Very low temperature single stage refrigeration system

Abstract

A refrigeration system and method of operating a refrigeration system having a loop comprising a compressor, a condenser, an expansion device and an evaporator, with the compressor compressing a refrigerant gas thereby heating the gas to a hot gas and the condenser removing heat from the hot gas thereby transforming the hot gas to a liquid refrigerant. The compressor has an inlet receiving gas from the evaporator and an outlet supplying hot gas to the condenser. The expansion device expands the liquid refrigerant from the condenser to a liquid-gas in the evaporator thereby absorbing heat. A heat exchanger transfers heat from the liquid refrigerant supplied to the expansion device. This increases energy density of the refrigerant.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows: 
     
         1 . A refrigeration system, comprising:
 a loop comprising a compressor, a condenser, an expansion device and an evaporator;   said compressor compressing a refrigerant gas thereby heating the gas to a hot gas and said condenser removing heat from the hot gas thereby transforming the hot gas to a liquid refrigerant, said compressor having an inlet receiving gas from the evaporator and an outlet supplying hot gas to the condenser;   said expansion device expanding the liquid refrigerant received from the condenser to a liquid-gas mixture in the evaporator thereby absorbing heat; and   a heat exchanger transferring heat from the liquid refrigerant supplied to said expansion device thereby increasing energy density of the refrigerant supplied to said evaporator.   
     
     
         2 . The refrigeration system as claimed in  claim 1  wherein said loop comprises an intermediate circuit that also cools liquid refrigerant from said condenser, said heat exchanger transferring heat from the liquid refrigerant supplied to the expansion device to the intermediate circuit refrigerant. 
     
     
         3 . The refrigerant system as claimed in  claim 2  wherein said intermediate branch cools liquid refrigerant from said condenser with another expansion device. 
     
     
         4 . The refrigerant system as claimed in  claim 3  wherein said expansion device comprises a thermally controlled expansion valve or an electronically controlled expansion valve. 
     
     
         5 . A refrigeration system, comprising:
 a loop comprising a compressor, a condenser, an expansion device and an evaporator;   said compressor compressing a refrigerant gas thereby heating the gas to a hot gas and said condenser removing heat from the hot gas thereby transforming the hot gas to a liquid refrigerant, said compressor having an inlet receiving gas from the evaporator and an outlet supplying hot gas to the condenser;   said expansion device expanding the liquid refrigerant received from the condenser to a liquid-gas mixture in the evaporator thereby absorbing heat;   a heat exchanger transferring heat from the liquid refrigerant supplied to said expansion device to an intermediate refrigerant circuit; and   wherein said compressor comprising a two-stage compressor having an intermediate injection port and said intermediate refrigerant circuit supplies refrigerant to the intermediate injection port.   
     
     
         6 . The refrigeration system as claimed in  claim 5  wherein said two-stage compressor comprises a scroll compressor. 
     
     
         7 . The refrigeration system as claimed in  claim 5  wherein said intermediate circuit also cools liquid refrigerant from said condenser with another expansion device wherein said heat exchanger comprises a primary coil connected between said condenser and said expansion device and a secondary coil that is connected between said another expansion device and said intermediate injection port. 
     
     
         8 . The refrigeration system as claimed in  claim 7  wherein said another expansion device expands refrigerant in said heat exchanger secondary coil. 
     
     
         9 . The refrigeration system as claimed in  claim 5  wherein said heat exchanger comprises a primary coil connected between said condenser and said expansion device and a secondary coil that is connected between said another expansion device and said intermediate injection port. 
     
     
         10 . The refrigeration system as claimed in  claim 9  wherein said another expansion device expands refrigerant in said heat exchanger secondary coil. 
     
     
         13 . The refrigeration system as claimed in  claim 1  that is capable of cooling to minus 50 degrees Celsius (−50° C.). 
     
     
         14 . The refrigeration system as claimed in  claim 1  that is capable of cooling to minus 70 degrees Celsius (−70° C.). 
     
     
         15 . The refrigeration system as claimed in  claim 1  wherein the transferring of heat from the liquid refrigerant supplied to said expansion device without requiring substantial change in suction pressure at said compressor inlet. 
     
     
         13 . The refrigeration system as claimed in  claim 5  that is capable of cooling to minus 50 degrees Celsius (−50° C.). 
     
     
         14 . The refrigeration system as claimed in  claim 5  that is capable of cooling to minus 70 degrees Celsius (−70° C.). 
     
     
         15 . The refrigeration system as claimed in  claim 5  wherein the transferring of heat from the liquid refrigerant supplied to said expansion device without requiring substantial change to suction pressure at said compressor inlet. 
     
     
         16 . A method of operating a refrigeration system having a loop comprising a compressor, a condenser, an expansion device and an evaporator, said compressor compressing a refrigerant gas thereby heating the gas to a hot gas, said condenser removing heat from the hot gas thereby transforming the hot gas to a liquid refrigerant, said compressor having an inlet receiving gas from the evaporator and an outlet supplying hot gas to the condenser; said expansion device expanding the liquid refrigerant received from the condenser to a liquid-gas mixture in the evaporator thereby absorbing heat with the evaporator, said method comprising:
 transferring heat from the liquid refrigerant supplied to said expansion device to increase energy density of the refrigerant supplied to said evaporator.   
     
     
         17 . A method of operating a refrigeration system, having a loop comprising a compressor, a condenser, an expansion device and an evaporator; wherein said compressor compressing a refrigerant gas thereby heating the gas to a hot gas and said condenser removing heat from the hot gas thereby transforming the hot gas to a liquid refrigerant, said compressor having an inlet receiving gas from the evaporator and an outlet supplying hot gas to the condenser; and said expansion device expanding the liquid refrigerant received from the condenser to a liquid-gas mixture in the evaporator thereby absorbing heat; said method comprising:
 transferring heat from the liquid refrigerant supplied to said expansion device to an intermediate refrigerant circuit thereby lowering evaporator pressure below ambient pressure in order to further lower the evaporation temperature;   wherein said compressor comprising a two-stage compressor having an intermediate injection port including supplying refrigerant from said intermediate refrigerant circuit to the intermediate injection port; and   regulating the refrigerant from the intermediate circuit to the intermediate injection port in order to provide sufficient refrigerant mass flow through the compressor in order to keep the discharge temperature within an acceptable range;   wherein the transferring of heat from the liquid refrigerant supplied to said expansion device and the supplying of refrigerant to the intermediate injection port achieves lower temperatures than would occur without said transferring and said supplying.