JPS645634B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a latent heat storage material mainly composed of sodium acetate trihydrate. Conventional Technology Sodium acetate trihydrate (NaCH ₃ COO.3H ₂ O melting point: 58°C) has a large amount of heat storage, and has been seen as a promising heat storage material for heating, for example. However, once NaCH ₃ COO.3H ₂ O is melted, it is very likely to become supercooled, so the supercooling cannot be broken unless the molten liquid is cooled to about -20°C. The supercooled state is a phenomenon in which even if the material is cooled to the freezing point, the latent heat of fusion is not released and the material is cooled below that temperature, which is a fatal drawback for heat storage materials that utilize the latent heat of fusion. To solve this problem, NaCH ₃ COO・
Various additives have been proposed to promote the crystallization of 3H ₂ O (Japanese Patent Application Laid-Open No. 147580-1983). Problems to be Solved by the Invention However, the heat resistance temperature of currently proposed crystal nucleation materials is 85°C or lower, so NaCH ₃ COO 3H ₂ O containing these crystal nucleation materials is heated to about 90°C. When heated, it loses its function as a heat storage material in a short period of time (Bull.Chem.Soc.Jpn., 57, 561
―563 (1984)). In other words, the current sodium acetate 3
Water-salt-based latent heat storage materials cannot rapidly store heat using a heat source of 85°C or higher, and this has become a major problem in practical use. Means for solving the problems The feature of the present invention is that NaCH ₃ COO is
Contains in the range of 55% to 73% by weight
In a system consisting of NaCH ₃ COO and H ₂ O, NaCH ₃ COO・
As a crystal nucleation material for preventing supercooling during crystallization of 3H ₂ O, lithium fluoride whose surface is at least partially covered with sodium acetate trihydrate is included. Preferably, the content of lithium fluoride is in the range of 0.1 parts by weight to 40 parts by weight based on 100 parts by weight of the system consisting of sodium acetate and water. Effect The heat storage material of the present invention has almost no supercooling phenomenon, has high heat resistance, and has an extremely stable performance from the first heat storage/release.The amount of heat stored per unit weight or per unit volume This is a large one. Example 60 g of commercially available special grade NaCH ₃ COO・3H ₂ O was heated to 80°C and melted, and 40 g of commercially available special grade LiF was poured into it.
g was added and thoroughly stirred to obtain a viscous liquid. Cool this viscous liquid and use seed crystals to
Crystallize NaCH ₃ COO・3H ₂ O,
A composition containing NaCH ₃ COO.3H ₂ O and LiF was obtained.
Thoroughly grind this composition to form NaCH ₃ COO・
A supercooling prevention material for 3H ₂ O was obtained. Using this supercooling prevention material, each sample was adjusted to have the composition shown in Table 1. The latent heat of fusion of each sample was measured using a differential scanning calorimeter, and the amount of latent heat per 1 g of each sample was calculated using the results. It is the second
Shown in the table.

【table】

【table】

[Table] In addition, 10 g of each sample was sealed in a plastic container. 10 containers filled with this heat storage material were heated in a constant temperature chamber for 10 hours, then cooled to 40℃, and within 2 hours NaCH ₃ COO・
The heat resistance of the heat storage material was evaluated based on whether 3H ₂ O crystallized. The upper limit temperature at which crystallization of NaCH ₃ COO·3H ₂ O was observed in all 10 samples was used as the heat-resistant temperature. Table 2 also shows the heat resistance temperature of each sample determined in this way. In other words, the second
If each sample is heated above the heat-resistant temperature shown in the table, some of the 10 samples will become supercooled without solidifying. For example, in the case of sample 3, when heat treatment was performed at 94°C, 6 out of 10 samples were supercooled. By the way, the amount of latent heat is 40 cal/g or more, and
Samples with a heat resistance temperature of 85°C or higher have a sufficiently large amount of heat storage and a sufficiently high heat resistance, so they are considered to be fully practical as latent heat storage materials capable of rapid heat storage. As is clear from Table 2, the desirable composition range is NaCH ₃ COO
Contains in the range of 55% to 73% by weight
LiF is contained in a range of 0.1 to 50 parts by weight based on 100 parts by weight of the system consisting of NaCH ₃ COO and H ₂ O. 1 kg of a sample having the same composition as Sample 9 was placed in a cylindrical container with an inner diameter of 100 mm and a length of 100 mm, and the container was sealed with a stopper equipped with a thermocouple insertion tube. When the container was placed in a water bath and heated and cooled 1000 times between 90°C and 40°C, stable heat storage and heat dissipation characteristics were obtained from the first time, and no deterioration was observed. It was confirmed that the heat storage material of the invention has sufficient characteristics as a latent heat storage material capable of rapidly storing heat. What I have explained so far is NaCH ₃ COO・3H ₂ O and
This is a NaCH ₃ COO/3H ₂ O-based latent heat storage material prepared using a composition containing LiF as a supercooling prevention material.
A similar heat storage material is made by mixing sodium acetate trihydrate and lithium fluoride in proportions that give the respective compositions, then heating to melt the sodium acetate trihydrate, then cooling and using seed crystals. , can also be produced by crystallizing sodium acetate trihydrate around lithium fluoride. The heat storage material produced by such a manufacturing method also showed the same amount of latent heat storage and heat resistance characteristics as when a composition containing NaCH ₃ COO.3H ₂ O and LiF was used as a supercooling prevention material. Effects of the Invention As shown above, the heat storage material of the present invention has
A system consisting of NaCH ₃ COO and H ₂ O containing NaCH ₃ COO in a range of 55% to 73% by weight contains lithium fluoride whose surface is at least partially covered with NaCH ₃ COO・3H ₂ O. It has a high heat resistance temperature, and therefore can rapidly store heat from a high-temperature heat source, exhibits stable heat storage and heat dissipation performance from the first use, is inexpensive, and has low heat storage per unit weight or unit volume. The quantity is becoming large. Therefore, the heat storage material of the present invention can be applied not only to heat storage devices for air conditioning, but also to all fields that utilize heat storage, such as heat storage type heat insulators.

Claims (1)

[Claims] 1. 55% by weight of sodium acetate (NaCH ₃ COO)
At least one portion of the surface _of the
A heat storage material characterized in that part of the material contains lithium fluoride covered with sodium acetate trihydrate. 2 The content of lithium fluoride is from 0.1 part by weight to 100 parts by weight of the system consisting of sodium acetate and water.
The heat storage material according to claim 1 in a range of 40 parts by weight. 3. A method for producing a heat storage material, which comprises adding and mixing a composition containing at least sodium acetate trihydrate and lithium fluoride to a system consisting of sodium acetate and water.