PERFORMANCE OF A HEAT-PUMP WITH A DIGITAL EXPANSION VALVE

The use of electronics, microprocessor design in particular, in the improvement of heat pump operation involves the conception of new expansion devices. This paper studies the operation of a digital expansion valve, set on a water-water heat pump with a 100 kW heat capacity. The performances of a heat pump are compared when this latter is equipped either with a digital or a thermostatic expansion valve. In a heat pump equipped with a digital expansion valve, the heat capacity gain can reach 5 %. Expansion in the digital valve occurs through gauged orifices where critical flow is appeared in some cases. In comparison with the thermostatic expansion valve, the digital one can optimize the heat pump operation in the whole range of operating temperatures.