Developments of next generation refrigerants and heat transfer

Since the effect of refrigerants which are widely used in heat pump and refrigeration systems on the global warming has become a big environmental issue, researches and developments on the next generation refrigerants are being conducted intensively. Values of global warming potential (GWP) of most of currently used refrigerants are grater than 1000. R32 which becomes popular as a refrigerant of domestics air-conditioners for years has GWP=675. Recently, some hydrofluoroolefins (HFOs) are getting attention and their thermophysical properties and heat transfer characteristics are being clarified experimentally because GWP of HFOs are very small in which the values of some HFOs are less than 1 and those of others are less than around 10. For example, R1234yf and R1234ze(E) are promising candidate of R134a. In this paper, recent developments of the next generation refrigerants and its heat transfer characteristics are introduced