Performance analysis of a dual temperature heat pump based on ejector-vapor compression cycle

Abstract

The dual temperature air-source heat pump reduces energy consumption and has wide application potential. A novel dual temperature air-source heat pump (NDAHP) system based on ejector-vapor compression cycle is proposed in this study. The system produces two types of heat sources (high- and low-temperature hot water). A theoretical model describing the performance of the system is established and validated, and the performance indices of the system, including the heating coefficient of performance (COPh), heating capacity per volume (qv), and the second law efficiency (ƞII) are obtained. The above-mentioned indices of the conventional dual temperature air-source heat pump (CDAHP) system and the NDAHP system using various refrigerants (R717, R1234yf, R134a, and R290) are compared. Results show that the NDAHP outperforms the CDAHP under various operating conditions. Compared with the CDAHP, the NDAHP improves the COPh, qv, and ƞII by 20.0% to 48.9% under a typical operating condition. The R290 shows the best performance among the various refrigerants. The performance of the NDAHP system is more sensitive to the evaporating temperature than the condensing temperature. Additionally, the ƞII of the NADHP system is significantly affected by the high-temperature heating load ratio (LR) and increases with the increase of the LR. This study hopes to provide a foundation for further research on the NDAHP systems.