JPH1135933A - Cold storage material utilizing latent heat - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable an adjustment of the melting point and a secure application in foods by incorporating at least one inorganic salt selected from sodium hydrogen carbonate, potassium hydrogen carbonate, ammonium hydrogen carbonate, disodium phosphate dodecahydrate and trisodium phosphate dodecahydrate into an aqueous solution of sodium chloride. SOLUTION: An aqueous solution of sodium chloride is employed as a cold storage medium, and the concentration thereof is 5-30 wt.%. The purity of sodium chloride is preferably 99% or higher. The inorganic salt employed as a melting point-adjusting agent can be securely used in the foods distribution fields and has advantages such as a high eutectic temperature, chemical inactivity with sodium chloride, a specific gravity not so different from that of sodium chloride, moderate solubility in water, cheapness and ease to buy, easy manageability, a small depression of a freezing point, a large heat of melting in a solution at a certain temperature. The amount of the inorganic salts is 1-30 wt.% based on the sum of the salts and the aqueous solution of sodium chloride, the amount of the aqueous solution of sodium chloride being 70-99 wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a latent heat storage material using an aqueous solution of sodium chloride as a refrigerant (main agent). More specifically, the present invention relates to a latent heat storage material obtained by adding a specific inorganic salt as a melting point regulator and / or a supercooling inhibitor to a cold storage material containing an aqueous sodium chloride solution.

[0002]

2. Description of the Related Art Various efficient storage and storage methods of electric power energy have been studied and developed for the purpose of utilizing surplus electric power. For example, development of a latent heat storage material utilizing absorption heat accompanying a phase change such as melting and solidification of a substance serving as a heat medium is one of them. A heat storage material is a material that accumulates heat or cold in a substance and effectively uses the flow of heat when necessary. Particularly, a material utilizing heat generation / endothermic reaction mainly due to a phase change of a substance is referred to as a latent heat storage material, and more particularly, a case in which cold heat is stored in advance and then cooled when necessary is referred to as a latent heat storage material. There is no clear distinction.
Among the latent heat storage materials, those using inorganic materials such as inorganic salts and inorganic hydrated salts as the refrigerant storage medium have higher thermal conductivity, larger latent heat, smaller volume change, and nonflammability than organic materials. Among them, an aqueous solution of sodium chloride has further advantages that it is less toxic, has low reactivity, is easily available, has an appropriate solubility, and has a eutectic temperature close to the frozen food storage temperature. Therefore, these regenerative materials can be particularly suitably used for refrigeration of foods, cold preservation at the time of delivery, refrigeration of chemicals and pharmaceuticals, and cooling processes in food factories and the like.

[0003] By the way, such a latent heat storage material requires various temperature ranges depending on a cooling object (commodity).
It is advantageous to arrange the cold storage materials corresponding to each of them in order to have a wider product lineup. As a method for changing the melting point of the inorganic salt aqueous solution, it is known to change the mixing ratio of the inorganic salt dissolved in water. For example, JP-A-6-50686 discloses adjusting the melting point of an aqueous solution of an inorganic salt by dissolving two or more inorganic salts in water. However, the inorganic salts proposed in this publication lack safety for use in food distribution, such as potassium nitrate and sodium nitrate.

[0004] It is an object of the present invention to provide a cold storage material which not only can appropriately adjust the melting point of a latent heat storage material using a sodium chloride aqueous solution as a refrigerant storage medium, but can also be used with confidence in the food distribution field.

[0005]

Under these circumstances, the present inventors have conducted various studies on a suitable melting point modifier for an aqueous solution of sodium chloride. As a result, a specific inorganic salt among salts used as food additives has been found. It has been discovered for the first time that salts and / or inorganic hydrated salts have high safety and can set a melting point that meets needs, and have completed the present invention. That is, the present invention provides (1) an aqueous solution of sodium chloride,
And a latent heat storage material containing at least one inorganic salt selected from the group consisting of sodium hydrogen carbonate, potassium hydrogen carbonate, ammonium hydrogen carbonate, disodium phosphate dodecahydrate and trisodium phosphate dodecahydrate, (2)
The latent heat storage material according to the above (1), wherein the amount of the inorganic salt is 1 to 30% by weight based on the total amount of the aqueous sodium chloride solution and the inorganic salt, (3) phase transition in a temperature range of -40 ° C to -2 ° C The latent heat storage material according to (1) or (2), wherein the phenomenon occurs.
(4) The sodium chloride concentration of the aqueous sodium chloride solution is 5
The latent heat storage material according to any one of the above (1) to (3), which further contains sodium borate, and (6) sodium borate. Is from 0.1 to 5 parts by weight based on 100 parts by weight of the latent heat storage material containing the aqueous sodium chloride solution and the inorganic salt.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The refrigerant storage medium used in the present invention is an aqueous sodium chloride solution. The concentration of sodium chloride is not particularly limited as long as an aqueous solution is formed. Above all, 5-30
% By weight, more preferably 15 to 27% by weight. When the content of sodium chloride is 5 to 30% by weight, the temperature difference at the time of solidification and melting becomes small, and the cold storage / cooling temperature becomes close to constant, which is desirable as a cold storage material. Although the purity of sodium chloride is not particularly limited, it is usually 99%.
The above is preferably used.

As a melting point modifier, sodium hydrogen carbonate,
Potassium bicarbonate, ammonium bicarbonate, disodium phosphate dodecahydrate and trisodium phosphate dodecahydrate
At least one inorganic salt selected from the group consisting of hydrated salts is used. These inorganic salts can be used safely in the food distribution field, as well as their eutectic temperature is high, they are chemically inert with sodium chloride, the specific gravity is not much different from sodium chloride, and their solubility in water is extremely large. However, there are advantages that it is not small, that it is inexpensive and easy to purchase, that there is no particular problem in handling, that the freezing point drop is small, and that the heat of fusion with an aqueous solution of a certain concentration is large. Among the above inorganic salts, disodium phosphate dodecahydrate also has an effect of preventing supercooling.

The amount of the inorganic salt used is such that the amount of the aqueous sodium chloride solution is
Preferably, the amount of the inorganic salt is 90 to 99% by weight, and the amount of the inorganic salt is 1 to 10% by weight.

A supercooling inhibitor may be added to the latent heat storage material of the present invention. The supercooling inhibitor used is not particularly limited, but borax (sodium borate decahydrate) is preferred. Borax is used in an amount of 0.1 to 5 parts by weight, preferably 2 to 4 parts by weight, based on 100 parts by weight of the latent heat storage material.

[0010] Ingredients that may be added to the latent heat storage material of the present invention include water-absorbing resins, thickening agents such as attapulghai clay, gelatin, agar, and silica gel.

The latent heat storage material of the present invention is preferably
40 ° C to -2 ° C, more preferably -30 ° C to -15 ° C
It is preferable that a phase transition phenomenon occurs in the above temperature range.

The method for producing the regenerator material is not particularly limited. For example, sodium chloride is gradually added to a predetermined amount of pure water or ion-exchanged water in a container while gradually stirring the mixture and thoroughly mixed. Add the melting point modifier to the specified amount while stirring gradually, mix well, add other additives at the same time or before or after this, stir and mix, sodium chloride, inorganic salt, etc. on the resin And a method of pouring an aqueous solution obtained by premixing the components in advance. In addition, sodium chloride,
The order of addition of the inorganic salt and other additives is arbitrary, and heating to about 50 ° C. is possible to promote dissolution. After mixing sodium chloride and an inorganic salt, the mixture may be added to pure water or ion-exchanged water.

Although the form of the cold storage material is not particularly limited, it is usually a form in which the above-mentioned cold storage material is packaged with a corrosion-resistant metal or inorganic material and / or an organic material such as polyethylene or other plastics. Examples of the shape include a lump, a plate, and a sheet. As a place where such a cold storage material is arranged, as it is in a cold storage room,
Alternatively, it is conceivable to place it in a heat exchange section.

[0014]

The present invention will be described below in more detail with reference to examples. However, the present invention is not limited to the following examples. Examples 1 to 5 Table 1 with respect to 95 parts by weight of a 15% by weight aqueous solution of sodium chloride.
Was added and stirred to obtain a latent heat regenerator. The melting temperature of the obtained regenerator material was measured by DSC (differential scanning calorimeter). DSC program: cooling rate 1 ° C / min → 2 at -45 ° C
Hold for 0 minute → heating rate 2 ° C./min→−10° C. The results are shown in Table 1.

Comparative Example 1 The melting temperature of an aqueous sodium chloride solution was measured in the same manner as in Example 1 except that no inorganic salt was used. Table 1 shows the results
Shown in

[0016]

[Table 1]

Examples 6 to 10 A latent heat storage material was obtained in the same manner as in Example 1 except that a 23.3% by weight aqueous solution of sodium chloride and an inorganic salt shown in Table 2 were used, and the melting temperature was measured. Table 2 shows the results.

Comparative Example 2 The melting temperature of an aqueous sodium chloride solution was measured in the same manner as in Example 6 except that no inorganic salt was used. Table 2 shows the results
Shown in

[0019]

[Table 2]

[0020]

According to the latent heat storage material of the present invention, the melting temperature can be adjusted as desired by adding an inorganic salt, so that the heat storage efficiency is increased and the salt used as an additive for food is used. Also, safety is ensured, and it can be used safely for keeping food cool.

Continued on the front page (72) Inventor Ryuji Katsuo 8 Nishinocho, Higashimukaijima, Amagasaki City, Hyogo Prefecture Inside Mitsubishi Electric Wire Industry Co., Ltd.

Claims (6)

[Claims] 1. An aqueous sodium chloride solution and at least one selected from the group consisting of sodium hydrogen carbonate, potassium hydrogen carbonate, ammonium hydrogen carbonate, disodium phosphate dodecahydrate and trisodium phosphate dodecahydrate. Latent heat storage material containing inorganic salts. 2. The latent heat regenerator according to claim 1, wherein the amount of the inorganic salt is 1 to 30% by weight based on the total amount of the aqueous sodium chloride solution and the inorganic salt. 3. The latent heat storage material according to claim 1, wherein a phase transition phenomenon occurs in a temperature range of −40 ° C. to −2 ° C. 4. The latent heat storage material according to claim 1, wherein the aqueous sodium chloride solution has a sodium chloride concentration of 5 to 30% by weight. 5. The method according to claim 1, further comprising sodium borate.
The latent heat storage material described. 6. The latent heat storage material according to claim 5, wherein the amount of sodium borate is 0.1 to 5 parts by weight based on 100 parts by weight of the latent heat storage material containing the aqueous sodium chloride solution and the inorganic salt.