Influence of the refrigerant charge in an R407C liquid-to-water heat pump for space heating and domestic hot water production

Abstract

A large number of commercially available domestic heat pumps are being produced without liquid receivers in order to minimize the refrigerant charge. In this type of systems knowing the effect of the refrigerant charge is of prime interest in order to optimize the system performance. This paper presents an experimental study of the influence of the refrigerant charge in an R407C liquid-to-water heat pump for space heating and domestic hot water production. The heat pump consists of a fixed speed scroll compressor, brazed plate heat exchanges and a thermostatic expansion valve. Experimental results are presented for the heating mode of operation at two different water temperatures in the condenser (low and medium temperature applications) with and without domestic hot water (DHW) production in a desuperheater. Results show that an optimum charge that maximized the system COP could be determined. This optimum charge was slightly different when the heat pump was operated for space heating only or for combined space heating and DHW production.