Experiment Investigation and Control Strategies on Two-Phase Refrigerant Injection Heat Pump System for Electric Vehicle in Start-up Stage

Due to the poor heating performance and operating safety in low ambient temperature, traditional Air Source Heat Pump (ASHP) for Electric Vehicles (EVs) has many limits in cold region, which can be solved by the ASHP with refrigerant injection. During the start-up stage of EV in winter, the inlet air temperature of the in-car condenser is the same as the ambient temperature. At this situation, the performance and control strategy of the heat pump require special attention. In the present study, a series of experiments were carried out on the heating performance of the Refrigerant Injection Heat Pump (RIHP) system in start-up stage of EV, at the ambient temperature from −20°C to −5°C. The effects of compressor speed and injected refrigerant state on the heating performance of the system were discussed in depth. According to the results, the control strategies during start-up stage have been discussed in the end of the article. The study provides a practical control strategy for the RIHP system during the start-up stage of electric vehicles, helping to efficiently operate electric vehicles in cold regions.