C02 refrigeration system with isochoric compression

Abstract

A method for operating a refrigeration system includes cooling a refrigerant using a gas cooler, decreasing the pressure of the refrigerant from the gas cooler using an expansion valve, and separating the refrigerant provided by the expansion valve into a vapor refrigerant and a liquid refrigerant using a flash tank. The method proceeds by determining whether to cool a medium temperature (MT) space or a low temperature (LT) space, and determining if heat exchange should occur for the refrigerant compressed by the MT compressor unit and the LT compressor unit, among other operations.

1 . A method of operating a refrigeration system for cooling a medium temperature (MT) space, the method comprising:
 cooling a refrigerant using a gas cooler;   decreasing the pressure of the refrigerant from the gas cooler using an expansion valve;   separating the refrigerant provided by the expansion valve into a vapor refrigerant and a liquid refrigerant using a flash tank;   transferring a portion of the liquid refrigerant from the flash tank to a MT evaporator unit;   cooling the MT space using the MT evaporator unit;   compressing the refrigerant from the MT evaporator unit using a MT compressor unit;   determining if heat exchange should occur for the refrigerant compressed by the MT compressor unit;   if heat exchange should occur for the refrigerant compressed by the MT compressor unit:
 transferring heat from a portion of the refrigerant provided by the MT compressor unit to a portion of the refrigerant provided by a low temperature (LT) compressor unit using a heat exchanger to produce a heated refrigerant stream and a cooled refrigerant stream; 
 combining the heated refrigerant stream from the heat exchanger with the vapor refrigerant stream from the flash tank; 
 compressing the heated refrigerant stream and the vapor refrigerant stream in a parallel compressor unit; 
 combining the refrigerant provided by the parallel compressor unit with the refrigerant compressed by the MT compressor unit; 
 transferring a portion of the combined refrigerant provided by the parallel compressor unit and the MT compressor unit to the gas cooler; and 
 recycling a portion of the combined refrigerant provided by the parallel compressor unit and the MT compressor unit to the heat exchanger for further heat transfer; 
   determining if further cooling is needed for the MT space; and   repeating the method if further cooling is needed.   
     
     
         2 . The method of  claim 1 , further comprising:
 determining whether to cool a low temperature (LT) space;   if cooling the LT space:
 transferring a portion of the liquid refrigerant from the flash tank to a LT evaporator unit; 
 cooling the LT space using the LT evaporator unit; 
 compressing the refrigerant from the LT evaporator unit using a LT compressor unit; and 
 determining if heat exchange should occur for the refrigerant compressed by the LT compressor unit; 
   if heat exchange should occur for the refrigerant compressed by the LT compressor unit:
 transferring heat from a portion of the refrigerant provided by the MT compressor unit to a portion of the refrigerant provided by the LT compressor unit using a heat exchanger to produce a heated refrigerant stream and a cooled refrigerant stream; 
 combining the heated refrigerant stream from the heat exchanger with the vapor refrigerant stream from the flash tank; 
 compressing the heated refrigerant stream and the vapor refrigerant stream in a parallel compressor unit; 
 combining the refrigerant provided by the parallel compressor unit with the refrigerant compressed by the MT compressor unit; 
 transferring a portion of the combined refrigerant provided by the parallel compressor unit and the MT compressor unit to the gas cooler; and 
 recycling a portion of the combined refrigerant provided by the parallel compressor unit and the MT compressor unit to the heat exchanger for further heat transfer; 
   determining if further cooling is needed for the LT space; and   repeating the method if further cooling is needed.   
     
     
         3 . The method of  claim 1 , wherein, if heat exchange should not occur for the refrigerant compressed by the MT compressor unit, then the method is repeated by cooling the refrigerant using the gas cooler. 
     
     
         4 . The method of  claim 1 , wherein, if heat exchange should not occur for the refrigerant compressed by the LT compressor unit, then the method further comprising transferring the refrigerant from the LT compressor unit to the MT compressor unit for further compression. 
     
     
         5 . The method of  claim 4 , wherein transferring the refrigerant from the LT compressor unit to the MT compressor unit is performed using a valve. 
     
     
         6 . The method of  claim 1 , further comprising transferring the cooled refrigerant stream provided by the heat exchanger to the gas cooler, wherein the cooled refrigerant stream is directed through a valve configured to regulate the flow rate of the cooled refrigerant stream. 
     
     
         7 . A method of operating a refrigeration system for cooling a low temperature (LT) space, the method comprising:
 cooling a refrigerant using a gas cooler;   decreasing the pressure of the refrigerant from the gas cooler using an expansion valve;   separating the refrigerant provided by the expansion valve into a vapor refrigerant and a liquid refrigerant using a flash tank;   transferring a portion of the liquid refrigerant from the flash tank to a LT evaporator unit;   cooling the LT space using the LT evaporator unit;   compressing the refrigerant from the LT evaporator unit using a LT compressor unit;   determining if heat exchange should occur for the refrigerant compressed by the LT compressor unit;   if heat exchange should occur for the refrigerant compressed by the LT compressor unit:
 transferring heat from a portion of the refrigerant provided by a medium temperature (MT) compressor unit to a portion of the refrigerant provided by the LT compressor unit using a heat exchanger to produce a heated refrigerant stream and a cooled refrigerant stream; 
 combining the heated refrigerant stream from the heat exchanger with the vapor refrigerant stream from the flash tank; 
 compressing the heated refrigerant stream and the vapor refrigerant stream in a parallel compressor unit; 
 combining the refrigerant provided by the parallel compressor unit with the refrigerant compressed by the MT compressor unit; 
 transferring a portion of the combined refrigerant provided by the parallel compressor unit and the MT compressor unit to the gas cooler; and 
 recycling a portion of the combined refrigerant provided by the parallel compressor unit and the MT compressor unit to the heat exchanger for further heat transfer; 
   determining if further cooling is needed for the LT space; and   repeating the method if further cooling is needed.   
     
     
         8 . The method of  claim 7 , further comprising:
 determining whether to cool a medium temperature (MT) space;   if cooling the MT space:
 transferring a portion of the liquid refrigerant from the flash tank to a MT evaporator unit; 
 cooling the MT space using the MT evaporator unit; 
 compressing the refrigerant from the MT evaporator unit using a MT compressor unit; and 
 determining if heat exchange should occur for the refrigerant compressed by the MT compressor unit; 
   if heat exchange should occur for the refrigerant compressed by the MT compressor unit:
 transferring heat from a portion of the refrigerant provided by the MT compressor unit to a portion of the refrigerant provided by the LT compressor unit using a heat exchanger to produce a heated refrigerant stream and a cooled refrigerant stream; 
 combining the heated refrigerant stream from the heat exchanger with the vapor refrigerant stream from the flash tank; 
 compressing the heated refrigerant stream and the vapor refrigerant stream in a parallel compressor unit; 
 combining the refrigerant provided by the parallel compressor unit with the refrigerant compressed by the MT compressor unit; 
 transferring a portion of the combined refrigerant provided by the parallel compressor unit and the MT compressor unit to the gas cooler; and 
 recycling a portion of the combined refrigerant provided by the parallel compressor unit and the MT compressor unit to the heat exchanger for further heat transfer; 
   determining if further cooling is needed for the MT space; and   repeating the method if further cooling is needed.   
     
     
         9 . The method of  claim 7 , wherein, if heat exchange should not occur for the refrigerant compressed by the LT compressor unit, then the method further comprising transferring the refrigerant from the LT compressor unit to the MT compressor unit for further compression. 
     
     
         10 . The method of  claim 9 , wherein transferring the refrigerant from the LT compressor unit to the MT compressor unit is performed using a valve. 
     
     
         11 . The method of  claim 8 , wherein, if heat exchange should not occur for the refrigerant compressed by the MT compressor unit, then the method is repeated by cooling the refrigerant using the gas cooler. 
     
     
         12 . The method of  claim 7 , further comprising: transferring the cooled refrigerant stream provided by the heat exchanger to the gas cooler, wherein the cooled refrigerant stream is directed through a valve configured to regulate the flow rate of the cooled refrigerant stream. 
     
     
         13 . A method of operating a refrigeration system, the method comprising:
 cooling a refrigerant using a gas cooler;   decreasing the pressure of the refrigerant from the gas cooler using an expansion valve;   separating the refrigerant provided by the expansion valve into a vapor refrigerant and a liquid refrigerant using a flash tank;   determining whether to cool a medium temperature (MT) space or a low temperature (LT) space;   if cooling the MT space:
 transferring a portion of the liquid refrigerant from the flash tank to a MT evaporator unit; 
 cooling the MT space using the MT evaporator unit; and 
 compressing the refrigerant from the MT evaporator unit using a MT compressor unit; 
   if cooling the LT space:
 transferring a portion of the liquid refrigerant from the flash tank to a LT evaporator unit; 
 cooling the LT space using the LT evaporator unit; and 
 compressing the refrigerant from the LT evaporator unit using a LT compressor unit; 
   determining if heat exchange should occur for the refrigerant compressed by the MT compressor unit and the LT compressor unit;   if heat exchange should occur:
 transferring heat from a portion of the refrigerant provided by the MT compressor unit to a portion of the refrigerant provided by the LT compressor unit using a heat exchanger to produce a heated refrigerant stream and a cooled refrigerant stream; 
 combining the heated refrigerant stream from the heat exchanger with the vapor refrigerant stream from the flash tank; 
 compressing the heated refrigerant stream and the vapor refrigerant stream in a parallel compressor unit; 
 combining the refrigerant provided by the parallel compressor unit with the refrigerant compressed by the MT compressor unit; 
 transferring a portion of the combined refrigerant provided by the parallel compressor unit and the MT compressor unit to the gas cooler; and 
 recycling a portion of the combined refrigerant provided by the parallel compressor unit and the MT compressor unit to the heat exchanger for further heat transfer; 
   determining if further cooling is needed for the MT space or the LT space; and   repeating the method if further cooling is needed.   
     
     
         14 . The method of  claim 13 , further comprising transferring the cooled refrigerant stream provided by the heat exchanger to the gas cooler. 
     
     
         15 . The method of  claim 13 , wherein, if heat exchange should not occur for the refrigerant compressed by the LT compressor unit, then the method further comprising transferring the refrigerant from the LT compressor unit to the MT compressor unit for further compression. 
     
     
         16 . The method of  claim 14 , wherein transferring the refrigerant from the LT compressor unit to the MT compressor unit is performed using a valve. 
     
     
         17 . The method of  claim 13 , wherein, if heat exchange should not occur for the refrigerant compressed by the MT compressor unit, then the method is repeated by cooling the refrigerant using the gas cooler.