Exergy Analysis on an Innovative Vapor-Compression Ejector Heat Pump Water Heater

Abstract Ejector-driven systems are thermally operated and capable of utilizing excess thermal energy to aid in boosting the overall efficiency of the system. Traditionally, ejectors have been implemented into systems for cooling purposes, however, recent studies have demonstrated their potential to increase the efficiency in heat pump systems. In this study a theoretical model is developed, its performance is modeled, and an exergy analysis is performed on an innovative vapor compression ejector heat pump (VCEHP) for the purposes of water heating. The analysis is performed assuming the evaporator temperature of 6.5 °C, and a low temperature evaporator (LTE) temperature of 20 °C, for condenser outlet temperature range of 40–60 °C, with R134a acting as the working fluid. The ejector model incorporated was compared to previous experimental studies utilizing R134a, and the predicted coefficient of performance (COP) and back pressures to within 4.01%. The results of the VCEHP are compared to that of a traditional vapor compression heat pump (VCHP) water heater. The theoretical results have shown that the incorporation of the ejector can lead to a 22.78% increase in the system heating COP.