Abstract: A compression type refrigeration system including at least one frosting evaporator positioned to refrigerate air. The evaporator has a liquid refrigerant inlet to which is connected an expansion valve. The evaporator also has a hot gas inlet; a liquid line supplies liquid to the expansion valve; a branch in the liquid line controlled by a solenoid valve connects to the hot gas inlet. The condensing unit, which includes compressor, condenser, receiver and re-evaporator, are valve-controlled so that during refrigeration, discharge gas from the compressor flows through the condenser, receiver, liquid line and expansion valve seriatim, but during defrost, gas from the compressor bypasses the condenser and flows instead from the compressor through the receiver, liquid line and hot gas inlet of the evaporator seriatim.

Abstract: A compression type refrigeration system including at least one frosting evaporator positioned to refrigerate air. The evaporator has a liquid refrigerant inlet to which is connected an expansion valve. The evaporator also has a hot gas inlet; a liquid line supplies liquid to the expansion valve; a branch in the liquid line controlled by a solenoid valve connects to the hot gas inlet. The condensing unit, which includes compressor, condenser, receiver and re-evaporator, are valve-controlled so that during refrigeration, discharge gas from the compressor flows through the condenser, receiver, liquid line and expansion valve seriatim, but during defrost, gas from the compressor bypasses the condenser and flows instead from the compressor through the receiver, liquid line and hot gas inlet of the evaporator seriatim.

Abstract: A suction accumulator for refrigeration systems having a tank with an inlet fitting for conveying it to refrigerant vapor from the evaporator which is mixed with oil and at times with liquid refrigerant. The tank has an outlet fitting for conveying away the refrigerant vapor from which the oil and liquid refrigerant have been separated. An oil return conduit is located underneath the tank. One end of the oil return conduit is connected into the bottom of the tank; the other end to the outlet fitting of the accumulator. Located within this oil return conduit is a thermostatic expansion valve whose bulb is located on the oil return conduit between the tank and the expansion valve. This bulb senses low superheat when liquid refrigerant is in the tank and in the conduit, and causes the expansion valve to close when liquid refrigerant is present, preventing the flow of large amounts of the liquid refrigerant into the outlet conduit.