Experimental comparison of R744 and R134a heat pump systems for electric vehicle application

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 degrees C to 45 degrees C; for heating, tests are performed at three typical temperatures (-15 degrees C,-10 degrees C,-5 degrees 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. (c) 2020 Elsevier Ltd and IIR. All rights reserved.