Method for providing refrigeration

Details Method for providing refrigeration Method for providing refrigeration

1998-12-30

2001-01-23

Doerrler, William (Department: 3744)

Refrigeration

Cryogenic treatment of gas or gas mixture

Liquefaction

C062S114000, C062S613000

Reexamination Certificate

active

06176102

ABSTRACT:

Technical Field
This invention relates generally to refrigeration systems and is particularly advantageous for providing refrigeration to an insulated enclosure.
Background Art
The provision of refrigeration, such as for the cooling and/or freezing of foods or pharmaceuticals, is typically carried out using a mechanical refrigeration system wherein a refrigerant such as ammonia or a freon is employed in a vapor compression cycle. Such systems are effective for providing refrigeration at relatively high temperature levels but to effectively achieve low level temperature refrigeration there generally is required vacuum operation and/or cascading which increases both capital and operating costs.
One method for more effectively providing refrigeration at low temperature levels is to use an expendable cryogenic liquid, such as liquid nitrogen, either separately or in conjunction with a mechanical refrigeration system, to provide the requisite low level refrigeration. However, such systems, while effective, are expensive because of the loss of, and therefore the need for continued replacement of, the cryogenic liquid.
Accordingly, it is an object of this invention to provide a method for providing refrigeration, such as to a heat exchanger or to an insulated enclosure, which can be used to effectively provide such refrigeration, when needed, at a low 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 which is:
A method for providing refrigeration comprising:
(A) compressing a multicomponent refrigerant fluid comprising at least one component from the group consisting of fluorocarbons, hydrofluorocarbons and fluoroethers and at least one component from the group consisting of fluorocarbons, hydrofluorocarbons, fluoroethers and atmospheric gases;
(B) cooling and at least partially condensing the compressed multicomponent refrigerant fluid;
(C) expanding the at least partially condensed multicomponent refrigerant fluid to generate refrigeration; and
(D) warming and at least partially vaporizing the refrigeration bearing multicomponent refrigerant fluid and employing refrigeration from the multicomponent refrigerant fluid in an enclosure.
As used herein the term “non-toxic” means not posing an acute or chronic hazard when handled in accordance with acceptable exposure limits. As used herein the term “non-flammable” means either having no flash point or a very high flash point of at least 600°0K.
As used herein the term “on-ozone-depleting” means having zero-ozone depleting potential, i.e. having no chlorine, bromine or iodine atoms.
As used herein the term “normal boiling point” means the boiling temperature at 1 standard atmosphere pressure, i.e. 14.696 pounds per square inch absolute.
As used herein the term “indirect heat exchange” means the bringing of fluids into heat exchange relation without any physical contact or intermixing of the fluids with each other.
As used herein the term “expansion” means to effect a reduction in pressure.
As used herein the term “zeotropic” means characterized by a smooth temperature change accompanying a phase change.
As used herein the term “subcooling” means cooling a liquid to be at a temperature lower than that liquid's saturation temperature for the existing pressure.
As used herein the term “low temperature” means a temperature of 250° K or less, preferably a temperature of 200° K or less.
As used herein the term “refrigeration” means the capability to reject heat from a subambient temperature system to the surrounding atmosphere.
As used herein the term “variable load refrigerant” means a mixture of two or more components in proportions such that the liquid phase of those components undergoes a continuous and increasing temperature change between the bubble point and the dew point of the mixture. The bubble point of the mixture is the temperature, at a given pressure, wherein the mixture is all in the liquid phase but addition of heat will initiate formation of a vapor phase in equilibrium with the liquid phase. The dew point of the mixture is the temperature, at a given pressure, wherein the mixture is all in the vapor phase but extraction of heat will initiate formation of a liquid phase in equilibrium with the vapor phase. Hence, the temperature region between the bubble point and the dew point of the mixture is the region wherein both liquid and vapor phases coexist in equilibrium. In the practice of this invention the temperature differences between the bubble point and the dew point for the variable load refrigerant is at least 10° K, preferably at least 20° K and most preferably at least 50° K.
As used herein the term “fluorocarbon” means one of the following: tetrafluoromethane (CF
4
), perfluoroethane (C
2
F
6
), perfluoropropane (C
3
F
8
) perfluorobutane (C
4
F
10
), perfluoropentane (C
5
F
12
), perfluoroethene (C
2
F
4
), perfluoropropene (C
3
F
12
), perfluorobutene (C
4
F
8
), perfluoropentene (C
5
F
10
), hexafluorocyclopropane (cyclo-C
3
F
6
) and octafluorocyclobutane (cyclo-C
4
F
8
).
As used herein the term “hydrofluorocarbon” means one of the following: fluoroform (CHF
3
), pentafluoroethane (C
2
HF
5
), tetrafluoroethane (C
2
H
2
F
4
), heptafluoropropane (C
3
HF
7
), hexafluoropropane (C
3
H
2
F
6
), pentafluoropropane (C
3
H
3
F
5
), tetrafluoropropane (C
3
H
4
F
4
), nonafluorobutane (C
4
HF
9
), octafluorobutane (C
4
H
2
F
8
), undecafluoropentane (C
5
HF
11
), methyl fluoride (CH
3
F), difluoromethane (CH
2
F
2
), ethyl fluoride (C
2
H
5
F), difluoroethane (C
2
H
4
F
2
), trifluoroethane (C
2
H
3
F
3
), difluoroethene (C
2
H
2
F
2
), trifluoroethene (C
2
HF
3
), fluoroethene (C
2
H
3
F), pentafluoropropene (C
3
HF
5
), tetrafluoropropene (C
3
H
2
F
4
), trifluoropropene (C
3
H
3
F
3
), difluoropropene (C
3
H
4
F
2
), heptafluorobutene (C
4
HF
7
), hexafluorobutene (C
4
H
2
F
6
) and nonafluoropentene (C
5
HF
9
).
As used herein the term “fluoroether” means one of the following: trifluoromethyoxy-perfluoromethane (CF
3
-O-CF
3
), difluoromethoxy-perfluoromethane (CHF
2
-O-CF
3
), fluoromethoxy-perfluoromethane (CH
2
F-O-CF
3
), difluoromethoxy-difluoromethane (CHF
2
-O-CHF
2
), difluoromethoxy-perfluoroethane (CHF
2
-O-C
2
F
5
), difluoromethoxy-1,2,2,2-tetrafluoroethane (CHF
2
-O-C
2
Hf
4
), difluoromethoxy-1,1,2,2-tetrafluoroethane (CHF
2
-O-C
2
HF
4
), perfluoroethoxy-fluoromethane (C
2
F
5
-O-CH
2
F), perfluoromethoxy-1,1,2-trifluoroethane (CF
3
-O-C
2
H
2
F
3
), perfluoromethoxy-1,2,2-trifluoroethane (CF
3
O-C
2
H
2
F
3
), cyclo-1,1,2,2-tetrafluoropropylether (cyclo-C
3
H
2
F
4
-O-) cyclo-1, 1,3,3-tetrafluoropropylether (cyclo-C
3
H
2
F
4
-O-), perfluoromethoxy-1,1,2,2-tetrafluoroethane (CF
3
-O-C
2
HF
4
), cyclo-1,1,2,3,3-pentafluoropropylether (cyclo-C
3
H
5
-O-), perfluoromethoxy-perfluoroacetone (CF
3
-O-CF
2
-O-CF
3
), perfluoromethoxy-perfluoroethane (CF
3
-O-C
2
F
5
), perfluoromethoxy-1,2,2,2-tetrafluoroethane (CF
3
-O-C
2
HF
4
), perfluoromethoxy-2,2,2-trifluoroethane (CF
3
-O-C
2
H
2
F
3
), cyclo-perfluoromethoxy-perfluoroacetone (cyclo-CF
2
-O-CF
2
-O-CF
2
-) and cyclo-perfluoropropylether (cyclo-C
3
F
6
-O).
As used herein the term “atmospheric gas” means one of the following: nitrogen (N
2
), argon (Ar), krypton (Kr), xenon (Xe), neon (Ne), carbon dioxide (CO
2
), oxygen (O
2
) and helium (He).
As used herein the term “low-ozone-depleting” means having an ozone depleting potential less than 0.15 as defined by the Montreal Protocol convention wherein dichlorofluoromethane (CCl
2
F
2
) has an ozone depleting potential of 1.0.


REFERENCES:
patent: 5429760 (1995-07-01), Doering et al.
patent: 5551255 (1996-09-01), Rothfleisch
patent: 5650089 (1997-07-01), Gage et al.
patent: 5729993 (1998-03-01), Boiarski et al.
patent: 5779931 (1998-07-01), Klug et al.
patent: 5792381 (1998-08-01), Gu
patent: 5822996 (1998-10-01), Sienel et al.

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