Vilter Manufacturing LLC

Francis T Pallanch

A refrigeration system, and a method for operating the system, having a two-stage compressor for supplying refrigerant to a cooling coil, and having a desuperheater unit disposed between the two compressor stages. This desuperheater unit includes a container having heat exchange fluid therein and a coil, disposed in the heat exchange fluid, through which the refrigerant passes. During normal operation of the refrigeration system, both compressors are running. The desuperheater unit between the two compressor stages reduces the temperature of the compressed refrigerant before it reaches the second stage. The temperature of the heat exchange fluid is correspondingly increased in the course of the heat exchange. Also during normal operation, frost accumulates on the cooling coil, which is removed by a control device initiating a defrost cycle. When the defrost cycle begins, the first stage compressor is turned off while the second stage compressor continues to run. Flow of refrigerant is then diverted making the desuperheater coil an evaporator coil, providing load for the second stage compressor, while the cooling coil becomes the condenser. Thus, during the defrost cycle, the heat exchange fluid is cooled while the cooling coil is heated and defrosted. After defrost is completed, the flow of refrigerant is normalized, with the cooling coil again cooled and the heat exchange fluid again heated.

Defrost apparatus for refrigeration system and method of operating same

A refrigeration system comprises an evaporator which feeds uncompressed vapor to a first (low) stage compressor, a second (high) stage compressor which receives low compression vapor from the first stage and feeds high compression vapor to a condenser, and a receiver which receives liquid from the condenser and ultimately feeds it to the evaporator. Desuperheater apparatus, comprising a pressure vessel (subcooler) and a heat exchanger, is provided to remove excess heat (superheat) from the compressed vapor fed by the first stage to the second stage to thereby improve thermal efficiency of the system and to reduce the mass of refrigerant to be handled by the second stage thereby enabling use of a smaller, more economical second stage compressor. The pressure vessel contains a bath of liquid which is supplied from the receiver and then fed to the evaporator. Compressed vapor from the first stage is forced through and cooled by the liquid bath in the pressure vessel and is then fed to the second stage, along with vapor which evaporates from the liquid bath. The heat exchanger has one side through which compressed vapor from the first stage passes (and is cooled) on its way to the pressure vessel. The heat exchanger has another side through which an over-supply of liquid is pumped (or gravity fed) from the receiver and then returned to the receiver as a liquid/vapor mixture.

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Minneapolis, MN, United States of America

Francis T Pallanch