Design and performance evaluation of a cooler refrigerating system working with ozone friendly refrigerant

In this study, a cooler refrigerating system was designed, constructed and tested with various charge quantities of an ozone friendly hydro-fluorocarbon refrigerant (R134a) as working fluid. The results obtained showed that the design temperature and pull-down time set by International Standard Organisation (ISO) for small refrigerator were early achieved with refrigerant charges of 100 and 120 g than with 60 and 80 g charges. Approximately the same pull-down time and minimum temperature of -14°C were obtained with refrigerant charges of 100 and 120 g. Discharge pressure is about the same for 60, 80 and 100 g refrigerant charges, but significant increase in discharge pressure was observed as the refrigerant charge increased to 120 g. The rate of increase in the refrigerating capacity and the COP with respect to evaporator temperature for refrigerant charge of 60 g to 100 g are higher than that for refrigerant charge of 120 g. Highest refrigerating capacity and COP of 4.404 kW and 3.1, respectively, were obtained in the cooler refrigerator with 100 g charge. Generally, the best performance of the cooler was obtained with refrigerant charge of 100 g and increase in the charge beyond 100 g affected the performance of the cooler negatively.