Abstract: In order to meet the needs of environmental protection and closely follow the development trend of electric vehicles, a CO2 air conditioning system for electric vehicle was developed based on the traditional air conditioning system of vehicle, the effects of different operating parameters on its performance were studied on the standard mobile air conditioning bench in order to see the new rules and provide guidance for the optimization of key components. Results show that the performance of the developed CO2 system can match the traditional refrigerant R134a, which is still commonly used. Among all the operating parameters, it was found that the outdoor temperature has the greatest impact on the system performance, and the performance decay is obvious under high temperature. The electric compressor can meet the cooling capacity needs of a real car, in some harsh conditions, system performance can not be optimal because of the discharge pressure and temperature limits of the existing CO2 electric compressor, so there is much space for system performance improvement by optimizing the compressor. If the temperature difference between the refrigerant and environment at the outlet of gas cooler can drop by 1℃ for the same heat exchange area, the COP of the system can be increased by 2%～5%, the optimal high pressure of the system can be reduced as well, if the evaporation temperature can increase by 5℃, the COP of the system can be increased by 15%.

Key words: CO2; electric vehicles; trans-critical cycle; performance; pressure