GB894011A - Heat pump - Google Patents

Abstract

894,011. Refrigerating; heat pumps. WISEMAN, A. R. A. April 8, 1960 [Jan. 10, 1959], No. 982/59. Class 29. In a heat pump of the compression type for heating domestic air or water, the evaporator, at normal ambient temperature, is heated by ambient air but, at reduced ambient temperatures, a second stage operating at lower temperature levels is brought into operation by a thermostat responsive to ambient temperature, and heats the first stage evaporator. As shown in Fig. 1, two compression systems are in cascade, the condenser R1 of the upper stage being located within the building, the compressor C2 of the lower stage being controlled by ambient temperature, and the heat exchanger constituted by the evaporator El and the condenser R2 being so constructed that the former can receive heat either from the latter or from ambient air. In a modification, evaporator El comprises two sections in series in heat exchange respectively with ambient air and condenser R2. The low temperature evaporator may be defrosted by water, hot gas, electric heating, vibration or mechanical deformation. More than two stages may be provided. The compressors may be driven by J.C. engines, the waste heat of which augments the heat pump effect. According to the Provisional Specification, at high ambient temperatures, refrigerant is evaporated in a high temperature evaporator heated by ambient air and compressed by a first compressor; at low ambient temperatures, a second compressor is also energized and liquid refrigerant not evaporated in the high temperature evaporator is evaporated in a second evaporator operating at lower pressure and is compressed by the two compressors in series. Superheat is removed from the vapour compressed by the second compressor in interstage coils by bleeding liquid refrigerant from the condenser through an auxiliary expansion valve.