Analysis of a dual-temperature air source heat pump cycle with an ejector

Highlights: • A novel dual-temperature air source heat pump cycle with an ejector is presented. • Energy and exergy analysis for this novel cycle performances are carried out. • The results indicate that the use of an ejector significantly increases the performance. • The proposed cycle has better performance at lower evaporation temperatures. This paper proposes a novel dual-temperature air source heat pump cycle with an ejector and a flash tank for simultaneous application in the water heater (providing about 55 °C hot water) and the floor or ceiling radiative heating equipment (providing about 35 °C hot water). In the presented cycle, an ejector, a flash tank as well as high and low-temperature condensers are applied to improve its performance effectively. The thermodynamic analysis based on the energetic and exegetic methods are conducted for the novel cycle and the conventional heat pump cycle using environmentally friendly refrigerant R1234yf. Thermodynamic analysis results indicate that under all given operation conditions, the novel cycle has superior performance compared with the conventional cycle. Compared with the conventional cycle, the heating coefficient of performance, the volumetric heating capacity and exegetic efficiency of the novel cycle under the typical working condition are improved by 24.93%, 24.92% and 38.84%, respectively. Furthermore, the results indicate that the novel cycle achieves better exegetic efficiency because the exergy destruction proportion of novel cycle expansion valves is lower than that of the conventional cycle. When a higher temperature source is demanded, the novel cycle saves more energy due to ejector application. Moreover, the novel cycle also has better performance characteristics when the evaporation temperature is lower.