Image Number 5 for United States Patent #4596123.
This invention is an improved refrigerant-cycle heat pump that requires neither a defrosting means nor a backup heat source. From widely varying outside environments, it pumps heat to heat living spaces or domestic hot water. Liquid refrigerant flows from a receiver through expansion valves into an outside evaporator consisting of a segmented array of plates where heat is absorbed from the atmosphere to evaporate the refrigerant. The resultant gas is compressed by a motor-driven compressor, gives up heat in a condenser, becomes liquid, and returns to the receiver. The segmented evaporator enables the self-governing heat pump system to choose the proper magnitude of evaporator area, in response to its determination of compressor suction pressure or motor power demand, so as to provide a steady refrigerant flow to the compressor and thereby maintain optimum heat pumping despite extreme excursions of outside temperature. The configuration of evaporator segments as plates enables the system to operate without interruption or performance deterioration even though frost or ice forms on plate surfaces.