Potential enhancement investigation of commercial R744 refrigeration systems based on avoidable and unavoidable exergy destruction concepts.

Abstract

In this paper, the actual feasible reduction in the inefficiencies occurring in two different commercial CO2 refrigeration systems was evaluated. The analysis was based on the calculation of the avoidable and unavoidable irreversibilities taking place in their components. The systems under investigation, which were a R744 refrigeration system with parallel compression and a R744 refrigerating plant with dedicated mechanical subcooling, were assessed by taking into account the design outdoor temperature of 30 °C. A cooling capacity of 100 kW and an evaporating temperature of -10 °C were selected, while the global efficiencies of all the chosen compressors were obtained by using some manufacturers’ selection software. The results revealed that, in both the selected cases, over 60% of the irreversibilities could be brought down. In particular, the inefficiencies of all the compressors were almost totally avoidable, whereas only half of the exergy destruction related to both the gas coolers and the evaporators could be actually reduced. The auxiliary compressor and the subcooling loop were accountable for14.6% and 25% of the total avoidable inefficiencies associated with their corresponding cycles.