Comparative study on four autocascade refrigeration cycles based on energy, exergy, economic and environmental (4E) analyses

Abstract

As known, insufficient component separation of zeotropic refrigerant and massive throttling losses are two major causes for the poor performance of autocascade system. Aiming to combine the benefits of applying two-stage component separation to improve the component separation efficiency and applying ejector to recover partial expansion work, a novel ejector enhanced autocascade refrigeration cycle with two-stage component separation is proposed. The comparative study on the novel cycle and other three autocascade refrigeration cycles are conducted by simulation method, based on energy, exergy, economic and environmental analyses method. The simulation results show that the novel cycle always yields remarkable performance advantage. Under the given condition, the novel cycle respectively improves the coefficient of performance and cooling capacity by 40.8% and 60.8% compared with the convenient autocascade refrigeration cycle. Furthermore, the exergy performance and irreversibility distributions of four cycles are compared. Moreover, the performance variation of the novel cycle with main operation parameters is simulated to investigate the cycle characteristics. The novel cycle achieves the longest payback period of 2.27 years and produces the lowest full life cycle cost of 5268 $, when applied in a low-temperature freezer. Meanwhile, the novel cycle remarkably reduces the carbon dioxide and air pollution emissions.