panels


For Rating or Design Cases If you

Then you must enter

Enter exchanger duty

2 of 3 process conditions for each fluid for economizers 2 of 3 hot process conditions and cold inlet temperature for air coolers

Do not enter exchanger duty

5 of 6 process process conditions for both fluids for economizers 4 of 6 process conditions for both fluids with all three hot fluid conditions for air coolers

For Simulation cases If you

Then you can omit

Enter exchanger duty

Same rules as Rating or Design Cases

Do not enter exchanger duty

Cold fluid flow rate and exit process conditions OR Hot fluid and cold fluid exit process conditions

Overspecification If you specify more than minimum number of process conditions, X conditions, X ace uses ace uses the following rules: X ace always ace always respects temperature specifications. If necessary, X necessary, X ace adjusts ace adjusts weight fraction vapor. X ace respects ace respects associated weight fraction vapor if you do not enter a process temperature. X ace always ace always respects flow rates. X rates. X ace calculates ace calculates flow rate only if not specified. If you specify all 6 process conditions and If

Then You do not enter duty and duties calculated from hot and cold process conditions do not match

X ace runs ace runs case as entered.

Duties differ by more than 5%

X ace issues ace issues a message.

Duties differ by more than 99%

X ace aborts ace aborts run.

Page 60



Input Panels

Fluid name Names hot and cold fluids up to 12 characters. These names label shellside and tubeside fluids in output report. Required:

No

Units:

None

Default:

Blank name

Fluid phase Sets phase of fluid.

Economizers Air Coolers

Hot Fluid

Cold Fluid

Two-phase

Condensing

Boiling

Sensible gas

All vapor

All vapor

Sensible liquid

All liquid

All liquid

Required:

Yes

Units:

None

Default:

Two-phase

If you select Sensible gas or Sensible liquid, X liquid, X ace sets ace sets fluid weight fraction vapors automatically. Conversely, if you set inlet and outlet weight fraction vapors, X vapors, X ace sets ace sets this field. If you have a two-phase component but do not know inlet or outlet conditions, specify Two-phase and X and X ace calculates ace calculates missing process conditions.

Airside flow rate units Sets flow rate units of airside fluid. Standard conditions are defined as dry air at 21.11 °C (70 °F) and 101.325 kPa (14.696 psia), which results in an air density of 1.1997 kg/m³ (0.075 lb/ft³). SI

US

MKH

Mass flow rate

kg/s

1000 lb/hr

1000 kg/s

Actual flow rate

actual m³/s

ACFM

actual m³/s

Face velocity

m/s

ft/min

m/s

Standard flow rate

standard m³/s

SCFM

standard m³/s

Required:

Yes

Units:

None © Heat Transfer Research, Inc. All rights reserved. Confidential: For HTRI member use only.

Page 61

Input Panels

Default:


Face velocity

If you select airside flow rate units in this field, unit for airside flow rate changes.

Flow rates Specifies flow rate of hot and cold process fluids. For units of airside flow, see Airside flow rate units. Required:

No

Units:

SI: kg/sec kg/sec

Default:

None

US: 1000 lb/hr

MKH: 1000 kg/hr

To determine duty, X duty, X ace needs ace needs 3 process conditions (flow rate, inlet temperature and outlet temperature, weight fraction vapor for two-phase fluids) for each fluid. X fluid. X ace does ace does not override user-specified flow rates. If duties calculated from hot and cold fluids do not match, X match, X ace runs ace runs case and issues a warning if process duties differ by more than 5%.

Inlet fraction vapor Specifies inlet weight fraction vapor of hot and cold process fluids. Include any components present in only a single phase (e.g., nonboiling or noncondensable) in your entered value. Required:

For single-phase; optional for two-phase

Units:

None

Default:

None

If you enter a two-phase weight fraction vapor (i.e., not 0 or 1) and a program-calculated heat release curve indicates that your specified inlet temperature is inconsistent, X inconsistent, X ace modifies ace modifies your weight fraction vapor to be consistent with specified temperature.

Outlet fraction vapor Specifies outlet weight fraction vapor of hot and cold process fluids. Include any components present in only single phase (e.g., nonboiling or noncondensable) in your entered value. Required:

Value between 0.0 and 1.0 inclusive

Units:

None

Default:

None

If you enter a two-phase weight fraction vapor (i.e., not 0 or 1) and a program-calculated heat release curve indicates that your specified outlet temperature is inconsistent, X ace modifies ace modifies weight fraction vapor to be consistent with specified temperature.

Inlet temperature Specifies inlet temperature of hot and cold process fluids. X fluids. X ace treats ace treats a temperature of 0.0 as an unspecified value. If you want 0.0 temperature, use 0.001.

Page 62



Required:

Yes

Units:

SI: °C

Default:

None

Input Panels

US: °F

MKH: °C

X ace requires you to specify a certain number of process conditions.

Outlet temperature Specifies outlet temperature of hot and cold process fluids. X ace treats a temperature of 0.0 as an unspecified value. If you want 0.0 temperature, use 0.001. Required:

Yes

Units:

SI: °C

Default:

None

US: °F

MKH: °C

X ace requires you to specify a certain number of process conditions.

Inlet pressure Specifies inlet pressure of hot and cold process fluids. Required:

For all fluids except single-phase liquids

Units:

SI: kPa

Default:

None

US: psia

MKH: kg/cm² A

Entered value must be greater than 0.0. Even though inlet pressure is not required for single-phase liquids, specify a value to avoid appearance of negative pressures on your output reports.

Allowable pressure drop Specifies maximum allowable pressure drop for hot and cold process fluids. Required:

No

Units:

SI: kPa

US: Psi

MKH: kg/cm²

Air side

Pa

in. H2O

mm H2O

Default:

None

Fouling resistance Sets fouling resistance for hot and cold fluids. Any value that you enter must be greater than or equal to zero. Base hot fluid value on hot fluid surface area and cold fluid value on cold fluid surface area. Required:

No

Units:

SI: m² °C/W

US: hr ft² °F/Btu

MKH: m² °C hr/kcal


Page 63

Input Panels

Default:


Zero

Do not use fouling factor as a safety factor. If safety factors are necessary, enter actual safety factors using fields on Safety Factors panel. For more information on fouling resistances, refer to HTRI Report F4. Heat exchanger designers often use fouling factors as safety factors to compensate for perceived deficiencies in exchanger design methods rather than as an allowance for fouling. However, under normal operating conditions many industrial fluids have essentially zero fouling, such as in condensation of light hydrocarbons. HTRI correlations require no additional safety factors. Achieve optimum design by entering values that reflect expected fouling for exchanger fluids at desired process conditions. A large fouling factor typically indicates an undesirable design; consider alternative designs.

Fouling layer thickness Sets fouling layer thickness for hot and cold fluids. Any value that you enter must be greater than or equal to zero. Required:

No

Units:

SI: mm

Default:

Zero

US: in.

MKH: mm

NOTE: Fouling layer thickness decreases available flow area, which usually increases both heat transfer and pressure drop. Errors in calculated pressure drop can result if you enter a large fouling resistance but omit fouling layer thickness.

Diagram of Fouling Resistance vs. Layer Thickness

Page 64



Input Panels

Thermal Conductivity Curve

W/m K

Btu/hr ft F

Typical Fouling Material

1

0.066

0.04

lamp black

2

0.144

0.08

lubricating oil

3

0.235

0.14

paraffin wax

4

0.346

0.20

—

5

0.450

0.26

—

0.606

0.35

hematite

0.606

0.35

water

0.625

0.36

asphalt

0.709

0.41

biofilm

0.900

0.52

cement

0.934

0.54

calcite (boiler deposit)

1.038

0.60

serpentine (boiler deposit)

1.211

0.70

analcite

1.315

0.76

gypsum (boiler deposit)

1.385

0.80

cooling tower water

2.163

1.25

magnesium phosphate

2.335

1.35

calcium sulfate

2.510

1.45

CaSO4 boiler scale

2.595

1.50

calcium phosphate

2.872

1.66

magnetic iron oxide

2.941

1.70

calcium carbonate

5.481

3.17

cracking coil coke

6

7

8

9

10

°


Page 65

Input Panels


Exchanger duty Specifies duty of heat exchanger. If

Then X ace can calculate duty from process conditions you enter

This value becomes required duty used in overdesign calculations: % Overdesign = (U actual – U required ) / U required * 100

X ace cannot calculate exchanger duty from process conditions you enter

X ace uses this value to calculate missing process conditions.

Required:

For airside fluid

Units:

SI: MegaWatts

Default:

None

US: MM Btu/hr

MKH: MM kcal/hr

Duty/flow multiplier Specifies a multiplication factor that X ace applies to specified process flow rates and specified duty. Use this field to rate your exchanger for over- or undercapacity without modifying original input. Required:

No

Units:

None

Default:

1.0

Reported flow rates and duties reflect specified multiplication factor. X ace also issues an informative message providing multiplication factor values.

Design input panel group Panels in this group define parameters used to control design option. The design data summary shows geometry parameters currently selected for modification by design logic. NOTE:

Page 66

You must use component-by-component options before you can specify dew and bubble points.



Input Panels

Design Geometry panel Fields on this panel determine which geometry parameters the design logic considers. You can specify the valid range of these same geometry parameters. Values determine the set of cases run by the design logic. The fields available for input depend on the type of case you select in Design Mode Control.

For Grid design only , you must check at least one checkbox and input fields Minimum, Maximum, and Step Size. You can then input the field Specified for all other parameters.

Bundle width checkbox Specifies whether design logic varies bundle width. Classic design Specified range increment given

X ace designs bundle within specified limits, adjusting bundle size by

Unspecified range X ace supplies default values Grid design X ace runs a grid using your specified series of values. Required:

No

Units:

None

Default:

None

If you specified a bundle width on Bundle panel, setting this value causes X ace to override your specified value. For Classic design, X ace automatically varies bundle width if you do not enter it. Checking the box allows you to override program-supplied values.


Page 67

Input Panels


Bundle width – Specified Specifies width of bundle in exchanger. The value is a distance between edges of bundle excluding any flanges. X ace uses this dimension as width of exchanger for tubes and face area calculations, determining number of tubes by dividing pitch into width and subtracting clearance specified to first tube in each row. Required:

Yes (Rating and Simulation) No (Classic and Grid)

Units:

SI: m

Default:

None

US: ft

MKH: mm

If you enter this dimension, you should not specify number of tubes in even- and odd-numbered rows. If you enter both this width and number of tubes in rows, number of tubes overrides bundle width if tubes do not fit into width you entered.

Bundle width – Minimum Specifies minimum bundle width for design logic to try. Classic If you enter this value, you can also enter values for maximum and step size. If you specify minimum and/or maximum bundle width without specifying step size, X ace uses default value for omitted value. If you do not set minimum and maximum values, design logic sets minimum based on tube length using API 661 standard of 40% bundle coverage by fans (for economizers, a minimum bundle of 1.2 m (4 ft) is used), maximum as 3.3 m (14 ft), and 10 steps. Grid You must specify minimum, maximum, and step size. Required:

No

Units:

SI: m

Default:

None

US: ft

MKH: mm

Bundle width – Maximum Specifies maximum bundle width for design logic to try. Classic If you enter this value, you can also enter values for minimum and step size. If you specify minimum and/or maximum bundle width without specifying step size, X ace uses default value for omitted value. If you do not set minimum and maximum values, design logic sets minimum based on tube length using API 661 standard of 40% bundle coverage by fans (for economizers, a minimum bundle of 1.2 m (4 ft) is used), maximum as 3.3 m (14 ft), and 10 steps. Grid You must specify minimum, maximum, and step size. Required: Page 68

No © Heat Transfer Research, Inc. All rights reserved. Confidential: For HTRI member use only.


Units:

SI: m

Default:

None

Input Panels

US: ft

MKH: mm

Bundle width – Step Size Specifies size of variance in bundle width. The design logic always runs minimum and maximum values even if specified range (maximum – minimum) is not evenly divisible by step size. Classic If you enter this value, you can also enter values for minimum and maximum. If you specify minimum and/or maximum bundle width without specifying step size, X ace uses default value for omitted value. If you do not set minimum and maximum values, design logic sets minimum based on tube length using API 661 standard of 40% bundle coverage by fans (for economizers, a minimum bundle of 1.2 m (4 ft) is used), maximum as 3.3 m (14 ft), and 10 steps. Grid You must specify minimum, maximum, and step size. Required:

No

Units:

SI: mm

Default:

None

US: in.

MKH: mm

Tubepasses checkbox Specifies whether design logic varies number of tubepasses. Required:

No

Units:

None

Default:

None

If you specified number of tubepasses on Unit panel, setting this value causes X ace to override your specified value. For Classic designs, X ace automatically varies number of tubepasses if you do not enter a value. Checking the box allows you to override program-supplied values.

Tubepasses – Specified Specifies number of tubepasses in exchanger bundle. The maximum number of tubepasses that X ace allows is 1440. Required:


Units:

None

Default:

0

For design cases, this item is usually omitted. If you specify, X ace treats value you enter as only value permitted while designing exchanger.


Page 69

Input Panels


Tubepasses – Minimum Specifies minimum number of tubepasses in exchanger bundle for Grid design. Available for Grid design only. You must enter values for minimum, maximum, and step size. Required:

No

Units:

None

Default:

0

Tubepasses – Maximum Specifies maximum number of tubepasses in exchanger bundle for design. The maximum allowed number of tubepasses is 1440. Classic

X ace uses value you enter as maximum number permitted in final design.

Grid

You must enter values for minimum, maximum, and step size.

Required:

No

Units:

None

Default:

0

Tubepasses – Step Size Specifies step size for number of tubepasses in exchanger bundle for Grid design. Available for Grid design only. You must enter values for minimum, maximum, and step size. Required:

No

Units:

None

Default:

0

Face velocity checkbox Specifies whether design logic varies face velocity approaching bundle. Classic X ace designs a bundle within limits you specify. If you do not specify minimum, maximum, and step size, X ace supplies default values Grid You must enter a minimum, maximum, and step size value. X ace runs a grid using specified series of values. Required:

No

Units:

None

Default:

None

Face velocity – Specified Specifies face velocity of outside fluid approaching bundle. Required: Page 70



Units:

SI: m

Default:

None

Input Panels

US: ft

MKH: mm

If you enter this value, X ace uses it as the only face velocity for design.

Face velocity – Minimum Specifies minimum face velocity limits for design logic to try. Classic X ace automatically determines face velocity if you do not enter it. If you checked the box, you can override program-supplied values. Grid If you enter this value, you must also enter values for maximum and face velocity adjustment. Required:

No

Units:

SI: m

Default:

None

US: ft

MKH: mm

Face velocity – Maximum Specifies maximum face velocity for design logic to try. Classic X ace automatically determines face velocity if you do not enter it. If you checked the box, you can override program-supplied values. Grid If you enter this value, you must also enter values for minimum and face velocity adjustment. Required:

No

Units:

SI: m

Default:

None

US: ft

MKH: mm

Face velocity – Step Size Specifies face velocity step size for X ace to use. The grid design logic always runs minimum and maximum values even if specified range (maximum – minimum) is not evenly divisible by step size. Classic If you enter this value, you can also enter values for minimum and maximum. If you specify minimum and/or maximum without specifying step size, X ace uses default value for omitted value. X ace uses this value only for adjusting airflow rate at the end of design. Grid You must specify minimum, maximum, and step size. Required:

No

Units:

SI: m/s

US: ft/sec

MKH: m/s


Page 71

Input Panels

Default:


None

Longitudinal pitch checkbox Specifies whether design logic varies longitudinal pitch. Available for Grid only. You must enter values in minimum, maximum, and step size fields. X ace runs a grid using specified series of values. Required:

No

Units:

None

Default:

None

Longitudinal pitch – Specified Specifies longitudinal pitch. X ace automatically supplies longitudinal pitch for high-finned tubes selected from Automatic Tube Data Bank. Required:

For non-equilateral staggered and inline tube banks only Not required for equilateral layouts.

Units:

SI: mm

Default:

None

US: in.

MKH: mm

X ace automatically supplies longitudinal pitch for high-finned tubes selected from Automatic Tube Data Bank.

Longitudinal pitch – Minimum Specifies minimum longitudinal pitch for grid design option. You must enter values for minimum, maximum, and step size. Required:

No

Units:

SI: mm

Default:

None

US: in.

MKH: mm

Longitudinal pitch – Maximum Specifies maximum longitudinal pitch for grid design option. Required:

No

Units:

SI: mm

Default:

None

US: in.

MKH: mm


Longitudinal pitch – Step Size Specifies longitudinal pitch step size for grid design option. Required:

No

Units:

SI: mm

Page 72

US: in.

MKH: mm



Default:

Input Panels

None


Transverse pitch checkbox Specifies whether design logic should vary transverse pitch. If you click the check box, minimum, maximum, and step size fields become available. You must enter all values; X ace runs a grid using specified series of values. Required:

No

Units:

None

Default:

None

A Grid design can be either a series of design cases or rating cases.

Transverse pitch – Specified Specifies transverse tube pitch. Required:

Yes

Units:

SI: mm

Default:

None

US: in.

MKH: mm

X ace automatically supplies transverse pitch for high-finned tubes selected from Automatic Tube Data Bank.

Transverse pitch – Minimum Specifies minimum transverse pitch. Required:

No

Units:

SI: mm

Default:

None

US: in.

MKH: mm


Transverse pitch – Maximum Specifies maximum transverse pitch. Required:

Yes

Units:

SI: mm

Default:

None

US: in.

MKH: mm


Transverse pitch – Step Size Specifies transverse pitch step size. Required:


Page 73

Input Panels


Units:

SI: mm

Default:

None

US: in.

MKH: mm


Tube length checkbox Specifies whether design logic should vary tube length. If you vary this parameter, you must also enter values for minimum, maximum, and step size. Required:

No

Units:

None

Default:

None

If you specified tube length on Bundle panel, setting this value causes X ace to override your specified value.

Tube length – Specified Specifies length of tubes in exchanger bundle. Required:


Units:

SI: m

Default:

No

US: ft

MKH: mm

Tube length – Minimum Specifies minimum tube length for design logic to try. If you enter this value, you must also enter values for maximum and either step size or number of steps. X ace runs every tube length from minimum to maximum using steps and step sizes to determine which intermediate values to run. Required:

No

Units:

SI: m

Default:

No

US: ft

MKH: mm

By setting this value along with maximum and either step size or number of steps, you define a set of tube lengths for design logic to run.

Tube length – Maximum Specifies maximum tube length that design logic should try. If you enter this value, you must also enter values for minimum and either step size or number of steps. X ace runs every tube length from minimum to maximum using steps and step sizes to determine which intermediate values to run. Required:

No

Units:

SI: m

Default:

No

Page 74

US: ft

MKH: mm



Input Panels

By setting this value along with minimum and either step size or number of steps, you define a set of tube lengths for design logic to run.

Tube length – Step Size Specifies tube length step size used by design logic. X ace runs cases from minimum to maximum tube length using specified step size. The design logic always runs minimum and maximum values even if specified range (maximum – minimum) is not evenly divisible by step size. Required:

No

Units:

SI: m

Default:

None

US: ft

MKH: mm

By setting this value, along with Minimum and Maximum fields, you define a set of tube lengths that design logic runs.

Tuberows checkbox Specifies whether design logic varies number of tuberows. If you click the check box, Minimum, Maximum, and Step Size fields become available. You must enter all values. X ace runs a grid using your specified values. Required:

No

Units:

None

Default:

None

A Grid design can be a series either of design cases or of rating cases.

Tuberows – Specified Specifies number of tuberows for design logic. Required:

Yes for Rating and Simulation No for Classic and Grid* designs

Units:

None

Default:

None

Up to 60 rows are allowed. Fewer that 4 rows is not good practice. *For Grid design, you must input Specified OR Minimum, Maximum, and Step Size

Tuberows – Minimum Specifies minimum number of tuberows for design logic. Required:

No

Units:

None

Default:

None

A Grid design can be a series either of design cases or of rating cases. © Heat Transfer Research, Inc. All rights reserved. Confidential: For HTRI member use only.

Page 75

Input Panels


Tuberows – Maximum Specifies maximum number of tuberows for design logic. Required:

No

Units:

None

Default:

None


Tuberows – Step Size Specifies minimum number of tuberows for design logic. Required:

No

Units:

None

Default:

None


Tube outside diameter checkbox Specifies whether design logic varies outside tube diameter. If you click the check box, minimum, maximum, and step size fields become available. You must enter all values. X ace runs a grid using your specified values. Required:

No

Units:

None

Default:

None


Tube outside diameter – Specified Specifies outside diameter of tubes. Required:

No

Units:

SI: m

Default:

None

US: ft

MKH: mm

For low-finned tubes, this value is plain end diameter.

Tube outside diameter – Minimum Specifies minimum tube outside diameter for design logic. Required:

No

Units:

SI: mm

Default:

None

Page 76

US: in.

MKH: mm



Input Panels

If you enter a value for minimum, you must enter values for maximum and step size.

Tube outside diameter – Maximum Specifies maximum tube outside diameter. Required:

No

Units:

SI: mm

Default:

None

US: in.

MKH: mm

If you enter a value for maximum, you must enter values for minimum and step size.

Tube outside diameter – Step Size Specifies tube outside diameter step size for grid design option. Required:

No

Units:

SI: mm

Default:

None

US: in.

MKH: mm

If you enter a value for step size, you must enter values for minimum and maximum.

Design Mode Control – Classic X ace designs smallest exchanger with minimum number of bays in parallel that fulfills given geometry, process, and physical property constraints. Process constraints must include heat duty (either specified or implicit) and can include pressure drop and/or velocity restraints. The minimum exchanger geometries necessary are Tube length Pitch Layout type Tube diameter Tube wall thickness Required:

No

Units:

None

Default:

Rating

Design Mode Control – Grid A grid design can be either a series of ratings or a series of designs, according to information you specify. The minimum exchanger geometries necessary are Tube length Pitch Layout type Tube diameter Tube wall thickness © Heat Transfer Research, Inc. All rights reserved. Confidential: For HTRI member use only.

Page 77

Input Panels


Required:

No

Units:

None

Default:

Rating

Design Mode Control – Rating For geometrically specified exchangers, a rating case requires sufficient process information to determine exchanger duty: Number of tubepasses Number of rows Bundle width Tube length Pitch Layout angle Tube diameter Tube wall thickness Required:

No

Units:

None

Default:

Rating

Design Mode Control – Simulation Simulations differ from ratings only in amount of process information supplied. A simulation (unknown duty case) has fewer process information requirements. X ace calculates expected performance of exchanger based on specified geometry and initial process conditions. Required:

No

Units:

None

Default:

Rating

Design Constraints panel This panel contains fields that provide constraints on design logic.

Page 78



Input Panels

Velocity – Minimum Specifies minimum fluid velocity for hot or cold fluid during a design run. Required:

No

Units:

SI: m/sec

Default:

None

US: ft/sec

MKH: m/sec

Velocities used for comparison are midpoint velocities printed on Final Results. For air-cooled heat exchangers, X ace ignores any entries for cold fluid on this panel. Enter air velocity limits on Design Geometry panel.

Velocity - Maximum Specifies maximum fluid velocity for hot or cold fluid during a design run Required:

No

Units:

SI: m/sec

Default:

None

US: ft/sec

MKH: m/sec

Velocities used for comparison are midpoint velocities printed on Final Results. For air-cooled heat exchangers, X ace ignores any entries for cold fluid on this panel. Enter air velocity limits on Design Geometry panel.

Pressure drop allowed in inlet nozzles Specifies maximum pressure drop in inlet nozzles allowed by design logic. Required:

No

Units:

Percent of total pressure drop

Default:

10% of allowable pressure drop

Pressure drop allowed in outlet nozzles Specifies maximum pressure drop in outlet nozzles allowed by design logic. Required:

No

Units:

Percent of total pressure drop

Default:

10% of allowable pressure drop


Page 79

Input Panels


Design Warnings panel Items on this panel specify conditions for the design logic to use as warnings. X ace provides warning messages if the final design violates any limits on this panel.

Minimum tube wall temperature Specifies wall temperature below which X ace indicates warning. Required:

No

Units:

SI: °C

Default:

None

US: °F

MKH: °C

Maximum tube wall temperature Specifies wall temperature above which X ace indicates a warning. Required:

No

Units:

SI: °C

Default:

None

US: °F

MKH: °C

Control input panel group Panels in this group define optional case control data: case descriptions, methods, safety factors, and vibration screening parameters. The Control summary panel contains a subset of more commonly used input items in this panel group.

Page 80



Input Panels

Case description Specifies additional descriptive information for current input case. Use up to 72 alphanumeric characters in this field. Required:

No

Units:

None

Default:

None

This label appears in header lines of all output report pages.

Problem description Specifies descriptive title for current input case. Use up to 72 alphanumeric characters in this field. Required:

No

Units:

None

Default:

None

This label appears in header lines of all output report pages.

Flow Maldistribution panel Use items on the Flow Maldistribution panel to specify airside maldistribution typically present in aircooled heat exchangers. If experimental velocity profile information is available, you can enter it directly.


Page 81

Input Panels


Diagram of Flow Maldistribution

Maldistribution control Sets type of airside (outside) maldistribution that X ace assumes. Required:

No

Units:

None

Default:

No maldistribution

Choices No X ace performs all calculations assuming uniform distribution of air (or maldistribution outside fluid) across face of tube bundle. Estimate maldistribution

Based on HTRI research data, X ace calculates expected airside (outside) maldistribution. Selecting this option also activates blocked air cooler sides options. X ace can estimate maldistribution with no inlet sides blocked or with one or more sides of inlet blocked by obstructions. These methods are based on experimental data obtained on units with three fans. X ace estimates an airside flow multiplier for each section. These multipliers are normalized to 1 and used to adjust the flow rate in each section. For all sides blocked, X ace assumes that the input or calculated flow rate of air accounts for the loss of air flow due to blockage.

NOTE

You must enter Plenum height and Ground clearance to fan blade, Optional panel, when you select any of the Estimate maldistribution options.

Specify maldistribution field

If experimental airside (outside) maldistribution data are available, you can enter relative velocities (or flow quantities) in a grid, which becomes available when you select this option. X ace divides exchanger into a grid of 6 sections across face of bundle and 10 increments down length of tube.

For purposes of entering data, an exchanger is divided into ten sections down length of tube and six sections across the width of the bundle. Think of these sections as boxes or columns that run from bottom to top of the exchanger. Enter relative flow velocity for each box. Page 82



Input Panels

The data you enter on this panel can be either absolute velocities or relative velocities. For example, if air flow in one box is 305 m/min and flow velocity in another box is 610 m/min, you can enter either 305 and 610 or 1 and 2. However, you must be consistent. Required:

No

Units:

None

Default:

None

If you use this panel, you must make an entry for each box and column in exchanger. Do not leave any blanks; enter a zero in any position of bundle.

250

250

350

400

350

350

350

350

325

325

250

350

450

450

400

400

450

450

450

400

250

250

350

375

250

250

350

350

350

350

250

250

350

350

250

250

350

350

250

250

350

350

400

450

375

375

450

375

350

350

300

300

350

350

350

350

350

350

300

300

Check any blocked sides Sets sides of exchanger to be blocked. Required:

No

Units:

None

Default:

None

NOTE: HTRI recommends that all sides remain open.


Page 83

Input Panels


Diagram of Blocked Sides Viewed from the top of the bay, the inlet to the exchanger bundle has four surfaces that can be obstructed by walls or other equipment. These surfaces are referred to as Side 1, Side 2, Side 3, and Side 4. Side 1 is the left side when viewed from above. Other sides are numbered clockwise, as shown. HTRI recommends that all sides remain open. This method applies to every bay, even if the unit has multiple bays or multiple bundles in the bay. X ace uses methods based on data taken from a unit one fan wide and three long, in calm wind conditions. These methods are less accurate for units with fewer or more than three fans, units with substantial wind effects, or units with more than one bundle per bay. See HTRI Reports AC-5 and AC-7.

Temperature Maldistribution panel Use items on the Airside inlet temperature profile value panel to specify a non-uniform airside (outside) temperature profile. Temperature maldistribution sometimes occurs in economizer bundles and other bundles in series on the air side (outside). If experimental temperature profile information is available, you can enter it directly. For purposes of entering data, the exchanger is divided into 10 sections down the length of the tube and 6 sections across the width of the bundle. Think of these sections as boxes or columns that run from the bottom to the top of the exchanger. Enter the average inlet temperature for each box. If you use this panel, you must make a non-zero entry for each box and column in the exchanger. Do not leave any blanks.

Page 84



Input Panels

Methods panel Fields on this panel control the methods X ace uses to predict heat transfer and pressure drop performance. All fields on this panel are optional.

Outside friction factor method Sets type of single-phase friction factor correlation for X ace to use for outside fluid. Required:

No

Units:

None

Default:

Commercial

Smooth Tube results in a slightly lower friction factor. This input is available for economizers only. It does not apply to air-cooled exchangers.

Tubeside friction factor method Sets type of single-phase friction factor correlation for X ace to use for tubeside fluid. Required:

No

Units:

None

Default:

Commercial

Smooth Tube results in a slightly lower friction factor.

Pure component condensation Informs X ace whether you are condensing a pure component. Required:

No

Units:

None

Default:


Page 85

Input Panels


By default, X ace adds a vapor-phase resistance to condensing heat transfer coefficient, a necessary penalty for multicomponent condensation. This correction does not apply to single components; in those cases, select Yes.

Condensable components Specifies number of condensable components. A modification to RPM condensation method adjusts vapor-phase heat transfer coefficient according to number of condensing components. The correlation distinguishes between one condensable component and more than one condensable component. Required:

No

Units:

None

Default:

1 (one)

A value larger than 1 (one) for this input improves condensing coefficient slightly, consistent with experimental data. The improved RPM is discussed in Section 4 of Report CT-10.

Condensation method Defines correlation for predicting condensing heat transfer coefficient. Required:

No

Units:

None

Default:

RPM

Method

Description

RPM (Resistance Proration Method)

HTRI-developed method, recommended for all cases. (If inerts are present, enter a value for Mole fraction inert at inlet, Methods panel unless water is the only condensing component.)

Literature

Uncorrected Ward-Silver-Bell proration method. Included for comparison with other methods, it is not recommended.

CPM (Composition Profile Method)

HTRI’s adaptation of film-theory methods, developed for condensation of hydrocarbons in the presence of inerts. The Resistance Proration method with a specified inert fraction is now recommended for this type of case. Values produced by this method are too low, according to research data. Do not use for mixtures containing polar (e.g., water, alcohols) compounds If you choose this method, X ace must calculate heat release curve, which means that you must use only internal database components for hot fluid and select Program Calculated for heat release curve on Hot/Cold Fluid Properties panel. Enter composition profile data on the Physical Property panel.

Reflux

Page 86

Used for vertical intube reflux condensation, vapor enters at bottom. Liquid condenses on tube wall and drains out the bottom. Proper use of the reflux condensation method requires specific exchanger geometry and special input considerations.



Input Panels

Rose-Briggs

Special method that provides improved accuracy for shellside condensation on low-finned tubes. HTRI Report CS-11 contains a description of this method.

Ammonia-Water

Modification of CPM method for ammonia-water mixtures only. Do not use this method with other mixtures.

High-Fin Dehumidification

Applicable for air-water systems only, the method is a Colburn-Houghen type that uses HTRI basic heat transfer methods for the liquid film and sensible gas heat transfer coefficients. These coefficients are combined with mass transfer relationships using an assumption of 1 (one) for the Lewis number.

High-Fin Approximation

This method is a simplified RPM based on TPG-1. In this method, condensate film coefficient is assumed to be large enough that vapor-phase resistance is the controlling resistance in the system, allowing the condensate film resistance to be assumes as unity. The vapor-phase coefficient is then calculated by correcting the sensible vapor coefficient with a ratio of duty to sensible vapor. The Resistance Proration method with a specified inert fraction is now recommended for this type of case. Values produced by this method are too low, according to research data.

For tubeside condensation, enter Mole fraction inert at inlet (Methods panel) and use the Resistance Proration method if you do not have the composition profile data. Inert is defined as any component with negligible condensation in the current exchanger. The Rose-Briggs Method is a theoretical advancement over the Katz-Beatty method for condensation of pure vapors on integral-finned tubes in gravity-controlled flow. It predicts the amount of surface blanketed by condensate and also accounts for separate condensation mechanisms for fin tips, flanks, and roots. In addition, it takes into account the effect of fin metal conductivity on the wall temperature of the three condensation regions. Comparison with the HTRI-modified Katz-Beatty Method shows the Rose-Briggs Method to be more sensitive to metal thermal conductivity. HTRI has modified the flooding calculation procedure of the RoseBriggs Method so that it predicts HTRI data for mixtures and for pure vapors as well as or better than the modified Katz-Beatty Method. The ammonia-water condensation method calculates the heat transfer coefficient using vapor and liquid composition profiles along the condenser’s length. Differs from the default CPM because the Lewis number is not a constant value (Le = 1.0) and is a function of the pressure, temperature, and weight of the constituents. Suitable for mass and heat transfer characteristics of the non-ideal ammonia-water mixture provided that accurate condensing heat release curves and fluid properties are entered. Users should specify heat release curves and grid properties. Ammonia-water mixtures, often used in refrigeration cycles, recently have been considered for use as the working fluid for power generating cycles (e.g., Kalina cycle). The National Renewable Energy Laboratory (NREL), as part of the Geothermal Division of the U.S. Department of Energy, has sponsored several © Heat Transfer Research, Inc. All rights reserved. Confidential: For HTRI member use only.

Page 87

Input Panels


research and development projects that use ammonia-water mixtures as the working fluid. For one of these projects, HTRI modified the CPM to model the condensation of ammonia-water mixtures. Heat transfer predictions using the modified CPM have been compared with vertical tubeside condensation data taken from an NREL double-pipe test condenser. Data were measured at inlet ammonia vapor concentrations of 0.65 to 0.85 (by weight) and pressures between 26 and 52 psia. The modified CPM provides a better match to the measured results than all other available methods.

Mole fraction noncondensables Sets mole fraction of noncondensables in condensing fluid feed stream. A noncondensable is any component that exhibits negligible condensation in current exchanger. This parameter is used only by Resistance Proration Method (RPM). Do not enter if water is only condensing component. Required:

No

Units:

None

Default:

X ace sets value if you use Program-calculated heat release curve.

For condensation, always set a value if inerts are present in your condensing fluid and use RPM option.

Momentum recovery to include Specifies percentage of momentum recovery to exclude from calculated condensation pressure drop. The valid range is 0 – 100 percent. Required:

No

Units:

Percent

Default:

0% (Include all momentum recovery in calculated condensation pressure drop.)

X ace has a method to predict this effect for tubeside condensation. Unless experimental data are available to determine a value, HTRI recommends that you enter 0.

Pure component boiling Informs X ace whether you are boiling a pure component. Required:

No

Units:

None

Default:

No

By default, X ace adds a vapor-phase resistance to boiling heat transfer coefficient, a necessary penalty for multicomponent boiling. This correction does not apply to single components; in those cases, select Yes.

Check film boiling Determines whether X ace checks for film boiling. Required:

No

Units:

None

Default:

Yes

Page 88



Input Panels

Usually, you should allow X ace to perform calculations that check for film boiling. If X ace predicts film boiling and you have plant data that show otherwise, select No to bypass film-boiling calculations.

Boiling method Sets correlation for X ace to use in calculating nucleate boiling coefficient. Required:

No

Units:

None

Default:

Phys Prop/TBR

Method

Description

Physical Property/BR

Physical property-based, with boiling range mixture correction, good for reduced pressures less than 0.6

Physical Property/ Schlünder

Physical property-based, with Schlünder mixture correction, recommended for binary mixtures when good vapor-liquid equilibrium data are available

Physical Property/TBR

Physical property-based, with theoretical boiling range mixture correction (default)

HTRI Falling Film Evaporator

Vertical tubeside falling film evaporator using HTRI film convection method and an empirically derived boiling range mixture correction factor, recommended for falling film evaporators

Chun-Seban Falling Film

Vertical tubeside falling film using Chun-Seban method and an empirically derived boiling range mixture correction factor

Reduced Property/BR

Reduced property-based, with boiling range mixture correction, original HTRI method developed for hydrocarbons at reduced pressures less than 0.6

For X ace to use the Schlünder method, it must have compositions: use with internal databank components and program-generated heat release curve or input composition profiles on a Physical properties panel.

Falling film evaporators X ace prints no messages regarding flow distribution because it assumes even flow distribution. Find header distribution information in HTRI Report BT-5 and tube distribution information in HTRI Report BT9.

If

Then You choose a single-pass vertical tubeside falling film evaporator

Inlet = saturated vapor and/or vapor/liquid mixture. Vapor and liquid are in downflow and exit together at bottom of exchanger. See BT-10 and Research Brief 3-8 for descriptions of heat transfer methods, Design Manual for standard HTRI two-phase pressure drop methods.


Page 89

Input Panels


If

Then Liquid flow is insufficient for wetting, according to Hartley-Murgatroyd method described in BT-11

X ace prints a message.

Boiling side temperature difference is greater than 45 °F (25 °C), present generally accepted limit for onset of film-destructive nucleate boiling

X ace prints a message.

X ace has enough X ace prints a message to warn of possible early breakdown due to information in input to Marangoni effects (see BT-13). This surface tension criterion requires determine mixture-average X ace to make vapor-liquid equilibrium calculations. OH-group surface tension as a function hydrocarbon/water mixtures often have Marangoni-type breakdown. of vaporization temperature For more details on these types of fluids, see HTRI Reports BT-10, BT-11, and BT-13.

Boiling method components Controls calculation of boiling heat transfer coefficient. The boiling heat transfer coefficient has a nucleate component and a convective component. Convective+nucleate

Recommended for all cases

Nucleate only

Not currently recommended

Convective only (fully suppressed nucleate boiling)

Not currently recommended

Required:

No

Units:

None

Default:

Convective+nucleate

Surface correction factor Specifies a surface correction factor. Required:

No

Units:

None

Default:

1.0

X ace does not automatically generate a value. For enhanced surfaces such as sintered tubes, you must enter a value. This factor has an effect only in boiling cases. The surface correction factor acts to multiply the nucleate boiling coefficient.

Page 90



Input Panels

Air-cooler single increment Forces X ace to use a single increment. This option was originally introduced into the program when computer power was much less than currently available in PCs. Instead of calculating tubeside performance in ten steps, X ace is forced to use a single increment. Required:

No

Units:

None

Default:

Multiple increments along tube length

Using this option is not recommended by HTRI. It sacrifices calculation accuracy to save computational time. The savings in execution speed is not significant with modern PCs.

Force phase separation in tube headers Specifies separation of phases in tube headers. If checked, X ace assumes total phase separation in all tube headers with the liquid flowing in the lower tube rows and vapor flowing in the higher tube rows. This option represents a worst-case result, allowing the user to do a "what if" check of the final results. Required:

No

Units:

None

Default:

No

This input has no effect for single-phase tubeside fluids or units with a single tube pass that does not have a two-phase inlet condition. X ace uses a velocity balance to determine the areas needed for all-liquid flow and all-vapor flow. This method assumes that all rows exiting the header have equal velocities. Because velocity is mass divided by flow area and density, the following equation is solved for AL, the cross section area of liquid flow.

M L AL

M V L

ATotalFlow AL

V

X ace then determines the number of rows required for the liquid flow area to equal or exceed AL (starting at the bottom of the bundle). X ace the number of rows needed to fulfill the area requirement for the vapor (starting at the top of the bundle). In some cases, a row has some liquid and some vapor, if the necessary liquid and vapor areas take up a partial row. In these cases, X ace determines the weight fraction vapor of a new row as the mass of vapor remaining divided by the total mass of liquid and vapor in the row. X ace makes two main assumptions in using this method: 1.

Liquid and vapor velocities exiting the header are equal.

2.

The amount of heat transfer in each row does not change with weight fraction vapor changes to account for the phase separation method.

High fin tube heat transfer method Sets heat transfer method for high-finned tubes. © Heat Transfer Research, Inc. All rights reserved. Confidential: For HTRI member use only.

Page 91

Input Panels


HTRI

Based on data from 41 geometries, encompasses all data taken by HTRI since 1962. Recommended for all cases.

Literature

Based on a much smaller data set, primary method in older versions of ACE. Yields a lower heat transfer coefficient over normal design range of air-cooled heat exchangers.

Required:

No

Units:

None

Default:

HTRI

High fin tube pressure drop method Sets pressure drop method for high-finned tubes. HTRI

Based on data from 41 geometries, encompasses all data taken by HTRI since 1962. Recommended for all cases.

Literature

Based on a much smaller data set, primary method in older versions of ACE. Yields a higher pressure drop over normal design range of air-cooled heat exchangers.

Required:

No

Units:

None

Default:

HTRI

HTRI Research Geometry Fin Root

Transverse

Over Fin

Longitudinal

Diameter

Pitch

Diameter

Pitch

mm

in.

mm

in

mm

in

mm

in

Number of Tuberows

25.40

1.000

55.88

2.200

63.50

2.5

54.99

2.165

4

25.40

1.000

55.88

2.200

124.89

4.917

107.70

4.24

4

25.40

1.000

55.88

2.200

63.50

2.500

63.50

2.5

4

3154 – 17501

25.40

1.000

55.88

2.200

93.27

3.672

38.10

1.5

4

4138 – 133984

25.40

1.000

56.64

2.230

60.66

2.388

52.58

2.07

4

2446 – 17176

25.40

1.000

56.64

2.230

63.50

2.500

54.99

2.165

4

1910 – 16903

25.40

1.000

56.64

2.230

70.76

2.786

61.21

2.41

4

2174 – 15798

25.40

1.000

56.64

2.230

60.66

2.388

105.16

4.14

4

2597 – 18144

25.40

1.000

56.64

2.230

70.76

2.786

122.43

4.82

4

2154 – 15581

25.40

1.000

56.92

2.241

92.08

3.625

38.10

1.5

5

1204 – 11975

25.40

1.000

56.92

2.241

92.08

3.625

50.80

2

5

2321 – 11242

25.30

0.996

57.68

2.271

63.50

2.500

54.99

2.165

4

1304 – 17611

25.40

1.000

56.11

2.209

92.08

3.625

79.76

3.14

5

3803 – 12612

38.18

1.503

68.66

2.703

74.30

2.925

64.26

2.53

4

1731 – 32248

38.18

1.503

68.66

2.703

76.20

3.000

66.04

2.6

4

1655 – 33136

68.66

2.703

68.66

2.703

82.55

3.250

71.37

2.81

4

2090 – 27896

38.18

1.503

69.72

2.745

76.20

3.000

66.04

2.6

4

2390 – 30306

Page 92


Reynolds Number Range 2278 – 18763


Input Panels

Fin Root

Transverse

Over Fin

Longitudinal

Diameter

Pitch

Diameter

Pitch

mm

in.

mm

in

mm

in

mm

in

Number of Tuberows

Reynolds Number Range

31.75

1.250

63.30

2.492

69.70

2.744

60.35

2.376

4

1602 – 26469

25.40

1.000

55.88

2.200

63.50

2.500

54.99

2.165

3

2139 – 18302

25.40

1.000

55.88

2.200

63.50

2.500

63.50

2.5

3

3144 – 17738

25.40

1.000

56.64

2.230

60.66

2.388

105.16

4.14

3

2517 – 18146

25.40

1.000

56.64

2.230

70.76

2.786

122.43

4.82

3

3934 – 15577

25.40

1.000

56.92

2.241

92.08

3.625

50.80

2

3

3426 – 11349

25.40

1.000

55.88

2.200

63.50

2.500

63.50

2.5

2

3166 – 17755

25.40

1.000

56.64

2.230

60.66

2.388

52.58

2.07

2

4572 – 17943

25.40

1.000

56.64

2.230

70.76

2.786

61.21

2.41

2

4004 – 15677

25.40

1.000

56.64

2.230

70.76

2.786

122.43

4.82

2

3991 – 15179

25.40

1.000

55.88

2.200

63.50

2.500

54.99

2.165

1

4163 – 18412

25.40

1.000

56.64

2.230

60.66

2.388

52.58

2.07

1

2451 – 17629

25.40

1.000

56.64

2.230

70.76

2.786

61.21

2.41

1

3695 – 15046

25.40

1.000

57.15

2.250

57.15

2.250

54.99

2.165

4

4711 – 19729

25.40

1.000

57.15

2.250

76.20

3.000

54.99

2.165

4

3634 – 16197

25.40

1.000

57.15

2.250

63.50

2.500

54.99

2.165

4

5178 – 19214

25.40

1.000

57.15

2.250

63.50

2.500

54.99

2.165

1

3844 – 17741

25.40

1.000

57.15

2.250

63.50

2.500

54.99

2.165

2

4806 – 18345

25.40

1.000

57.15

2.250

63.50

2.500

54.99

2.165

3

5479 – 18696

50.80

2.000

99.06

3.900

114.30

4.500

99.06

3.9

4

8231 – 38736

50.80

2.000

97.79

3.850

114.30

4.500

99.06

3.9

4

8460 – 39950

50.80

2.000

98.50

3.878

107.95

4.250

93.50

3. 681

4

8669 – 46118

25.40

1.000

57.10

2.248

57.15

2.250

54.99

2.165

4

4166 – 17071

Safety panel Use this panel to specify absolute values and safety factors for heat transfer coefficients. All fields on this panel are optional. Use fields on this panel with care because they adjust the calculated heat transfer and pressure drop.


Page 93

Input Panels


Usually, you should use these fields only for cases in which you have data indicating that X ace does not model the actual performance of the exchanger. You can use these fields if necessary to match field or experimental data for your exchanger.

Hot sensible liquid coefficient Defines a value for hot fluid sensible liquid heat transfer coefficient. Your entered value overrides any value calculated by X ace. Base your entered value on hot fluid's surface area. Required:

No

Units:

SI: W/m² °C

Default:

None

US: Btu/hr ft² °F

MKH: kcal/hr m² °C

X ace applies heat transfer coefficient you enter only over that part of the exchanger containing sensible liquid cooling and in two-phase region.

Hot sensible vapor coefficient Defines a value for hot fluid sensible vapor heat transfer coefficient. Your entered value overrides any X ace-calculated value. Base your entered value on hot fluid's surface area. Required:

No

Units:

SI: W/m² °C

Default:

None

US: Btu/hr ft² °F


X ace applies heat transfer coefficient you enter only over that part of exchanger containing sensible vapor cooling and in two-phase region. Page 94



Input Panels

Condensing coefficient Defines a value for hot fluid phase-change heat transfer coefficient. Your entered value overrides any value calculated by X ace. Base your entered value on hot fluid's surface area. Required:

No

Units:

SI: W/m² °C

Default:

None

US: Btu/hr ft² °F


X ace applies heat transfer coefficient you enter only over that part of exchanger where condensation occurs.

Cold sensible liquid coefficient Defines a value for cold fluid sensible liquid heat transfer coefficient. Your entered value overrides any value calculated by X ace. Base your entered value on cold fluid's surface area. Required:

No

Units:

SI: W/m² °C

Default:

None

US: Btu/hr ft² °F


X ace applies heat transfer coefficient you enter only over that part of exchanger where boiling occurs.

Cold sensible vapor coefficient Defines a value for cold fluid sensible vapor heat transfer coefficient. Your entered value overrides any value calculated by X ace. Base your entered value on cold fluid's surface area. Required:

No

Units:

SI: W/m² °C

Default:

None

US: Btu/hr ft² °F


The entered heat transfer coefficient is applied only over that part of exchanger containing sensible vapor heating and in two-phase region.

Boiling coefficient Defines a value for cold fluid boiling heat transfer coefficient. Your entered value overrides any value calculated by X ace. Base your entered value on cold fluid's surface area. Required:

No

Units:

SI: W/m² °C

Default:

None

US: Btu/hr ft² °F


X ace applies heat transfer coefficient you enter only over that part of exchanger where boiling occurs.


Page 95

Input Panels


Critical heat flux Specifies local heat flux at which X ace switches to film boiling heat transfer correlation. Required:

No

Units:

SI: W/m² °C

Default:

Calculated by program

US: Btu/hr ft² °F


Critical heat flux is the maximum heat flux at which nucleate boiling can occur. If the temperature difference driving force increases, the boiling mechanism moves into a transition and then a film-boiling regime. The figure below illustrates the typical shape of the boiling curve. As the temperature driving force (difference between fluid and wall temperature) increases, the flux increases to a maximum value that is called critical heat flux . If the temperature driving force is increased beyond this point, the heat flux decreases rapidly in the transition-boiling regime. After a minimum is reached, the flux then increases monotonically in the film-boiling regime. In general, designers prefer to avoid the transition and film boiling regimes because of their decreased fluxes and dry wall conditions. However there is nothing inherently wrong with operating in the stable filmboiling regime.

Page 96



Input Panels

Typical Shape of Boiling Curve

Fraction of critical flux for film boiling Specifies fraction of program-calculated (or user-specified) critical heat flux at which X ace uses film boiling heat transfer coefficient. Required:

No

Units:

SI: W/m² °C

Default:

1 (one)

US: Btu/hr ft² °F


Hot fluid coefficient multiplier Defines a multiplier on program-calculated hot fluid heat transfer coefficient. Enter any value > 0.0. Required:

No

Units:

None

Default:

1.0

If you enter a value in this field, X ace calculates a hot fluid heat transfer coefficient and then multiplies by the entered value.

Cold fluid coefficient multiplier Defines a multiplier on program-calculated cold fluid heat transfer coefficient. Enter any value > 0.0. Required:

No

Units:

None

Default:

1.0

If you enter a value, X ace multiplies calculated or specified heat transfer coefficient by entered value. © Heat Transfer Research, Inc. All rights reserved. Confidential: For HTRI member use only.

Page 97

Input Panels


Outside friction factor multiplier Modifies program-calculated airside (outside) single-phase friction factor. You can use a friction factor multiplier to shift calculated friction factor up (>1.0, to simulate an enhancement device) or down (< 1.0, to simulate use of a drag reducer). Required:

No

Units:

None

Default:

1.0

Use this field only if you have experimental or plant data on similar units.

Tubeside friction factor multiplier Modifies program-calculated tubeside single-phase friction factor. You can use a friction factor multiplier to shift calculated friction factor up (>1.0, to simulate an enhancement device) or down (< 1.0, to simulate use of a drag reducer). Required:

No

Units:

None

Default:

1.0

Because two-phase pressure drop correlations use single-phase friction factor as a basis for two-phase pressure drop, this field also affects two-phase flow. All existing two-phase methods have been developed based on commercial pipe. Use this field only if you have experimental or plant data on similar units.

User-Defined Methods panel This panel applies specification of user-defined nucleate and film boiling curves.

Reference pressure for nucleate boiling curve Specifies pressure at which nucleate boiling curve is provided. If you enter a nucleate boiling curve, X ace uses entered equation to calculate nucleate boiling component of boiling heat transfer coefficient. If you specify this value, you must also specify constant and exponent for nucleate boiling curve to use this option. Required: Page 98



Input Panels

Units:

SI: kPa

US: psia

MKH: kgf/cm² A

Default:

None (program-calculated nucleate boiling heat transfer coefficient)

NOTE: X ace adds a convective boiling component to your equation unless you select Nucleate only, Methods panel.

Constant A for nucleate boiling curve Specifies constant A in nucleate boiling curve. The equation is

h A T

B

If you enter a nucleate boiling curve, X ace uses entered equation to calculate nucleate boiling component of boiling heat transfer coefficient. If you specify this value, you must also specify reference pressure and exponent for nucleate boiling curve to use this option. Required:

No

Units:

None

Default:

None


Exponent B for nucleate boiling curve Specifies exponent B in nucleate boiling curve. The equation is

1n VP A B T C If you enter a nucleate boiling curve, X ace uses entered equation to calculate nucleate boiling component of boiling heat transfer coefficient. If you specify this value, you must also specify reference pressure and constant for nucleate boiling curve to use this option. Required:

No

Units:

None

Default:

None


Add non-nucleate boiling components to this curve This checkbox tells X ace whether to add additional boiling components (e.g., convective) to user-defined nucleate boiling curve. If box is checked

X ace uses defined curve for nucleate boiling coefficient calculations, but adds additional boiling components for boiling heat transfer coefficient calculations.

If box is not checked X ace uses defined curve only for direct boiling heat transfer coefficient calculations © Heat Transfer Research, Inc. All rights reserved. Confidential: For HTRI member use only.

Page 99

Input Panels


Required:

No

Units:

None

Default:

Checked

NOTE: X ace ignores this field unless you specify a nucleate boiling curve.

Constant A for film boiling curve Specifies constant A in film-boiling curve. The equation is

h A T

B

If you enter a film-boiling curve, X ace uses entered equation to calculate film boiling heat transfer coefficient when program determines that exchanger contains increments in film-boiling regime. If you specify this value, you must also specify exponent for film-boiling curve to use this option. Required:

No

Units:

None

Default:

None

Exponent B for film boiling curve Specifies exponent B in film-boiling curve. The equation is

h A T

B

If you enter a film-boiling curve, X ace uses entered equation to calculate film boiling heat transfer coefficient when X ace determines that exchanger contains increments in film-boiling regime. If you specify this value, you must also specify constant for film-boiling curve to use this option. Required:

No

Units:

None

Default:

None

Page 100



Input Panels

Convergence panel This panel sets convergence tolerances that you wish to apply to a case.

Overall pressure drop Controls exit quality calculated in heat exchanger. X ace iterates until the calculated pressure drop in the exchanger is within this tolerance of the value in the previous iteration. Required:

Yes

Units:

None

Default:

20% of the calculated pressure drop

For moderate pressure, the calculated results are not a strong function of this value; vacuum exchangers may show a stronger trend with convergence tolerance.

Overall heat transfer Sets tolerance for heat transfer. Incrementally, X ace iterates until the standard deviation of the calculated and assumed heat duty in increment in each increment is within this tolerance. Smaller numbers indicate a more tightly converged solution. Required:

Yes

Units:

None

Default:

1%

Use your engineering judgment when you use this field. Increasing the tolerance allows the case to run faster, but answers may not be valid. If you alter this value, check duty ratio in the Output 3D Profiles plot, Graphs tab, after you run case to assure convergence.

Unknown duty Loosens or tightens convergence tolerance (by increasing or decreasing number). The unknown duty tolerance is used in simulation cases when determining the performance of the exchanger. © Heat Transfer Research, Inc. All rights reserved. Confidential: For HTRI member use only.

Page 101

Input Panels


Required:

Yes

Units:

None

Default:

1% of calculated heat duty

Consider increasing the value in this field if case does not converge.

Local wall temperature Controls tolerance that X ace uses when calculating local wall temperature. Required:

Yes

Units:

None

Default:

0.1% of local wall temperature

The local wall temperature convergence is the innermost loop of the software, so that increasing this value can significantly impact run time. The only way to assure that final results are sufficiently converged is through trial-and-error: you must run many different values.

CAPE-OPEN panel When you launch X changer Suite from a process simulator by editing a CAPE-OPEN unit operation, the Control panel group has an additional panel. This panel contains fields that enable you to control the execution of the unit operation during process flowsheet execution.

Maximum number of pressure-properties trials Specifies how many times X changer Suite regenerates physical properties during execution of a CAPEOPEN unit operation. When the exchanger is solved, the calculated process conditions may be outside the range of the fluid physical properties. If so, the program adjusts the pressure and/or temperature range and regenerates fluid physical properties. Required:

Yes

Units:

None

Default:

10

Page 102



Input Panels

If the calculated process conditions are outside the range of the generated properties after the specified number of iterations, the CAPE-OPEN block returns an execution failure to the process simulator. * This version of the panel is visible only when you launch X changer Suite from a CAPE-OPEN unit embedded in a process simulator.

Relative pressure tolerance Sets relative pressure tolerance used to determine if fluid physical properties should be regenerated. If the calculated outlet pressure is outside the range of currently generated properties by more than the specified tolerance, properties are regenerated. The calculation is PRF = (CurrentEndingPressure – OutletPressure) / InletPressure If the absolute value of PRF is more than the specified tolerance, the properties are regenerated. Required:

Yes

Units:

None

Default:

0.01

You can also specify an absolute pressure tolerance on this same panel. X changer Suite uses the most limiting value to determine regeneration of properties. * This version of the panel is visible only when you launch X changer Suite from a CAPE-OPEN unit embedded in a process simulator.

Absolute pressure tolerance Sets pressure tolerance used to determine if fluid physical properties should be regenerated. If the calculated outlet pressure is outside the range of currently generated properties by more than the specified tolerance, properties are regenerated. Required:

Yes

Units:

SI

US

MKH

kPa

psi

kgf/cm2

Default:

6.895 kPa (1 psi)

You can also specify a relative pressure tolerance on this same panel. The most limiting value is used to determine regeneration of properties. * This version of the panel is visible only when you launch X changer Suite from a CAPE-OPEN unit embedded in a process simulator.

Absolute temperature tolerance Sets temperature tolerance used to determine if fluid physical properties should be regenerated. If calculated outlet temperature is outside the range of currently generated properties by more than the specified tolerance, properties are regenerated.


Page 103

Input Panels


Required:

Yes

Units:

SI

US

C

F

Default:

MKH C

6.895 kPa (1 psi)

* This version of the panel is visible only when you launch X changer Suite from a CAPE-OPEN unit embedded in a process simulator.

Default number of pressure sets Specifies how many pressure sets should be generated when fluid physical properties are calculated. The program calculates properties as P = (Starting Pressure – Ending Pressure)/(Number of pressure sets -1) The program calculates properties at increments of P between starting and ending pressures. Auto

program decides on number of pressure sets based on process conditions See Note below

1-12

generates specified number of pressure sets

This field sets the default value only. The actual number of pressure sets generated can be directly specified on a per fluid basis on the Fluid Properties panels. Required:

Yes

Units:

None

Default:

Auto

Logic for determining the number of pressure sets is described in Selecting Temperature and Pressure Grid Points * This version of the panel is visible only when you launch X changer Suite from a CAPE-OPEN unit embedded in a process simulator.



1-12


Page 104



Input Panels


Yes

Units:

None

Default:

Auto

Logic for determining the number of pressure sets is described in Selecting Temperature and Pressure Grid Points * This version of the panel is visible only when you launch X changer Suite from a CAPE-OPEN unit embedded in a process simulator.



1-12



Yes

Units:

None

Default:

Auto

Logic for determining the number of pressure sets is described in Selecting Temperature and Pressure Grid Points This version of the panel is visible only when you launch X changer Suite from a CAPE-OPEN unit embedded in a process simulator.


Page 105

Output Reports


X ace Output Reports X ace produces several types of output reports. With certain exceptions noted in their descriptions, reports are available either in wide (120-column) or narrow (80-column) formats. Output Summary Output Summary for Multiple Services Run Log Data Check Messages Runtime Messages Final Results Outside Monitor Tubeside Monitor Temperature Monitor Pressure Drop Monitor API 661 Spec Sheet Property Monitor Stream Properties Maldistribution Monitor Input Reprint Headings for all report pages include 4 lines of information. These headings differ according to the type of case you run, but remain the same within a report.

Report Heading Example Line 1: X ace, version, date, time, and page number Line 2: Problem Line 3: Case Line 4: Exchanger Description

Page 106



Output Reports

Output Report Line 4 This run description is built from the following choices: Design

Horizontal

Natural Draft Air-cooler

Rating

Vertical

Forced Draft Air-cooler

Simulation

Inclined

Economizer Air-cooled heat exchanger

Output Summary After you run a case, the Output Summary appears, showing major aspects of your results. Make quick go/no go decisions on your exchanger designs with this information. The tree on the left of the X ace window shows all reports available to you.


Page 107

Output Reports


Process Conditions Printed headings without comments are self-explanatory

Printed Heading

Comments

Fluid name

A name appears for both Airside and Tubeside fluids.

Fluid condition

Indicates whether fluid is boiling or condensing, liquid or vapor.

Total flow rate Weight fraction vapor Temperature, in/out Skin temperature, min/max

Printed for both sides of exchanger, values are at surface between fluid and tube wall or fluid and outside of fouling layer, if present.

Pressure, inlet/outlet Pressure drop, total/allowed

Airside (outside) pressure drop and allowable pressure drop as entered. Values are in Pa (in. H2O). Tube pressure drop Includes effects caused by nozzles, turnarounds, tube entrance, and tube exit, as well as frictional pressure drop Total – measured inlet to outlet Total pressure drop is calculated pressure drop for entire exchanger, includes bundle pressure drop and any effects caused by ground clearance, fan rings, fan guards, steam coils, and louvers. It is static pressure drop only, and does not include velocity pressure effects. Allowed – value entered on Process panel

Velocity, Midpoint

Velocity at midpoint of stream path. Velocities for condensing and boiling are based on two-phase properties.

In/Out

Tubeside only. Velocities for condensing and boiling are based on two-phase properties.

Heat transfer safety factor Fouling resistance

Referenced to its own surface as input. If multiple tube types are in bundle, this value takes into account tube geometry differences.

Exchanger Performance Printed headings without comments are self-explanatory

Printed Heading

Comments

Outside film coefficient

Outside extended coefficient

Tubeside film coefficient

Tubeside film coefficient film coefficient (referenced to its own surface area) X ace, a fully incremental program, does not use overall heat transfer coefficients or temperature differences; any of these values are integrated averages over all increments, printed for reference only. X ace does NOT use these values when calculating exchanger performance.

Clean coefficient

Assumes no fouling

Hot regime Cold regime

Page 108



Output Reports

Printed Heading

Comments

EMTD

Effective mean temperature difference Although X ace can obtain total heat transferred in exchanger and total surface area directly, the program must average effective overall heat transfer coefficient and effective overall mean temperature difference over all increments.

Duty

Based on process conditions X ace uses this calculated duty when calculating heat transfer coefficients and process temperatures.

Actual U

Actual heat transf er coefficient X ace integrates all incremental overall heat transfer coefficients.

Required U

Required heat transfer coefficient This value is back-calculated based on calculated heat duty and effective mean temperature.

Area

Extended area/unit

Overdesign

Theoretical indication of feasibility of exchanger design Overdesign indicates the amount of extra area the design has for indicated process conditions. A negative value for overdesign indicates that the exchanger is too small for the specified process. A value near zero indicates a close match of process conditions and exchanger area design.

Unit Geometry Areas on this report are net effective areas, not total ar ea. X ace subtracts length in tubesheets, length blocked by support strips, and any unheated or unfinned lengths specified before it calculat es heat transfer ar ea. Printed headings without comments are self-explanatory.

Printed Heading

Comments

Bay in parallel per unit


Bundles in parallel per bay


Extended area

Extended area per unit

Bare area

Bare area per unit

Bundle width

Inside side frames, including clearance from first tube to wall

Number of nozzles


Diameter


Velocity

Two-phase cases use homogeneous mixed density for nozzle velocity calculations

Nozzle R-V-SQ


Pressure drop


Page 109

Output Reports


Tube Geometry If the exchanger has more than one ty pe of tube, this information is for the t ube type of the top row in the exc hanger. Printed headings without comments are self-explanatory

Printed Heading

Comments

Tube type

- plain - high-fin - low-fin - stud-fin

Tube OD

Tube outside diameter

Tube ID


Length

Tube straight length

Area ratio (out/in) Layout

Prints as Staggered or Inline

Tran pitch

Transverse pitch

Long Pitch

Longitudinal pitch

Number of passes


Number of rows Tubeside only. Velocities for condensing and boiling are based on two-phase properties.

Tubecount

Total for all rows in bundle

Tubecount Odd/Even

Based on the tube type of the first row

Tube material

Fan Geometry Printed headings without comments are self-explanatory

Printed Heading

Comments

No./bay

Number of fans per bay – Fans are assumed to be down length of exchanger in bundle.

Fan ring type Diameter Ratio, Fan/bundle face area Fan power Efficiency

Page 110



Output Reports

Fin Geometry Printed headings without comments are self-explanatory

Printed Heading

Comments

Type

- none - round - segmented round - rectangular - round studs

Fins/length Fin root

Fin root diameter

Height Base thickness

Fin thickness at base

Over fin

Over fin diameter

Efficiency

Averaged value over entir e exchanger X ace actually calculates a separate fin efficiency for each increment in exchanger based on local performance

Area ratio (fin/bare)

For finned portion of t he tube only Not an overall exchanger area ratio and thus does not include unfinned length

Material

Airside Velocities Velocities appear for both actual and st andard conditions (dry air at 21.11 °C (70 °F) and 101.325 kPa (14.696 psia) , which results in an air density of 1.1997 kg/m³ (0.075 lb/ft³)). Velocities and volumetric flow rates are at exchanger inlet. For economizers, standard conditions are blank. For bundles inservice, the value displayed is the maximum value from the available bundles. Printed headings without comments are self-explanatory

Printed Heading

Comments

Face

Velocity approaching outside inlet of exchanger

Maximum

Based on minimum flow area in exchanger, calculated using inlet outside fluid (air) physical properties

Flow

Volumetric flow

Velocity pressure

Velocity pressure effect

Static pressure

X ace uses static pressure drop to calculate motor power requirements


Page 111

Output Reports


Thermal Resistance Printed headings without comments are self-explanatory

Printed Heading

Comments

Air

For economizers, percent of ther mal resistance due to out side coefficient

Tube Fouling

Fin root diameter

Metal

Includes fin resistance

Bond

You must enter a value for fin bond resistance; X ace does not calculate it. In new tubes, bond resistance is usually zero. For tension-wound tubes at elevated temperatures (typically above 176 °C (350 °F)), fin can separate from tube, resulting in marked decrease in heat transfer.

Airside Pressure Drop Airside (outside) press ure drops are printed as a percent of total static pr essure drop in bundle. Print ed headings without comments are self-explanatory.

Printed Heading

Comments

Bundle

Across bundle

Ground clearance Fan ring

Function of Fan Ring Type entered on Fans panel

Fan guard Fan area blockage Louvers Hail screen Steam coil

Page 112



Output Reports

Output Summary for Multiple Services The output for X ace multiple services is a two-page report detailing the operation of the entire bay.


Page 113

Output Reports

Page 114




Output Reports

Overall Exchanger Performance Printed Heading

Comments

Maximum overdesign

maximum overdesign for bundles in bay

Minimum overdesig

minimum overdesign for the bundles in the bay

Heat Duty

total heat duty for all bundles in the bay

Outside Process Conditions For the entire bay, these conditions are calculated using an enthalpy balance. For calculating these values, the outside fluid is assumed to be air. Printed headings without comments are self-explanatory.

Printed Heading

Comments

Fluid name

A name appears if the unit is an economizer

Fluid condition

Indicates whether outside fluid is boiling or condensing, liquid or vapor

Total flow rate Weight fraction vapor, In/Out Temperature, In/Out

Outlet temperature is enthalpy balanced by mixing the outlet stream from each bundle

Skin temperature, Min/Max

Prints for both sides of exchanger, values are at surface between fluid and tube wall or fluid and outside of fouling layer, if present.

Pressure, Inlet/Outlet Pressure drop, Total/Allow

Midpoint velocity

Airside (outside) pres sure drop as entered. Values are in Pa (i n. H2O).

Total

Averaged over bundles. Total pressure drop is calculated pressure drop for entire exchanger, includes bundle pressure drop and any effects caused by ground clearance, fan rings, fan guards, steam coils, and louvers. It is static pressure drop only, and does not include velocity pressure effects.

Allow

Value entered on Process panel


Heat transfer safety factor Fouling


Unit Geometry Printed headings without comments are self-explanatory.

Printed Heading

Comments

Bays in parallel per unit

bays are identical

Bundles parallel per bay © Heat Transfer Research, Inc. All rights reserved. Confidential: For HTRI member use only.

Page 115

Output Reports


Printed Heading

Comments

Total extended area

for entire bay

Total bare area

for entire bay

Fan Geometry Printed headings without comments are self-explanatory.

Printed Heading

Comments

No/bay

Fans are assumed to be down length of exchanger in bundle

Fan ring type Diameter Ratio, Fan/bundle face area Driver power Tip clearance Efficiency

Maximum Airside Velocities Velocities appear for both actual and standard conditions (dry air at 21.11 °C (70 °F) and 101.325 kPa (14.696 psia), which results in an air density of 1.1997 kg/m³ (0.075 lb/ft³)). Velocities and volumetric flow rates are at exchanger inlet. For economizers, standard conditions are blank. Printed headings without comments are selfexplanatory.

Printed Heading

Comments

Face

velocity approaching outside inlet of exchanger

Maximum

based on minimum flow area in bay, calculated using inlet outside fluid (air) physical properties

Flow Velocity pressure

calculated for bay

Bundle pressure drop

average for all bundles

Airside Pressure Drop % Airside (outside) pressure drops are printed as a percent of total static pressure drop in bundle. Bundle pressure loss and steam coil pressure loss are averaged per bundle. Fan ring, fan guard, ground clearance and other obstruction pressure drops are per bay. Printed headings without comments are self-explanatory.

Printed Heading

Comments

Ground clearance Fan ring

Page 116

function of Fan Ring Type entered on Fans panel © Heat Transfer Research, Inc. All rights reserved. Confidential: For HTRI member use only.


Printed Heading

Output Reports

Comments

Fan guard Louvers Fan area blockage Hail screen

Exchanger Weights Unless a material is explicitly specified in the program (tubes and fins), X ace uses stainless steel properties for weight calculations. Printed headings without comments are self-explanatory.

Printed Heading

Comments

Weight/bundle Structure weight

total weight of structure including all bays in the unit

Total weight Dry

Total weight of entire unit including structure weight, ladder/walkway weight, and all bundles in the unit.

Wet

Total dry weight plus the weight of the header and tube volume filled with water at the exchanger inlet temperature

Ladder/walkway weight

Estimated weight of ladders and walkways in the unit including all ladders and walkways assumed

Fan Manufacturers Displays only if one or more of the available fan manufacturer ratings are requested. Printed headings without comments are self-explanatory.

Printed Heading

Comments

Manufacturer

Name of manufacturer recommending fan

Type

Manufacturer fan description

Fan size

Fan diameter

Number of blades Blade angle Noise PWL Total efficiency Static efficiency Fan speed Tip speed Driver power


Page 117

Output Reports


Bundle Summary Values are printed for each bundle in services in a column format. Full reports are provided for each bundle in addition to this reference view

Run Log When you run a case from the X changer Suite GUI, a run log indicates the status of the calculations. This log disappears when X ace completes running the case.

The Run Log report shows you what displayed in the box while X ace ran the rating or simulation case.

Data Check Messages Before running a case, X ace performs a detailed check of input data to verify that they are complete and consistent. When X ace encounters conditions warranting Fatal, Warning, or Informative messages, it displays data check messages. If you get any of these messages, check your input carefully. Message

Occurs if

Fatal

You provide invalid or inconsistent input. X ace catches most of these errors as you enter data. However, some inconsistencies cannot be determined until you run your case. The message identifies data item causing problem and suggests corrective action, if any is possible.

Page 118



Warning

Output Reports

X ace detects a problem in input data. Warning messages indicate the nature of problem and describe corrective action.

Informative

Your input is unusual.

Change level of warning that appears by selecting from View menu, Data Check Messages secondary menu. This setting is dynamic: change level before or after you run your case, and X ace’s display updates messages to reflect your current choice.

Runtime Messages Runtime Messages follow Data Check Messages when problems occur while X ace is processing a case. FATAL messages appear first, followed by WARNING messages and INFORMATIVE messages. If your case has any Runtime Messages, an identifying banner heading appears on Final Results first page. To change the level of warning that appears, select another option from View menu, Runtime Messages secondary menu. This setting is dynamic: change level before or after you run your case, and X ace’s display updates messages to reflect your current choice. Message Fatal

Occurs if X ace encounters problems that lead to incorrect results. Fatal errors are caused by loop-type calculations that do not converge, impossible geometry situations, or some specifications that prove to be in error once calculation starts. Usually, only one message of this type prints because X ace terminates when it encounters a fatal error.

NOTE

Results printed when a Fatal error is found are not a solution.

Warning

X ace encounters unusual, limiting, or undefined situations that need to be brought to your attention.

Informative

X ace encounters unusual data or results. These messages can also mean that a method being used is not totally reliable in area in which it is being applied. Consider using a different geometry, such as finned tubes.


Page 119

Output Reports


Final Results This output contains the main results of a case. In most cases, all information you need for surveying the rating is included here. This report can appear in regular or wide format. Select Wide reports, View menu, to see Final Results in wide format.

Page 120



Output Reports


Page 121

Output Reports


Process Data Printed headings without comments are self-explanatory

Printed Heading

Comments

Fluid name

A name appears for both Airside and Tubeside fluids.

Fluid condition

Indicates whether fluid is boiling or condensing, liquid or vapor.

Total flow rate Weight fraction vapor Temperature, in/out Skin temperature, min/max

Printed for both sides of exchanger, values are at surface between fluid and tube wall or fluid and outside of fouling layer, if present.

Pressure, inlet/outlet Pressure drop, total/allowed

Airside (outside) pres sure drop and allowable pressur e drop as entered. V alues are in Pa (in. H2O).

Total – measured inlet to outlet

Page 122



Printed Heading

Output Reports

Comments Total pressure drop is calculated pressure drop for entire exchanger, includes bundle pressure drop and any effects caused by ground clearance, fan rings, fan guards, steam coils, and louvers. It is static pressure drop only, and does not include velocity pressure effects.

Allowed – value entered on Process panel Tube pressure drop, total/allowed

Includes effects caused by nozzles, turnarounds, tube entrance, and tube exit, as well as frictional pressure drop.

Velocity, Midpoint


In/Out

Tubeside only. Velocities for condensing and boiling are based on two-phase properties.

Film Coefficient, Bare/Extended

Bare coefficient, for airside, is reference value for comparison only; X ace does not use it in any calculations. Extended film coefficient, for tubeside, is referenced to its own surface area. X ace, a fully incremental program, does not use overall heat transfer coefficients or temperature differences; any of these values are integrated averages over all increments, printed for reference only. X ace does NOT use these values when calculating exchanger performance.

Heat transfer safety factor Fouling resistance


Average Coefficients X ace is a fully incremental program. As such, it does not need or use overall heat transfer coefficients. Average coefficients are calculated for comparison purposes based on incremental values. To calculate average overall coefficients from incremental values, X ace first calculates the overall average heat transfer coefficient, U avg , as

U avg

1 A tot

i 1, n

U i dAi

Once the average overall heat transfer coefficient is calculated, individual overall average film heat transfer coefficients can be calculated as follows: 1

1

h 1 avg

U avg A tot

1

1

h 2 av

U avg A tot

U i dAi i 1, n

h1i U i dAi

i 1, n

h2i


Page 123

Output Reports


where Atot

total area in heat exchanger

dAi

area of increment i

h 1 avg

apparent overall film coefficient on side 1 of exchanger (line 14)

h1

incremental heat transfer film coefficient on side 1 of exchanger

i

h2

avg

h2

i

apparent overall film coefficient on side 2 of exchanger (line 14) incremental heat transfer film coefficient on side 2 of exchanger

n

number of increments in heat exchanger In X ace, this number is between 10 and 14400, depending on case being run. apparent overall average heat transfer coefficient for exchanger (line 18 below)

U avg

Overall values can also be used in the following context, which shows the relationship between averaged heat transfer coefficients: 1

1

U avg

h 1 avg

RTF

RTW

RFN

1 h 2 avg

where (RTF)

total fouling resistance

(RFN)

fin resistance

(RTW)

tube wall resistance

You can use any area in these integrations as long as you are consistent. In X ace, all values are referenced to the extended surface area of the outside of the tube. As with heat transfer coefficients, the effective mean temperature difference printed on line 20 is averaged from all incremental values. The equations used to average these values are as follows: 1

1

T avg

Qtot

dQi i 1, n

T mi

where T avg Qi T mi

Page 124

effective mean temperature difference (EMTD) heat duty in an increment log mean temperature difference an increment

i

increment number

n

number of increments

Qtot

total heat duty in exchanger



Output Reports

Overall Performance Data Printed headings without comments are self-explanatory.

Printed Heading Overall Coef, Design/Clean/Actual

Comments Design: back-calculated based on calculated heat duty and effective mean temperature (lines 19 and 20). Clean: assumes no fouling. Actual: X ace integrates all incremental overall heat transfer coefficients. Although X ace can obtain total heat transferred in exchanger and total surface area directly, the program must average effective overall heat transfer coefficient and effective overall mean temperature difference over all increments.

Heat Duty, Calculated/Specified

Effective Overall Temperature Difference

Based on process conditions, these values are input. X ace uses specified duty to determine unit overdesign and calculated duty when calculating heat transfer coefficients and process temperatures. Although X ace can obtain total heat transferred in exchanger and total surface area directly, the program must average effective overall heat transfer coefficient and effective overall mean temperature difference over all increments.

NOTE

X ace uses incremental temperature differences when calculating performance of exchanger. The value printed on this line is for reference only. It is not used in any internal calculations.

Messages Printed headings without comments are self-explanatory.

Printed Heading (none)

Comments

These lines indicate that fatal errors or warning messages have occurred. If a message is indicated on these lines, check Runtime Messages. If these lines are blank, the case has no Runtime Messages.

Unit and Bundle Construction Information Areas on this report are net effective areas, not total ar ea. X ace subtracts length in tubesheets, length blocked by support strips, and any unheated or unfinne d lengths specified before it calculates heat transfer area. Printed headings without comments are self-explanatory.

Printed Heading

Comments

Bay in parallel/unit Bundles in parallel/bay Extended area/unit Bare area/unit

Based on fin root diameter

Extended area/bundle Bare area/bundle Number of tubepasses/rows © Heat Transfer Research, Inc. All rights reserved. Confidential: For HTRI member use only.

Page 125

Output Reports


Printed Heading

Comments

Number of tubes/bundle

Total for all rows in bundle

Tube count odd/even rows

Based on first tube type entered

Edge seals

If present, X ace treats bundle as an ideal tube bank without flow bypassing

Bundle width

Inside side frames, including clearance from first tube to wall

Fan guard

If fan guard, louvers, steam coil, and/or hail screen present in unit, X ace calculates additional pressure loss and reports additional pressure drop as Other on Final Results.

Clearance

Clearance from outside-most tube in bundle to exchanger wall For finned tubes, value is from edge of fin to wall.

Louvers Header Box

If present, X ace calculates additional pressure drop based on fully open louvers depth

If program-calculated, based on simplified version of ASME code

-plate thickness -tubesheet thickness

Steam coil

If present, X ace calculates additional pressure drop The following geometry is assumed for steam coils: Root diameter 25.4 mm (1 in.) Aluminum fins, 433 fins/m (11 fins/ in.) Fin height 15.748 mm (0.62 in.) Tube pitch of 63.5 mm (2.5 in.) Calculations assume steam coil is turned off: air inlet temperature is not changed based on presence of coil.

Hail screen

If present, X ace calculates additional pressure drop Presence of plate does not influence calculated heat transfer performance

Plenum type

Does not influence calculated performance of exchanger

Tube support information – Number – Width Orientation (from horizontal)

Zero for horizontal tubes.

Weight/bundle

Calculated weight of one bundle

Structure weight

Total weight of structure including all bays in the unit

Total weight

Total weight of entire unit including structure weight, ladder/walkway weight, and all bundles in the unit

Ladder/walkway weight

Estimated weight of ladders and walkways in the unit including all ladders and walkways assumed

Cost factor

Relative cost factor provided by Hudson, used for comparing different designs and not actual cost of the exchanger. The cost factor is a function of bare area, tube metal cost (assuming anything that is not carbon steel is stainless), design pressure, and tube

Page 126



Printed Heading

Output Reports

Comments length.

Tube Information If the exchanger has more than one t ype of tube, this section appears on page t wo in a tabular format . Printed headings without comments are self-explanatory.

Printed Heading

Comments

Straight length Unfinned length

As entered on Bundle panel, Geometry group

Layout

Prints as Staggered or Inline

Transverse pitch Longitudinal pitch Tube form

Straight or U-tube

Outside diameter Inside diameter

Inside any specified fouling layer thickness

Area ratio (Out /In) Over fin diameter Tube type

plain high-fin low-fin stud-fin

Unheated length

Includes tubesheet, length covered by support strips, and any unheated length entered

Area ratio (fin/bare)

For finned portion of the tube only It is not an overall exchanger area ratio and thus does not include unfinned length.

Number of fins Fin root diameter Fin height Fin thickness at base Fin thickness at tip Fin type

none round segmented round rectangular round studs

Fin efficiency

Averaged value over entire exchanger X ace actually calculates a separate fin efficiency for each increment in exchanger based on local performance.

Tube material © Heat Transfer Research, Inc. All rights reserved. Confidential: For HTRI member use only.

Page 127

Output Reports


Printed Heading

Comments

Fin material

Inlet Airside Velocities If you use regular-sized format, this information appears on second page. Velocities appear for both actual and standard conditions (dr y air at 21.11 °C (70 °F) and 101.325 kPa (14.696 psia), which results in an air densit y of 1.1997 kg/m³ (0.075 lb/ft³)). Velocities and volumetric flow rates are at exchanger inlet. For economizers, standard condit ions are blank. Printed headings without comments are self-e xplanatory.

Printed Heading

Comments

Face velocity

Velocity approaching outside inlet of exchanger

Maximum velocity

Based on minimum flow area in exchanger, calculated using inlet outside fluid (air) physical properties

Volumetric flow Maximum mass velocity Air humidity

Relative humidity as s pecified on Optional panel, Geometry group

Fan Description and Fan Power This section remains blank for natural draft or heat recovery systems. Printed headings without comments are self explanatory.

Printed Heading Number of fans/bay

Comments Fans are assumed to be down length of exchanger in bundle.

Diameter Tip clearance

For reference only; not used in any internal calculations

Ratio, fan area/bay face area Fan ring type Percent open area – in fan guard – in hail screen

X ace assumes fan guard and hail screen (if specified) are made of 2-in. wire cloth similar to chain-link fencing material.

Ratio, ground clearance/fan diameter Percent blockage, other obstruction Static pressure/velocity pressure

Calculated static pressure drop and velocity pressure effect. X ace uses static pressure drop to calculate motor power requirements.

Fan and drive efficiency Motor power per fan – design air temperature – minimum air temperatu re Ambient temperature maximum/minimum

Page 128

X ace calculates this value based on specified winter ambient temperature. X ace reprints values you entered, using minimum (min) value to determine winter fan power. Maximum (max) value is not used for any internal calculations. © Heat Transfer Research, Inc. All rights reserved. Confidential: For HTRI member use only.


Output Reports

Two-Phase Parameters Printed headings without comments are self-explanatory.

Printed Heading

Comments

Method

Condensation calculation method used by X ace, set on Methods panel

RPM (HTRI Resistance Proration Method) LITERATURE (Uncorrected Ward-Silver-Bell method) CPM (Composition Profile Method) REFLUX (Reflux condensation) Inlet, Center, Outlet

Controlling condensation mode at inlet, center, and outlet of condensing fluid path Tubeside horizontal condensation GRAVITY TRANS (Transition) ANN-MIST (Annular- mist) SHEAR Tubeside vertical condensation G C LAM (Gravity-controlled laminar) G C TRANS (Gravity-controlled transition) G C TURB (Gravity-controlled turbulent) TRANS (Transition) ANN-MIST (Annular- mist) SHEAR Outside condensation GRAVITY TRANS (Transition) ANN-MIST (Annular- mist) SHEAR Boiling CONV (Convective boiling) NUCL (Nucleate boiling) FILM (Film boiling) MIST (Mist flow boiling) SENS LIQ (Sensible liquid) SENS GAS (Sensible vapor) FLOW (Flow boiling – combination of nucleate/convective) SUBCOOL (Subcooled boiling) F/M TRAN (Transition between mist and flow boiling) TRAN (Transition between flow and film boiling)

Mix F

Mixing factor for condensation The average correction to pure component condensing heat transfer coefficient to account for mixture effects. This value is printed for reference only; X ace does not use it internally.

Heat Transfer and Pressure Drop Parameters Printed headings without comments are self-explanatory. © Heat Transfer Research, Inc. All rights reserved. Confidential: For HTRI member use only.

Page 129

Output Reports


Printed Heading Midpoint j-factor Heat transfer

For airside only, value is at geometric middle of bundle. Wall Corr

Row Corr Midpoint f-factor Pressure drop

Comments

Correction for heat transfer at exchanger’s geometric middle For airside only, value is correction to outside heat transfer coefficient for bundles with fewer than four rows. Single-phase fluids only

Wall Corr

Row Corr Reynolds number Inlet

Pressure drop correction caused by fluid viscosity at wall. A value, at exchanger’s geometric middle, appears for single-phase fluids only. Airside fluid only, correction for bundles with fewer than four rows Based on two-phase physical properties for phase-change fluids

Midpoint Outlet Fouling layer thickness Input minimum velocity

For reference only, if velocity falls below this user-input value at any point in exchanger, X ace issues warning.

Input maximum velocity

For reference only, if velocity exceeds this user-input value at any point in exchanger, X ace issues warning.

Input minimum wall temperature

For reference only, if wall temperature falls below this user-input value at any point in exchanger, X ace issues warning.

Input maximum wall temperature

For reference only, if wall temperature exceeds this user-input value at any point in exchanger, X ace issues warning.

Page 130



Output Reports

Thermal Resistance Printed headings without comments are self-explanatory.

Printed Heading Air

Comments For economizers, per cent of thermal resistance due to out side coefficient

Tube Fouling Metal

Includes fin resistance

Bond

You must enter a value for fin bond resistance; X ace does not calculate it. In new tubes, bond resistance is usually zero. For tension-wound tubes at elevated temperatures (typically above 176 °C (350 °F)), fin can separate from tube, resulting in marked decrease in heat transfer.

Overdesign

If negative, represents percent under design This value is based on specified duty if input, on calculated duty if duty not input. Overdesign is calculated as follows: % Over design = 100(Uo /Ureq –1)

Airside Pressure Drop The airside (outside) pressure drops are printed as a percent of total static pres sure drop in bundle. Printed headings without comments are self-explanatory.

Printed Heading

Comments

Across bundle Fan ring

Function of Fan Ring Type entered on Fans panel

Fan guard Ground clear. Other obstacles

Includes hail screen pressure drop

Steam coil Louvers

Tube Nozzle You can specify a second nozzle at outlet for liquid; information for this second nozzle prints only when one is present. Printed headings without comments are self-explanatory.

Printed Heading

Comments

Number of nozzles Diameter Velocity


Nozzle R-V-SQ


Pressure drop


Page 131

Output Reports


Mean Metal Temperatures This section lists mean tube metal temper atures for each tubepass in exchanger. These temperat ures differ from wall temperatures reported in increment al monitors. Values in this section are metal surface t emperatures inside any fouling layer. Wall temperatures reported on incremental monitors are surface temperature outside any fouling layer. The temperatures reported are length-averaged temperatures ofall tubes in each row that are in indicated tube pass.

Printed Heading Tube row

Comments Reported for each row in exchanger Row 1 is first row that outside fluid contacts. In a normal air-cooled exchanger, this is bottom row

Tubepass

Contains entry for each tubepass in exchanger Note that split-pass header designs have a separate entry for each tubepass on each row of exchanger. Values reported are averaged for each section.

Inside

Mean metal temperature on inside surface of tube for each tubepass

Outside

Mean metal temperature on outside surface of tube for each tubepass For finned tubes, temperature reported is fin root temperature.

Radial

Mean metal temperature inside tube wall This temperature is evaluated at geometric mean of wall thickness, not an average of inside and outside values.

Graphical Bundle Layout This graphic is drawn to scale. Each tube shows its tubepass number, and different shades of gray indicate tubepasses. Side seals appear if you specify them.

Bundle Information Printed headings without comments are self-explanatory.

Printed Heading

Comments

Bundle width Number of tube rows Total number of tubes

Total of all tubes in all rows

Wall clearance

Right clearance cannot be directly specified because it is based on left clearance and number of tubes if bundle width also entered

Left Right Number of tubes per pass

Total of all tubes in each pass on all rows in exchanger

Outside Monitor This monitor prints local outside heat transfer and pressure drop parameters for each increment in exchanger following flow path of outside fluid. The inlet conditions are indicated as row 0, while exit conditions are given at final row plus 1. For example, for a five-row exchanger, outside entrance conditions are reported for row 0, and outside (airside) exit conditions are reported for row 6. Page 132



Output Reports


Page 133

Output Reports


Tubeside Monitor The tubeside monitor prints local tubeside heat transfer and pressure drop parameters beginning at entrance to first tubepass and following fluid through all succeeding tubepasses.

Explanation of Items on Outside/Tubeside Incremental Monitors Heading Point number

Page 134

Description Running counter of points starting from 1 at tube inlet end of exchanger © Heat Transfer Research, Inc. All rights reserved. Confidential: For HTRI member use only.

Appears In Outside/Tube


Heading

Output Reports

Description

Appears In

Increment

Internal increment number for current point

Outside/Tube

Section

Section for current point. Sections are across the face of the tubesheet. The number of sections is based on the geometry of the exchanger.

Outside/Tube

Row

Rows are numbered from the top of the exchanger, with row 1 being the row furthest away from the outside fluid inlet.

Outside/Tube

Length from inlet

Distance from beginning of tube to midpoint of the increment

Tube

Mass fraction vapor

Weight fraction vapor at the beginning of the increment

Outside/Tube

Bulk temperature

Bulk temperature at the beginning of the increment

Outside/Tube

Skin temperature

Average wall temperature (outside fouling layer) in the increment

Outside/Tube

MTD

Mean temperature difference between outside/tubeside fluids in the increment.

Outside/Tube

Fin tip temperature

Average temperature at the tip of the fins in the increment (outside any fouling)

Outside

Pressure

Pressure at the beginning of the increment

Outside/Tube

Pressure drop

Total pressure drop across the increment. Nozzle pressure drop for first and last points on the tubeside.

Outside/Tube

Enhanced pressure drop mult

Pressure drop enhancement multiplier applied to plain tube correlation (currently only for internal micro-fins)

Tube

Friction loss

Frictional pressure drop across the increment

Outside/Tube

Static head loss

Static head pressure drop across the increment, calculated only for boiling fluids

Outside/Tube

Momentum loss

Momentum pressure drop in the increment

Outside/Tube

Can be negative (recovery) for condensing fluids. Fluid velocity

Local fluid velocity. Based on homogeneous density for two-phase flow.

Outside/Tube

Area

Total heat transfer surface area in the increment

Outside/Tube

Duty

Total duty transferred in the increment

Outside/Tube

Heat flux

Total (Duty/area) for the increment

Outside/Tube

Calculated heat flux

(Calculated duty/area) for the increment based on predicted heat transfer coefficient in the increment

Outside/Tube

Duty reported in this monitor is normalized to equal user-specified duty. At zero (0) percent overdesign, duty and calculated duties are equal. Critical heat flux

Heat flux above which film boiling is triggered in this increment

Outside/Tube

For film boiling determination, X ace uses calculated heat flux. Local overall U

Average overall heat transfer coefficient in increment

Outside/Tube

Outside/Tubeside h

Average outside or tubeside film coefficient in increment

Outside/Tube

Enhanced heat transfer mult

Heat transfer enhancement multiplier applied to plain tube correlation (currently only for internal micro-fins)

Tube

Sensible liquid h

Average sensible liquid heat transfer coefficient in the increment.

Outside/Tube

Sensible vapor h

Average sensible vapor heat transfer coefficient in the increment. Not calculated if all liquid.

Outside/Tube

Condensate film h

Average condensate film coefficient in the increment

Outside/Tube

Vapor phase h

Average effective vapor-phase heat transfer coefficient in the increment

Outside/Tube

Nucleate boiling h

Average nucleate component of overall boiling heat transfer coefficient

Outside/Tube


Page 135

Output Reports

Heading


Description

Appears In

in the increment Convective. boiling h

Average convective component of overall boiling heat transfer coefficient in the increment

Outside/Tube

Film boiling h

Average film boiling coefficient in this zone

Outside/Tube

This value is increment coefficient only if film boiling is the regime in the increment. Boiling thin film h

Average thin film boiling heat transfer coefficient in this zone

Outside/Tube

Natural convective h

Average contribution to the boiling heat transfer coefficient due to natural convection effects.

Outside/Tube

Overall Reynolds

Overall average Reynolds number in the increment, a two-phase or single-phase value depending upon fluid’s phase condition

Outside/Tube

Vapor Reynolds

Average Reynolds number of vapor as if flowing alone in the increment

Outside/Tube

Liquid Reynolds

Average Reynolds number of liquid as if flowing alone in the increment

Outside/Tube

Vapor Prandtl

Average Prandtl number for vapor phase in the increment

Outside/Tube

Liquid Prandtl

Average Prandtl number for liquid phase in the increment

Outside/Tube

Flow regime parameter

Average dimensionless paramet er used to determine flow regimes

Outside/Tube

See section B6.2 of the HTRI Design Manual for calculation equations. Condensate regime

Average condensing flow regime (e.g., Shear or Gravity) in the increment

Outside/Tube

Boiling flow regime

Flow regime for a boiling coolant (e.g. Stratified, Annular, Mist) in the increment.

Outside/Tube

Boiling mechanism

Boiling mechanism (e.g., Nucleate or Film) in the increment

Outside/Tube

Radiation coefficient

Heat transfer coefficient due to thermal radiation in the increment

Outside

Page 136



Output Reports

Temperature Monitor This monitor prints local temperature, pressure, and weight fraction vapor crosspass by crosspass, and row by row in 10 increments. According to the exchanger's geometry, all incremental values in a given crosspass are averaged to provide a manageable number of points.

Pressure Drop Monitor The Pressure Drop Monitor is designed to give tubeside process conditions as fluid exits each tube section. The outside fluid flows from bottom of bundle (represented by bottom of page) to top of bundle (represented by top of page). The flow of outside fluid is represented in this way, even if the bundle is not horizontal. The following four values appear for each tube section: Section outlet temperature Section outlet weight fraction vapor Tubeside fluid flow rate in a row of section Pressure drop through a row of section


Page 137

Output Reports

Page 138




Output Reports

API 661 Spec Sheet This specification sheet is similar to the one in API standard 661. This report always prints in the same format regardless of whether you select wide or narrow report formatting.


Page 139

Output Reports


Property Monitor This output report shows all fluid property data calculated by X ace as a function of temperature and pressure. X ace interpolates properties with respect to temperature and pressure to determine required incremental properties. The report has two pages, one for hot fluid and one for cold fluid. If you input property profiles, this report shows your specified properties. This report can have up to 6 sections, depending on fluid condition. Heat Release Profile

Miscellaneous Physical Property Factors

Vapor Properties

Vapor Mole Fraction

Liquid Properties

Liquid Mole Fraction

Lines

Physical Property Data

2–6

Temperature, pressure, and weight fraction vapor

7 – 12

Vapor properties

13 – 22

Liquid properties

23 – 25

Miscellaneous physical property factors

Page 140



Output Reports

Heat Release Profile Shows temperature, heat duty per flow rate, and weight fraction vapor for each point.

Vapor Properties Displays mixture vapor properties at each point. Vapor properties do not print for single-phase liquid fluids.

Liquid Properties Shows mixture liquid properties at each point. Liquid properties do not print for single-phase vapor fluids.

Miscellaneous Physical Property Factors Contains those factors that are completely property-dependent. These values are used by condensing and boiling correlations. Does not print if fluid is single-phase.

Vapor Mole Fraction Contains mole fractions of each component for each pressure profile in vapor phase. An all-liquid fluid does not have a Vapor Mole Fraction section.


Page 141

Output Reports


Liquid Mole Fraction Contains mole fractions of each component for each pressure profile in liquid phase. An all-vapor fluid does not have a Liquid Mole Fraction section.

Stream Properties The Stream Properties report gives information concerning calculated physical properties of hot and cold fluids. For fluids with multiple components, liquid and vapor compositions and vapor liquid equilibrium Kvalues for each component also print. X ace prints properties at inlet and outlet of exchanger. X ace takes values from the property profile, stored at 3 reference pressures. Reference pressures for the Component Physical Properties printout appear in line 5 of heading. The following 4 sets of physical property data appear on the printout:

Lines

Physical Property Data

1–4

Temperature, pressure, and weight fraction vapor

5 – 10

Mixture vapor local physical properties

11 – 18

Mixture liquid local physical properties

19 – 20

Composition and vapor-liquid equilibrium K-values

Any lines that do not apply to fluid condition (for example, liquid properties when fluid is a single-phase vapor) remain blank. Most items on Stream Properties are self-explanatory. However, 2 lines require additional explanation.

Line

Printed Heading

Comments

10

Molecular Wt.

values of vapor's molecular weight corresponding to mixture reference temperatures (Line 30) If you input properties on Hot (or Cold) Fluid Profile Properties Data Form, this line remains blank because molecular weights have not been input.

16

Molecular Wt.

values of liquid's molecular weight corresponding to mixture reference temperatures (Line 30) If you input properties on Hot (or Cold) Fluid Profile Properties Data Form, this line remains blank because molecular weights have not been input.

Page 142



Output Reports

Maldistribution Monitor This monitor depicts maldistribution in the air cooler/economizer.


Page 143

Output Reports


Input Reprint The last item on the tree view, Reports tab, shows all information used by X ace to run the case as it was input.

Page 144



Output Reports



Page 145

Test Cases


X ace Test Cases This section contains test cases for X ace. The five test cases are actual inquiries selected to provide a test for as many logic paths as possible in X ace, as well as to demonstrate the program’s use. These cases are installed in files Xace_StandardCase_1 through Xace_StandardCase_5, located in the DataFiles\Samples subdirectory of your working directory (specified when you installed HTRI X changer Suite). The default installation directory is C:\HTRI\DataFiles\Samples. 1: Single-component gas stream cooled on tube side of an air-cooled heat exchanger 2: Air-cooled heat exchanger cooling an organic liquid on tube side 3: Multicomponent hydrocarbon mixture condensed on tube side of an air-cooled heat exchanger 4: Economizer with hot flue gas stream outside tubes 5: Economizer with hot flue gas stream outside tubes Several additional cases are installed in the samples directory to illustrate other program options, although they are not discussed in this section. Xace_NaturalDraft_Example.dat, an example of a natural draft calculation using X ace Xace_ClassicDesign.dat, an example of a classical design air-cooled heat exchanger Xace_GridDesign_Example.dat, an example of an air-cooler designed using grid option

Page 146



Test Cases

Xace Test Case 1 The first test case is a horizontal forced draft air-cooled heat exchanger with a tubeside gas stream consisting primarily of methane. The case has physical properties at inlet and outlet temperatures, and individual component properties for gas at two reference temperatures.

Process Conditions Tubeside Fluid (primarily methane) Flow rate

12.6 1000 lb/hr

Inlet temperature

500 °F

Inlet pressure

485 psia

Outlet temperature

120 °F

Air Side Flow rate

36950 ft³/min

Inlet temperature

100 °F

Geometry Tube material

Carbon steel


1.0 in.


0.782 in.

Fin material

Aluminum 1100-annealed

Fin height

0.625 in.

Fin thickness

0.018 in.

Fin density

10 fins/in.

Tube length

16 ft

Number of tubes per row

28

Tube transverse pitch

2.35 in.

Tube layout

Staggered

Number of tuberows

4

Number of tubepasses

4


Page 147

Test Cases


Xace Test Case 1 Results Because of the simple geometry design, this case can be compared directly with any air-cooled heat exchanger rating program. Also, note that Test Case 1 is controlled by the tubeside heat transfer coefficient. As with most cases in which the program calculates the airside exit temperature and flow, thermal overdesign for the exchanger is near zero. The exchanger is also thermal-controlled by the tubeside fluid, as indicated by the larger percent thermal resistance for the tube side.

Known duty rating case Tubeside process conditions

specified

Exit air temperature

179.31 °F

Pressure drop air side

0.330 in. H2O

tube side

3.754 psia

Design heat duty

3.174 MM Btu/hr

Thermal overdesign

-2.08

Fans Number

3

Size

4 ft diameter

Fan-to-bundle face area ratio

0.42 (within API specifications)

Fan power

1.24 hp

Page 148



Test Cases

Xace Test Case 1 Output


Page 149

Test Cases


Xace Test Xace Test Case 2 The second test case is a horizontal forced-draft air-cooled heat exchanger with a tubeside liquid stream consisting of organic compounds. Process conditions of the case are as follows:

Process Conditions Tubeside Fluid Flow rate

318 1000 lb/hr

Inlet temperature

133 °F

Inlet pressure

65 psia

Outlet temperature

115 °F

Air Side Flow rate

245060 ft³/min

Inlet temperature

100 °F

Outlet temperature

117.60 °F


Carbon steel


1.0 in.

Tube wall thickness

0.065 in.

Fin material

Aluminum

Fin height

0.625 in.

Fin thickness

0.023 in.

Fin density

10 fins/in.

Tube length

30 ft


75

Tube pitch

2.5 in.

Tube layout

Staggered

Number of tuberows

5


5

Page 150



Test Cases

Xace Test Xace Test Case 2 Results As in Test Test Case 1, the geometry geometry is simple simple enough enough that the rating rating check with other other programs programs is possible. possible. Test Case 2 is heat transfer-controlled by the airside stream. X ace issues ace issues a data check message that indicates specified heat duty does not match given process conditions.

Simulation Case Tubeside fluid composition

unknown

Physical properties for fluid

known at inlet and outlet conditions Enter as a pseudo a pseudo-single -single component at inlet and outlet conditions, the same way that Test Case 1 handles physical properties.

Exit air/tubeside temperatures

117.60 °F and 115.00 °F


0.434 in H2O of an allowable 0.6 in. H2O

tube side

10.785 psia of an allowable 10 psia

Film coefficients (based on bare surface area) air side

178.42 Btu/hr ft² °F

tube side


Airside thermal thermal resistanc resistance e

60.27%

Fans Number/bay

2

Size

15 ft diameter

Tip clearance

0.75 in.

Fan-to-bay area ratio

0.75 (within API specifications)

Fan power

14.62

Because this simulation has unknown duty, design and actual conditions are within a convergence tolerance of 2.5%. The air-cooled heat exchanger is thermal-controlled by the airside process, as indicated by the 59.2 % of thermal resistance.


Page 151

Test Cases


Xace Test Xace Test Case 2 Output

Page 152



Test Cases

Xace Test Xace Test Case 3 The third test case is a horizontal forced draft air-cooled heat exchanger with tubeside condensation. The tubeside fluid is a hydrocarbon mixture.


80 1000 lb/hr

Inlet temperature

315 °F

Inlet pressure

50 psia

Outlet temperature

175 °F

Air Side Face velocity

550 ft/min

Inlet temperature

70 °F


Carbon steel


1 in.

Tube wall thickness

0.109 in.

Fin material

Aluminum

Fin height

0.625 in.

Fin thickness

0.017 in.

Fin density

9 fins/in.

Tube length

26 ft


62

Tube pitch

2.5 in.

Tube layout

Staggered

Number of tuberows

4


1


Page 153

Test Cases


Xace Test Case 3 Results This test case illustrates calculated property profiles. The tubeside fluid composition for X ace Test Case 3 is known, and all components are in the Automatic Properties Data Bank. The Automatic Property Code is specified for all components, and X ace is allowed to calculate the condensing curve and property profiles using databank Antoine Coefficients and ideal mixing rules. The geometry for this case is simple, with no complex specification needed.

Known duty case Tubeside fluid

condensing with noncondensable gas present (rigorous flash calculation)

Outlet airside temperature

145.51 °F


0.346 in. H2O

tube side

2.279 psia

Film coefficients (based on bare surface area) air side


tube side


Thermal resistance air side

52.47%

tube side

45.05%

tube and fin material

2.48%

Overdesign

4.4%

Heat duty

15.263 million Btu/hr

Page 154



Test Cases



Page 155

Test Cases


Xace Test Case 4 X ace test case 4 is a heat recovery system with boiling water on the tube side.


22.5 1000 lb/hr

Inlet temperature

545 °F

Inlet pressure

1000 psia

Outlet temperature

545 °F

Air Side Flow rate

45 1000 lb/hr

Inlet temperature

720 °F

Outlet temperature

—

Geometry Tube bundle orientation

Vertical

Tube material

Carbon steel


2 in.

Tube wall thickness

0.109 in.

Fin material

carbon steel

Fin height

0.75 in.

Fin thickness

0.049 in.

Fin density

5 fins/in.

Tube length

4 ft


11

Tube pitch

3.464 in.

Tube layout

Staggered

Number of tuberows

13


1

Page 156



Test Cases

Xace Test Case 4 Results This case illustrates the use of tubeside boiling as well as gas cooling outside tubes. Physical properties of combustion gases have been entered, along with the heat release curve. The tube wall temperatures in economizers are typically quite high. In this case, the program warns that tube wall thermal conductivity was calculated outside the built-in correlation range. It is better in this instance to enter the tube’s thermal conductivity on the Tubes page, Tube Types panel, Geometry group.

Known duty case Tubeside fluid weight fraction

Boiling saturated water 0.0 to 0.125

Outside fluid

mixture of combustion gases from burning methane, 20% excess air

Outside exit stream

hot gas at 576.59 °F

Pressure drop outside

0.192 psi

tube side

1.269 psi

Film heat transfer coefficients

outside


tube side

1196.65 Btu/hr ft² °F

Thermal resistances outside

79.73%

tube side

9.33%

fouling

7.31%


3.62%

Overdesign

11.23%

Heat duty

1.828 MM Btu/hr


Page 157

Test Cases



Page 158



Test Cases

Xace Test Case 5 X ace test case 5 is a horizontal forced draft air-cooled heat exchanger with 2 fans. Carbon dioxide gas enters the exchanger in the supercritical region.


200 1000 lb/hr

Inlet temperature

173 °F

Inlet pressure

1340 psia

Outlet temperature

105 °F

Air Side Flow rate

253486 ft³/min

Inlet temperature

85 °F


Carbon steel


1 in.

Tube wall thickness

0.091 in.

Fin material

Aluminum

Fin height

0.609 in.

Fin thickness

0.016 in.

Fin density

10 fins/in.

Tube length

34 ft


66

Transverse tube pitch

2.5 in.

Tube layout

Staggered

Number of tuberows

6


4


Page 159

Test Cases


Xace Test Case 5 Results Test case 5 is an air-cooled heat exchanger with carbon dioxide gas entering the exchanger in the supercritical region. This case illustrates use of the split-pass header option and input of a physical properties profile. All properties were included on the profile. Row 2 of exchanger is split between passes 3 and 4, while row 5 is split between passes 1 and 2. The number of tubes per row is the same for each row, and the tube count per pass is the same for each pass.

Known duty case Pressure drop outside

0.696 in. H2O

tube side

5.875 psia

Film heat transfer coefficients air side

7.83 Btu/hr ft² °F (based on bare tube surface area)

tube side

39313 Btu/hr ft² °F

overall for process design


overall for specified geometry


Thermal resistance air side

56.70%

tube side

29.24%

fouling

11.51%


2.55%

Overdesign

11.32%

Heat duty

9.025 Btu/hr

Fans Number

2

Diameter

12 ft.

Fan tip clearance

0.7200 in.

Fan-to-bay area ratio

0.48

Fan power

32.53 hp

Page 160



Test Cases



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Frequently Asked Questions


X ace Frequently Asked Questions How do I rate an air-cooled heat exchanger used as a propane vaporizer? The process temperatures are below air inlet temperature, and Xace does not allow the case to run. Change unit type to an economizer. All calculations are handled correctly. X ace even calculates fan performance if you enter a fan diameter and number of fans. How do I enter complex physical property profiles? Some users have encountered problems when using complex physical property profiles (as generated by process simulators) with HTRI programs. HTRI encourages using simulator properties to model non-ideal mixtures accurately. However, X ace occasionally issues fatal error messages when it interpolates these sophisticated property grids. The following recommendations should help you enter complex physical property profiles: If pressure effects are minimal, reduce property profile input from two or three isobars to one isobar at limiting reference pressure (lowest P for condensing, highest P for boiling). Typically, this recommendation applies to non-vacuum cases in which the pressure drop is less than 10 percent of the inlet pressure. Adjust each temperature grid to place most points in non-linear (e.g., phase-change) region. Include exact bubble and dew point temperatures for each isobar if subcooled and superheated zones are present. To prevent extrapolation, adjust end-point temperatures to include all bulk and wall conditions. Re-enter all properties at new reference temperature for each isobar. Consult simulator reference manuals to determine recommended choice of mixture model. Check property profile in detail for any inconsistencies. The Stream Properties on the Graphs tab can be especially helpful in identifying problems with properties profiles obtained from process simulators. If you cannot resolve a property profile problem by the above means, forward the case to HTRI for review. If possible, transmit property cases by e-mail or diskette to eliminate transcription errors and improve response time. Otherwise, fax or mail a copy of the HTRI Input Data Reprint (not actual input data file). Use a large, bold, fixed-width font when you fax to avoid transcription errors. Is there any way to run Xace on the Windows 95 original release? ®

®

The original release of the Microsoft Windows 95 operating system does not run HTRI ® X changer Suite without some system updates. If you are running the original release of Microsoft Windows 95, install Microsoft Internet Explorer 5.0 or later before you install X ace. Internet Explorer is available for free from Microsoft and updates a number of system components when installed. If you have already installed X ace, uninstall and reinstall it after you load Internet Explorer 5.0. Check which version of Microsoft Windows 95 you use by running the System application in the Control Panel. Near the top of the dialog box that appears is a version number starting with 4.00. If the version ends in the letter B or greater, no updates are required. If the letter is A or no letter is present, updates may be required to run X ace. Page 162




The Contents tab is missing from Help files in Windows 95/98. Due to limitations in Microsoft Windows 95/98, the help file Contents tab may be missing from the left edge of the help window. This situation can occur when you access a help file from a network drive (e.g., shared network install). To correct the problem, check the following items: 1

When multiple users access the same installation, the HTRI shared and application directories must be set as Read only.

2

Delete any .GID files present in the HTRI shared and application directories. These hidden files are created by Windows when a help file is created. For multiple users, these files should be created on the local machine, which happens automatically if the HTRI shared and application directories are Read only.

3

If you access HTRI X changer Suite via a UNC specification (e.g., \\Computer\HTRI\XchangerSuite1), change to a mapped drive specification (e.g., M:\HTRI\xchangersuite1). It will be necessary to modify some Xace registry entries using REGEDIT. If you are not comfortable editing your registry, ask for assistance from your local IT group or contact HTRI Technical Support.

®

The X ace registry keys are located at \\HKEY_LOCAL_MACHINE\Software\HTRI\XAC\1.00 You need to change all registry keys that reference a UNC path specification to the equivalent mapped drive. You can encounter the same situation when you access help files via the Start menu shortcuts. The same correction can be applied: Change the shortcut path and Start In directory to use a mapped drive rather than a UNC specification. Why can’t I get context-sensitive help for disabled fields? As a feature of Microsoft Windows, context-sensitive help is not available when fields are disabled. To get information on a disabled field, go to the full online help via the Help menu. The axis labels don’t appear in graphs. Why? The missing labels result from the default font size used on axis labels; typically, this problem occurs when you plot only a couple of points along one axis. Correct the display by changing font size on axis labels in the following manner: 1

Press right mouse button while a graph is displayed.

2

Select Chart Designer .

3

In the tree view of Chart Designer, select each axis in turn.

4

Select Axis Labels.

5

Select Font tab in the right window.

6

Decrease font size. Repeat steps 3 through 6 for all axis labels.

I can’t delete components with Delete key. Is something wrong? © Heat Transfer Research, Inc. All rights reserved. Confidential: For HTRI member use only.

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To delete a component, select component by clicking component number and then clicking the Delete button (below the Add button on the panel or page). Can I use the old DOS interface available with ACE 3.2? The interface is available, but HTRI STRONGLY RECOMMENDS that you use the graphical user interface instead. The DOS interface, which will be eliminated in a future version of X ace, has not been tested and may not work properly. To use MS-DOS interface 1

Open an MS-DOS window.

2

Set default to location of Xace100.EXE (use FIND to locate file).

3

Type Xace100.

How can I make tube information that I added to HIGHFIN.BNK appear in the drop-down list? For the tube information to appear on the drop-down list, 1

Format the new entry like the existing entries.

2 Alphabetize

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the codes.

3

Use the same code in both the first and the second text fields of the first line of the new entry in HIGHFIN.BNK. Tip: Try limiting the code to three characters.

4

Create a unique code for each tube.



About This Version

X ace About This Version ®

X ace 5.0, which replaces all versions of X ace, represents a significant modification from earlier versions. Some of the more significant modifications/enhancements to X ace 5.0 include the following: Pressure drop balancing between multiple tube rows in a single pass has been corrected. Logic has been modified to improve convergence for close temperature approaches. A new bundle layout option allows easy specification of equal count with defined passes on each tuberow. Rectangular fins are now drawn correctly in the bundle layout drawing. More items (e.g., fin thickness and efficiency) have been added to the available items in the Session log. Heat transfer/pressure drop methods have been modified to ensure extrapolation to the same value for staggered/inline layouts as pitch increases to very large values. Users can now choose to synchronize transverse/longitudinal pitch input for equilateral layouts or allow independent specification. A row correction factor from Reports AC-10 and AC-11 was implemented, increasing by a few percent the predicted heat transfer coefficients. Boiling Methods Calculation Procedures Condensing Methods Data Input and Data Check External Interfaces Graphical Interface Miscellaneous Physical Properties Program Outputs Single-Phase Methods Tube Layout


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About This Version


Boiling Methods Version 5.0 Shellside boiling

An error has been corrected in the call argument to the shellside boiling routine. The argument was incorrect, but this correction does not change the results. (CR2806)

Version 3.0 Service Pack 2 Tubeside boiling heat flux

The heat flux for tubeside boiling is now based on the inside surface area. In all previous versions of X ace and ACE, the flux was based on the outside surface area. As a result of this correction, predicted boiling heat transfer coefficients may be slightly higher and some cases may now predict film boiling. The heat fluxes on the tubeside monitors are also slightly higher, reflecting the surface area change. (CR1494)

Version 3.0 Improve tubeside film boiling prediction at high mass velocities

HTRI research data obtained at high mass velocities indicates that the tubeside film boiling coefficient is overpredicted by methods in X changer Suite 2.0. The method has been updated, with appropriate limits placed on the calculated film boiling coefficient. The following limits have been imposed: 1. Heat flux to maximum of 18915 W/m² (6000 BTU/hr ft²) 2. Mass velocity to maximum of 1464720 kg/hr m² (300000 lb/hr ft²) 3. Reduced pressure to maximum of 0.5 when weight fraction vapor is less than 0.5 These conditions have also been imposed: 1. Film boiling heat transfer coefficient must be greater than sensible vapor coefficient for vapor flowing alone 2. Film boiling heat transfer coefficient must be less than the sensible vapor coefficient for total flow rate vaporized If any limit is exceeded, the film boiling heat transfer coefficient is calculated at the limiting value. These modifications improve predictions for tubeside film boiling and the HTRI tubeside vertical thermosiphon data. If any limit is exceeded, the predicted film boiling heat transfer coefficient will be less than that predicted by the previous method. In general, the percent change is small. (CR399)

Up- and downflow boiling tubeside pressure drop Page 166

The static head pressure effect in downflow boiling is now correctly set to zero based on current HTRI recommendations. Previously, it was added in as a pressure loss. Falling film evaporators are handled correctly. (CR603) © Heat Transfer Research, Inc. All rights reserved. Confidential: For HTRI member use only.


Tubeside mixture film boiling heat transfer coefficients

About This Version

The tubeside film boiling heat transfer coefficient calculation has been updated. This update is based on HTRI’s vertical thermosiphon and tubeside boiling research. Analysis of mixture data shows that· No mixture correction is necessary for pure components and mixtures with boiling ranges less than 56 °C. A physical property correction factor was necessary so that the corrections extrapolate well to other fluids and process conditions. The film boiling heat transfer method for twisted tape inserts has also been updated. These changes have an impact on tubeside film boiling of fluids with boiling ranges less than 166.7 ºC. On average, the improved methods increase the film boiling coefficient by about 9% over the methods in X changer Suite 1.0. However, the film boiling coefficient can increase as much as 40% for cases with a reduced pressure greater than 0.85 and with vapor Reynolds numbers greater than 50000. It is possible that cases very close to the lower temperature limit for stable film boiling will have a lower film boiling coefficient resulting from the addition of the physical property correction factor. If the ratio of wall saturation temperature to the wall temperature is less that 0.25, the coefficient is up to 20% lower. (BT-27, CR537)

Version 2.0 Boiling Outside Tubes

X ace now includes methods for boiling outside tubes, both plain and low finned. These methods are the same as the ones X ist uses for shellside boiling in TEMA X shells. (QC 200110001, 200110016, 200111012)

Tubeside Nonequilibrium Mist Flow Boiling Model

HTRI has developed and implemented a new theoretical non-equilibrium model for mist flow and vapor superheating heat transfer in a tube to rate the performance of exchangers with heated tubes more realistically. Droplets actually evaporate very slowly and are difficult to remove from the vapor stream unless some type of insert is used in the tube. The software now indicates that the results are optimistic and warns that twisted tape inserts are required. If inserts are not incorporated in the tube design, you can expect much more superheating than actually is obtainable. Previously, HTRI software used an equilibrium model that overestimated the amount of droplet evaporation and superheat produced in mist flow inside a heated tube. (QC 200112021)

Tubeside Boiling Dry Wall (Mist Flow) Methods

New methods have been developed for tubeside mist flow boiling. The new model, described in HTRI Report BT-22 (2002), is a theoretical non-equilibrium model for mist flow and vapor superheating heat transfer in a tube. The nonequilibrium model predicts the temperature profile and heat transfer rate for mist flow in a tube. (QC 200112021, 200203003) © Heat Transfer Research, Inc. All rights reserved. Confidential: For HTRI member use only.

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About This Version


New Tubeside Flow Boiling Methods for Twisted Tape Inserts

New models for intube boiling with twisted tapes have been developed and implemented in the programs. These new wet-wall flow boiling heat transfer and pressure drop methods are based on extensive HTRI research. Also included in the methods is an improved method for mist flow boiling with twisted tapes. The methods are documented in HTRI Report BT-23.(QC200202033, 200202040, 200203003, 200203023, 200205022, 20020531, 200205044)

Calculated Negative Boiling Range

X ace has been updated so that it does not subtract the calculated dew point from the bubble point when calculating the boiling range. Formerly, the resulting boiling range was always negative, resulting in overprediction of the boiling heat transfer coefficient in nucleate boiling and possibly premature prediction of film boiling. Cases in which you specify the boiling range are not affected by this correction. (QC200111012)

Extrapolation of Boiling Range

X ace and X ist have been changed to limit the extrapolation of the boiling range to 532 °C (990 °F) to avoid triggering the wide boiling range/viscous core film boiling correlations. Using these correlations results in a much lower boiling heat transfer coefficient, which may not be appropriate for these cases. If the boiling fluid viscosity at the boiling point in the heat exchanger is greater than about 5 mPa s (5 cP), rerun the case entering a boiling range of 538 °C (1000 °F) to use the wide boiling range/viscous core film boiling calculation method. (QC 200203018)

Mixture Correction for Tubeside Film Boiling

The mixture correction effect was removed for tubeside film boiling based on recent HTRI film boiling research data. (QC 200203009)

Mixture Correction for Tubeside Boiling

Procedures for calculating the mixture correction for tubeside boiling have been updated to handle cases properly with a very small amount of latent duty compared with the sensible duty. (QC 200202033, 200203023)

Bubble Point Temperature in Liquid Zone

The bubble point temperature in the liquid zone has been reset in each increment to reflect the local saturation pressure. Previous versions of X ace, ACE, X ist , and IST looked only at the inlet conditions. As a result, the boiling coefficient could be slightly underestimated as the boiling fluid incorrectly went from subcooled boiling to sensible liquid and then to boiling. (QC 200203035, 200203037)

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About This Version

Calculation Procedures Version 5.0 Updated tubeside pressure balancing

In cases in which the pressure drops between rows in a pass differed widely (e.g., a case with full separation in the header), the program experienced some difficulty balancing the tubeside pressure. An error in the pressure balancing routine has been fixed. (CR2688)

Natural draft option with correct incremental properties

Selecting the natural draft option may have caused the program to use incorrect tubeside physical properties for incremental calculations. This potential problem has been eliminated. In cases with large physical property variations on the tube side, heat transfer and pressure drop answers will change. (CR2789)

Limits to shellside flow variations

Limits to the amount of variation allowed for unknown shellside flow between iterations were added. This change stops cases from going out of control in one increment. (CR2856)

Airside longitudinal pitch heat transfer and pressure drop correction

The longitudinal pitch effect has been updated for longitudinal pitches greater than about twice the transverse pitch. Prior to correction, pressure drop and heat transfer calculations did not trend properly as the longitudinal pitch increased while the transverse pitch remained constant. Values for an inline layout were predicted to be higher than the values for a staggered layout. Further, the staggered and inline values did not approach the same value as expected at large longitudinal pitches. After modification, X ace calculates reasonable pressure drops and heat transfer coefficients for longitudinal pitches that are more than twice as large as the transverse pitch. For longitudinal pitches above 1.3 times the transverse pitch, users may see pressure drop differences of up to 20% from the previous method. (CR2437)

Updated Xace convergence methods

X ace convergence methods have been changed to a version that shows marked improvement in the handling of cases near a temperature pinch. This method has been verified using new data from the shellside crossflow unit, some of which nears pinching out. The new method is able to predict exchanger performance better for the pinched out data. Previously existing HTRI data sets are unaffected by the change. (CR3132)

Percent overdesign convergence for air coolers

X ace now converges to a zero percent overdesign in more cases. Previously, as a result of oscillation, the logic occasionally failed to converge when there was a feasible solution. (CR3173)

Change in tube wall resistance calculation

The tube wall resistance calculation is now based on the bare metal inside diameter. Previously, this calculation used an inside diameter that included the fouling layer, which was incorrect. This change increases the tube wall coefficient; the magnitude of the increase depends on the fouling layer thickness and resistance, and for cases with a significant fouling layer, a change in the overall heat transfer in the exchange. In the X ace testset, fewer than 10 cases changed more than 2%, and no case changed more than 10%. (CR3162) © Heat Transfer Research, Inc. All rights reserved. Confidential: For HTRI member use only.

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About This Version


Added convergence error to natural draft to stop potential infinite loop

A fatal convergence error has been added to the X ace natural draft option. If the program is unable to determine an airside outlet temperature that is low enough to keep the tubeside outlet temperature higher than the airside inlet temperaure, it issues a fatal convergence error instead of entering an infinite loop. (CR2804)

Modified equal count default bundle layout type

As a result of comments from HTRI users, the equal count layout has been changed to a serpentine layout with a new method to allocate extra tubes (the tubes remaining after an even split of tubes over all tube passes). The new allocation attempts to minimize hanging tubes while distributing the extra tubes equally throughout the bundle. Eliminating hanging tubes takes priority over equal count in such layouts. (CR1759)

Changed fan lanes to "fully blocked to air flow"

In X ace, fan lanes were not being handled as "fully blocked to air flow" through the bundle. This error caused fan lanes to affect pressure drop and Reynolds number through the bundle. Fan lanes are now fully blocked in X ace. The only value affected by fan lanes is now face velocity, which is based on the full bundle inlet area. (CR3232)

Version 4.0 Service Pack 3 Fan ring pressure drop for multiple services

The X ace multiple services option now respects the user-entered fan ring type and calculates a fan ring pressure drop using the specified fan ring type. Prior to this modification, X ace always assumed a straight fan ring type. This modification corrects HCPA item X ace 4.0-6. (CR3019)

Motor power per fan at minimum temperature for multiple services

For multiple services cases, the motor power per fan at the minimum temperature is now calculated using the overall bay performance. The overall value is printed on individual bundle output reports for bundles in service. (CR2590)

Version 4.0 Service Pack 1 Programcalculated tube supports based on ISO standard

Per ISO 13706:2000 Section 7.1.1.4, the program-calculated number of tube supports will be based on a maximum unsupported span length of 6.0 feet (1.8288 meters). (CR2493)

Consistent definitions for rectangular fin dimensions

The definitions of the rectangular fin dimensions in the X ace engine, user interface, and online help were not consistent in previous versions of X ace. The rectangular fin width is now defined as the length perpendicular to air flow, and the rectangular fin height as the length parallel to air flow. See Figures of Rectangular Sections in the online help to view these dimensions. Please note that you should check previously entered rectangular cases for consistency with these definitions. (CR2469)

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Pressure for air property calls limited to 0 psia

About This Version

Pressure in calls to the air property routines are now limited to 0.0 psia. This limit allows X ace to recover if an intermediate pressure drop is calculated that is higher than the inlet pressure. Very few cases are affected by this change. (CR2551)

Version 4.0 Running cases in any order in DOS

You can now run cases in any order from DOS. Previously, if you ran an air cooler case after an economizer case, the DOS engine did not handle it correctly. The graphical interface handled cases correctly in previous versions (CR1792).

Steam coil default pitch changed

The steam coil default pitch has been changed from 2.5 to twice the transverse pitch of the bottom row in the exchanger. (CR1620).

Handling of fluid properties at nozzles modified

Respecting user-specified outlet temperatures, X ace no longer resets fluid conditions at the nozzles during iterations unless the terminal temperatures for the tubeside fluid are changed. This update corrects HCPA item X ace 3.0-16. (CR1470)

Updated X ace now calculates bay width summing the bundle widths, twice the side seal calculation of bay width (currently defaults to 0.0), and twice the side channel thickness (currently defaults to 6.35 mm (0.25 inches). Additional, X ace adds 12.7mm (0.5 inches) width between bundles in the bay. (CR1855) f and j factors for multiple tube types

f and j factors now work properly for all tube types. The sequencing error in the transfer of data to X ace has been corrected. (CR1775).

Increase in maximum number of rows

X ace’s maximum number of rows has been increased from 60 to 99. (CR1218)

Number of increments for Xfh

X ace has been modified to set the number of increments per row in the output branch of the X ace bundles in X fh cases. (CR1602)

Running Xfh bundles

X ace has been modified to correctly interpret the order of execution of X fh convection units. (CR1611)

Change in steam coil weight calculations

The calculation of steam coil weight (part of the structure weight) is now done for every bundle. Also, the steam coil weight assumes 100 pound steam for the calculation of the steam coil material density. (CR1684)

Correct setting of This change corrects a problem that can occur when multiple X ace units are stream properties connected together in series (for example, when modeling multiple bundles in an X fh convection section). Each unit writes fluid properties for the inlet and outlet in multiple units streams. When bundles are connected together, the inlet for one bundle is the outlet for another bundle and the properties may get written incorrectly. This change modifies the behavior to allow for connected bundles. (CR1683) © Heat Transfer Research, Inc. All rights reserved. Confidential: For HTRI member use only.

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About This Version

Plenum height calculated according to ISO 13706:2001 standard


X ace now calculates plenum height as described by ISO 13706:2001 standard 7.3.4.7 and Figure 7. The value calculated by X ace is the minimum plenum height for the bay. (CR2246)

Version 3.0 Service Pack 2 Pressure values for film boiling and economizers with hot fluid on shell side

Pressure references in calculating coolant heat transfer coefficient have been corrected. This update affects very few cases; of those it affects, changes are usually less than three percent in the overall heat transfer coefficient. This update corrects HCPA item X ace 3.0-12. (CR1511)

Temperature limits added to natural draft cases

X ace now limits the incremental, wall, skin, and fin tip temperatures for natural draft between the cold inlet and the hot outlet to prevent impossible temperatures from occurring in each increment. This change affects incremental temperatures shown in the monitor, but has little or no effect on the overall results. (CR1558)

High auxiliary pressure drops

For fan guards and hail screens, the calculated pressure drops are now correct when you enter 100% open area in the input. Previously, the values were calculated to be different from those when no guard or screen was specified. (CR1628)

Version 3.0 Service Pack 1 Pressure drop during convergence

X ace internally allows up to 99 percent of the inlet pressure drop in gas and two phase systems before terminating the case. Previously, the limit was 98 percent. With this change, additional cases that were previously stopped because of excessive pressure drop now can converge. (CR1433)

Section splitting for maldistribution

In the case of maldistribution, X ace now correctly splits the bundle into 6 sections of equal area across the tube bundle width using the bundle width of the widest tuberow. Previously, the split was correctly done only when the number of tubes in the row was evenly divisible by six. This update corrects HCPA item X ace 3.0-3. (CR1445)

Classic design with number of rows and tubepasses not entered

If you specify a classic design case with variable number of rows and variable number of tubepasses and the number of tubepasses exceeds the number of rows, X ace will now properly allocate tubes to the appropriate tubepasses. Previously, the allocation was incorrect, and the pressure drop was not output. This update corrects HCPA item X ace 3.0-4. (CR1446)

Tubeside flow distribution with large changes in viscosity

X ace now properly balances flow down each row of a multi row tubepass. X ace relies on pressure balancing to determine the amount of flow down each row in any given pass. The pressure balancing has been changed to force equal tubeside pressure drops for rows in the same pass by changing the fraction of flow down each row. This update corrects HCPA item X ace 3.0-5. (CR1444)

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About This Version

Resetting the default bundle layout

X ace now sets the default bundle layout to rows unless the number of tubepasses is greater than the number of tuberows. In this case, the default layout is always equal count. This update corrects HCPA item X ace 3.0-7. (CR1385)

Unheated tube length not copied from output geometry

The unheated tube length is no longer copied in the Copy Output Geometry to Input option, thus allowing the correct value to remain in the input. This update corrects HCPA item X ace 3.0-9. (CR1327)

Unheated tube length used in calculations

If you specify an unheated tube length, X ace now correctly calculates the total unheated tube length as the value specified plus the total width of the tube supports. This update corrects HCPA item X ace 3.0-10. (CR1327)

AC-12 incremental row correction not fully implemented

The heat transfer row correction factors described in AC-12 are now implemented for rows 1 through 3 for all exchangers regardless of the total number of rows. This feature causes the outside heat transfer coefficient to drop a small percentage (between 2 and 7 percent in most cases) for exchangers with 4 or more rows. (CR1437)

Version 3.0 [back to top] Total separation in headers

A new option has been added to the Methods panel to calculate tubeside condensation with total phase separation in the headers between passes. This option represents a "worst case" result and offers you an opportunity to perform a "what if" check of the final results. (CR240)

Program crash when tube types added and then removed

X ace now uses the tube type of the first row when making calculations that involve only one tube type. Previously, if tube type 1 was not present in the bundle because of user changes made using the Bundle Layout panel, the program crashed when the case was run. This update corrects HCPA X ace 2.0-34. (CR527)

EMTD calculation X ace now splits large sections into smaller sections, thus allowing some cases with problem caused equal count layouts to converge better. Previously these cases experienced an EMTD that was too large. Typically, one or two tubes from the previous tubepass by convergence carry over to the next tuberow. The problem, which occurred when internal sections issues with were too different in size, resulted from convergence failure. X ace did not always "hanging tube" flag the convergence failure correctly with a program message. This update cases corrects X ace 2.0-38. (CR698) Upper and lower bounds on all temperatures

In some cases, X ace calculated temperatures that were either higher than the hot inlet temperature or colder than the cold inlet temperature. Limits have been placed on the incremental temperatures, skin temperatures, and fin tip temperatures during program calculations. This update corrects X ace 2.0-39. (CR124)

Equal count layout crash

In some cases with an equal count layout and more than one tube type, widely different transverse pitches were being laid out incorrectly in X ace. This problem has been corrected. This update corrects X ace 2.0-47. (CR900)


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About This Version


Film boiling check cannot be disabled

The Bypass film boiling calculations option on the Methods panel now works properly. Previously, the film boiling check was performed even when the option was enabled. This modification corrects HCPA item X ace 2.0-18. (CR239)

Nozzle location for vertical exchangers respected

With regard to nozzle placement for vertical exchangers, X ace now respects the value in the field Tube orientation, Unit panel. If you do not set this field, nozzle placement is always at the bottom for cases with cold fluid on the tube side and always at the top for cases with hot fluid on the tube side. This modification corrects HCPA item X ace 2.0-51. (CR965)

Corrected minimum and maximum skin temperatures printed on reports

X ace now reports the correct values for the minimum and maximum skin temperatures on both air side and the tube side. This modification corrects HCPA item X ace 2.0-53. (CR801)

C channel weight

The weight of the C channel now uses the appropriate bundle width instead of the frame depth in determining the weight of side channels. This modification corrects HCPA item X ace 2.0-55. (CR1176)

Handling of airside flow rate for cases with sections of differing sizes

X ace now handles airside flow distribution for cases with different sized sections correctly. Previously, the flow rates were not always distributed properly, resulting in different airside pressure drops over the bundle. This modification corrects HCPA item X ace 2.0-56. (CR883)

Wall and skin temperature calculations for natural draft

The wall and skin temperature calculations for natural draft now use the appropriate temperatures for natural draft. Previously, the values reported were based on forced draft conditions. This modification corrects HCPA item X ace 2.0-58.

Version 2.0 Service Pack 2 Corrected answers for entered bundle width

X ace has been updated to ensure that equal count cases with poor convergence yield the same answers, regardless of whether you enter bundle width or number of tubes per row.

Wet wall desuperheating

A problem in the way X ace handled calculation of the wet wall desuperheating heat transfer coefficient has been corrected. Cases most affected are those with· more than 20% of the increments in wet wall desuperheating· large EMTDs· 3 rows in heating/condensing and one row in subcooling· vertical exchangers· condensers with large fouling factors·

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About This Version

condensers with very low tubeside Reynolds numbers· condensers with more than 50 percent overdesign Although the potential exists for a large difference in expected answers, in the 5349 cases in the X ace test set, only 202 (3.8 %) changed by more than 3% overdesign, and only 26 cases (0.4%) changed by more that 10%. (CR208) All previous versions of X ace and ACE exhibit this problem. This update corrects HCPA X ace 2.0-24.

Version 2.0 Service Pack 1 Classic Design In a classic design, X ace no longer crashes for induced draft units when you do Program Crash for not enter Number of rows or Plenum height. This modification corrects alert item Induced Draft X ace 2.0-6. (CR94) Natural Draft

X ace now correctly handles the natural draft calculation whether or not you enter the air flow rate. Previously, the natural draft calculations incorrectly used the entered value in initial calculations resulting in a different predicted flow rate than the correct value. This modification corrects alert item X ace 2.0-5. (CR99)

Version 2.0 Bundle and Structure Weight

X ace now estimates the bundle and structure weights and includes them on the Final Results. (QC200203006, 200203041)

Bundle Drawing on Drawings Tab

X ace updates the bundle layout when you rerun a case, thus assuring that the output drawing reflects the calculated results. This update corrects HCPA item X ace 1.0-9. (QC200203021,200204029, 200204059, 200205033, 200205029)

Calculated Bundle X ace now correctly calculates the input bundle width if an even row is the widest row in the bundle. X ace 1.0 underestimated the number of tubes from the bundle Width width for these cases. (QC200201018, 200202004) Number of Tubes Calculated from Bundle Width

The procedure for determining the number of tubes in each row from the tube pitch and bundle width has been updated. Before corrections, one too few tubes was placed on each row. This update corrects alert item X ace 1.0-2. (QC200110003, 200111017)

Tube Count per Row Passed to Calculation Engine

The HTRI X changer Suite GUI now passes the tubecount per row and location of the first tube in each row directly to the calculation engine. This procedure eliminates any possibility of the calculation engine running a different case than you intended, improving the accuracy of the predictions. (QC200111019)

Overall Pressure Convergence Loop

The procedures have been updated to converge on the overall pressure drop even if the tubeside fluid is single-phase. This update does not affect air-cooled exchangers, but is required when X ace is called from FH. (QC200203008)


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About This Version


Starting Guess for X ace now ace now starts the incremental wall temperature based on the average Incremental Wall incremental temperature of each fluid. Previously, X Previously, X ace 1.0 ace 1.0 started with the average of all temperatures in the increment. In some cases, this method resulted Temperature in a crash in the boiling subroutines. (QC200111012) Messages Cleared Between Wall Temperature Iterations

Incremental Convergence

Messages generated in initial wall temperature iterations are now cleared properly. In all earlier versions, messages could be set because of the initial wall temperature guess that did not belong in the final results. For example, most messages indicating the condensate film coefficient was limited to 56750 W/m² ° C (10000 Btu/hr ft² ° F) were in error. (QC200202020, 200202028) The incremental convergence has been modified based on experience with X with X ist ist . As with earlier versions of X of X ist ist , X ace (as ace (as well as ACE) occasionally failed to converge sufficiently. (QC200112017, 200206011)

Tubeside Film Boiling at Low Fraction Vapor

The calculation procedure for tubeside film boiling at low qualities (less than a weight fraction vapor of 0.012) has been updated to provide a smooth transition to the liquid-only coefficient. Previous programs had an unrealistic coefficient change in the transition. (QC200203009)

Airside Flow Rate/Exit Temperature Convergence

Calculation procedures for handling cases in which the first approximation at the airside flow rate is much too high have been improved. Previously, the program stopped and reported the approximation as the final solution. X solution. X ace 2.0 ace 2.0 treats the approximation as simply a bad guess and continues convergence. Cases with this type of failure are easily identified: They have an airside pressure drop exceeding the air inlet pressure, an extremely high air flow rate, and usually a very high overdesign. (QC200203053)

Grid Design Option

The grid design logic has been improved to prevent incorrect switching to a classic design while the case is running. (QC200203072)

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About This Version

Condensing Methods Version 5.0 Condensation heat transfer coefficient

The condensing heat transfer coefficient is now limited to the value predicted for single-phase gas flow. Previously, the condensing heat transfer coefficient could incorrectly be a smaller value. (CR3058)

Twisted tape methods for horizontal condensing added

In previous versions of X of X changer changer Suite, Suite, the twisted tape methods for condensing were applied only for vertical cases. The vertical methods have now been applied to horizontal cases. This modification corrects HCPA item X item X ace 4.0-12. ace 4.0-12. (CR3526)

Version 4.0 Outside high fin condensing methods

X ace now ace now has two methods for predicting condensing over high fins: a ColburnHougen method for air dehumidification and a simplified RPM method. Both methods are available on the Methods panel. (CR1231)

Version 3.0 Liquid entrainment for reflux condensation

A message message has been been added added that compares the outlet vapor vapor velocity velocity to the velocity velocity that produces liquid entrainment. (CR672) If the outlet vapor velocity is below the entrainment velocity, an informative message indicates the current percent of the entrainment velocity. If the outlet vapor velocity is above the entrainment velocity, X velocity, X ace issues ace issues a warning message.

Sensible duty for vapor-phase resistance calculation

Calculation of the vapor-phase resistance for condensation increments has been updated in two ways: (CR675) 1

The fraction of sensible vapor to total duty is calculated strictly using the calculated temperature profile. Previously, X Previously, X ace used ace used the temperature and duty profiles to calculate this ratio. Because it is possible for temperature and duty profiles to be inconsistent prior to convergence, X convergence, X ace sometimes ace sometimes converged to an incorrect condensation coefficient in one or more increments.

2

The ratio of sensible vapor to total duty allows for duty imbalances. If you specify a different hot and cold process duty, X duty, X ace correctly ace correctly handles the sensible duty. Previously, the sensible duty was too high or too low, depending on whether the actual duty on the condensing side was less than the average incremental duty or greater.


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About This Version


Version 2.0 Service Pack 1 Very Low Condensing Heat Transfer Coefficient

Previously, if you did not enter components on the Property Grid in order, X order, X ace ace treated all components as non-condensing components and calculated a condensing coefficient equal to the sensible gas value. The problem occurred only if you skipped components. This modification corrects alert item X item X ace 2.0-14. ace 2.0-14. (CR143)

Version 2.0 Ammonia-Water Condensation Option

A new option option has has been added for for ammonia-wate ammonia-waterr condensation condensation based on on data provided to HTRI by NREL. The new method is a special modification of the condensation profile method (CPM). To use the ammonia-water method, you must enter the heat release curve either manually or via PPDS or property simulator interface (using the Property generator option). The internal vapor-liquid equilibrium generated by X by X ist ist and and X ace is ace is inadequate. (QC200202002, 200202011,200203012)

Subcooling Heat Transfer Coefficient

X ace now ace now uses the same subroutines to calculate the subcooled heat transfer coefficient as X as X ist ist . Previous versions of X of X ace and ace and ACE used a full tube of liquid approximation, which can predict a subcooling coefficient lower than is actually observed in the unit. (QC200112013)

Tubeside Condensation with Twisted Tapes

New heat transfer and pressure drop methods for tubeside condensation with twisted tapes have been added. Based on extensive HTRI research data with multiple twisted tape geometries, these data and methods show the following: Heat transfer enhancement increases as the twisted pitch/width ratio (H ( H /Dt ) decreases because the twisted tape provides good vapor-condensate mixing and reduces the condensing mass transfer resistance. Experimental data show that the maximum heat transfer enhancement ratio (h (htape /h /h plain) for condensation is about 1.5 to 2.2 for pure components and about 1.5 to 4.0 for mixtures.· The pressure drop in tubeside condensers increases as the twisted pitch/width ratio (H (H /Dt ) decreases. The pressure drop increase ratio ( P tape tape / P plain) ranges from 2 to 12 over a wide range of tape geometries and operating conditions. Comparisons with experimental data show that these methods predict heat transfer coefficients within ± 20 percent and pressure drop within ± 25 percent. Details of the method are given in HTRI Report CT-15. (QC200201022, 200205030, 200205041)

Average X ace has ace has been changed to use the average incremental properties when Properties Used to calculating the condensate film heat transfer coefficient. Previous versions of Calculate X ace and ace and ACE used the inlet properties in the increment, which resulted in an Condensate Film incorrect prediction of the condensing heat transfer coefficient. X ace correctly ace correctly Heat Transfer used the average incremental physical properties for all other calculations. The Coefficient procedures in X in X ace are ace are now consistent with those in X in X ist ist . (QC200111012) Page 178



Tubeside Water Condensation in Presence of Noncondensables

About This Version

The tubeside condensation procedures have been updated to handle properly the vapor-phase resistance calculation when noncondensables are present but water is the only condensing component. Previous versions of the program overestimated the vapor-phase resistance, predicting a condensing coefficient smaller than the actual value. This update corrects alert item X item X ace 1.0-16 ace 1.0-16 and X ist ist 1.0-15. 1.0-15.


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About This Version


Data Input and Data Check Version 5.0 Natural draft airside results and outside friction factor multiplier

If you enter the outside friction factor multiplier in a natural draft case, the program now uses this value when calculating the friction factor used in determining the airflow. (CR3309)

Loading inclination angles from .DAT files

The program now loads inclination angles from .DAT files correctly. Previously, any angle between 0 and 90 was read in as 90. The problem did not affect .HTRI files but only files exported to the .DAT format. (CR3442)

Individual unit conversions on Design Geometry panel

Converting the units on either the longitudinal or transverse pitch could incorrectly convert the other pitch. This conversion occurred only on the Design Geometry panel and only when individual field units were converted. This item has been corrected. (CR2988)

Rows with defined passes layout added

A new layout type, rows with defined passes, allows the user to specify a grid of passes on the bundle panel for each row. Tubepasses per tube will be assigned to ensure that the passes on that row are equal count. (CR2214)

User-entered value for dew point temperature of air

X ace now respects entered values for Dew point temperature of the air on the Optional panel. This modification corrects HCPA item X ace 4.0-9. (CR3280)

Chimney width and length value reversal

The chimney width and length entered on the Natural Draft panel are now handled properly in the calculation engine. Previously, the values were reversed. This modification corrects HCPA item X ace 4.0-10 (CR3195) (CR3195)

U-tubes limited to even tubepasses

For an air cooler, when you set the tube form to u-tubes and the number of passes is odd, X ace issues a data check message. Additionally, while running the classic design logic for u-tube cases, X ace uses only even tubepasses for air coolers. (CR3423)

Version 4.0 Service Pack 3 Tubeside weight fraction vapor for CHNG data records in .DAT files

The X ace graphical user interface was not reading in the tubeside weight fraction vapor from a .DAT file for cases using the CHNG record for records other than the HPRO record. This item has been corrected, and all records are now properly handled for CHNG record .DAT files. CHNG data records are present only in .DAT files created using a text editor. It is not possible to create them from the X changer Suite graphical user interface or from the older DOS user interface. (CR2805)

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About This Version

Version 4.0 Service Pack 1 Twisted tapes for multiple tube types

X ace now handles twisted tape inserts for multiple tube types properly. Previously, X ace handled only the first tube type correctly for twisted tape inserts. Subsequent tube types were assumed to have the same twisted tape inserts as tube type 1. This item has been corrected and X ace now respects twisted tape inputs for multiple tube types (above and including tube type 1). (CR2465)

Version 4.0 Unreasonable specified temperature check

A fatal error message has been implemented for specified inlet and outlet temperatures. If the temperature is higher than 2760 °C (5000 °F), the case does not attempt to run. (CR1889).

Entered heat release curve for air coolers

X ace now issues a warning message if cold heat release and/or property data (data records COLQ, CPLI and CPVA) are input for an air-cooled exchanger. The message indicates that entered property and heat release data will not be used for the cold side. The program instead uses HTRI’s air properties. Note that it has never been possible in ACE or X ace to enter this information; it may be entered only by using a text editor outside the interface. (CR1881)

Version 3.0 Check for valid serial number and company name

The program logic has been modified to check for valid program serial numbers and company names. These values are set during program installation. If an installation fails, these values can set to invalid values and cause a program crash when you run a case. The program now checks for valid values and issues a message to the run log if it finds any invalid values. If you receive this message, contact HTRI Technical Support. (CR705)

Version 2.0 Service Pack 1 Default Bundle Layout

The default bundle layout type is now by rows rather than equal count. X ace Online Help correctly indicated rows as the default; unfortunately, the calculation engine and bundle layout were incorrectly set to equal count instead. This modification corrects alert item X ace 2.0-13. (CR133)

Number of Fans Assumed for Natural Draft Air Coolers

You can now specify natural draft air coolers without fans. Previously, X ace and ACE always assumed one fan, even if none was specified. This modification corrects alert item X ace 2.0-15. (CR158, 179)

Version 2.0 Twisted Tape Width Input Added

New methods developed for twisted tapes include the width of the tape as a correlational parameter. Previously, the width was not required; tapes were assumed to be as wide as the tube inside diameter. (QC200201012, 200201008) © Heat Transfer Research, Inc. All rights reserved. Confidential: For HTRI member use only.

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About This Version


Short Tube Length Check

A check has been added to prevent the specification of a tube length shorter than the tubesheet thickness. (QC200203007)

Loading Files Created with ACE

The data reading subroutines have been updated to handle properly reading files created with ACE. Improvements include· Properly determining the fluid condition based on the weight fraction vapor· Setting the maldistribution control code properly This update corrects alert item X ace 1.0-10 and X ace 1.0-17. (QC200112022)

Data Check for Rectangular Finned Tubes

Page 182

The data check procedure has been updated to ensure that the specified dimensions of the finned tube are larger than the root diameter. Previously, you were able to specify rectangular fin dimensions too small, which caused a program crash. (QC200203046)



About This Version

Graphical Interface Version 5.0 Response time on Design Geometry Panel

When you entered values on the Design Geometry panel, the input fields performed extensive data checks, slowing response time. The logic has been corrected to improve the performance of this panel. (CR2975)

User-input air humidity

Previously, X ace did not always use the specified relative humidity to calculate the air properties. The user had to select a different humidity type and then reselect relative humidity. Now the program uses the entered value every time. (CR3149)

Bundle layout display of rectangular fins

The bundle layout drawing now correctly shows rectangular finned tubes. In previous versions, they were shown as circular fins. The calculations correctly used rectangular fins; the error occurred only in the drawing. (CR2372)

Longitudinal pitch in different units

The Tubes panel logic has been modified to see longitudinal pitch units correctly when the transverse and longitudinal pitch fields are in different unit types. Previously, when the two pitch fields were in different units (e.g., inch and mm), specifying a value in the transverse pitch field resulted in an incorrect value in the longitudinal pitch field. (CR3042)

Inclination angle data entry

The interface has been modified to allow entry of decimal digits for the slope/inclination angle on the Unit panel. Prior to this modification, the interface did not allow entry of any digits past the decimal point. (CR1839)

Moved "Use Summary Input" field

The Use Summary Input checkbox that appears for multiple services cases has been moved to the top of the Input Summary panel to improve visibility and be consistent with the X ist panels. (CR2308)

Number of nozzles in air cooler

The interface has been modified to respect the default value of 1 inlet and 1 outlet nozzle in an air cooler or economizer. Previously, a value of 1 was treated as not entered, and X ace could override the specified value. Now X ace respects any positive value for number of nozzles. Specifying a value of zero allows X ace to decide the correct number of nozzles. (CR2723)

Missing unit type with single increment option

The program interface has been modified to display the Unit type field on the Unit panel correctly when you select the single increment option on the Methods panel. Prior to modification, the Unit type remained blank on the Unit panel when you selected the single increment option. This problem was in the display only. (CR2977)

Equilateral layout option on the Tube Geometry panel

An Equilateral Layout checkbox has been added to the Tube Geometry panel. If this box is checked, X ace automatically calculates the longitudinal pitch for an equilateral layout from the entered transverse pitch. (CR2227)

Unheated length input item renamed

The input item description for unheated length in X ace has been changed from Total unheated length to Additional unheated length. The original description was inaccurate because this value does not include unheated length under tube supports and length inside tubesheets. This change does not affect case answers. (CR2504) © Heat Transfer Research, Inc. All rights reserved. Confidential: For HTRI member use only.

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About This Version


More than 10 tube type definitions

The program logic has been modified to handle correctly more than 10 defined tube types. An individual bundle can use no more than 9 types, but if you define and delete multiple tube types, you can create a tube type with an internal number greater than 9, which caused the case to crash. The logic has been modified and this situation no longer causes a problem. This modification corrects HCPA item X ace 4.0-5. (CR2919)

Number of tubepasses field in design run

Previously, when you selected design mode and design tubepasses, the tubepasses on the Geometry Summary, Unit, and Bundle panels were disabled, but those on the Bundle Layout Panel were not. The tubepasses field on the Bundle Layout panel is now correctly disabled in those circumstances. (CR3435)

Version 4.0 Service Pack 3 Nozzle/Support buttons on 3D drawings

The interface buttons on the 3D drawing to enable/disable display of nozzles and supports have been corrected. Previously, these buttons were not functional, and nozzle/support display was toggled with the header button (CR2602).

Version 4.0 Online help for new items on Layout menu

Online help has been updated to include new items on the Layout menu: Show Bundle Information, Show Tube Type Table, and Show Tube Row. (CR18838)

Updated 2D and 3D drawings

The 2D and 3D drawings have been updated to draw units that implement the multiple services option. The drawings now support varying width bundles. (CR1266)

Multiple services option

The Multiple services option has been added. Use this option to run bundles with different geometry and/or process fluids and conditions with the airside fluid run in parallel. X ace then automatically balances the airside pressure drop over the bundles using the air flow rate. X ace also evaluates the fan performance over all bundles, where applicable. (CR166, CR167, CR392, CR1669, CR1793)

Incorrect plenum height on drawings

Previously, the drawings forced plenum heights to at least 3 feet. This restriction has been removed and a value specified in the input or calculated by the calculation engine is respected. (CR1302)

Economizer layout added

The bundle layout tool now supports a new layout type (Convection) for economizer units. This layout produces the type of pass layout used for convection section bundles in a fired heater. (CR1084)

Correct bundle layout drawing text in output reports

The bundle layout drawing on the last page of the Final Results report has been modified to correct the drawing of the text associated with the graphical drawing. Some text was missing while other text was drawn upside-down (CR1252).

Convective Bundle Layout

A new bundle layout type has been added to the X ace interface. The Convective layout option from the X fh component has been added to Xace to allow automatic layout of convective bundles. (CR1897)

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About This Version

Online help for Drawings tab, Project Settings dialog

Online help has updated to explain the new options on the Drawings tab, Project Settings dialog. The options include use of color and graphics control. (CR1847)

Input status no longer shows Modified when certain panels viewed

The input status now shows Modified only when the values on an input panel are modified. It no longer indicates Modified when certain design panels are viewed but not changed. (CR2027)

Specified fields accept more than one digit on Design Geometry panel

On the Design Geometry panel for a Rating or Simulation case, the Specified field no longer loses focus as each digit is entered. (CR2026)

Version 3.0 Service Pack 2 Low-finned tubes copy output to input

The command Copy input to output now correctly sets the tube wall thickness under the finned portion for low-finned tubes. Previously, the value was incorrectly decreased by the fin height. (CR1593)

Diagram of overfin diameter in online help

The diagram of overfin diameter for high-finned tubes in the online help has been corrected. Prior to correction, the overfin diameter was labeled as fin height. (CR1532)

Online help for new items on Layout menu

X ace Online help has been updated to include new items on the Layout menu: Show Tube Type Table, and Show Tube Row. (CR18838)

Version 3.0 Service Pack 1 Online help figure for tube pitch

The figures in X ace Online Help for tube pitch have been updated to reflect staggered and inline tube layouts. (CR1430)

Pressure Drop Monitor help

The online help topic for the Pressure Drop Monitor has been updated to properly indicate that the tubeside flow rate output is reported per tube. (CR1447)

Version 3.0 Enhanced bundle layout capabilities

X ace now always respects your entered value for number of tubes per row. The bundle width is no longer based on tube type 1. The bundle width expands to include your specified number of tubes per row for every tube type. The ability to specify the number of tubes on a per row basis, as opposed to odd and even, has been implemented as a part of this enhancement. Using the bundle layout properties menu, each tube row can have a unique number of tubes. (CR241) © Heat Transfer Research, Inc. All rights reserved. Confidential: For HTRI member use only.

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About This Version


Fan lanes for induced draft units

The interface and calculation engine have been updated to permit you to specify one or more fan lanes in the bundle for induced draft units. The calculations assume that the lane is properly sealed to prevent air bypassing the bundle. (CR242)

Number of tubes in each row

On the Bundle Layout panel, you can now specify the number of tubes in each row. Previously, it was possible to specify the number in odd and even rows only, and all odd and even rows were assumed to have the same tube count. (CR457)

Total separation in header

A new option has been added to the Methods panel to calculate tubeside condensation with total phase separation in the headers between passes. This option represents a worst-case result, allowing the user to do a "what if" check of the final results. (CR601)

Intermediate tube supports

The default for the number of intermediate supports on the Optional geometry panel now correctly shows as Program set. Previously, it indicated None. (CR387)

Temperature conversion on Process panel

Temperatures now convert correctly when you change units on the input item Hot inlet temperature. Previously, if you clicked the units for the hot fluid inlet temperature and converted the value, the outlet temperature converted incorrectly. This update corrects HCPA X ace 2.0-33. (CR483)

HIGHFin tube databank expanded

Additional tubes have been added to the high-finned tube databank (HighFin.bnk). You can access these new tube dimensions by clicking the Load from Databank button on the High Fin panel.(CR1190)

Default fin material

The default fin material for high-finned tubes has been changed to 1040 H14. Previously, it was 1100-annealed. The interface has also been updated to allow any aluminum to be selected as the fin material. This modification corrects HCPA item X ace 2.0-57 (CR1078)

Red outlines corrected for Simulation

In Simulation mode, if all three hot process conditions and cold inlet temperature are specified, the tree view no longer indicates that more information is required. This modification corrects HCPA item X ace 2.0-60. (CR922)

Version 2.0 Service Pack 1 Drag-and-Drop Does Not Copy Louvers

X ace now correctly copies louvers when you use the drag-and-drop option (see How to Merge Input in the How To ... topics in the main X ace Online Help). Previously, louvers were not copied. This modification corrects alert item X ace 2.0-3. (CR101)

Version 2.0 Ammonia-Water Ammonia-water has been added to the Methods panel as one of the condensing options available to users. (QC200202011) Option Twisted Tape Width

Page 186

Twisted tape width has been added to the Tube Internals panel in X ist and the Twisted Tape panel in X ace. Previously, width was not required; tapes were assumed to be as wide as the tube inside diameter. (QC200202007, 200201008, 200202007) © Heat Transfer Research, Inc. All rights reserved. Confidential: For HTRI member use only.


About This Version

Nozzle Data Banks

Nozzle data banks have been added; users can select specific nozzles sized to meet the appropriate standards. Data banks are ASCII text files; users can quickly and easily add other standards for use in HTRI X changer Suite. (QC200203031, 200203061, 200203062, 200206054, 200204, 200206054, 200204027)

Design Case with Fatal Data Check Messages

X ace now handles design cases with fatal data check messages properly. Fatal data check messages sometimes caused the GUI to fail without informing you. (QC200202013)

2D Drawings

X ace now includes a two-dimensional exchanger sketch with a top and front view. The drawing includes structure, walkways, bundle, and fans. (QC200204028, 200206051)

Cocurrent Units

The graphical interface now correctly passes the cocurrent/countercurrent flag to the calculation engine. Before this update, all cases were run as countercurrent if the bundle layout was not specified. (QC200203061)

Vertical Bottom Inlet

The graphical user interface has been updated to pass the Vertical (bottom inlet) selection to the calculation engine. Previously, it passed Vertical (top inlet). (QC20020307, 200205021)


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About This Version


Miscellaneous Version 5.0 Corrupt nozzle figure in online help

The online help has been modified to correct a corrupt figure in the topic Figure of Tubeside Nozzle Types. (CR2664)

Fin/Bare Area Ratio explanation in online help

The online help has been modified to provide a definition of the fin/bare area ratio reported in the Final Report output. (CR2950)

Updated demo spreadsheets

Demo spreadsheets have been updated for Version 5.0 to indicate the correct default location for files. (CR3231)

Version 4.0 Service Pack 3 Multiple Services pressure drop graph

The pressure drop graph on the Multiple Services tab in X ace has been updated to show the Bundle Outside Pressure Drop per bundle. This value is the bundle plus the steam coil pressure drop for each bundle in service. (CR2764)

Version 4.0 Service Pack 2 Updated Xace tutorial help

X ace tutorial help has been updated to indicate that the user should specify 1 in the Number of services, in the steps referring to lines 45 – 47 of the specification sheet. Previously the tutorial indicated that the user should specify 1 for the Number of bays in series. (CR2601)

Version 4.0 Service Pack 1 Online help for tube pitch

The diagram in online help that illustrates the definition of tube pitch contained some inaccuracies. This diagram has been corrected. (CR982)

Version 4.0 Values for fin tip thickness and fin height in highfin.bnk

Fin tip thicknesses for the 100 and 200 series of automatic high fin codes were changed to 0085 inches. Fin heights for the 200 series were changed to 0.608 inches.

Version 3.0 Set internal company name Page 188

The internal company name string of the ACETubeLyt.OCX (Bundle Layout Control) has been set to Heat Transfer Research, Inc. Now users can examine the properties of the OCX file and determine the vendor. (CR558) © Heat Transfer Research, Inc. All rights reserved. Confidential: For HTRI member use only.


About This Version

Version number

The version numbers for all components and the suite have been updated to 3.0. (QC200201020, 200202005, 200201020, 200111025, 200111025, 200203032)

Modification number

The modification number has been updated for issue (CR608).

Expected answers for standard test cases

The built-in answers for the standard test cases have been updated. (CR611)

Crashes in fan manufacturer software

The writes from the fan manufacturer software have been removed. Previously, some of the fan manufacturer software in X ace attempted to write a message when the calculations failed. Because X ace does not support the type of write used, the program crashed. This modification corrects HCPA X ace 2.0-37. (CR679)

Version 2.0 Service Pack 2 Program crash when design case with no solution runs

X ace now properly handles design cases with no solution. Previously, X ace could crash if you ran another case in the same session before you ran the design case with no solution. (CR306)

Correct economizer topic

X ace Online Help was corrected to indicate that X ace allows two-phase fluids on the outside of tubes (except for high and stud-finned). (CR338).

Version 2.0 Service Pack 1 Classic Design Flow Rate

X ace now correctly handles a classic design case when you indicate that the flow rate is to be varied and enter the air flow rate. Previously, X ace used the specified flow rate and did not vary the flow as requested. This modification corrects alert item X ace 2.0-6 (CR137)

Version 2.0 Updates for use in FH

Calculation procedures have been updated to work directly with FH. X ace handles the convection section bundles and the process fluid in the fire box. (QC200110006, 200110011, 200111006, 200201018, 200111019, 200111022, 200112003, 200112006, 200112007, 200112009, 200112015, 200112019, 200112022, 200112025, 200112026, 200201001, 200201006, 200201007, 200201010, 200202001, 200201018, 200201021, 200201026, 200202003, 200202016, 200202021, 200202023, 200202031, 200202035, 200202041, 200203002, 200203008, 200203010, 200203013, 200203015, 200203028, 200203043, 200203045, 200203059, 200203067, 200204010, 200204015, 200204017, 200204020, 200204043, 200204047, 200204050, 200204061, 200205014, 200205028, 200206033, 200206046, 200204039, 200206055)


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About This Version


Version Number

The version numbers for all components and the suite have been updated to 2.0. (QC200201020, 200202005, 200201020, 200111025, 200111025, 200203032)

Internal Test Set Updated

Cases received from users and new research data cases have been incorporated into the program test sets. (QC200110004, 200110005, 200110007, 200110012, 200111009, 200111013, 200112012, 200112024, 200201002,200201006, 200201018, 200204001, 200204046)

User-Specified Heat Release Curve Ignored

X ace now respects your specified heat release curve for air in economizers. X ace 1.0 ignored the component information entered. This update corrects alert item X ace 1.0-5. (QC200111001)

Handling of X ace is now fully compatible with X ist in its handling of the weight fraction vapor. In User Entered some instances, X ace did not respect the temperatures and reset them based on the Weight Fraction specified weight fraction vapor. This update corrects alert item X ace 1.0-15. Vapor (QC200111016) Missing Properties Update

Miscellaneous Corrections

The X ace calculation engine has been updated to determine which missing process conditions need to be calculated based on user process conditions rather than the code used in ACE. As a result of this update, it is possible that X ace will interpret your input differently if the heat duty code specified in ACE was inconsistent with the specified process conditions. When loading cases created with ACE, verify that the omitted process conditions (if any) are the ones you want X ace to calculate for you. (QC200111014) The zeroing procedure for the local common blocks has been updated (QC200202027) The external statements have been corrected to reflect the subroutines needed in the link step properly. (QC200202027)· The input file no longer closes when you load a .DAT file containing a FILE data record. (QC200201009)

Vapor Reynolds Numbers

The arrays have been expanded to allow storage of a vapor Reynolds number for both sides of the exchanger. Previously, only one array was available, causing the Tubeside monitor to have vapor Reynolds number values from the outside fluid. (QC200111008)

Outside Temperature Profile with Mismatched Process Duties

X ace now correctly distributes the outside temperatures when the tubeside duty is not equal to the outside duty. Previously, X ace based the airside temperature profile on the required duty, not the duty of the outside fluid. (QC200203036)

Plenum Height Required Loading Case from ACE

The data loading procedures have been updated to prevent the plenum height/ground clearance from being required when a case created with ACE is loaded. (QC200112022)

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About This Version

Fan Tip Speed for The Moore Company Fans

The fan tip speed printed by the program is now correct for fans from The Moore Company. All other manufacturers’ fans have also been corrected. This update corrects alert item X item X ace 1.0-4. ace 1.0-4.

Bubble Point and Dew Point Entered for Boiling Fluids

The setup of the heat release curve for a boiling coolant from the bubble point and dew point temperature has been corrected. The problem was easily identified when it occurred because the case did not converge. (QC200203066)

Twisted Tape Pressure Drop

The calculation of twisted tape pressure drop has been corrected to use the tube inside diameter rather than the hydraulic diameter. Previous versions underestimated the frictional pressure drop by a factor of 1.6366. (QC200110014)


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About This Version


Physical Properties Version 2.0 Gas Properties Temperature Range Extended

Gas phase properties for the following data bank components have been extended to 2000 K (3552 °R). Vapor viscosity, thermal conductivity, and heat capacity correlations have been updated to predict the properties over the new temperature range. Properties were checked with literature sources, the FH program, and PPDS 2.Updated components: methane, C1 carbon dioxide, CO2 carbon monoxide, CO hydrogen, H nitrogen, N2 oxygen, O2 ethane, C2 propane, C3 n-butane, NC4 n-pentane, NC5 n-hexane, NC6 ethylene, C2E propylene, C3E sulfur dioxide, SO2 argon, Ar hydrogen sulfide, H2S methanol, CH3OH A new componen component, t, carbonyl carbonyl sulfide, sulfide, COS, COS, has also been been added to the databank databank.. This update corrects alert items ACE 3.1-2, and IST 2.0-3. (QC200111007)

Separate Liquid and Vapor Temperature Ranges Supported

The HTRI fluid physical property data bank has been expanded so that you can specify separate temperature limits for the liquid and vapor phases of each component. This update allows the programs to predict high-temperature vapor physical properties more accurately. (QC200111015)

Tube Metal Correlation for Thermal Conductivity

The thermal conductivity correlation constants in HTRITUBE.BNK have been expanded to include a fifth coefficient for thermal conductivity. This update allows accurate prediction of tube metal properties at elevated temperatures for materials commonly used in fired heaters. (QC200112008)

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Tube Metal Thermal Conductivity Update

About This Version

The thermal conductivities of · chrome moly steel (1CR0.5Mo)· low chrome steel (2.25CR1Mo)· med chrome steel (5CR0.5Mo) have been updated based on information in TEMA standards. (QC200112011)

Rectangular Finned Tubes

The finned tube information is correctly handled for rectangular finned tubes. Previously, the program did not correctly identify rectangular finned tubes to the calculation engine, which resulted in a performance calculation for circular fins. (QC200203047)

Entered Bubble Point and Dew Point Temperature

The bubble point and dew point temperatures are now correctly passed to the calculation engine in all cases. Previously, if the heat release curve was entered and input switched to specifying bubble point and dew point temperatures, the program switched the values when passing them to the calculation engine. (QC200203047)


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Program Outputs Version 5.0 Internal Enhancement section added to Final Results

A new section section has has been added to the Final Results report; this this section section describes describes the geometry of any specified internal enhancement (e.g., microfins or twisted tape). (CR3086)

Excessive file size on reports exported to Excel

When you exported some X some X ace reports ace reports to Excel, excessively large file sizes resulted. Reports affected were the Output Summary, Maldistribution, and Stream Properties. The templates for these reports were modified to correct this problem. (CR3313)

Updated Howden fan selection

The Howden fan selection in X in X ace has ace has been updated using code provided by Howden Cooling Fans. (CR3033)

Tubeside velocity on incremental monitors

The average tubeside velocity now displays on the Tubeside Incremental Monitor. (CR2261)

Added items to Xace session Xace session log

Hot/cold fluid coefficient multipliers, high-fin efficiency, and high-fin base thickness have been added to the session log for X for X ace cases. ace cases.

Corrected Xace Corrected Xace zonal values for outside fluid

For X X ace cases ace cases with the hot fluid on the outside, the 3D graphs displayed incorrect values in a portion of the exchanger. This problem has now been corrected. (CR2647)

Number of decimal points for water/steam flow on API 661 report

Decimal points for the water/steam flow rate on the API 661 report are now consistently reported. Previously, the number of decimal digits could vary on the report; answers were unaffected. (CR2599)

Number of tube supports on Final Results

The Final Results now displays 0 for the number of tube supports when you select None for tube supports on the Optional geometry panel. Previously, the program displayed -1 for this scenario. (CR2643)

Fan diameter message for multiple services corrected

Previously, when a multiple services case had more than one bundle in parallel within a service, the program incorrectly calculated the bay width used to generate the messages comparing fan diameter to bay width and bundle area coverage. This issue has been resolved. (CR3141)

Density used in calculating output airside volumetric flow rate and velocity updated

The air density used in calculating output airside volumetric flow rate and velocity is now determined using the HTRI airside density equation as described in the Extended Surfaces Databook. (CR3147)

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About This Version

Version 4.0 Service Pack 3 Fan manufacturer static pressure loss calculations for cases with auxiliary pressure losses

The integrated fan manufacturer predictions for all fan manufacturers now use the correct static pressure loss without regard to user specification of auxiliary pressure losses on the Optional panel. The fan manufacturer code now uses only bundle pressure losses for recommendation of an appropriate fan or appropriate fans. This modification corrects HCPA item X ace 4.0-8. (CR3087)

Version 4.0 Service Pack 1 Tube material temperature limit properly cleared in Xace

X ace no longer issues the following warning message about exceeding the tube material temperature limit:

Incorrect fin material reported for low-finned tubes

For low-finned tubes, X ace now uses the tube material for all calculations. Additionally, the fin material on the output reports the tube material. (CR1981)This item corrects HCPA X ace 4.0-3.

Airside pressure drop corrected on Multiple Services Output Summary

The bundle pressure drop and steam coil pressure drop that X ace uses to calculate total pressure drop on the Multiple Services Output Summary has been corrected. Now X ace uses the pressure drop from the bundle with the highest sum total bundle and steam coil pressure drop. (CR2575)

Driver power corrected for Xace multiple services

The fan driver power for X ace multiple services cases now uses the input total combined fan and drive efficiency from the Fan panel. Previously, the program used the default of 65% in all cases regardless of user input. (CR2584)

"The maximum process temperature is outside the correlational range of the automatic tube material data bank. The tube metal properties were calculated at the temperature limit. For tube metal number XX the temperature limit is XXX F. Temperature limits are available in the HTRI X changer Suite Online Help file for cases where the process inlet temperature is not user specified." (CR2494)

Version 4.0 Fan BHP on API 661 Output

Two values, fan BHP at design temperature and minimum ambient temperature, reported on the API 661 spec sheet have been removed because they did not include fan efficiency. The reported value was the fluid power and not the brake horsepower. This update corrects HCPA item X ace 2.0-61 and X ace 3.0-14. (CR1209)

Units for fan tip clearance on Output Summary

Units for fan tip clearance have been corrected on the Output Summary. The units are correctly reported as inches for the US unit set and millimeters for the SI unit set. This corrects HCPA item X ace 3.0-15. (CR1777).


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Extra zeros on incremental monitors for sensible liquid and vapor coefficients

The incremental monitors no longer print zeros for sensible liquid and vapor coefficient for row zero on the outside; this value is now blank. Additionally, sensible liquid coefficient is blank for all vapor cases, and sensible vapor coefficient is blank for all liquid cases. (CR1250)

Basic design data section in API 661 Spec Sheet

The Basic design data section has been added to the API 661 spec sheet report. (CR1371)

Velocities at standard conditions for economizers with outside fluid that is not air

The standard face velocity, maximum velocity, and volumetric flow no longer print on the Final Results output for economizers with outside fluid that is not air. (CR1729)

Two-phase flow regime maps added

X ace now offers a tubeside flow regime map for all horizontal two-phase cases. For economizers with two-phase flow outside the tubes, the outside fluid flow regime path is also shown if the bundle has low-finned or plain tubes (CR1083).

Cofimco fans now available

X ace now has Cofimco fans available for selection as a fan manufacturer. Selecting either Cofimco or All from the fan manufacturer list on the Fans panel shows all Cofimco fans that meet the requirements of the case (CR1794).

Fluid name description

The allowable length of the fluid name description has been increased. Depending on the output, typically 20 to 24 characters now displayed. You can input up to 60 characters. (CR1723)

Updates to Xace Design view

The outside volumetric flow on the Design view is now reported in the correct units. Additionally, the Design view now has both extended and bare outside coefficients, and outside pressure drop is available in both airside and economizer unit sets. (CR1672)

Changed title of Fan power on Input Summary report

The title Fan power on the Input Summary report was changed to the more accurate Driver power. This change is in title only; the value remains unchanged (CR1827).

Static pressure drop on reports

On the X ace Final Results and Output Summary, the static pressure drop label was changed to bundle pressure drop. This value now prints for all cases. (CR657)

Add header design messages from ISO 13706

Messages have been added to X ace if the header dimensions are lower than recommended in 7.1.6.1.4 and 7.1.6.1.5 in the ISO 13706 standard. (CR1196)

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About This Version

Add column to Xace Session and Design grids

X ace Design and Session views now report Outside pressure loss in airside units, Pa (in H2O) and outside pressure units, kPa (psi). Turn columns on or off as desired (CR1590)

Fan speed in SI units

The fan speed is now correctly displayed in SI and MKH units. It was previously converted as a velocity. (CR1689)

New output summary report for Xace multiple services

X ace generates a new output summary report for multiple services cases. This report contains summary information for the bay, fan manufacturer information (if requested), and summary results for each bundle. (CR1340)

Added cost factor to Final Results

A cost factor has been added to the Final Results output for use in comparing relative costs of exchangers. This value is not the actual cost of the exchanger; it is only for comparison purposes. (CR1411)

Methods panel items appearing as Name panel items on Input Reprint

Some items from the Methods input panel were printing to the Name panel list in the Input Reprint report. This problem has been corrected. (CR1946)

Informative weight messages removed

The informative messages printed for cases in which exchanger data were outside the weight data in the weight bnk files have been removed per user request. Because the weight calculation was intended to be an estimation, these messages are not necessary.

Black cells appearing on Output Reports

Some cells in the output report spreadsheets were filled with white, which caused then to print as black-filled cells in some instances. This problem has been corrected. (CR2241)

Version 3.0 Service Pack 2 Values on Xace Output Summary moved

In previous versions of X ace, the locations of velocity pressure and static pressure on the Output Summary report appeared to indicate that these values were at standard rather than actual conditions. To prevent confusion, the velocity pressure and static pressure have been moved; they now appear beneath the Actual column. (CR1527)

Tube types on Output Summary and Final Results

If you change a high-finned tube to a plain tube, the Output Summary and Final Results print only the plain tube information. This update corrects HCPA item X ace 3.0-13. (CR1473).

Setting of number of bays in parallel on Session Output

The Session tab now shows the correct number of bays for each selection even if multiple bays have been selected. This update corrects HCPA item X ace 3.0-11. (CR1570)


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Version 3.0 Service Pack 1 API 661 with French language settings

On the API 661 specification sheet, the formulas used to display the values for the vapor flow rates now work properly if the language settings are French. Previously, an error occurred when the flow rates were output. This corrects HCPA item X ace 3.0-6. (CR1355)

Duty messages changed to print total duty

X ace now multiplies duty in the following messages by the number of bundles and bays in parallel, thus printing the total duty: 1

Duty calculated from the hot fluid process conditions is \&&&&&&& MW (|&&&&&&& M Btu/hr).

2

Duty calculated from the cold fluid process conditions is \&&&&&&& MW (|&&&&&&& M Btu/hr).

3

Specified heat duty is \&&&&&&& MW (|&&&&&&& M Btu/hr). (4088)

4

Required heat duty is \&&&&&&& MW (|&&&&&&& M Btu/hr). The percent overdesign is based on this value.

(CR1381)

Version 3.0 Tubeside film boiling messages

The correct message is not printed when the film boiling calculation fails to converge. Previously, the nucleate message was incorrectly printed. The tubeside boiling film boiling messages were also simplified when film boiling is present in the exchanger. (CR1212)

Percent pressure drop in tubeside nozzles added to data base output (.dbo) file

The total calculated tubeside nozzle pressure drop, expressed as a fraction of the total nozzle tubeside pressure drop, has been added to the data base output file for X ace as item 147. Previously, this value was not output by X ace.

Outside Monitor sensible liquid coefficient for shellside condensation

The shellside liquid coefficient in the two-phase zone of an outside condenser is now printed properly. Previously, it was not zeroed correctly, so that misleading values were output on the monitor. The appropriate value was used internally. Note that the sensible liquid coefficient in the two-phase zone is calculated only in gravity-controlled flow and then only at high liquid loading. (CR475)

Design pressure on API 661 output

Units on the API 661 specification have been changed to indicate that the design pressure is in gauge pressure. Previously, the units were indicated as absolute. (CR400)

Units for static pressure on API 661 Spec Sheet

The units for static pressure drop on the API 661 specification sheet are now indicated as Pa. Previously, the value was output in Pa, but the units were labeled kPa. This update corrects HCPA X ace 2.0-35. (CR658)

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To find out more about the database output file, open X changer Suite Help, click Reference Information, and then click Common Database Output Files. (CR778)



About This Version

Flow regime for two-phase shellside and twophase shellside, single-phase tubeside cases

The flow regime parameter now displays on the Tubeside Monitor for two-phase shellside, single-phase tubeside cases. The flow regime also appears on the Outside Monitor for two-phase boiling cases. This update corrects HCPA X ace 2.036. (CR538)

Sensible gas coefficient printout for tubeside condensation

The tubeside sensible gas coefficient is now available on the Tubeside Monitor for condensation cases. It previously was not output when the outside fluid was single-phase. There were no problems in the internal calculation; only the report was incorrect. (CR618)

Airside coefficient on summary output; vaporphase heat transfer coefficient on Tubeside Monitor

The average overall airside coefficient on the summary output is now based on the extended area. It was previously based on the bare area. The vapor-phase heat transfer coefficient on the Tubeside Monitor is now correctly based on the inside surface area. Previously, it was based on the outside area. This update corrects HCPA X ace 2.0-40. (CR717)

Page count overflow on output reports

For exchangers with a very large number of tubepasses (e.g., >100), the Tubeside and Outside Monitors can exceed the maximum number of pages (255) that can be displayed. Previously, X ace output as many pages as it could, but the first page was incomplete. A warning dialog has been added to indicate when the maximum number of pages has been exceeded, and the first page display has been corrected. (CR720)

API 661 Spec Sheet Export to ® Microsoft Excel

X ace’s API 661 Spec Sheet now exports to Microsoft Excel without sending an error message. Previously the report used merged cells that were not supported in the Microsoft Excel 95 file format. The report no longer uses the merged cells. This update corrects HCPA X ace 2.0-42. (CR412)

Total shellside pressure drop in database output file

In the database output file, the value for the total shellside pressure drop (line 135) is now correct. In X ace 2.0 Service Pack 2, it was too low by a factor of 27.68. This update corrects HCPA X ace 2.0-44. (CR770)

Units on API 661 spec sheet reflect SI units for horsepower

The horsepower fields on the API 661 Specification Sheet now show SI and MKH units also. This update corrects HCPA X ace 2.0-46. (CR839) SI and MKH Units (New)

US Units (Existing)

• KW@design temp.

• BHP@design temp.

• KW@min. ambient temp.

• BHP@min. ambient

• Driver KW

• Driver hp


temp.

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Database (.DBO) file corrections


The following database output file (.DBO) are now correctly output (CR1005): 223

value for fin to bare area ratio corrected

137

value for frictional pressure drop corrected

013

determination of calculation mode corrected

230

value for tube wall thickness corrected

047, 048

root diameter and finned wall thickness no longer for plain tubes

243, 244, 500 fan area per face area, fin tip clearance fan ring type now printed from GUI dbo file for natural draft cases 017

value for tube type has been corrected

This update corrects HCPA X ace 2.0-49. Boiling convective X ace now displays nucleate and convective boiling coefficients for falling film and nucleate cases on the Tubeside Monitor. (CR375) coefficients added to monitors for falling film cases No data from disabled fan fields on reports

If you run a case with no fans, the disabled (grayed out) data from the Fans panel is no longer displayed on the reports. (CR1011)

Structure on drawing for economizer bundles

The drawing for economizer bundles shows only the bundle. Previously, parts of the air cooler structure were included on the drawing. (CR1045)

No data from When you run a case with no fans, the disabled (grayed out) data from the Fans disabled fan fields input panel no longer displays on reports. This modification corrects HCPA item X ace 2.0-52. (CR1011) on reports Fan manufacturer information properly cleared between runs

Fan manufacturer information on the Final Results output no longer appears when you select no fans. Previously, if any fan information had been included in the session, it appeared on the output for the new case. (CR1080)

Warning message X ace now issues a warning message if you enter heat release or physical property for thermosiphons data and the entered pressures do not span the operating pressure of a two-phase fluid. If this message is generated in a case, please carefully verify the results; with insufficient property extrapolation must be used carefully in two-phase regions.(CR1105) property profiles Report headers on fatal input errors

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The output routines were modified to set the program version number properly in the event of a fatal input error. Prior to this correction, X ace exited before setting the version number, which caused the program to report a version of 0.00 when it detected a fatal input error. (CR1191)



About This Version

Xace Online Help for outside and tubeside monitors

The online help topics that define bulk temperature, pressure, and weight fraction vapor on the outside and tubeside monitors now indicate values as being at the beginning of the increment. This modification corrects HCPA item X ace 2.0-59. (CR1199)

Text overlap on 2D exchanger drawing

The font size on the 2D exchanger drawing is now automatically sized to prevent overlap of text for the different exchanger annotations. (CR521)

Date on specification sheet

The date the case was run now prints on the API 661 Specification Sheet output. (CR1033)

Version 2.0 Service Pack 2 Corrected noise PWL

The noise PWL, given in dbA on the Final Results, has been corrected in SI and MKH units. Previously, it was treated as if it had units and converted to incorrect values.

Drawing for economizers

The 2D drawing has been updated so that no exostructure appears on economizers. Previously, part of the structure for an air-cooled heat exchanger was incorrectly included on an economizer drawing. This update corrects HCPA X ace 2.0-25. (CR234)

Estimation of fan weight

Fan weight estimation has been changed to consider number of fans as per bay rather than per bundle. This update corrects X ace 2.0-26. (CR180)

Implementation of warning messages

X ace now properly determines when to issue the following messages: 1 A

differential flash is recommended for two-tubepass intube condensation unless a U-tube bundle is used because of potential phase separation in the header.

2

Film boiling has been predicted in at least one increment on the tube side. To confirm, check side profile for increments in film boiling, and note local wall temperatures to assure they are acceptable.

3 An

internal temperature cross exists in the exchanger. The program handles the reverse heat flow properly in the calculations, but you may want to consider changing the terminal process conditions to avoid the internal temperature cross.

This update corrects HCPA X ace 2.0-48. (CR411) Writing of condensing and boiling coefficients to Monitors

Updated writing of condensing and boiling coefficients to Monitors so that they reflect values from the incremental calculations accurately. This update corrects HCPA X ace 2.0-29. (CR243)


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Added nonconvergence message


During convergence, X ace can increase convergence tolerance if the case is not converging. In most cases, the converged solution is valid. However, in some cases, the final solution, although converged as tightly as possible, is not adequately converged. Although these cases can be identified by checking the duty ratio on the 3D plot, the following message has been added to alert you: "Based on the standard deviation of the Duty Ratio in each increment, the case may not be converged properly. Nonconvergence usually results from an incorrect bundle layout, such as a case with only one or two tubes in a pass on one or more of the rows. The duty ratio is the assumed duty divided by the calculated duty in each increment; the values should be approximately the same for all increments in the exchanger if the case is properly converged. To check convergence after the case has run, 1

Click the Graphs tab.

2

Select Output 3D Profiles.

3

Plot the Duty Ratio.

If the values in the plot are not within 10%, the case has not converged properly. Check the bundle layout to ensure that the tubes in the unit are properly positioned; the Equal count bundle layout option may result in an unrealistic bundle geometry. If the unit layout is not as you intended, correct the bundle and run the case again. If you receive this message and the unit is as you intended, do not use the results. Instead, please e-mail the case to [email protected] for analysis." The likelihood of encountering this message is relatively remote; in the entire X ace test set of more than 6000 cases, fewer than 200 do not converge adequately. This modification corrects HCPA X ace 2.0-43. (CR185) Outside allowable pressure drop SI and MKH units for economizers

The Final Results now correctly reports allowable pressure drop for economizers if you run the case in SI or MKH units. Previously, the value reported was 27.68 times larger than the value entered. This reporting problem did not influence any of the calculated results. This modification corrects HCPA X ace 2.0-30. (CR419)

Standard answers update

The results to the standard test set were updated for the X ace self-test. (CR451)

Version 2.0 Service Pack 1 Zero Lengths in Tubeside Monitor and Incorrect Graphs with Length from Inlet as x-Axis

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The lengths from the inlet on the Tubeside Monitor are now correct. Previously, the values always printed as zero. Because these lengths are used as the values in plots from the inlet of the exchangers, those graphs also work properly now. This modification corrects alert item X ace 2.0-4. (CR105)



About This Version

Extended Surface Area on Wide Final Results

The extended surface area for the unit on the wide Final Results now correctly reflects the area for all bundles in all bays. Previously, the value printed on the wide results was for one bundle only. The narrow Final Results and Output Summary are correct. This modification corrects alert item X ace 2.0-7. (CR107)

Transfer Rates on API Specification Sheet

The overall coefficients are now correctly output for the "Transfer rate finned" and "Bare tube, service" coefficients on the API 661 sheet. Previously, these values were for the air film coefficient. This modification corrects alert item X ace 2.0-11. (CR123)

Tubeside Volumes X ace now correctly gives the tubeside volume in liters. Previously, the value was reported as liters but printed in cubic meters. This modification corrects in SI Units alert item X ace 2.0-9. (CR149) Winter Fan Power

The winter fan power is now based on a constant air flow volume as in previous version of X ace and ACE. In X ace 2.0, the value was based on constant mass flow. This modification corrects alert item X ace 2.0-10. (CR150)

Bundle Weight and Volume for UTubes

The bundle weight and tubeside volume are now correct for U-tubes. Previously, the value was too large because it treated the extra length in Ubends incorrectly. This modification corrects alert item X ace 2.0-12. (CR156)

Minimum and Maximum Temperatures

X ace now correctly formats zero degrees for the minimum and maximum temperatures on the Final Results. Previously, a value such as 2.133e-3 C could print incorrectly. (CR173)

Version 2.0 Summary Output Updated

The following items have been added to the Output Summary report for X ace: 1. Fluid name 2. Fluid condition 3. Inlet/Outlet velocity 4. Heat transfer safety factor 5. Tube ID 6. Number of odd/even tubes 7. Tube material 8. Fin efficiency 9. Over-fin diameter (QC200203011)


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Additional Monitor Outputs


The following items have been added to the Outside monitor: 1. Fin tip temperature 2. Sensible liquid coefficient 3. Sensible vapor coefficient 4. Boiling thin film coefficient 5. Convective boiling coefficient The following items have been added to the Tubeside monitor:· Sensible liquid coefficient Sensible vapor coefficient Boiling thin film coefficient Convective boiling coefficient The maximum fin tip temperature has also been added to the Final Results. These modifications correct alert item X ace 1.0-8. (QC200201023, 200203011, 200203068)

Minimum and Maximum Wall Temperatures

Minimum and maximum wall temperatures inside the fouling layer have been added to the Final Results and monitor reports. (QC200203022, 200204002)

Water and Noncondensables Flow Rates

Flow rates of water and noncondensables have been added to the specification sheet printout and database output file. (QC200203006, 200203027, 200202034, 200202030, 200201026)

Minimum and Maximum Fin Tip Temperatures

Minimum and maximum fin temperature temperatures are now calculated and reported on the Final Results. (QC200201023, 200201025)

Database Output File

Several database output items have been corrected:· Steam/water flow shellside (Item 73) Steam/water flow tubeside (item 73) Area ratio (item 223) Fin efficiency (item 241) Fan area over face area (item 243) Fan tip clearance (item 244) Fan ring type (item 500) This update corrects alert item ACE 1.0-18. (QC200201026)

Duty Multiplier on Spec Sheet Outputs

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Your entered duty multiplier has been added to the Specification Sheet outputs in the Comments section. (QC200203072)



Composition Profile on Input Data Reprint

About This Version

The composition profile is now included as a part of the Input Data Reprint. (QC200203072)


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Single-Phase Methods Version 5.0 Airside row correction factor

The overall row correction factor used in previous versions of X ace and ACE has been implemented again in X ace. The method is described in report AC-10. The method that was removed, described in report AC-12, incorrectly penalized the airside heat transfer coefficient by 4 to 7 percent for bundles with more than one row. This item corrects HCPA X ace 4.0-4. (CR2669)

Internal microfin option added

Using methods developed by Dr. John Thome and currently available in the EHT software distributed by HTRI, single-phase internal microfins methods have been added to X ace. (CR3085)

Version 3.0 Implementation of AC-12 methods for pressure drop and heat transfer

Incremental row correction factors have been implemented to replace the previous version that used overall correlations.

Twisted tapes in laminar flow

The laminar heat transfer method for tubes with twisted tape inserts has been updated. As a result, heat transfer coefficients predicted for twisted tapes in the laminar region will be up to about 30 percent higher depending on the physical properties of the fluid and the Reynolds number. The previous method was 30 to 35 percent too conservative for fluids with operating Prandtl numbers greater than about 200. The modification, which is supported by additional data, gives less conservative, more theoretically based results and covers Prandtl numbers up to over 8000. (CR424)

Version 2.0 Twisted Tape Single-Phase Methods

New methods for single-phase flow over twisted tapes have been developed and implemented, dramatically improving prediction of the pressure drop for single-phase flow. The new methods are documented in HTRI Report TE-4 (2002). In summary, Heat transfer is enhanced by about 16 to 40 percent, and pressure drop increases about 1.5 to 3.0 times for intube single-phase flow using twisted tapes over a wide range of turbulent flow conditions. The new heat transfer and pressure drop methods predict intube singlephase flow data (gas or liquid) well using twisted tape inserts. All predictions fall within ± 20 percent of calculated-to-measured heat transfer and pressure drop values. In addition, a wall temperature correction has been added to the methods from TE-4.This modification corrects alert items X ace 1.0-1 and X ace 1.0-2. (QC200202033)

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Lymer-Ridal Fin Efficiency Correction

About This Version

X ace now bypasses the Lymer-Ridal fin efficiency correction for thin steel fins. The fin efficiency for thin steel fins increases slightly based on this change, typically 4 to 12 percent. Thin fins are those having thickness less than 1 mm, 0.04 in. This change is based on field data. (QC200203030)


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About This Version



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About This Version

Glossary A annular distributor: A cylinder of diameter larger than the shell, used to help distribute fluid into shell side of exchanger. Fluid enters larger cylinder through a nozzle, flows around outside shell, and enters shell through evenly distributed slots cut into shell well. Sometimes called a vapor belt. auto straight-line: The ability to generate a straight-line heat release curve when you specify inlet and outlet temperatures and fraction vapors for a fluid. Both fraction vapors must be between 0.001 and 0.999.

B baffle-to-shell clearance: Diametric distance between baffle outside diameter and shell inside diameter. baffle cut: For single-segmental baffles, segment opening height expressed as percentage of shell inside diameter. For double- and triple-segmental baffles, defined as segment height of innermost (center) baffle as percent of shell inside diameter. baffle cut orientation: Relationship of baffle cut to centerline of inlet nozzle, can be parallel or perpendicular to centerline. Used to provide orientation description that is independent of shell orientation. For horizontal shell with inlet nozzle on top or bottom of shell, perpendicular is the same as horizontal cut baffles and parallel is the same as vertical cut baffles. baffle type: Common baffle types are single-segmental, double-segmental, triple-segmental, and rod. bundle: Tube bundle of exchanger, consists of tubes, baffles, supports, tie rods, spacers, and tubesheets. bundle-to-shell clearance: Diametric distance between outer tube limit and shell inside diameter.

C central baffle spacing: Distance from center of one baffle to center of next baffle. clean heat transfer coefficient: Predicted overall rate at which heat is transferred from hot fluid on one side of exchanger to cold fluid on other side, with zero fouling resistance. corbel: A projection from the refractory wall that prevents flue gas from bypassing convection section tubes. cross baffle: Metal plate placed in bundle to alter flow pattern of shellside fluid flow.

D detuning plate: Metal plate attached to bundle to change acoustic resonance frequencies within bundle. dirty heat transfer coefficient: Predicted overall rate at which heat is transferred from hot fluid on one side of exchanger to cold fluid on other side, with specified fouling. dry weight: Weight of heat exchanger when empty.

E effective area: Total tube outside surface area (including finned area) available for heat transfer. Surface area covered by tubesheets is not included in this area. effective mean temperature difference: Average temperature difference between shellside and tubeside fluids. This value is a measure of average driving force for heat transfer. effective tube length: Effective heat transfer length of heat exchanger's tubes; does not include tube length projecting from tubesheet(s) or tube length contained inside tubesheet(s). emissivity: A hypothetical black body emits radiation at a rate proportional to the fourth power of the absolute temperature of the body. Actual surfaces emit radiation at a somewhat lesser rate. The emissivity is the ratio of the actual emissivity to that of a black body. end partition plate: Metal plate in front and/or rear heads used to partition heads for multiple tubepasses. expansion joint: Cylindrical device located in shell cylinder of fixed tubesheet exchangers; designed to relieve stress caused by difference in expansion or contraction of tube and shell materials resulting from temperature or pressure. © Heat Transfer Research, Inc. All rights reserved. Confidential: For HTRI member use only.

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About This Version


extinction coefficient: A measure of the ability of particles or gases to absorb and scatter photons from a beam of light; a number that is proportional to the number of photons removed from the sight path per unit length.

F fin area per unit length: Finned tube surface area per unit length of heat exchanger tube. fin pitch: Distance between adjacent fins, center to center.

H height under nozzle: Distance between shell inside diameters and edge of first tuberow beneath nozzle. hot fluid allocation: Location of hot fluid, shell side or tube side.

I impingement protection: Flow distribution device used to protect tube bundle from damage due to excessive velocities or twophase flow in the nozzles. impingement rods: Rods placed below the shell inlet nozzle to prevent impingement of fluid directly onto tubes. Typically, rods are of same size and layout as bundle tubes. inclination angle: Departure of exchanger shell from horizontal, measured in degrees. Vertical shell has inclination angle of 90°. Shells are sometimes inclined slightly to promote condensate drainage. inlet baffle spacing: Distance between tubesheet (or support plate) and first baffle where shellside flow enters exchanger.

L layout angle: Layout of tubes in relation to direction of shell side crossflow. Given in degrees. Commonly used layout angles are 30°, 45°. 60°, and 90°. longitudinal baffle: Metal plates within a heat exchanger that are parallel to the tubes. Used to direct fluid flow in desired flow pattern. Longitudinal baffles are present in TEMA F, G, and H shells. longitudinal tube pitch: Tube center-to-center distance between adjacent tuberows in the direction of shellside flow.

M mean beam length: The length of a beam that, if directed at right angles to the walls of the firebox, would have the same effect as the average of all beams directed to the walls at their respective angles.

N no-tubes-in-window: Exchanger with all tubes removed from baffle windows. This type of exchanger is commonly used to prevent flow-induced tube vibration problems. nozzle: Physical opening for fluid to enter or exit heat exchanger. nozzle dome: Enlarged nozzle neck used to reduce velocity of fluid entering exchanger and to aid distribution of fluid inside heat exchanger. number of shell passes: Number of times shellside flow travels all or part of shell longitudinally. For example, TEMA types F and G shells have 2 passes, and TEMA type H has 4 passes.

O outer tube limit: Diameter of circle beyond which no tubes can be placed in the tubesheet. outlet baffle spacing: Distance between tubesheet and last baffle at point where shellside flow exits exchanger. outside area per unit length: Actual outside area of tube plus external fin surface area per unit length of tube. outside/inside area ratio: Ratio of outside surface area to inside surface area of tube.

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overdesign: A theoretical indication of the feasibility of the exchanger design, given in percent. It indicates the amount of extra area the design has for indicated process conditions. A negative value for overdesign indicates that the exchanger is too small for the specified process. A value near zero indicates a close match of process conditions and exchanger area design.

P partition seal rod: Rod connecting two baffles, located in the pass partition lane to decrease the shellside fluid flowing through the pass partition lane. passlane: An opening lane between tubepasses.

R root diameter: Outside diameter of tube at base of the fin for external finned tube.

S seal strips: Devices (typically rectangular strips) placed in the circumferential bypass space between tube bundle and shell. Seal strips force fluid from the bypass (C) stream back into the bundle. shell: That portion of the exchanger (typically from tubesheet to tubesheet) that encloses the tube bundle. skid bars: Guide bars attached to bundle to assist insertion of bundle into shell. slot area: The total cross-sectional area of all slots cut in the shell wall for an annular distributor.

T TEMA shell type: The three-letter designation (e.g., AES) that describes the front head, shell style, and rear head, respectively, of a shell-and-tube heat exchanger. thermal resistance: Measure of material's ability to prevent heat from flowing through it, equal to difference between temperatures of opposite faces of body divided by rate of heat flow. thermosiphon piping: All inlet and outlet piping pertaining to thermosiphon reboiler system. tie rod: Device used to hold baffles in place during construction. One of several rods located at various points around periphery of bundle that run from front tubesheet to last baffle. tie rod spacers: Tube or pipe material with inside diameter greater than tie rod diameter and outside diameter greater than baffle tie rod holes. Spacers slide over tie rods. transverse tube pitch: Distance between tube row centerlines perpendicular to shellside fluid flow. tube-to-baffle clearance: Diametric distance between hole in baffle for tube and tube outside diameter. tubepass layout type: For bundles with more than 1 tubepass, specifies arrangement of tubepasses within bundle. Xist allows 1, 2, 3, 4, 6, 8, 10, 12, 14, or 16 tubepasses in the exchanger bundle. Common types are quadrant, boxed or h-bonded, and ribbon. tubesheet: Sheet of metal located between heads and shell to maintain separation of shellside and tubeside fluids. Perforated with tubes to permit tubeside fluid passage through shell.

U U-bend support: Full baffle placed at or before the tangent to support the bundle. Also, straps of metal inserted in the bundle to support the U-bend region.

W wall temperature: Temperature at interface between fluid and tube or surface of fouling layer, if present. wet weight: Weight of heat exchanger when full of water.


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Index

Index A

Bundle Summary ........................................... 118

About This Version.........................................165

Bundle width .................................................... 27

Absolute pressure tolerance ..........................103

Bundle width - Maximum ................................. 68

Absolute temperature tolerance.....................103

Bundle width - Minimum ..................................68

Add button........................................................30

Bundle width - Specified ..................................68

Add non-nucleate boiling components to this curve.............................................................99

Bundle width - Step Size..................................69 Bundle width checkbox ....................................67

Additional unheated tube length ......................29 C Air-cooler single increment...............................91 Calculation Procedures..................................169 Airside flow rate units .......................................61 CAPE-OPEN Panel .......................................102 Airside Pressure Drop............................112, 131 Case description .............................................. 81 Airside Pressure Drop %................................116 Case Mode.........................................................4 Airside Velocities............................................111 Check any blocked sides .................................83 Allowable pressure drop...................................63 Check film boiling.............................................88 API 661 Spec Sheet.......................................139 Clearance wall to first tube .............................28 Average Coefficients......................................123 Cold fluid coefficient multiplier.........................97 B Cold sensible liquid coefficient.........................95 Bank fin code ...................................................42 Cold sensible vapor coefficient........................95 Bank Fin Codes................................................43 Condensable Components ..............................86 Boiling coefficient .............................................95 Condensation method......................................86 Boiling method .................................................89 Condensing coefficient .................................... 95 Boiling method components.............................90 Condensing Methods.....................................177 Boiling Methods..............................................166 Constant A for film boiling curve....................100 Bundle Information.........................................132 Constant A for nucleate boiling curve.............. 99 Bundle Layout panel ........................................53 Control input panel group ................................80 Bundle Layout Tube Information......................54 Convergence panel........................................101 Bundle panel ....................................................24 © Heat Transfer Research, Inc. All rights reserved. Confidential: For HTRI member use only.

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Index


Critical heat flux................................................96

Diagram of Fan Ring Types............................. 16

D

Diagram of Fin Measurements ........................47

Data Check Messages ...................................118

Diagram of Flow Maldistribution ...................... 82

Data Input and Data Check............................180

Diagram of forced draft unit ground clearance 23

Databank type ..................................................49

Diagram of Fouling Resistance vs. Layer Thickness ..................................................... 64

Default bundle type ..........................................24 Default number of pressure sets....................104

Diagram of induced draft unit ground clearance .....................................................................23

Default number temperature points in each pressure set................................................104

Diagram of Micro-fin Tube Insert .....................39 Diagram of Plenum Height...............................58

Delete button....................................................30 Diagram of Plenum Height Forced Draft Units58 Design Constraints panel.................................78 Design Geometry panel ...................................67 Design input panel group .................................66 Design Mode Control - Classic ........................77 Design Mode Control - Grid .............................77 Design Mode Control - Rating..........................78 Design Mode Control - Simulation ...................78 Design pressure...............................................21 Design temperature..........................................22 Design Warnings panel....................................80 Dew point temperature.....................................19 Diagram of Air-Cooled Exchanger Dimensions19 Diagram of Blocked Sides................................84 Diagram of Bundle Layout Choices .................25 Diagram of Bundle Width.................................28

Diagram of Plenum Height Induced Draft Units .....................................................................59 Diagram of Rectangular and Plate Continuous Fin ................................................................44 Diagram of Serrated Fin ..................................44 Diagram of Tube Layouts ................................27 Diagram of Tube Pitches .................................34 Diagram of Tubes in Odd/Even Rows .............26 Diagram of Tubeside Nozzle Types.................11 Dialog Box Fin Geometry for High-Finned Tubes ...........................................................42 Duty/flow multiplier...........................................66 E Entry type/ Exit type .........................................11 Equilateral layout .............................................32

Diagram of Circular Fin ....................................44

Equivalent tube length in tube bends for U-tubes .....................................................................29

Diagram of Cocurrent Flow ................................9

Exchanger duty................................................66

Diagram of Countercurrent Flow........................9

Exchanger Performance................................ 108

Diagram of Fan Arrangements...........................7

Exchanger Weights........................................117

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Index

Explanation of Items on Outside/Tubeside ....134

Fin material......................................................45

Exponent B for film boiling curve ...................100

Fin material thermal conductivity .....................46

Exponent B for nucleate boiling curve .............99

Fin root diameter..............................................50

F

Fin thickness..............................................40, 50

f- and j-Curves page.........................................36

Fin tip thickness ...............................................45

Face velocity - Maximum .................................71

Fin type ............................................................43

Face velocity - Minimum ..................................71

Final Results ..................................................120

Face velocity - Specified ..................................70

Fins per unit length ..........................................50

Face velocity - Step Size..................................71

Flow Maldistribution panel ...............................81

Face velocity checkbox ....................................70

Flow rates ........................................................62

Fan area blockage ...........................................17

Flow type............................................................8

Fan Arrangement ...............................................7

Fluid name .......................................................61

Fan Description and Fan Power ....................128

Fluid phase ...................................................... 61

Fan diameter ....................................................14

Force phase separation in tube headers .........91

Fan Geometry ........................................110, 116

Fouling layer thickness ....................................64

Fan manufacturer.............................................14

Fouling resistance............................................63

Fan Manufacturers .........................................117

Fraction of critical flux for film boiling...............97

Fan ring type ....................................................16

Free area in fan guard .....................................18

Fan shaft lane width .........................................15

Free area in hail screen................................... 18

Fans panel .......................................................13

Frequently Asked Questions..........................162

Fin apex angle..................................................41

G

Fin base thickness ...........................................45

Geometry input panel group ..............................5

Fin bond resistance..........................................46

Graphical Bundle Layout ...............................132

Fin density........................................................45

Graphical Interface.........................................183

Fin efficiency ....................................................46

Ground clearance to fan blade ........................22

Fin Geometry .................................................111

H

Fin height....................................................40, 50

Header box depth ............................................19

Fin helix angle ..................................................41

Header box height............................................20


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Header box plate thickness..............................20

Local wall temperature...................................102

Header box width .............................................20

Longitudinal pitch.............................................33

Heat Release Profile ......................................141

Longitudinal pitch - Maximum .......................... 72

Heat Transfer and Pressure Drop Parameters ....................................................................129

Longitudinal pitch - Minimum........................... 72 Longitudinal pitch - Specified...........................72

Height of rectangular section ...........................48 Longitudinal pitch - Step Size ..........................72 High fin tube heat transfer method...................91 Longitudinal pitch checkbox.............................72 High fin tube pressure drop method.................92 Louvers present ...............................................18 High Fins page .................................................41 Low Fins page..................................................48 Hot fluid coefficient multiplier ...........................97 M Hot fluid location.................................................7 Maldistribution control......................................82 Hot sensible liquid coefficient...........................94 Maldistribution Monitor...................................143 Hot sensible vapor coefficient ..........................94 Maldistribution profile values ...........................82 HTRI Research Geometry................................92 Maximum Airside Velocities...........................116 I Maximum ambient temperature .......................19 Inlet Airside Velocities....................................128 Inlet fraction vapor............................................62

Maximum number of pressure-properties trials ...................................................................102

Inlet pressure ...................................................63

Maximum sound pressure level....................... 15

Inlet temperature..............................................62

Maximum tube wall temperature......................80

Input Panels .......................................................3

Mean Metal Temperatures.............................132

Input Reprint...................................................144

Messages....................................................... 125

Input Summary panel.........................................4

Methods panel .................................................85

L

Micro-fin page ..................................................39

L/D 360-degree twist........................................38

Minimum ambient temperature........................ 19

Legend Details .................................................54

Minimum tube wall temperature.......................80

Liquid Mole Fraction.......................................142

Miscellaneous ................................................188

Liquid Properties ............................................141

Miscellaneous Physical Property Factors...... 141

Load from Databank button........................42, 48

Mole fraction noncondensables.......................88

Load from Databank Dialog Box ......................49

Momentum recovery to include........................88

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Index

N

Overall Exchanger Performance....................115

Natural Draft panel...........................................55

Overall heat transfer ......................................101

Nozzle database ..............................................10

Overall Performance Data .............................125

Number of bays in parallel per unit ....................9

Overall pressure drop ....................................101

Number of bundles in parallel per bay ...............9

Over-fin diameter .............................................47

Number of fan shaft lanes per bundle..............15

P

Number of fans per bay....................................13

Passes for Rows with Defined Passes Bundle Type Grid......................................................29

Number of fins..................................................40 Physical Properties ........................................192 Number of intermediate tube supports.............21 Plenum chamber type ......................................22 Number of nozzles per bundle Inlet ................12 Plenum height..................................................57 Number of nozzles per bundle Outlet .............12 Plenum length..................................................57 Number of services ..........................................10 Plenum width ...................................................57 Number of stud rings........................................51 Pressure drop allowed in inlet nozzles ............79 Number of studs in each ring ...........................52 Pressure drop allowed in outlet nozzles..........79 Number of tubepasses per bundle...................10 Pressure Drop Monitor...................................137 Number of tuberows.........................................25 Problem description .........................................81 O Process Conditions........................................108 Optional panel ..................................................17 Process Data .................................................122 Outlet fraction vapor.........................................62 Process input panel .........................................59 Outlet temperature ...........................................63 Program Outputs............................................194 Output Summary ............................................107 Property Monitor ............................................140 Output Summary for Multiple Services ..........113 Pure component boiling ................................... 88 Outside area/length..........................................51 Pure component condensation........................ 85 Outside friction factor method ..........................85 R Outside friction factor multiplier........................98 Radial fan tip clearance ...................................14 Outside Monitor..............................................132 Recovery chimney height ...............................57 Outside Process Conditions...........................115 Recovery chimney length ...............................56 Outside/Airside f- and j-factors.........................37 Recovery chimney width.................................56 © Heat Transfer Research, Inc. All rights reserved. Confidential: For HTRI member use only.

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Index


Reference pressure for nucleate boiling curve 98

Transverse pitch .............................................. 33

Relative humidity..............................................18

Transverse pitch - Maximum ........................... 73

Relative pressure tolerance ...........................103

Transverse pitch - Minimum ............................73

Report Heading Example ...............................106

Transverse pitch - Specified ............................ 73

Run Log..........................................................118

Transverse pitch - Step Size............................ 73

Run shortcut calculations...............................105

Transverse pitch checkbox ..............................73

Runtime Messages ........................................119

Tube dimensions..............................................49

S

Tube form.........................................................27

Safety panel .....................................................93

Tube Geometry..............................................110

Schedule ..........................................................10

Tube Geometry page.......................................31

Side seals.........................................................28

Tube Information............................................127

Single-Phase Methods ...................................206

Tube inside diameter .......................................40

Split segment height.........................................47

Tube internals ..................................................30

Split segment width..........................................48

Tube layout ......................................................27

Steam coil present ...........................................17

Tube length ......................................................28

Stream Properties ..........................................142

Tube length - Maximum ................................... 74

Stud diameter...................................................53

Tube length - Minimum ....................................74

Stud Fins page .................................................51

Tube length - Specified....................................74

Stud length .......................................................52

Tube length - Step Size ................................... 75

Surface correction factor..................................90

Tube length checkbox......................................74

T

Tube material code ..........................................31

Table of Tube Pitches ......................................35

Tube name.......................................................30

Temperature Maldistribution panel ..................84

Tube Nozzle...................................................131

Temperature Monitor......................................137

Tube OD ..........................................................32

Thermal Resistance ...............................112, 131

Tube orientation.................................................8

Total combined fan and drive efficiency...........14

Tube outside diameter - Maximum ..................77

Total tubesheet thickness ................................21

Tube outside diameter - Minimum ...................76

Total unfinned tube length................................28

Tube outside diameter - Specified...................76

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Index

Tube outside diameter - Step Size...................77

Typical Maximum Stud Density .......................52

Tube outside diameter checkbox .....................76

Typical Stud-Finned Tube Geometry............... 52

Tube thermal conductivity ................................31

U

Tube type .........................................................30

Unit and Bundle Construction Information..... 125

Tube Types panel ............................................30

Unit Geometry........................................109, 115

Tubepasses - Maximum...................................70

Unit panel...........................................................5

Tubepasses - Minimum....................................70

Unit type............................................................. 6

Tubepasses - Specified....................................69

Unknown duty ................................................101

Tubepasses - Step Size ...................................70

Unset Bank Fin button ..................................... 42

Tubepasses checkbox .....................................69

User defined drawing.......................................53

Tuberows - Maximum.......................................76

User-Defined Methods panel...........................98

Tuberows - Minimum........................................75

V

Tuberows - Specified .......................................75

Vapor Mole Fraction.......................................141

Tuberows - Step Size.......................................76

Vapor Properties............................................141

Tuberows checkbox .........................................75

Velocity - Maximum..........................................79

Tubes in even-numbered rows.........................26

Velocity - Minimum...........................................79

Tubes in odd-numbered rows ..........................26

W

Tubeside f- and j-factors ..................................38

Wall thickness..................................................32

Tubeside friction factor method........................85

Wall thickness under fins .................................51

Tubeside friction factor multiplier .....................98

Wet bulb temperature ......................................18

Tubeside Monitor ...........................................134

Width of intermediate tube supports................21

Tubeside nozzle inside diameter Inlet.............11

Width of rectangular section ............................48

Tubeside nozzle inside diameter Outlet..........11

Wind velocity....................................................56

Twisted Tape page...........................................38

X

Twisted tape thickness.....................................38

Xace Online Help, printed version .....................1

Twisted tape width ...........................................39

Xace Output Reports .....................................106

Two-Phase Parameters .................................129

Xace Overview...................................................1

Typical Input for Maldistribution Panel .............83

Xace Test Case 1 ..........................................147


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