Simulation Analysis and Experimental Study on Substituting R134a with R290 in Electric Vehicle Compressors

Because the driving method of electric vehicles differs from that of conventional ones, the power sources of electric vehicles can be diversified. The Global Warming Potential (GWP) and ozone depletion potential (ODP) values of the refrigerant R290 are lower than those of R134a. Consequently, R290 has become an important option for electric vehicle air-conditioners. In this study, an electric vehicle air-conditioning compressor test system was set up to study the compressor performance of two refrigerants (R134a and R290) under variable evaporating temperatures, condensing temperatures, and compressor speeds. The simulated and experimental values for the two refrigerants were also analyzed. The results reveal that the condensing temperature significantly affected the compressor powers of R134a and R290. As the condensing temperature increased by 1 ℃, the compressor power increased by ~3%. The evaporating temperature had a smaller effect on the compressor powers of R134a and R290: as the evaporating temperature increased by 1 ℃, the compressor power decreased by ~0.3%. The prediction errors of compressor power for R134a and R290 were approximately 5% and 10%, respectively. For the same temperature difference, the compressor performance of R290 was significantly better than that of R134a. Furthermore, the isentropic and volumetric efficiencies of R290 were 10%-15% and 6%-9% higher, respectively. At the same pressure ratio, the compressor performance of R290 was similar to that of R134a. In addition, the compressor performances of R290 and R134a were essentially the same at different compressor speeds. However, further optimization is necessary for the applicability of semi-empirical simulation models in variable-speed compressors, particularly at high compressor speeds.