GWP, COP, Refrigerant, Heat pump system, R410A, R32/R1234yf, R32, zeotropic, High ambient temperature
R32 was selected as the alternative for R410A for mini-split air conditioners/heat pumps and already phased out R410A in residential market in Japan. Recently several new alternatives for R410A have been proposed in order to achieve more close capacity to R410A and mitigate high discharge temperature issue of R32 as well as to reduce energy consumption. We selected R32 from among the candidates a few years ago; however it is important to continue comparing it to new candidates in search for an even better choice. We carried out performance evaluation for the lower GWP refrigerant R32/R125/R1234yf (67/7/26) and R32. We also conducted the experiments in cooling operation at high ambient temperature. As the result, we found that the COP of R32 is superior to the blend because of its latent heat characteristic. In particular, as condensing temperature increases such as at high ambient temperature operation, latent heat of the blend obtains even smaller. Therefore, advantage of R32 in COP becomes more significant at high ambient conditions. From the above, we consider that R32 is still the best refrigerant at present. However, we will continue investigation in search for a better refrigerant.