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International Communications in Heat and Mass Transfer 37 (2010) 1340–1349
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International Communications in Heat and Mass Transfer
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A performance comparison of vapour-compression refrigeration system usingvarious alternative refrigerants☆
A.S. Dalkilic a,⁎, S. Wongwises b,⁎a Heat and Thermodynamics Division, Department of Mechanical Engineering, Yildiz Technical University, Yildiz, Besiktas, Istanbul, 34349, Turkeyb Fluid Mechanics, Thermal Engineering and Multiphase Flow Research Lab. (FUTURE), Department of Mechanical Engineering,King Mongkut's University of Technology Thonburi (KMUTT), Bangmod, Bangkok, 10140, Thailand
☆ Communicated by W.J. Minkowycz.⁎ Corresponding authors.
E-mail addresses: [email protected] (A.S. Dalkilic(S. Wongwises).
0735-1933/$ – see front matter © 2010 Published by Edoi:10.1016/j.icheatmasstransfer.2010.07.006
a b s t r a c t
a r t i c l e i n f oAvailable online 3 August 2010
Keywords:RefrigerationAlternative refrigerantsPropaneButaneIsobutaneHydrocarbon mixtureR32R134aR12R22
A theoretical performance study on a traditional vapour-compression refrigeration system with refrigerantmixtures based on HFC134a, HFC152a, HFC32, HC290, HC1270, HC600, and HC600a was done for variousratios and their results are compared with CFC12, CFC22, and HFC134a as possible alternative replacements.In spite of the HC refrigerants' highly flammable characteristics, they are used in many applications, withattention being paid to the safety of the leakage from the system, as other refrigerants in recent years are notrelated with any effect on the depletion of the ozone layer and increase in global warming. Theoreticalresults showed that all of the alternative refrigerants investigated in the analysis have a slightly lowerperformance coefficient (COP) than CFC12, CFC22, and HFC134a for the condensation temperature of 50 °Cand evaporating temperatures ranging between −30 °C and 10 °C. Refrigerant blends of HC290/HC600a (40/60 by wt.%) instead of CFC12 and HC290/HC1270 (20/80 by wt.%) instead of CFC22 are found to bereplacement refrigerants among other alternatives in this paper as a result of the analysis. The effects of themain parameters of performance analysis such as refrigerant type, degree of subcooling, and superheating onthe refrigerating effect, coefficient of performance and volumetric refrigeration capacity are also investigatedfor various evaporating temperatures.
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© 2010 Published by Elsevier Ltd.
1. Introduction
Recently, the ozone depleting potential (ODP) and globalwarming potential (GWP) have become the most importantcriteria in the development of new refrigerants apart from therefrigerant CFCs and HCFCs, both of which have high ODP andGWP, due to the their contribution to ozone layer depletion andglobal warming. In spite of their high GWP, alternatives torefrigerant CFCs and HCFCs such as hydro fluorocarbon (HFC)refrigerants with their zero ODP have been preferred for use inmany industrial and domestic applications intensively for adecade. HFC refrigerants also have suitable specifications such asnon-flammability, stability, and similar vapour pressure to therefrigerant CFCs and HCFCs. The problems of the depletion ofozone layer and increase in global warming caused scientists toinvestigate more environmentally friendly refrigerants than HFCrefrigerants for the protection of the environment such ashydrocarbon (HC) refrigerants of propane, isobutene, n-butane,or hydrocarbon mixtures as working fluids in refrigeration and air-
conditioning systems. Although HC refrigerants have highlyflammable characteristics (A3) according to the standards ofASHRAE as a negative specification, they have not only severalpreferable specifications such as zero ozone depletion potential,very low global warming, non-toxicity, and higher performancethan other refrigerant types but also high miscibility with mineraloil and good accordance with the existing refrigerating systems.They are used in many applications with attention being paid tosafety of the leakage from the system as for other refrigerants inrecent years.
Many investigations have been conducted in the research intosubstitutes for CFC12 and CFC22. Wongwises et al. [1] presented anexperimental study on the application of hydrocarbon mixtures toreplace HFC134a in automotive air conditioners. The hydrocarbonsinvestigated are propane (R290), butane (R600), and isobutane(R600a). The measured data are obtained from an automotive air-conditioning test facility utilizing HFC134a as the refrigerant.Wongwises and Chimres [2] presented an experimental study onthe application of a mixture of propane, butane, and isobutene toreplace HFC134a in a domestic refrigerator. The results showed thata 60%/40% propane/butane mixture was the most appropriatealternative refrigerant. Hammad and Alsaad [3] investigated theperformance of a domestic refrigerator using LPG (24.4% propane,56.4% butane, and 17.2% isobutane), which is available locally in
Nomenclature
atm atmosphereCFCs chlorofluorocarbonsCOP coefficient of performanceGWP global warming potentialh enthalpy, kg kJ−1
hfg latent heat of condensation, kJ kg−1
HCFCs hydro chlorofluorocarbonsHCs hydrocarbonsHFCs hydro fluorocarbonsODP ozone depletion potentialP pressure, MPaRE refrigerating effect, kJ kg−1
SVFR suction vapour flow per kW of refrigeration, L s−1
T temperature, °C or KW isentropic compression work, kNm kg−1
VRC volumetric refrigerating capacity, kJ m−3
Greek symbolsρ density, kg m−3
Subscriptscod condensing/condenserevap evaporating/evaporatorcomp compressor1 evaporator superheat2 compressor superheat3 condenser saturated liquid4 evaporator saturated mixture
Fig. 1. Traditional vapour-compression refrigeration cycle used in the analysis for thecases of (a) non-superheating/subcooling and (b) superheating/subcooling.
1341A.S. Dalkilic, S. Wongwises / International Communications in Heat and Mass Transfer 37 (2010) 1340–1349
many countries, is cheap, and possesses an environmentally friendlynature with no ozone depletion potential (ODP), as an alternativerefrigerant to CFC12. Jung et al. [4] used a propane/isobutane (R290/R600a) mixture to determine their performance for domesticrefrigerators. According to their thermodynamic cycle analysis, thepropane/isobutane blend in the composition range from 0.2 to 0.6mass fraction of propane yields an increase in the coefficient ofperformance (COP) of up to 2.3% compared to CFC12. Granryd [5]mentioned the possibilities and problems of using hydrocarbons asworking fluids in refrigeration equipment. In spite of theirflammability specification, it is shown in his paper that alternativerefrigerants can be obtained by means of hydrocarbons for energyefficient and environmentally friendly refrigerating equipmentand heat pumps. Han et al. [6] studied a new hydrocarbon refri-gerant mixture instead of R407C for vapour-compression refrige-ration systems experimentally. As a result of the experimental andtheoretical analyses, their new ternary non-azeotropic mixture ofR32/R125/R161, whose ODP and GWP are zero and lower thanR407C respectively, showed better refrigerating capacity andcoefficient of performance (COP) than R407C. Park et al. [7] testedtwo pure hydrocarbons and seven mixtures composed ofpropylene, propane, HFC152a, and dimethylether as an alternativeto HCFC22 in residential air-conditioners and heat pumps. Theirexperimental results show that the coefficient of performance(COP) of these mixtures is up to 5.7% higher than that ofHCFC22. Mani and Selladurai [8] performed experiments using avapour-compression refrigeration system with the new R290/R600a refrigerant mixture as a substitute refrigerant for CFC12 andHFC134a. According to the results of their experiments, therefrigerant R290/R600a had a refrigerating capacity 19.9% to50.1% higher than that of R12 and 28.6% to 87.2% than that ofR134a. The R290/R600a blend's performance coefficient (COP) is
improved by 3.9–25.1% compared to that of R12 at lower eva-porating temperatures and by 11.8–17.6% at higher evaporatingtemperatures. The refrigerant R134a had a slightly lower coef-ficient of performance (COP) than R12. Chen and Yu [9] presented anew refrigeration cycle, introduced as an alternative refrigerationcycle applied in residential air-conditioners, using the binary non-azeotropic refrigerant mixture R32/R134a. As a result of the com-parison between the conventional cycle configuration and the newone, the coefficient of performance (COP) increases by 8% to 9%compared to the conventional cycle configuration, and the volu-metric refrigerating capacity is increased by approximately 9.5%.
In this paper, a vapour-compression refrigeration cycle for binarynon-azeotropic mixed refrigerants is used in order to obtain betterperformance. The present study mostly concentrates on a theoreticalinvestigation of the performance of the vapour-compression refrigera-tion cycle. The binary non-azeotropic mixtures R-290/R-600, R-290/R-600a, R-290/R-1270, R-290/R-152a, and R-32/R-134a in variousconcentrations such as R-290/R-600(50/50), R-290/R-600(60/40), R-290/R-600(70/30), R-290/R-600(80/20), R-290/R-600a(40/60), R-290/R-600a(50/50), R-290/R-600a(60/40), R-290/R-600a(70/30), R-290/R-1270(20/80), R-290/R-1270(50/50), R-290/R-1270(60/40), R-290/R-1270(80/20), R-290/R-152a(60/40), R-290/R-152a(70/30), R-290/R-152a(80/20), and R-32/R-134a(30/70) are used as the working fluidfor the comparison with the conventional refrigerants R12, R134a, andR22. The effects of themain parameters of performance analysis such as
1342 A.S. Dalkilic, S. Wongwises / International Communications in Heat and Mass Transfer 37 (2010) 1340–1349
refrigerant type and degree of subcooling and superheating on therefrigerating effect (RE), coefficient of performance (COP) and volu-metric refrigeration capacity (VRC) are investigated for variousevaporating temperatures ranging between −30 and 5 °C and aconstant condensation temperature of 50 °C.
Fig. 2. Evaporating pressure (a, b, c) and pressur
2. Caculation method
The pressure–enthalpy diagram prepared for theoretical datafor two different cases is shown in Fig. 1. The ideal refrigerationcycle in Fig. 1 is considered for the working substances that
e ratio (d, e, f) vs evaporating temperature.
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change phase during the cycle. It is known that the actualrefrigeration cycle systems have some deviations from the idealone due to pressure losses of fluid flow and heat transfer exchangebetween the surroundings. The superheated state of vapour existsat the inlet part of the compressor as shown in Fig. 1b, thepressure of the liquid at the exit part of the condenser is lowerthan the pressure at the inlet part of it, there is a pressure dropgreater than the ideal one between the condenser and expansion
Fig. 3. Refrigerating effect (a, b, c) and isentropic comp
valve, and also a larger pressure drop occurs on the evaporationline.
Cycle performance determination is performed to ease the theoret-ical calculations by means of some assumptions as follows: neglect ofthe pressure drops and the heat losses to the environment from thedevices of evaporators, recuperators, subcooler, phase separator andcondensers; saturated vapour at the low boiling point stream (vapourphase) from the separator and saturated liquid at the high boiling point
ression work (d, e, f) vs evaporating temperature.
Fig. 4. Coefficient of performance (a, b, c) vs evaporating temperature.
1344 A.S. Dalkilic, S. Wongwises / International Communications in Heat and Mass Transfer 37 (2010) 1340–1349
stream (liquid phase) from the separator in Fig. 1a; the isenthalpic flowacross the expansion valves; and the considered isentropic efficiency forthe compressor. When the thermodynamic properties of each state ofthe cycle are determined, the equations for the cycle analysis can beobtained bymeans ofmass and energy conservation. The data reductionof the theoretical results can be analysed below.
The pressure ratio of the cycle can be seen below as follows:
Thepressureratio = Pcod = Pevap: ð1Þ
Isentropic compression work of the compressor (Wcomp) isexpressed as follows:
Wcomp = h2−h1: ð2Þ
The refrigerating effect (RE), in other words, the heat transfer rateof the evaporator (Qevap), is calculated as follows:
RE = Qevap = h1−h4: ð3Þ
Power per ton of refrigeration is calculated as follows:
Powerper tonof refrigeration P = TRð Þ = 3:5Wcomp = RE: ð4Þ
In the vapour-compression system in Fig. 1, volumetric refriger-ating capacity (VRC) is given as:
VRC = ρ1⋅RE: ð5Þ
Suction vapour flow per kW of refrigeration can be determined as:
SVFR = 1= ρ1⋅REð Þ: ð6Þ
The coefficient of performance (COP) of the refrigeration system'scycle can be determined by:
COP = RE =Wcomp: ð7Þ
3. Results and discussion
The dependency on the composition of refrigerant mixturesmakesthe pressure–temperature relationship in the cycle significant forcondensers and evaporators. Cycle performance is affected by thepressure alterations while the ratios of the blend vary at the giventemperature. For that reason, the proportion of the components in themixture is one of the significant factors in the cycle. For comparison ofthe theoretical data, R12 and R22 are chosen in this paper as referencefluids due to their common usage in cooling systems and prohibitionby the Montreal Protocol.
The analysis of the variation of physical properties of pure andblend refrigerants such as evaporation pressure (Pevap), pressureratio, isentropic compression work (W), refrigerating effect (RE),power per ton of refrigeration, volumetric refrigeration capacity(VRC), suction vapor flow rate (SVFR) and coefficient of perfor-mance (COP) is investigated in this theoretical study, and they areplotted against the evaporating temperature (Tevap) as shown inFigs. 2-6c for the ideal refrigeration cycle in Fig. 1a, and inFigs. 6d-9b for comparison of the superheating/subcooling case inFig. 1b with the non-superheating/subcooling case in Fig. 1a.Considering the evaporation and condensation temperatures ofstudies in the literature, the example case studies in Tables 1 and 2as shown in Stoecker and Jones [10] are shown for thedetermination of mixed alternative refrigerants for the traditionalpure refrigerants R12 and R22 respectively. Tables 3 and 4 showsdeviations of alternative refrigerants from the values of R12 andR22 numerically.
The changes in evaporation pressure (Pevap) and pressure ratiowith the evaporation temperature (Tevap) are shown in Fig. 2 forlisted refrigerant mixtures with different proportions as follows:R-290/R-600a vs R-12 vs R-134a (Fig. 2a), R-290/R-1270 vs R-22(Fig. 2b), and R22 vs R290/152a vs R290/R1270 vs R32 vs R134a(Fig. 2c). The nearest pressure ratio of substitute refrigerant tobase one belongs to R290/R600a (70/30 by wt.%), whose pressureratio is 1.63% higher than that of R12 and R290/R152a (60/40 bywt.%), whose pressure ratio is 7.21% lower than that of R22 asshown in Tables 3 and 4 for the constant condensation andevaporation temperatures of 50 °C and −10 °C respectively. Inaddition to this, R290/R600 (50/50 by wt.%) and R32/R134a (30/70by wt.%) give the highest ratios as substitutes for R12 and R22respectively according to the same table. It can be seen from
Fig. 5. Power per ton of refrigeration (a, b, c) and volumetric refrigerating capacity (d, e, f) vs evaporating temperature.
1345A.S. Dalkilic, S. Wongwises / International Communications in Heat and Mass Transfer 37 (2010) 1340–1349
Fig. 2a and c that the saturated vapour pressures for R290/R600a(70/30 by wt.%) and R290/R152a (60/40 by wt.%) are closer thanothers to the vapour pressure curve of the refrigerants R12 andR22 respectively.
In Tables 1 and 2, significant parameters of cycle performanceunder different conditions are calculated as case studies of R12 andR22 respectively for the same condensing and evaporation tempera-tures obtained from the literature review. In addition to this, it can beseen that the evaluation of cycle performance results under differentworking conditions agrees with those under real working conditions.
Fig. 3 shows that the refrigerating effect (RE) increases withincreasing evaporation temperature (Tevap) while the compressorpower (Wcomp) decreases with increasing Tevap for the constantcondensation temperature of 50 °C and the evaporation temperaturesranging from −30 °C to 5 °C. Apart from the mixture of R290/R600a(50/50 by wt.%) and R32/R134a (30/70 by wt.%), other testedalternative refrigerants have much higher refrigerating effects thanthose of R12 and R22 in Fig. 3a, b, c respectively. All of the testedrefrigerants at various concentrations apart from R134a and R32/R134a (30/70 by wt.%) have much higher values of isentropic
Fig. 6. Suction vapour flow rate (a, b, c) and refrigerating effect (d, e) vs evaporating temperature.
1346 A.S. Dalkilic, S. Wongwises / International Communications in Heat and Mass Transfer 37 (2010) 1340–1349
compression work than R12 and R22 respectively in Fig. 3d, e, f and asshown in Tables 3 and 4.
The variation of performance coefficient (COP) with evapora-tion temperature (Tevap) is illustrated in Fig. 4a, b, c. From thisfigure, the coefficient of performance (COP) increases as theevaporation temperature (Tevap) increases for the constantcondensation temperature of 50 °C and evaporation temperaturesranging from −30 °C to 5 °C, and this alteration also can beunderstood from Eq. (4), considering an increase in refrigeratingeffect (RE) and a decrease in compressor power (Wcomp) for thecase. The decrease in pressure ratio for the compressor alsoimproves the efficiency. All the performance coefficients (COP) ofthe alternative refrigerants tested are found to be lower than
those of R12 and R22 for the simulation conditions. In addition tothis, the coefficient of performance (COP) has some alterationswith the decrease or increase in the components' ratios in thecomposition due to the changes in the thermodynamic physicalproperties of the refrigerant mixture as the composition of themixture varies.
The changes in power needed for refrigeration with evaporationtemperature (Tevap) in Fig. 5a, b, c, volumetric refrigeration capacity(VRC) with evaporation temperature (Tev) in Fig. 5d, e, f, andsuction vapour flow needed for refrigeration (SVFR) with evapo-ration temperature (Tevap) in Fig. 6a, b, c are shown in order toverify the cycle performance advantages of alternative refrigerants.The specific volume of the suction vapour decreases, causing the
Table 1Operation on a standard vapor-compression cycle using R12 and various refrigerants at Tcod=50 °C and Tevap=–10 °C.
Refrigerant Pevap Pcod Pressure ratio Wcomp RE Power per ton refrigeration VRC SVFR COP
(by wt.%) (MPa) (MPa) (kJ kg–1) (kJ kg–1) (kW TR–1) (kJ m–3) (L s–1)
R-12 0.219 1.217 5.562 30.500 98.600 1.083 1273.912 0.785 3.233R-134a 0.201 1.318 6.570 39.100 121.100 1.130 1215.844 0.822 3.09720%R600+80%R290 0.213 1.268 5.953 83.800 234.500 1.251 1120.676 0.892 2.79830%R600+70%R290 0.176 1.102 6.261 84.900 237.700 1.250 959.357 1.042 2.80040%R600+60%R290 0.149 0.965 6.492 85.000 240.200 1.239 836.376 1.195 2.82650%R600+50%R290 0.128 0.852 6.668 84.000 242.400 1.213 742.229 1.347 2.88630%R600a+70%R290 0.225 1.270 5.654 78.200 226.200 1.210 1180.764 0.846 2.89340%R600a+60%R290 0.199 1.155 5.807 77.700 225.900 1.204 1066.248 0.937 2.90750%R600a+50%R290 0.177 1.053 5.936 77.100 225.200 1.198 969.936 1.031 2.92160%R600a+40%R290 0.225 1.270 5.654 78.200 226.200 1.210 1180.764 0.846 2.893
Table 2Operation on a standard vapor-compression cycle using R22 and various refrigerants at Tcod=50 °C and Tevap=–10 °C.
Refrigerant Pevap Pcod Pressure ratio Wcomp RE Power per ton refrigeration VRC SVFR COP
(by wt.%) (Mpa) (Mpa) (kJ kg–1) (kJ kg–1) (kW TR–1) (kJ m–3) (L s–1)
R-22 0.355 1.943 5.476 43.400 138.000 1.101 1273.912 0.473 3.18080%R1270+20%R290 0.426 2.039 4.789 76.200 228.400 1.168 1215.844 0.478 2.99750%R1270+50%R290 0.406 1.958 4.829 75.500 223.400 1.183 1120.676 0.506 2.95940%R1270+60%R290 0.395 1.918 4.853 75.200 222.900 1.181 959.357 0.519 2.96420%R1270+80%R290 0.371 1.822 4.908 75.000 223.200 1.176 836.376 0.549 2.97640%R152a+60%R290 0.362 1.850 5.108 65.800 195.300 1.179 742.229 0.549 2.96830%R152a+70%R290 0.366 1.835 5.019 67.700 201.300 1.177 1180.764 0.587 2.97320%R152a+80%R290 0.362 1.815 5.025 70.000 197.400 1.241 1066.248 0.587 2.82070%R134a+30%R32 0.293 1.851 6.328 50.600 149.500 1.185 969.936 0.580 2.955
1347A.S. Dalkilic, S. Wongwises / International Communications in Heat and Mass Transfer 37 (2010) 1340–1349
increase in the mass flow rate as the evaporation temperature(Tevap) increases. The effects of changed concentrations on theperformance parameters can be seen from these figures and alsofrom Tables 1–4. The volumetric cooling effect, in other words, thevolumetric capacity, is defined as the cooling capacity per unit ofvapour volume at the exit of the evaporator. A high cooling capacitycan be obtained from a high volumetric capacity refrigerant for agiven swept volume in the compressor.
The cycle performance can be improved by the subcooling andsuperheating application. In this paper, the effects of the degree ofsubcooling and superheating are calculated respectively. Thecomparison of the superheating/subcooling case in Fig. 1b with
Table 3Some deviation values of alternative refrigerants from R12.
R12 at Tcod=50 °C and Tevap=–10 °C
Refrigerant Pressure ratio % Wcomp % RE %
R-134a 6.57 21.73 18.5750%R600+50%R290 16.58 63.69 59.3230%R600a+70%R290 1.63 60.86 56.4140%R600a+60%R290 4.21 60.61 56.3550%R600a+50%R290 6.29 60.31 56.2160%R600a+40%R290 7.99 59.81 56.04
Table 4Some deviation values of alternative refrigerants from R22.
R22 at Tcod=50 °C and Tevap=–10 °C
Refrigerant Pressure ratio % Wcomp % RE %
80%R1270+20%R290 –14.36 43.04 39.5740%R152a+60%R290 –7.21 34.04 29.3330%R152a+70%R290 –9.1 35.89 31.4420%R152a+80%R290 –8.98 38 30.0970%R134a+30%R32 13.46 14.22 7.69
the non-superheating/subcooling case in Fig. 1a is illustrated inFig. 6d, e and Figs. 7-9 for the blend refrigerants of R-290/R-600a(40/60 by wt.%) and R-290/R-1270 (20/80 by wt.%). It should benoted that the characteristics of trend lines belonging to eachrefrigerant are similar to those from Figs. 2a-6c and the perfor-mance coefficient (COP) values of the superheating/subcoolingcase are found to be higher than those of the non-superheating/subcooling case. The reason for the improvement is the increase inthe compressor inlet temperature, and thus the increases in therefrigerating effect and volumetric refrigerating capacity.
The thermo-physical properties, restrictions related to safety,environmental impact, and associated legislation are the most
Power per ton refrigeration % VRC % SVFR % COP %
3.88 –4.77 4.55 –4.0310.73 –71.63 41.73 –12.0210.23 –7.88 7.31 –11.399.77 –19.47 16.3 –10.839.35 –31.33 23.86 –10.318.58 –43.38 30.25 -9.39
Power per ton refrigeration % VRC % SVFR % COP %
5.73 –0.95 0.94 –6.086.65 –16.01 13.8 –7.136.48 –16.25 13.99 –6.93
11.31 –24.13 19.44 –12.757.08 –22.64 72.4 –7.62
Fig. 7. Isentropic compression work (a, b) and coefficient of performance (c, d) vs evaporating temperature.
Fig. 8. Power per ton of refrigeration (a, b) vs evaporating temperature.
1348 A.S. Dalkilic, S. Wongwises / International Communications in Heat and Mass Transfer 37 (2010) 1340–1349
significant factors in choosing a new refrigerant. Low viscosities ofliquid and vapour phases, high liquid specific heat, high thermalconductivities of liquid and vapour phases, high latent heat, andsmall temperature glide are the desired thermo-physical proper-ties of refrigerant mixtures in the literature. As a result of theanalysis in this paper, HC290/HC600a (40/60 by wt.%) instead ofR12 and HC290/HC1270 (20/80 by wt.%) instead of R22 seem to bethe best alternative refrigerants in terms of the factors in choosinga new refrigerant.
4. Conclusions
In this study, an ideal vapour-compression refrigeration systemis used for the performance analysis of alternative new refrigerantmixtures as substitutes for CFC12, HFC134a, and CFC22. Consid-ering the comparison of performance coefficients (COP) andpressure ratios of the tested refrigerants and also the mainenvironmental impacts of ozone layer depletion and globalwarming, refrigerant blends of HC290/HC600a (40/60 by wt.%)and HC290/HC1270 (20/80 by wt.%) are found to be the mostsuitable alternatives among refrigerants tested for R12 and R22respectively. The refrigeration efficiency, the performance coeffi-cient (COP) of the system, increases with increasing evaporatingtemperature for a constant condensing temperature in theanalysis. All systems including various refrigerant blends wereimproved by analysing the effect of the superheating/subcoolingcase. Better performance coefficient values (COP) than those of thenon-superheating/subcooling case are obtained as a result of thisoptimization.
Fig. 9. Volumetric refrigerating (a, b) and suction vapour flow rate (c, d) vs evaporating temperature.
1349A.S. Dalkilic, S. Wongwises / International Communications in Heat and Mass Transfer 37 (2010) 1340–1349
Acknowledgements
The authors are indebted to King Mongkut's University ofTechnology Thonburi (KMUTT), the Thailand Research Fund, theOffice of the Higher Education Commission and the National ResearchUniversity Project for supporting this study. Especially, the first authorwishes to thank KMUTT for providing him with a Post-doctoralfellowship.
References
[1] S. Wongwises, A. Kamboon, B. Orachon, Experimental investigation of hydrocar-bon mixtures to replace HFC-134a in an automotive air conditioning system,Energy Conversion and Management 47 (2006) 1644–1659.
[2] S. Wongwises, N. Chimres, Experimental study of hydrocarbon mixtures toreplace HFC-134a in a domestic refrigerator, Energy Conversion and Management46 (2005) 85–100.
[3] M.A. Hammad, M.A. Alsaad, The use of hydrocarbon mixtures as refrigerants indomestic refrigerators, Applied Thermal Engineering 19 (1999) 1181–1189.
[4] D. Jung, C.B. Kim, B.H. Lim, H.W. Lee, Testing of a hydrocarbonmixture in domesticrefrigerators, ASHRAE Transactions 3 (1996) 1077–1084.
[5] E. Granryd, Hydrocarbons—an overview, International Journal of Refrigeration 24(2001) 15–24.
[6] X.H. Han, Q. Wang, Z.W. Zhu, G.M. Chen, Cycle performance study on R-32/R-125/R-161 as alternative refrigerant to R-407C, Applied Thermal Engineering 27(2007) 2559–2565.
[7] K.J. Park, T. Seo, D. Jung, Performance of alternative refrigerants for residential air-conditioning applications, Applied Energy 84 (2007) 985–991.
[8] K. Mani, V. Selladurai, Experimental analysis of a new refrigerant mixture as drop-in replacement for CFC12 and HFC134a, International Journal of Thermal Sciences47 (2008) 1490–1495.
[9] J. Chen, J. Yu, Performance of new refrigerant cycle using refrigerant mixture R32/R134a for residential air-conditioner applications, Energy and Buildings 40 (2008)2022–2027.
[10] W.F. Stoecker, J.W. Jones, Refrigeration and Air Conditioning, second ed.,McGraw-Hill, 1982, pp. 298–299.
