Thermodynamic analysis of optimal condensing temperature of cascade-condenser in CO2/NH3 cascade refrigeration systems

This study thermodynamically analyzed a cascade refrigeration system that uses carbon dioxide and ammonia as refrigerants, to determine the optimal condensing temperature of the cascade-condenser given various design parameters, to maximize the COP and minimize the exergy destruction of the system. The design parameters include: the evaporating temperature, the condensing temperature and the temperature difference in the cascade-condenser. The results agreed closely with the reported experimental data. The optimal condensing temperature of the cascade-condenser increases with T-C, T-E and Delta T. The maximum COP increases with T-E, but decreases as T-C or Delta T increases. Two useful correlations that yield the optimal condensing temperature of the cascade-condenser and the corresponding maximum COP are presented. (c) 2006 Elsevier Ltd and IIR. All rights reserved.