Variable load refrigeration system particularly for...

Details Variable load refrigeration system particularly for... Variable load refrigeration system particularly for...

2000-04-07

2002-07-30

Einsmann, Margaret (Department: 1751)

Compositions

Vaporization, or expansion, refrigeration or heat or energy...

C062S606000

Reexamination Certificate

active

06426019

ABSTRACT:

TECHNICAL FIELD
This invention relates generally to refrigeration and, more particularly, to the use of multiple component refrigerant fluids useful for generating refrigeration. The invention is particularly useful for providing refrigeration down to cryogenic temperatures.
BACKGROUND ART
Refrigeration is conventionally generated by compressing and then expanding a refrigerant fluid within a refrigeration circuit. Well known examples of such conventional systems include refrigerators and air conditioners. Typically the refrigerant is a single component fluid which undergoes a phase change at a required temperature from a liquid to a gas thus making its latent heat of vaporization available for cooling purposes. The efficiency of the conventional system can be improved by using a multiple component fluid as the refrigerant which can provide variable amounts of refrigeration over a required temperature range. However, known multiple component fluid refrigeration cycles cannot effectively provide refrigeration over a large temperature range down to colder cryogenic temperatures. Moreover, most well known refrigerant fluids are toxic, flammable and/or ozone depleting.
Accordingly it is an object of this invention to provide a method for generating refrigeration using a multiple component refrigerant fluid which can provide refrigeration over a large temperature range down to cryogenic temperatures.
It is another object of this invention to provide a multiple component refrigerant fluid which is non-toxic, non-flammable, and low or non-ozone-depleting.
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 refrigeration comprising:
(A) compressing a variable load refrigerant mixture 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, hydrochlorofluorocarbons, fluoroethers, atmospheric gases and hydrocarbons to produce a compressed variable load refrigerant mixture;
(B) cooling the compressed variable load refrigerant mixture to produce a cooled compressed variable load refrigerant mixture;
(C) expanding the cooled, compressed variable load refrigerant mixture and generating refrigeration to produce a lower temperature variable load refrigerant mixture; and
(D) warming the lower temperature variable load refrigerant mixture.
Another aspect of the invention is:
A refrigerant mixture which is non-toxic, non-flammable and low-ozone-depleting 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, hydrochlorofluorocarbons, fluoroethers, atmospheric gases and hydrocarbons.
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
6
), 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 “hydrochlorofluorocarbon” means one of the following: chlorodifluoromethane (CHClF
2
), chlorofluoromethane (CH
2
ClF), chloromethane (CH
3
Cl), dichlorofluoromethane (CHCl
2
F), chlorotetrafluoroethane (C
2
HClF
4
), chlorotrifluoroethane (C
2
H
2
ClF
3
), chlorodifluoroethane (C
2
H
3
ClF
2
), chlorofluoroethane (C
2
H
4
ClF), chloroethane (C
2
H
5
Cl), dichlorotrifluoroethane (C
2
HCl
2
F
3
), dichlorodifluoroethane (C
2
H
2
Cl
2
F
2
), dichlorofluoroethane (C
2
H
3
Cl
2
F), dichloroethane (C
2
H
4
Cl
2
), trichlorofluoroethane (C
2
H
2
Cl
3
F), trichlorodifluoroethane (C
2
HCl
3
F
2
), trichloroethane (C
2
H
3
Cl
3
), tetrachlorofluoroethane (C
2
HCl
4
F), chloroethene (C
2
H
3
Cl), dichloroethene (C
2
H
2
Cl
2
), dichlorofluoroethene (C
2
H
2
ClF) and dichlorodifluoroethene (C
2
HClF
2
).
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
), perfluoroethoxyfluoromethane (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 “hydrocarbon” means one of the following: hydrogen (H
2
), methane (CH
4
), ethane (C
2
H
6
), ethene (C
2
H
4
), propane (C
3
H
8
), propene (C
3
H
6
), butane (C
4
H
10
), butene (C
4
H
8
), cyclopropane (C
3
H
6
) and cyclobutane (C
4
H
8
).
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° K.
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