Defrost refrigeration system

Abstract

A defrost refrigeration system comprises first compressors and second compressors serially positioned with respect to one another such that refrigerant going through a compression stage in the refrigeration cycle passes sequentially through the first compressors and the second compressors. A first line extends from an exit of one of the first compressor and the second compressor of the compression stage, and is in fluid communication with the evaporator stage in a defrost cycle and is adapted to receive a defrost portion of refrigerant compressed in the compression stage. Valves switch evaporators between the refrigeration cycle and the defrost cycle, by stopping/allowing a flow of refrigerant from the condensation stage to the evaporators of the evaporation stage in the refrigeration cycle, and for allowing/stopping a flow of said defrost portion of refrigerant to defrost the evaporators in the defrost cycle.

1 . A defrost refrigeration system of the type having a main refrigeration circuit in which a refrigerant absorbs heat from an evaporator stage and releases heat in a condensation stage, with a compression stage sequentially between the evaporation stage and the condensation stage during a refrigeration cycle, said defrost refrigeration system comprising:
 at least a first compressor and a second compressor serially positioned with respect to one another such that refrigerant going through the compression stage in the refrigeration cycle passes sequentially through the first compressor and the second compressor;   a first line extending from an exit of one of the first compressor and the second compressor of the compression stage, and in fluid communication with the evaporator stage in a defrost cycle and adapted to receive a defrost portion of refrigerant compressed in the compression stage; and   valves for switching at least one evaporator between the refrigeration cycle and the defrost cycle, by stopping/allowing a flow of refrigerant from the condensation stage to at least one evaporator of the evaporation stage in the refrigeration cycle, and for allowing/stopping a flow of said defrost portion of refrigerant to defrost the at least one evaporator in the defrost cycle.   
     
     
         2 . The defrost refrigeration system according to  claim 1 , wherein the first line is positioned at the exit of the first compressor and is in fluid communication with the evaporation stage during the defrost cycle. 
     
     
         3 . The defrost refrigeration system according to  claim 2 , further comprising a second line in fluid communication between the evaporation stage and the compression stage during the defrost cycle, and valves for directing the defrost portion of refrigerant to the compression stage after defrost. 
     
     
         4 . The defrost refrigeration system according to  claim 1 , wherein the first line is positioned at the exit of the second compressor and is in fluid communication with the evaporation stage during the defrost cycle. 
     
     
         5 . The defrost refrigeration system according to  claim 4 , further comprising a pressure-reducing device on the first line for reducing a pressure of said defrost portion of refrigerant for subsequent defrost of the at least one evaporator. 
     
     
         6 . The defrost refrigeration system according to  claim 4 , further comprising a second line in fluid communication between the evaporation stage and the compression stage during the defrost cycle, and valves for directing the defrost portion of refrigerant to the compression stage after defrost. 
     
     
         7 . The defrost refrigeration system according to  claim 4 , wherein the defrost portion of refrigerant is directed to the evaporation stage after defrost to mix with refrigerant from the condensation stage to feed evaporators in the refrigeration cycle.