Performance analysis of an ejector-boosted solar-assisted flash tank vapor injection cycle for ASHP applications

A novel ejector-boosted solar-assisted flash tank vapor injection cycle (ES-FVIC) is proposed for air source heat pump (ASHP) applications. The heating performances of the ES-FVIC and the conventional flash tank vapor injection cycle (FVIC) are analyzed by employing the developed mathematical model. Compared with FVIC, the simulation results shows ES-FVIC using R134a has 21.4–29.0% improvements in heating COP and 82.1–108.3% improvements in volumetric heating capacity at the given evaporating temperature range (−20 to +5 °C) when the ejector's pressure lift ratio is set as 1.5. The performance improvement amount of the new cycle is primarily determined by the solar energy input ratio. The system can accommodate the changes of solar energy input ratio within a wide range (from 0.3 to 2.0) by adjusting the ejector pressure lift ratio. The system can be switched to the conventional FVIC when solar energy input is too less to support the proper operation. The heating performances of using three low-GWP substitutes (R32, R290 and R1234yf) in ES-FVIC and the comparison with R134a are also presented. The ES-FVIC has shown its potential in advanced solar energy utilization by applying the ejector to improve the performance of the FVIC and enlarge its application in ASHP.