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International Journal of Emerging Technology and Advanced Engineering

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Energy and Exergy Analysis of Vapour Compression

Refrigeration System with R12, R22, R134a Md. Nawaz Khan

1, Md. Mamoon Khan

2, Mohd. Ashar

3, Aasim Zafar Khan

4

1Assistant Professor,

3,4Lecturer, Department of Mechanical Engineering, Integral University, Lucknow, Uttar Pradesh,

India 2Faculty, Department of Mechanical Engineering, Rohilkhand University, Bareilly, Uttar Pradesh, India

Abstract- This paper provides a detailed exergy analysis

for theoretical vapour compression refrigeration cycle using

R12, R22 and R134A. The equations of exergetic efficiency

and exergy destruction for the main system components

such as compressor, condenser expansion device and

evaporator are developed. The relations for total exergy

destruction in the system, the overall exegetic efficiency of

the system and Exergy Destruction Ratio (EDR) related to

exergetic efficiency are obtained. Also, an expression for

Coefficient of Performance (COP) of refrigeration cycle is

developed. The investigations shows that various results are

obtained for the effect of evaporating temperatures on

COP, exergetic efficiency and EDR of theoretical vapour

compression refrigeration cycle.

Keywords- Exergy, Subcooling, R12, R22 and R134A

I. INTRODUCTION

Energy consumption in buildings and in industries has

become an important aspect on a global scale. There in

energy efficiency is a prime mover in reducing global

warming emissions. The rapid escalation in energy costs,

the issues of security of supply, the emission of polluting

substances as well as global climate change, have all

made refrigerating methods in their current forms

unsustainable at present and in the future. Therefore to

overcome these problems, alternative solutions must be

studied which focus on the reduction of energy

consumption and the improvement of heating

performance while reducing adverse effects on the

environment. Various researches have suggested different

HC, HFC and HCFC blends as potential substitutes for

CFCs and compared the performance of these substitutes

either theoretically or experimentally.

The growing awareness of the need to sustain the

ecology of the planet has resulted in the phase out of the

harmful refrigerants containing chlorine atoms, such as

chlorofluorocarbons (CFCs) and hydro-

chlorofluorocarbons (HCFCs). Although a replacement

for CFCs has been found, the search for good alternatives

for HCFCs especially R-22 is still on.

II. LITERATURE REVIEW

Lovelin Jerald et al. (2014) in his study investigate the

performance analysis of vapour compression

refrigeration system with zeotropic refrigerant R404a.

Mohammad Nawaz khan et al. (2014) in his paper

explained the comparative performance analysis of four

different configuration of a vapour compression

refrigeration system with four different refrigerants R12,

R134a, R407 and R717. The four configurations are

Simple Vapour Compression system , Multiple

Compression System with flash chamber, Multiple

compression system with water intercooler and liquid

subcooler and Multiple compression system with Flash

intercooling and multiple expansion valve, The results

showed that the refrigerant R717 have highest COP for

Simple Vapour Compression system , Multiple

Compression System with flash chamber and MCS with

Flash intercooling and multiple expansion valve followed

by the R12 in Simple VCS, R134a in Multiple

Compression System with flash chamber and R407 in

Multiple compression system with Flash intercooling and

multiple expansion valve but in Multiple compression

system with water intercooler and liquid subcooler the

highest COP is of R12 followed by R717. Jyoti soni et al. (2013) in his paper presents the

simulation result of vapour compression refrigeration

system with R404A, 407C, 410A as refrigerants and

conclude that the COP and exergetic efficiency of R407C

are better than that of R404A and R410A. The EDR of

R410A is higher than that of R407C and R404A.

Bilal et al. (2011) investigated performance

degradation due to fouling in a vapour compression cycle

for various applications. For the analysis consider the two

sets of refrigerants depending upon the assumption and

their some properties. Considering the first set of

refrigerants R134a, R410A and R407C while second set

include the refrigerants of R717, R404A and R290.



211

Venkataramanamurthy et al. (2010) conducted an

experimental test for the analysis the comparisons of

energy, exergy flow and second law efficiency of R22

and its substitutes R-436b in vapour compression

refrigeration system. The investigations present the

effects of the evaporating temperatures on the exergy

flow losses and second law efficiency and coefficient of

performance of a vapour compression refrigeration cycle.

Comakli et al. (2009) experimentally investigated the

effects of gas mixture rate, evaporator air inlet

temperature (from 24 to 32), evaporator air mass flow

rate (from 0.58 to 0.74), condenser air inlet temperature

(from 22 to 34) and condenser air mass flow rate (from

0.57 to 0.73) on the COP and the exergetic efficiency

values of vapour compression heat pump systems. The

investigation has been done for refrigerants R22 and

R404A five of their binary mixtures which contain about

0%, 25%, 50%, 75% and 100% mass fractions of R404A

were tested.

Akhilesh et al. (2008) present a detailed exergy

analysis of an actual vapour compression refrigeration

cycle. A computational model has been developed for

calculating the COP, exergetic efficiency, exergy

destruction and efficiency defects for R502, R404A and

R507A. The results of this investigations revealed that

R507A is a better substitutes to R502 than R404A.

Reddy et al. (2012) performed numerical analysis of

vapour compression refrigeration system using R134a,

R143a, R152a, R404A, R410A, R502 and R507A, and

discussed the effect of evaporator temperature, degree of

subcooling at condenser outlet, superheating of

evaporator outlet, vapour liquid heat exchanger

effectiveness and degree of condenser temperature on

COP and exergetic efficiency. They reported that

evaporator and condenser temperature have significant

effect on both COP and exergetic efficiency and also

found that R134a has the better performance while

R407C has poor performance in all respect.

Selladurai and Saravana kumar (2013) compared the

performance between R134a and R290/R600a mixture on

a domestic refrigerator which is originally designed to

work with R134a and found that R290/R600a

hydrocarbon mixture showed higher COP and exergetic

efficiency than R134a. In their analysis highest

irreversibility obtained in the compressor compare to

condenser, expansion valve and evaporator.

Nikolaidis and Probert (1998) studied analytically that

change in evaporator and condenser temperatures of two

stage vapour compression refrigeration plant using R22

add considerable effect on plant irreversibility. They

suggested that there is need for optimizing the conditions

imposed upon the condenser and evaporator.

Padilla et al. (2010) exergy analysis of domestic

vapour compression refrigeration system with R12 and

R413A was done. They concluded that performance in

terms of power consumption, irreversibility and exergy

efficiency of R413A is better than R12, so R12 can be

replaced with R413A in domestic vapour compression

refrigeration system.

Getu and Bansal (2008) had optimized the design and

operating parameters of like condensing temperature,

subcooling temperature, evaporating temperature,

superheating temperature and temperature difference in

cascade heat exchanger R744-R717 cascade refrigeration

system. A regression analysis was also done to obtain

optimum thermodynamic parameters of same system.

Spatz and Motta (2004) had mainly focused on

replacement of R12 with R410a through experimental

investigation of medium temperature vapour compression

refrigeration cycles. In terms of thermodynamic analysis,

comparison of heat transfer and pressure drop

characteristics, R410a gives best performance among

R12, R404a and R290a.

Mohanraj et al. (2009) concluded through

experimental investigation of domestic refrigerator they

arrived on conclusions that under different environmental

temperatures COP of system using mixture of R290 and

R600a in the ratio of 45.2: 54.8 by weight showing up to

3.6% greater than same system using R134a, also

discharge temperature of compressor with mixture of

R290 and R600a is lower in the range of 8.5-13.4K than

same compressor with R134a.

Han et al. (2007) Under different working conditions

experimental results revealed that there could be

replacement of R407C in vapour compression

refrigeration system having rotor compressor with

mixture of R32/R125/R161 showing higher COP, less

pressure ratio and slightly high discharge compressor

temperature without any modification in the same

system.

Halimic et al. (2003) had compared performance of

R401A, R290 and R134A with R12 by using in vapour

compression refrigeration system, which is originally

designed for R12.Due to similar performance of R134a in

comparison with R12, R134A can be replaced in the

same system without any medication in the system

components. But in reference to greenhouse impact R290

presented best results.

Xuan and Chen presented in this manuscript about the

replacement of R502 by mixture of HFC-161 in vapour

compression refrigeration system and conducted

experimental study it was found that mixture of HFC-161

gives same and higher performance than R404A at lower

and higher evaporative temperature respectively on the

vapour compression refrigeration system designed for

R404A.



212

Cabello et al. (2007) had studied about the effect of

operating parameters on first law efficiency (COP), work

input and cooling capacity of single-stage vapour

compression refrigeration system. There is great

influence on energetic parameters due change in suction

pressure, condensing and evaporating temperatures.

III. SYSTEM DESCRIPTION

The typical lay out of the Vapour compression system

in shown in Fig.1. Refrigerant leaves the evaporator, now

fully vaporized and slightly heated and returns to the

compressor inlet to continue the cycle

Fig. 1: Schematic Diagram of System Layout

Fig. 2. Pressure Enthalpy Diagram of Vapour Compression System

The above Fig. 2 represents the pressure-enthalpy

(p-h) diagram of a theoretical vapour compression

refrigeration cycle. In this cycle, the refrigerant enters the

compressor at state 1 at low pressure, low temperature

and is compressed isentropically to dry saturated vapour

state. The compressed dry saturated refrigerant is

discharged at state 2 as a high pressure, high temperature

and superheated vapour. The superheated vapour enters

the condenser where it gives out the latent heat to the

surrounding condensing medium.

The refrigerant enters the expansion devise where it

experiences a sudden drop in the pressure and

superheated vapour refrigerant is converted into partial

wet vapour. The liquid vapour mixture of the refrigerant

enters the evaporator at state 4 where it absorbs latent

heat of vaporization from the medium which is to be

cooled. The heat that is absorbed by the refrigerant at this

stage is called the refrigeration effect. The refrigerant

leaves the evaporator at low pressure, low temperature

and saturated vapour at point 1 and the cycle is

completed. The main characteristics of the tested

refrigerants as shown in Table 1.

Table 1.

Properties of Different Refrigerants used for the Analysis

S.No Property R12 R22 R134a

1Chemical formula / blend

compositionCCl₂F₂ CHCLF₂ CH₂FCF₃

2 Molar Mass (kg/kmol) 120.914 86.47 102.03

3 Critical Point Temperature Tc (°C) 113.23 96.15 101.06

4 Critical Pressure (Pc) (bar) 42 49.9 40.593

5 Critical Density (kg/m³) 565 523.842 511.9

6 Boiling Point -21.6 -42 -26.074

7 ODP 1 0.05 0

IV. PERFORMANCE ANALYSIS

For analysis the performance of vapour compression

refrigeration system, following assumption are made:

Degree of subcooling of liquid refrigerant in liquid-

vapour heat exchanger (Tsub) = 5K.

Mechanical efficiency of compressor (

) =

80%.

Difference between evaporator and space

temperature (Tr – Te) = 20 °C.

Evaporator temperature Tevap (in °C) ranging from

–40 °C to -10 °C.

Condenser temperature Tcond = 40 °C.

Dead state temperature (To) = 27 °C.

There is no pressure loss in pipelines.

In all components steady state operations are

considered.

The energy analysis based on first law of

thermodynamic, the performance of vapour compression

refrigeration system can be predicted in terms of

Coefficient of Performance (COP), which is defined as

the ratio of net refrigerating effect produced by the

refrigerator to the work done by the compressor. It is

expressed as:



213

(1)

The modern approach based on second law of

thermodynamic, i.e., exergy analysis can be used to

measures the performance of the vapour compression

refrigeration system. This analysis derives the concept of

exergy, which is always decreasing due to

thermodynamic irreversibilities. Exergy is the maximum

useful work that could be obtained from the system at a

given state in a specified environment. Exergy balance

for a control volume undergoing steady state process is

expressed as:

( ) ( ) ( ( ⁄ ) ) ( ( ⁄ ) )

(2)

Exergy Destruction (ED) in the System Components

Exergy destruction in each component of the cycle is

calculated as:

Exergy destruction in Evaporator

(

⁄ )

( ) (

⁄ ) (

)

(3)

Exergy destruction in Compressor

( ( )) (4)

Exergy destruction in Condenser

( ) ( ) (

⁄ ) (5)

Exergy destruction in Throttle valve

( ) ( ) (6)

Total Exergy Destruction

(7)

Exergetic Efficiency

| ⁄ | (8)

Exergy Destruction Ratio (EDR)

Exergy destruction ratio is the ratio of the total exergy

destruction in the system to the exergy in the product and

it is given by

EDR related to the exergetic efficiency given by:

(9)

V. RESULTS AND DISCUSSIONS

Performance analysis of vapour compression

refrigeration system has been carried out and figure 3

shows the effects of evaporating temperatures on

coefficient of performance.

With increase in evaporator temperature, the pressure

ratio across the compressor decreases, causing work done

by the compressor decrease and cooling capacity

increases due to increase in refrigerating effect. Hence,

the combined effect of these two factors increases the

COP of the vapour compression refrigeration system.

R12 shows better C.O.P than R22 and R134a followed by

the R22 with increase in evaporator temperature.

Figure 3. Variation of C.O.P with Evaporator Temperature

Figure 4 shows the variation of C.O.P with subcooling

of liquid refrigerant at the exit of condenser. It is evident

that increase in degree of subcooling increases the

cooling capacity because of increase in refrigerating

effect and there is no change in compressor work, hence

COP increases.



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Figure 4. Variation of C.O.P with Degree of Subcooling

Figures 5 shows the effect of evaporator temperatures

on exergetic efficiency ( ex) and with increase in

evaporator temperatures exergetic efficiency decreases.

The optimum evaporator is the temperature at which

maximum exergetic efficiency is obtained. R12 has the

highest exergy efficiency followed by R22 and R134A.

Figure 5. Variation of Exergy Efficiency with Evaporator

Temperature

Figure 6 shows the curves trend for EDR almost

reverses to curves of exergetic efficiency. The rise and

fall of the exergetic efficiency, depends upon the two

parameters. First parameter is the exergy of cooling

effects, i.e. (

⁄ ) with increase in evaporator

temperature Qe increases whereas the term (

⁄ )

reduces.

Second parameter is the compressor work required by

compressor W which decreases with increase in

evaporator temperature. Both terms Qe and W have

positive effect on increase of exergetic efficiency

whereas the term (

⁄ ) has negative effect on

increase of exergetic efficiency. The combined effects of

these two parameters, increases exergetic efficiency till

the optimum evaporator temperature and beyond the

optimum temperature decrease. Because of exergetic

efficiency is inversely proportional to EDR; the curves

trend for EDR almost reverses to curves of exergetic

efficiency. With increases in evaporating temperatures,

EDR decreases till the optimum evaporator temperature

and beyond this optimum temperature it increase. The

optimum evaporator is the temperature at which

minimum EDR is obtained.

Figure 6. Variation of EDR with Evaporator Temperature

Figures 7 & 8 presents the effect of degree of

subcooling on exergetic efficiency and EDR. It is evident

that increase in degree of subcooling increases the

cooling capacity because of increase in refrigerating

effect and there is no change in compressor work, hence

COP increases. From the study, it is evident that increase

in COP increases the exergetic efficiency and reduces the

EDR. The R12 has the highest exergy efficiency on

different ranges of subcooling which are 0.2173, 0.212,

0.208, 0.205 & 0.1999 0n 10C, 7C, 5C, 3C & 0 C

followed by the R22 and R134A except on 10C of

subcooling on which R134A has maximum exergetic

efficiency than R22.

3

3.1

3.2

3.3

3.4

3.5

3.6

3.7

0 3 5 7 10

C.O

.P

Degree of Subcooling (C)

R12 R22 R134A

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

-40 -30 -20 -10

Exer

gy E

ffic

ien

cy

Evaporator Temp.(C)

R12 R22 R134A

2

2.5

3

3.5

4

4.5

5

5.5

-40 -30 -20 -10

ED

R

Evaporator Temp. (C)

R12 R22 R134a



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Figure 7. Variation of Exergy Efficiency with Degree of Subcooling

Figure 8. Variation of EDR with Degree of Subcooling

VI. CONCLUSION

A computational model based exergy analysis is

presented for the investigation of the effects of

evaporating temperatures and degree of subcooling on

the COP, exergetic efficiency and EDR of the vapour

compression refrigeration cycle for R12, R22 and

R134A. The conclusions present in this analysis are

given as follows:

The COP and exergetic efficiency of R12 are better

than that of R22 and R134A. The EDR of R134A is

higher than that of R22 and R12. This analysis

performed at condenser temperature on 40C and

evaporator temperatures ranges from -10C to -40C.

For all refrigerants R12, R22 and R134A COP and

exergy efficiency increases with increase in degree of

subcooling.

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options for replacing HCFC-22 in medium temperature refrigeration systems”, Int J Refrigeration, 27:475-483

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[16] Venkataramanamurthy V P and Senthil Kumar P (2010),

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performance study on R32/R125/R161 as an alternative refrigerant to R407C”, Int J Applied Thermal Engineering.

0.18

0.185

0.19

0.195

0.2

0.205

0.21

0.215

0.22

0 3 5 7 10

Ex

erg

y E

ffic

ien

cy


R12 R22 R134A

3.3

3.4

3.5

3.6

3.7

3.8

3.9

4

4.1

4.2

4.3

0 3 5 7 10

ED

R


R12 R22 R134A



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[18] Yongmei Xuan, Guangming Chen, “Experimental study on HFC-

161 mixture as an alternative refrigerant to R502”, Int J Refrigeration, Article in Press.

NOMENCLATURE

COP Coefficient of Performance

W Work Rate (kW)

EDR Exergy Destruction Ratio

S Entropy (kJ/kgK)

Ed Exergy destruction (kW)

Ex Exergy of Refrigerant (kW)

h Enthalpy (kJ/kg)

T Temperature (K)

exergy Exergy Efficiency

To Temperature of Dead State

Tr Temperature of space

Tc Temperature of condenser

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