The aim of this paper is to determine the best available alternative which coul
d replace existing
refrigerant R 22, with minimum or no changes in the air c onditioning system. For this purpose, both the
theoretical as well as experimental studies done in this area of research have been reviewed. The most popular
HFC, R410A is having lower critical temperature, which restricts its usage in compression based sy stems
working at higher condensing temperatures whereas for R407C, a change to synthetic lubricant is required and
HC 290 is flammable. It is suggested that until the safety issue of use of hydrocarbon refrigerants in quantities
exceeding 500gm is resolved , we should go for those mixtures of HFCs and HCs for which TEWI index is the
lowest