Refrigeration system

Abstract

Refrigeration systems are provided which include a first refrigeration system and a second refrigeration system that share a common heat exchanger. The heat exchanger includes a vessel that operates as a condenser for the second refrigeration system. A coil disposed in the vessel operates as an evaporator for the first refrigeration system. A method of operating a refrigeration system is also provided that includes exchanging energy between the refrigerant of the first refrigeration system and the refrigerant of the second refrigeration system.

1 . A refrigeration system comprising:
 a first refrigeration system configured to implement a refrigeration cycle with a first refrigerant, and   a second refrigeration system configured to implement a refrigeration cycle with a carbon dioxide refrigerant;   a heat exchanger common to the first and second refrigeration systems, the heat exchanger comprising a vessel configured to operate as a condenser for the carbon dioxide refrigerant and a coil disposed in the vessel and configured to operate as an evaporator for the first refrigerant.   
   
   
       2 . The system of  claim 1 , wherein the vessel is configured to receive vapor phase carbon dioxide refrigerant in an interior volume disposed about the coil. 
   
   
       3 . The system of  claim 2 , wherein the vessel is configured to retain a volume of liquid carbon dioxide refrigerant within the interior volume. 
   
   
       4 . The system of  claim 1 , comprising a carbon dioxide refrigeration system coupled to the vessel and configured to cool carbon dioxide refrigerant within the vessel during operation. 
   
   
       5 . The system of  claim 1 , wherein the second refrigeration system comprises an expansion device and an evaporator configured to provide cooling at an application via evaporation of liquid carbon dioxide. 
   
   
       6 . The system of  claim 5 , wherein vapor phase carbon dioxide refrigerant is directed from the evaporator to the interior volume of the vessel. 
   
   
       7 . The system of  claim 1 , wherein the second refrigeration system comprises a plurality of expansion devices associated with respective evaporators configured to provide cooling to different temperatures at a plurality of applications via evaporation of liquid carbon dioxide. 
   
   
       8 . The system of  claim 7 , wherein a circuit comprising one of the evaporators operating at a lower temperature than the other evaporator includes a compressor configured to compress vapor phase carbon dioxide refrigerant prior to returning the carbon dioxide refrigerant to the vessel. 
   
   
       9 . The system of  claim 1 , wherein the first refrigerant is an ammonia based refrigerant, a hydrocarbon based refrigerant, or a hydrofluorocarbon based refrigerant. 
   
   
       10 . A refrigeration system comprising:
 a first stage system comprising a compressor, a condenser, an expansion device and an evaporator, the first stage system configured to implement a refrigeration cycle with a first refrigerant; and   a second stage system comprising an expansion device, an evaporator, a receiver and a pump, the second stage system configured to implement a refrigeration cycle with a carbon dioxide refrigerant;   the first stage evaporator being disposed within the receiver.   
   
   
       11 . The system of  claim 10  wherein the receiver is configured to operate as a condenser for the carbon dioxide refrigerant. 
   
   
       12 . The system of  claim 10 , wherein the receiver is configured to retain a volume of liquid carbon dioxide refrigerant within an interior volume in which the first stage evaporator is disposed. 
   
   
       13 . The system of  claim 10 , comprising a carbon dioxide refrigeration system coupled to the receiver and configured to cool carbon dioxide refrigerant within the vessel during operation. 
   
   
       14 . The system of  claim 10 , wherein the second refrigeration system comprises an expansion device and an evaporator configured to provide cooling at an application via evaporation of liquid carbon dioxide. 
   
   
       15 . The system of  claim 14 , wherein vapor phase carbon dioxide refrigerant is directed from the evaporator to an interior volume of the receiver. 
   
   
       16 . The system of  claim 10  wherein the second refrigeration system comprises a plurality of expansion devices associated with respective evaporators configured to provide cooling to different temperatures at a plurality of applications via evaporation of liquid carbon dioxide. 
   
   
       17 . The system of  claim 16 , wherein a circuit comprising one of the evaporators operating at a lower temperature than the other evaporator includes a compressor configured to compress vapor phase carbon dioxide refrigerant prior to returning the carbon dioxide refrigerant to the receiver. 
   
   
       18 . A method for operating a refrigeration system, comprising:
 circulating a first refrigerant in a first refrigeration system and through a coil disposed in a vessel; and   circulating a carbon dioxide refrigerant in a second refrigeration system and through the vessel;   wherein the first refrigerant and the carbon dioxide refrigerant exchange energy with one another in the vessel to vaporize the first refrigerant in the coil and to condense the carbon dioxide refrigerant in the vessel.   
   
   
       19 . The method of  claim 18 , wherein the first refrigerant is an ammonia based refrigerant, a hydrocarbon based refrigerant, or a hydrofluorocarbon based refrigerant. 
   
   
       20 . The method of  claim 18 , comprising cooling two different applications at different temperatures via evaporation of the carbon dioxide refrigerant at two different pressures.