Abstract
In any thermal energy conversion systems such as refrigeration and air-conditioning systems, it is needless to emphasize a vital importance of selecting the optimum refrigerant so as to achieve the designed performance of the system. In the present paper, the author attempts to summarize an overview on the development of refrigerants for refrigeration and air-conditioning system, and/or working fluids in general for heat-pumping equipment, over the last several decades in the light of various obstacles recognized in the past. It is no doubt, however, that the global environmental issues such as stratospheric ozone depletion and global warming have impacted the refrigeration and air-conditioning industry worldwide like no other event in history. The discussion also covers the current state of the arts to identify the optimum refrigerants among proposed candidates including hydrofluorocarbon refrigerant mixtures and natural working fluids. For the future perspectives, some of the existing novel challenges in progress will also be presented.
