This paper presents the simulated results of vapour compression system with sub-cooling and superheating and to compare the system performance for three refrigerants i.e. R22, R410A and R32. For simulation 1 “TR” (Ton of Refrigeration) capacity of air conditioning unit was considered and compared the performance with liquid sub cooling and vapour superheating at different temperature and pressures. For analysis R22 experimental results were considered and simulated for R410A and R32 refrigerants. The simulated results for sub-cooled in the refrigeration system positively affected the system performance and all the investigated refrigerants benefited from the performance improvement. An increase in the sub- cooling and superheating reduced the compressor work input and increased the coefficient of performance. The COP for R22, R410A and R32 are 2.33, 3.36 and 3.63, i.e. with compare to R410A and R22 the refrigerant R32 yields 7.34% and 36% higher COP. The refrigerant charge in to the vapour compression cycle was, for R22, R410A and R32 are 0.8 kg, 0.8 kg and 0.56 kg which determine the size of compressor. For the same operating temperature and pressures the cooling capacity for R32 is higher than the R22 refrigerant. And also reduces the pressure ratio and increases both refrigeration mass flow rate and coefficient of performance.