Refrigeration – Air compressor – cooler and expander type
Reexamination Certificate
2000-05-01
2001-06-26
Doerrler, William (Department: 3744)
Refrigeration
Air compressor, cooler and expander type
C062S088000, C062S402000
Reexamination Certificate
active
06250096
ABSTRACT:
TECHNICAL FIELD
This invention relates generally to the provision of refrigeration and is particularly useful for the provision of refrigeration at a very cold temperature.
BACKGROUND ART
Historically, refrigeration systems have used various fluorocarbons and hydrofluorocarbons as refrigerant fluids to generate refrigeration and to provide the refrigeration to a heat load. Recently the use of some such refrigerants has been questioned on environmental and other grounds. Systems which use an environmentally friendly working fluid, such as air, are known. However, such systems typically are less efficient than systems using the more conventional refrigerants. For example, air systems commonly have a pinch at the warm end of the heat exchanger used in the system which limits the refrigeration capacity of the system. This is particularly a problem when the provision of the refrigeration is desired at a very cold temperature.
Accordingly it is an object of this invention to provide an improved method for generating a cold gas for the provision of refrigeration.
It is another object of this invention to provide an improved method for generating a cold gas for the provision of refrigeration which employs an environmentally benign working fluid.
It is a further object of this invention to provide an improved method for generating a cold gas for the provision of refrigeration which employs an environmentally benign working fluid and can efficiently provide the refrigeration at a very cold temperature.
SUMMARY OF THE INVENTION
The above and other objects, which will become apparent to those skilled in the art upon a reading of this disclosure, are attained by the present invention, one aspect of which is:
A method for generating a cold gas for supplying refrigeration comprising:
(A) compressing a nitrogen-containing working gas and cooling the compressed nitrogen-containing working gas;
(B) expanding the cooled nitrogen-containing working gas to produce a cold nitrogen-containing working gas, and warming the cold nitrogen-containing working gas to supply refrigeration to a heat load;
(C) further warming the nitrogen-containing working gas by indirect heat exchange with the compressed nitrogen-containing working gas to effect a portion of said cooling of the compressed nitrogen-containing working gas; and
(D) compressing a refrigerant fluid, expanding the compressed refrigerant fluid to cool the refrigerant fluid, and warming the cooled refrigerant fluid by indirect heat exchange with the compressed nitrogen-containing working gas to effect another portion of said cooling of the compressed nitrogen-containing working gas.
Another aspect of the invention is:
A method for generating a cold gas for supplying refrigeration comprising:
(A) compressing a nitrogen-containing working gas and cooling the compressed nitrogen-containing working gas;
(B) expanding the cooled nitrogen-containing working gas to produce a cold nitrogen-containing working gas;
(C) warming a first portion of the cold nitrogen-containing working gas to supply refrigeration to a heat load; and
(D) warming a second portion of the cold nitrogen-containing working gas by indirect heat exchange with the compressed nitrogen-containing working gas to effect said cooling of the compressed nitrogen-containing working gas.
As used herein the term “very cold temperature” means a temperature within the range of from −30° F. to −300° F.
As used herein the term “nitrogen-containing working gas” means a gas having a nitrogen concentration of at least 78 mole percent.
As used herein the term “expansion” means to effect a reduction in pressure.
As used herein the term “refrigeration” means the capability to reject heat from a subambient temperature system.
As used herein the terms “turboexpansion” and “turboexpander” mean respectively method and apparatus for the flow of high pressure fluid through a turbine to reduce the pressure and the temperature of the fluid thereby generating refrigeration.
As used herein the term “refrigerant fluid” means a pure component or mixture used as a working fluid in a refrigeration process which undergoes changes in temperature, pressure and possibly phase to absorb heat at a lower temperature and reject it at a higher temperature.
REFERENCES:
patent: 2030509 (1936-02-01), Frankl
patent: 3856493 (1974-12-01), Bulkley
patent: 4924677 (1990-05-01), Quack
patent: 5392606 (1995-02-01), Labinov et al.
Acharya Arun
Bonaquist Dante Patrick
Cheung Harry
Doerrler William
Ktorides Stanley
Praxair Technology Inc.
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