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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. This experiment was conducted by Refrigeration Unit R633 using refrigerant Forane-R141b (1,1-dichloro-1-flouroethane) to determine the overall heat transfer coefficient between R141b and water in evaporator and condenser. Overall heat transfer coefficient varied from 724.02 W/m2oC to 1148.35 W/m2oC and 583.15 W/m2oC to 805.50 W/m2oC for evaporator and condenser respectively. Graphs of Saturation pressure vs. saturation temperature, rate of heat transfer vs. condensing temperature, rate of heat transfer vs. compressor pressure ratio for both evaporator and condenser were plotted. Comparing with the reference graphs and possible causes for discrepancies are stated in discussions.
Citation preview
A Report on
STUDY OF A REFRIGERATION UNIT
Bangladesh University of Engineering and Technology
ChE 302
Chemical engineering laboratory - II
Experiment No. 7 Group No. 03 (A2)
Name of the experiment:
STUDY OF A REFRIGERATION UNIT
Submitted by:
Md. Hasib Al Mahbub
Student Id: 0902045
Level: 3; Term: 1
Section: A2
Date of performance: 28/04/2013
Date of submission: 19/05/2013
Partners Student Id. 0902041
0902042
0902043
0902044
Department of Chemical Engineering.
Bangladesh University of engineering and technology, Dhaka.
Page | ii
Summary
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. This experiment was conducted by Refrigeration Unit
R633 using refrigerant Forane-R141b (1,1-dichloro-1-flouroethane) to determine the overall
heat transfer coefficient between R141b and water in evaporator and condenser. Overall heat
transfer coefficient varied from 724.02 W/m2oC to 1148.35 W/m2oC and 583.15 W/m2oC to
805.50 W/m2oC for evaporator and condenser respectively. Graphs of Saturation pressure vs.
saturation temperature, rate of heat transfer vs. condensing temperature, rate of heat transfer
vs. compressor pressure ratio for both evaporator and condenser were plotted. Comparing with
the reference graphs and possible causes for discrepancies are stated in discussions.
Page | iii
Acknowledgement
First of all, I would like to thank our respected teacher, Tania Tabassum Emi, Lecturer,
Department of Chemical Engineering, BUET for the guidance and adjuration. Besides, I would
like to thank the authority of Bangladesh University of Engineering and Technology (BUET)
for providing us with a good facility to complete this report. Also, I would like to take the
opportunity to thank the Department of Chemical Engineering, Bangladesh University of
Engineering and Technology (BUET) for offering this course, Chemical Engineering
Laboratory-II. In addition, I would also like to thank my group partners who helped me in doing
the experiment.
Table of Contents
Page | iv
Title Page No.
Summary ii
Acknowledgement iii
1. Introduction 7
2. Theory 9
2.1 Assumptions for Ideal vapor compression refrigeration cycle 11
2.2 The Steps of Ideal Vapor Compression Cycle 12
2.3 Actual vapor-compression refrigeration cycle 14
2.4 Heat Transfer Coefficient 15
3. Experimental Setup 18
3.1 Apparatus 18
3.2 Chemical Used 18
3.3 Schematic Diagram 19
3.4 R633 Valve Position 20
3.5 Procedure 21
4. Observed Data 22
5. Calculated Data 23
6. Sample Calculation 24
7. Graph 26
7.1 Graph of Saturation pressure vs. Saturation temperature for both
evaporator and condenser
26
7.2 Graph of rate of heat transfer vs. condensing temperature for both
evaporator and condenser
27
7.3 Graph of rate of heat transfer vs. compressor pressure ratio for both
evaporator and condenser
28
8. Result 29
9. Discussion 30
10. Conclusion 35
References 36
Nomenclature 37
Appendices 38
Appendix A: Choice of Refrigerant. 39
Appendix B: Usage and Application of Refrigeration Process. 41
Appendix C: Other Refrigeration Processes (Modification). 43
Page | v
List of Illustrations
List of Figure
No. of Figure Name of Figure Page No.
1 Schematic diagram of a refrigeration unit 9
2 Schematic and T-s diagram for the ideal vapor compressor
refrigerator cycle
11
3 P-h diagram for the ideal vapor compressor refrigerator cycle 13
4 Vapor compressor refrigerator cycle in household refrigerator 13
5 Schematic and T-s diagram of an actual vapor-compression
refrigeration cycle
14
6 Refrigeration cycle demonstration unit R633 16
7 Schematic diagram of a refrigeration unit (R633) 19
8 Different valve position of refrigeration unit R633 20
9 Saturation pressure vs. saturation temperature curve for both
evaporator and condenser
26
10 Rate of heat transfer vs. condensing temperature curve for both
evaporator and condenser
27
11 Rate of heat transfer vs. compressor pressure ratio curve for both
evaporator and condenser
28
12 The theoretical graph of saturation pressure vs. saturation
temperature for both evaporator and condenser
31
13 Theoretical graph of heat transfer vs. condensing temperature for
both evaporator and condenser
32
14 Theoretical graph of heat transfer vs. compressor pressure ratio for
both evaporator and condenser
33
15 A two-stage cascade refrigeration system with the same refrigerant
in both
43
16 A Multistage compression refrigeration systems 44
17 A Multipurpose refrigeration systems 45
18 Vapor-compression refrigeration system is by multistage
compression with regenerative cooling
46
19 Gas Refrigeration Systems 47
20 Absorption Refrigeration Systems 48
21 Thermoelectric Refrigeration Systems 49
Page | vi
List of Tables
No. of Table Name of Table Page No.
1 Observed Data for Vapor Compression of Refrigeration Cycle 22
2 Calculated Data of vapor Compression Refrigeration Cycle 23
3 Tabulated data of the results (rate of heat transfer, compressor
pressure ratio, and overall heat transfer coefficient for evaporator and
condenser)
29
4 List of symbols 37
Page | 7
1. 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.
Including thermodynamics many other phases of engineering are involved in the design,
manufactures, application and operation of refrigeration system. The thermodynamic
properties of the refrigerants must be known before the cycle analysis can be made. Evaporators
and condensers of the system is used for the absorption and rejection of heat respectively
involved the fields of heat transmission. Steady state are involved in the determination of
cooling-load requirements. On the other hand, the design of reciprocating compressor involves
a variety of machine problems. The physical capacity of a compressor or expender will be
determined from thermodynamic factors.
The physical capacity of a compressor or expander can be determined from thermodynamic
factors. The measure of effectiveness of a refrigerator is its coefficient of performance (C.O.P).
It is the expression of the cycle efficiency and is stated as the ratio of the heat absorbed in the
refrigerated space to the heat energy equivalent of the energy supplied to the compressor.
The first known method of artificial refrigeration was demonstrated by William Cullen at the
University of Glasgow in Scotland in 1756. Cullen used a pump to create a partial vacuum over
a container of diethyl ether, which then boiled, absorbing heat from the surrounding air. The
experiment even created a small amount of ice, but had no practical application at that time.
Todays refrigeration process is far more advanced, easy to use and control and more
environment friendly, and thus it has become a very common system adopted at households
and many other places as the first cost and operating costs had also become reasonable.
Page | 8
The application 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 woolen goods storage could beat the moths by using
refrigerated warehouses. So it is important to have a general knowledge on refrigeration which
has prompted to conduct the experiment.
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 this process 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 is created.
Page | 9
2. Theory
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 Refrigeration cycle is a sequence of thermodynamic processes
whereby heat is withdrawn from a cold body and expelled to a hot body, which is a reversed
heat-engine cycle. According to the 2nd law of thermodynamics it required 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 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 the refrigerator (R).
Figure 1. Schematic diagram of a refrigeration unit
Warm
environment
R
QH
QL (Desired output)
Wnet, in (Required input)
Cold
refrigerated
space
Page | 10
In such a case the performance of refrigerators is expressed in terms of the coefficient of
performance (COP), defined as
COP =Desired output
Required input =
Cooling effect
Work input =
QL
Wnet,in ... ... ... ... ... ... ... ... ... (2.1)
Since energy cannot be destroyed, the heat taken in at low temperature plus any other energy
input must be dissipated to the surroundings. 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. 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 component1,
(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.
(3) A condenser where the high pressure vapor condenser, rejecting heat to its
surroundings.
(4) A flow control device which controls the fowl of liquid back to the evaporator and
which brings about the pressure reduction.
The refrigeration cycle is most interesting from the thermodynamic view point. It is one of the
few practical plants which operates on a true thermodynamic cycle and involves8-
(a) Nucleate boiling and film wise condensation.
(b) Steady flow process, i.e. throttling, compression and heat exchange.
(c) Flow control.
Page | 11
(d) The thermodynamic properties, i.e. pressure, specific volume, temperature, specific
enthalpy and entropy of a pure substance at all conditions between sub-cooled liquid
and super-heated vapor.
The refrigeration cycle can be described by and ideal process operated on a Carnot cycle and
then can be converted to the actual cycle or actual changes in entropy and enthalpy during the
process. The Carnot cycle for refrigeration consists of 4 steps as well similar to heat engine.
The phase changes of the refrigerant in the vapor compression cycle are the main key process
of the refrigeration system and they can be represented by the T-S diagram in figure 2.
2.1 Assumptions for Ideal vapor compression refrigeration cycle2
Irreversibility within the evaporator, condenser and compressor are ignored
No frictional pressure drops
Refrigerant flows at constant pressure through the two heat exchangers (evaporator and
condenser)
Stray heat losses to the surroundings are ignored
Compression process is isentropic
Figure 2. Schematic and T-s diagram for the ideal vapor compressor refrigerator cycle.5
QH
Warm
Cold
Evaporator
Condenser
Compressor
QL
Expansion
Valve Win
1
2 3
4
Saturated
liquid
Saturated vapor
QL
QH
Win
T
S
Page | 12
2.2 The Steps of Ideal Vapor Compression Cycle:
The cycle operates on following four process:6
1-2: Isentropic compression
2-3: Constant pressure heat rejection (Condenser)
3-4: Adiabatic expansion in a throttling device
4-1: Constant pressure heat absorption (Evaporator)
I. (1-2) Isentropic compression in a compressor: 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. External work is done on the cycle to initiate the cycle to
flow heat from lower temperature to higher. The saturated vapor outlet from evaporator
goes in the compressor and is compressed to superheated vapor. Here the ideal process
is an isentropic process but in actual case the entropy increases due to increase in
temperature. The compression process is represented by line 1-2 in figure 2.
II. (2-3) Constant pressure heat rejection in a condenser: A condenser where the high
pressure vapor condenses, rejecting heat to its surroundings. This is another isothermal
process in which heat QH is rejected at higher temperature in the condenser. The
superheated vapor from the outlet of the compressor goes in the condenser and cooled
to saturated vapor and then condensed to saturated liquid by rejecting latent heat to the
surrounding at higher temperature (room temperature) The condensation process is a
constant pressure and temperature process which is represented by 2-3 line in the
figure 2.
III. (3-4) Adiabatic expansion in a throttling device: it is an adiabatic process and also
an isenthalpic process of expansion. An expansion device (throttle valve) is used to get
back the refrigerant to its original pressure at the inlet of evaporator. The pressure drop
in this irreversible process results from fluid friction in the valve. At the inlet of the
throttle valve the refrigerant is saturated liquid and due to expansion, it is converted to
a liquid vapor mixture at outlet. This process is represented by line 3-4 in figure 2.
IV. (4-1) Constant pressure heat absorption in an evaporator: It is an isothermal step
in which heat QL is absorbed at the lower temperature in the evaporator. Here the
liquid refrigerant evaporates at constant pressure and temperature absorbing the latent
heat of vaporization. The inlet of the evaporator is a liquid-vapor mixture and absorbing
Page | 13
heat from air of lower temperature (room temperature in this case) it becomes saturated
vapor. The process in evaporator is represented by line4-1 in figure 2.
The P-h diagram in figure 3 is another convenient diagram often used to illustrate the
refrigeration cycle. Where, process 1-2 indicates isentropic compression process, process 2-3
indicates P = constant heat rejection process, process 3-4 indicates expansion under throttling
process, h = constant, process 4-1 stands for P = constant heat addition process.
Figure 3. P-h diagram for the ideal vapor compressor refrigerator cycle.7
The ordinary household refrigerator is a good example of the application of this cycle-
Figure 4. Vapor compressor refrigerator cycle in household refrigerator.3
Evaporator coil
Freezer
compartment
Capillary tube
QH
Condenser coil
Compressor
QL
Kitchen air
25
3
-18
Page | 14
2.3 Actual vapor-compression refrigeration cycle1
An actual vapor-compression refrigeration cycle differs from the ideal one in several ways,
owing mostly to the irreversibilities that occur in various components. Two common sources
of irreversibilities are fluid friction (causes pressure drops) and heat transfer to or from the
surroundings. The T-s diagram of an actual vapor-compression refrigeration cycle is shown in
Figure 5.
Figure 5. Schematic and T-s diagram of an actual vapor-compression refrigeration cycle.
The reason for the deviation is that, there are frictional effects that result in pressure drops as
the refrigerant flows through the condenser, evaporator, and the piping connecting various
components in the actual cycle. The actual compression process (process 1-2) starts in
superheated vapor region, not on the saturated vapor line. The actual compression process is
irreversible (not isentropic) and goes in the direction of increase of entropy (S2>S1). The
isentropic efficiency of the compressor is used to evaluate the performance of the compressor
and define enthalpy at the exit of the actual compressor (point 2). And at the end of the actual
heat rejection process in the condenser (process 2-3) the liquid is sub cooled, not saturated.
Warm
Cold
Evaporator
Condenser
Compressor
QL
Expansion
Valve Win
1
2 5
7
3 4
6
8
1
2 3
2`
4
5 6 7 8
T
s
Page | 15
2.4 Heat Transfer Coefficient
Heat transfer coefficient is defined as the amount of heat which passes through a unit area of a
medium or system in a unit time when the temperature difference between the boundaries of
the system is 1 degree.2 The heat transfer coefficient, in thermodynamics and in mechanical
and chemical engineering, is used in calculating the heat transfer, typically by convection or
phase transition between a fluid and a solid:
Where
Q = heat flow in input or lost heat flow, J/s = W
h = heat transfer coefficient, W/ (m2K)
A = heat transfer surface area, m2
T= difference in temperature between the solid surface and surrounding fluid area
From the above equation, the heat transfer coefficient is the proportionality coefficient between
the heat flux, that is heat flow per unit area, q/A, and the thermodynamic driving force for the
flow of heat (i.e., the temperature difference, T).
The heat transfer coefficient has SI units in watts per square meter kelvin: W/ (m2K).
The overall heat transfer coefficient (U) is a measure of the overall ability of a series of
conductive and convective barriers to transfer heat1. It is commonly applied to the calculation
of heat transfer in heat exchangers, but can be applied equally well to other problems.
For the case of a heat exchanger, U can be used to determine the total heat transfer between the
two streams in the heat exchanger by the following relationship:
Where
Q = heat transfer rate, W
U = overall heat transfer coefficient, W/ (mK)
A = heat transfer surface area, m2
TLMTD = log mean temperature difference, K
U=
Q
ATLMTD
... ... ... ... ... ... ... ... ... (2.2)
... ... ... ... ... ... ... ... ... (2.3)
Page | 16
With the use of refrigeration cycle demonstration unit R633 (Figure 6) in laboratory, following
steps leads to the calculation of overall heat transfer coefficient (U).
Figure 6. Refrigeration cycle demonstration unit R633
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= meCp(t1-t2)
Rate of heat transfer for Condenser, Qc= mcCp(t3-t4)
Where
Cp = Specific Heat of Water, (KJ/Kg .K)
me = Evaporator Water Flow rate
mc = Condenser Water Flow rate
t1 = Evaporator Water Inlet Temperature, ()
t2 =Evaporator Water Outlet Temperature, ()
t3 =Condenser Water Outlet Temperature, ()
t4 =Condenser Water Inlet Temperature, ()
Finally,
Overall Heat Transfer Coefficient,
U=
Q
ATLMTD
Page | 17
Where each term Q, A and TLMTD refer to the corresponding value for condenser and
evaporator
TLMTD =
Where
Tin= temperature difference of water inlet and supplied refrigerant.
Tout= temperature difference of water outlet and supplied refrigerant.
Tin
Tout
Tin-Tout
ln ( ) ... .... ... ... ... ... ... ... ... ... (2.4)
Page | 18
3. Experimental Setup
3.1 Apparatus
Compressor
Temperature indicator
Condenser rotameter
Evaporator rotameter
Condenser
Evaporator
Condenser pressure gauge
Evaporator pressure gauge
Condenser inlet thermometer
Condenser outlet thermometer
Evaporator inlet thermometer
Evaporator outlet thermometer
Condenser thermometer
Evaporator thermometer
Throttle valve
Compressor discharge thermometer
Control valve
Switcher
Capillary tube
Water reservoir
Pump
3.2 Chemical Used
R141b (1,1-dichloro-1-fluoroethane)
Water
Fig
ure
7.
Sch
em
ati
c d
iagra
m o
f a r
efri
ger
ati
on
un
it (
R6
33)
Outl
et C
onden
ser
Ther
mom
eter
Conden
ser
Pre
ssure
Gau
ge
Conden
ser
Ther
mom
eter
Inle
t C
onden
ser
Ther
mom
eter
Conden
ser
Rota
met
er
Tem
per
ature
Indic
ator
Inle
t E
vap
ora
tor
Ther
mom
eter
Evap
ora
tor
Pre
ssure
Gau
ge
Evap
ora
tor
Th
erm
om
eter
Outl
et E
vap
ora
tor
Ther
mom
eter
Evap
ora
tor
Rota
met
er
Evap
ora
tor
Conden
ser
Thro
ttle
Val
ve
Wat
er O
utl
et
Com
pre
ssor
Wat
er R
eser
voir
Pum
p
3.3 Schematic diagram
3.4 R633 Valve Position
Normal Operation
Refrigerant Pump Down
Oil Return
Shutdown
Figure 8. Different valve position of refrigeration unit R633
Page | 21
3.5 PROCEDURE
The main components of the refrigeration unit were identified.
The piping and control system were studied.
The cooling water supply and mains supply to the unit were turned on.
Water supply to the unit was turned on and the evaporator water flow rate was adjusted
to 10 g/s and condenser water flow rate was adjusted to 50 g/s using control valve.
When the main switch was turned on, then the compressor was started and the two
internal lamps were lighted.
The evaporator pressure and the compressor pressure were set approximately at -75
KN/m2 and 120 KN/m2.
The unit was allowed to run approximately 15 minutes in order to reach suitable
temperature and pressure.
The temperatures (t1, t2, t3, t4, t5, t6, t7, t8), pressure pe and pc, water flow rate me and mc
were recorded.
Similarly steps h - i were repeated after reducing condenser water flow rate to 40 g/s,
30 g/s, 20 g/s, 10 g/s.
Page | 22
4. Observed Data
Water Coil Surface Area of Condenser, Ac= 0.032 m2
Water Coil Surface Area of Evaporator, Ae=0.032 m2
Specific Heat of Water, Cp= 4.18 KJ/Kg .K
Refrigerant used= R141b (1, 1- dichloro-1-fluroethane) of approximately 800 cm3
Normal Boiling Point= 32
Local Atmospheric Pressure, P= 101.325 KN/m2
Table 1. Observed Data for Vapor Compression of Refrigeration Cycle.
Number of observation 1 2 3 4 5
Evaporation Gauge pressure, pe (KN/m2) -70 -68 -70 -69 -68
Absolute Evaporator pressure, Pe (KN/m2) 31.33 33.33 31.33 32.33 33.33
Evaporator temperature, T5 () 7 8 8 6 7
Evaporator water flow rate, e (g/s) 4 7 4 4 4
Evaporator Water Inlet Temperature, T1 () 15 14 17 18 19
Evaporator Water Outlet Temperature, T2
() 9 10 9 9 10
Condensed Liquid Temperature, T8 () 24.10 25.40 26.90 28.30 31.1
Condenser Gauge Pressure, pc (KN/m2) 50 54 59 65 78
Absolute Condenser Pressure, Pc (KN/m2) 151.33 155.33 160.33 166.33 179.33
Compressor Discharge Temperature, T7 () 43 44 49 52 53
Condenser Temperature, T6 () 23 24 26 27 30
Condenser Water Flow Rate, c (g/s) 50 40 30 20 10
Condenser Water Inlet Temperature, T4 () 12 13.5 15.5 17 18
Condenser Water Outlet Temperature, T3 () 13 15 17 19 23
Page | 23
5. Calculated Data
Table 2. Calculated Data of vapor Compression Refrigeration Cycle.
Number of Observation 1 2 3 4 5
Saturation Pressure of Evaporator,
Pe (KN/m2) 31.33 33.33 31.33 32.33 33.33
Saturation Pressure of Condenser,
Pc (KN/m2) 151.33 155.33 160.33 166.33 179.33
Rate of Heat Transfer for
Evaporator, Qe (W)=meCp(t1-t2) 100.32 117.04 133.76 150.48 150.48
Rate of Heat Transfer for Condenser,
Qc (W) )=mCCp(t3-t4) 209 250.80 188.1 167.20 209
Compressor Pressure Ratio,
4.83 4.66 5.12 5.14 5.38
Temperature difference for
evaporator inlet, Tin,e= t1-t5 8 6 9 12 12
Temperature difference for
evaporator outlet, Tout,e= t2-t5 2 2 1 3 3
TLMTD(Evaporator)()=,,
(,
,)
4.33 3.64 3.64 6.49 6.49
Temperature difference for
condenser inlet, Tin,c= t6-t4 11 10.5 10.5 10 12
Temperature difference for
condenser outlet, Tout,c=t6-t3 10 9 9 8 7
TLMTD (Condenser)()=,,
(,
,)
10.49 9.73 9.73 8.96 9.28
Overall Heat Transfer Coefficient
(Evaporator), Ue (W/m2)=
724.02 1004.81 1148.35 724.58 724.58
Overall Heat Transfer Coefficient
(Condenser), Uc (W/m2)=
622.62 805.50 604.12 583.15 703.80
Page | 24
6. Sample Calculation
Sample calculation for observation- 5
Atmospheric pressure = 101.325 KN/m2
Water coil surface area in Evaporator, Ae = 0.032 m2
Water coil surface area in Condenser, Ac = 0.032 m2
Evaporator gauge pressure, pe = -68 KN/m2
Evaporator absolute pressure, Pe = (-68+101.325) KN/m2
= 33.33 KN/m2
Condenser gauge pressure, pc = 78 KN/m2
Condenser absolute Pressure, Pc = (78+101.325) KN/m2
= 179.325 KN/m2
Compressor Pressure Ratio,
=
179.325
33.33 = 5.38
Evaporator water flow rate, e = 4 g/s
Evaporator water inlet temperature, t1 = 19
Evaporator water outlet temperature, t2 =10
Rate of heat transfer to water in evaporator, Qe = eCp(t1-t2)
= 44.18(19-10) W
= 150.48 W
Condenser water flow rate, c = 10 g/s
Condenser water inlet temperature, t4 = 18
Condenser water outlet temperature, t3 = 23
Rate of heat transfer to water in Condenser, Qc = cCp(t3-t4)
= 104.18(23-18) W
= 209 W
Page | 25
For Evaporator
Evaporator temperature, t5 = 7
Tin = ( t1- t5 )
= (19-7)
=12
Tout = (t2- t5)
= (10-7)
= 3
TLMTD =
ln(
)
= 123
ln(12
3)
= 6.49
For evaporator overall heat transfer coefficient, Ue =
= 150.48
0.0326.49 W/m2
= 724.58 W/m2
For Condenser
Condenser temperature, t6 = 30
Tin = ( t6- t4 )
= (30-18)
= 12
Tout = ( t6- t3 )
= (30-23)
= 7
TLMTD =
ln(
)
= 127
ln(12
7)
= 9.28
For condenser overall heat transfer coefficient, Ue =
= 209
0.0329.28W/m2.0 C
= 703.79 W/m2
703.8 W/m2
Page | 26
7. Graphs
7.1 Graph of Saturation pressure vs. Saturation temperature for both evaporator and condenser
Figure 9. Saturation pressure vs. saturation temperature curve for both evaporator and
condenser
y = 32.33
R = 0
y = 3.9667x + 59.397
R = 0.9859
0
20
40
60
80
100
120
140
160
180
200
0 5 10 15 20 25 30 35
1 s
mal
l sq
uar
e =
5 K
Pa
Sat
ura
tion P
ress
ure
, (
KP
a )
Saturation Temperature, ( C ) 1 small square = 1C
Evaporator
Condenser
Page | 27
7.2 Graph of rate of heat transfer vs. condensing temperature for both evaporator and condenser
Figure 10. Rate of heat transfer vs. condensing temperature curve for both evaporator
and condenser
y = 7.3825x - 70.093
R = 0.8415
y = 4.0215x + 53.305
R = 0.9914
90
100
110
120
130
140
150
160
170
180
190
22 23 24 25 26 27 28 29 30 31 32
Rat
e of
hea
t tr
ansf
er f
or
both
evap
ora
tor
and
co
nd
ense
r(W
)
(1 s
quar
e unit
= 2
W)
Condensing temperature(C) (1 square unit = 0.4 C )
Evaporator
Condenser
Page | 28
7.3 Graph of rate of heat transfer vs. compressor pressure ratio for both evaporator and condenser
Figure 11. Rate of heat transfer vs. compressor pressure ratio curve for both evaporator and
condenser
y = 64.155x - 192.03
R = 0.6918
y = -68.943x + 551.33
R = 0.3951
80
100
120
140
160
180
200
220
240
260
4.6 4.7 4.8 4.9 5 5.1 5.2 5.3 5.4 5.5
Rat
e of
hea
t tr
anfe
r fo
r both
evap
ora
tor
and
co
nd
ense
r(W
)
1 s
quar
e um
it =
10 W
Compressor pressure ratio
1 square unit = 0.04
Evaporator
Condensor
Page | 29
8. Result
Results obtained in the experiment are shown below:
Table 3. Tabulated data of the results (rate of heat transfer, compressor pressure ratio,
and overall heat transfer coefficient for evaporator and condenser).
Observation
Number
Rate of Heat
Transfer to
Water in
Evaporator,
Qe (W)
Rate of Heat
Transfer to
Water in
Condenser,
Qc (W)
Overall Heat
Transfer
Coefficient,
Ue(W/m2.)
Over all Heat
Transfer
Coefficient,
Uc(W/m2.)
Compressor
Pressure
Ratio,
( Pc / Pe)
1 100.32 209 724.02 622.62 4.83
2 117.04 250.8 1004.81 805.50 4.66
3 133.76 188.1 1148.35 604.12 5.12
4 150.48 167.2 724.35 583.15 5.14
5 150.48 209 724.58 703.80 5.38
Page | 30
9. Discussion
From the calculated data the required graphs, i.e.
I. Saturation pressure vs. Saturation temperature curve,
II. Rate of heat transfer vs. Condensing temperature curve and
III. Rate of heat transfer vs. Compressor pressure ratio curve for both evaporator and
condenser
are shown above. Though the curves shows the general characteristics somewhat accurately,
these experimental curves show some deviations from the theoretical curves. The major causes
for the deviation of the experimental graphs4 from the theoretical graphs are discussed below.
i) Saturation pressure vs. Saturation temperature curve
The relationship between saturation pressure and temperature was observed in both evaporator
and condenser. However variation of evaporating temperature was small for all but extreme
changes in cooling water flow.
As the condenser contains refrigerants in all stages from superheated vapor through to sub
cooled liquid the thermometer pocket t6 only records temperature close to saturation when the
pocket is showing signs of condensed liquid. Therefore it is recommended that the pressure
temperature relationship in the condenser is investigated as the condenser pressure increases.
In case of investigating pressure temperature relationship by reducing the condenser pressure
then the t6 thermometer pocket will be at a temperature that is higher than the surrounding
vapor due to its thermal inertia. Therefore no vapor will condense on the pocket and an
incorrect temperature will be measured.
The theoretical graph of saturation pressure vs. saturation temperature for both evaporator and
condenser for R141b is shown below. Here the standard pressure gauge accuracy of 1% of
gauge full scale has been shown as dotted lines about a mean. We can see from the graph that,
the curves of condenser and evaporator are so close and the trend line seems to be a single one.
But form the experimental graph (figure. 12), it can be seen that they are far apart due to the
discrepancies like reading errors, absolute accuracy of temperatures etc.
Page | 31
Figure 12. The theoretical graph of saturation pressure vs. saturation temperature for
both evaporator and condenser4
ii) Rate of heat transfer vs. Condensing temperature curve
The effect of evaporating temperature on the refrigerator rate could be investigated, but due to
the limited effect on evaporating temperature it is more graphic to investigate condensing
temperature. The effect of increasing the condensing temperature on many refrigeration system
and heat pumps is a reduction in the heat discharge from the condenser and in many cases a
smaller reduction in the refrigerating effect at the evaporator.
The following theoretical graph shows that the heat transfer at the condenser decreases as the
condensing temperature increases. 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 increases
with condensing temperature. Which may be due to the discrepancies like pressure variation,
reading error etc.
Page | 32
Figure 13. Theoretical graph of heat transfer vs. condensing temperature for both
evaporator and condenser4
iii) Rate of heat transfer vs. Compressor pressure ratio curve 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. From the
graph it can be seen that the evaporator curve is parallel to x-axis and condenser curve makes
a negative slope. form the experimental graph it can be seen that condenser curve is same as
the theoretical one but the evaporator curve is not parallel to x- axis rather it is positively sloped
and. Here heat transfer rate increases for evaporator and decreases for condenser with
compressor pressure ratio.
Page | 33
Figure 14. Theoretical graph of heat transfer vs. compressor pressure ratio for both
evaporator and condenser4
The deviation of experimental curves and some observations of data for which the rate of heat
transfer was not identical with other calculated value which might cause from the following
discrepancies.
The experiment and the calculations was done considering the system to be operated
on ideal Carnot cycle. But in actual case the conditions vary from the ideal one. The
actual compression process starts in superheated vapor region, not on the saturated
vapor line. The actual compression process is irreversible (not isentropic) and goes in
the direction of increase of entropy. And at the end of the actual heat rejection process
in the condenser the liquid is sub cooled, not saturated.
Presence of air in refrigeration unit causes the compressor delivery pressure to rise,
reducing the coefficient of performance. This increase of pressure is generally due to -
(i) the total pressure in the condenser is approximately equal to the sum of the
refrigerant saturation pressure and the pressure of the air present. And (ii) the air tends
to be swept towards the heat transfer surfaces, forming an insulated layer which reduces
the heat transfer coefficient
Page | 34
Because of fluid friction small pressure drops occur and some error is found in
calculation. A small heat exchange also occurs with the surroundings of the system as
the system cant be insulated in such a way so that no heat is exchanged with the
surroundings.
Another cause for the deviation of the vapor compression cycle applied for actual
refrigeration cycles from the Carnot cycle is due to the irreversibility in expansion in
the throttle valve and also in the compression process. Error is found therefor in the
calculation and experimental graphs deviate from the theoretical one.
Pressure of condenser was increasing very rapidly and was not stable enough to get
accurate values of temperature for corresponding pressure of condenser.
Mass flow rate had to be controlled by observing the flow meter as the flow rate was
not constant in any certain observation. It was fluctuating a little bit.
Page | 35
10. Conclusion Modern life has reached in such position that temperature control is unavoidable in various
cases which cant be imagined without refrigeration. So it is important to have an overall
knowledge about refrigeration system, its different parts and operating modes. Selection of
refrigerator for any purpose depends on refrigerant types, efficiency required, system
characteristics and environmental feature. In this experiment all the separate parts of the
refrigeration unit, their structure and mechanisms had been well observed and studied. The
objective of this experiment have been completely achieved as required and at the same time,
all the parameters required to be solved have been calculated and solved accordingly. In
addition, all of the experiments have eventually being done according to the procedures given
systematically and appropriately. There were many discrepancies while performing the
experiment due to which experimental data deviates from the theoretical one. But still it is very
helpful to acquire a general idea on refrigeration.
Page | 36
References
1. Abbot, M. M., Van Ness, and Smith, J. M., (2001), Introduction to CHEMICAL
ENGINEERING THERMODYNAMICS, 6th edition, Tata McGraw-Hill Publishing
Company Limited, pp. 309-322.
2. Cengel, Y. A. and Boles, M. A., (2006), THERMODYNAMICS An Engineering
Approach, 5th edition, Tata McGraw-Hill Publishing Company Limited, pp. 607-637.
3. Perry, R. H. and Green, D. W., (1997) Perrys Chemical Engineers Handbook, 7th
edition, McGraw-Hill, New York, pp. 11/76-11/80.
4. Experimental Operating and Maintenance Manual Refrigeration cycle
demonstration unit. P. A. Hilton Ltd. SI no 3080 Feb. 96, pp. 4, 27-29, 36-38, 40-42.
5. Richard C. Jordan & Gayle B. Priester Refrigeration and Air Conditioning, Chapter-
2, pp. 16-17,423
6. C P Arora, Refrigeration and Air conditioning, 2nd edition, Tata McGraw-Hill
Publishing Company Limited, New Delhi, 2000, pp. 113,119.
7. Andrew D. Althouse, Carl H. Turnquist, Alfred F. Bracciano, Modern Refrigeration
And Air Conditioning, The Goodheart-Wilcox Company, Inc.1968, pp. 319-324.
8. Stoecker W. S., (1998), Industrial Refrigeration Handbook, McGraw-Hill, New
York, pp. 115-120.
Page | 37
Nomenclature
List of symbols used throughout the report are given below:
Table 4. List of symbols
Symbol Significance Unit (SI)
COP Coefficient of performance Unitless
h Enthalpy J
I Current Amp
P Pressure KPa
Q Supplied heat Watt
Qc Heat removed from cold reservoir Watt
QH Heat supplied to hot reservoir Watt
QL Amount of heat of low temperature source Watt
S Entropy KJ K-1
Tm Logarithmic Mean Temperature Difference
(LMDT) C
Tcold Temperature of cold reservoir C
Thot Temperature of hot reservoir C
TH Temperature of condenser C
TL Temperature of evaporator C
U Overall Heat Transfer Coefficient W/m2C
W Work J
Page | 38
Appendices
A. Choice of Refrigerant.
B. Usage and Application of Refrigeration Process.
C. Other Refrigeration Processes (Modification).
Page | 39
Appendix A: Choice of Refrigerant
Factors which affect the efficiency of a refrigeration system are:
the refrigerant performance
heat exchangers
evaporating temperature
condenser temperature
compressor efficiency
pipe sizing
The coefficient of performance of a carnot refrigerator is independent of the refrigerant.
However, the irreversibilities inherent in the vapor compression cycle cause the COP of
practical refrigerators to depend to some extent on the refrigerant. The following characteristics
of a refrigerant are important in case of selection:
Toxicity
Flammability
Chemical stability
Cost
Corrosion properties
Vapor pressure in relation to temperature
Thermal factors
Ozone depletion
Global warming impact
If the refrigerant is toxic or flammable it will be very hazardous and injurious to health if even
a small leakage of the system takes place which is not an abnormal phenomenon. If it is
flammable then explosion can take place easily in case of leakage or if pressure is built up
inside somehow.
Cost is also an important factor for smaller units costly refrigerant can be used but in industrial
purpose optimization of cost is required.
If the refrigerant is corrosive then the whole unit would be affected and would sustain smaller
period of time than expected.
Page | 40
The vapor pressure of the refrigerant at the evaporator temperature should be greater than
atmospheric pressure so that air cannot leak into the refrigeration system. On the other hand,
the vapor pressure of the refrigerant at condenser temperature should not be unduly high,
because of the initial cost and operating expense of high pressure equipment. These two
requirements limit the choice of refrigerant to relatively few fluids. The final selection then
depends on the other characteristics.
Thermal Factors
The heat of vaporization of the refrigerant should be high. The higher hfg, the greater
the refrigerating effect per kg of fluid circulated
The specific heat of the refrigerant should be low. The lower the specific heat, the less
heat it will pick up for a given change in temperature during the throttling or in flow
through the piping, and consequently the greater the refrigerating effect per kg of
refrigerant
The specific volume of the refrigerant should be low to minimize the work required
per kg of refrigerant circulated
Since evaporation and condenser temperatures are fixed by the temperatures of the
surroundings- selection is based on operating pressures in the evaporator and the
condenser
Ozone Depletion Potential
chlorinated and brominated refrigerants
acts as a catalyst to destroy ozone molecules
reduces the natural shielding effect from incoming ultra violet B radiation
Global Warming Potential
gases that absorb infrared energy
gases with a high number of carbon-fluorine bonds
generally have a long atmospheric lifetime
Page | 41
Appendix B: Usage and Application of Refrigeration Process.
Refrigeration can serve us from the cradle to the grave. For some, the benefits starts at birth in
the air condition delivery room and for a few in the modern incubator and nursery for premature
babies. Applications are then encountered and appreciated though the often indirectly
throughout life and for some, refrigeration is even applied after death in cooling the slab vault
at the city morgue. The applications may be classified into one of the following five general
groups. They are as follows:
1. Domestic Refrigeration
2. Commercial Refrigeration
3. Industrial Refrigeration
4. Marine and Transportation Refrigeration
5. Air-Conditioning Refrigeration
1. Domestic Refrigeration: Domestic refrigeration is rather limited in scope, being
concerned primarily with household refrigerator and home freezers. However, because the
number of units in service is quite large, domestic refrigeration represents a significant
portion of the refrigeration industry. Domestic units are usually small in size having
horsepower ratings of between 1/20 and 1/2 horsepower and were of the hermetically sealed
type. Since these applications are familiar to everyone.
2. Commercial Refrigeration: Commercial refrigeration is concerned with the designing,
installation and maintenance of refrigerated fixtures of the type used by retail stores,
restaurants, hotels and institutions for the storing, displaying, processing and dispensing of
perishable commodities of all types.
3. Industrials Refrigeration: Industrial application is larger in size than commercial
application. Typical industrial application is ice plants, large food packing plants that were
fish, meat, poultry, frozen foods etc.
4. Marine and Transportation Refrigeration: Marine refrigeration, of course, referrers to
refrigeration aboard marine vessels and included, for example, refrigeration for boats and
for vessels transporting perishable cargo as well as refrigeration for the ships stores on
Page | 42
vessels of all kinds. Transportation refrigeration is concerned with refrigeration equipment
as it is applied to trucks, both long distance transports and local delivery and to refrigerated
railway cars.
5. Air-Conditioning Refrigeration: Air conditioning applications are of two types, either
comfort or industrial, according to the purpose. Any air-conditioning, which has as its
primary function the conditioning of air for human comfort is called comfort air-
conditioning. Typical installations of comfort air conditioning are in homes, schools,
offices, churches, hotels, retail stores, public buildings, factories, automobiles, busses,
trains, planes, ships etc. The applications of industrial air conditioning are almost without
limit both in number and in variety. Generally speaking, the functions of industrial air
conditioning systems are to
Control the moisture content of hydroscopic materials
The govern rate of chemical and bio-chemical reactions
Limit the variations in the size of precision manufactured articles because of thermal
expansion and construction
Provide clean, filtered air, which was often essential to trouble free operation and to the
production of quality products.
In spite of some specific classifications would include as follows:
Oil refining and synthetic rubber manufacturing
Creation of artificial atmospheric conditions
Medical and Surgical aids
Heat Pump
Ice making
Page | 43
Appendix C: Other Refrigeration Processes (Modification)
1. Cascade refrigeration systems
Some industrial applications require moderately low temperatures, and the temperature range
they involve may be too large for a single vapor compression refrigeration cycle to be practical.
A large temperature range also means a large pressure range in the cycle and a poor
performance for a reciprocating compressor. One way of dealing with such situations is to
perform the refrigeration process in stages, that is, to have two or more refrigeration cycles that
operate in series. Such refrigeration cycles are called cascade refrigeration cycles.
Figure 15. A two-stage cascade refrigeration system with the same refrigerant in both
Refrigerants with more desirable characteristics can be used in each cycle. In this case, there
would be a separate saturation dome for each fluid, and the T-s diagram for one of the cycles
would be different. Also, in actual cascade refrigeration systems, the two cycles would overlap
somewhat since a temperature difference between the two fluids is needed for any heat transfer
to take place. It is evident from the T-s diagram in Fig.16 that the compressor work decreases
and the amount of heat absorbed from the refrigerated space increases as a result of cascading.
Page | 44
Therefore, cascading improves the COP of a refrigeration system. Some refrigeration systems
use three or four stages of cascading.
The characteristics of a cascade refrigeration system are following:
combined cycle arrangements
two or more vapor compression refrigeration cycles are combined
used where a very wide range of temperature between TL and TH is required
the condenser for the low temperature refrigerator is used as the evaporator for the high
temperature refrigerator
2. Multistage compression refrigeration systems
In case of using same refrigerant, then we have the option to mix the refrigerant of each system
with each other to attain better heat transfer properties. These type of systems are called
multistage compression refrigeration systems. In order to understand the behavior, we will
consider 2 stage refrigeration system.
Figure 16. A Multistage compression refrigeration systems
Page | 45
By looking at the T-s diagram of the system, we can clearly see that the refrigerant expands in
the first expansion valve to the flash chamber pressure, the same pressure which the interstage
compressor have. At the time of doing compression, part of the liquid gets evaporated
represented as state 3 and mixed with superheated vapors come from low pressure
compressor at state 2. When the mixture is prepared in the chamber then it will enter in the
high pressure compressor. The saturated liquid state then expands in the second expansion
valve where it further picks up the heat from refrigerated space.
Because of using flash chamber which further do direct mixing process of the refrigerant, we
can relate it with the regeneration process where we extract heat from one process of the cycle
and then delivers the same amount of heat to the other process in the same cycle.
3. Multipurpose refrigeration systems
There are many practical applications in which we require refrigerating effect at more than one
temperature. So to attain this phenomenon either we can do throttling process by installing the
separate throttling valve or to install compressor for each evaporator having unique
temperatures. But the installation of either systems will be too bulky and uneconomical,
therefore we need to make this system much more efficient and economical. For this reason,
we redirect the route of all exit streams from each evaporator to the single compressor.
In order to understand the behavior, we consider ordinary refrigerator freezer unit usually
installed in the houses. Normally the temperature of the freezer compartment is 18C but to
do heat transfer, the refrigerant temperature should be 25C.
Figure 17. A Multipurpose refrigeration systems
Page | 46
Now if we have single expansion valve and evaporator then the same refrigerant will pass
through both freezer compartment and then to the evaporator coils where ice formation will
start. But to reduce the problem of evaporator coil freezing, we can throttle it to the minimum
pressure so that we can use it in the freezer compartment. From where it is then compressed by
single compressor to the condenser pressure.
4. Liquefaction of gases
Another way of improving the performance of a vapor-compression refrigeration system is by
using multistage compression with regenerative cooling. The vapor-compression refrigeration
cycle can also be used to liquefy gases after some modifications.
Figure 18. Vapor-compression refrigeration system is by multistage compression with
regenerative cooling.
Page | 47
5. Gas Refrigeration Systems
The power cycles can be used as refrigeration cycles by simply reversing them. Of these, the
reversed Brayton cycle, which is also known as the gas refrigeration cycle, is used to cool
aircraft and to obtain very low (cryogenic) temperatures after it is modified with regeneration.
The work output of the turbine can be used to reduce the work input requirements to the
compressor. Thus, the COP of a gas refrigeration cycle is
Figure 19. Gas Refrigeration Systems
6. Absorption Refrigeration Systems
Another form of refrigeration that becomes economically attractive when there is a source of
inexpensive heat energy at a temperature of 100 to 200 is absorption refrigeration, where the
refrigerant is absorbed by a transport medium and compressed in liquid form. The most widely
used absorption refrigeration system is the ammonia-water system, where ammonia serves as
the refrigerant and water as the transport medium. The work input to the pump is usually very
small, and the COP of absorption refrigeration systems is defined as
Page | 48
Figure 20. Absorption Refrigeration Systems
7. Thermoelectric Refrigeration Systems
A refrigeration effect can also be achieved without using any moving parts by simply passing
a small current through a closed circuit made up of two dissimilar materials. This effect is
called the Peltier effect, and a refrigerator that works on this principle is called a thermoelectric
refrigerator.
The thermoelectric device, like the conventional thermocouple, uses two dissimilar materials.
There are two junctions between these two materials in a thermoelectric refrigerator. One is
located in the refrigerated space and the other in ambient surroundings. When a potential
difference is applied, as indicated, the temperature of the junction located in the refrigerated
Page | 49
space will decrease and the temperature of the other junction will increase. Under steady-state
operating conditions, heat will be transferred from the refrigerated space to the cold junction.
The other junction will be at a temperature above the ambient, and heat will be transferred from
the junction to the surroundings. A thermoelectric device can also be used to generate power
by replacing the refrigerated space with a body that is at a temperature above the ambient.
Figure 21. Thermoelectric Refrigeration Systems
Marking scheme: Formal Report on Study of a Refrigeration Unit
Name: Md. Hasib Al Mahbub
Student number: 0902045
Section and marks allocated Marks
Summary (10)
Introduction (5)
Theory (10)
Experimental setup (10)
Observed data (5)
Calculated data (5)
Sample calculation (5)
Graphs (15)
Results and Discussions (10)
Conclusion (5)
References and Nomenclature (10)
Overall (10)
Total (100)
ChE 302 Chemical Engineering Laboratory II
PERFORMANCE EVALUATION SHEET
Experiment No : 7 Group No : 03 (A2)
Name of Experiment : STUDY OF A REFRIGERATION UNIT
Following is the list of contributions each of the members of the group conducted while
performing the experiment:
Student
Number
Contribution
Experiment Report
0902041 Has drawn the experimental
setup and observed all data
Has drawn Graphs in Microsoft
Excel
0902042 Has done Calculation Has done sample calculation in
Microsoft word
0902043 Has observed all temperatures
of evaporator and condenser
Has done all calculations in
Microsoft Excel
0902044 Has observed all other
temperature of system, water
flow rate, pressure
Has tabulated all observed and
calculated data in Microsoft word
0902045 Has collected all observed data
in tabulated form
Has drawn graphs and all other
necessary work necessary for
creating a formal report
I hereby announce that every statement I provided above is true and I will be responsible for
any misinformation.
Sign above the line
Name (Group Leader): Md. Hasib Al Mahbub
Student Number: 0902045
CoverTopSummarypage 1-12Figure 1Figure 2page 15-43Marking schemeEvolution