Unloading structure for compressor of refrigeration system

Abstract

A refrigeration system including a compressor, condenser, thermal expansion valve, control for the thermal expansion valve, shell evaporator, suction line between the shell evaporator and compressor, and a control evaporator in the suction line between the shell evaporator and the control for the thermal expansion valve utilizing hot refrigerant gas from the compressor to heat the refrigerant in the suction line. The refrigeration system also includes an unloading arrangement for the compressor. In one arrangement a hot loop circuit is located directly between the outlet of the compressor and the inlet thereof and a cold loop circuit is located between the outlet and inlet of the compressor and which includes the evaporator, and both loops bypass the condenser and thus pass refrigerant from the compressor back to the compressor to thereby permit it to selectively operate in an unloaded condition in response to the load applied by the medium which is being cooled. An alternate and preferred arrangement for unloading the compressor includes a loop circuit between the outlet of the compressor and the inlet thereof which passes through an auxiliary evaporator under the main evaporator to thereby bypass the condenser and thus unload it in response to the load applied by the medium being cooled.