Experimental investigation on control strategy of electric vehicle heat pump with refrigerant injection at low temperature

作者：Xu, Qiangqiang; Wu, Jianghong^*; Guo, Zhengdao; Xu, Geyao; Chen, Yiqun; Yang, Huaiyu; Xue, Xiangjin

来源：International Journal of Refrigeration, 2022, 138: 40-51.

DOI：10.1016/j.ijrefrig.2022.03.024

• Control strategy
• Refrigerant injection
• Heat pump
• Electric vehicle
• Load demand
• Discharge temperature

A heat pump cycle with refrigerant injection is one of the effective means to enhance the heating performance of electric vehicles in low temperature climate. The control strategy is very critical for the application of refrigerant injection technology in electric vehicles. In this paper, the variation of cabin load demand with ambient temperature is first presented for electric vehicles. Secondly, a test bench of heat pump system with refrigerant injection is built to compare the system heating performance under different control strategies. Considering the compressor discharge temperature and the load demand, the applicable temperature range under different control strategies is determined. The experimental results show that the control strategy of the main branch with slightly wet can effectively reduce the compressor discharge temperature and improve the heating performance of the system. The compressor discharge temperature can be reduced by up to 23 degrees C with above control strategy. The system heating capacity and COP can be increased by up to 5.7% and 4.7%. Vapor injection cycle can meet the demand at the ambient temperature above -15 degrees C. The two-phase injection cycle further extends the temperature range of the system operation at low temperature, and the lowest temperature can reach -22 degrees C.