Thermodynamic Performance Assessment Of R32 And R1234yf -Books Pdf

Thermodynamic Performance Assessment of R32 and R1234yf
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Zheng et al 12th IEA Heat Pump Conference 2017 O 4 1 2. 1 Introduction, According to the amendment for Montreal Protocol on Substances that Deplete the Ozone Layer the use of. HFCs will be reduced gradually from as early as 2019 to prevent the global temperature from increasing 0 5. degrees Celsius by the end of the century HFC 410A R410A as one of the most widely used HFCs to replace. HCFC 22 R22 in household air conditioners is now facing the challenge of being phased down due to its high. GWP value ca 2 088 Therefore it requires researchers to search for alternatives of R410A to protect the. environment In recent years refrigerant HFO 1234yf R1234yf with a GWP as low as 4 is considered. However since R1234yf has much smaller latent heat than R410A the coefficient of performance COP of a. heat pump system would be decreased if R1234yf were to be substituted directly To maintain a R410A system. performance some researchers proposed to use refrigerant mixtures of R1234yf and other fluids with large latent. heat such as HFC32 R32 Fujitaka et al 1 conducted experiments to compare the system performances of. R32 R1234yf mixtures to that of R410A in a room air conditioner Results indicated that the system. performance of the mixture improved as the mass fraction of R32 was increased Okazaki et al 2 tested. R32 R1234yf in a modified room air conditioner and pointed out that the modified unit with mixture having a. 60 R32 mass fraction could reach 93 3 of the annual performance factor APF of R410A In addition. studies were conducted on the vapor liquid equilibrium 3 dynamic viscosity 4 flow boiling heat transfer. coefficient 5 and compressor operating characteristics 6 of the R32 R1234yf mixture with certain mixing. ratio In order to achieve both a low GWP and high system performance the mixing ratio of the R32 R1234yf. mixture should be carefully determined In this paper the basic properties and theoretical cycle performance of. the mixture with various R32 mass fractions were compared with those of R410A under both heating and. cooling conditions The optimal mixing ratios of the mixture considering the trade off between GWP and COP. based on different working conditions were obtained. 2 Comparison of Properties,2 1 Property comparison of Pure Refrigerants. Table 1 shows the comparison of some selected properties of R410A R32 and R1234yf The basic. thermodynamic properties of each refrigerant were obtained from REFPEOP 7 and the information about. safety class ODP and GWP was originated from previous publications 5 8 Table 1 shows that the ODP value. of these refrigerants are all zero R32 showing the largest latent heat has similar critical temperature and boiling. point as those of R410A and its GWP value is reduced by about two third compared to that of R410A R1234yf. has the lowest GWP and latent heat among the three fluids. Table 1 Comparison of properties of three refrigerants. Properties R410A R32 R1234yf,M g mol 72 585 50 024 114 04. Tnb C 51 40 51 651 29 45,Tcrit C 71 35 78 105 94 700. Pcrit bar 49 019 57 82 33 822,Hlv 15 C kJ kg 238 54 337 28 172 37.
Hlv 45 C kJ kg 148 27 223 99 127 37,Safety Class A1 A2L A2L. GWP 2 088 675 4, Fig 1 shows the comparison of the three refrigerants on a temperature entropy T s diagram It can be seen. clearly from the figure that the difference in latent heat between R1234yf and other two refrigerants increases. gradually as the saturation temperature decreases As shown in the figure the saturation vapour curve of. R1234yf exhibits a negative slope while R410A and R32 have positive saturation vapour curve slope. According to the previous study 9 R1234yf is regarded as wet refrigerant and the other two refrigerants are as. dry refrigerants Mixing of R32 and R1234yf could lead to isentropic mixtures. Zheng et al 12th IEA Heat Pump Conference 2017 O 4 1 2. Fig 2 shows the comparison of the flow boiling heat transfer coefficients of R410A R32 and R1234yf based. on the experimental results published by Longo et al 10 and Li et al 5 All of the experimental data were. obtained under same mass velocity 400 kg m2 s and heat flux 12 kW m2 conditions As shown in Fig 2 R32. exhibits slightly higher heat transfer coefficient than that of R410A under the same conditions and the difference. in the heat transfer coefficient becomes larger as the vapour quality increases When the tube diameter is 2 mm. and saturation temperature is 15 C R1234yf shows much lower heat transfer coefficient than that of R32 within. the entire variation range of vapor quality,0 4 0 6 0 8 1 0 1 2 1 4 1 6 1 8 2 0. Fig 1 T s diagram of three refrigerants,R1234yf d 2 mm Tsat 15 C. Heat Transfer Coefficient kW m2k,R32 d 2 mm Tsat 15 C.
15 R32 d 4 mm Tsat 10 C,R32 d 4 mm Tsat 20 C,R410A d 4 mm Tsat 10 C. R410A d 4 mm Tsat 20 C,0 0 0 2 0 4 0 6 0 8 1 0,Vapor Quality. Fig 2 Flow boiling heat transfer coefficients of R410A R32 and R1234yf G 400 kg m2 s and q 12 kW m2. 2 2 Properties of R32 R1234yf mixtures, The mixing of R32 and R1234yf results in zeotropic mixtures since each component fluid has a different. boiling point For zeotropic mixtures the saturation temperature changes during the phase change process The. temperature difference between the saturated liquid and vapor points at a constant pressure is defined as the. temperature glide Fig 3 shows the variation of the temperature glides of R32 R1234yf mixture with R32 mass. fraction under two pressures at which the average saturation temperatures are 15 C and 45 C According to the. calculation results when the R32 mass fraction is about 0 15 the maximum temperature glides of the mixture is. 9 8 C for lower pressure and 7 9 C for higher pressure The variation of GWP value versus R32 mass fraction in. mixture is also illustrated in Fig 3 For simplicity the GWP of the mixture is estimated based on the linear. weighted sum method hence a higher R32 mass fraction will lead to a larger GWP value for the mixture In this. paper the upper limit of the GWP value is set to 150 as an example since refrigerants with GWP above that. value are banned from use in mobile air conditioners in EU market from 2011 As shown in Fig 3 the GWP of. the mixture reaches to the upper limit as R32 mass fraction increases to about 0 218. Zheng et al 12th IEA Heat Pump Conference 2017 O 4 1 2. According to the test data 5 the variation of boiling heat transfer coefficient by the R32 mass fraction. change is not linear for the R32 R1234yf mixture As shown in Fig 4 the boiling heat transfer coefficient first. decreases and then increases as the mixture becomes rich in R32 component and reaches to the minimum value. around R32 mass fraction of 0 2 The decrease in heat transfer coefficient could be related to the non linear. variation in the thermophysical properties of the zeotropic mixture caused by the interactions between blend. components, Fig 5 shows the variation of the liquid viscosity and latent heat versus R32 mass fraction for R32 R1234yf. mixtures at two different saturation temperatures The latent heat of the mixture increases gradually with an. increasing R32 mass fraction The dynamic viscosity of the saturated liquid of R1234yf is higher than that of. R32 For R32 R1234yf mixtures the saturated liquid viscosity decreases obviously with an increasing R32 mass. fraction but the variation curve begins to be flat as the R32 mass fraction approaching to unit value Lower. viscosity of the liquid corresponds to smaller friction in liquid pipelines contributing to a smaller pressure drop. Temperature glide 15 C,Temperature glide 45 C,Temperature Glide K.
GWP 100 year,GWP 150 200,xR32 0 218,0 0 0 2 0 4 0 6 0 8 1 0. Mass Fraction of R32, Fig 3 Temperature glide and GWP of R32 R1234yf mixtures. Heat Transfer Coefficient kW m2K,7 G 200 kg m2s,q 12 kW m2. 6 Tsat 15 C,0 0 0 2 0 4 0 6 0 8 1 0,Mass Fraction of R32. Fig 4 Boiling Heat transfer coefficient of mixture R32 R1234yf at different R32 mass fractions. Zheng et al 12th IEA Heat Pump Conference 2017 O 4 1 2. Viscosity 15 C,240 Viscosity 45 C,Latent Heat 15 C.
Latent Heat 45 C,Liquid Viscosity pas,Latent Heat kJ kg. 0 0 0 2 0 4 0 6 0 8 1 0,Mass Fraction of R32, Fig 5 Saturated liquid viscosity and latent heat of R32 R1234yf mixtures. 3 Thermodynamic cycle model, A steady state thermodynamic model of a single stage refrigeration cycle was established to evaluate the cycle. performance of different refrigerants based on the following assumptions. Constant pressure during phase change process,Constant compressor isentropic efficiency of 0 75. Isenthalpic throttling process, No superheating at evaporator outlet and no subcooling at condenser outlet.
Fixed mass flow rate with unit value, The evaporating and condensing temperatures are fixed values for pure fluid and azeotropic mixture R410A. For R32 R1234yf mixtures the condensing and evaporating temperatures were set to be the average values of. bubble point and dew point under condensing and evaporating pressures The calculation of the cycle. performance for each refrigerant was carried out by a Matlab program and the required refrigerant properties. were determined using REFPROP 9 0 7,4 Results and Discussion. In this section the cycle performance of an air conditioning heat pump system operating with R32 R1234yf. mixture is compared with that of R410A under both cooling mode and heating mode conditions For cooling. mode the evaporating and condensing temperatures were fixed at 10 C and 45 C respectively and for heat. pumping mode the evaporating and condensing temperatures were set as 15 C and 35 C respectively as shown. in Table 2,Table 2 Temperature conditions,Evaporation T C Condensation T C. Cooling Mode 10 45,Heating Mode 15 35, Fig 6 a shows the variation trend of condensing pressure versus R32 mass fraction for t he R32 R1234yf. mixtures Since R32 has a much lower boiling point than R1234yf the condensing pressure is expected to. increase with an increasing R32 mass fraction The condensing pressure of R410A under each mode is also. illustrated in the diagram for comparison It can be seen that the condensing pressure of R32 R1234yf mixture. begin to surpass that of R410A as the R32 mass fraction reaches to about 0 9 for the two modes When the R32. Zheng et al 12th IEA Heat Pump Conference 2017 O 4 1 2. mass fraction is 0 218 the condensing pressures of the mixture in cooling and heating modes are reduced by. 910 3 kPa and 715 6 kPa respectively as compared to those of R410A. Discharge Temperature C,Condensing Pressure kPa,R410A cooling mode R410A cooling mode.
1000 R410A heating mode R410A heating mode, R32 R1234yf cooling mode 40 R32 R1234yf cooling mode. R32 R1234yf heating mode R32 R1234yf heating mode,0 0 0 2 0 4 0 6 0 8 1 0 0 0 0 2 0 4 0 6 0 8 1 0. Mass Fraction of R32 Mass Fraction of R32, Fig 6 Variation of condensing pressure a and discharge temperature b for R32 R1234yf mixture. Fig 6 b shows the effect of R32 mass fraction on the discharge temperature Overall the discharge. temperature increases with an increasing R32 mass fraction When the R32 mass fraction is less than 0 35 the. discharge temperature of cooling mode is higher than that of heating mode though the cooling mode shows. smaller cycle temperature lift 35 K than heating mode 50 K The variation of the slope of the saturated vapor. curve may lead to this phenomenon Figure 6 b also indicates that the R32 R1234yf mixture will show higher. discharge temperature than R410A as the R32 mass fraction reaches to about 0 55 for both heating and cooling. modes For R32 R1234yf mixture with a 0 218 R32 mass fraction the discharge temperature is reduced by 7 3 C. in cooling mode and 13 2 C in heating mode as compared to that of R410A. Fig 7 shows the changes of cooling and heating capacities versus R32 mass fraction for cooling mode and. heating mode respectively As expected both the heating and cooling capacities increase with an increasing R32. mass fraction For cooling mode the cooling capacity of R32 R1234yf mixture becomes larger than that of. R410A as the R32 mass fraction reaches to 0 45 For heating mode the heating capacity of the zeotropic mixture. becomes superior to that of R410A as the R32 mass fraction increases to about 0 5 For R32 R1234yf mixture. with an R32 mass fraction of 0 218 the cooling capacity and heating capacity is reduced by 13 5 and 17 6. respectively as compared to that of R410A under the same condition. R32 R1234yf Qevap,Cooling Heating Capacity kW,R32 R1234yf Qcond. 300 R410A Qevap,R410A Qcond,0 0 0 2 0 4 0 6 0 8 1 0.
Mass Fraction of R32, Fig 7 Variation of cooling and heating capacities of R32 R1234yf. Zheng et al 12th IEA Heat Pump Conference 2017 O 4 1 2. 3 94 R32 R1234yf,R32 R1234yf 4 75,3 92 R410A,Cooling COP. Heating COP,0 0 0 2 0 4 0 6 0 8 1 0 0 0 0 2 0 4 0 6 0 8 1 0. Mass Fraction of R32 Mass Fraction of R32, Fig 8 Variations of heating and cooling COPs of R32 R1234yf. Fig 8 a shows the variation of heating COP versus R32 mass fraction for R32 R1234yf mixture under. heating mode The heating COPs of R1234yf and R32 are 3 82 and 3 95 respectively The heating COP of the. R32 R1234yf shows an increase tendency with R32 mass fraction in general The heating COP of the mixtures is. less than that of R410A 3 85 before the R32 mass fraction reaching to 0 45 Fig 8 b shows the comparison of. cooling COP between R410A and R32 R1234yf mixture with varying mixing ratio As shown in the figure the. cooling COP of the mixture first decreases and then increases with an increasing R32 mass fraction The. minimum COP value of 4 56 is reached when the R32 mass fraction increases to 0 35 Fig 8 b also shows that. when the evaporating and condensing temperatures are 10 C and 45 C respectively both R32 and R1234yf. show higher cooling COP than R410A When mixture R32 R1234yf with an R32 mass fraction of 0 218 is. applied the heating COP is reduced by 0 4 but the cooling COP is increased by 1 5 as compared to that of. 5 Conclusions, The following conclusions can be drawn from this work.
Lower R32 mass fraction in the R32 R1234yf mixture leads to the decrease in condensing pressure and. discharge temperature but the reduction in cooling heating capacity so that the compressor displacement volume. should be increased, When R32 mass fraction is 0 218 the GWP of the mixture R32 R1234yf reaches to 150 which is reduced by. 92 8 compared to that of R410A While the cooling and heating capacities of mixture are reduced by 13 5. and 17 6 respectively as compared to that of R410A under the same conditions the heating and cooling COPs of. the mixture R32 R1234yf with an R32 mass fraction of 0 218 is comparable to that of R410A respectively. Either higher R32 mass fraction in R32 R1234yf or pure R32 would be the choice while considering the heat. transfer and COP perspectives but it requires relaxing of GWP value. Therefore the life cycle climate performance evaluation would help in determining the proper GWP value. without compromising the environmental impact,Acknowledgements. This work is sponsored by the National Nature Science Foundation of China 51476110 The support of the. Center for Environmental Energy Engineering CEEE at the University of Maryland and the China Scholarship. Council CSC are gratefully acknowledged, Zheng et al 12th IEA Heat Pump Conference 2017 O 4 1 2. References, 1 Fujitaka A Shimizu T Sato S Kawabe Y 2010 Application of low global warming potential. refrigerants for room air conditioner 2010 International Symposium on Next generation Air Conditioning. and Refrigeration Technology Tokyo Japan NS 25, 2 Okazaki T Maeyama H Saito M Yamamoto T 2010 Performance and reliability evaluation of a.
room air conditioner with low GWP refrigerant 2010 International Symposium on Next generation Air. Conditioning and Refrigeration Technology Tokyo Japan NS 27. 3 Arakawa Y Kim S Kamiaka T Dang C Hihara E 2010 Thermophysical properties measurement of. HFO 1234yf R32 mixture 2010 International Symposium on Next generation Air Conditioning and. Refrigeration Technology Tokyo Japan NS 22, 4 Dang Y Kim HS Dang C Hihara E Measurement of vapor viscosity of R1234yf and its binary mixtures. with R32 R125 Int J Refrig 2015 58 131 6, 5 Li M Dang C Hihara E Flow boiling heat transfer of HFO1234yf and R32 refrigerant mixtures in a smooth. horizontal tube Part I Experimental investigation Int J Heat Mass Tran 2012 55 3437 46. 6 Cremaschi L Wu X Biswas A Deokar P 2013 Experimental study of compressor operating. characteristics and performance when using refrigerants R 32 R1234yf and two new low GWP. developmental refrigerants as drop in replacements for R 410A 2013 International Conference On. Compressors And Their Systems London UK, 7 Lemmon E Huber M McLinden M NIST Standard Reference Database 23 Reference Fluid. Thermodynamic and Transport Properties REFPROP Version 9 0 National Institute of Standards and. Technology Standard Reference Data Program 2010, 8 Tian Q Cai D Ren L Tang W Xie Y He G Liu F An experimental investigation of refrigerant mixture. R32 R290 as drop in replacement for HFC410A in household air conditioners Int J Refrig 2015 57 216 28. 9 Zheng N Hwang Y Zhao L Radermacher R 2016 Isentropic mixture and their application in heat. pump in cold climate region 16th International Refrigeration and Air Conditionging Conference at Purdue. West Lafayette USA 2387, 10 Longo GA Mancin S Righetti G Zilio C HFC32 and HFC410A flow boiling inside a 4 mm horizontal.


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