Abstract: A heat pump apparatus has a main refrigerant circuit constituted by a closed loop including a compressor, condenser, gas-liquid separator, pressure reducer such as an expansion valve, and an evaporator. A shunting refrigerant line having a compressor, condenser and a pressure reducer means shunts from the gaseous phase portion of the gas-liquid separator of the main refrigerant circuit and merges in the evaporator of the main refrigerant circuit. The shunting refrigerant line may be constructed to have one or more compression stages.

Abstract: A heat exchanger fin according to the invention has a multiplicity of fins arranged substantially in parallel with the direction of air flow and at least one heat transfer tube to which said fins are connected in a heat conducting relation. A multiplicity of louvers inclined by a small angle to the direction of air flow are formed in said fins.According to this construction, it is possible that the air as a whole can flow substantially straight across the heat exchanger and can strongly collide with all louvers, thereby to ensure a reduced flow resistance encountered by the air flow, as well as improved heat transfer performance of the heat exchanger.

Abstract: A refrigerating apparatus including a first compressor, a condenser, a first pressure reducer a first evaporator, a second pressure reducer and a second evaporator connected together by lines to form a refrigerating circuit for a refrigerant to flow therethrough, wherein a second compressor is connected at its suction side to the second pressure reducer for receiving gaseous component of refrigerant from the first evaporator and connected at its discharge side to the line between the first compressor and the condenser. An evaporative pressure control valve may be mounted in the line between the first evaporator and the second pressure reducer or the line between the second pressure reducer and the second evaporator. A bypass line mounting an electromagnetic valve may connect the line between the first evaporator and the second pressure reducer to the line between the second pressure reducer and the second evaporator.

Abstract: An air cooling apparatus having a cooler including a plurality of fins arranged in substantially parallel relationship with a predetermined spacing therebetween and heat transfer tubes extending through the fins in a plurality of positions in the fins is further provided with at least one defrosting device having a plurality of projecting members of a width slightly smaller than the spacing between the fins which projecting members are each located between the adjacent two fins. The defrosting device is mounted for rotation about the heat transfer tubes and operative to remove frost from the surfaces of the cooler while rotating which frost has been formed during the operation of the air cooler.