FACULTY OF ENGINEERING, TECHNOLOGY & BUILT ENVIRONMENT
SUBJECT CODE & NAME: EM306 THERMODYNAMICS II
Lecturer Name: Dr. LAI Nai Yeen Gavin Tutor Name: Ms. Nor Fazilah
Student Name
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Student ID
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Semester / Year
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January – April April 2014
EM306| Thermodynamics II
TABLE OF CONTENTS
SN
Content
Page
1
Experiment #1 Air Conditioning Unit
2
2
Experiment #2 General Observation of Cooling Tower and Relationship
3
between Cooling Load and Cooling Range
3
Experiment #3 End State Properties of Air and Steady Flow
5
Equations
4
Experiment #4 Refrigeration System
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EM306| Thermodynamics II
Experiment 1 – Title: Air Conditioning Unit
Objective
To study the cooling effects and to determine the cooling power of the cooling coil To study the dehumidification effects and to determine the cooling power of the cooling coil To study the heating effects and to determine the heating power of the heaters
Introduction / Instruction / Procedure / Guideline
Design and conduct experiments to achieve the above objectives. Students should run the radial fan at selected air speed and choose the selected processes. Additionally, students should also record the air temperature and relative humidity at the inlet and outlet of the coil and the differential pressure reading across the orifice when a steady state is reached.
Process will stabilize in approximately 15 minutes. **Note:
Results and Discussion
1. For each process, plot these two state points (inlet & outlet points) on the Psychrometric chart. 2. Analyze the Specific Volume of Outlet Air, v (m3/kg dry air) and Absolute Humidity of Outlet Air,
(kg/kg dry air) from Psychrometric chart.
3. Assess the cooling power of the cooling coil and heating power of the heaters. (Please show your calculation) 4. Complete the name of unit assembly of Air-Cond unit (AC01) – Refer attachment.
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EM306| Thermodynamics II
Experiment 2 – Title: General Observation of Cooling Tower and Relationship between Cooling Load and Cooling Range
Objective
To observe the processes within a forced draught cooling tower To investigate the relationship between cooling load and cooling range Introduction / Instruction / Procedure / Guideline Observation of Forced Draught Cooling Tower
1. Perform the general start-up procedures and observe the forced draught cooling tower proves. 2. As the warm water enters the top of the tower, it is fed into channels from which it flows via water distribution system onto the packing. The channels are designed to distribute the water uniformly over the packing with minimum splashing. 3. The packing surfaces are easily wetted and the water spreads over the surfaces to expose a large area to the air stream. 4. The cooled water falls from the lowest packing into the basin and then is pumped to the simulated load in the load tank. 5. During the process, some water is lost due to the evaporation. Thus, "make-up" water must be supplied to keep the amount of water in the cooling system constant. The make-up is observed flowing past the float-controlled valve in the load tank. 6. A “droplet arrester”, or “mist eliminator” is fitted at the tower outlet to minimize loss of water due to escape of droplets of water (resulting from splashing, etc.) which is entrained in the air stream. This loss does not contribute to the cooling, but must be made good by "make-up". The droplet arrester causes droplets to coalesce, forming drops that are too large to be entrained and these falls back into the packing. 7. The fan drives the air upward through the wet packing. At air outlet, the air leaving the cooling tower is almost saturated, i.e. Relative Humidity is ~100%. The Relative Humidity at the air outlet is much higher than the Relative Humidity at the air inlet. The increase in the moisture content of the air is due to the evaporation of water into steam and the "latent heat" for this account for most of the cooling effect. 8. When the cooling load is switched off and the unit is allowed to stabilize, it is found that the water leaves the basin at temperature close to the wet bulb temperature of the air entering. Wet bulb temperature is lower than the dry bulb temperature and this varies according to the local atmospheric conditions (i.e. pressure and relative humidity). 9. With no load, the water would be cooled to the incoming wet bulb temperature. However, the condition cannot be achieved since the work done by the pump transfers about 40W to the water.
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EM306| Thermodynamics II
Relationship between Cooling Load and Cooling Range
1. Set the system under the following conditions and allow stabilizing for about 15 minutes. i. Water flow rate ii. Air Flow iii. Cooling load
: : :
2.0 LPM Maximum 0.0 kW
2. After the system stabilized, record a few sets of the measurements such as temperatures, orifice differential pressure, water flowrate and heater power, then obtain the mean value for calculation and analysis. 3. Without changes in the conditions, increase the cooling load to 0.5 kW. When the system stabilized, record all data. 4. Similarly, repeat the experiment at 1.0kW and 1.5kW. 5. The tests may be repeated: i. At other water flow rates ii. At other air flow rate
Results and Discussion
1. Outline your observation of the process within a forced draught cooling tower in the lab. 2. In UCSI University North Wing Campus, cooling towers are used in the air conditioning system. Explain the principle of this system and use some sketches as illustrations to show the cycle of cooling the classrooms in the campus. 3.
Plot a graph of cooling load vs. cooling range. Analyze the relationship.
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EM306| Thermodynamics II
Experiment 3 – Title: End State Properties of Air and Steady Flow Equations
Objective
To determine the “end state” properties of air and water from tables or charts To determine energy and mass balances using the steady flow equation.
Introduction / Instruction / Procedure / Guideline
Based on experience conducting previous experiment of cooling tower, design and conduct an experiment of a modern evaporating system. The experiment should determine the “end state” properties of air and . Student also needs to show the calculations to draw up energy and mass balances.
The cooling tower unit should be prepared, start and allow stabilizing under following suggested conditions:
Water flow rate = 2.0 LPM
Air flow
= Maximum
Cooling load
= 1.0kW
After the conditions have stabilized, observe and examine the processes of the water system and air system of the cooling tower.
Results and Discussion
1. Determine the “end state” properties of air and water from tables or charts . 2. Calculate the energy and mass balances by using the steady flow equation. 3. Evaluate and discuss the major factor and issues affecting the accuracy of the measurements and cooling tower performance.
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EM306| Thermodynamics II
Experiment 4 – Title: Refrigeration System
Objective
To investigate the effect of condensing and evaporating temperatures on the refrigeration rate and condenser heat output. To determine the compression ratio and its effect on system performance Introduction / Instruction / Procedure / Guideline
1. Ensure that the unit is air free by venting the air from the condenser. 2. Adjust the condenser cooling water flow, to the maximum and Evaporator cooling water flow, to 1.5LPM. The pressure at which the condenser stabilizes will depend upon the water inlet temperature. 3. Allow the temperature and pressure readings to stabilize. Then, record all the system parameters. 4. Reduce the condenser cooling water flow rate to increase the condenser pressure by approximately 0.1 kgf/cm2. 5. Allow the unit to stabilize and again record all of the system parameters. 6. Repeat for increasing condenser pressures to the minimum readable value on the condenser water flow meter is reached.
Results and Discussion
1. Compare the Heat Transfer Rate in Condenser Vs Condensing Temperature (with the help of a graph) 2. Assess the Evaporator Heat Transfer, Q E(W) and Condenser Heat Transfer, Q C(W) 3. Compare the Heat Transfer Rate in Condenser Vs Compressor Pressure Ratio (with the help of a graph) 4. Assess the Evaporator Heat Transfer, Q E(W) and Condenser Heat Transfer, Q C(W). 5. Determine the pressure ratio for every condenser pressure readings obtained (Pc/PE).
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EM306| Thermodynamics II
Attachment: General Introduction (Air Conditioning Unit AC01)
Air-conditioning is a widespread feature of building engineering, designed to make the occupants feel comfortable and at ease. The main functions of an air-conditioning system include heating and cooling, and humidifying and dehumidifying in order to create the desired indoor air conditions. The SOLTEQ® Air-Conditioning Unit (M odel: AC 01) includes all the components found in airconditioners installed in buildings. It additionally has a complete refrigeration unit, enabling the system to cover most of the spectrum of experiments in the field of refrigeration and air-conditioning engineering. COMBINED TEMPERATURE /
AT 1
HUMIDITY TRANSMITTER
RH 1 T
AT 2
AT 3
AT 4
AT 5
RH 2
RH 3
RH 4
RH 5
T
T
T
T
RADIAL FAN
DP
DIFFERENT PRESSURE MANOMETER
PRE-HEATER
EVAPORATOR
RE-HEATER
ORIFICE
STEAM HUMIDIFIER
Figure 1: Process Schematic Diagram for AC System
Air Duct Cross Sectional Area, A = 0.09 m 2 Specific Heat Capacity of Air, C p = 1.006 kJ/kg.K Orifice Differential Pressure, DP ' 0.102 DP (mmH2O)
a Air Mass Flowrate, m
0.0592
DP ' v1
Cooling Power Power,
Heating Power (kW),
Heat Transfer Efficiency (%)
Efficiency
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Q P
100%
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EM306| Thermodynamics II
Unit Assembly of Air Conditioning Unit - AC01
1 9
2 3
10
4
11
5 12 6
13 14
7 15
8
Figure 2: Unit Construction for Air Conditioning Unit
1. _______________________
9.
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10. ________________________
3. _______________________
11. ________________________
4. _______________________
12. ________________________
5. _______________________
13. ________________________
6. _______________________
14. ________________________
7. _______________________
15. ________________________
8. _______________________
* Please submit this together with your report
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EM306| Thermodynamics II
General Introduction ( Bench top cooling Tower HE152) ® The SOLTEQ Basic Cooling Tower Unit (Model: HE152) has been designed to demonstrate the construction, design and operational characteristics of a modern cooling system. The unit resembles a full size forced draught cooling tower and it is actually an "open system" through which two streams of fluid (in this case air and water) pass and in which there is a mass transfer from one stream to the other. The unit is self-contained supplied with a heating load and a circulating pump. Once energy and mass balances are done, students will then be able to determine the effects on the performance of the cooling tower by the following parameters:
a) b) c)
Temperature and flow rate of water Relative Humidity and flow rate of air Cooling load
Additionally, a Packing Characteristics Column (optional) is available for SOLTEQ® Basic Cooling Tower Unit (Model: HE152). This column is designed to facilitate study of water and air conditions at three additional stations (I, II and III) within the column. This enables driving force diagrams to be constructed and the determination of the Characteristic Equation for the Tower. 1.
Orifice Calibration Formula: Mass flow rate of air and vapor mixture,
0.0137 m
x1 v ab
The mass flow rate of dry air,
a m
0.0137
x v ab 1
Where, x
v a B
= orifice differential in mmH20, = specific volume of air at the outlet = humidity ratio of the mixture
2.
Pump Work Input = 80W
3.
Column Inner Dimension = 150 mm x 150 mm x 600 mm
4.
Packed column: 110 m2/m3
5.
Inner diameter of Make up tank = 74mm
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(0.08kW)
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EM306| Thermodynamics II
GENERAL OPERATING PROCEDURES (Refrigeration Cycle Demonstration Unit RF166)
The SOLTEQ® Refrigeration Cycle Demonstration Unit (Model: RF166) has been designed to study the thermodynamics of the vapor compression cycle. The unit is constructed as a bench top unit. The unit operates as a refrigerator so that experiments on the evaluation of refrigeration cycle and thermodynamic energy balances of the condenser, evaporator, and compressor can be performed. The evaporation and condensation can be observed through the glass tubes. A refrigerator is defined as a machine whose prime function is to remove heat from a low temperature region. Since energy cannot be destroyed, the heat taken in at a low temperature must be dissipated to the surroundings. Refrigerators are cyclic devices, and the working fluids used in the refrigeration cycles are called refrigerants. A refrigerator requires an external energy for it to operate. This energy input may be in the form of work, or a heat transfer at a high temperature. The most common type of refrigerator uses a work input and operates on the vapour compression cycle.
Condenser Pressure Evaporator Pressure Condenser Water Flowrate Evaporator Water Flowrate Condenser Temperature Condenser Water Inlet Temp. Condenser water Outlet Temp. Evaporator Temperature Evaporator Water Inlet Temp. Evaporator Water Outlet Temp.
PT 1 ( Abs Bar) PT 2 ( Abs Bar) FT 1 (LPM) FT 2 (LPM) T 1 (oC) T 2 (oC) T 3 (oC) T 4 (oC) T 5 (oC) T 6 (oC)
Table 6.1: System Parameter
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EM306| Thermodynamics II
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