Shell and Tube Heat Exchanger October 7, 2003 Cycle 2 Group 1A Frank Fadenholz Jennifer Fadenholz Christian Woods Angell Taylo Ange Taylor aylor
Outline • Objectives • Background • Experimental Strategy • Results • Error Analysis • Conclusions • Recommendations • References
Objectives and Background
Objectives • Operate shell and tube heat exchanger varying steam flow
• Determine the outside overall heat transfer coefficient (Uo)
• Determine shellside heat transfer (Q SS ) • Determine tubeside heat transfer (Q TS )
Heat Exchanger Background • Exchange heat between fluids • Latent heat and sensible heat transfer • Common to chemical process industry • Types of heat exchangers – – – –
Air Cooled Double Pipe Spiral Plate and Tube Shell and Tube
Heat Exchanger Background Shell and Tube Heat Exchangers
• Account for 60% of heat exchangers in use today • Can handle large flows, low temperatures and pressures, pressures, high temperatures and pressures
• Our shell and tube heat exchanger – – –
Basco Type 500 U-tube Water Heater 1 Shell Pass 16 Tubes
Experimental Strategy
Cold Water Inlet
Compressed Air
Steam
ST-V4
Emergency Shutdown Valve
ST-V1
ST-V3
ST-V2
Emergency Shutdown Vavle
TV-04
Should make Labels Larger
FT-01
PRV-05 TT-04
Hot Water Outlet
E-01 PG-07
C o n d e n s a t e
T ST-V5
PG-06
FT-02
FV-02
TT-03
Experimental Strategy • 5 Runs Total • Varied Steam Valve (TV-04) Position – – – – –
105% open 75% open 65% open 60% open 52% open
• Cooling water flow rate constant
Experimental Strategy • Measured Variables – Condensate flow – Condensate temperature – Cooling water flow – Cooling water inlet temperature – Cooling water outlet temperature
Heat Exchanger Calculations • Heat transfer rate •
Q TS = mCp∆ T
•
QSS = m∆ H + mCp∆ T
• Overall heat transfer coefficient •
Uo = QSS /(Ao*∆ TLM )
• Log mean temperature • ∆ TLM = ((Thi -Tco ) – (Tho – Tci )) / ln[(Thi
– Tco ) – (Tho – Tci )]
Simplified Process Flow Diagram Thi
Qin,SS Tci
Qin,TS
Qout, TS Qout,SS
Tho
Tco
Results
Experimental Results Steam Valve Heat Transfer Heat Transfer % Open Rate (QTS ) Rate (QSS ) (btu/hr) (btu/hr)
Overall Heat Transfer Coefficient (Uo) (btu/lb*F*hr)
105%
276489
275350
211
75%
250275
254588
201
65%
183357
181872
148
60%
134200
133777
112
52%
98289
93757
78
Shellside vs. Tubeside Heat Transfer He at Tr anfe r Rate (Q) Q-tube Q-tube s ide vs. Q-sh Q-sh e ll s 290000 e ) 240000 d i r s h e / 190000 b u u t t
b Q ( 140000 90000 75000
125000
17 5000
Qshellsid (btu/hr)
225000
275000
Steam vs. Heat Transfer Rate (Q TS , QSS ) e t 290000 a R r ) 240000 e r f s h / n t u190000 a b r T ( 140000 e t a 90000 H
75
125 175 225 Condensate Mass Out (lb/hr) Q-Shellside
Q-Tub Tubeside
275
Steam vs. Overall Heat Transfer Coefficient 300 30 0 250 25 0 r ) t e r f n h s e * 20 0 n i F 200 c a * r i f f l 150 T e b 15 0 t o / u a t b e C ( 100 10 0 H 50 50
100
15 0
200
250
Condensate Mass Out (lb/h U i n s id e
U o u ts id e
300
Error Analysis
Propagation of Error • Determine the accuracy of measured variables • Apply the propagation of error equation to each function
k ∂ y ∆ y = ∑ ∆ xi i = ∂ xi 2
1
1
2
Variable Measurement Accuracy
• Flow rate of the steam +/- 5 lb/hr • Flow rate of the cooling water +/- 50 lb/hr • Temperature readings +/- 2 °F
• Largest sources of error – Mass flow rate of the steam – Mass flow rate of the cooling coo ling water
Calculated Error Values • ∆Q ≈ +/- 1,000 btu/hr • ∆Q ≈ +/- 50,000 btu/hr • ∆U ≈ +/- 4 btu/lb °F hr • ∆U ≈ +/- 4 to +/- 1.6 btu/lb °F hr TS
SS
o
i
Propagation of Error Heat Transfer e t 340000 a R r ) 290000 e r f s h / 240000 n t u a r ( b 190000 T t 140000 a e 90000 H
75
1 25
1 75
2 25
Condensat Condensate e Mass Out Out (lb/hr) (lb/hr) Q-tub -tubeside eside
Q-shel -shelllside side
27 5
Propagation of Error Heat Transfer Coefficient 300 30 0 250 25 0 r ) t e r f n h s e * 20 0 n i F 200 c a * r i f f l 150 T e b 15 0 t o / u a t b e C ( 100 10 0 H 50 50
100
15 0
200
250
Condensate Mass Out (lb/h U i n s id e
U o u ts id e
300
Conclusions and Recommendations
Conclusions • Q TS , QSS , Uo all increase as the steam flow rate increases
• Q TS , QSS , Uo all have a linear relationship with the mass flow rate of the steam
• Heat transfer rate of the tube side is equal to the heat transfer rate of the shell side
Recommendations • Operation Recommendation – Operate the shell and tube heat exchanger at approximately 75% for sufficient heat transfer and economic efficiency
Recommendations ations Recommendations • Experiment Recommend – Monitor pressure gauge (PG-07) at low steam rates to prevent a vacuum
References • API Heat Transfer. Shell and Tube Heat Exchanger Picture
• • • •
www.apiheattransfer.com/en/Products/HeatExchangers/She llAndTube/ Georgia Tech. Propagation of Error . www.swiki.che.gatech.edu/CHE4200. August 2002. Geankoplis, Christie J. Transport Processes and Unit Operations, 3rd 3rd ed. Englewood Cliffs, NJ. Prentice-Hall Publishing, Inc. 1993. Heald, C. C. Cameron Hydraulic Data. Liberty Corner, NJ. Ingersoll-Dresser Pump Co. 1998. Peters, Timmerhaus, West. Plant Design and Economics for Chemical Engineers, 5th ed. New York, NY. NY. McGaw-Hill Co. Inc., 2003.
