18 May 2017

O.1.7.3 Heat pump for water preparation in block of flats

Recent trends in a building construction in the central Europe show a growing number of well insulated residential buildings. The heat demand for a domestic hot water preparation is in those applications similar or higher than for the space heating. Regular vapor-compression heat pumps reach relatively low SPF 2.5 in such applications. The way to increase SPF is to use a heat pump with multiple heat exchangers on a high-pressure side (desuperheater, condenser, and subcooler) and a special hot water storage tank with three internal heat exchangers for a good temperature stratification. A prototype of a heat pump with desuperheater and subcooler was developed and a mathematical model of a refrigerant cycle was tested on it. The model of heat pump describes a heating capacity and a power input with an average relative deviation lower than 5 %. The validated model was used in simulations of a system for hot water preparation in a block of flats. A water draw in the simulation was set under European standard and measured data from real applications. Results of simulations show improvement of SPF by 26 % for a heat pump with desuperheater and subcooler in comparison with a standard heat pump.