International Journal of Engineering Technology, Management and Applied Sciences

www.ijetmas.com January 2016 , Volume 4, Issue 1, ISSN 2349-4476

40 Prakash U, Dr Vijayan R, Vijay P

Energy and Exergy Analysis of Vapour Compression

Refrigeration System with Various Mixtures of HFC/HC

Prakash U

P.G. Scholar, Department of

Mechanical Engineering

Government College of

Engineering, Salem, Tamil Nadu,

India

Dr Vijayan R

Associate professor, Department

of Mechanical Engineering

Government College of

Engineering, Salem, Tamil Nadu,

India

Vijay P

Assistant professor, Department of

Mechanical Engineering

Knowledge Institute of

technology, Salem, Tamil Nadu,

India

ABSTRACT

This paper deals with the energetic and exergetic performance of vapour compression refrigeration system with the

appropriate mass proportion of R152a/R600a, R152a/R600, R152a/R1270 and R152a/R32/R600a to replace R12. In this

analysis, a computational model based on energetic and exergetic analysis of vapour compression refrigeration system is

generated and has been investigated using MATLAB for the effects of evaporator temperatures on exergy efficiency,

exergy defect on different components and coefficient of performance. The exergy efficiency and the coefficient of

performance increase whereas the exergy destruction ratio decrease with decreasing temperature difference between the

evaporator and refrigerated space. Energy and Exergy analysis on vapour compression refrigeration system, using

R152a/R600a (0.9/0.1), R152a/R600 (0.9/0.1), R152a/R1270 (0.92/0.8) and R152a/R32/R600a (0.85/0.07/0.08) have

been carried out with the help of CYCLE-D software, to illustrate the various exergy defect occurring in the different

components and to display the potential improvements.

Keywords: - Energy and Exergy analysis, vapour compression refrigeration system, alternative refrigerant, HCF/HC

blend.

Nomenclature

COP Coefficient Of Performance EDR Exergy Destruction Ratio

Qe Refrigeration effect I Exergy loss

Wc Compression work Specific exergy

T0 Dead state temperature s Specific entropy

Tc Condenser temperature h Specific enthalpy

Te Evaporator temperature m Mass flow rate

Tr Refrigerated space temperature GWP Global Warming Potential

isen Isentropic efficiency ODP Ozone Depletion Potential

M Mechanical efficiency HFC Hydro-Fluoro Carbon

E Electrical efficiency HC Hydrocarbon

ex Exergy efficiency WE Electrical power

1. INTRODUCTION

The demand for energy is increasing exponentially, therefore, it is necessary to harness and utilize energy

with higher efficiency or with fewer energy losses. Refrigeration plays a very important task in domestic,

industrial and commercial sectors for various application such as cooling, heating, food preserving, etc. The

Refrigeration system is a work consuming device whereas the refrigerant used releases harmful emissions.

However, in a hunt to find out alternate and eco-friendly refrigerants, the performance of the refrigerant plays

a significant role in the current scenario.

International Journal of Engineering Technology, Management and Applied Sciences

www.ijetmas.com January 2016 , Volume 4, Issue 1, ISSN 2349-4476

41 Prakash U, Dr Vijayan R, Vijay P

Cengel and Boles (2011) presented that the energy analysis based on the first law of thermodynamic is

concerned only with the law of conservation of energy and, therefore it cannot tell about how, where and how

much the system performance is degraded. In order to determine the actual inefficiencies due to

irreversibilities in the process exergy analysis, which is based on the second law of thermodynamic, is the

appropriate method. Unlike energy analysis, the exergy analysis determines the amount of irreversibilities

associated in the process qualitatively and thereby, that indicates the direction in which the researchers should

concentrate more in order to enhance the performance of the system [1]. Arora et al. (2008) represented a

computational model to determine COP, exergetic efficiency and exergy defects for R502, R404A and

R507A. They concluded that COP and exergetic efficiency for R507A are better than R502 and R404A [2].

Recep Yumrutes et al. (2002) found that the condenser and evaporator temperatures have strong effects on

exergy losses in the condenser and evaporator and on the COP and exergy efficiency of the cycle but little

effects on evaporator and compressor [3]. P. D. Malwe et al. (2014) concluded that the lowest exergy

efficiency valve is found for the compressor as it follows non-isentropic compression. Losses due to entropy

generation, leakages in the pipelines and system irreversibilities contribute major exergy defects in the system

[4]. Md. Nawaz Khan et al. (2008) reports the exergy analysis for theoretical VCR system using R12, R22

and R134a. The COP and exergy efficiency of R12 are better than that of R22 and R134a. R134a has high

EDR than R22 and R12 [5].

Jyoti Soni et al. (2012) reported with a computational model the COP and exergy efficiency improve by

sub-cooling. With an increase in dead state temperature, the exergy efficiency increases and exergy

destruction ratio decreases while COP remains constant [6]. Ahamed et al. reviewed on exergy analysis

vapour compression refrigeration system. They concluded that maximum exergy defect occurred in the

compressor, however, staging of compression process could be helpful for reducing compressor losses in the

system. Exergy efficiency can be enhanced by sub-cooling up to 50C [7]. H. C. Bayrakci et al. (2009) carried

out the exergy analysis using pure HC refrigerants. In their analysis, R600a can be assumed as an alternative

for R22 and R134a. However, in the energy and exergy point of view, the suitable alternative to R22 is R1270

[8]. B.O. Bolaji (2010) presented that the highest exergy efficiency was using R152a in the system. Exergy

efficiency of the system using R152a and R134a are 4.4% higher and 13.6% lower than that of R12,

respectively [9]. A. Yataganbaba et al. (2015) experimentally studied that the exergy analysis using R1234yf,

R1234ze and R134a. The R1234ze has highest exergetic efficiency than other refrigerants and it has 238 times

lower GWP than R134a [10]. S.K. Kalla et al. (2014) reviewed on alternative refrigerant. Refrigerant mixtures

of R290/R600a (40%wt / 60%wt) instead of R12 and R290/R1270 (20%wt / 80%wt) instead of R22 are found

to be suitable alternative refrigerant [11]. Arora et al. (2007) provide a computational model for exergy

analysis. In their analysis, R410A is a better alternative refrigerant as compared R407C for refrigeration

system whereas for air-conditioning system R407C is better alternative refrigerant than R410A [12]. R.S.

Mishra (2014) concluded that COP and exergy efficiency of vapour compression refrigeration system using

R717 is significantly higher but it has toxic nature. The COP and exergy efficiency for R600 and R152a are

nearly overlapping the same valves and are better than R125 [13].

In this paper, a computation model has been generated using MATLAB for calculating the COP, Exergy

efficiency and EDR for various HFC/HC mixtures. The thermo-physical valves of various HFC/HC mixtures

are obtained by CYCLE-D software.

2. SYSTEM DESCRIPTION

The simple layout of vapour compression refrigeration system is shown in figure1.The four essential

components of vapour compression refrigeration system are compressor, condenser, expansion valve and

evaporator. In the compressor, the low pressure and temperature vapour refrigerant from the evaporator is

compressed and then it is allowed to pass through the condenser coil. The refrigerant is cooled and condensed,

when passing through the condenser, by giving up its latent heat to the surrounding cooling medium.

International Journal of Engineering Technology, Management and Applied Sciences

www.ijetmas.com January 2016 , Volume 4, Issue 1, ISSN 2349-4476

42 Prakash U, Dr Vijayan R, Vijay P

Fig.1: Schematic diagram and p-h diagram of vapour compression refrigeration system.

The expansion valve reduces the pressure and temperature by allowing it to pass at a controlled rate,

whereas some of the liquid refrigerants tend to evaporate. In the evaporator, the liquid vapour refrigerant

absorbs its latent heat of vaporization from the medium to be cooled and obtained as saturated vapour

(Khurmi and Gupta, 2003) [14].

3. PERFORMANCE ANALYSIS

For energy and exergy analysis following assumptions are made:

1. Steady-state operations are considered in all components. 2. Exergy of kinetic and potential energy components are neglected. 3. There is no pressure loss in the pipelines. 4. The power inputs to the condenser and evaporator fans are neglected.

Table II. Operating conditions of the VCR system

Dead state temperature (T0) 250C

Difference between refrigerated space and evaporator temperature (Tr - Te) 150C

Condenser temperature (Tc) 300C

Evaporator temperature (Te) -500 to -10

0C

Isentropic efficiency of compressor (isen) 80%

Mechanical efficiency of compressor (M) 90%

Electric motor efficiency (E) 90%

System cooling capaci