Co2 refrigeration system

Abstract

A CO 2 refrigeration system for an ice-playing surface comprises an evaporation stage in which heat is absorbed from an ice-playing surface. CO 2 compressors in a compression stage compress CO 2 refrigerant subcritically and transcritically. A gas cooling stage has a plurality of heat-reclaim units reclaiming heat from the CO 2 refrigerant. A pressure-regulating device is downstream of the gas cooling stage, to control a pressure of the CO 2 refrigerant in the gas cooling stage. A reservoir is downstream of the pressure-regulating device for receiving CO 2 refrigerant in a liquid state. A controller operates the pressure-regulating device to control the pressure of the CO 2 refrigerant in the gas cooling stage as a function of the heat demand of the plurality of heat-reclaim units, the controller causing the pressure of the CO 2 refrigerant to reach a transcritical level as a function of a heat demand of the plurality of heat-reclaim units.

1 . A method for operating a CO 2  refrigeration system for an ice-playing surface, comprising:
 operating a refrigeration cycle by sequentially compressing CO 2  refrigerant,   releasing heat from the CO 2  refrigerant in a gas cooling stage after the compressing,   absorbing heat from at least one ice-playing surface after the releasing, and   directing the CO 2  refrigerant having absorbed heat to the compressing; and   for a heat demand of a plurality of heat-reclaim units, causing the pressure of the CO 2  refrigerant to reach a transcritical level as a function of said heat demand for the plurality of heat-reclaim units to absorb heat from the CO 2  refrigerant in the gas cooling stage.   
     
     
         2 . The method according to  claim 1 , further including causing the pressure of the CO 2  refrigerant to return to a subcritical level from said transcritical level as a function of said heat demand. 
     
     
         3 . The method according to  claim 1 , wherein causing the pressure of the CO 2  refrigerant to reach a transcritical level includes controlling a pressure-regulating device downstream of the gas cooling stage. 
     
     
         4 . The method according to  claim 1 , further including accumulating CO 2  refrigerant in a liquid state in a reservoir prior to said absorbing heat. 
     
     
         5 . The method according to  claim 1 , wherein absorbing heat from at least one ice-playing surface includes circulating CO 2  refrigerant in a circuit of pipes to absorb heat from the at least one ice-playing surface. 
     
     
         6 . The method according to  claim 5 , wherein circulating CO 2  refrigerant in a circuit of pipes includes vaporizing the CO 2  refrigerant with at least one expansion valve. 
     
     
         7 . The method according to  claim 5 , wherein circulating CO 2  refrigerant in a circuit of pipes includes pumping the CO 2  refrigerant in the liquid state into the circuit of pipes. 
     
     
         8 . The method according to  claim 1 , wherein at least one of the plurality of heat-reclaim units absorbs heat from the CO 2  refrigerant in the gas cooling stage by heat exchange with a secondary refrigerant. 
     
     
         9 . The method according to  claim 8 , wherein the secondary refrigerant heats water in at least one water tank. 
     
     
         10 . The method according to  claim 1 , wherein the plurality of heat-reclaim units absorbs heat from the CO 2  refrigerant in the gas cooling stage in series. 
     
     
         11 . The method according to  claim 1 , wherein the plurality of heat-reclaim units absorbs heat from the CO 2  refrigerant in the gas cooling stage in parallel. 
     
     
         12 . The method according to  claim 1 , wherein at least one of the plurality of heat-reclaim units absorbs heat from the CO 2  refrigerant in the gas cooling stage by blowing air on a coil in which circulates the CO 2  refrigerant. 
     
     
         13 . The method according to  claim 1 , further including collecting oil downstream of said compressing, and directing the oil upstream of said compressing for the CO 2  refrigerant in said compressing to have an oil content. 
     
     
         14 . The method according to  claim 13 , wherein collecting oil includes collecting oil from a bottom of a reservoir. 
     
     
         15 . The method according to  claim 3 , wherein controlling the pressure-regulating device downstream of the gas cooling stage includes modulating a valve to maximize the heat reclaim as a function of the heat demand of the plurality of heat-reclaim units. 
     
     
         16 . The method according to  claim 1 , wherein causing the pressure of the CO 2  refrigerant to reach a transcritical level as a function of said heat demand includes causing the pressure of the CO 2  refrigerant to reach a pressure of at least 1400 Psi as a function of the heat demand during a winter month period. 
     
     
         17 . The method according to  claim 16 , wherein causing the pressure of the CO 2  refrigerant to reach a transcritical level as a function of said heat demand includes causing the pressure of the CO 2  refrigerant to reach a pressure including 550 Psi as a function of the heat demand during a summer month period, wherein an outdoor temperature is warmer in the summer month period than in the winter month period.