This study proposed an improved CO₂ heat pump system for electric vehicles by introducing the concept of two stage compression with intermediate cooling. A coefficient of performance optimal control strategy was proposed based on the discovered feature that the changing trend of the COP is consistent with that of the inlet temperature of the electronic expansion valve. Contrast experiments between the heat pump with intermediate cooling compressor and the basic heat pump were conducted. Result shows that the two stage compression with intermediate cooling contributes to 50–132% increment in the heating capacity and 18.9–61.9% improvement in the COP over the basic system as the ambient temperature decreases from 0 °C to −20 °C. The advantages increase with the decrease in ambient temperature. The typical COP of this system under −20 °C ambient temperature and 20 °C in-car temperatures condition is approximately 1.70 while the discharge temperature is controlled well within 100 °C.

这项研究提出了一种改进的CO ₂通过引入两级压缩和中间冷却的概念，为电动汽车提供热泵系统。基于发现的特征提出了性能系数最优控制策略，即COP的变化趋势与电子膨胀阀的入口温度一致。进行了带中间冷却压缩机的热泵与基本热泵之间的对比实验。结果表明，随着环境温度从0°C降低到−20°C，具有中间冷却功能的两级压缩使热容量增加50–132％，COP改善18.9–61.9％。优点随着环境温度的降低而增加。