JP2007314741A - Latent heat storage material composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a latent heat storage material composition that has a melting point at temperatures in the range ambient to 57°C and is used as a heat storage material for a heating system. <P>SOLUTION: The latent heat storage material composition based on a sodium acetate is produced by mixing 100 pts.wt. sodium acetate hydrate having a composition of the formula: CH<SB>3</SB>COONa-nH<SB>2</SB>O (wherein n is 3 or 0) with a seed material for promoting crystallization comprising a composite material or the like of succinic acid and/or lithium fluoride, a phase separation inhibitor comprising 1-20 pts.wt. ceramics of attapulgite and/or sepiolite, more preferably, 0.1-20 pts.wt. mixture of attapulgite and sepiolite in a mixing ratio (by weight) of attapulgite to sepiolite of 9/1-1/9, which constitutes an adsorption and fixing material required to have heat resistance at 90°C, and additionally, if necessary, a filler comprising 0.1-10 pts.wt. various kinds of fibers including a glass fiber and the like. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

Detailed Description of the Invention

  The present invention relates to a latent heat storage material. More specifically, the present invention relates to a latent heat storage composition useful for use in a temperature range adapted to a hot water supply / heating system for a house or a building.

  A substance that absorbs and dissipates a large amount of latent heat at a constant temperature during the melting and solidification process stores this latent heat without causing a temperature change, and releases or absorbs the heat without changing the temperature when necessary. As a latent heat storage material, there are many heat storage materials related to atmospheric heat and waste heat by heat pumps, solar heat storage, inexpensive nighttime power use, etc., and proposals to use them. .

  Various inorganic hydrates are known as excellent heat storage materials. However, since inorganic hydrates have a peritectic point at the transition melting point, the heating temperature for melting becomes higher than the harmonic melting point. Therefore, when it melts, it is separated into two phases of an inorganic salt solid and a saturated aqueous solution thereof, and a phenomenon such as no formation of a hydrated salt occurs even when cooled.

  Methods such as changing the melting point with water or a harmonized substance have been proposed as methods for temperature harmony. In the results, the composed composition had a reduced melting point temperature and heat. Further, in order to effectively use the latent heat of fusion of the latent heat storage material, it is necessary to adjust the melting point / freezing point so as to act reliably within the operating temperature range.

  Sodium acetate trihydrate, which is widely known as a latent heat storage material, has a melting point / freezing point of 57.5 ° C. and a latent heat amount of 60 cal / g. As a hydrate, it is an excellent latent heat storage material having a melting point in the range of use, but in order to use a theoretical melting point of 57.5 ° C. for a thermal system, the material of sodium acetate trihydrate remains as it is. It is not suitable for use. In order to melt the material substance related to the peritectic transfer, the heating temperature reaches 80 ° C., and even if the heating time is changed, a heating temperature of 70 ° C. or more is required.

  Therefore, the components of thickeners and seed agents that maintain the composition of sodium acetate hydrate are naturally required to have heat resistance performance. Particularly in sodium acetate trihydrate, the phase separation phenomenon due to the supercooling and the difference in the component density mentioned in the previous section was conspicuous among the hydrates, and its specificity hindered the utilization of latent heat.

  There are known proposals to stabilize a composition such as sodium acetate trihydrate and use it as a latent heat storage material for heating (for example, Japanese Patent Publication Nos. 56-10359, 59-53578, 61-11986, and the like). However, the proposed thickener was not a disclosure satisfying the heat-resistant use conditions corresponding to high temperatures.

  That is, sodium acetate trihydrate is generally easy to supercool by melting as a general property, and phase separation is remarkable due to the difference in density. When the seed agent is added, the supercooling is temporarily eliminated. However, when the number of times of melting / solidification is repeated, a dense anhydrous acetate solid settles in the saturated aqueous solution and separates into two phases upon melting. . When this separation phenomenon proceeds, a balanced crystal cannot be obtained again, the heat storage function of the composition is lost, and the function intended by the invention cannot be achieved. That is, if the balance of the heat storage material is missing at the composition design stage, the functional effect as a heat storage material could not be expected.

  Therefore, the latent heat storage material that can be used in the temperature condition that is the object of the present invention cannot achieve the maintenance of the composition structure and the object by adding the seed material. Further, there has been no proposal of a composition constituent thickener that can be used stably in the heating and melting temperature range of 90 ° C. (for example, as a typical example that has been proposed, organic substances such as polymers such as PVA, polysaccharides, (Inorganic clay minerals such as kaolin, diatomaceous earth, bentonite, etc.) These thickener materials are effective when used at low temperature settings. Loss of function. As a result of losing the function in practice, no heat-resistant acetic acid-based latent heat storage material has been obtained.

Problems to be solved by the invention

  In the present invention, latent heat having a heat radiation temperature of 57 ° C. near the melting point of the system is used for heating and hot water supply systems. As a result of examining a latent heat storage material mainly composed of sodium acetate trihydrate, two phases are generated at the time of heating and melting due to the difference in density of the components, that is, acetic anhydride crystals in the lower layer and intermolecular of saturated aqueous acetic acid in the upper layer It was a means to prevent separation. The heat storage material is almost impossible to regenerate when separation occurs. Therefore, the best means is to analyze the mechanism of occurrence of composition separation from all angles and to take certain physical measures to suppress in advance. Otherwise, the original purpose cannot be achieved. In addition, various types of thickeners that have been proposed in the past have made their purpose difficult due to their specific regression factors (for example, heat durability, component compatibility, safety, accuracy, etc.) inhibiting their function as stabilizers.

  The present inventor paid attention to the fact that porous ceramics are effective in heat resistance and ion exchange capacity as a solution to this solution, and as a result of research on the nature, heat resistance and durability, safety, and economy of many porous ceramics. In addition, we are trying to prevent separation using attapulgite / and sepiolite complex / or simple substance, and verifying the solution. (For example, there is a proposal of Japanese Patent Publication No. 2890197 in 1999) However, in this means, sepiolite adopted has a function corresponding to both phase separation and supercooling. In order to keep it to a minimum, we tried to improve it by using the means of promoting solidification, which lacked the accuracy and stability of solidification.

As a means, a composition such as succinic acid (chemical formula HO ₂ C (CH ₂ ) ₂ CO ₂ H) excellent in heat resistance and / or a single compound such as lithium bromide is added to the composition and used. Even if the temperature was raised and lowered repeatedly at the above-mentioned high temperature, the supercooling was broken at a constant temperature of 53 ° C. without any trouble, and the possibility of 57 ° C. latent heat radiation was demonstrated. As a result, a latent heat storage material that supplies heat to heating and hot water supply can be obtained.

Means for solving the problem

That is, in the present invention, attapulgite / and sepiolite composite or simple substance is used as a composition separation inhibitor for 100 parts by weight of sodium acetate hydrate having a composition of the chemical formula CH ₃ COONa.nH ₂ O (n is 3,0). A latent heat storage material composition having a network structure obtained by mixing 0.1 to 30 parts by weight and 0.1 to 30 parts by weight of a succinic acid / lithium bromide compound / or a solid coagulation promoting seed agent. is there.

  In the present invention, the mixing ratio (weight) of the succinic acid and lithium fluoride composite is 9/1 to 1/9, especially 3/1 to 1/1. Use of ˜30 parts by weight is a preferable embodiment because the effect can be obtained with a smaller addition amount.

  Furthermore, the present invention uses a smaller amount of the mixture of attapulgite and / or sepiolite (weight) 9/1 to 1/9, particularly 3/1 to 1/1, as a phase separation inhibitor in the heat storage material composition. Since the effect can be obtained with the added amount, it is preferable. The composition includes 0.1 to 20 parts by weight of the mixture.

Sodium acetate hydrate used as the main component of the latent heat storage material of the present invention is represented by the chemical formula CH ₃ COONa · nH ₂ O (n is 3, 0). This includes so-called sodium acetate trihydrate and those in which the amount of crystal water is slightly increased or decreased. When n = 3, it is sodium acetate trihydrate. Such sodium acetate hydrate can be prepared by adding water to sodium acetate anhydrous or sodium acetate hydrate.

  In the present invention, the amount of attapulgite and / or sepiolite added to sodium acetate hydrate as the main agent is 1 to 20 parts by weight of attapulgite and / or sepiolite alone or in combination with 100 parts by weight of sodium acetate hydrate. . If the amount added is larger than this, the fluid becomes too viscous to be practical. On the other hand, if the addition amount is less than this range, the functional material as the object of the present invention cannot be obtained. Within the said range, the addition amount can be arbitrarily selected by the temperature range which uses a latent-heat storage material.

  In addition, since the system of the present invention is a hydrate, a phase separation phenomenon is likely to occur upon melting, and the heat storage effect has been reduced by repeated melting and solidification. Therefore, in the present invention, it is preferable to add 0.1 to 30 parts by weight of sepiolite as a thickener for suppressing phase separation. That is, a more preferred embodiment of the present invention is a latent heat storage material composition obtained by mixing 1 to 20 parts by weight of a combination of attapulgite and sepiolite alone or with 100 parts by weight of sodium acetate hydrate as the main agent.

Here, the apulgite is a hydrous magnesium silicate based ceramic having a palygorskite structure of (Mg.AL) ₂ Si ₄ O ₁₀ (OH) · 4H ₂ O structural formula. It is a naturally occurring fibrous clay mineral that has a porous fibrous structure and ion exchange properties between interlayer cations, and has a function of incorporating water molecules and organic molecules. Sepiolite is also referred to as aorite and is a hydrated magnesium silicate ceramic having a structural formula of 2MgO.3SiO ₂ .nH ₂ O. The crystal structure is a very fine fiber crystal, and innumerable tunnel-like pores having a micropore diameter exist between the fibers. This unique adsorption effect by the tunnel entraps crystal water and crystal molecules, prevents the separation of water molecules and lattices in a fibrous form, and acts as a powerful phase separation inhibitor. A stable composition is characterized by these two unique adsorption performances.

  In addition, apagite and sepiolite can be used in the form of a fibrous material, a powdered material obtained by pulverizing this, or a mixture thereof. Further, by adding glass fiber or the like as a filler in addition to these, resource saving and economic effects can be achieved.

Hereinafter, the present invention will be specifically described with reference to examples.
[Example 1]
Water was added to sodium acetate hydrate, and sodium acetate hydrate was prepared as follows to have a composition of general formula CH ₃ COONa · nH ₂ O (n is 3,0).
Sodium acetate hydrate: 100 parts by weight Apagite 2.5 parts by weight Sepiolite 1.0 part by weight of a mixture was prepared by adding succinic acid and lithium bromide to each addition amount shown in Table 1, and a latent heat storage material A composition was prepared, and the temperature in the thermostatic chamber was maintained at 70 ° C. for 8 hours. Then, the temperature in the thermostatic chamber was decreased to 20 ° C., and the freezing point of the composition was 56.5 ° C. and the duration was 6 Maintenance measurements were taken over time. The results are shown in Table 1. It was recorded and confirmed in successive repetitions that the phase change steadily even after heating and that the supercooling was broken at 52 ° C. and the temperature rose to 56 ° C.

［比較例］
アパジャイト、セピオライトを添加せず、酢酸ナトリウム水和物１００重量部に対し、化学式ＨＯ_２Ｃ（ＣＨ_２）_２ＣＯ_２Ｈ（コハク酸）及び沸化リチウム複合物を各々２重量部を添加して、潜熱蓄熱材組成物を調製し、実施例１と同様にして凝固点測定を試みたが、融解／凝固を約１５０回の繰り返し時点より無水結晶の成長現象や及び液体／固体の相分離現象が発生し、蓄熱材の機能を喪失した。

[Comparative example]
Without adding apagite and sepiolite, 100 parts by weight of sodium acetate hydrate was added with 2 parts by weight of each of the chemical formula HO ₂ C (CH ₂ ) ₂ CO ₂ H (succinic acid) and lithium fluoride composite. Then, a latent heat storage material composition was prepared and an attempt was made to measure the freezing point in the same manner as in Example 1. However, an anhydrous crystal growth phenomenon and a liquid / solid phase separation phenomenon were observed from the time when melting / solidification was repeated about 150 times. Occurred and lost the function of the heat storage material.

[Example 2]
Using the same sodium acetate hydrate as used in Example 1,
Sodium acetate hydrate: 100 parts by weight apagite: 2.5 parts by weight Sepiolite: 1.0 part by weight Seed material mixture: 2.0 A latent heat storage material obtained by mixing the double scene part with- The temperature was raised to 80 ° C. in a low-temperature thermostatic bath that can be programmed from 25 ° C. to + 125 ° C., then set to 20 ° C. and the temperature was lowered and solidified. In the experiment, the melting and solidification processes were repeated 500 times in this way, but there was no change in the heat storage amount and the heat release cycle function.

The invention's effect

  The latent heat storage material of the present invention is a thickener and network structure that avoids phase separation of components even when dissolved at a high temperature of 90 ° C. by addition of apagite and / or sepiolite to sodium acetate hydrate. Constructed the body. Furthermore, the use of succinic acid and lithium fluoride composites in the solidification promoting sheet material accurately solidifies the supercooling temperature, which was unstable only with the sepiolite alone thickener proposed previously, to 53 ° C, and 56 ° C. Since the latent heat radiation can be repeated in the process, energy loss due to overcooling is reduced and reliability is improved. Thermal storage material used in general temperature ranges, especially for hot water supply and heating systems, has higher density and heat per unit volume than hot water tank type, useful for space-saving and large-capacity heat storage It is.

Claims (4)

Solidification promotion with 0.1 to 30 parts by weight of phase separation preventive material (thickener) for 100 parts by weight of sodium acetate hydrate having a composition of general formula CH ₃ COONa · nH ₂ O (n is 3H ₂ O) A latent heat storage material composition obtained by mixing 0.1 to 30 parts by weight of a seed agent.   2. The latent heat storage material composition according to claim 1, wherein the phase separation preventing material (thickener) or attapulgite and sepiolite are used alone or in a mixture ratio (weight) in the range of 9/1 to 1/9. . A succinic acid having a composition of a chemical formula HO ₂ C (CH ₂ ) ₂ CO ₂ H as a coagulation promoting seed agent and lithium fluoride represented by the general formula LiF are mixed and adjusted or used alone. Item 3. The latent heat storage material composition according to Item 1 or 2. Thickener uses 0.1 to 30 weights of a mixture of attapulgite and sepiolite in 100 parts by weight of sodium acetate hydrate having a composition of chemical formula CH ₃ COONa · nH ₂ O (n is 3,0). And a latent heat storage material composition for heating, wherein the seed agent is composed of 0.1 to 30 parts by weight of a single or a mixture of succinic acid and lithium fluoride.