US4237023A
Expired / Lapsed
US
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Aqueous heat-storage compositions containing fumed silicon dioxide and having prolonged heat-storage efficiencies
Assignee: Cabot Corp
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Filing: 1979-03-20
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Granted: 1980-12-02
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Expires: 1999-03-20
Abstract
Abstract Aqueous heat-storage compositions useful in space heating applications are disclosed which contain a phase-change material which absorbs and stores heat as it is heated above its phase-change temperature and releases stored heat as it is cooled below its phase-change temperature. These compositions include fumed silicon dioxide which acts as a stabilizing agent and provides dramatically prolonged heat-storage efficiency for these compositions as they undergo repetitive cycling through their phase-change temperature. Articles containing such compositions and methods of forming such compositions are additionally disclosed.
Inventors
- 👤 Timothy E. Johnson
- 👤 John Giuffrida
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 04:14
CPC Classifications
C; C09; C09K; C09K5/00; C09K5/02; C09K5/06; C09K5/063; F; F24; F24S; F24S60/00; F24S60/10; Y; Y02; Y02E; Y02E10/00; Y02E10/40; Y10; Y10S; Y10S165/00; Y10S165/902
Claims Analysis
Total Claims: 26
Claim 1
Independent Claim
72 words
In an aqueous heat-storage composition containing a phase-change material which absorbs and stores heat as it is heated above its phase-change temperature and releases stored heat as it is cooled below its phase-change temperature and a stabilizing agent to prolong heat-storage efficiency as the composition is repeatedly cycled through its phase-change temperature: the improvement wherein said stabilizing agent comprises fumed silicon dioxide uniformly dispersed throughout said composition in a stable dispersion thereof.
Claim 2
Dependent Claim
72 words
In an aqueous heat-storage composition containing a phase-change material which absorbs and stores heat as it is heated above its phase-change temperature and releases stored heat as it is cooled below its phase-change temperature and a stabilizing agent to prolong heat-storage efficiency as the composition is repeatedly cycled through its phase-change temperature: the improvement wherein said stabilizing agent comprises fumed silicon dioxide uniformly dispersed throughout said composition in a stable dispersion thereof.
Claim 3
Dependent Claim
20 words
The improvement of claim 1 wherein said fumed silicon dioxide was pyrogenically prepared by hydrolysis of a silicon halide feedstock.
Claim 4
Dependent Claim
113 words
An aqueous composition adapted to reversibly store heat energy as its temperature is raised above a predetermined temperature and to release stored heat energy as it is cooled below said predetermined temperature, comprising a uniform and stable dispersion of: an inorganic salt capable of forming a salt hydrate in said aqueous composition and having a theoretical heat-of-fusion at its phase temperature of at least about 80 BTU/lb.; a quantity of water sufficient to supply the hydration requirements of said inorganic salt in its hydrated form; and, fumed silicon dioxide present in an effective amount to significantly prolong the heat-storage efficiency of said composition as it is repetitively thermally cycled through its phase-change temperature.
Claim 5
Dependent Claim
113 words
An aqueous composition adapted to reversibly store heat energy as its temperature is raised above a predetermined temperature and to release stored heat energy as it is cooled below said predetermined temperature, comprising a uniform and stable dispersion of: an inorganic salt capable of forming a salt hydrate in said aqueous composition and having a theoretical heat-of-fusion at its phase temperature of at least about 80 BTU/lb.; a quantity of water sufficient to supply the hydration requirements of said inorganic salt in its hydrated form; and, fumed silicon dioxide present in an effective amount to significantly prolong the heat-storage efficiency of said composition as it is repetitively thermally cycled through its phase-change temperature.
Claim 6
Dependent Claim
21 words
An aqueous composition of claim 3 wherein said fumed silicon dioxide was pyrogenically prepared by hydrolysis of a silicon halide feedstock.
Claim 7
Dependent Claim
35 words
An aqueous composition of claim 4 additionally including an inorganic recrystallization temperature depressing salt which forms a eutectic mixture with said inorganic salt, said eutectic mixture having a phase-change temperature corresponding to said predetermined temperature.
Claim 8
Dependent Claim
30 words
An aqueous composition of claim 5 additionally including a nucleating agent to promote recrystallization and inhibit supercooling of said inorganic salt as said composition is cooled below its phase-change temperature.
Claim 9
Dependent Claim
13 words
An aqueous composition of claim 6 wherein said inorganic salt comprises sodium sulfate.
Claim 10
Dependent Claim
17 words
An aqueous composition of claim 7 wherein said recrystallization temperature depressing salt comprises an alkali metal halide.
Claim 11
Dependent Claim
15 words
An aqueous composition of claim 8 wherein said nucleating agent comprises an alkali metal borate.
Claim 12
Dependent Claim
14 words
An aqueous composition of claim 9 wherein said alkali metal borate is sodium borate.
Claim 13
Dependent Claim
14 words
An aqueous composition of claim 10 wherein said alkali metal halide is sodium chloride.
Claim 14
Dependent Claim
24 words
An aqueous dispersion consisting essentially of, by weight: about 37.9%--anhydrous sodium sulfate about 7.8%--sodium chloride about 2.6%--sodium borate about 3.4%--fumed silicon dioxide about 48.3%--water.
Claim 15
Dependent Claim
24 words
An aqueous dispersion consisting essentially of, by weight: about 37.9%--anhydrous sodium sulfate about 7.8%--sodium chloride about 2.6%--sodium borate about 3.4%--fumed silicon dioxide about 48.3%--water.
Claim 16
Dependent Claim
120 words
A heat-storage article comprising a water vapor-impermeable, thermally conducting container and an aqueous composition adapted to reversibly store heat energy as its temperature is raised above a predetermined temperature and to release stored heat energy as it is cooled below said predetermined temperature, said composition containing an inorganic salt capable of forming a salt hydrate in said aqueous composition and having a theoretical heat-of-fusion at its phase temperature of at least about 80 BTU/lb.; a quantity of water sufficient to supply the hydration requirements of said inorganic salt in its hydrated form; and, fumed silicon dioxide present in an effective amount to significantly prolong the heat-storage efficiency of said composition as it is repetitively thermally cycled through its phase-change temperature.
Claim 17
Dependent Claim
120 words
A heat-storage article comprising a water vapor-impermeable, thermally conducting container and an aqueous composition adapted to reversibly store heat energy as its temperature is raised above a predetermined temperature and to release stored heat energy as it is cooled below said predetermined temperature, said composition containing an inorganic salt capable of forming a salt hydrate in said aqueous composition and having a theoretical heat-of-fusion at its phase temperature of at least about 80 BTU/lb.; a quantity of water sufficient to supply the hydration requirements of said inorganic salt in its hydrated form; and, fumed silicon dioxide present in an effective amount to significantly prolong the heat-storage efficiency of said composition as it is repetitively thermally cycled through its phase-change temperature.
Claim 18
Dependent Claim
33 words
A heat-storage article of claim 13 wherein the thickness of said aqueous composition within said container is limited to a thickness which allows recrystallization of the phase-change material to occur primarily by diffusion.
Claim 19
Dependent Claim
15 words
A heat storage article of claim 14 wherein said container comprises a flexible resilient pouch.
Claim 20
Dependent Claim
18 words
A heat-storage article of claim 14 wherein said container comprises a rigid shell forming a core volume therein.
Claim 21
Dependent Claim
16 words
A heat-storage article of claims 15 or 16 wherein said inorganic salt is anhydrous sodium sulfate.
Claim 22
Dependent Claim
18 words
A heat-storage article of claim 17 wherein the maximum thickness of said core volume is about one centimeter.
Claim 23
Independent Claim
84 words
A method of forming a heat-storage composition comprising an inorganic heat-of-fusion salt having fumed silicon dioxide homogeneously dispersed therein, comprising: a. adding fumed silicon dioxide to water maintained at an elevated temperature under high shear mixing conditions to thereby form a stable, high-solids, low-viscosity aqueous predispersion of fumed silicon dioxide; and, b. adding said inorganic heat-of-fusion salt into said predispersion at an elevated temperature and under low speed mixing conditions to thereby form said homogeneous dispersion of inorganic heat-of-fusion salt and fumed silicon dioxide.
Claim 24
Independent Claim
84 words
A method of forming a heat-storage composition comprising an inorganic heat-of-fusion salt having fumed silicon dioxide homogeneously dispersed therein, comprising: a. adding fumed silicon dioxide to water maintained at an elevated temperature under high shear mixing conditions to thereby form a stable, high-solids, low-viscosity aqueous predispersion of fumed silicon dioxide; and, b. adding said inorganic heat-of-fusion salt into said predispersion at an elevated temperature and under low speed mixing conditions to thereby form said homogeneous dispersion of inorganic heat-of-fusion salt and fumed silicon dioxide.
Claim 25
Dependent Claim
14 words
A method of claim 19 wherein said inorganic heat-of-fusion salt comprises anhydrous sodium sulfate.
Claim 26
Dependent Claim
10 words
A heat-storage composition formed by the method of claim 20.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1983-12-02 | 1984-06-02 | 1984-12-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1987-12-02 | 1988-06-02 | 1988-12-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1991-12-02 | 1992-06-02 | 1992-12-02 | $7700.00 | Window Closed / Lapsed |