Compressor Performance for Varying Compositions of High-Glide Mixtures R1233zd(E)/R1234yf and R1336mzz(Z)/R1234yf

Theoretical work has shown that zeotropic mixtures allow COP improvements for heat pumps if large temperature changes in the heat source and heat sink exist, as is common in industrial applications. However, the improvements shown in modeling work can only be harvested in a real system if the refrigerant mixture does not lead to a significantly lower compressor efficiency. This study presents experimental data for the mixtures R1233zd(E)/R1234yf and R1336mzz(Z)/R1234yf, featuring temperature glides of more than 30 K. Experimental data was collected at several suction pressures with varying pressure ratios for each pure refrigerant and three compositions for each mixture. Overall isentropic compressor efficiency, volumetric efficiency, and compressor heat rejection were compared as fundamental dimensionless performance measures. The isentropic and volumetric efficiency were a strong function of the suction pressure and pressure ratio, but little deviation was found among the different fluids and mixtures. Two empirical functions with a total of 6 fitting coefficients were found to represent the volumetric and isentropic efficiencies of all mixtures and operating conditions well.