Effect of Capillary Tube Length and Refrigerant Charge on the Performance of Domestic Refrigerator with R12 and R600a

In this work, the thermodynamic performance of a domestic refrigerator was experimentally studied by simultaneously varying the refrigerant charge (mr) and the capillary tube length (L). The potential of replacing R12 by R600a was also investigated. The test rig for the experiment was a vapor compression refrigerator designed to work with R12. The enthalpy of the refrigerants R600a and R12 for each data set for the experimental conditions were obtained by using REFPROP software (version 9.0). The results show that the design temperature of -120C (according to ISO - 8187 standard) and pull – down time of 135 minutes are achieved by using 60g of R600a with L= 1.2m and 1.5m. For R12, the design temperature is achieved at pull – down time of 165 minutes with mr = 40g and L = 0.9m. The appropriate combination of L and mr for R600a to be used as a drop-in refrigerant for R12 is found to be 1.5m and 60g on the basis of power consumption per day, pull-down time and COP, whereas by considering the cooling capacity, it is 0.9 m and 60g. The cooling capacity of R600a was about 9.18% higher than that of R12, the power consumed by R600a was about 24 % lower than that of R12 and the COP of R600a was about 6.3% higher than that of R12. In conclusion, the proposed R600a seems to be an appropriate long-term candidate to replace R-12 in the existing refrigerator in terms of power consumption, cooling capacity and COP