JPH0680957A - Heat storage composition - Google Patents

Abstract

PURPOSE:To obtain the title compsn. having an m. p. near room temp., a large amt. of latent heat, and an excellent long-term stability in heat cycle by specifying the molar ratio of water of crystallization to sodium sulfate. CONSTITUTION:The title compsn. having long-term stability in repeated solidifying and melting cycle is obtd. by adjusting the molar ratio of water to anhydrous sodium sulfate to 9. 4-6. 5 by adding anhydrous sodium sulfate to sodium sulfate decahydrate. The compsn. may further contain at least one inorg. salt (e.g. ammonium chloride, ammonium bromide, or sodium chloride) as a solidification point adjusting agent, at least one supercooling preventive selected from the group consisting of borax, a silicate, and cryolite, and at least one phase separation preventive selected from the group consisting of CMC. attapulgite, and a water-absorbing acrylic resin. The compsn. has a large amt. of latent heat, is excellent in long-term thermal stability, and is suitable for using at room temp. or for air conditioning because it's m. p. is near room temp.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for modifying sodium sulfate decahydrate and / or a eutectic salt of sodium sulfate, which are often used in latent heat storage materials, to be suitable for use in heat storage materials. The present invention relates to a heat storage material composition section.

[0002]

2. Description of the Related Art Sodium sulfate decahydrate has been generally used as a latent heat storage material near room temperature because it is inexpensive, easily available in large quantities, and has a large latent heat quantity. The invention relating to the molar ratio of water to sodium sulfate in a sodium sulfate decahydrate-based composition has hitherto been described as a composition comprising 130 to 190 parts by weight of water with respect to 100 parts by weight of sodium sulfate decahydrate (Japanese Patent Laid-Open Publication No. Sho. 60-202183 Director of Industrial Technology), 35 parts by weight of water is added to 100 parts by weight of sodium sulfate decahydrate to obtain a saturated aqueous solution of sodium sulfate (Japanese Patent Publication No. 15549 Shikoku Kasei Kogyo).
In any of the inventions, sodium sulfate decahydrate was not completely dissolved in its own water of crystallization at the melting point and became a saturated solution of anhydrous sodium sulfate and sodium sulfate. Is dissolved in. However, sodium sulfate decahydrate causes supercooling phenomenon and phase separation phenomenon, and a supercooling inhibitor and a phase separation inhibitor have been developed for practical use. As a supercooling inhibitor, borax (N
a ₂ B ₄ O ₇ · 10H ₂ O), silicates, cryolite, etc. as phase separation inhibitors, among others, sawdust, sawdust, pulp, various fibrin mixtures, starch, alginic acid, silica gel, diatomaceous earth, Water-soluble resins and superabsorbent resins have been investigated.

[0003]

There is a need for a sodium sulfate decahydrate-based composition having long-term thermal recycling stability.

[0004]

MEANS FOR SOLVING THE PROBLEMS The present invention provides "1. A sodium hydrate of sodium sulfate decahydrate and another sodium sulfate hydrate different in water of crystallization and anhydrous sodium sulfate. Is 9.4 ~
The heat storage material composition which is 6.5. 2. The heat storage material composition according to item 1, wherein the other sodium sulfate having a different crystal water is sodium sulfate heptahydrate. 3. The heat storage material composition according to item 1 or 2, wherein one or more inorganic salts other than sodium sulfate is added as a freezing point modifier. 4. 1 or 2 or more selected from borax, silicate, and cryolite as a supercooling inhibitor, and CMC as a phase separation inhibitor,
1 selected from Atta Pulsh clay and acrylic water absorbent resin
Or any one of the items 1 to 3 in which 2 or more are blended
The heat storage material composition described in the item. Regarding

The present inventors have conducted intensive studies to develop a heat storage material composition having a melting temperature near room temperature, which has a large latent heat amount and is excellent in long-term thermal stability, which is suitable for room temperature and cooling, and as a result, sodium sulfate was found. Anhydrous sodium sulfate (Na ₂ SO ₄ ) is added to decahydrate (Na ₂ SO ₄ · 10H ₂ O), and the molar ratio of water to anhydrous sodium sulfate is 9.4 to 6.5. It was found that the resulting composition is stable against long-term solidification / melting recycling. Further, it may contain one or more other inorganic salts such as ammonium chloride, ammonium bromide and sodium chloride as a freezing point modifier, and is usually used in sodium sulfate-based compositions such as borax, silicate and cryolite. A supercooling inhibitor may be added, and as a rule, sawdust, sawdust, pulp, various fiber mixtures, starch,
Alginic acid, silica gel, diatomaceous earth, water-soluble resin or crosslinked polyacrylic acid salt, starch graft polymer, cellulose graft polymer, vinyl acetate-acrylic acid ester copolymer partially saponified product, crosslinked polyvinyl alcohol, crosslinked polyethylene A phase separation inhibitor such as a highly water-absorbent resin such as oxide may be added.

[0006]

The present invention is premised on the operation of a heat storage system called a capsule type. For practical use, it is necessary to prevent phase separation and stabilize long-term heat recycling performance. The cooling period is 3 months / year, and heat storage and heat radiation is repeated about 100 times a year. In order to be maintenance-free for 10 years after installing the heat storage system, it is necessary to maintain the initial performance even after at least 1000 heat cycles.
Therefore, in the present invention, a composition in which the molar ratio of water to sodium sulfate is 9.4 to 6.5 does not cause phase separation because excess water does not exist in the system, and exhibits stable performance in long-term heat recycling. I found that.

The present invention has been studied for the purpose of preventing phase separation and improving long-term heat recycling performance. As a result, the molar ratio of water to sodium sulfate is adjusted to 9.4 to 6.5, whereby coagulation and It was found that the surplus water in the melt recycling was eliminated and the repeatability was stable. Sodium sulfate is most stable in the decahydrate salt, but in the unstable state where coagulation and melting are repeated, many metastable heptahydrate salts are present, and it is considered that surplus water is present. However, 1
It is not that there is no zero hydrate salt, and it is very difficult to determine the abundance ratio of anhydrous sodium sulfate, heptahydrate and decahydrate. However, according to the research conducted by the present inventor, it has been confirmed that sodium sulfate anhydrous, heptahydrate and decahydrate exist, and the present inventor has such a composition. It is considered that when the molar ratio of is adjusted to 9.4 to 6.5, excess water is not generated during coagulation and melting / recycling, and the repeating performance is stable.

Although it is difficult to determine the abundance ratio of heptahydrate, the molar ratio of water to sodium sulfate is 9.4 to 6.
It was found that adjusting to 5 eliminates the generation of excess water in the system, makes phase separation less likely to occur, and eliminates the generation of excess water, resulting in a sharp melting pattern. When the molar ratio of water of crystallization to sodium sulfate is larger than 9.4, it is the same as decahydrate, and when it is smaller than 6.5, anhydrous sodium sulfate is precipitated. Preferably,
9.0-7.0 mol, more preferably 8.5-7.5.
Mole gives good results.

As a method for obtaining a composition in which the molar ratio of sodium sulfate to water is 9.4 to 6.5, water is added to anhydrous sodium sulfate or sodium sulfate 10
There is no limitation on the method of making it, such as by forming a mixture of hydrated salt, anhydrous sodium sulfate and water.

[0010]

【Example】

Examples 1 to 3 anhydrous sodium sulfate, ammonium chloride, ammonium bromide, sodium chloride and water as freezing point modifiers,
37.4-10-5-5-52.6% by weight, 39.
2-10-5-5-40.8% by weight and 42.4-1
It was prepared to be 0-5-5-37.6% by weight, and borax was used as a supercooling preventive agent in an amount of 1.5 parts by weight per 100 parts by weight of a sodium sulfate hydrate, and an acrylic water absorbing agent was used as a phase separation inhibitor. -Based resin (Sunwet M-1000 manufactured by Sanyo Kasei Co., Ltd.) was added in an amount of 1.5 parts by weight with respect to 100 parts by weight of sodium sulfate-based hydrate, and the mixture was stirred and mixed by a mixer. Examples 1-3 have a molar ratio of water to sodium sulfate of 9,
8 and 7. After preparation, DSC at -50 to 50 ° C
The amount of latent heat was measured in the temperature range of. This composition is 9-1
It is a heat storage material that has a heat storage temperature of 1 ° C, and is around 10 ° C
There is a latent heat peak near 30 ° C. The latent heat peak near -30 ° C is a eutectic of water and salts such as sodium chloride,
It is an unnecessary component for the present composition, and the smaller the amount, the better.
The measurement results are shown in Table 1. -3 as the molar ratio decreases
The amount of latent heat at 0 ° C is decreasing. It was found that the latent heat amount near 10 ° C. reached a maximum at a molar ratio of around 8.

Comparative Examples 1 to 3 Anhydrous sodium sulfate, ammonium chloride, ammonium bromide, sodium chloride and water as coagulation conversion agents,
33.2-10-5-5-46.8% by weight, 35.2-
10-5-5-44.8% by weight and 48.3-10-
Prepared to be 5-5-31.7% by weight, 1.5 parts by weight of borax as a supercooling inhibitor with respect to 100 parts by weight of sodium sulfate hydrate, and an acrylic water absorbent resin as a phase separation inhibitor. (Sunwet M-1000 manufactured by Sanyo Kasei Co., Ltd.) was added to 1.5 parts by weight of 100 parts by weight of sodium sulfate-based hydrate, and the mixture was mixed by stirring with a mixer. In Comparative Example 3, after a while after preparation, crystals began to precipitate because the amount of water in the composition was too small. In Comparative Examples 1 to 3, the molar ratio of water to sodium sulfate is 11, 10 and 9.
The latent heat quantity was measured by DSC in the same manner as in Example 1. The measurement results are shown in Table 1.

[0012]

[Table 1]

Examples 4 to 6 Anhydrous sodium sulfate, ammonium chloride, ammonium bromide, sodium chloride and water as coagulation conversion agents,
37.4-5-10-5-42.6% by weight, 39.2-
5-10-5-40.8% by weight and 42.4-5-1
The amount of borax was adjusted to 0-5-37.6% by weight, 1.5 parts by weight of borax as a supercooling inhibitor with respect to 100 parts by weight of sodium sulfate hydrate, and an acrylic water-absorbent resin as a phase separation inhibitor. (Sunwet M-1000 manufactured by Sanyo Kasei Co., Ltd.) was added to 1.5 parts by weight of 100 parts by weight of sodium sulfate-based hydrate, and the mixture was mixed by stirring with a mixer. Examples 4-6 have a molar ratio of water to sodium sulfate of 9, 8 and 7. The composition is a heat storage material having a heat storage temperature of 7 to 9 ° C, and latent heat peaks are present at around 9 ° C and around -30 ° C. The latent heat quantity was measured by DSC in the same manner as in Example 1. The measurement results are shown in Table 2. As the molar ratio decreases,
It was found that the latent heat amount at −30 ° C. decreased and the latent heat amount near 9 ° C. reached its maximum near 8 mol.

Comparative Examples 4 to 6 Anhydrous sodium sulfate, ammonium chloride, ammonium bromide, sodium chloride and water as coagulation conversion agents,
33.2-5-10-5-46.8 wt%, 35.2-
5-10-5-44.8% by weight and 48.3-5-1
The content of borax was adjusted to 0-5-31.7% by weight, 1.5 parts by weight of borax as a supercooling inhibitor with respect to 100 parts by weight of sodium sulfate hydrate, and an acrylic water absorbent resin as a phase separation inhibitor. (Sunwet M-1000 manufactured by Sanyo Kasei Co., Ltd.) was added to 1.5 parts by weight of 100 parts by weight of sodium sulfate-based hydrate, and the mixture was mixed by stirring with a mixer. In Comparative Example 6, crystals began to precipitate a while after preparation. In Comparative Examples 4 to 6, the molar ratio of water to sodium sulfate was 11,
10 and 6. The latent heat quantity was measured by DSC in the same manner as in Example 1. The measurement results are shown in Table 2.

[0015]

[Table 2]

Examples 7 to 9 Sodium sulfate decahydrate, anhydrous sodium sulfate, and sodium chloride 85.9-4.1 as a coagulant conversion agent
10% by weight, 81.2-8.8-10% by weight and 76
-14-10% by weight, borax as a supercooling inhibitor is 1.5 parts by weight with respect to 100 parts by weight of sodium sulfate-based hydrate, and an acrylic water-absorbent resin (sun wet) as a phase separation inhibitor. M-1000 manufactured by Sanyo Chemical Co., Ltd.)
1.5 to 100 parts by weight of sodium sulfate hydrate
Parts by weight were added and mixed by stirring with a mixer. Examples 7-9
Has a molar ratio of water to sodium sulfate of 9, 8 and 7
Is. This composition is a heat storage material having a heat storage temperature of 18 to 20 ° C., and the amount of latent heat was measured by DSC. The measurement results are shown in Table 1.

[0017]

[Table 3]

Comparative Examples 7 and 8 Sodium sulfate decahydrate, sodium chloride and water as coagulation conversion agents were prepared to be 85.5-10-4.5% by weight and 90-10-0% by weight. As a supercooling inhibitor, borax is 1.5 parts by weight with respect to 100 parts by weight of sodium sulfate hydrate, and as a phase separation inhibitor, an acrylic water absorbent resin (Sunwet M-1000 manufactured by Sanyo Kasei Co., Ltd.) is sodium sulfate. 1.5 parts by weight was added to 100 parts by weight of the system hydrate, and the mixture was mixed by stirring with a mixer. In Comparative Examples 7 and 8, the molar ratio of water to sodium sulfate was 11,
It is 10. The latent heat quantity was measured by DSC in the same manner as in Example 1. Both Comparative Examples 5 and 6 have a melting temperature range of 15 to 27 ° C.
The composition was unsuitable as a heat storage material. 1
The amount of latent heat of 8-20 ° C could not be measured.

[0019]

EFFECTS OF THE INVENTION The heat storage material of the present invention exhibits a sharp melting pattern and exhibits an excellent heat storage property capable of maintaining the initial stability even after repeated solidification and melting.

Claims (4)

[Claims] 1. A sodium hydrate of 10 hydrate and another hydrate of sodium sulphate having different water of crystallization, and anhydrous sodium sulphate, wherein the molar ratio of water of crystallization to sodium sulphate is 9.4 to 6.5. Heat storage material composition. 2. The heat storage material composition according to claim 1, wherein the other sodium sulfate salt having different water of crystallization is sodium sulfate heptahydrate. 3. The method according to claim 1, wherein one or more inorganic salts other than sodium sulfate are added as a freezing point modifier.
The heat storage material composition described in 1. 4. One or more selected from borax, silicate, and cryolite as a supercooling inhibitor, and one or more selected from CMC, attapulshy clay, and acrylic water-absorbing resin as a phase separation inhibitor. The heat storage material composition according to any one of claims 1 to 3, which is blended.