A thorough comparison of the R744 and R134a HP systems at both cooling and heating modes is made at the same test conditions. The HP system structure is different, with indoor gas cooler (IGC) and evaporator in series (for R744 system) or in parallel (for R134a system). At cooling mode, the ambient temperature ranges from 15°C to 45°C; for heating, tests are performed at three typical temperatures (-15°C, -10°C, -5°C). In addition, the cooling/heating capacity and COP of R744 HP system are compared with or without battery cooling/heating mode. Test results show that, in hot weather, the R744 HP system proposed in this study can achieve a similar or better cooling capacity than that of R134a HP system; keeping the same cooling capacity, the coefficient of performance (COP) is equivalent or higher than that of R134a system. In heating mode, the performance of R744 HP system is much better than R134a HP system. The R744 HP system with or without battery cooling/heating shows a similar cooling/heating capacity, the COP of the system becomes larger if there is a demand for battery heating in cold weather. The fully comparison of R744 and R134a HP system performance and the stable performance of R744 HP system with/without battery cooling/heating indicates that the R744 HP system proposed in this paper shows a very high potential for application in electric vehicles.

在相同的测试条件下，对制冷和加热模式下的R744和R134a HP系统进行了全面比较。HP系统的结构不同，室内气体冷却器（IGC）和蒸发器串联（对于R744系统）或并联（对于R134a系统）。在冷却模式下，环境温度范围为15°C至45°C；对于加热，在三个典型温度下进行测试（-15°C -10°C -5°C）。此外，比较了有无电池冷却/加热模式时R744 HP系统的冷却/加热能力和COP。测试结果表明，在炎热的天气中，本研究中提出的R744 HP系统可以达到与R134a HP系统相似或更好的冷却能力。保持相同的冷却能力，性能系数（COP）等于或高于R134a系统。在加热模式下，R744 HP系统的性能远远优于R134a HP系统。带有或不带有电池冷却/加热的R744 HP系统都具有类似的冷却/加热能力，如果在寒冷的天气中需要电池加热，则系统的COP会变大。