Scholarly article on topic 'Theoretical Performance Investigation of Vapour Compression Refrigeration System Using HFC and HC Refrigerant Mixtures as Alternatives to Replace R22'

Theoretical Performance Investigation of Vapour Compression Refrigeration System Using HFC and HC Refrigerant Mixtures as Alternatives to Replace R22 Academic research paper on "Mechanical engineering"

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Abstract of research paper on Mechanical engineering, author of scientific article — Sharmas Vali Shaik, T.P. Ashok Babu

Abstract The present paper describes the theoretical thermodynamic performance of vapour compression refrigeration system using HFC and HC blends as an alternatives to replace the refrigerant R22. In this study thermodynamic analysis of window air conditioner with R431A, R410A, R419A, R134a, R1270, R290 and fifteen refrigerant mixtures consists of R134a, R1270 and R290 was carried out based on actual vapour compression cycle. All the investigated refrigerant mixtures are ozone friendly in nature and they possess GWP in the range of 0.0244 to 1.685 times the GWP of R22. Thermodynamic performance analysis of all the investigated refrigerant mixtures were evaluated at the condensing and evaporating temperatures of 54.4oC and 7.2oC respectively. The results show that COP for the refrigerant mixture R134a/R1270/R290 (50/5/45 by mass percentage) is 2.10% higher among the R22, R431A, R410A, R419A, R134a, R1270, R290, and fifteen studied refrigerant mixtures. The compressor discharge temperature of all the studied refrigerants were lower than that of R22 by 4.8oC-22.2oC. The power consumption per ton of refrigeration for the refrigerant mixture R134a/R1270/R290 (50/5/45 by mass percentage) is 2.01% lower among R22, R431A, R410A, R419A, R134a, R1270, R290, and fifteen studied refrigerant mixtures. Overall the thermodynamic performance of refrigerant mixture R134a/R1270/R290 (50/5/45 by mass percentage) is better than that of R22 with reasonable savings in the energy and hence it is an appropriate ecologically energy efficient alternative refrigerant to substitute R22 used in air conditioning applications.

Academic research paper on topic "Theoretical Performance Investigation of Vapour Compression Refrigeration System Using HFC and HC Refrigerant Mixtures as Alternatives to Replace R22"

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Energy Procedía 109 (2017) 235 - 242

International Conference on Recent Advancement in Air Conditioning and Refrigeration, RAAR 2016, 10-12 November 2016, Bhubaneswar, India

Theoretical Performance Investigation of Vapour Compression Refrigeration System Using HFC and HC Refrigerant Mixtures as

Alternatives to Replace R22

Sharmas Vali Shaika, T. P.Ashok Babub*

aNational Institute of Technology Karnataka, Department of Mechanical Engineering ,Surathkal, Mangalore-575025, Karnataka, India. b*National Institute of Technology Karnataka, Department of Mechanical Engineering ,Surathkal, Mangalore-575025, Karnataka, India.

Abstract

The present paper describes the theoretical thermodynamic performance of vapour compression refrigeration system using HFC and HC blends as an alternatives to replace the refrigerant R22. In this study thermodynamic analysis of window air conditioner with R431A, R410A, R419A, R134a, R1270, R290 and fifteen refrigerant mixtures consists of R134a, R1270 and R290 was carried out based on actual vapour compression cycle. All the investigated refrigerant mixtures are ozone friendly in nature and they possess GWP in the range of 0.0244 to 1.685 times the GWP of R22. Thermodynamic performance analysis of all the investigated refrigerant mixtures were evaluated at the condensing and evaporating temperatures of 54.4oC and 7.2oC respectively. The results show that COP for the refrigerant mixture R134a/R1270/R290 (50/5/45 by mass percentage) is 2.10% higher among the R22, R431A, R410A, R419A, R134a, R1270, R290, and fifteen studied refrigerant mixtures. The compressor discharge temperature of all the studied refrigerants were lower than that of R22 by 4.8oC-22.2oC. The power consumption per ton of refrigeration for the refrigerant mixture R134a/R1270/R290 (50/5/45 by mass percentage) is 2.01% lower among R22, R431A, R410A, R419A, R134a, R1270, R290, and fifteen studied refrigerant mixtures. Overall the thermodynamic performance of refrigerant mixture R134a/R1270/R290 (50/5/45 by mass percentage) is better than that of R22 with reasonable savings in the energy and hence it is an appropriate ecologically energy efficient alternative refrigerant to substitute R22 used in air conditioning applications.

© 2017 The Authors.Publishedby Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.Org/licenses/by-nc-nd/4.0/).

Peer-review under responsibility of the organizing committee of RAAR 2016.

* Corresponding author. Tel.: + 91-9986548546. E-mail address: tpashok@rediffmail.com

1876-6102 © 2017 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Peer-review under responsibility of the organizing committee of RAAR 2016. doi:10.1016/j.egypro.2017.03.053

Keywords: COP; Compressor discharge temperature; GWP; HFC and HC blends; ODP

1. Introduction

Due to ozone depletion and high global warming potential of hydrochlorofluorocarbon refrigerant R22, Montreal protocol 1987 have been decided to phase out HCFCs by 2030 in all developed countries and by 2040 in developing countries [1, 2]. So far no pure substance was available to substitute R22 used in heat pump and air conditioning devices. Hence it is essential to develop new refrigerant mixtures which are ecologically friendly in nature to replace R22. From the past few years hydrofluorocarbons (HFCs) like R410A and R407C were used as alternatives to the refrigerant R22. The main disadvantage of R410A and R407C is higher global warming potential (GWP) than R22 and also COP was lower than that of R22. To overcome high GWP problem, eco-friendly hydrocarbons like R290, R1270 and R600a were used. Hydrocarbon refrigerants possess all required properties except their flammability in nature. The flammability of hydrocarbons was lowered by blending with the HFCs. Investigation results reported that there was a possibility to blend the hydrocarbons with HFCs [3]. From the experimental studies it was observed that the flammability of hydrocarbons was reduced by mixing them with the HFCs [4]. Experimental studies was carried out in a heat pump with R134a/ R290 (55/45 by mass %) and R134a/R600a (80/20 by mass %). Both the refrigerant mixtures are azeotropic. Performance parameters of these azeotropic refrigerants were compared with R22, R12, R134a and R290. It was reported that capacity of R134a/R290 mixture (55/45 by mass %) was greater than that of R22 and R290 whereas COP was lower than that of R22 and R290 respectively. R134a/R600a mixture (80/20 by mass %) showed higher COP and capacity than R134a and R12 respectively [5]. Theoretical and experimental studies were conducted in a window air conditioner with new refrigerant mixtures like R125/R290, R32/ R290, R32/R125/R290 and R32/ R125/ R152a as an alternatives to R22. In this study the composition of various refrigerant mixtures was not mentioned. Results showed that the performance of R32/R125/R152a was near to the refrigerant R22 throughout the working conditions which has higher efficiency under varying working conditions. Therefore it was essential that composition of all these refrigerant mixtures must be optimized as per working conditions of the unit. But researchers were not mentioned about the optimum composition to the R32/R125/R152a mixture for which performance was near to R22 [6]. Experimental tests were carried out with HFC and HC refrigerant blends consists of R134a, R32, R125, R152a, R290 and R1270 as alternative refrigerants to replace R22. Test results revealed that COP and capacity of refrigerant mixtures consists of R32/R125/R134a (26/14/60 by mass% and 26/20/54 by mass %) was 4 to 5% greater than the refrigerant R22. Capacity of binary refrigerant mixtures R32/R134a (30/70 by mass % and 26/74 by mass %) revealed similar capacity to that of R22 and COP was 7% higher than the R22. COP and capacity of binary mixture azeotrope consists of R290/R134a (45/55 by mass %) was 3 to 4% greater than that of R22. The discharge temperature of compressor for all the investigated refrigerants were lower than the R22. Thus it indicates the longer life of the compressor when compared to R22 [7]. Experimental performance testing of R431A (71%R290/29%R152a by mass) was conducted in a heat pump device under both heat pump and air conditioning operating conditions. Results reported that the COP of R431A was 3.5 to 3.8% higher than the R22 whereas capacity was similar to the R22 under both heat pump and air conditioning working conditions. Overall R431A was a suitable eco-friendly refrigerant to substitute R22 [8]. Theoretical thermodynamic performance was carried out with R410A (50%R32/50%R125 by mass) and R419A (77%R125/19%R134a/4%RE170 by mass) as alternatives to R22. Results reported that refrigeration effect and Coefficient of performance of R22 and R410A was higher than the R419A whereas the performance of R410A was near to the R22 in all the working conditions. Hence R410A was recommended as a possible drop in substitute to R22 [9]. Apart from R431A, R410A and R419A, in the present study performance investigation of HFC and HC blends consists of R134a, R1270 and R290 at different compositions is carried out to substitute R22. In this study pressure drop at high pressure side of the system is taken as 0.5 bar whereas at low pressure side of the system is 0.3 bar.

Nomenclature

ARI Air conditioning and refrigeration institute Q Combustion heat in (kJ/mol)

COP Coefficient of performance R Gas constant (J/kg K)

GWP Global warming potential RE Refrigeration effect (kJ/kg)

hi Enthalpy at the entry of compressor (kJ/kg) Qc Refrigeration capacity (W)

hic Enthalpy at the exit of evaporator (kJ/kg) tc Condensing temperature (oC)

h2 Enthalpy at the exit of compressor (kJ/kg) te Evaporating temperature (oC)

h4 Enthalpy at the entry of evaporator (kJ/kg) Td Compressor discharge temperature (oC)

HC Hydrocarbons TR Ton of refrigeration (kW)

HCFCs Hydrochlorofluorocarbons U Upper limit of flammability (kg/m3)

HFCs Hydrofluorocarbons V Specific volume (m3/kg)

L Lower limit of flammability (kg/m3) W Power per ton of refrigeration (kW/TR)

m Mass flow rate of the refrigerant (kg/min) Wc Compressor work (kJ/kg)

M Molecular weight (kg/kmol)

ODP Ozone depletion potential

P Pressure (Pa)

2. New refrigerant mixtures

In the present study R431A, R410A, R419A, three pure fluids (R134a, R1270 and R290) and fifteen refrigerant mixtures consists of R134a, R1270 and R290 at different compositions is considered to compute the performance of window air conditioner. Refrigerant mixtures 5, 6, 7, 8, 9, 10, 11, 13, 14, 15, 16 and 22 (as given in table 1) are non azeotropes whereas mixtures 17, 18, 19, 20 and 21 (as given in table 1) are near azeotropes whose temperature glide is less than 0.6oC. And for the refrigerant mixture 12 (given in table 1) is almost azeotropic because its temperature glide is 0.01oC. A matlab program is written to develop the thermodynamic properties of selected refrigerant mixtures by using martin-hou equation of state [10]. Martin-hou equation of state is given below.

-5.4757 -5.4757

RT A2+B2T + C2e Tc A3+B3T + C3e Tc A. B5T m

P =--U—------I- —-------1-----1-----(1)

V-b (V-b)2 (V-by (y-b)* (V-b)s

The developed properties of studied refrigerant mixtures are not available in literature and therefore they are compared with Refprop [11]. The percentage variation in developed properties from Refprop are 3.5 to 4.8 % within the working pressure and temperature. Therefore the procedure followed to develop the properties is precise. The critical properties required for the refrigerant mixtures are taken from the Refprop. The basic properties of considered refrigerants are given below in table 1.

Table 1. Basic properties of investigated refrigerants

Refrigerant designation Composition Molecular Boiling Critical Critical ODP GWP Temperature

By mass % weight point Pressure Temperature (100years) Glide (oC)

(kg/kmol) (oC) (Mpa) (K)

1 R22 Pure fluid 86.5 -40.81 4.99 369.3 0.055 1760 0

2 R134a Pure fluid 102.0 -26.07 4.0593 374.21 0 1300 0

3 R1270 Pure fluid 42.1 -47.69 4.66460 365.57 0 2 0

4 R290 Pure fluid 44.0 -42.11 4.2512 369.89 0 3 0

5 (R134a/R290) 60/40 66.88 -43.47 3.9852 353.98 0 781 2.66

6 (R134a/R1270) 60/40 64.99 -42.57 4.2308 357.01 0 781 4.15

7 (R 134a/R1270/R290) 80/10/10 80.097 -35.07 4.1184 358.46 0 1040 10.8

8 (R134a/R1270/R290) 60/20/20 65.924 -43.03 4.0965 355.13 0 781 3.55

9 (R134a/R1270/R290) 65/5/30 69.627 -41.35 3.993 353.9 0 846 4.86

10 (R134a/R1270/R290) 60/5/35 66.64 -43.37 4.0105 354.21 0 781 2.88

11 (R134a/R1270/R290) 55/5/40 63.898 -45.31 4.0411 354.98 0 716 0.97

12 (R134a/R1270/R290) 50/5/45 61.373 -46.28 4.079 356.08 0 652 0.01

13 (R134a/R1270/R290) 65/30/5 68.335 -40.89 4.1732 356.55 0 846 5.6

14 (R134a/R1270/R290) 60/35/5 65.223 -42.68 4.1957 356.46 0 781 4.06

15 (R134a/R1270/R290) 55/40/5 62.383 -44.33 4.2244 356.67 0 716 2.64

16 (R134a/R1270/R290) 50/45/5 59.779 -45.68 4.2569 357.08 0 651 1.48

17 (R134a/R1270/R290) 50/15/35 60.967 -46.38 4.1144 356.07 0 651 0.17

18 (R134a/R1270/R290) 50/20/30 60.766 -46.32 4.1343 356.12 0 651 0.36

19 (R134a/R1270/R290) 50/25/25 60.566 -46.22 4.1557 356.22 0 651 0.59

20 R431A(R290/R152a) 71/29 48.8 -43.21 4.2194 364.94 0 43 0.01

21 R410A(R32/R125) 50/50 72.585 -51.36 4.9012 344.49 0 2088 0.08

22 R419A(R125/R134a/RE170)_77/19/4 109.39 -35.85 4.0602 356.65_0 2967_6/79

3. Refrigerant flammability number analysis:

Investigation of flammability for developing various alternative refrigerant mixtures is essential. Hence flammability limit is most commonly used as an index to denote the flammability properties of refrigerants. It is proposed that refrigerant flammability number (RF number) is used for denoting the potential combustion hazard of the refrigerants. It is convenient to express the combustion hazards with regard to flammability limits of each compound with the help of RF number. The procedure for evaluating the RF number of refrigerants is given in the literature [12]. And from this literature the correlation used for computing the refrigerant flammability number is given below.

RF -number =

Depending upon the RF number, refrigerants are classified into different categories. Refrigerants with RF number below 30 are classified into mildly flammable refrigerants (ASHRAE A2), those which are in between 30 to 150 as flammable refrigerants (ASHRAE A3) and refrigerants which are higher than 150 are categorized as strongly flammable. In the present study the flammability number of fifteen studied refrigerant mixtures are computed by using the above equation (2). All the fifteen investigated refrigerant mixture are categorized as mildly flammable refrigerants (A2) since RF number of these refrigerants are less than 30.

4. Thermodynamic performance analysis:

Thermodynamic performance investigation of R22 and its different alternative refrigerant mixtures which is considered in this study is carried out based on actual vapour compression refrigeration cycle. In this performance investigation, pressure drop occurred in the condenser and evaporator, pressure drop through suction and discharge valve, superheating of the refrigerant vapour in the evaporator and subcooling of refrigerant liquid in the condenser is considered. The increase in temperature due to heat gain at compressor inlet and decrease in temperature due to heat loss at compressor outlet is assumed as 10oC. The degree of subcooling and superheating is assumed as 5oC and 10oC respectively. A matlab code is developed to evaluate the thermodynamic performance analysis of the vapour compression refrigeration cycle. Actual vapour compression refrigeration cycle on p-h diagram is shown in figure 1.

Enthalpy h (kJ/kg)

Fig. 1. Actual vapour compression refrigeration cycle on p-h diagram.

The description of various state points of the cycle as shown in figure 1 are given in Table 2 [13].

Table 2. Description of various state points of the thermodynamic cycle

State points Explanation of various states of the thermodynamic cycle

4-1m Evaporator pressure drop

1m-1c Superheat of refrigerant vapour in the evaporator

1c-1k Heat gain and superheating of the refrigerant vapour through the suction line

1k-1j Suction line pressure drop

1j-1 Pressure drop through the suction valve

1-2 Polytropic compression

2-2j Pressure drop through the discharge valve

2j-2k Discharge line Pressure drop

2k-2l Heat loss and desuperheating of refrigerant vapour through the discharge line

2k-3 Condenser pressure drop

3-3j Subcooling of refrigerant liquid in the condenser

3j-3k Heat gain in the liquid line

Window air conditioner capacity, operating condition for investigated refrigerant mixtures and pressure drop values at different state points of the cycle are given in table 3 and table 4 respectively [14].

Table 3. ARI conditions

Refrigerant capacity (TR) Evaporator temperature te (oC) Condensing temperature tç (oC)

R22 08 72 54.4

Table 4. Pressure drop values at various points of the cycle

_Description_Pressure drop in bar

Pressure drop through suction valve 0.2 Pressure drop through discharge valve 0.4 Suction line pressure drop 0.1 Discharge line pressure drop 0.1 Evaporator pressure drop_0-1_

The calculations involved in the thermodynamic performance of the vapour compression cycle are given below.

1. Compressor work is determined by Wc = h2 — h1

2. Refrigerating effect is given by RE = hlc — hA

3. Coefficient of performance is calculated as COP = RE/WC

4. Power consumption per ton of refrigeration W = 3.5167 x WC/RE = 3.5167/COP Summary of results for the investigated refrigerant mixtures are given in Table 5.

Table 5. Summary of results for the considered refrigerant mixtures

Refrigerant designation Composition m RE Wc COP Differ Td Power per ton Ashrae

By mass % kg/min kJ/kg kJ/kg ence in (oC) of flammabi

COP refrigeration lity group

(%)_(kW/TR)

1 R22 Pure fluid 1.226 137.672 38.949 3.534 0 95.85 0.994 A1

2 R134a Pure fluid 1.339 125.973 38.638 3.26 -7.76 73.59 1.078 A1

3 R1270 Pure fluid 0.719 234.715 73.633 3.187 -9.81 77.79 1.103 A3

4 R290 Pure fluid 0.737 228.9 72.496 3.157 -10.67 70.4 1.113 A3

5 (R134a/R290) 60/40 0.921 183.08 60.001 3.051 -13.67 75.56 1.152 A2*

6 (R134a/R1270) 60/40 1.035 162.99 64.716 2.518 -28.74 85.73 1.396 A2*

7 (R134a/R1270/R290) 80/10/10 1.028 164.129 47.366 3.465 -1.96 77.48 1.014 A2*

8 (R134a/R1270/R290) 60/20/20 0.894 188.71 54.919 3.436 -2.78 77.54 1.023 A2*

9 (R134a/R1270/R290) 65/5/30 0.907 186.034 52.487 3.544 0.27 75.88 0.992 A2*

10 (R134a/R1270/R290) 60/5/35 0.875 192.739 54.032 3.567 0.91 75.71 0.985 A2*

11 (R134a/R1270/R290) 55/5/40 0.847 199.241 55.432 3.594 1.68 75.55 0.978 A2*

12 (R134a/R1270/R290) 50/5/45 0.819 205.969 57.072 3.608 2.10 75.66 0.974 A2*

13 (R134a/R1270/R290) 65/30/5 0.945 178.543 53.754 3.321 -6.03 79.22 1.058 A2*

14 (R134a/R1270/R290) 60/35/5 0.919 183.487 54.795 3.348 -5.26 78.96 1.05 A2*

15 (R 134a/R1270/R290) 55/40/5 0.895 188.508 56.47 3.338 -5.55 79.22 1.053 A2*

16 (R134a/R1270/R290) 50/45/5 0.871 193.59 58.215 3.325 -5.91 79.58 1.057 A2*

17 (R134a/R1270/R290) 50/15/35 0.829 203.461 57.524 3.536 0.06 76.57 0.994 A2*

18 (R134a/R1270/R290) 50/2 0/30 0.835 202.063 57.675 3.503 -0.88 77.03 1.003 A2*

19 (R134a/R1270/R290) 50/25/25 0.841 200.577 57.828 3.468 -1.87 77.52 1.013 A2*

20 R431A(R290/R152a) 71/29 0.665 253.655 76.320 3.323 -5.97 90.96 1.058 A3

21 R410A(R32/R125) 50/50 1.125 149.911 44.570 3.363 -4.83 88.99 1.045 A1

22 R419A(R 125/R134a/RE 170) 77/19/4 1.90 88.841 32.123 2.765 -21.76 74.98 1.271 A2

* Estimated values

5. Results and Discussions:

5.1. Refrigeration effect and compressor work

Figure 2 (a) illustrates the refrigeration effect of alternative refrigerant mixtures. Figure 2 (b) illustrates the compressor work of alternative refrigerant mixtures which is investigated in the present study. From the figure 2 (a) and 2 (b) it is observed that refrigeration effect and compressor work increases for propylene (R1270), propane (R290) and R431A (3, 4 and 20 in table 5) among the R22, R134a, R410A, R419A and other fifteen studied refrigerant mixtures composed of R134a, R1270 and R290. Since enthalpy values of R1270, R290 and R431A are higher at the operating conditions when compared to R22, R134a, R410A, R419A and other fifteen studied refrigerant mixtures. Depending upon composition and type of refrigerants used in the present study both compressor work and refrigeration effect increase for the mixtures 5 to 19 (in table 5) when compared to R22, R134a, R410A and R419A. It is also observed that both refrigeration effect and compressor work decreases for the refrigerant mixture R419A. Because enthalpy values of R419A are lower at the working conditions when compared to all the studied refrigerants.

2 O CD

I Refrigeration Effect (kj/kg)

. s « 3 s

- 2 a «

■J 2, g 4

¡! S i

3 S S 1 2 N d 7 ^ S " 5 = =

I 2 J 4 5 6 7 8 9 10 II 12 13 14 1516 171819 2021 22 Refrigerant mixtures

6 7 8 9 10 11 12 1314 151617 1819 20 2] 22 Refrigerant mixtures

Fig. 2. (a) Refrigeration effect of alternative refrigerant mixtures; (b) Compressor work of alternative refrigerant mixtures.

5.2. Coefficient of performance and percentage difference in COP

COP is taken as an energy efficient index for a given device when it is charged with a specific refrigerant. Hence it is essential to study the COP of various mixture refrigerants against the refrigerant R22 when choosing its alternatives to substitute R22. Figure 3 (a) illustrates the COP of alternative refrigerant mixtures. Figure 3 (b) illustrates the percentage difference in COP of alternative refrigerant mixtures. From the figure 2 (a) and 2 (b) it is clear that the net effect of compressor work and refrigeration effect on the COP of various studied refrigerants either increases or decreases or remains same, depending upon the type of refrigerants, composition of refrigerants and also on the working conditions of the system. From the figure 3 (a) and 3 (b) it is observed that COP of ternary

refrigerant mixture R134a/R1270/R290 (12 in table 5) was 2.10% higher among the R22, R431A, R410A, R419A, R134a, R1270, R290, and other fifteen studied refrigerant mixtures composed of R134a, R1270 and R290. The poor performance is observed for the binary refrigerant mixture R134a/R1270 and R419A (6 and 22 in table 5).

Coefficient of Performance

2 3 4 5 6 7 8 9 10 II 12 13 14 15 16 17 IS 19 20 21 22

Refrigerant mixtures

10 11 12 13 1415 11) 17 18 19 20 21 22

Refrigerant Mixtures

Fig. 3. (a) COP of alternative refrigerant mixtures; (b) Percentage difference in COP of alternative refrigerant mixtures.

5.3. Compressor discharge temperature and Power per ton of refrigeration

Fig. 4. (a) Compressor discharge temperature of alternative refrigerant mixtures; (b) Power per ton of refrigeration for alternative refrigerant

mixtures.

Figure 4 (a) shows the compressor discharge temperature of alternative refrigerant mixtures. While employing alternative refrigerants the lifespan, consistency of the system and durability of the compressor motor should be studied. These parameters can be investigated by calculating the discharge temperature of the compressor. From the figure 4 (a) it is observed that compressor discharge temperature for all the investigated refrigerant mixtures were reduced by 4.8oC-22.2oC when compared to the R22. The lower compressor discharge temperature is advantageous from the stand point of durability of the compressor life.

Figure 4 (b) shows the power per ton of refrigeration for alternative refrigerant mixtures. If the power consumption per ton of refrigeration is lees then the performance of the system can be increased. From the figure 4 (b) it is observed that the power consumption per ton of refrigeration for the refrigerant mixture R134a/R1270/R290 (12 in table 5) is less compared to the refrigerant R22 and other studied refrigerants. Therefore performance of the mixture (12 in table 5) is higher among R22 and other studied refrigerants. But for the refrigerants R134a/R1270 and R419A (6 and 22 in table 5) power consumption per ton of refrigeration is higher when compared to all other investigated refrigerants. Therefore poor COP is obtained for the Refrigerants R134a/R1270 and R419A.

6. Conclusions:

From the thermodynamic performance investigation of various alternative refrigerants, the following conclusions can be drawn.

• The net effect of refrigerating effect and compressor work for the ternary refrigerant mixture composed of R134a/R1270/R290 (50/5/45 by mass percentage) gives the COP (3.608) which is 2.10% higher among the R22, R431A, R410A, R419A, R134a, R1270, R290 and fifteen studied refrigerant mixtures consists of R134a, R1270 and R290. The present study reveals that all the fifteen investigated refrigerant mixtures are mildly flammable.

• The compressor discharge temperature for all the studied refrigerants are lower than the R22 by 4.8oC-22.2oC. If the compressor discharge temperature is lower, then the lifespan of the motor windings increases. Hence it is beneficial from the stand point of life of the compressor motor windings.

• The power consumption per ton of refrigeration for the refrigerant mixture R134a/R1270/R290 (50/5/45 by mass percentage) gives 0.974 kW/TR which is less compared to R22, R431A, R410A, R419A, R134a, R1270, R290 and fifteen studied refrigerant mixtures composed of R134a, R1270 and R290. Thus it indicates the better performance of the system for the mixture R134a/R1270/R290 (50/5/45 by mass percentage).

• Overall, refrigerant mixture R134a/R1270/R290 (50/5/45 by mass percentage) is an ecologically energy efficient alternative refrigerant to substitute R22 among the R431A, R410A, R419A and fifteen studied mixtures from the stand point of COP, GWP, ODP and power consumption per ton of refrigeration.

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