Exergy Analysis of Influence of Intermediate Temperature on Cascade Refrigeration System

In order to improve the thermal performance and reduce the energy consumption of R404A/R23 superposed refrigeration system, the effects of intermediate temperature and evaporation temperature on total energy consumption, thermal performance, exergic loss and exergic efficiency of superposed refrigeration system are analyzed by establishing thermodynamic model and using thermal analysis and exergic analysis. The results show that under the condition of no superheating and subcooling, with the increase of intermediate temperature T₃(low-temperature cycle condensation temperature), the total power consumption and exergic loss of the system first decrease and then increase, and the thermal performance COP and exergic efficiency increase first and then decrease and thus determine conditions exist an optimal intermediate temperature T₃make the system energy consumption, minimum exergic loss, thermal performance COP and exergic efficiency of system is the largest. By analyzing the change of the exergy loss of each component of the system with the intermediate temperature, it is concluded that the exergy loss of the system is mainly concentrated in the evaporative condenser, high temperature level compressor, high temperature level throttle and condenser. With the change of the intermediate temperature T₃, the exergy loss of these four components accounts for 57.5% to 85.7% of the total exergy loss. In the optimal intermediate temperature T₃, the four parts exergic damage accounted for 66.9% of the system total exergic loss. The influence of evaporation temperature on the system is analyzed. It is concluded that the change of evaporation temperature will change the optimal intermediate temperature, and with the increase of evaporation temperature, the optimal intermediate temperature will also increase, and the thermal performance and exergic efficiency of the system will also increase significantly.