Performance Investigation of CO2 Automotive Air-conditioning System with Ejector at 45°C Ambient Temperature

The ejector-expansion system design is an effective approach to improve the cooling performance of transcritical CO2 systems. In this study, a transcritical CO2 air-conditioning system with an ejector for electric vehicles is built up to experimentally investigate the cooling performance at an extreme temperature of 45°C. The performance improvement is evaluated compared to the corresponding basic system. The effects of electronic expansion valve's (EXV) opening, compressor speed, and fresh air ratio are analyzed. The results show that the ejector can effectively improve system COP by 4.61 – 16.52 % under test conditions. At 45°C/27°C (out-cabin/in-cabin) condition, the optimal COP of 1.52 can be obtained at EXV's opening of 65%. The entrainment ratio significantly goes up from 0.22 to 0.60 as EXV's opening increases.