Co2 refrigeration system

Abstract

A CO 2 refrigeration system comprises a refrigeration circuit in which circulates CO 2 refrigerant between a compression stage in which the CO 2 refrigerant is compressed. A condensation stage is provided in which the CO 2 refrigerant releases heat and is accumulated in a condensation reservoir. An evaporation stage is provided in which the CO 2 refrigerant is expanded to a gaseous state to absorb heat from a fluid for refrigeration, with at least a portion of CO 2 refrigerant exiting the evaporation stage being directed to a supra-compression circuit comprising a supra-compression stage in which the portion of CO 2 refrigerant is compressed. A heat exchanger is provided by which the compressed CO 2 refrigerant is in a heat-exchange relation with a secondary-refrigerant circuit, such that the compressed CO 2 refrigerant releases heat to a secondary refrigerant used for heating purposes. Pressure-regulating means control a pressure of the compressed CO 2 refrigerant being returned to the condensation stage.

1 .- 23 . (canceled) 
     
     
         24 . A CO 2  refrigeration system comprising: a refrigeration circuit in which circulates CO 2  refrigerant between at least one compression stage in which the CO 2  refrigerant is compressed, a gas cooling stage in which the compressed CO 2  refrigerant releases heat, a condensation reservoir in which a portion of the CO 2  refrigerant is accumulated in a liquid state, a pressure-regulating unit in a line between the gas cooling stage and the condensation reservoir, an evaporation stage in which the CO 2  refrigerant from the condensation reservoir absorbs heat from a fluid for refrigeration; and a defrost circuit comprising a defrost line extending from the at least one compression stage to the evaporation stage for directing compressed CO 2  refrigerant to at least one evaporator of the evaporation stage to absorb heat in defrosting the at least one evaporator. 
     
     
         25 . The CO 2  refrigeration system according to  claim 24 , wherein the defrost circuit comprises at least one defrost accumulator connected to the at least one evaporator for receiving the CO 2  defrost refrigerant exiting the at least one evaporator prior to returning the CO 2  defrost refrigerant to the refrigeration circuit. 
     
     
         26 . The CO 2  refrigeration system according to  claim 25 , further comprising a line between the defrost accumulator and the condensation reservoir to return the CO 2  defrost refrigerant to the condensation reservoir. 
     
     
         27 . The CO 2  refrigeration system according to  claim 24 , wherein the at least one compression stage comprises a first CO 2  compression stage, a CO 2  supra-compression stage, with the defrost line directing CO 2  defrost refrigerant from either one of the compression stages to the at least one evaporator for defrost. 
     
     
         28 . The CO 2  refrigeration system according to  claim 27 , wherein the defrost line directs CO 2  defrost refrigerant from the CO 2  supra-compression stage to the at least one evaporator for defrost, with a pressure-control unit in the defrost line to reduce a pressure of the CO 2  defrost refrigerant. 
     
     
         29 . The CO 2  refrigeration system according to  claim 25 , further comprising a line between the at least one evaporator, and the first CO 2  compression stage, for returning the CO 2  defrost refrigerant to the refrigeration circuit. 
     
     
         30 . The CO 2  refrigeration system according to  claim 27 , further comprising a suction accumulator between the compression stages, with a portion of the CO 2  refrigerant exiting the first CO 2  compression stage being directed to the CO 2  supra-compression stage via the suction accumulator. 
     
     
         31 . The CO 2  refrigeration system according to  claim 30 , further comprising a line between the at least one evaporator, and the suction accumulator between the compression stages, for returning the CO 2  defrost refrigerant to the refrigeration circuit. 
     
     
         32 . The CO 2  refrigeration system according to  claim 30 , further comprising another suction accumulator upstream of the first compression stage to separate liquid and gaseous portions from the CO 2  refrigerant such that gaseous CO 2  refrigerant is fed to the first compression stage. 
     
     
         33 . The CO 2  refrigeration system according to  claim 32 , wherein the other suction accumulator receives an other portion of the CO 2  refrigerant exiting the evaporation stage to then feed said other portion of the CO 2  refrigerant to the first compression stage. 
     
     
         34 . The CO 2  refrigeration system according to  claim 32 , wherein the suction accumulator between compression stages receives CO 2  refrigerant exiting medium-temperature evaporators of the evaporation stage, and wherein the other suction accumulator receives CO 2  refrigerant exiting low-temperature evaporators of the evaporation stage. 
     
     
         35 . The CO 2  refrigeration system according to  claim 27 , further comprising a suction accumulator upstream of the first compression stage to accumulate CO 2  refrigerant being fed to the compression stage, the suction accumulator connected to the evaporators so as to receive at least a portion of the CO 2  defrost refrigerant exiting from the at least one evaporator. 
     
     
         36 . The CO 2  refrigeration system according to  claim 27 , further comprising a line between the at least one evaporator and the condensation reservoir to return the CO 2  defrost refrigerant to the condensation reservoir. 
     
     
         37 . The CO 2  refrigeration system according to  claim 24 , further comprising a pump between the condensation reservoir and the evaporation stage to direct CO 2  refrigerant to the evaporation stage. 
     
     
         38 . The CO 2  refrigeration system according to  claim 24 , further comprising a pressure-relief system for the evaporators of the evaporation stage, the pressure relief system exhausting CO 2  refrigerant from any one of the evaporators when a pressure of refrigerant in the refrigeration coil reaching a given threshold. 
     
     
         39 . The CO 2  refrigeration system according to  claim 32 , further comprising a pressure-relief system for the evaporators of the evaporation stage, the pressure-relief system exhausting defrost CO 2  refrigerant from any one of the evaporators when a pressure of refrigerant in the refrigeration coil reaching a given threshold, the pressure-relief system directing excess-pressure defrost CO 2  refrigerant to any one of the suction accumulators. 
     
     
         40 . The CO 2  refrigeration system according to  claim 32 , further comprising a pressure-relief valve for the one of the suction accumulators receiving the excess-pressure defrost CO 2  refrigerant. 
     
     
         41 . The CO 2  refrigeration system according to  claim 24 , further comprising a line between the evaporation stage and the compression stage to return the CO 2  defrost refrigerant to the compression stage. 
     
     
         42 . The CO 2  refrigeration system according to  claim 41 , further comprising a heat exchanger in said line to vaporize the CO 2  defrost refrigerant returning to the compression stage.