Abstract: A heat pump refrigeration system for refrigerating a compartment includes a first heat exchanger mounted outside the compartment, a second heat exchanger mounted inside the compartment and coupled to the first heat exchanger, and a compressor. A refrigerator conduit is coupled between the first and second heat exchangers, and between the compressor and the first and second heat exchangers, to transport refrigerant. A valve mechanism is coupled between the compressor and first and second heat exchangers. A cycle control mechanism switches the valve mechanism between two positions, one of which enables refrigerant to flow to the first and second heat exchangers in one direction and the other position enables refrigerant to flow in the opposite direction. Bypass conduits are coupled to the first and second heat exchangers to pass at least a portion of the refrigerant around the heat exchangers.

Abstract: A method of defrosting a refrigerating circuit for use in cooling a vehicular chamber comprises two steps. In a first step a frost formed at an outer surface of an evaporator of a cooling unit is defrosted by directly leading discharged gas to the evaporator. In a second step a frost formed at elements of the cooling unit except the evaporator is defrosted by making air in the vehicular chamber pass through the heated evaporator. In this manner, the cooling down characteristic in the vehicular chamber is improved and compressor durability is preserved.