Energy and exergy analysis of various ejector-assisted two-stage compression heat pumps applied in various conditions

Compared with the single-stage compression, the two-stage compression cycle shows high efficiency and application potential under both severe heating and refrigerating conditions. Therefore, to improve the performance of the two-stage vapor-compression cycle furtherly, this study introduces three ejector-assisted two-stage compression cycles (E1, E2, and E3), and a conventional two-stage vapor-compression cycles (C1) also selected as the comparison. The energetic and exergetic efficiency of the systems using various refrigerants (R152a, R1234yf, R32 and R290) is investigated and compared based on the validated theoretical model for both the severe refrigerating and heating application. The result shows that the ejector improves the system’s performance significantly. Under the refrigerating mode, System E3 using R32 is recommended to be applied. Compared with Systems C1, E1, and E2, the maximum refrigerating coefficient of performance (COPR) of System E3 using R32 is improved by 16.1, 12.4, and 9.1