1.0 ABSTRACTThe experiment is done by using the Mechanical Heat Pump (Model: HE165) and is divided into 3 parts. The objectives of the experiment are to determine the power input, heat output and coefficient of performance of a vapour compression heat pump system, to produce the performance of heat pump over a range of source and delivery temperatures, and to plot the performance of heat pump over a range of evaporating and condensation temperatures which the saturation temperature at condensing pressure. The data obtained is then tabulated into table and is plotted into graph. The graph is plotted in order to determine the heat pump performances against cooling water outlet temperature and condensing temperature. 2.0INTRODUCTIONThe Mechanical Heat Pump (Model: HE165) has been designed to provide a practical and quantitative demonstration of a vapour compression cycle, and is suitable for all course levels (intermediate and undergraduate). Refrigerators and heat pumps both apply the vapour compression cycle, although the applications of these machines differ, the components are essentially the same. During the operation, slightly superheated refrigerant (R-134a) vapour enters the compressor from the evaporator and its pressure is increased. Thus, the temperature rises and the hot vapour then enters the water cooled condenser. Heat is given up to the cooling water and the refrigerant condenses to liquid before passing to the expansion valve. Upon passing through the expansion valve, the pressure of the liquid refrigerant is reduced. This causes the saturation temperature to fell to below that the atmospheric. Thus, as it flows through the evaporator, there is a temperature difference between the refrigerant and the water being drawn across the coils. The resulting heat transfer causes the refrigerant to boil, and upon leaving the evaporator it has become slightly superheated vapour, ready to return to the compressor.Industrial heat pumps are used to recover or make best use of heat in manufacturing processes or in public utilities such as energy generation & distribution. They vary enormously in both size and concept, but most are specially designed for the application. Domestic heating only heat pumps can compete environmentally and economically with gas heating. Reversible heat pumps, which can also provide summer cooling, are not as efficient as those designed for heating only and are likely to result in higher heating bills and overall greater environmental impact compared to other fuels. The output of currently available domestic heat pumps is limited to approximately 5 kW so they are best suited to small or very well insulated properties.

3.0OBJECTIVES1. To determine the power input, heat output and coefficient of performance of a vapour compression heat pump system.2. To produce the performance of heat pump over a range of source and delivery temperatures.3. To plot the performance of heat pump over a range of evaporating and condensation temperatures which the saturation temperature at condensing pressure.

4.0THEORYA heat pump is a mechanism that absorbs heat from waste source or surrounding to produce valuable heat on a higher temperature level than that of the heat source. The fundamental idea of all heat pumps is that heat is absorbed by a medium, which releases the heat at a required temperature which is higher after a physical or chemical transformation. Heat pump technology has attracted increasing attention as one of the most promising technologies to save energy. Areas of interest include heating of buildings, recovery of industrial waste heat for steam production and heating of process water for e.g. cleaning, sanitation.Generally, there are three types of heat pump systems: i. Closed cycle vapour compression heat pumps (electric and engine driven)ii. Heat transformers (a type of absorption heat pump) iii. Mechanical vapour recompression heat pumps operating at about at 200C

Closed Cycle Vapour Compression Heat PumpMost of the heat pumps operate on the principle of the vapour compression cycle. In this cycle, the circulating substance is physically separated from the heat source and heat delivery, and is cycling in a close stream, therefore called closed cycle. In the heat pump process, the following processes take place: 1. In the evaporator the heat is extracted from the heat source to boil the circulating substance; 2. The circulating substance is compressed by the compressor, raising its pressure and temperature; 3. The heat is delivered to the condenser; 4. The pressure of the circulating substance (working fluid) is reduced back to the evaporator condition in the throttling valve.

Vapor Compression Heat Pump System Principles

The labeled components are: 1. Condenser2. Compressor3. Expansion Valve4. EvaporatorFour basic processes or changes in the condition of the refrigerant occur in a Vapor Compression Heat Pump Cycle. These four processes shall be illustrated in the most simplistic way with the aid of above schematic sketch.i.Compression Process (t1 t2)The refrigerant at the pump suction is in gas at low temperature and low Pressure. In order to be able to use it to achieve the heat pump effect continuously, it must be brought to the liquid form at a high pressure. The first step in this process is to increase the pressure of the refrigerant gas by using a compressor. Compressing the gas also results in increasing its temperature.

ii.Condensing Process (t2 t3)The refrigerant leaves the compressor as a gas at high temperature and pressure. In order to change it to a liquid, heat must be removed from it. This is accomplished in a heat exchanger called the condenser. The refrigerant flows through one circuit in the condenser. In the other circuit, a cooling fluid flows (normally air or water), at a temperature lower than the refrigerant. Heat is therefore transferred from the Refrigerant to the Cooling fluid and as a result, the refrigerant condenses to a liquid state. This is where the heating takes place.iii.Expansion Process (t3 t4)At Point (3), the refrigerant is in liquid state at a relatively high pressure and temperature. It flows to (4) through a restriction called the flow control device or expansion valve. The refrigerant loses pressure going through the restriction. The Pressure at (4) is so low that a small portion of the refrigerant flashes (vaporizes) into a gaseous. In order to vaporize, it must gain heat (which it takes from that portion of the refrigerant that did not vaporize).iv.Vaporizing Process (t4 t1)The refrigerant flows through a heat exchanger called the evaporator. The heat source is at a slightly higher temperature than the refrigerant, therefore heat is transferred from it to the refrigerant. The refrigerant boils because of the heat it receives in the evaporator. By the time it leaves the evaporator (4) it is completely vaporized.The refrigerant has thus returned to its initial state and is now ready to repeat the cycle, in a continuous manner.

Obtain the Enthalpy Values from P-H DiagramTo obtain the following values, we first refresh our memory from the previous chapter on Flow diagram of a Simple Saturated Cycle Enthalpy or p-h diagram of R-134a, Simple Saturated Cycle, as shown below:

Figure 1: Flow diagram of a simple saturated cycle

Figure 2: Comparison of two simple saturated cycles operating at different vaporizing temperatures (figure distorted). (Refrigerant-134a)

Figure 3a: Skeleton P-H chart illustrating the three regions of the chart and the direction of phase changing

Figure 3b: Skeleton P-H chart showing oaths of constant pressure, constant temperature constant volume, constant enthalpy, and constant entropy. (Refrigerant-134a)

Figure 3c: Pressure-enthalpy diagram of a simple saturated cycle operating at a vaporization temperature of 200F and a condensing temperature of 1000F. (Refrigerant 134a)

h1 = The Enthalpy at Point 1, which is the point where Compression Process", begins. (This is also where we obtained the Temperature Reading, TT1 for the process).h2 = The Enthalpy at Point 2, which is the point where "Compression Process" ends.h3 = The Enthalpy at Point 3, which is the point where "Condensation" is complete.(This is also where we obtained the Temperature Reading, TT3 for the process).Thus,h2 h3 = Refrigerating Effect (See figure 2)While,h2 h1 = Heat of Compression (See figure 2)Figure 4: Pressure-enthalpy diagram of a simple saturated cycle operating at a vaporizing temperature of 20oF and a condensing of 100oF (Refrigerant- 134a)

Coefficient of PerformanceThe Coefficient of Performance, (COPH) of a heat pump cycle is an expression of the cycle efficiency and is stated as the ratio of the heat removed in the heated space to the heat energy equivalent of the energy supplied to the Compressor.COPH = Heat removed from heated space / Heat energy equivalent of the energy supplied to the compressor.COPH = =

5.0APPARATUS AND MATERIAL198765432

Mechanical Heat Pump (Model: HE 165)1. Pressure Switch6. Control Panel

2. Receiver Tank7. Water Flow Meter

3. Compressor8. Evaporator

4. Condenser9. Refrigerant Flow Meter

5. Pressure Transmitter

6.0PROCEDURE6.1General Start-up Procedures1. The unit and all instruments are checked and in proper condition.2. Both water sources is checked and drain are connected then the water supply is opened and the cooling water flowrate is set at 1.0 LPM.3. The drain hose at the condensate collector is checked and connected.4. The power supply is connected and the main power is switched on followed by main switch at the control panel.5. The refrigerant compressor is switched on. The unit is now ready for experiment as soon as temperature and pressures are constant.6.2General Shut-down Procedures1. The compressor is switched off, followed by main switch and power supply.2. The water supply is closed and the water is ensure that is not left running.6.3Experiment 1: Determination of power input, heat output and coefficient of performance.1. The general start-up procedure is performed.2. The cooling water flow rate is adjusted to 40%.3. The system is allowed to run for 15 minutes.4. All necessary readings is recorded into the experimental data sheet.

6.4Experiment 2: Production of heat pump performance curves over a range of source and delivery temperatures1. The general start-up procedure is performed.2. The cooling water flow rate is adjusted to 80%.3. The system is allowed to run for 15 minutes.4. All necessary readings are recorded into the experimental data sheet.5. The experiment is repeated with reducing water flowrate so that the cooling water outlet temperature increases by about 3C.6. The similar step is repeated until the compressor delivery pressure reaches around 14.0 bars.7. The experiment may be repeated at different ambient temperature.

6.5Experiment 4: Production of heat pump performance curves over a range of evaporating and condensation temperatures1. The general start-up procedure is performed.2. The cooling water flow rate is adjusted to 80%.3. The system is allowed to run for 15 minutes.4. All necessary readings are recorded into the experimental data sheet.5. The experiment is repeated with reducing water flowrate so that the compressor delivery pressure increases by about 0.6 bars. The evaporating temperature (TT4) is maintained by covering part of the evaporator for the purpose of lowering the evaporating load.6. The similar step is repeated with water flow rate not less than 20%. Make sure that the compressor delivery pressure does not exceed 14.0 bars.7. The experiment may be repeated another constant evaporating temperature (TT4).

7.0RESULTExperiment 1: Determination of power input, heat output and coefficient of performanceCooling Water Flow Rate, FT1%40

Cooling Water Flow Rate, FT1LPM2.0

Cooling Water Inlet Temperature, TT5C28.9

Cooling Water Outlet Temperature, TT6C29.8

Compressor Power InputW163

Experiment 2: Production of heat pump performance curves over a range of source and delivery temperatures Test1234

Cooling Water Flow Rate, FT1%20406075.7

Cooling Water Flow Rate, FT1LPM1.02.03.04.0

Cooling Water Inlet Temperature, TT5C29.229.329.429.5

Cooling Water Outlet Temperature, TT6C31.630.630.330.2

Compressor Power InputW165164162161

Heat OutputW167.2181.1188.1195.1

COPH-1.011.101.161.21

Graph of Performance of Heat Pump against Cooling Water Outlet Temperature

Experiment 4: Production of heat pump performance curves over a range of evaporating and condensation temperaturesTest123

Refrigerant Flow Rate, FT2%24.124.324.1

Refrigerant Flow Rate, FT2LPM0.3030.3050.303

Refrigerant Pressure (Low), P1Bar(abs)2.22.12.0

Refrigerant Pressure (High), P2Bar(abs)7.57.36.9

Refrigerant Temperature, TT1C26.426.626.4

Refrigerant Temperature, TT2C56.061.360.9

Refrigerant Temperature, TT3C29.028.627.2

Refrigerant Temperature, TT4C23.222.922.0

Enthalpy 1 (P1, TT1)kJ/kg428427430

Enthalpy 2 (P2, TT2)kJ/kg441447449

Enthalpy 3 (P2, TT3)kJ/kg240245245

Evaporating Temperature (TT4)C23.222.922.0

Condensing TemperatureC27.025.222.6

Compressor Power InputW260250247

Heat Delivered in Condenser (Refrigerant)W554.7495.7560.0

COPH-1.011.101.16

Graph of Performances Curves for Heat Pump against Condensed Temperature

8.0SAMPLE OF CALCULATIONExperiment 1: Determination of power input, heat output and coefficient of performance

Experiment 4: Production of heat pump performance curves over a range of evaporating and condensation temperaturesEnergy Balance on the CondenserRefrigerant mass flowrate

Heat transfer from the refrigerant

Heat transfer to the cooling water

Energy Balance on the CompressorPower Input

Heat transfer to the refrigerant

Heat loss to surroundings= 250 74.1 = 175.9 W

9.0DISCUSSIONExperiment 1 is done in order to determine the power input, heat output and the coefficient of performance or COPH at the cooling water flow rate of 40%. The cooling water flow rate, FT 1 is displayed on percentages, thus, the formula must be used in order to convert it in litre per minute or LPM. After 15 minutes, the data is collected and calculated. The reading temperature of cooling water inlet and outlet are 28.9 and 29.8 C respectively while the compressor power input is 163 W. The heat output can be determined by inserting the temperature reading into the formula. The heat output is then divided with power input in order to get the value of COPH which is 1.10. Next, Experiment 2 is done in order to determine the production of heat pump performances curves over a range of source and delivery temperature. In the experiment, the cooling water flowrate can only achieved about 75.7%. This may resulted from the slow water flowrate from the source. The data for this experiment is taken for each drop of 20 % of cooling water flowrate. The reducing of water flowrate can only increase the cooling water outlet temperature slightly and not about 3C as stated in the procedure. This may be due to the error that is occurred inside the heat pump as the temperature wont rise even the cooling water is increase or due to the slow flow of water from source. Based on the data tabulated, graph of performances of heat pump against cooling water outlet temperature is plotted. The performance of heat pump is taken based on the heat output, power input and the coefficient of performance as the cooling water outlet temperature is increasing. The graph shows that the coefficient of performances falls between the heat output and power input at the beginning and falls below the value of power input at the end of experiment. Lastly, Experiment 3 is done in order to determine the production of heat pump performances curves over a range of evaporating and condensing temperature. As discussed in Experiment 2, the cooling water flowrate can only achieved about 75.7%. Thus, the flowrate of cooling water is taken starting from 60% and is decreased every 20%. The value of enthalpy is taken from the pressure-enthalphy diagram. Based on the data tabulated, graph of performances curves of heat pump against condensing temperature is plotted. The performance curves is taken based on the heat output, power input and the coefficient of performance as the condensing temperature is increasing. The graph shows that the coefficient of performances falls between the heat output and power input at the beginning and falls below the value of power input at the end of experiment.

10.0CONCLUSIONThe objective of Experiment 1 is to determine the power input, heat output and coefficient of performance of a vapour compression heat pump system. The value of power input, heat output and coefficient of performance is obtained and calculated successfully. Thus, the objective of the experiment is achieved.For Experiment 2 and 3, both experiments have an objective which can be achieved depending on the graph. As stated in the discussion part, the graph shows that the coefficient of performances falls between the heat output and power input at the beginning and falls below the value of power input at the end of experiment. Based on the theory, the Coefficient of Performance, (COPH) of a heat pump cycle is an expression of the cycle efficiency and is stated as the ratio of the heat removed in the heated space to the heat energy equivalent of the energy supplied to the compressor. The COPH should maintain in between both heat output and power input in order for the heat pump to cycle efficiently. Thus, it can be concluded that the experiment only achieved the objective of showing the performance curves but not theoretically.

11.0RECOMMENDATIONS1. Make sure the reading is stabilized and waited about 15 minutes before taking the reading because it will affect the result.2. The water supply must be in good condition and high in flow rate as it may affect the result.3. Any calculation and graph readings must be made repeatedly in order to avoid error.4. Ensure that the machine is in good condition and consult with the technician if there any problem.

12.0REFERENCES1. Chemical Engineering Laboratory Manual. (CGE 536), Faculty of Chemical Engineering, UiTM Shah Alam .2. http://www.kwikwap.co.za/labequip/docs/Mechanical%20Heat%20Pump%20%20HE165A.pdf.3. http://energy.gov/energysaver/articles/heat-pump-systems4. www.docstoc.com/docs/25444876/heat-pump-experiment

13.0APPENDICES

1