Azeotropic refrigerants and its application in vapor compression refrigeration cycle

Searching for the refrigerants with less influence on the global warming is one of the main challenges of the refrigeration industry. The azeotropic refrigerants are attracting increasing attentions due to their special thermophysical properties. An evaluation of mixed-refrigerants is performed on the vapor compression refrigeration cycle and regenerative cycle, synthetically considering the coefficient of performance (COP), volumetric refrigeration capacity (VRC), pressure ratio and discharge temperature. The tests show that all the positive azeotropic refrigerants achieved better VRC than its compositions. The COP of the mixtures is generally lower than that of the best individual refrigerants, but higher than the zeotropic compositions. The present results suggest the superiorities of the azeotropic refrigerants, especially for binary and ternary systems including ammonia. The maximum pressure at the azeotropic location and the consequent extreme density are the main reason why positive azeotropes dominate in refrigeration.