Development and demonstration of a microscale absorption heat pump water heater

Abstract

The development and demonstration of a compact ammonia–water absorption heat pump water heater using microchannel heat and mass exchangers is presented. The absorber, condenser and evaporator are hydronically coupled, while the desorber is direct natural gas-fired. A heat pump comprised of discrete microchannel components was first fabricated and tested on a breadboard facility. Component and system performance are experimentally investigated over a range of conditions, and insights from experiments are used to refine designs. The refined designs are used to develop an integrated microchannel monolithic heat and mass exchanger packaged into a prototype absorption heat pump water heater containing all auxiliary support systems to allow for connection to a water storage tank. The system is nominally sized to provide 2.79 kW of heat at a coefficient of performance (COP) of 1.74. Performance is experimentally investigated at the design condition of 32 °C coupling water into the system and an ambient of 20 °C, and over the range of expected water temperatures (10–60 °C) and ambient conditions (10–32 °C).