Compositions – Vaporization – or expansion – refrigeration or heat or energy... – With low-volatile solvent or absorbent
Reexamination Certificate
2000-09-29
2003-03-04
Ogden, Necholus (Department: 1751)
Compositions
Vaporization, or expansion, refrigeration or heat or energy...
With low-volatile solvent or absorbent
C252S067000, C062S112000, C062S476000
Reexamination Certificate
active
06527974
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an aqueous absorption fluid composition, process and apparatus providing improved water vapor absorption and thermal transfer. Addition of small quantities of certain ethers to an aqueous absorption fluid composition provides improved heat and mass transfer resulting in improved water vapor absorption and enhanced thermal and chemical stability. The compositions of this invention are particularly suited for use in high temperature stages of thermal transfer loops used in absorption refrigeration, chilling, heat pump, energy storage and other thermal transferring applications.
2. Description of Related Art
Aqueous metal halide solutions are well known as refrigerant/absorbent solutions for absorption refrigeration systems as taught by U.S. Pat. No. 3,478,530.
Alcohols have been widely used as additives in small amounts to aqueous refrigerant absorbent solutions for improved heat transfer. Octyl alcohol in LiBr solutions is taught by U.S. Pat. Nos. 3,276,217 and 4,857,222; certain secondary alcohols in LiBr solutions are taught by U.S. Pat. Nos. 3,609,087 and 4,315,411; certain tertiary alcohols are taught by U.S. Pat. No. 3,580,759; and fluoroalcohols are taught by U.S. Pat. No. 3,783,631.
Amines have been used as additives in small amounts to aqueous absorption systems for increased rate of water vapor sorption of working fluid as taught by U.S. Pat. Nos. 5,419,145; 5,577,388 and 5,829,259, for example.
Certain ethers are known as solvents for refrigerant methyl chloride used in absorption refrigeration as taught by U.S. Pat. No. 2,040,905.
The polyfunctional ethers, ethylene glycol monobutyl ether and diethylene glycol monobutyl ether, in amounts of 0.001 to 1.0 percent by weight, in concentrated lithium halide aqueous solutions are known as vapor pressure depressants for use in absorption refrigeration systems, as taught by U.S. Pat. No. 3,553,136.
The use of polyfunctional ether, specifically tetraethylene glycol dimethylether, as an absorbent in conjunction with an azeotropic mixture of trifluoroethanol and water as a cooling medium is taught by Japanese Patent Number 61-14282 to afford a wider temperature range of a cycle than a water/LiBr system in absorption refrigeration.
An absorption fluid of aqueous solutions of metal salts of alkali metal hydroxides, nitrites, and alkaline earth and transition metal hydroxides, halides and thiocyanates and about 10 to about 30 weight percent, based on the metal salt, of an organic compound including ethers, particularly alkaline glycol ethers is taught by U.S. Pat. No. 5,529,709 to provide increased absorbent solubility and vapor pressure reduction.
SUMMARY OF THE INVENTION
It is an object of this invention to provide an improved aqueous absorption fluid composition and process for thermal transfer having increased rates of water vapor absorption to result in improved thermal transfer.
It is another object of this invention to provide an improved aqueous absorption fluid composition and process for thermal transfer which allows use of reduced absorber size to obtain a specified thermal transfer.
Yet another object of this invention is to provide an aqueous absorption fluid composition which exhibits high stability to thermal decomposition and chemical reactivity to other components of the composition.
In particular, the general object of the invention can be attained, at least in part and in accordance with one embodiment of the invention, through an absorption fluid composition which includes aqueous refrigerant, at least one metal halide salt absorbent present in an amount to provide a composition useful as a refrigerant/absorbent and at least one monofunctional ether heat and mass transfer additive normally liquid at system operating conditions and present in an amount effective as an absorption promoter.
The invention further comprehends an improvement in a process for thermal transfer using an absorption fluid which includes an aqueous metal halide salt refrigerant/absorbent composition. In accordance with one embodiment of such invention, such improvement relates to obtaining an increased rate of water vapor absorption in the absorption fluid via adding thereto an absorption promoting amount of at least one monofunctional ether heat and mass transfer additive normally liquid at system operating conditions.
The invention still further comprehends an improved apparatus for absorption thermal storage, cooling or heating of the type containing an absorption fluid which includes aqueous refrigerant and at least one metal halide salt absorbent present in an amount to provide a composition useful as a refrigerant/absorbent. In accordance with one preferred embodiment, such improvement relates to the absorption fluid additionally including an absorption promoting amount of at least one monofunctional ether heat and mass transfer additive normally liquid at system operating conditions.
The above objects and other advantages of this invention which will become apparent upon reading this disclosure are achieved by addition of parts per million amounts of certain ethers to aqueous absorption fluids.
As used herein, references to “monofunctional” ether heat and mass transfer additives are to be understood to refer to such ether additives that contain or include only a single organic functional group, i.e., a single ether chemical group. The term “organic functional group” is not meant to include aliphatic and aromatic hydrocarbon groups such as phenyl, butyl, hexyl and the like. It is to be understood, however, that a monofunctional ether as used herein may, in certain preferred embodiments, be at least partially fluorinated such as to contain one or more fluorine groups.
Further, references herein to “polyfunctional” ether or other additive material are to be understood to refer to such an additive material which contains or includes two or more organic functional groups, wherein the two or more organic functional groups can be of the same or different type. Examples of polyfunctional additives include: ethylene glycol (i.e., contains or includes two alcohol functional groups), diethylene glycol (ether) (i.e., contains or includes one ether and two alcohol functional groups), ethylene glycol monobutyl ether (i.e., contains or includes one ether and one alcohol functional group), diethylene glycol dibutyl ether, (i.e., contains or includes three ether functional groups), diethylene glycol monobutyl ether acetate (i.e., contains or includes two ether and one ester functional groups), and monophenyl glycol ether acetate (i.e., contains or includes one ether and one ester functional group).
Components in the working fluid of an absorption thermal transfer cycle include chemicals which classified according to their use are defined in the art as follows:
“Refrigerant” is the chemical which vaporizes and condenses, or is absorbed, in large volume and the energy associated with this phase change being the essence of the system thermodynamics. In this invention water is the principal refrigerant.
“Absorbent” is the chemical(s) which have relatively low volatilities compared to the refrigerant, and high affinities for the refrigerant. Many suitable absorbents known to the art are suitable for use in this invention, such as those disclosed in U.S. Pat. No. 3,478,530, which is incorporated herein by reference. Lithium, zinc and calcium bromides and chlorides are among suitable absorbents. Lithium bromide compositions are most frequently used in large commercial refrigeration equipment. The properties of the refrigerant and to absorbent(s) together in a refrigerant/absorbent(s) composition define the theoretical limits of the equilibrium thermodynamics of the absorption system. In this invention suitable absorbent(s) are at least one metal salt which is present in an amount sufficient to provide a composition functional as a refrigerant/absorbent(s) composition. Any of the above mentioned salts or combinations of salts, and also salts in combination with other non-interf
Fejer Mark E.
Gas Research Institute
Ogden Necholus
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