TABLE OF CONTENTS
ABSTRACT………………………………………………………………………………... iii
1. TITLE…………………………………………………………………………...1
2. INTRODUCTION……………………………………………………………....1
3. THEORY………………………………………………………………………. 2
4. OBJECTIVES………………………………………………………………….. 4
5. PROBLEM STATEMENT…………………………………………………….. 4
6. MATERIALS AND APPARATUS……………………………………………. 5
7. METHODOLOGY ……………………………………………………………..5
8. TABULATION OF DATA……………………………………………………..6
8.1 Observed Data
8.2 Analysed Data
9. DATA ANALYSIS…………………………………………………………….. 8
9.1 Formulae
9.2 Sample Calculation
10. GRAPHS……………………………………………………………………….. 12
11. DISCUSSION………………………………………………………………….. 15
12. CONCLUSION………………………………………………………………....17
REFERENCES……………………………………………………………………………...27
Abstract
Air conditioning is a system for controlling the humidity, ventilation and temperature
in a building or vehicle, typically to maintain a cool atmosphere in warm conditions. This
module provides an overview and displays the basic thermodynamic cycle found in air
conditioning systems. The refrigeration unit apparatus has been designed to provide a practical
and quantitative demonstration of a vapor compression cycle or the refrigeration cycle which
is crucial in any appliances involving cooling and also heating processes. Refrigerators and
heat pumps both apply the vapor compression cycle. Although the applications of these
machines quite differ, the components are essentially the same. The refrigeration unit is able
to demonstrate the result or effect when the flow rate of cooling water is adjusted to a certain
amount. This will allow the study of the performance curve and efficiency of refrigeration unit
with respect to the varying flow rates and other manipulating variables. This apparatus is
equipped with control valves for the cooling water flow rate besides pressure, temperature and
compressor power output display which will make it easier to conduct the experiments with
the accurate data display. This simple vapor compression refrigeration cycle is displayed on a
visualization board that features all four major components of the systems which are
evaporator, condenser, compressor and expansion valve. In order to improve its efficiency,
temperature and pressure is taken at each stage of the cycle. Theoretically, as the pressure on a
liquid is increased, the boiling point rises. In an air conditioning system, a compressor is used
to increase the pressure of the refrigerant; this raises its temperature. The refrigerant vapor
entering the condenser is hot. The flow control device is used to lower the pressure of the
refrigerant making the refrigerant in evaporator cold. This shows that the performance relies a
lot on the pressure and temperature. Therefore, a discussion is done on our understanding
regarding the cycle and a total of six graphs were plotted including a graph of Coefficient of
performance (COP) against condenser water flow rate. COP is a ratio of useful heating or
cooling provided to work required, high COP equate to lower operating cost. In other words,
higher efficiency. Therefore, COP is calculated in order to analyze the system performance
under different working conditions. Thus, helping us to understand more on how to improve
the air conditioning system.
ii
1. Title
Air Conditioning: Vapor Compression Cycle
2. Introduction
Refrigeration cycle is a sequence of thermodynamic processes whereby heat is
withdrawn from a cold body and expelled to a hot body. It is a reversed heat engine cycle. In
general words refrigeration refers to the process of removing heat from an enclosed space, or
from a substance, to lower its temperature. The device whose prime function is to do the job is
known as refrigerator and the working fluids used in the refrigeration cycle is called refrigerant.
A refrigerator uses the evaporation of a liquid to absorb heat. The liquid, or refrigerant, used in
a refrigerator evaporates at a low temperature, creating cooling or freezing temperatures inside
the refrigerator. Evaporators and condensers of the system is used for the absorption and
rejection of heat respectively involved the fields of heat transmission (Al Mahbub, 2013).
Refrigeration implies the maintenance of a temperature below that of the surroundings.
This requires continuous absorption of heat at a low temperature level usually accomplished
by evaporation of a liquid in a steady-state flow process. The vapor reformed to liquid state for
re-evaporation generally by compressing and then condensing by rejecting heat at a higher
temperature consecutively. According to the second law of thermodynamics it requires an
external source of energy or external work done on the system to transfer heat from a lower
temperature level to a higher one.
A refrigerator is shown schematically in Figure 2.1. Here QL is the magnitude of the
heat removed from the refrigerated space at temperature TL. QH is the magnitude of the heat
rejected to the warm space at temperature TH, and Wnet, in is the net work input to the refrigerator
(R).
Figure 2.1. Schematic diagram of refrigerator
1
The applications of refrigeration are numerous in our daily life. The most widely used
current applications of refrigeration are for air conditioning of private homes and public
buildings, and refrigerating foodstuffs in homes, restaurants and large storage warehouses. In
commerce and manufacturing, there are many uses for refrigeration. Refrigeration is used to
liquefy gases - oxygen, nitrogen, propane and methane, for example. In compressed air
purification, it is used to condense water vapor from compressed air to reduce its moisture
content. In oil refineries, chemical plants, and petrochemical plants, refrigeration is used to
maintain certain processes at their needed low temperatures. Textile mills uses refrigeration in
mercerizing, bleaching, and dyeing. Manufacturers of paper, drugs, soap, glue, shoe polish,
perfume, celluloid, and photographic materials. Fur and wooden goods storage could beat the
moths by using refrigerated warehouses (Application, 2017). So, it is important to have a
general knowledge on refrigeration which has prompted to conduct the experiment.
3. Theory
The distinction between refrigeration, air conditioning, and heat pumping is primarily in
the services provided, rather than in the essentially common cycle, namely: Refrigeration refers
to cooling by a thermodynamic cycle of processes or materials including food. Air
conditioning refers to cooling, and dehumidification when required, of air for environmental
or equipment control. Air conditioning is commonly associated with building or space comfort
systems. Heat pumping refers to heating of either air or other substances, such as domestic
water, and may also, in a reversed mode, include air conditioning or refrigeration. These are
very significant differences in the actual equipment engineering and system design (James,
1984). Although the applications of these machines quite differ, the components are essentially
the same.
The Clausius statement of the second law of thermodynamics states that heat will not pass
from a cold to a hotter region without the aid of an external agency (Sharma, 1997). Thus, a
refrigerator will require an input of high-grade energy for it to operate. The most common type
of refrigerator uses a work input and operates on the Vapor compression cycle. The work
input to the Vapor Compression Cycle derives a compressor which maintains a low pressure
on an evaporator and a higher pressure in condenser. The temperature at which a liquid will
evaporate (or a vapor will condense) is dependent on pressure, thus if a suitable fluid is
introduced it will evaporate at a low temperature in the low pressure evaporator (taking in heat)
and will condense at a higher temperature in the high pressure condenser (rejecting heat). The
high-pressure liquid formed in the condenser must then be returned to the evaporator at a
controlled rate. Thus, the simple vapor compression refrigeration cycle has four main
components,
(1)
An evaporator where heat is taken in at a low temperature as a liquid evaporator at a
low pressure.
(2)
A compressor which uses a work input to reduce the pressure in the evaporator and
increase the pressure of the vapor being transferred to the condenser.
2
(3)
A condenser where the high pressure vapor condenser, rejecting heat to its
surroundings.
(4)
An expansion valve which controls the flow of liquid back to the evaporator and which
brings about the pressure reduction.
Figure 3.1. Schematic diagram of vapor compression cycle
In general, the thermal efficiency, ηth, of any heat engine as the ratio of the work it does, W, to
the heat input at the high temperature, QH.
But in heat pumps and refrigerators, the work is not an output. For a refrigeration or heat
pumps, thermal efficiency indicates the extent to which the energy added by work is converted
to net heat output. From an economic point of view, the best refrigeration cycle is one
that removes the greatest amount of heat from the inside of the refrigerator (cold reservoir) for
the least expenditure of mechanical work or electric energy. The relevant ratio is therefore the
larger this ratio, the better the refrigerator. We call this ratio the coefficient of performance,
denoted by COP.
In general, the thermal efficiency, ηth, of any heat engine as the ratio of the work it does, W, to
the heat input at the high temperature, QH.
𝐶𝑂𝑃 =
𝑄𝑐𝑜𝑙𝑑
𝑊
As can be seen, the better (more efficient) the refrigerator is when more heat Qcold can be
removed from the inside of the refrigerator for a given amount of work. Since the first law of
3
thermodynamics must be valid also in this case (Qcold + W = Qhot), we can rewrite the above
equation:
𝐶𝑂𝑃 =
𝑄𝑐𝑜𝑙𝑑
𝑄𝑐𝑜𝑙𝑑
=
𝑊
𝑄ℎ𝑜𝑡 − 𝑄𝑐𝑜𝑙𝑑
For an ideal refrigerator (without losses and irreversibilities) can be derived that:
𝐶𝑂𝑃 =
𝑇𝑐𝑜𝑙𝑑
𝑇ℎ𝑜𝑡 − 𝑇𝑐𝑜𝑙𝑑
These formulas are applied also for an air conditioner, which works very much like a
refrigerator.
4. Objectives
The objectives of this experiment were to be familiar with the refrigeration process and the
essential parts or units of the system (i.e., evaporator, compressor, condenser, and throttling
device or expansion valve) and also to know basic thermodynamics related to this process.
Specifically, this experiment aimed at the vapor compression refrigeration cycle with visual
observation including the investigation of the saturation pressure-temperature relationship
during evaporation and condensation, effect of evaporating and condensing temperature on
refrigeration rate, effect of compressor pressure ratio on system performance and to determine
the overall heat transfer coefficient.
5. Problem Statement
As refrigeration has become one of the basic needs to modern people, it is important to know
the actual working principle of the refrigerator so that the users can always maintain the
refrigeration system at its maximum performance. Therefore, a study is needed to analyse the
actual performance of refrigeration cycle to determine the optimum COP. Understanding of air
conditioning system will help engineers to improve the performance of the system thus helping
to further design a low cost with an energy saving potential, as well as high efficiency air
conditioning unit. Besides, we have to study all the components of refrigeration unit and its
processes to relate it with thermodynamics law involve in order to enhance the knowledge thus
creating a platform for further improvement and development of the study area. It is also
important to understand the elements which play a major role in the performance of the Vapor
compression cycle such as the pressure and temperature of the condenser and evaporator of the
air conditioning unit.
4
6. Materials and Apparatus
Temperature indicator, Pressure gauge, Compressor, Evaporator, Condenser, Flowmeter, Main
switch, Tube, Cooling water supply, Valves, Refrigerant
Figure 6.1. Schematic diagram of Refrigeration Demonstration Unit R634
7. Methodology
1. The cooling water supply and the main supply were turned on.
2. The water supply was turned on and the control valves on the evaporator water flowmeter and condenser water flow-meter was adjusted to approximately 8-12 𝑔 𝑠 −1 and
30 𝑔 𝑠 −1 respectively.
3. The main switch was turned on and the compressor started and two internal lamps
lighted up.
4. The normal operation was started by increasing the condenser cooling water flow to the
flow-meter maximum (12 𝑔 𝑠 −1 ). The pressure when the condenser stabilised depend
on the water inlet temperature.
5. The unit was running for approximately 15 minutes in order to reach a uniform
operating temperature. The condenser pressure, 𝑃𝑐 , evaporator pressure, 𝑃𝑒 , condensing
temperature, 𝑡6 and evaporating temperature, 𝑡5 was recorded.
6. The procedure was repeated up to the maximum condenser pressure required or to the
high pressure cut out value of 220 𝑘𝑁 𝑚−2.
5
8. Tabulation of Data
8.1 Data Observed
Observation
1
2
3
4
5
Condenser Water Flow Rate (g/s)
12
11
10
9
8
Evaporator Water Flow Rate (g/s)
30
30
30
30
30
Condenser Pressure (kN/m2)
200
207
209
211
215
Evaporator Pressure (kN/m2)
-60
-60
-58
-60
-59
Evaporator Water Inlet Temperature, T1 (˚C)
27.5
27.7
27.8
27.9
27.9
Evaporator Water Outlet Temperature, T2 (˚C)
26.4
26.5
26.5
26.5
26.6
Condenser Water Outlet Temperature, T3 (˚C)
31.3
31.8
32.5
33.1
33.9
Condenser Water Inlet Temperature, T4 (˚C)
27.9
28.1
28.2
28.2
28.3
Evaporator Temperature, T5 (˚C)
17.5
16.3
16.3
16.1
15.7
Condenser Temperature, T6 (˚C)
42.2
43.5
44.4
45.2
45.8
Compressor Discharged Temperature, T7 (˚C)
70.0
70.5
70.9
71.2
71.4
Condensed Liquid Temperature, T8 (˚C)
15.9
16.4
17.2
17.9
18.3
Table 8.1a: Observed Data for Vapor Compression Refrigeration Cycle
6
8.2 Data Analyzed
Observation
Evaporator
Evaporator Compressor
absolute
Pressure
𝑷
pressure,
Ratio, 𝑷𝒄
𝒆
𝐾𝑁
𝑷𝒆 ( 𝑚 2 )
1
2
3
4
5
1
2
3
4
5
7.29
7.46
7.16
7.56
7.47
Condenser
Condenser
absolute
pressure,
Compressor
Pressure
𝑻𝒐𝒖𝒕
(˚C)
137.94
150.48
163.02
175.56
163.02
8.9
10.2
10.2
10.4
10.9
10.0
11.4
11.5
11.8
12.2
∆𝑻𝑳𝑴𝑻𝑫 evaporator
overall
(˚C)
heat
transfer
coefficient,
𝑼𝒆
(𝑊/𝑚2 °𝐶)
9.44
456.63
10.79
435.82
10.84
469.96
11.09
494.70
11.53
441.84
Rate of
𝑻𝒊𝒏 𝑻𝒐𝒖𝒕 ∆𝑻𝑳𝑴𝑻𝑫
heat
(˚C) (˚C) (˚C)
𝑷𝒄
transfer to
Ratio,
𝑷𝒆
𝐾𝑁
water in
𝑷𝒄 ( 𝑚 2 )
condenser,
𝑸𝒄
(W)
301.325
7.29
170.544
14.3 10.9 12.52
308.325
7.46
170.126
15.4 11.7 13.47
310.325
7.16
179.74
16.2 11.9 13.94
312.325
7.56
184.338
17.0 12.1 14.41
316.325
7.47
187.264
17.5 11.9 14.52
Table 8.2a: Calculated Data for Vapor Compression Refrigeration Cycle
Observation
1
2
3
4
5
41.325
41.325
43.325
41.325
42.325
Rate of
𝑻𝒊𝒏
heat
(˚C)
transfer to
water in
evaporator,
𝑸𝒆 (W)
Condenser Flow 𝑻𝑯 (K)
𝑻𝑳 (K)
Rate (g/s)
12
315.2
290.5
11
316.5
289.3
10
317.4
289.3
9
318.2
289.1
8
318.2
288.7
Table 8.2b: Calculated Data for COP
7
condenser
overall
heat
transfer
coefficient,
𝑼𝒄
(𝑊/𝑚2 °𝐶)
425.67
394.69
402.93
399.76
403.03
COP
11.76
10.64
10.29
9.93
9.79
9. Data Analysis
9.1 Formulae
1)
2)
3)
4)
5)
Absolute pressure = Gauge pressure (𝑝𝑒 ) + Atmospheric pressure (P)
Saturation pressure of evaporator, 𝑷𝒆 = 𝑝𝑒 + 𝑃
Saturation pressure of compressor, 𝑷𝒄 = 𝑝𝑐 + 𝑃
Rate of heat transfer for evaporator, 𝑸𝒆 = 𝑚̇𝑒 𝐶𝑝 (𝑡1 − 𝑡2 )
Rate of heat transfer for condenser, 𝑸𝒄 = 𝑚̇𝑐 𝐶𝑝 (𝑡3 − 𝑡4 )
𝑄
6) Overall heat transfer coefficient, 𝑼 = 𝐴×∆𝑇
𝐿𝑀𝑇𝐷
7) Logarithmic mean temperature difference, ∆𝑻𝑳𝑴𝑻𝑫 =
𝑇𝑖𝑛 −𝑇𝑜𝑢𝑡
𝑇
ln ( 𝑖𝑛 )
𝑇𝑜𝑢𝑡
𝟏
8) 𝑪𝑶𝑷𝑹,𝒓𝒆𝒗 = 𝑻𝑯
𝑻𝑳
where,
𝑪𝒑
−𝟏
𝑘𝐽
Specific Heat of Water (𝑘𝑔∙𝐾)
𝒎̇ 𝒆
𝒎̇ 𝒄
Evaporator water flow rate
Condenser Water Flow Rate
𝒕𝟏
Evaporator Water Inlet Temperature
𝒕𝟐
Evaporator Water Outlet Temperature
𝒕𝟒
Condenser Water Inlet Temperature
𝒕𝟑
Condenser Water Outlet Temperature
Temperature difference of water inlet and supplied refrigerant
𝑻𝒊𝒏
Temperature difference of water outlet and supplied refrigerant
𝑻𝒐𝒖𝒕
𝑪𝑶𝑷𝑹,𝒓𝒆𝒗 Coefficient of Performance
8
9.2 Sample Calculation
Example: Observation-1
Atmospheric pressure = 101.325KN/m3
Water coil surface area in Evaporator, 𝐴𝑒 = 0.032𝑚2
Water coil surface area in Condenser, 𝐴𝑐 = 0.032𝑚2
Evaporator gauge pressure, 𝑝𝑒 = −60𝐾𝑁/𝑚2
Evaporator absolute pressure, 𝑃𝑒 = (−60 + 101.325)𝐾𝑁/𝑚2
= 41.325𝐾𝑁/𝑚2
Condenser gauge pressure, 𝑝𝑐 = 200𝐾𝑁/𝑚2
Condenser absolute pressure, 𝑃𝑐 = (200 + 101.325)𝐾𝑁/𝑚2
= 301.325𝐾𝑁/𝑚2
𝑃
Compressor Pressure Ratio, 𝑃𝑐 =
𝑒
301.325
41.325
= 7.29
Evaporator Water Flow Rate 𝑚̇ 𝑒 = 30 g/s
Evaporator Water Inlet Temperature, 𝑡1 = 27.5 ˚𝐶
Evaporator Water Outlet Temperature, 𝑡2 = 26.4 ˚𝐶
Rate of heat transfer to water in evaporator, 𝑄𝑒 = 𝑚̇𝑒 𝐶𝑝 (𝑡1 − 𝑡2 )
= 30
𝑔
𝑘𝐽
× 4.18
× (27.5 − 26.4)°𝐶
𝑠
𝑘𝑔 ∙ 𝐾
= 137.94𝑊
Condenser Water Flow Rate 𝑚̇ 𝑐 = 12 g/s
Condenser Water Inlet Temperature, 𝑡4 = 27.9 ˚𝐶
Condenser Water Outlet Temperature, 𝑡3 = 31.3 ˚𝐶
Rate of heat transfer to water in condenser, 𝑄𝑐 = 𝑚̇𝑐 𝐶𝑝 (𝑡3 − 𝑡4 )
= 12
𝑔
𝑘𝐽
× 4.18
× (31.3 − 27.9)°𝐶
𝑠
𝑘𝑔 ∙ 𝐾
= 170.544𝑊
9
Evaporator,
𝑇𝑖𝑛 = (𝑡1 − 𝑡5 )
= (27.5 − 17.5)(˚𝐶)
= 10 ˚C
𝑇𝑜𝑢𝑡 = (𝑡2 − 𝑡5 )
= (26.4 − 17.5)(˚𝐶)
= 8.9 ˚C
∆𝑇𝐿𝑀𝑇𝐷 =
=
𝑇𝑖𝑛 − 𝑇𝑜𝑢𝑡
𝑇
ln (𝑇 𝑖𝑛 )
𝑜𝑢𝑡
10−8.9
10
)
8.9
ln (
˚C
= 9.44 ˚C
𝑄
For evaporator overall heat transfer coefficient, 𝑈𝑒 = 𝐴×∆𝑇
=
137.94
0.032 × 9.44
= 456.63 𝑊/𝑚2 °𝐶
Condenser,
𝑇𝑖𝑛 = (𝑡6 − 𝑡4 )
= (42.2 − 27.9)(˚𝐶)
= 14.3˚C
𝑇𝑜𝑢𝑡 = (𝑡6 − 𝑡3 )
= (42.2 − 31.3)(˚𝐶)
= 10.9 ˚C
∆𝑇𝐿𝑀𝑇𝐷 =
=
𝑇𝑖𝑛 − 𝑇𝑜𝑢𝑡
𝑇
ln (𝑇 𝑖𝑛 )
𝑜𝑢𝑡
14.3−10.9
14.3
)
10.9
ln (
˚C
= 12.52 ˚C
10
𝐿𝑀𝑇𝐷
𝑄
For condenser overall heat transfer coefficient, 𝑈𝑐 = 𝐴×∆𝑇
=
𝐿𝑀𝑇𝐷
170.544
0.032 × 12.52
= 425.67 𝑊/𝑚2 °𝐶
COPR,rev =
=
=
1
TH
TL − 1
1
T6
T5 − 1
1
(42.2 + 273)𝐾
−1
(17.5 + 273)K
= 11.76
11
10. Graphs
Temperature (°C) against Evaporator Water Flow Rate (g/s)
80
70
Temprature (°C)
60
50
40
30
20
10
0
30
30
30
30
30
Evaporator Water Flow Rate (g/s)
T1
T2
T3
T4
T5
T6
T7
T8
Figure 10.1. Graph of Temperature against Evaporator Water Flowrate
Temperature (°C) against Condenser Water Flow Rate (g/s)
80
70
Temprature (°C)
60
50
40
30
20
10
0
12
11
10
9
8
Condenser Water Flow Rate (g/s)
T1
T2
T3
T4
T5
T6
T7
T8
Figure 10.2. Graph of temperature against condenser water flowrate
12
Figure 10.3. Graph of rate of heat transfer vs condensing temperature for both
evaporator and condenser
Figure 10.4. Graph of rate of heat transfer vs compressor pressure ratio for both
evaporator and condenser
13
Condenser Pressure (kPa) against Condenser Water Flow
Rate (g/s)
220
Condenser Pressure (kPa)
215
210
205
200
195
190
12
11
10
9
8
Condenser Water Flow Rate (g/s)
Figure 10.5. Graph of condenser pressure against condenser water flowrate
Graph of COP against Condenser Water Flowrate
Coefficiant of Performance, COP
14
12
10
8
6
4
2
0
8
9
10
11
12
Condenser Water Flowrate (g/s)
Figure 10.6. Graph of coefficient of performance against condenser water flowrate
14
AWANG MOHAMAD IHSAN BIN AWANG JULAIHI
64660
11. Discussion
In this experiment, there are a few variables that are being measured. The variables are
the condenser pressure, evaporator pressure and temperatures of the air conditioner at certain
points. The air conditioner is being kept under constant evaporated water flow rate which is at
30 g/s and the condenser water flow rate decreases linearly throughout the experiment from 12
g/s to 8 g/s. Referring to table 8.1a, it can be clearly seen that when the condenser water flow
rate decreases, the condenser pressure increases. It can be state that the relationship between
the condenser water flow rate and the condenser pressure is inversely proportional to each
other.
Theoretically, since the evaporated water flow rate is constant, the evaporator should
also remain constant. However, this is not the case as it can be observed in table 8.1a, that the
evaporator pressure changes throughout the experiment. The evaporator changes from -60kPa
to -58kPa then back to -60kPa and finally -59kPa. Although there is a change in the pressure,
but the value is small ranging from only 1kPa to 2kPa only. This different in value may occurs
because of outside factors such as the environment temperature and pressure.
The temperature variables being observed in this experiment is divided into eight parts
or points on the air conditioner. The temperature variables are evaporator water inlet
temperature, evaporator water outlet temperature, condenser water outlet temperature,
condenser water inlet temperature, evaporator temperature, condenser temperature, compressor
discharged temperature and condensed liquid temperature which are being noted as T1, T2, T3,
T4, T5, T6, T7 and T8 respectively. Throughout the experiment, all the temperature with the
exception of T5 undergoes an increase in temperature. T5 undergoes decrease in temperature
because the coil in the evaporator absorbs heat thus resulting in the temperature area around
the coil to be cool. Although the temperature of variables experienced changes, there is still a
point where the temperature remains constant. This can be seen in table 8.1a where T1, T2, T4
and T5 experienced a constant temperature at a certain point. This happen because T1, T2, T4
and T5 had achieved thermal equilibrium with the surrounding at that point.
The coefficient of performance or also known as COP is a ratio of useful heating or
cooling provided to work required. Higher COP will result in lower operating cost. COP is
highly dependent on the operating condition, especially absolute temperature between sink and
system. The equation for COP is given below.
𝑸
COP = 𝑾
Where,
Q = useful heat supplied or removed by the system
W = the work required by the system
The condition of the air conditioner is assumed to be reversible. This is because the air
conditioner is assumed to be an ideal system. As mentioned before, higher COP will result in
lower operating cost. Thus, the ideal condition is to have a higher COP. A system consists of a
reversible process always have a greater COP than a system which consist of an irreversible
process at the same temperature.
15
Referring to table 8.2c, it can be observed that when the condenser flow rate decreases,
the coefficient of performance also decreases. It can be said that the condenser flow rate and
the coefficient of performance of system is directly proportional to each other. Therefore, the
greater the condenser flow rate, the closer the air conditioner to become an ideal system.
Figure 13 and 14 shows the theoretical graph that should be plot from the result. Figure 13
represent the theoretical graph for figure 10.3 and figure 14 represent the theoretical graph for
figure 10.4. However, both of the laboratory result graph differ from their respective theoretical
graph. In figure 13, the theoretical result for condensing temperature of evaporator should be
constant while the condensing temperature of condenser should decrease throughout the
experiment. But this is not the case as it can be observed in figure10.3 both the condensing
16
temperature for both evaporator and condenser tend increase. The same problem also applies
to both figure 14 and figure 10.4. In figure 14, the theoretical result for pressure ratio of
evaporator should be constant while the pressure ratio for condenser should decrease
throughout the experiment. Figure10.4 also act in the same way as figure 10.3 where both of
the pressure ratio for evaporator and condenser tend to increase throughout the experiment.
The result of the experiment differ from its theoretical result may be caused by the errors that
takes place during the experiment. The error that may takes place is parallax errors. The eye
level of observer may not be perpendicular with the device scale. Other than that, systematic
error also occurred. The air conditioner has a maximum limit of 220kPa for its condenser
pressure. If the pressure exceed the 220kPa, the device will shut down immediately. The time
taken for the system to stabilize will approximately be 10 minutes. This become an
inconvenient as it disrupt the progress of the experiment and the time limit to carry out an
experiment is only an hour.
AWANG MOHAMAD IHSAN BIN AWANG JULAIHI
64660
12. Conclusion
In conclusion, the working principle of air conditioner and how the system works can
be understood by analysing the temperature change for T1 to T8. Air conditioner does not cool
the air which is a common misconception in Malaysia. Air conditioner actually takes away the
heat through the evaporator and release heat through the condenser. Furthermore, it can be
observed that the condenser water flow rate and the condenser pressure is inversely
proportional to each other. Other than that, the condenser flow rate and the coefficient of
performance of system is directly proportional to each other. It is important to know that higher
COP will results in lower operating cost. This concept is important because it can be applied
not only to air conditioner but also to other devices that use the heat pump or refrigerator
system.
17
AZLAN HAZIQ BIN AMIROOL
64663
11. Discussion
Based the experiment conducted, the mass flow for the evaporator were kept constant at
30 𝑔 𝑠 −1 meanwhile the mass flow rate for the condenser were reduced from 12 𝑔 𝑠 −1 to
8 𝑔 𝑠 −1 . The evaporator pressure,𝑃𝑒 , condenser pressure,𝑃𝑐 , the condensing temperature,𝑡6 and
evaporating temperature,𝑡6 were recorded.
Throughout the experiment, the mass flow rate for the evaporator were kept constant at
30 𝑔 𝑠 −1 . The values obtained is recorded from 12 𝑔 𝑠 −1 to 8 𝑔 𝑠 −1 . The value of evaporator
absolute pressure remained constant from 12 𝑔 𝑠 −1 to 11 𝑔 𝑠 −1 at 41.325 𝑘𝑁 𝑚−2 and then
increased at 10 𝑔 𝑠 −1 with a value of 43.325 𝑘𝑁 𝑚−2. After that the value decreased to
41.325 𝑘𝑁 𝑚−2 and 42.325 𝑘𝑁 𝑚−2 at 9 𝑔 𝑠 −1 and 8 𝑔 𝑠 −1 respectively. These readings were
due to the mass flow rate of the evaporator were kept constant.
The values of condenser absolute pressure from 12 𝑔 𝑠 −1 to 8 𝑔 𝑠 −1 were continuously
increasing throughout the experiment which is from 301.325 𝑘𝑁 𝑚−2 to 308.325 𝑘𝑁 𝑚−2 to
310.325 𝑘𝑁 𝑚−2 to 312.325 𝑘𝑁 𝑚−2 to 316.325 𝑘𝑁 𝑚−2 respectively. As the mass flow rate
for the condenser decreases, the condenser absolute pressure will decrease. This shows that it
is inversely proportional.
Coefficient of Performance, COP, is defined as the heat removed from the cold reservoir
divided by the work done to remove the heat by the compressor. Based on the values obtained
from calculations, the values of COP when the condenser flow rate was from 12 𝑔 𝑠 −1 to
8 𝑔 𝑠 −1 are 11.76, 10.64, 10.29, 9.93 and 9.79 respectively.
The machine was warmed up for at least 15 minutes to obtained more accurate results. This
also reduce the errors that may occurred throughout the experiment. The machine will start up
whenever the evaporator pressure reaches 220 𝑘𝑁 𝑚−2 where systematic error may occur.
Therefore, the evaporator pressure should be observed from time to time throughout the
experiment.
AZLAN HAZIQ BIN AMIROOL
64663
12. Conclusion
Based on the results and graphs obtained after conducting the experiment, we have learnt
how the air conditioning systems worked. This fulfilled the objective of the experiment. As we
know, this system will act differently according to the needs of the region. As in Malaysia, this
system is used for air conditioning to lower the temperature of a certain space. From the result
obtained, we can conclude that the condenser absolute pressure increases as the mass flow rate
of condenser decreases. Due to the values of mass of flow rate for evaporator were constant
throughout the experiment, the difference in the absolute pressure for the evaporator were not
too obvious. Therefore, the relationship between the absolute pressure and the mass flow rate
cannot be conclude.
18
BRYANT DANA MERING
64671
11. Discussion
Based on my knowledge and after conducting experiment related to air conditioning,
air conditioning is a process associated with the removal of heat from the air condensation
process that occur in the evaporator. This is mainly because the refrigerant which is at a low
pressure and low saturation temperature subcooled state enters the evaporator. Refrigerant
undergo evaporation by absorbing heat from the surrounding due to the evaporator greater
temperature. In other words, surrounding in the evaporator loses thermal energy. Thus, it can
be said that the air passing through the evaporator also loses thermal heat energy and undergoes
condensation. Resulting in temperature of air much be cooler when it leaves the evaporator.
The compressor then sucks in and compresses the cool refrigerant gas, causing it to become
hot, high pressure gas.
In the experiment conducted, we kept the evaporator water flow rate constant at
30𝑔 𝑠 . We chose the condenser water flow rate to act as the manipulated variable. We started
off by setting the condenser water flow rate at 12𝑔 𝑠 −1 followed by 11𝑔 𝑠 −1 and so on until
8𝑔 𝑠 −1 . While this goes on, the pressure and temperature for both condenser and pressure are
recorded at every interval. Also, we make sure to always observe the pressure of evaporator
does not reach 220 𝑘𝑁 𝑚−2 . When this happens, the module of simple-vapor compression
refrigeration cycle will restart and we have to start all over again.
−1
When the condenser water flow rate acts as the changing variable while evaporator
water flow rate is fixed, we found out that there is a change in pressure of the condenser. It can
be seen that the condenser pressure increases gradually with the condenser water flow rate.
However, the evaporator pressure stays at an average of -60 kN/m2. The same pattern is
observed for the temperature of water inlet and outlet for both condenser and evaporator where
the evaporator is averagely constant throughout while the condenser has a slight increase.
Whereas for the temperature, the evaporator decreases throughout the experiment while
temperature at condenser increases. The compressor discharged temperature and condensed
liquid temperature both increase as the experiment goes on. Graph 1, graph 2 and graph 3
visualized the result that is obtained during the experiment.
Theoretically, when plotting of rate of heat transfer against compressor pressure ratio
for both evaporator and condenser it should look like the graph below. Where the heat transfer
for evaporator should be fixed as condensing temperature increase. However, the heat transfer
of condenser decreases gradually. The same result should be obtained when plotting graph of
rate of heat transfer against compressor pressure ratio for both evaporator and condenser. Due
to errors, we get the graph showing the rate of heat transfer for both condenser and evaporator
slightly increase with the condensing temperature. The same can be concluded with the graph
of heat transfer for both condenser and evaporator against compressor pressure ratio.
19
Coefficient of performance (COP) is a ratio of useful heating or cooling provided to
work required, high COP equate to lower operating cost. In other words, higher efficiency.
Therefore, COP is calculated in order to analyse the system performance under different
working conditions. From the graph plotted, the COP increases as condenser water flow rate
increase. Meaning, higher condenser water flow rate, higher efficiency.
There are differences when comparing the experimental result and theoretical result.
This is due to errors during conducting the experiment. The obvious error that may happen
during the experiment and affecting our result is when changing the water flow rate, we had to
wait for some time in order for the system to stabilized. Only then, we are able to record the
result obtained. However, the time given for the experiment is only 1 hour. Therefore, due to
the shortage of time, the result obtained in this experiment is disrupted.
BRYANT DANA MERING
64671
12. Conclusion
As a conclusion we are able to understand the working principle of air conditioner even
deeper after analysing the temperature and pressure at every stage in the system. Air
conditioning systems efficiency is based on how it moves heat. Heat flows in air conditioning
by heat transfer. Compressor in the system sucks in and compresses the cool refrigerant gas
from the evaporator, causing it to become hot, high pressure gas. This shows that air
conditioning does not only produces cool air like what most people in hot countries imagined.
In cold countries, this concept can be used as heaters. The experimental results indicated that
air can be conditioned to desired levels to maintain the health and comfort of the occupants or
to meet requirements of industrial process irrespective of the external climatic conditions. The
experiment is successful as the aim of the experiment was achieved.
20
FARID HAMIZAN BIN ROSLAN
64733
11. Discussion
The vapor compression refrigeration cycle is a common method for transferring heat
from a low temperature to a high temperature. The refrigeration lab was conducted to gain a
better understanding of the vapor-compression refrigeration cycle and to compare the ideal
cycle with a real cycle.
In this experiment, SES36 was used as the refrigerant and the mass flow rate of water coming
into the condenser was varied while the evaporator water mass flowrate was kept constant.
From this, variation data was obtained and analysed. Liquids absorb heat when changed from
liquid to gas and gases give off heat when changed from gas to liquid. For an air conditioning
system to operate with economy, the refrigerant must be used repeatedly.
For this reason, all air conditioners use the same cycle of compression, condensation,
expansion, and evaporation in a closed circuit. The same refrigerant is used to move the heat
from one area, to cool this area, and to expel this heat in another area. The refrigerant comes
into the compressor as a low-pressure gas, it is compressed and then moves out of the
compressor as a high-pressure gas. The gas then flows to the condenser. Then, gas condenses
to a liquid, and gives off its heat to the outside air.
The liquid then moves to the expansion valve under high pressure. This valve restricts the flow
of the fluid and lowers its pressure as it leaves the expansion valve. The low-pressure liquid
then moves to the evaporator, where heat from the inside air is absorbed and changes it from a
liquid to a gas. As a hot low-pressure gas, the refrigerant moves to the compressor where the
entire cycle is repeated.
Based on the understanding of the cycle, we can relate it with why certain temperature
increase in temperature and some decrease in temperature. By keeping evaporator water flow
rate constant at 30g/s, condenser water mass flowrate was varied from 12g/s to 8g/s to study
its influence on the performance characteristics of the refrigeration unit and the influence in the
temperature. We decided to adjust the condenser water flow rate because it has major effect on
the compressor pressure. We have to make sure that the pressure does not exceed 220 N/m2 or
the unit system specifically the compressor will shut down due to safety reason.
Performance characteristics of the refrigerator against the condenser water mass flowrate are
presented in Table 8.1a. Variation of the condensing and evaporating pressures and temperature
with the condenser water mass flowrate are illustrated in Fig. 10.1 and 10.2. As we decrease
the water flowrate into the coil in the condenser, note that the pressure will increase. The
refrigerant enters the condenser as a superheated (hot) high pressure gas, the condensation of
refrigerant takes place at high pressure and then releasing heat to the surrounding air which is
then being absorbed by the water in the coil. As a result, we can see the increase in condenser
temperature and condenser water outlet temperature denoted as T6 and T3 respectively.
As in the evaporator, the increase of temperature of water is not that obvious. The rate of heat
taken away by the water is nearly the same as we maintain the evaporator water mass flowrate
at 30g/s. However, the evaporator temperature shows decrease in value which means the
cooling effect increases. In the evaporator, the refrigerant enters as a cold, low pressure
21
liquid but quickly begins to boil due to low pressure and low temperature. The refrigerant has
a very low boiling temperature, typically of -23ºc (Evans, 2015). As the refrigerant boils it
evaporates, this phase change from liquid to gas picks up the rooms heat and carries it away
towards the compressor where the refrigeration cycle will begin again. This explains why the
temperature in the evaporator is cooled down to average temperature of 16˚C.
Based on table 8.2, the rate of heat transfer to water for both condenser and evaporator is highly
depended on the pressure ratio. Clearly, higher condenser water mass flowrate yields lower
pressure ratio and rate of heat transfer for both condenser and evaporator. This is because the
condenser pressure change is higher than that of evaporator pressures, thereby the pressure
ratio (Pc/Pe) decreases as the condenser water flowrate increases. Other than that, table 8.2a
also shows the increasing trend of rate of heat transfer and logarithm mean temperature
difference as we decrease the condenser water flowrate.
Figure 11.1. Theoretical graph of heat transfer against compressor pressure ratio for both
evaporator and condenser
The theoretical curve for the Rate of heat transfer vs. Compressor pressure ratio shows that the
heat transfer at the condenser decreases as the compressor pressure ratio increases (Al Mahbub,
2013). From the graph it can be seen that the evaporator curve is parallel to x-axis and
condenser curve makes a negative slope. But form the experimental graph it can be seen that
the evaporator curve is not parallel to x- axis and condenser curve is different from the
theoretical one. Here heat transfer rate for both evaporator and condenser increase with
compressor pressure ratio which may be due to the discrepancies like pressure variation,
reading error etc.
Table 8.2b presents variation of COP with condenser water mass flowrate which also illustrated
on Fig. 10.6. As condenser water mass flowrate increases, COP increases. Based on Table 4.1c:
Calculated Data for COP and graph of COP against condenser water flow rate, the highest COP
calculated is 11.76 at condenser flow rate of 12g/s. The variation of COP depending on the
difference in condenser and evaporator temperature assuming that the work from electrical
22
energy supply is the same. From an economic point of view, the best refrigeration cycle is one
that removes the greatest amount of heat from the inside of the refrigerator (cold reservoir) for
the least expenditure of mechanical work or electric energy. The relevant ratio is therefore the
larger this ratio, the better the refrigerator. Theoretically, the higher the COP, the more energyefficient the system and lower electricity costs. The refrigeration system is assumed to be
reversible. Thus, the higher the condenser flow rate, the higher the COP, hence, more energyefficient the system and lower electricity cost.
As the experiment was mainly descriptive, it is difficult to quantify any errors. Instead,
the systematic and experimental errors and improvements for the experiment and the air
conditioning unit are discussed. The experiment was conducted within a 2-hour session, this
time constraint limited the time that could be used for stabilisation of the unit and the
observation made is limited to certain extend. All readings were taken from digital scales which
were fluctuating, increasing the error in the results.
FARID HAMIZAN BIN ROSLAN
64733
12. Conclusion
The experiment has been performed to study various components of a refrigeration unit
physically and operating it at different operating modes to get acquainted with the processes
and all of its essential parts and also to know the thermodynamic basics of refrigeration
thoroughly and specially the overall heat transfer coefficient so that the operations may become
well known to us and a platform for further modification can be created.
In conclusion, the system and how it works is understood by analysing and discussing the
temperature change observed by the variation of the water mass flowrate. In air conditioning
where the main components which are the evaporator, condenser, compressor and the
expansion valve play the important role in achieving the thermal comfort and our daily life
needs depending on the application. From the experimental results, it can be stated that as mass
flow rate decrease, the capacity of water carrying heat decrease, hence, the temperature
difference decrease. Besides, the pressure and the temperature will affect the phase change of
the refrigerant thus results in the temperature difference especially in condenser and evaporator.
Also, the higher the condenser flow rate, the higher the COP, hence, more energy-efficient the
system and lower electricity cost. Due to the systematic and experimental errors, some of the
results do not reflect with the theoretical one.
Objectives are achieved.
23
KHAIRUL ANWAR BIN ZAINUDDIN
64816
11. Discussion
Air-conditioning is based on refrigerator that requires input work and operates on the
vapour compression cycle. It has four components, which consists of evaporator, compressor,
condenser and flow control device. The purpose of air conditioning is to alter the properties of
air to bring comfortable conditions in an occupied space. In other words, to achieve desired
thermal comfort. In Malaysia, air-conditioning objective is to lower the air temperature, since
Malaysia has tropical weather that has range of 20ºC to 30ºC (Travel Online, 2019).
In the air conditioning system, the first and second laws of thermodynamics are
applicable and used in the system. The first law of Thermodynamics states that when a system
undergoes a thermodynamics cycle, the net heat is supplied to the system from the
surroundings. This means the absorption of heat by refrigerant in air-conditioning system is
equal to net work done by all air conditioning system on its surrounding. It is also stated that
energy is conserved. Thus, energy is conserved in the system by having evaporator and
condenser. In Clausius statement of the second law of Thermodynamics, heat is taken in from
a cold environment, work is applied, and heat is expelled to a hot environment. This statement
clearly matches the air-conditioning process, where, in order to make an occupied space colder,
heat is removed to hotter surrounding.
Generally, air conditioners use refrigeration to chill indoor air, which evaporate
refrigerant and condense it in a closed system of coils. Refrigerant has properties enabling them
to change at relatively low temperatures. Air conditioners consists fans that move warm interior
air over refrigerant-filled coils. When hot air flows over the cold, low-pressure evaporator coils,
the refrigerant inside absorbs heat as it changes from a liquid to a gaseous state. To keep cooling
efficiently, the air conditioner has to convert the refrigerant gas back to a liquid again. To do
that, a compressor puts the gas under high pressure, a process that creates unwanted heat. All
the extra heat created by compressing the gas is then evacuated to the outdoors with the help
of a second set of coils called condenser coils, and a second fan. As the gas cools, it changes
back to a liquid, and the process starts all over again (Marshall Brain, 2019).
Based on Table 8.1a: Observed Data for Vapor Compression Refrigeration Cycle, the
𝑔
experiment starts by keeping the evaporator water flow rate at constant 30 𝑠 and condenser
𝑔
𝑔
𝑔
𝑔
𝑔
water flow rate at 12 𝑠 , 11 𝑠 , 10 𝑠 , 9 𝑠 , and lastly 8 𝑠 . Observation 1 as the example, in the
evaporator, at T1, the reading is higher than T2 (27ºC>26.4ºC). This is because as water flows
from water inlet(T1) flows in the evaporating coils. Since the temperature of the water inlet is
higher, the coils have higher temperature at this point, it is able to evaporate the refrigerant due
to effect of very low boiling point of the very low pressure and temperature refrigerant in the
evaporator. At T5(17.5ºC), the reading is decrease because more heat is absorbed by the
evaporating coils, where at this point liquid is evaporated to colder gas. This indicates why
when touch with bare hands, the evaporator is colder, because heat is absorbed in the evaporator
processes. At T7(70.0ºC), the reading increase because compressor purpose is to increase
temperature and pressure of refrigerant gas. In other words, the gas is compressed. At this point,
the reading of T7 is higher than the surrounding so that it is easier to eject heat to condenser.
The flows continue to condenser. At T4, the reading is lower than T3(27.9ºC<31.3ºC), and
24
T6[42.2ºC>(27.9ºC<31.3ºC)] reading is the highest in the condenser part, which is higher than
surrounding due to thermal inertia (Mahbub, 2013). In the condenser, heat is released. This is
because water flows from water inlet (T4) throughout the condenser coils, this make the hotter,
higher pressure gas condense to colder, lower pressure liquid due to the temperature difference.
The water flows absorbed some heat from the released heat of gas which indicates why the
reading of T3 is higher than T4. This is why when touch with bare hands, the condenser is
hotter. This is because the vapor is condensed, where gas turned to liquid. The flows continue
to expansion valve. The purpose of expansion valve is to restrict refrigerant flows, so that the
pressure will decrease drastically. The liquid become sudden cold with much lower pressure
due to throttling effect of orifice, which is the reason for T8(15.9ºC) reading lower than room
temperature. The flows continue to evaporator hence cycle happens. Overall, from observation
1 to 5, Evaporator Temperature (𝑇5 ) shows decreasing trend. For observations where increasing
trends or readings increase, those are Condenser Pressure, Evaporator Water Inlet Temperature
(𝑇1 ), Evaporator Water Outlet Temperature (𝑇2 ), Condenser Water Inlet Temperature (𝑇4 ),
Condenser Water Outlet Temperature (𝑇3 ), Condenser Temperature (𝑇6 ), Compressor
Discharged Temperature (T7) and Condensed Liquid Temperature (T8).
In Graph 10.1: Temperature against Evaporator Water Flow Rate and in Graph 10.2:
Temperature against Condenser Water Flow Rate, both graphs show very similar pattern.
Overall, from observation 1 to 5, when condenser water flow rate decrease, Evaporator
Temperature (𝑇5 ) decrease. However, Condenser Pressure, Evaporator Water Inlet
Temperature (𝑇1 ), Evaporator Water Outlet Temperature (𝑇2 ), Condenser Water Inlet
Temperature (𝑇4 ), Condenser Water Outlet Temperature (𝑇3 ), Condenser Temperature (𝑇6 ),
Compressor Discharged Temperature (T7) and Condensed Liquid Temperature (T8) are
increase. As mass flow rate decrease, the heat carrying the capacity water decrease, hence, the
temperature difference decrease. The effect of the temperature difference especially in
condenser will affect the phase change of the refrigerant, the pressure and the temperature. In
Graph 10.3: Condenser Pressure against Condenser Water Flow Rate, as condenser water flow
rate decrease, the condenser pressure increase. According to Bernoulli’s principle, as the speed
of moving fluid increases, the pressure within the fluid decreases.
Based on Table 8.2a: Calculated Data for Vapor Compression Refrigeration Cycle for
evaporator, Temperature difference of water inlet and supplied refrigerant (Tin), Temperature
difference of water outlet and supplied refrigerant (Tout) and Logarithmic mean temperature
difference (∆TLMTD) show increasing trends. For Table 4.1b: Calculated Data for Vapor
Compression Refrigeration Cycle for condenser, Temperature difference of water inlet and
supplied refrigerant (Tin) and Logarithmic mean temperature difference (∆TLMTD) show
increasing trends.
Based on the graph of rate of heat transfer against condensing temperature for both evaporator
and condenser, as condensing temperature increase, the rate of heat transfer for evaporator and
condenser increase. However, theoretically, the effect of increasing the condensing temperature
is a reduction in the heat released from condenser and smaller reduction in the refrigerating
effect in the evaporator (Mahbub, 2013). There might be some errors such as pressure variation
and reading error.
25
Based on the graph of rate of heat transfer vs compressor pressure ratio for both evaporator and
condenser, it can be seen that the condenser trend is almost parallel to x-axis, while evaporator
trend slightly increase. Theoretically, condenser trend decreases and evaporator trend parallel
to x-axis as compressor pressure ratio increase (Mahbub, 2013).
Based on Table 8.2b: Calculated Data for COP and graph of COP against condenser
water flow rate, it is found that the highest COP is 11.76 at condenser flow rate of 12g/s, where
evaporator water flow rate is kept constant. The definition of the coefficient of performance
(COP) of air conditioning system is a ratio of useful cooling provided to work required
(Wikipedia, 2019). Theoretically, the higher the COP, the more energy-efficient the system
and lower electricity costs. The refrigeration system is assumed to be reversible. Thus, the
higher the condenser flow rate, the higher the COP, hence, more energy-efficient the system
and lower electricity cost.
There might be some errors while conducting the experiment. First, pressure of
condenser was increasing rapidly and not stable enough to get accurate values of temperature
for corresponding pressure of condenser. Secondly, the air sensitivity of the system. Since the
maximum pressure of the condenser is 220kPa, it will shut down, hence, more time ,
approximately 10 minutes needed to stabilize the system so that the readings will be more
accurate.
KHAIRUL ANWAR BIN ZAINUDDIN
64816
12. Conclusion
In conclusion, air-conditioning system apply the first law of thermodynamics and
second law of thermodynamics. Evaporator water flow rate is kept constant at 30 g/s. The
system and how it works is also understood by analysing and reasoning the temperature change
of T1 to T8, where the main components (evaporator, condenser, expansion valve) play the
important role in achieving the thermal comfort. Moreover, mass flow rate decrease, the heat
carrying the capacity water decrease, hence, the temperature difference decrease. The effect of
the temperature difference especially in condenser will affect the phase change of the
refrigerant, the pressure and the temperature. Also, the higher the condenser flow rate, the
higher the COP, hence, more energy-efficient the system and lower electricity cost. There are
some data errors in the graphs due to some errors, such as reading errors and so on. Objectives
are achieved.
26
References
(1) Anonymous, (2017). Applications of refrigeration and air conditioning. Retrieved from
https://www.mechlectures.com/applications-refrigeration-air-conditioning/
(2) Mahbub, M. H. (2013, May 19). Scribd. Retrieved from Study of a Refrigeration Unit:
https://www.scribd.com/doc/142332508/Study-of-a-Refrigeration-Unit-R633
(3) Marshall Brain, C. W. (2019). Home & Garden. Retrieved from How Air Conditioners
Work: https://home.howstuffworks.com/ac2.htm
(4) Sharma, B. K. (1997). Thermochemistry. Objective question bank in chemistry. P-457.
Retrieved from https://books.google.com.my/books
(5) Travel Online. (2019). Retrieved from Malaysia Weather and Climate:
https://www.travelonline.com/malaysia/weather.html
(6) Wikipedia. (2019, September 16). Retrieved from Coefficient of performance:
https://en.wikipedia.org/wiki/Coefficient_of_performance
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