Presently, the emphasis is to utilize renewable energy sources such as solar energy and waste heat from industrial processes to produce refrigeration. Ejector refrigeration has been suggested by many investigators as one of the possible alternatives for the vapor compression refrigeration due to its potential for utilization of low grade thermal energy as low as 60°C. The present study describes a computer simulation model for ejector refrigeration systems using constant pressure mixing ejector theory. A regenerator and a precooler have been added to improve the system performance. Ejector refrigeration systems traditionally use water as refrigerant. In this study, zero ozone depletion hydro-fluoro-carbon (HFC) refrigerants such as R134a as well as hydrocarbon refrigerants such as propane (R290) and isobutane (R600a) have been used as working fluids and a comparative performance analysis has been carried out. A variable geometry ejector has also been used in the analysis to predict optimum performance of refrigeration system for varying operating conditions.