JPH0115549B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention uses sodium sulfate decahydrate (Na ₂ SO ₄ .
The purpose is to prevent the phase separation phenomenon that occurs due to repeated heat dissipation and maintain stable heat storage performance over a long period of time _. It has been improved to do so. Na ₂ SO ₄・10H ₂ O has a melting point of about 32℃ and about
It has a latent heat of 60 cal/g, is obtained in large quantities at low cost as a by-product of the rayon spinning process or petroleum desulfurization process, and is non-toxic, making it a useful latent-heat type heat storage material. Also
Na ₂ SO ₄ · 10H ₂ O has the property that its melting point can be changed by creating a eutectic; for example, by adding sodium chloride, ammonium chloride, etc. to Na ₂ SO ₄ · 10H ₂ O. Depending on the amount added, the melting point can be lowered to around 10°C. The amount of latent heat storage is about 44 cal/g when 0.5 mole of sodium chloride and 0.5 mole of ammonium chloride are added to 1 mole of Na ₂ SO ₄ .10H ₂ O (melting point: about 13°C). Therefore, Na ₂ SO ₄ 10H ₂ O and its eutectic are
It is suitable as a latent heat storage material for solar heat, waste heat, residual heat recovery and storage systems, and cold heat storage systems from air conditioners operated on nighttime power to alleviate power peaks in the summer. However, when using Na ₂ SO ₄ .10H ₂ O as a latent heat storage material for a long period of time, there are two problems. One of these is the so-called supercooling phenomenon in which pseudo-solidification does not occur even after passing the pseudo-solidification point during cooling, and the other is the phenomenon in which unmelted crystals ( Anhydrous sodium sulfate) is precipitated, and this precipitate no longer participates in the phase change, resulting in a so-called deterioration of the amount of heat storage, in which the amount of latent heat storage decreases. It is disclosed in US Pat. No. 2,667,664 that the supercooling phenomenon can be solved by adding sodium tetraborate decahydrate as a nucleating substance. In order to avoid deterioration of heat storage capacity,
A method has been proposed in which a thickening agent is added to turn the solution into a gel state to prevent precipitation of anhydrous sodium sulfate and to uniformly disperse and maintain the solution in the solution. Typical thickening agents include sawdust, wood pulp, carboxymethyl cellulose, methyl cellulose, lees, organic polymer compounds such as organic alginates, polyacrylates, and cross-linked polyacrylates, finely powdered silica, and diatom. soil, silica gel, bentonite,
It is an inorganic material such as attapal guide type clay. Furthermore, oleate salts are described in JP-A No. 57-200482, organic sulfonates are described in JP-A-58-132075, polyethylene oxides and ethoxylated amines, and hemosamethalin are described in JP-A-57-159871. Adding a crystal habit modifier such as sodium chloride,
A method has been proposed to prevent the deterioration of the amount of heat storage. However, even if precipitation of anhydrous sodium sulfate is prevented by such a method and a crystal habit modifier is added, crystal particles of anhydrous sodium sulfate will grow due to repeated melting and coagulation, and only the surface of the particles will grow during solidification. The particles tend to form hydrated salts and the center of the particles remains anhydrous, and the amount of heat storage decreases with cycling, which is not a satisfactory condition. In view of these circumstances, the present inventors have conducted various tests and researches, and have found that by adding water to Na ₂ SO ₄ 10H ₂ O and bringing Glauber's salt decahydrate close to a saturated solution of Glauber's salt, melting and solidification can be reduced. We thought that it might be possible to prevent the formation and growth of anhydrous sodium sulfate crystal particles that occur during cycles, and although adding water alone cannot prevent heat storage deterioration, we added a silicone antifoaming agent and a chelating agent. It was discovered that the deterioration of the amount of heat storage can be prevented by this, and the present invention was completed. In carrying out the present invention, Na ₂ SO ₄ .
30 to 50 parts by weight of water should be added to 100 parts by weight of 10H ₂ O. If it is less than 30 parts by weight, a sufficient effect of preventing heat storage deterioration will not be obtained, while if it exceeds 50 parts by weight, Although this method has the effect of preventing deterioration of the amount of heat storage, it is not practical because the amount of heat storage per unit weight of the heat storage material decreases. According to the invention, for example Na ₂ SO ₄ .10H ₂ O100
The heat storage material is made by adding 35 parts by weight of water, 0.01 parts by weight of methyl silicone oil, and 0.5 parts by weight of Cuperon.
Even after 500 cycles of melting and solidification, it maintains a melting point of 29°C and a heat storage capacity of 36 cal/g.
Compared to the initial heat storage amount, the heat storage amount deteriorates slightly.
It can be suppressed to 2 cal/g. As is clear from each example, such an effect of preventing deterioration of heat storage amount can be achieved by adding water, silicone-based antifoaming agents such as methyl silicone oil, methylphenyl silicone oil, and methyl hydrogen silicone oil, and cuperone,
This occurs specifically when a chelating agent such as ethylenediaminetetraacetic acid disodium salt, nitrilotriacetic acid disodium salt, or triethanolamine is added, and even if any of these is absent, the desired effect will not be achieved. I can't list them. In carrying out the present invention, known sodium tetraborate decahydrate is used to prevent supercooling, and
In order to prevent precipitation of the nucleating agent and unmelted crystals, carboxymethylcellulose is used as a thickening agent.
A water-soluble organic polymer compound such as methylcellulose, organic alginate, polyacrylate, or crosslinked polyacrylate should be used in combination. Furthermore, the present invention can be similarly applied to eutectic products such as Na ₂ SO ₄ .10H ₂ O, sodium chloride, ammonium chloride, etc., and the durability as a heat storage material can be greatly improved. The present invention will be specifically explained below using Examples and Comparative Examples. Example 1 To 100 parts by weight of Na ₂ SO ₄ 10H ₂ O, 35 parts by weight of water, 0.01 part by weight of methyl silicone oil, Cuperone
A sample containing 0.5 parts by weight, 4 parts by weight of carboxymethyl cellulose as a thickening agent, and 4 parts by weight of sodium tetraborate decahydrate as a nucleating agent was melted and mixed in a constant temperature water bath at 40°C. Put 100g of the heat storage agent obtained in this way into a polyethylene cylindrical container with an inner diameter of 45mm and a height of 60mm, prepare four samples by inserting thermocouples and sealing them, and temperature cycle the three of them at 40℃ and 15℃. The sample was placed in a constant temperature bath set to repeat heating and cooling. Perform long repeated cycles, 100, 250,
After every 500 cycles, one sample was taken out and the phase change temperature and amount of latent heat storage were measured. In addition, the other one is the initial stage (number of cycles is 0)
The money was spent on measurements. To measure the amount of latent heat storage, the sample is kept in a constant temperature bath at 40°C for one day, then immersed in a juice bottle filled with ice at 10 to 15°C, and the temperature changes are measured until the water temperature and sample temperature become the same. The amount of latent heat storage was calculated by reading and subtracting the sensible heat content of the container and sample. The test results thus obtained are shown in Table 1.

[Table] As can be seen from the table, the performance of the composition of this example hardly changed even after heating and cooling were repeated 500 times. Comparative Example 1 In Example 1, a similar durability test was conducted for a composition without the addition of methyl silicone oil and cuperone. The results are shown in Table 2.

[Table] As can be seen from the table, the amount of heat stored in the composition of this example was significantly reduced by repeated heating and cooling. Comparative Example 2 In Example 1, when a similar durability test was conducted on the composition without adding only methyl silicone oil, the amount of latent heat storage after 500 cycles was
It decreased from 38.0 cal/g to 30.0 cal/g. Comparative Example 3 When a similar durability test was conducted on a composition in which only cuperone was not added in Example 1, the amount of latent heat storage was 35.0 cal/g after 500 cycles.
It decreased from 31.0 cal/g to 31.0 cal/g. Examples 2 and 3 Compositions were prepared in which 0.01 parts by weight of methylphenyl silicone oil and methyl hydrogen silicone oil were added in place of methyl silicone oil in Example 1, and the same durability tests were conducted. Table 3 shows the results after 500 cycles.

[Table] Examples 4 to 6 A composition was prepared in which 0.5 parts by weight each of ethylenediaminetetraacetic acid disodium salt, nitrilotriacetic acid disodium salt, and triethanolamine were added in place of cuperone in Example 1, and the same composition was prepared. We conducted a durability test. Table 4 shows the results after 500 cycles.

[Table] Example ₇ 8 parts by weight of _MaCI , 35 parts by weight of water, 0.01 _parts by weight of methyl silicone oil, 0.5 parts by weight of cuperone, and cross-linked polyacrylic acid (as a thickening agent) Product name: “Hibis Wako 103”)
A composition was prepared containing 4 parts by weight of sodium tetraborate decahydrate as a nucleating agent, and the sample was melted and mixed in a constant temperature water bath at 40°C. A test similar to that in Example 1 was conducted using the obtained heat storage material. The test results are shown in Table 5.

[Table] Comparative Example 4 When a similar durability test was conducted on the composition in Example 7 without the addition of methyl silicone oil and cuperone, the amount of latent heat storage decreased from 31 cal/g to 21 cal/g after 500 cycles. .

Claims (1)

[Claims] 1. In a heat storage material mainly consisting of sodium sulfate decahydrate or a eutectic of sodium sulfate decahydrate and other salts, sodium tetraborate decahydrate, and a thickening agent, water is converted into a silicon-based A heat storage material characterized by the addition of an antifoaming agent and a chelating agent. 2 For 100 parts by weight of sodium sulfate decahydrate or sodium sulfate decahydrate in the eutectic, add water
The heat storage material according to claim 1, wherein 30 to 50 parts by weight of the heat storage material is added. 3. The heat storage material according to claim 1, wherein the silicone antifoaming agent added is at least one of methyl silicone oil, methylphenyl silicone oil, and methyl-hydrogen silicone oil. 4. Claim 1, wherein the chelating agent added is at least one of cuperone, ethylenediaminetetraacetic acid disodium salt, nitrilotriacetic acid disodium salt, and triethanolamine.
Thermal storage material described in section.