Heat recovery design and test for the secondary loop heat pump MAC system

Abstract

Abstract In mobile air conditioning (MAC) systems, the secondary loop (SL) structure was usually adopted when using flammable refrigerants such as R1234yf, R290 and R152a. The introduction of intermediate heat exchangers in SL system inevitably increased the temperature difference between the condensation side and the evaporation side, thereby increased the compressor power consumption and caused the performance attenuation. To overcome the attenuation, this study designed a heat recovery device which collects the waste heat from the passenger compartment to increase the evaporation temperature and reduce the compressor power consumption. Validation experiments were completed in a secondary loop heat pump (SLHP) MAC system using R152a and was compared with a baseline direct expansion (DX) system. According to experimental results, under the -10 °C outdoor temperature, the SLHP system showed performance attenuation compared with the DX system. With the increase in indoor temperature, the attenuation gradually increased to 8.96% at the indoor temperature of 20 °C. In this case, a heat recovery design was used in the SLHP system, which increased the coefficient of performance (COP) by 9.29% compared with the original SLHP system and achieved similar performance to the DX system.