JP3774530B2 - Manufacturing method of heat storage material - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a latent heat storage material used for heating a building or the like.
[0002]
[Prior art]
Many proposals have been made to use a salt hydrate having the property of solid-liquid phase change as a heat storage material, and it has already been put into practical use in the field of floor heating and the like. Typical salt hydrates include sodium sulfate decahydrate, calcium chloride hexahydrate, disodium hydrogen phosphate 12 hydrate, sodium acetate trihydrate, and the like. All of these salt hydrates exhibited a supercooling phenomenon by themselves, which was a large barrier to use as a heat storage material. In order to overcome this barrier, many proposals have been made on supercooling inhibitors or supercooling prevention methods.
[0003]
It was found in 1952 that sodium tetraborate decahydrate was effective as a supercooling inhibitor for sodium sulfate decahydrate. This combination belongs to the same crystal system, and since the lattice constants of the crystals are close, it is known that the nucleation is based on heteroepitaxial growth.
After this discovery, the search for other salt hydrates continued with a crystallographic approach, but no similar combinations have yet been found.
[0004]
On the other hand, for sodium acetate trihydrate, a method using a specific supported crystal has been proposed. Examples of supported crystals include sodium salts such as disodium hydrogen phosphate and trisodium phosphate (Japanese Patent Publication No. 61-42957 and Japanese Patent Publication No. 2-15598). These are methods in which a support crystal or a press-supported support crystal is placed in a melt of sodium acetate trihydrate, and the melt is solidified by forced cooling.
In these methods, the supercooling prevention effect cannot be obtained unless the melt is solidified and the sodium acetate trihydrate is solidified on the surface of the supported crystals. Therefore, the supercooled state is broken after filling the container. Therefore, forced cooling-solidifying operation is essential, which is an inconvenient method in mass production. In addition, it is necessary to use a large amount of supported crystals.
When adopting a method of solidifying the melt by introducing seed crystals instead of forced cooling, it is necessary to precool the melt in advance so that the seed crystals do not melt. Is an inconvenient method.
[0005]
In order to solve this problem, Japanese Patent Publication No. 1-51515 and Japanese Patent Publication No. 58-27301 disclose sodium pyrophosphate as a supporting crystal (base material) in a melt, which is cooled or solidified as it is or taken out. Separately, a method for producing a supercooling inhibitor is disclosed. In JP-A-64-75583, a supported crystal is put into a melt, solidified once, and then heated and melted again. Thereafter, the crystal collected from the melt is filtered with a supercooling inhibitor (nucleating agent). A method is disclosed.
In these methods, it is only necessary to add a supercooling inhibitor to the filling melt, so that the operability is improved, but it is necessary to adjust the melt to produce the supercooling inhibitor. Further, since it is solidified after being filtered from the melt, there is a problem in energy consumption, operational safety, operational simplicity, etc. because it needs to be pulverized for use as a supercooling inhibitor.
[0006]
[Problems to be solved by the invention]
The present invention seeks to solve the problems of the prior art described above. That is, the present invention provides a simple method for making the effect of the supercooling inhibitor remarkable in the method for producing a heat storage material, thereby enabling economical mass production.
[0007]
[Means for Solving the Problems]
That is, the present invention provides (A) a melt of a composition containing a heat storage material main material and a supercooling-preventing support crystal, and (B) a heat storage that cools a molded body containing the heat storage material main material after filling the container. The present invention relates to a method for manufacturing a material.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described in detail below.
As the heat storage material main material of the present invention, a salt hydrate having a property of solid-liquid phase change is usually used. Typical salt hydrates include sodium sulfate decahydrate, calcium chloride hexahydrate, disodium hydrogen phosphate twelve, calcium nitrate tetrahydrate, sodium acetate trihydrate, strontium chloride hexahydrate, and the like. .
These are used alone or as a composition with a eutectic salt or a melting point adjusting agent. In addition to the crystal water, it may be preferable to add a small excess of water.
[0009]
As the supporting crystal for preventing overcooling of the present invention, a crystal capable of supporting the main material of the heat storage material is used. For example, when the main material of the heat storage material is sodium acetate trihydrate, the supported crystals include disodium hydrogen phosphate, monosodium dihydrogen phosphate, trisodium phosphate, sodium tetraborate, sodium bromide, and their water. A Japanese thing etc. are illustrated. Further, in the case of strontium chloride hexahydrate as the heat storage material main material, strontium hydroxide octahydrate as the support crystal, and in the case where the heat storage material main material is disodium hydrogen phosphate 12 hydrate, as the support crystal Examples thereof include sodium tetraborate and hydrates thereof.
[0010]
Preferably, sodium acetate trihydrate as the heat storage material main material, disodium hydrogen phosphate, monosodium dihydrogen phosphate, trisodium phosphate, sodium tetraborate, sodium bromide as a supported crystal, or a hydrate thereof More preferably, sodium acetate trihydrate as the heat storage material main material, disodium hydrogen phosphate or trisodium phosphate as the supported crystal, particularly preferably sodium acetate trihydrate as the heat storage material main material, Disodium hydrogen phosphate is used as the supported crystal.
[0011]
The salt hydrate may be a salt hydrate melt using an anhydride together with water. When using a salt hydrate, a small amount of water may be added.
For example, sodium acetate may be any of anhydrous and trihydrate salts, and water may be used in the range of 3.0 to 4.5 moles of water per mole of anhydrous sodium acetate in terms of sodium acetate. An amount of water of 3.0 mol or less is not preferable because it is not sufficient to form sodium acetate trihydrate, and an anhydride remains, which may cause a decrease in the amount of stored heat. If it is 4.5 moles or more, water is excessive, so that the heat storage amount may be reduced due to the dilution effect, which is not preferable.
[0012]
The overcooling-supported crystal of the present invention must be present as a crystal at the time of heating and cooling, and for that purpose, it is necessary to add an amount higher than the solubility. Since the solubility depends on the coexisting ionic species and the liquid temperature, it is difficult to specify the addition amount, but it is preferably 0.5 to 10% by weight, more preferably 0.5 to 5% by weight.
[0013]
The thickener of the present invention suppresses settling of the main material of the heat storage material and the supporting crystal for preventing overcooling in the heat storage material composition during heating and melting and reduces non-uniformity of the concentration in the melt. The main work is to do. Therefore, hydrophilic and highly viscous ones are preferred and can be selected from known thickeners. Suitable thickeners include water-soluble polymers containing carboxyl groups, such as carboxymethylcellulose sodium salt, poly (sodium acrylate-acrylamide) copolymer, and the like. These are added in an amount that provides a sufficiently high viscosity in the melt, and preferably in the range of 1 to 10% by weight. If it is less than 1%, high viscosity may not be expected, and if it exceeds 10%, it is preferable in terms of viscosity, but due to the diluting effect, the heat storage amount may be reduced.
[0014]
The melt of the composition of the present invention is maintained at a temperature that does not cause crystal precipitation of the main material of the heat storage material by heating the composition. The fluidity of the melt depends on the thickening effect of the thickener.
The molded body containing the heat storage material main material of the present invention acts as a seed crystal of the main material when the melt is cooled. Therefore, the molded body usually contains the main material in a crystalline state, and an auxiliary for shape retention can be used alone.
[0016]
The molded body of the present invention can be directly put into a heated melt. Alternatively, it is possible to fill a heated melt after charging the compact. Accordingly, the filling, sealing, and storage processes flow smoothly and are suitable for mass production.
[0017]
The molded body of the present invention preferably has a shape that does not melt even in a heated melt, and preferably has a sufficient thickness. Although the cooling rate after the heated melt is filled in the container depends on the material and shape of the container and the heat transfer environment outside the container, it is difficult to specify the thickness of the molded body, but the preferred thickness is 3 mm. It is above, Preferably it is 3-30 mm. Although it depends on other conditions, the thickness of 3 mm or less is not preferable because it may dissolve in a short time. If it is more than 30mm, it may be too large to fill the container. More preferably, it is 5 to 15 mm.
[0018]
The shape of the molded body of the present invention is not particularly limited. Any shape may be used as long as the thickness of the thinnest portion is as described above. In consideration of filling the container, the shape can be variously modified based on a cylindrical shape, a cube, a rectangular parallelepiped, a spherical shape, or the like.
[0019]
The manufacturing method of a molded object can use the various methods for maintaining a heat storage material main material as a molded object. When the heat storage material main material is used, there are dry processes such as single crystal cutting, polycrystal press molding, and wet processes such as supercooled liquid crystallization. In the case of using the main material of the heat storage material and the shape retention aid, there are molding of polycrystal and an adhesive, crystallization of the supercooling liquid of the heat storage material containing the thickener, and the like.
[0020]
In the present invention, when the melt of the composition and the molded body are cooled after filling the container, the supercooling is broken by the action of the molded body which is a seed crystal, and the whole crystallizes. By this first crystallization, it is assumed that the main material of the heat storage material is supported on the surface of the supercooling prevention supporting crystal added in the melt, and has a function as a supercooling prevention agent. Thereafter, even if a seed crystal is not newly added, the supercooling phenomenon can be effectively suppressed while the container is sealed.
[0021]
The cooling method may be cooling, air cooling, water cooling, or other commonly used cooling methods, but for mass production, it will be most economical to cool as well as store in a warehouse.
[0022]
EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.
[0023]
【Example】
Example 1
(Manufacture of melt)
In a 2-liter beaker, 550 g of sodium acetate and 450 g of water were collected and dissolved in a 70 ° C. water bath. To this was added 20 g of disodium hydrogen phosphate, and the mixture was stirred for 10 minutes, and then 30 g of carboxymethyl cellulose sodium salt was added little by little. A viscous melt was obtained after stirring for 30 minutes.
[0024]
(Manufacture of molded products)
In a 100 ml beaker, 55 g of sodium acetate and 45 g of water were collected and dissolved in a 70 ° C. water bath. To this, 3 g of carboxymethylcellulose sodium salt was added little by little, stirred for 30 minutes, and then filled into a sealed one end of a flexible PVC pipe having an outer diameter of 15 mm (wall thickness of 1 mm) and a length of 500 mm. After allowing this to cool and making it supercooled, a small amount of sodium acetate trihydrate crystal was added, and as a result, the content of the soft vinyl tube rapidly crystallized and solidified. The upper end was sealed and allowed to stand overnight, then cut and subjected to the following experiment.
[0025]
(Manufacture of heat storage materials)
Using a hard PVC plate with a thickness of 2 mm, a container with an outer size of 200 x 200 x 20 mm (with one end of 200 x 20 mm opened) was produced. With the open end as the upper end, 15 mm thick polystyrene foam was pasted on the side and bottom to insulate it.
The above melt (70 ° C.) was filled up to 20 mm from the upper end of the container. Immediately after the above molded body (cut to 30 mm in length) was put in and a hard PVC plate (200 × 20 × 2 mm) was covered, 15 mm thick foamed polystyrene was placed on the lid to insulate it. After 2 hours, the heat insulating material and the lid were removed, and the contents were observed, and the whole was solidified.
[0026]
Example 2
A molded body (cut to a length of 30 mm) produced in the same manner as in Example 1 was put into an empty container (with a heat insulating material attached) as in Example 1. This was filled with the same melt (70 ° C) as in Example 1 up to 20 mm from the top of the container, immediately covered with a hard PVC plate (200 x 20 x 2 mm), and then 15 mm thick expanded polystyrene from the top of the lid. To insulate. After 2 hours, the heat insulating material and the lid were removed and the contents were observed, and the whole was solidified.
[0027]
Comparative Example 1 (example in which a molded product is not charged)
In Example 1, the same operation was performed except that the molded body was not charged. After 2 hours, the heat insulating material and the lid were removed and the contents were observed.
[0028]
Comparative example 2 (example in which powdery seed crystals were added)
In Example 2, the same operation was performed except that 5.0 g of powdered sodium acetate trihydrate was added instead of the molded body. After 2 hours, the heat insulating material and the lid were removed and the contents were observed.
[0029]
【The invention's effect】
According to the present invention, in the method for producing a heat storage material, a simple method for making the effect of the supercooling inhibitor remarkable is provided, thereby enabling economical mass production.

Claims (8)

(A) A heat storage material characterized by cooling a melt containing a main component of the heat storage material and a supporting crystal for preventing overcooling and (B) a molded body containing the main material of the heat storage material after filling the container. A method of manufacturing the material. The method for producing a heat storage material according to claim 1, wherein the main material of the heat storage material is sodium acetate trihydrate. (A) a melt of a composition comprising 100 parts by weight of sodium acetate trihydrate, 0.5 to 10 parts by weight of supporting crystals for preventing supercooling, and 1 to 10 parts by weight of a thickener; and (B) sodium acetate trihydrate. A method for producing a heat storage material, comprising cooling a molded body containing the product after filling the container. (A) A melt of a composition comprising 100 parts by weight of a mixture containing 3.0 to 4.5 moles of water per mole of sodium acetate, 0.5 to 10 parts by weight of supported crystals for preventing supercooling, and 1 to 10 parts by weight of a thickener. And (B) a method for producing a heat storage material, wherein a molded body containing sodium acetate trihydrate is cooled after filling the container. The method for producing a heat storage material according to any one of claims 1 to 4, wherein the overcooling-supporting crystal is disodium hydrogen phosphate or trisodium phosphate. The method for producing a heat storage material according to any one of claims 3 to 5, wherein the thickener is a water-soluble polymer containing a carboxyl group. The method for producing a heat storage material according to any one of claims 1 to 6, wherein the molded body (B) has a shape that does not melt in the melt (A). The method for producing a heat storage material according to any one of claims 1 to 6, wherein the molded body (B) is a molded body having a thinnest portion having a thickness of 3 mm or more.