Refrigeration systems needs efficient refrigerant to perform it's determined objective, so, an optimum refrigerant, must have a good and desirable characteristics as compared with other refrigerants as well as a high coefficient of performance for the working cycle, which results for minimizing operating power to attain determined refrigeration capacity.
A variety kinds of improved refrigerants had been appeared within the last twenty years, and many countries did large efforts to phaseout some refrigerants, or at least reduce it's usage, that's for it's ozone layer depletion and it's bad influence on environment and climate.
This research deals with a comparative study between many Refrigerants on the basis of it's characteristics , COP and compressibility factor in ejector refrigeration system to select the optimum to be used in this system.
From this study results , the optimum refrigerant is Butane (R – 600), which have a good characteristics , a relatively high compressibility factor values , and a COP value of (0.615) , which is a good result as compared with other refrigerants included the phaseouted for it's bad influence on environment and climate.