Abstract: A reversible compression type refrigeration system is provided having a heating mode and a cooling mode. The system includes a liquid receiver and a liquid refrigerant line for feeding refrigerant to an expansion device. A main service heat exchanger is provided for absorbing heat from a fluid stream in the heating mode and for rejecting waste heat to the fluid stream during the cooling mode. A main process heat exchanger is provided for cooling or heating a load. A sub-cooling heat exchanger is positioned in the liquid refrigerant line between the receiver and the expansion device and connected in heat exchange relation with the fluid stream entering the main service heat exchanger, whereby the liquid refrigerant flowing to the expansion device is sub-cooled both during the heating and the cooling modes and the fluid stream flowing to the main service heat exchanger is warmed.

Abstract: An improved refrigeration evaporator having a first heat exchange element including a fluid inlet and a fluid outlet, for cooling a fluid stream traversing the evaporator by evaporating a volatile refrigerant liquid in heat exchange relation to the fluid stream. The volatile refrigerant liquid is supplied to the evaporator at relatively high saturated condensing temperature and slightly subcooled. The improvement in the refrigeration evaporator comprises a second heat exchange element, positioned in the fluid stream entering the first heat exchange element. The second heat exchange element cools and thereby further subcools the volatile refrigerant liquid prior to the refrigerant liquid entering the first heat exchange element via a pressure reducing device. The fluid stream being cooled may be either gas or liquid and the evaporator may be of the type best adapted for the type of fluid being cooled.

Abstract: A cascade vapor compression refrigeration system having a high stage and a low stage, each stage having a compressor, evpaorator, condenser and expansion device. The high-stage evaporator is in heat transfer relationship with the low-stage condenser. There is further provided an air-to-refrigerant heat exchange element, including means for moving air over the element. The heat exchange element is connected in the discharge line of the low-stage system and is positioned to be subject to a fluctuating outoor ambient temperature. Control means are provided which are responsive to some characteristic related to outdoor temperature whereby high-stage compressor operation is permitted when the outdoor ambient is below a preset temperature and high-stage compressor operation is prevented when the outdoor ambient is above a preset temperature.

Abstract: To defrost a selected evaporator, in a system including at least two evaporators, the system condenser is isolated from the compressor and the selected evaporator receives hot, compressed refrigerant vapor directly from the compressor. The liquid refrigerant formed in the defrosting evaporator flows to the other evaporators in the system to permit them to continue in the refrigeration mode. A pressure regulated control system is provided which causes excess liquid refrigerant in the defrosted evaporator to be pumped out of that evaporator before the evaporator is reconnected to the compressor suction line. In a preferred embodiment, each evaporator includes a coil having a plurality of circuits connected between its inlet and outlet and each circuit is disposed in a horizontal plane at a different elevation from any of the other circuits.