Experimental performance analysis of ejector heat pump water heater under transient conditions

Net-zero energy buildings are on the agenda of the international community due to reduced energy consumption in the buildings, which in turn lowers carbon emissions and negative environmental effects. One of the ways to reach net zero in buildings is to utilize heat pumps to decrease their energy consumption. In this study, the idea of ejector utilization in a heat pump system was investigated in an experimental test facility by comparison to a conventional heat pump system (without an ejector). The experimental facility, which utilizes hot and cold water as the heat source, can operate in two modes: as an ejector heat pump water heater (EHP-WH) and as a heat pump water heater (HP-WH). The system was tested in transient conditions and the effect of ejector utilization on the system was determined. Results indicate that the EHP-WH mode (coefficient of performance [COP] between 5 and 6) had a COP value on average 5.5% higher than for the HP-WH mode (COP between 4.5 and 5.5). Furthermore, the heating capacity obtained in the EHP-WH mode was 30% higher than for the HP-WH. Additionally, the water cooler loop's water temperature was 64.5% higher in the EHP-WH mode than in the HP-WH mode. Finally, it is determined that the ejector positively impacts the performance of te HP-WH system.