JP2002030279A - Latent heat cooling agent - Google Patents

Abstract

PROBLEM TO BE SOLVED: To sufficiently reduce the supercooling of a latent heat cooling agent having (-3)-(-12) deg.C melting temperature to reduce the consumption of useless solidification energy in a solidifying-melting cycle. SOLUTION: An aqueous solution of sodium carbonate is used as a cooling medium, and ammonium dihydrogen phosphate is dissolved therein as an agent for preventing the supercooling. In other aspect, an aqueous solution of potassium nitrate is used as the cooling medium, and sodium sulfate decahydrate is dissolved therein as the agent for preventing the supercooling.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an aqueous solution of an inorganic compound (hereinafter also referred to as an inorganic aqueous solution).
The present invention relates to a latent heat storage material using a material having a melting temperature of −12 ° C. as a refrigerant storage medium (main agent).

[0002]

2. Description of the Related Art In recent years, cold storage materials have been developed for the purpose of utilizing surplus electric power. As a cold storage material, for example,
There is a latent heat regenerative material that utilizes heat absorbed by phase transition such as melting and solidification of a substance serving as a refrigerant. Among these latent heat storage materials, those using an aqueous solution of an inorganic compound such as an inorganic salt or an inorganic hydrate salt as a refrigerant have a higher thermal conductivity and a larger latent heat amount than those using an organic material, and are nonflammable. And so on.

However, a latent heat storage material using an aqueous solution of the above-mentioned inorganic compound as a refrigerant has a problem of causing supercooling. The term “supercooling” means that when a substance is cooled, a transition phenomenon does not appear (that is, does not solidify) even when the temperature exceeds a liquid to solid phase transition temperature. For example, it is known that an aqueous sodium chloride solution is used as a refrigerant storage medium.
3.3% by weight aqueous sodium chloride solution has a phase transition temperature of-
Despite the temperature of 21 ° C., solidification may not actually occur unless cooled to around −30 ° C. In other words, the occurrence of supercooling requires refrigeration equipment capable of cooling to a temperature lower than the temperature at which the regenerator material is to be actually used (the freezing point of the refrigerant storage medium). In addition, there is a problem that extra energy is required, such as an increase in running cost due to a decrease in operating efficiency due to low-temperature operation (3% decrease every 1 ° C. decrease). For this reason, in order to alleviate supercooling, a substance (supercooling inhibitor) serving as a nucleus of the refrigerant medium during solidification is added. For example, JP-A-5-332457
Japanese Patent Application Laid-Open Publication No. H11-157, discloses that carbon black having a DBP oil absorption of 100 or more is added to an inorganic aqueous solution (heat storage medium) such as NH ₄ Cl or NaCl. However, as to what kind of substance is effective as a supercooling inhibitor, while it is suggested that a substance having the same crystal structure and lattice constant as the refrigerant medium is better, Some of them have high supercooling prevention effects, and at present, it is trial and error what type of supercooling inhibitor is suitable for a specific refrigerant storage medium.

Incidentally, a latent heat storage material using an inorganic aqueous solution as a refrigerant storage medium has a melting temperature of -3.degree. C. to -12.degree. C., which can be easily solidified in a home refrigerator, that is, -3.degree. Those using an aqueous inorganic solution exhibiting a melting temperature of −12 ° C. are commercially available. This is generally installed in refrigerating freezers or refrigerating showcases to store fresh fish, meat, milk, beverages, prepared foods, dairy products, daily items, vegetables,
It is used for keeping the fruits and the like at a proper temperature, and can be easily re-solidified by the cooling capacity (cooling means) used in the above-mentioned devices such as the cold storage freezer and the cold storage showcase. Even with the latent heat storage material having a melting temperature of -3 ° C to -12 ° C, the above-described problem of supercooling occurs, but no measure has been taken to add a supercooling inhibitor. This is -3 ° C ~
With a latent heat storage material having a melting temperature of -12 ° C, even if supercooling occurs, it can be dealt with by a compressor (corresponding from the equipment side), and a latent heat storage material having a melting temperature of -3 ° C to -12 ° C. Usually uses an aqueous solution of sodium carbonate, an aqueous solution of potassium nitrate, an aqueous solution of potassium hydrogen carbonate or an aqueous solution of ammonium bicarbonate as a refrigerant medium. However, a supercooling inhibitor exhibiting an excellent effect of preventing supercooling suitable for these inorganic aqueous solutions can be examined. The reason is that they did not. However, large regenerative freezers and regenerative showcases have a problem in that the amount of cold storage material increases and the capacity of the compressor must be increased. From the viewpoint of cost reduction, the melting temperature is -3C to -12.
It is desirable to use a supercooling inhibitor also in the cold storage material of ° C.

[0005]

SUMMARY OF THE INVENTION In view of the above circumstances, the present invention provides a latent heat storage material having a melting temperature between -3 ° C and -12 ° C. It is an object of the present invention to provide a latent heat storage material that can greatly reduce energy consumption.

[0006]

Means for Solving the Problems The present inventors have conducted intensive studies in order to achieve the above object, and as a result, have found that a latent heat storage material using an aqueous sodium carbonate solution having a melting temperature of -3 ° C to -12 ° C as a refrigerant storage medium. In the above, ammonium dihydrogen phosphate exhibits an excellent effect of preventing supercooling.
In a latent heat storage material using a potassium nitrate aqueous solution having a melting temperature of ° C as a refrigerant storage medium, sodium sulfate decahydrate was found to exhibit an excellent supercooling prevention effect, and the present invention was completed. That is, the present invention has the following features.

[0007] (1) A latent heat storage material obtained by dissolving ammonium dihydrogen phosphate as a supercooling inhibitor in a storage medium made of an aqueous sodium carbonate solution. (2) A latent heat storage material obtained by dissolving sodium sulfate decahydrate as a supercooling inhibitor in a refrigerant storage body comprising an aqueous solution of potassium nitrate. (3) The latent heat storage material according to (1) or (2), wherein the amount of the supercooling inhibitor is 0.5 to 7 parts by weight based on 100 parts by weight of the refrigerant (aqueous sodium carbonate solution or aqueous potassium nitrate solution). (4) The above (1) to (1) to in which the refrigerant storage body is packaged with a packaging material.
The latent heat storage material according to any of (3).

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The latent heat storage material of the present invention has a temperature of -3.degree.
An aqueous sodium carbonate solution used as a refrigerant storage medium having a melting temperature of ~ -12 ° C and ammonium dihydrogen phosphate dissolved therein as a supercooling inhibitor, or -3 ° C ~-
An aqueous solution of potassium nitrate was used as a refrigerant storage medium having a melting temperature of 12 ° C., and sodium sulfate 10
It is a hydrate dissolved.

In the case of using an aqueous sodium carbonate solution as the refrigerant, the concentration of sodium carbonate in the aqueous sodium carbonate solution is preferably 2 to 10% by weight, particularly preferably 3 to 8% by weight, and particularly preferably 4 to 7% by weight. %. In the case of using an aqueous solution of potassium nitrate as the refrigerant medium, the concentration of potassium nitrate in the aqueous solution of potassium nitrate is preferably 3 to 15% by weight, particularly preferably 8 to 12% by weight.
%, Particularly preferably 9 to 11% by weight.

The amount (dissolution amount) of ammonium dihydrogen phosphate in the embodiment and sodium sulfate decahydrate in the embodiment is usually 0.5 to 7 parts by weight per 100 parts by weight of the refrigerant body. , Preferably 1 to 5
Parts by weight. If the amount is less than this range, it is difficult to obtain a sufficient effect of preventing supercooling, and the solidification temperature (melting point) of the inorganic aqueous solution (refrigerant) tends to increase from -3C to -12C. On the other hand, when the used amount (dissolved amount) is larger than this range, it tends to precipitate from the inorganic aqueous solution (refrigerant) and tends to impair the uniformity of the cold storage material. In addition, ammonium dihydrogen phosphate and sodium sulfate 1
The purity of the 0-hydrate is not particularly limited, but usually 95% or more is used.

In the embodiment of the present invention, when the concentration of the inorganic compounds (sodium carbonate and potassium nitrate) in the aqueous solution constituting the refrigerant storage medium is within the above-specified preferable range, the temperature difference between coagulation and melting is reduced, and the cold storage / discharge is performed. The cold temperature becomes close to a constant value, which is preferable as a refrigerant (cooling material). Although the purity of the inorganic compound in the aqueous inorganic solution constituting the refrigerant storage medium is not particularly limited, it is usually 9%.
More than 5% is used. As an example of a particularly preferable combination of the concentration of the refrigerant storage medium (aqueous potassium nitrate solution) and the used amount (dissolved amount) of the supercooling inhibitor (sodium sulfate decahydrate) in the embodiment, the concentration of potassium nitrate is 7 to 12% by weight. 1 to 5 parts by weight of sodium sulfate decahydrate per 100 parts by weight of an aqueous potassium nitrate solution. With such a configuration, in particular, 2
A favorable result that the difference between the solidification temperature and the melting temperature after the cycle becomes small can be obtained.

In the embodiment, ammonium dihydrogen phosphate is dissolved as a supercooling inhibitor, and in the embodiment, sodium sulfate decahydrate is dissolved as a supercooling inhibitor. You may use together with other well-known cooling inhibitors other than these. Such other known supercooling inhibitor is a known compound known as a supercooling inhibitor of a refrigerant storage medium having a melting temperature other than the refrigerant storage medium having a melting temperature of −3 ° C. to −12 ° C. is there.

In the present invention, the above-mentioned water-soluble inorganic salt (ammonium dihydrogen phosphate in the embodiment) and sodium sulfate decahydrate in the embodiment are contained in a refrigerant storage medium (aqueous sodium carbonate solution in the embodiment) and potassium nitrate aqueous solution in the embodiment. In addition to the above, other substances may be added as long as the object of the present invention is not impaired. For example, various gels such as water-absorbent resins (eg, starch-based, acrylate-based, poval-based, carboxymethylcellulose-based), attapulgaya clay, gelatin, agar, silica gel, xanthan gum, arabic gum, arabic gum, guar gum, carrageenan, cellulose, konjac and the like Agent (thickener)
Is mentioned.

The method for producing the regenerative material of the present invention is not particularly limited. For example, pure water or ion-exchanged water placed in a container is charged with an inorganic compound (sodium carbonate in the embodiment) and potassium nitrate in the embodiment. ) Is added to a predetermined amount while gradually stirring, and then a water-soluble inorganic salt (sodium sulfate decahydrate of the embodiment, ammonium dihydrogen phosphate of the embodiment) as a supercooling inhibitor is gradually stirred. Add to a predetermined amount, mix well, add other additives at the same time or after this, stir and mix, or use an inorganic compound for refrigerant storage and a supercooling inhibitor (water-soluble inorganic salt). After mixing, the mixture may be poured into pure water or ion-exchanged water and stirred. In addition, water may be heated to about 50 ° C. in order to promote the dissolution of the inorganic compound for the refrigerant storage, the supercooling inhibitor (water-soluble inorganic salt), or other additives.

The latent heat storage material of the present invention can be used in various forms, and the form is not particularly limited. Usually, however, the storage medium in which the supercooling inhibitor (water-soluble inorganic salt) is dissolved is made of a metal having corrosion resistance, It is in the form of packaging (contained in a packaging material) with a packaging material made of an inorganic material or an organic material such as plastic. At this time, the shape of the package may be an appropriate shape according to the use of the cold storage material such as a lump, a plate, a sheet, or the like, the shape of the arrangement portion thereof, and the like. The packing material (container) is preferably air-tight and light-shielding from the viewpoint of maintaining the characteristics of the cold storage material, and the material and form for that purpose are selected. Further, even if the packaging material is in a form (for example, a bag shape) that allows deformation of the package after packaging, a form that does not substantially allow the deformation of the package (for example,
(A box shape made of a rigid body). Specifically, a container (box) made of aluminum, copper, stainless steel, or the like, or a container in which a coating for preventing corrosion is further provided is preferable. Also, when the packaging material is composed of a film,
It is preferable to form a composite film using a metal film such as aluminum for at least one layer.

[0016]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

(Embodiment 1) 5.9% N as refrigerant medium
a ₂ CO ₃ aqueous solution containing 100 parts by weight of NH as a supercooling inhibitor
_A latent heat storage material was prepared by dissolving 3 parts by weight of ₄ H ₂ PO ₄ . (Comparative Example 1) 100 parts by weight of a 5.9% Na ₂ CO ₃ aqueous solution as a refrigerant storage medium was mixed with Na ₂ SO ₄ .10 as a supercooling inhibitor.
H ₂ O was dissolved in 3 parts by weight to prepare a latent heat storage material. (Example 2) in 9.7% KNO ₃ aqueous solution 100 parts by weight of the cold-storage medium as a supercooling inhibitor Na ₂ SO ₄ · 10H
₂ O was dissolved in 3 parts by weight to prepare a latent heat storage material. Comparative Example 2 NH ₄ H ₂ PO ₄ as a supercooling inhibitor was added to 100 parts by weight of a 9.7% KNO ₃ aqueous solution as a refrigerant storage medium.
The parts by weight were dissolved to prepare a latent heat storage material. (Comparative Example 3) Na ₂ SO ₄ · 1 to 16.5% KHCO ₃ solution 100 parts by weight of the cold-storage medium as a supercooling inhibitor
A latent heat storage material was prepared by dissolving 3 parts by weight of 0H ₂ O.

The solidification temperature and melting temperature of each of the latent heat storage materials of the above Examples and Comparative Examples were measured by the following methods. In addition, as Reference Examples 1 to 3, a refrigerant storage body in which a supercooling inhibitor was not dissolved (a 5.9% Na ₂ CO ₃ aqueous solution,
9.7% KNO ₃ aqueous solution, 16.5% KHCO ₃ aqueous solution)
The coagulation temperature and melting temperature were measured.

[Measurement of solidification temperature and melting temperature] DSC
(Differential scanning calorimeter) After cooling from 10 ° C. to -30 ° C. at a temperature lowering rate of 2 ° C./min and holding for 3 minutes, a temperature increasing rate of 2 ° C./min.
After raising the temperature to −3 ° C. for 5 minutes and maintaining the temperature for 5 minutes, cooling to -20 ° C. again at a temperature lowering rate of 2 ° C./minute and maintaining the temperature for 3 minutes, then increasing the temperature at a rate of 2 ° C./minute to 10 ° C. I do. The solidification and melting are performed twice to check the degree of supercooling. The solidification temperature and melting temperature of the regenerator material were derived from the intersection of the baseline of the exothermic or absorption peak and the tangent of the peak.

[0020]

[Table 1]

The determination in the first cycle in the above table is the result of comparing the solidification temperature with the reference example in which the supercooling inhibitor is not dissolved. That is, those having a solidification temperature higher than the solidification temperature of the reference example were judged to be acceptable (（), and those having a solidification temperature lower than the solidification temperature of the reference example were rejected (x).
It was determined. The determination in the second cycle is a result of comparison with the solidification temperature in the first cycle, and the one in which the solidification temperature in the second cycle is higher than the solidification temperature in the first cycle is judged as pass (合格), and When the solidification temperature was lower than or equal to the solidification temperature in the first cycle, the sample was judged as failed (x).

From Table 1, the melting temperature between -3 ° C. and -12 ° C.
In the latent heat storage material having_TwoCO_ThreeWater soluble
Ammonia dihydrogen phosphate as a supercooling inhibitor when it is a liquid
By using nickel, supercooling is sufficiently suppressed and
9.7% KNO _ThreeIf it is an aqueous solution
Use sodium sulfate decahydrate as a cooling inhibitor
Thus, it can be seen that the supercooling is sufficiently suppressed.

[0023]

As is apparent from the above description, according to the present invention, a latent heat storage material having a melting temperature in the range of -3 ° C to -12 ° C, in which supercooling is sufficiently suppressed, is obtained. be able to. Therefore, wasteful coagulation energy is not consumed in the coagulation-melting cycle, and a low-cost cold storage system can be realized.

Claims (4)

[Claims] 1. A latent heat regenerative material obtained by dissolving ammonium dihydrogen phosphate as a supercooling inhibitor in a refrigerant storage medium comprising an aqueous solution of sodium carbonate. 2. A latent heat storage material comprising sodium sulfate decahydrate dissolved as a supercooling inhibitor in a refrigerant storage medium comprising an aqueous solution of potassium nitrate. 3. The latent heat storage material according to claim 1, wherein the amount of the supercooling inhibitor is 0.5 to 7 parts by weight based on 100 parts by weight of the refrigerant (aqueous sodium carbonate solution or aqueous potassium nitrate solution). 4. The latent heat storage material according to claim 1, wherein the refrigerant storage body is packaged with a packaging material.