Performance simulation of a two-evaporator refrigerator—freezer charged with pure and mixed refrigerants
Abstract A computer simulation of two-evaporator refrigerators charged with pure and mixed refrigerants operating on a Lorentz and Meutzner's cycle has been performed to determine possible substitutes for R12 with an improved energy efficiency. The results for pure fluids indicate that the coefficients of performance (COPs) and volumetric capacities obtained with two-evaporator units are enhanced up to 6 and 15.5%, respectively, compared to those with single evaporator units. This is due to some of the evaporation occurring at higher temperatures in the two-evaporator units. For mixtures, a significant increase in COP of up to 18% is observed by matching the large overall drop in temperature of the air streams, 23°C, with that of refrigerant mixtures in the evaporator. The evaporator area ratio is a very important parameter and depends largely on the load distribution between the two compartments. The effect of the low temperature heat exchanger has been studied by varying its size. As the size increases, the COP also increases with a decreased pressure ratio across the compressor. An optimized two-evaporator refrigerator-freezer unit charged with alternative, ozone-safe refrigerant mixtures may increase the energy efficiency considerably, helping to alleviate the environmental impact of refrigeration.