Thermodynamic analysis of a novel dual-temperature air-source heat pump combined ejector with zeotropic mixture R1270/R600a

Abstract

This study presents a novel dual-temperature air-source heat pump system with an ejector using zeotropic mixture R1270/R600a. The system provides a high-temperature heat source (around 60 °C hot water) and low-temperature heat source (around 35 °C hot water) respectively. The system improves its performance via the application of an ejector. The mathematical model based on the energetic method is established to analyze and compare the performance between the novel dual-temperature air-source heat pump system (DTHP-II and DTHP-III) and the conventional dual-temperature air-source heat pump system (DTHP-I), including the heating coefficient of performance (COPh), the heating capacity per volumes (qv) and the second law efficiency (ηII). The results show that the DTHP-II and DTHP-III systems significantly outperform the DTHP-I system under various operation conditions due to the application of ejector. Compared with the DTHP-I, the COPh, qv and η=2\\*ROMANII of DTHP-II are improved by 20.2%, 19.5% and 18.2%. Again, compared with the DTHP-II, the COPh, qv and ηII of DTHP-III are improved by 36.5%, 37.2% and 38.5% respectively. The heat source temperature affects heat pump system performance significantly. And the DTHP-II and DTHP-III save more energy under the demand for a higher temperature source. Mass fraction of R600a in the zeotropic mixture (z) and the high low-temperature heat source load ratio (LR) show a noticeable effect on the system performance, which should be given attention when designing the DTHP system.