Ejector Heat Pump for Water Heating.

Water heating is a major energy consumption in the US residential sector. According to the annual energy outlook of the EIA (EIA 2021), the total US national primary energy efficiency of water heating is only 60%. Heat pump water heaters can significantly increase the thermal efficiency of water heating. Electric powered heat pump water heaters are already commercially available in the US. On the other hand, no fuel-fired heat pump water heaters are available, but two are in development, both employ absorption cycle. Thermally driven ejector heat pumps have been discounted for their low efficiency and narrow operating range. In this paper we present performance analysis of a novel ejector heat pump for water heating that overcomes the shortcomings of conventional ejector heat pumps. The heat pump uses binary fluid mixture and active back pressure control. The use of the binary mixture results in high thermal efficiency and the active back pressure control widens the operating range of the heat pump. Two configurations of the heat pump are presented and analyzed. The maximum achievable COP of each was 1.95 and 1.7 at output heating capacities of 5.7 and 6.7 kW, respectively. [ABSTRACT FROM AUTHOR]