Energetic and entropy analysis of a novel transcritical CO2 two-stage compression/ejector refrigeration cycle for shipboard cold chamber

Abstract

The adverse effects of global warming and climate change require critical measures for marine refrigeration technology because of its impact on greenhouse gas emissions. A novel transcritical CO2 two-stage compression/ejector refrigeration cycle for shipboard cold chamber is proposed in this research. A comparative analysis was conducted between the basic transcritical CO2 two-stage compression cycle and the cycle equipped with a two-phase ejector considering the coefficient of performance. Meanwhile, the refrigeration cycle was analyzed using entropy analysis to elucidate the distribution of irreversible losses in each component of the two-stage compression/ejector refrigeration cycle, and the effects of system parameters such as the evaporating and gas cooler outlet temperatures as well as the intermediate and discharge pressures on the cycle were investigated. The results showed that the ejector had the largest power capability loss, accounting for 26.95 % of the overall system, which is followed by the low-pressure compressor with 26.06 %. The coefficient of performance of basic and ejector system significantly increase as the gas cooler outlet temperature and intermediate pressure decrease as well as the evaporating temperature increases. Furthermore, the entropy production of the system components decreases gradually with increasing evaporating temperature, with the greatest reduction in the ejector. In addition, the entropy production of the two-phase ejector remains constant with the increase of the high-pressure side discharge pressure and gas cooler outlet temperature.