The market for Sanitary Hot Water Heat Pumps is growing fast these years due to regulations in EU and UK pushing electrical heaters and gas boilers out of the market in order to lower CO₂ emissions. At the same time refrigerants with high GWP will be pushed out and leaving the industry in the dilemma to switch from typical R-134a to fx. R-290 to meet HFC-gas regulation.

The common solution today is based on a tube wrapped around the water tank. The obvious solution would be down sizing of tube diameter as known from fin&tube heat exchangers, but this will cause an undesired high pressure drop in the system and will destroy a good COP rating. Th ...