C02 refrigeration system with isochoric compression

Abstract

A refrigeration system includes a low temperature (LT) evaporator unit, a medium temperature (MT) evaporator unit, or both. The system further includes a LT compressor unit, an MT compressor unit, or both. The system further includes a heat exchanger, a gas cooler, an expansion valve, and a flash tank.

1 . A refrigeration system, comprising:
 a low temperature (LT) evaporator unit configured to receive a first portion of refrigerant, the LT evaporator unit comprising a LT expansion valve and a LT evaporator, wherein the LT expansion valve is configured to decrease the pressure of the first portion of refrigerant and the LT evaporator unit is configured to cool a LT space;   a LT compressor unit configured to receive the first portion of refrigerant from the LT evaporator unit, the LT compressor unit comprising at least one LT compressor configured to compress the first portion of refrigerant;   a heat exchanger that receives the first portion of refrigerant from the LT compressor unit and a second portion of refrigerant, the heat exchanger configured to transfer heat from the second portion of refrigerant to the first portion of refrigerant received from the LT compressor unit thereby producing a heated refrigerant stream and a cooled refrigerant stream;   a gas cooler configured to receive and cool the second portion of refrigerant, wherein the gas cooler is further configured to receive the cooled refrigerant stream from the heat exchanger;   an expansion valve configured to receive and decrease a pressure of refrigerant from the gas cooler; and   a flash tank configured to receive refrigerant from the expansion valve, the flash tank configured to separate the received refrigerant into a vapor refrigerant and a liquid refrigerant, wherein the LT evaporator unit is configured to receive at least a portion of the liquid refrigerant.   
     
     
         2 . The refrigeration system of  claim 1 , wherein the heat exchanger isochorically compresses the first portion of refrigerant received from the LT compressor unit to produce the heated refrigerant stream. 
     
     
         3 . The refrigeration system of  claim 1 , further comprising:
 a first valve positioned between the LT compressor unit and the heat exchanger, wherein the first valve is configured to regulate the flow rate of the first portion of refrigerant from the LT compressor unit to the heat exchanger.   
     
     
         4 . The refrigeration system of  claim 3 , wherein the first valve is a check valve, wherein the check valve restricts a backflow of the first portion of refrigerant from the heat exchanger to the LT compressor unit. 
     
     
         5 . The refrigeration system of  claim 1 , further comprising:
 a parallel compressor unit configured to receive the vapor refrigerant from the flash tank and the heated refrigerant stream from the heat exchanger;   a valve positioned between the heat exchanger and the parallel compressor, wherein the valve is configured to regulate the flow rate of the heated refrigerant from the heat exchanger to the parallel compressor.   
     
     
         6 . The refrigeration system of  claim 1 , wherein the valve positioned between the heat exchanger and the parallel compressor unit is a differential pressure valve having a threshold pressure,
 wherein, when the threshold pressure is exceeded, the differential pressure valve allows the passage of the heated refrigerant from the heat exchanger to the parallel compressor unit and, when the heated refrigerant is below the threshold pressure, the differential pressure valve restricts the flow of the heated refrigerant from the heat exchanger to the parallel compressor unit.   
     
     
         7 . A refrigeration system, comprising:
 a medium temperature (MT) evaporator unit configured to receive a first portion of refrigerant, the MT evaporator unit comprising a MT expansion valve and a MT evaporator; wherein the MT expansion valve is configured to decrease the pressure of the first portion of refrigerant and the MT evaporator unit is configured to cool a MT space;   a MT compressor unit that receives the first portion of refrigerant from the MT evaporator unit, the MT compressor unit comprising at least one MT compressor that is configured to compress the first portion of refrigerant;   a heat exchanger that receives the first portion of refrigerant from the MT compressor unit and a second portion of refrigerant, the heat exchanger configured to transfer heat from the first portion of refrigerant received from the MT compressor unit to the second portion of refrigerant thereby producing a heated refrigerant stream and a cooled refrigerant stream;   a gas cooler configured to receive and cool the first portion of refrigerant from the MT compressor unit, the gas cooler configured to cool the first portion of refrigerant, wherein the gas cooler is configured to receive the cooled refrigerant stream from the heat exchanger;   an expansion valve configured to receive and decrease a pressure of refrigerant from the gas cooler; and   a flash tank configured to receive refrigerant from the expansion valve, the flash tank configured to separate the received refrigerant into a vapor refrigerant and a liquid refrigerant, wherein the MT evaporator unit is configured to receive at least a portion of the liquid refrigerant.   
     
     
         8 . The refrigeration system of  claim 7 , wherein the heat exchanger isochorically compresses the second portion of refrigerant to produce the heated refrigerant stream. 
     
     
         9 . The refrigeration system of  claim 7 , further comprising:
 a first valve positioned downstream of the LT compressor unit, wherein the first valve is configured to regulate the flow rate of the refrigerant from the LT compressor unit.   
     
     
         10 . The refrigeration system of  claim 9 , wherein the first valve is a differential pressure valve having a threshold pressure,
 wherein, when the threshold pressure is exceeded, the differential pressure valve is configured to direct the refrigerant to the MT compressor unit and, when the refrigerant is below the threshold pressure, the differential pressure valve is configured to direct the refrigerant to the heat exchanger.   
     
     
         11 . The refrigeration system of  claim 7 , further comprising:
 a parallel compressor unit configured to receive the vapor refrigerant from the flash tank and the heated refrigerant stream from the heat exchanger;   a valve positioned between the heat exchanger and the parallel compressor, wherein the valve is configured to regulate the flow rate of the heated refrigerant from the heat exchanger to the parallel compressor.   
     
     
         12 . The refrigeration system of  claim 7 , wherein the valve positioned between the heat exchanger and the parallel compressor unit is a differential pressure valve having a threshold pressure,
 wherein, when the threshold pressure is exceeded, the differential pressure valve allows the passage of the heated refrigerant from the heat exchanger to the parallel compressor unit and, when the heated refrigerant is below the threshold pressure, the differential pressure valve restricts the flow of the heated refrigerant from the heat exchanger to the parallel compressor unit.   
     
     
         13 . The refrigeration system of  claim 7 , further comprising:
 a valve positioned between the MT compressor unit and the gas cooler, wherein the valve is configured to divert the first portion of refrigerant from the MT compressor to the heat exchanger.