Energy and exergy performance comparison of different HFC/R1234yf mixtures in vapor-compression cycles

To increase the COP and volumetric capacity of hydrofluoroolefins while reducing the global warming potential (GWP) of hydrofluorocarbons (HFCs), four HFC/R1234yf mixtures with various compositions are compared with verified thermodynamic models. Results show that a lower R1234yf mass fraction leads to a higher mixture latent heat; R32/R1234yf has the highest pressures, the lowest pressure ratios and the biggest temperature glides. As the R1234yf mass fraction increases from 0.0 to 1.0, the cooling coefficient of performance (COP) first increases from 5.25 to 5.52 and later decreases to 5.30 for R32/R1234yf, while it decreases from 5.46, 5.63 and 5.30 to 5.29 for R134a/R1234yf, R152a/R1234yf and R161/R1234yf. The heating COP first increases from 3.90 to 4.00 and later decreases to 3.79 for R32/R1234yf, while it decreases from 3.84, 3.95 and 4.02–3.79 for others. Caused by different volumetric capacities, R32/R1234yf requires a compressor enlarged by 2.8 times, R134a/R1234yf and R152a/R1234yf requires little change on compressor size, while R161/R1234yf requires a compressor enlarged by 1.5 times. R32/R1234yf yields the highest discharge temperature, while R134a/R1234yf yields the lowest. R32/R1234yf shows the highest exergy COPs (ECOPs) when the R1234yf mass fraction is above 60% in cooling mode and 46% in heating mode. Otherwise, R152a/R1234yf performs the best in cooling model and R161/R1234yf performs the best in heating mode. Considering both GWP and efficiency, the optimal composition is 20/80% for R32/R1234yf, 10/90% for R134a/R1234yf and 100/0% for both R152a/R1234yf and R161/R1234yf. This study provides suggestions for the determination of optimal compositions of different HFC/R1234yf mixture refrigerants.