Secondary loop reversible AC/HP system for electric vehicles

This paper presents experimentally obtained results of a secondary loop air conditioning-heat pump system compared to a baseline direct system. The secondary loop system has a refrigerant circuit operating between two 50/50 water glycol loops, and uses the identical compressor and accumulator as the baseline DX system. For most operating conditions in this study, the secondary loop system has slightly lower maximum capacity and lower COP/HPF compared to the DX system, while it has potential for integrated thermal management, waste heat recovery, and may allow better refrigerants to be used due to compact refrigerant loop design. It was found that system refrigerant charge needed for cooling was close to that for heating, and was about 200g less than required by the baseline. Operating parameters including compressor and pump speeds, air flow rates, and condenser exit subcooling were investigated to improve energy efficiency. Performance in different ambient conditions was also studied and compared to the baseline