A novel dual-temperature ejector-compression heat pump cycle-exergetic and economic analyses

High-efficiency air source heat pumps are of great importance for energy saving and environmental protection, especially for the cold area in north China. In this study, the thermo-economic performance of the dual-temperature ejector-compression air-source heat-pump (DAHP) cycle, is conducted wherein R1234yf, R290, and R134a are used as refrigerants. Two configurations are examined: DAHP-I (without an ejector, conventional system for comparison) and DAHP-II (enhanced by an ejector). The effects of the principal operating parameters on the system performance, including the exergy destruction (Ex_{d_tot}), exergy efficiency (η_{ex_sys}) and economic, are investigated, and the two systems are compared. The results indicate that the DAHP-II significantly outperforms the DAHP-I in terms of Ex_{d_tot}, η_{ex_sys} and economic index, and the R290 is the most suitable refrigerant applied for the DAHP-II system. Compared with DAHP-I, the Ex_{d_tot} for DAHP-II is reduced by 24.0%–54.8%. For DAHP-II, although the refrigerant type affects Ex_{d_tot} and η_{ex_sys} slightly, while the effect on economic is noticeable. Comparing with R1234yf, the system using the R134a and R290 as the working fluid, the total annual capital cost rate (Ċ_{t ot}) can be reduced by 6.2% and 11.0% respectively. Besides, the DAHP-II outperforms the DAHP-I system significantly with the R134a, R290 and R1234yf as refrigerant in terms of economic. The relative decrease ratio in total annual capital cost rate (Ċ_{t ot}) are 21.6%, 13.5% and 24.0% respectively. This study provides a basis for the application of DAHP system.