Aqueous heat-storage compositions containing fumed silicon dioxide and having prolonged heat-storage efficiencies
First Claim
1. 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.
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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.
64 Citations
21 Claims
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1. 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. - View Dependent Claims (2)
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3. 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:
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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. - View Dependent Claims (4, 5, 6, 7, 8, 9, 10, 11)
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12. An aqueous dispersion consisting essentially of, by weight:
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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.
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13. 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. - View Dependent Claims (14, 15, 16, 17, 18)
- a quantity of water sufficient to supply the hydration requirements of said inorganic salt in its hydrated form; and
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19. A method of forming a heat-storage composition comprising an inorganic heat-of-fusion salt having fumed silicon dioxide homogeneously dispersed therein, comprising:
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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. - View Dependent Claims (20, 21)
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Specification