Heating performance of a mobile heat pump system with natural refrigerant CO2 2019-01-0912
Natural refrigerant CO2 (GWP = 1) is considered as a promising alternative to HFC-134a in mobile air conditioning (MAC) applications. This study investigated the heating performance characteristics of a CO2 heat pump system for an electrical vehicle in a cold climate. A prototype CO2 heat pump system was developed and tested, consisting of a CO2 electrical compressor, CO2 parallel flow microchannel heat exchangers, and an electrical expansion valve. A newly developed mobile CO2 compressor with 6.8 ml displacement and 8000 RPM maximum speed was employed. Besides, a novel CO2 heat pump system with Series Gas Cooler (SGC) configuration was proposed for application in an Electrical Vehicle (EV). At the extreme cold temperature of -20 ℃, the novel EV CO2 heat pump system achieved 5.6 kW maximum heating capacity and 1.8 COP, which greatly outperforms the conventional PTC heating supplement for an EV. Therefore, the heat pump using CO2 refrigerant achieved good heating performance in a cold climate. Additionally, a new secondary loop heat pump was also compared with the conventional heat pump, and the test results show that use of the secondary loop heat pump reduced COP by 19%.