Theoretical analysis on a novel two-stage compression transcritical CO2 dual-evaporator refrigeration cycle with an ejector

Abstract

This paper proposes a novel two-stage compression transcritical CO2 dual-evaporator refrigeration cycle with an ejector. The ejector and flash tank introduced in the novel system is used to reduce the flashed vapor flowing through the low-temperature evaporator and thus reduce the input power of the low-temperature compressor, rather than traditionally reducing the compressor input power by lifting the compressor suction pressure. Thermodynamic analysis results indicate that under all given operating conditions, the performances of novel system are better than those of conventional system. Compared with the conventional system, the COP and exergy efficiency of the novel system under a typical operating condition is increased by 19.6% and 15.9% respectively, and the discharge temperature of high-temperature compressor in the novel system is reduced by 10.5 °C. In addition, the optimum gas cooler pressure of the novel system is 10.3 MPa, which is lower than that of the conventional system. Moreover, exergy analysis results display that the overall exergy destruction in all expansion devices for both systems accounts for the largest part of the total exergy destruction, but its proportion of the novel system is smaller than that of the conventional system.