Experimental study of a subcritical heat pump booster for sanitary hot water production using a subcooler in order to enhance the efficiency of the system with a natural refrigerant (R290)

•Experimental facilities for the characterization of heat pumps SHW were built.•Subcooler increases the efficiency of a subcritical heat pump with high water lift.•The approach is applied to water-to-water heat pump dedicated to energy recovery.•This configuration reaches COPs significantly higher than without the subcooler.

This paper presents the experimental results obtained from a new heat pump prototype for sanitary hot water production, in the application of heat recovery from water sources like sewage water or condensation loops (typical temperature condition between 10 °C and 30 °C). The system configuration is able to produce a high degree of subcooling in order to take advantage from the high water temperature glide (typical value for sanitary hot water production is 10 °C to 60 °C). Subcooling is made by using a separate heat exchanger from the condenser (subcooler). The obtained results have shown a high degree of improvement by making subcooling. COP is 5.61 in nominal conditions, which is about 31% higher than the same cycle working without subcooling (Nominal point: inlet/outlet water temperature at evaporator is 20 °C/15 °C and the water inlet/outlet temperature in the heat sink is 10 °C and 60 °C).