Lab 1 Heat Pump
Lab 1 Heat Pump
Lab 1 Heat Pump
Contents
Abstract ...................................................................................................................................... 2
Introduction ................................................................................................................................ 3
Results ........................................................................................................................................ 9
Discussion ................................................................................................................................ 14
Conclusion ............................................................................................................................... 16
Reference ................................................................................................................................. 17
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THERMODYNAMICS
ABSTRACT
This experiment is carried out to study the mechanical heat pump and
thermodynamics refrigeration unit work through the operating of the equipment Heat Pump
(Model: ET102). This experiment is conducted by doing a series of tests by manipulating the
delivery temperatures and flow rates of the cooling water. The experimental capabilities with
different objectives can be carried out such as to study the mechanism of a heat pump,
coefficient of performance and heat pump performance curves. Besides, this experiment is
conducted to study the cyclic thermodynamic process of heat pump and comparing the ideal,
real and actual Coefficient of Performance(COP). From the result, the experimental and
theoretical calculations results have a bit difference between each other. One of the reasons
for this difference is reading mistakes on Log P-h diagram, and then the theoretical
calculations are based on idealized cycle. In actual case there are many factors effects the
differences such as heat loss and friction.Next, able to determine the coefficient of
performance of the heat pump and effect of the delivery temperatures towards the coefficient
of performance. Lastly, to produce the performance curves of the heat pump and vapour
compression cycle on a p-h diagram.
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INTRODUCTION
Heat pumps are currently in fashion, and are even subsidised by plenty of state, which
is quite sensible, because not only do they run on electricity that is free emission at the point
of use, they are also comparatively economical and draw their power from the national grid
and centralized generating stations. In general, it will always be more efficient to use
centrally generated power to operate equipment such as heat pumps rather than to generate
heat locally by burning fossil fuels such as oil or gas, although decentralised solutions such as
solar panels can also be used to operate heat pumps. Heat pumps can be broadly subdivided
into three basic systems, air to air, air to water and water – water. In this instalment you can
read about the components that manufacturers use in these heat pump systems.
In all types of refrigeration and air conditioning work, a thorough knowledge of the
basic principles is required. This is particularly true when dealing with heat pump systems
where both heating and cooling modes of operation must be understood. The Heat Pump
Training System provides the necessary training to develop the understanding of typical
domestic heat pump systems. A hands-on approach is taken to train and evaluate the principle
components used in modern heat pumps. The trainer is designed with a general approach to
heat pump systems which may be applied to many of the popular systems in use today. The
trainer will demonstrate the functions and applications of heat pump principles, which in turn
will develop the student’s understanding of the conditions under which heat pump systems
are most effective. A heat pump transports heat and this is the defining characteristic of all
heat pumps. It functions in the same way as a compression refrigeration system, except that
the principal focus is not on the evaporator side for example the cool side, but on the
condenser side where the heating effect is. The essential principle remains the same
evaporation of refrigerant in the evaporator, increase of pressure and hence temperature in the
compressor, dissipation of the gained heat by liquefying the refrigerant in the condenser, and
subsequent expansion of the refrigerant through the throttle valve.
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The refrigerants used are also hardly any different from those used in an ordinary
refrigeration plant. Heat is released in the condenser and delivered to the heat sink. The
vapour condenses to a high-pressure liquid as it gives up heat. The high pressure liquid is
expanded through the expansion valve to become a low pressure liquid and the cycle is
repeated. A heat pump actually delivers more heat output than the equivalent of the electric
input it uses. It is not uncommon for a heat pump to deliver more than it would obtain from
an equivalent electric resistance heating system. The most common heat pumps use
electricity-driven compressors.
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COMPONENT:
SYMBOL OF FUNCTION OF
NAME OF COMPONENT
COMPONENT COMPONENT
Heat pump is a mechanical
compression cycle
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Expansion valve is
component in refrigeration
and air conditioning systems
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PROCEDURE:
1) The heat pump circuit consists of a compressor, an evaporator with fan, a thermostatic
expansion valve and a coaxial coil heat exchanger as condenser. All components are
clearly arranged in the trainer.
2) The compressed refrigerant steam condenses in the outer pipe of the condenser and
thereby discharges heat to the water in the inner pipe. The liquid refrigerant
evaporates at low pressure in the finned tube evaporator and thereby absorbs heat
from the ambient air.
3) The hot water circuit consists of a tank, a pump and the condenser as heater. For a
continuous operation the generated heat is dissipated via an external cooling water
connection. The cooling water flow rate is set via a valve and measured.
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RESULTS
AMBIENT
26°C DATE 03/10/2017
TEMPERATURE
2.00-
TIME
4.00pm
Experiment 1 2 3 4 5 6 7 8
P1/4 in bar 5.86 5.95 4.44 5.32 6.38 4.76 5.63 4.52
P2/3 in bar 14.58 14.83 15.66 15.32 13.75 16.23 14.71 15.87
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CALCULATIONS:
1. Plot the cyclic process on the p-h diagramfor ideal and real process.
Please refer to the p-h diagrams.
Experiment 1:
Output coefficient, εfor real process
= (h2* – h3*) / (h2* – h1*)
= (439-275) / (439-420)
= 8.63
Experiment 2:
Output coefficient, εfor real process
= (h2* – h3*) / (h2* – h1*)
= (433-280) / (433-410)
= 6.65
Experiment 3:
Output coefficient, εfor real process
= (h2* – h3*) / (h2* – h1*)
= (423-268) / (423-412)
= 14.09
Experiment 4:
Output coefficient, εfor real process
= (h2* – h3*) / (h2* – h1*)
= (429-285) / (429-402)
= 5.33
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Experiment 5:
Output coefficient, εfor real process
= (h2* – h3*) / (h2* – h1*)
= (430-270) / (430-412)
= 8.89
Experiment 6:
Output coefficient, εfor real process
= (h2* – h3*) / (h2* – h1*)
= (430-280) / (430-410)
= 7.50
Experiment 7:
Output coefficient, εfor real process
= (h2* – h3*) / (h2* – h1*)
= (430-280) / (430-415)
= 10.00
Experiment 8:
Output coefficient, εfor real process
= (h2* – h3*) / (h2* – h1*)
= (430-270) / (430-410)
= 8.00
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Where:
V: flow rate in 𝑚3 /𝑠
ρ: density water in kg/𝑚3
Cp: specific heat of water in kJ/kgK
Tout: hot water outlet temperature in °C
Tin: hot water inlet temperature in °C
Pcompr: compressor power in kW
Experiment 1:
Actual output coefficient, ε
= [(V. ρ. Cp).(Tout - Tin)] / Pcompr
= [(2.78x10-6) . (996) . (4.19) . (41.6-33.1)]/0.219
= 0.45
Experiment 2:
Actual output coefficient, ε
= [(V. ρ. Cp).(Tout - Tin)] / Pcompr
= [(4.17x10-6) . (996) . (4.19) . (43.5-36.6)]/0.242
= 0.50
Experiment 3:
Actual output coefficient, ε
= [(V. ρ. Cp).(Tout - Tin)] / Pcompr
= [(5.56x10-6) . (996) . (4.19) . (43.4-37.5)]/0.250
= 0.55
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Experiment 4:
Actual output coefficient, ε
= [(V. ρ. Cp).(Tout - Tin)] / Pcompr
= [(6.94x10-6) . (996) . (4.19) . (43.8-37.3)]/0.216
= 0.87
Experiment 5:
Actual output coefficient, ε
= [(V. ρ. Cp).(Tout - Tin)] / Pcompr
= [(8.33x10-6) . (996) . (4.19) . (43.4-37.6)]/0.223
= 0.90
Experiment 6:
Actual output coefficient, ε
= [(V. ρ. Cp).(Tout - Tin)] / Pcompr
= [(9.72x10-6) . (996) . (4.19) . (43.1-37.6)]/0.245
= 0.91
Experiment 7:
Actual output coefficient, ε
= [(V. ρ. Cp).(Tout - Tin)] / Pcompr
= [(1.11x10-5) . (996) . (4.19) . (43.9-37.5)]/0.233
= 1.27
Experiment 8:
Actual output coefficient, ε
= [(V. ρ. Cp).(Tout - Tin)] / Pcompr
= [(1.25x10-5) . (996) . (4.19) . (43.1-37.3)]/0.209
= 1.45
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DISCUSSION
The objective of this experiment is to study the cyclic thermodynamic process of heat
pump and comparing the ideal, real and actual Coefficient of Performance (COP). Coefficient
of performance (COP) is an expression of the efficiency of a heat pump. The COP is
determined by the ratio between energy usage of the compressor and the amount of useful
heat extracted from the condenser. A high COP value represents a high efficiency.
The coefficient of performance (COP) for ideal cyclic process and real cyclic process
are different. The most important difference between real and ideal cyclic processes is that
compression is not isentropic such as without the discharge of heat. Besides that, the actual
coefficient of performance (COP) is derived from the flow of the water, the temperature
difference between the inlet and the outlet, and the specific heat capacity of water.
Theoretically, COPideal>COPreal>COPactual.This is because there is no heat loss to the
surrounding for ideal process but there is working medium vapor and heat losses in the
compressor to the surrounding for real process. Energy used are too much for actual process
due to radiation, heat conduction and friction.
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The efficiency of a heat pump, COP, depends on several factors especially the
temperature difference between waste heat source and potential user is an important factor.
The temperature difference between condensation and evaporation temperature mainly
determines the efficiency. The smaller the difference, the higher the coefficient of
performance. Increasing of evaporation temperature will increase the coefficient of
performance. It means that the higher the low grade energy source temperature, the higher the
coefficient of performance. In summary, the coefficient of performance (COP) is improved if
the temperature of the heat source is raised. For this reason heat pumps can be seen as devices
able to convert low grade thermal energy to useful heat.
The experimental and theoretical calculations results have a bit difference between
each other. One of the reasons for this difference is reading mistakes on Log P-h diagram,
and then the theoretical calculations are based on idealized cycle. In actual case there are
many factors effects the differences such as heat loss and friction. For example, the power
supplied to the compressor is higher in actual in experimental case than theoretical
considerations.Experimental errors may be take place because ofchange in flow rate of
system, the personal student mistakes on reading the values from experimental rig and the
sensitivity of measuring equipments and experimental rig. In addition, a cooling system can
also be used for heating. A heat pumps uses the some equipments as a refrigeration system
but operates for the purpose of delivering heat at a high level of temperature. Even though the
equipment is used in a refrigeration cycle and in a heat pump may be identical the objectives
are different. The purpose of refrigeration cycle is to absorb heat at low temperature and
purpose of a heat pump is to reject heat a high temperature.
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CONCLUSION
In the conclusions on this experiments carried out are the experiments by doing a
series of tests by manipulating the transmission temperature and the flow rate of the cooling
water. if, the coefficient of performance corresponds directly to the valve angle. Then, the
greater the angle of the valve, will be the flow rate through the condenser. However, the
increased flow rate will cause evaporator temperature to decrease. When the amount of water
flow is low through the condenser, more energy will be wasted. Based on the results of the
experiment, it is shown that the experimental data is the same as the data through the theory
which is the data that can be applied in this experimental heat pump. Furthermore, this
experimental objective has been achieved because, from this experiment it is possible to
know the process cycle in the thermodynamic of heat pump and can distinguish the ideal, real
and actual coefficient of performance.
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REFERENCE
WEB:
1. https://www.hydroone.com/savingmoneyandenergy_/energysavingsforbusiness_/Doc
uments/Heat_Pump_Reference_Guide.pdf.
2. http://www.nrcan.gc.ca/energy/publications/efficiency/heating-heat-pump/6827.
3. http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/heatpump.html.
BOOK:
1. Heat pumps: prospects in heat pump technology and marketing : proceedings of the
1987 International Energy Agency Heat Pump Conference, prospects in heat pump
technology and marketing, Orlando, Florida, April 28-30, 1987, Kay H. Zimmerman,
Raleigh H. Powell, International Energy Agency, Lewis Publishers, 1987.
2. The Heat Pump Service, Dennis Wash, California State University, Fresno., 1977.
3. Heat Pump Technology, Hans Ludwig Von Cube, Fritz Steimle, Elsevier, 2013.
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