Exergy characteristics of R404A indirect refrigeration system using CO_2 as a secondary refrigerant

摘要

In this paper, R404 refrigeration system is evaluated to understand the exergy characteristics of an indirect refrigeration system for R404A that adopted CO2 as a secondary refrigerant. This provides basic data for the optimal design of indirect refrigeration system for the R404A. The results are summarized as follows. It was confirmed that the system's exergy loss increased as the R404A condensation temperature, the CO2 cooler temperature difference, and the CO2 mass flow rate increased under a fixed experimental condition. However, the system's exergy loss decreased as the CO2 evaporation temperature increased. It was also found that the exergy loss of the R404A refrigeration system was higher than that of the CO2 secondary refrigerant system. It was also confirmed that total exergy loss of the R404A refrigeration system and the indirect refrigeration system tended to be inversely related to the coefficient of performance. Regardless of any experimental conditions, the exergy loss rate of components was the largest in the compressor, followed by the R404A condenser, the expansion valve, the internal heat exchanger, the CO2 cooler, the CO2 evaporator and the pump. Therefore, in conclusion, it is necessary to reduce exergy loss in the compressor and the R404A condenser to improve the overall performance of this system.