Design and rating of an integrated mechanical-subcooling vapor-compression refrigeration system

Subcooling of the refrigerant at the exit of the condenser in a simple vapor-compression refrigeration system allows the refrigerant to enter the main cycle evaporator with low quality. Thus, allowing the refrigerant to absorb more heat in the evaporator; thereby improving the coefficient of performance (COP) of the system. In an integrated mechanical-subcooling vapor-compression refrigeration system, the subcooling is performed by utilizing a small integrated vapor-compression refrigeration cycle, known as the subcooler cycle. This subcooler cycle is coupled to the main cycle at the exit of the condenser and it utilizes the main cycle condenser for rejecting the heat. In this paper, thermodynamic models of an integrated mechanical subcooling system are developed to simulate the actual performance of the subcooling system, particularly with respect to the subcooler saturation temperature in addition to heat exchanger areas. It is demonstrated that the performance of the overall cycle is improved over the corresponding simple cycle. This improvement is found to be related to the refrigerant saturation temperature of the subcooler. The model is also used for predicting an optimum distribution of the total heat exchanger area between the evaporator and condenser.