Experimental analysis of the air-to-water ejector-based R290 heat pump system for domestic application

The aim of this study was to analyze and compare the performance of an 8 kW ejector-based R290 heat pump system for hot water heating applications that operates with two different expansion devices: a throttling valve and a two-phase ejector. The vapor compression system was designed to compare the unit operating in direct expansion and ejector-based working modes under similar operating conditions. The test results were assessed for overall system performance measured by COP and heating capacity and for single-component operation. The ejector mode allowed operation at the same range of ambient temperatures as direct expansion mode with the potential to completely replace the expansion valve. The COP of ejector system was up to 2.6, which was 38% higher than direct expansion when working under similar conditions for an ambient temperature of -12.8 degrees C. Moreover, the COP in direct expansion mode decreased significantly along the decrease of ambient temperature, whereas for the ejector mode this decrease was considerably smaller.