Theoretical Study on CO_2 Transcritical Cycle Combined Ejector Cycle Refrigeration System

摘要

Chlorofluorocarbons( CFCs) or hydrochlorofluorocarbons (HCFCs) are as main refrigerants used in traditional refrigeration systems driven by electricity from burning fossil fuels, which is regarded as one of the major reasons for ozone depletion (man-made refrigerants emission) and global warming ( CO_2 emission). So people pay more and more attention to natural refrigerants and energy saving technologies. An innovative system combining CO_2 transcritical cycle with ejector cycle is proposed in this paper. The CO_2 compression sub-cycle is powered by electricity with the characteristics of relatively high temperature in the gas cooler (defined as an intercooler by the proposed system) . In order to recover the waste heat, an ejector sub-cycle operating with the natural refrigerants ( NH_3, H_2O) is employed. The two sub-cycles are connected by an intercooler. This combined cycle joins the advantages of the two cycles together and eliminates the disadvantages. The influences of the evaporation temperature in CO_2 compression sub-cycle, the evaporation temperature in the ejector sub-cycle, the temperature in the intercooler and the condensation temperature in the proposed system performance are discussed theoretically in this study. In addition, some unique features of the system are presented.