Evaluation of performance of heat pump system using R32 and HFO-mixed refrigerant.

Recently several refrigerants have been lined up as candidate alternatives to R410A in order to prevent further global warming and to promote saving energy. We have selected R32 from among these candidates; however it is important to continue comparing it to other refrigerants in search for an even better choice. Therefore we carried out evaluation of the new R32/R1234ze(70/30) refrigerant by comparing its COP and compressor discharge temperature etc. to those of R410A, and the results of R32. We also conducted analysis regarding the drop of COP during Cooling operation in case of high outside temperature. As a result, we found that the COP of R32 is superior to the other refrigerants due especially to its small amount of pressure loss. As the discharge temperature for both the R32/R1234ze(70/30) refrigerant and R32 was roughly the same, we re-confirmed that there is no problem using R32. Additionally, for non-azeotropic refrigerants such as R32/R1234ze(70/30), a Temperature Glide occurs during phase change. During the current evaluation, we came across a number of performance degradation phenomena thought to be caused by this glide. Meanwhile, we compared the COPs in the high ambient temperature, and recognized that the superiority of R32 in the 35°C ambient could be obtained also at higher ambient temperature. From the above, we confirmed that R32 is indeed the best candidate at present. Even though we will continue to carry out evaluation in search for a better candidate.