JPS60130671A - Thermal energy storage material - Google Patents

Abstract

PURPOSE:To provide a thermal energy storage material which does not cause a supercooling phenomenon, has stable heat absorption and heat dissipation performances and a large thermal energy storage capacity per unit weight and is inexpensive, by blending a specified nucleating agent with a sodium acetate/ water thermal energy storage material compsn. CONSTITUTION:At least one compd. selected from sodium dithionate, potassium pyrosulfate, potassium sulfite, lithium sulfate, potassium tellurite and potassium perchlorate is used as a nucleating agent. Not more than 40pts.wt. said nucleating agent is blended with 100pts.wt. system consisting of 40-80wt% sodium acetate and 60-20wt% water.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a latent heat storage material based on acetic acid (IJ) trihydrate.

Conventional Structures and Problems There are generally known heat storage materials that utilize the sensible heat of substances and those that utilize latent heat. Heat storage materials that use latent heat have a larger amount of heat storage per unit weight or unit volume than heat storage materials that use sensible heat, and only a small amount is required to store the required amount of heat. It becomes possible to downsize heat storage devices. In addition, a heat storage material that uses latent heat has the characteristic that unlike a heat storage material that uses sensible heat, the temperature does not drop with heat radiation, and instead radiates heat at a constant temperature at a transition point. In particular, heat storage materials that utilize the latent heat of fusion of inorganic hydrates are known to have a large amount of heat storage per unit volume.

By the way, conventionally sodium acetate trihydrate (NaOH5
COO.3 H2O (melting point: 58°C) I-i It has a large amount of heat storage among inorganic hydrates, and was considered to be a promising heat storage material for heating, for example. However, once NaCH3000/3H20 is melted, it tends to become supercooled, so the melt is usually -2o
Supercooling cannot be broken unless it is cooled to around °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 to the amount of heat stored using the latent heat of fusion.

Purpose of the invention The present invention prevents the supercooling phenomenon of IJium acetate,
The purpose of the present invention is to provide a heat storage material that is inexpensive, has stable heat absorption and radiation performance, and has a large amount of heat storage per unit weight or unit volume.

Structure of the Invention The most characteristic feature of the present invention is that the main component is a system consisting of sodium acetate (NaCH3COO) and water, and is used as a crystal nucleation material to prevent supercooling during crystallization of NaCJCOO.3H20. , sodium dithionate (Na2S206) + potassium pyrosulfate (K2S2
07) + Potassium sulfite (K2S03) + Lithium sulfate (Li2SO4), Potassium tellurite (K
2TeO3) and potassium perchlorate (KClO2)
The method consists of mixing at least one compound selected from the group consisting of the following compounds into the above-mentioned system consisting of sodium acetate and water.

By the way, FIG. 1 shows a phase diagram of the NaCH3COOH2O system. From this figure, NaCJCiOO60.3% by weight
A system consisting of 9.7% by weight of H2O and NaCH, Co
It corresponds to the o -CH2O composition, and it can be seen that with this composition, melting and solidification occur at about 58°C unless supercooling occurs. In addition, NaCH3COO50% by weight and H2O60
% system has a uniform Na at temperatures above about 55°C.
This becomes a GH5COO aqueous solution. This homogeneous aqueous solution was heated to 55°C.
When cooled below, if supercooling does not occur, NaCJ
COO.5H20 begins to crystallize, and as it cools, the proportion of Na CHs COO.3H20 crystals increases. When cooled to about 30°C, 60% by weight N
Approximately 60 cm of the total mass of the aCH5000-H20 system is Na(1
(scOo ・3H20 crystals, remaining 40% is N
acl (exists as a 3coo aqueous solution. Therefore, N
The system of aCH5COO50% by weight and H2O3○ weight is 5
When cooled from a temperature of 5°C or higher to 3o'G, there is almost no supercooling, and if NaGHsGOO.3H2o is successfully crystallized, the unit mass will be reduced by 9. NaCHsOOOO
・A latent heat of approximately 60 cm is obtained in the case of CH2O composition. Furthermore, as the proportion of NaCH5COOH2O water increases, the amount of sensible heat that is stored increases, and it is natural that the amount of stored heat due to sensible heat increases. Cutting Na
By controlling the ratio of CH3COO and H2O, heat storage by latent heat of fusion and heat storage by sensible heat are performed together, and by controlling the ratio of heat storage by latent heat and sensible heat, the range of applications of heat storage materials is greatly expanded. . However, if a system with a low concentration of Na CHs COO is used, the characteristics of a heat storage material using latent heat of fusion will be lost;
It is appropriate to use a NaCH3COO-H2O system containing N amount of 1 or more.

Conversely, in the Na(Hy, Coo -H2O system)
As the content of CH5COO increases, as is clear from Figure 1, Na(1(3000 to 6o, triple jt
% or more, when cooling from a temperature of 58°C or higher to a temperature below that temperature, if the supercooling is broken,
NaC4000.3H20 crystallizes. However, naturally the entire system does not become NaOH3000.3H20, and a portion remains as NaCH3COO. So, NaCJCO
NaCH,coo-H2 containing more than 80% by weight of O
In the O system, the amount of latent heat per unit mass is NaCH3COO・3
Since it is less than about 50 cm in the case of H,,O composition, it is not practical.

Therefore, it is considered appropriate that the actually used NaCH5COO-H,,O system contains Na(J(5000) in a range of 80% by weight or less.

In addition, dithionic acid (Na2S206) and potassium pyrosulfate (K2S207) are used as crystal nucleation materials.
).

Potassium sulfite (K2SO5) + Lithium sulfate (Li
2S04), potassium tellurite (K2S207), and iM potassium chlorite (KClO2) are NaO
uacH3coo containing 58% by weight or more of H5COO
In the case of the H2O system, about 1 part by weight of each is sufficient for 100 parts by weight of the system, and of course, even if more than that is added, the effect is sufficient to prevent supercooling.

In the case of a system in which NaCH3coo is less than 68% by weight, the amount of crystal nucleating material dissolved in the NaCH3COOH20 system increases compared to a system in which NaCH3coo is contained in an amount of 58% by weight or more. The amount must be increased from the above value.

However, when the heat storage material according to the present invention is used in a heat storage device for air conditioning, etc., it is considered normal to use a heat storage material of about 100 to 100 degrees. In such a case, N
Even in the molten state of a GHs COO 3H20 crystal, the composition is not uniform throughout, and the second part contains NaG.
A solution with a low concentration of H5C00 is present, and a precipitate of the crystal nucleating material and a liquid with a high concentration of Na CH3G OO and the crystal nucleating material are present at the bottom. Therefore, even if the mixed amount of the crystal nucleation material is much smaller than the minimum amount for forming a uniform solution, the crystal nucleation material is Na0Hs.
It acts as a crystal nucleation material without being dissolved in the Coo-H20 system. The minimum amount of the crystal nucleation material necessary for crystal nucleation, that is, the lower limit of the mixing amount, is the NaCH5 used.
Since it depends on the amount of the COO-H2O system and the shape of the container housing the heat storage material, it may be determined appropriately depending on the usage pattern.

However, adding too much crystal nucleation material is not preferable as a heat storage material, and leads to a decrease in the amount of heat storage in the heat storage material as a whole.

Therefore, in practice, the mixing ratio of the crystal nucleation material is N
40 parts by weight for 100 parts by weight of aCH3COO-H20 system
It is desirable not to exceed parts by weight.

Description of Examples Example 1 2010 oz of NaCJCOO"3H and 1 q of the crystal nucleation material shown in Table 1 were placed in a beaker and heated to 75°C in a water bath to form NaCI (sCOO.
All of the 3H20 was melted. This mixture has an inner diameter of 100
The container was placed in a cylindrical container with a length of 100 πm and was sealed with a stopper equipped with a thermocouple insertion tube. The container was placed in a water bath and heated and cooled continuously between TO'C and 40'C.

Figure 2 shows the degree of supercooling, that is, the solidification temperature, and the temperature at which supercooling breaks when a sample is repeatedly heated and cooled 100 times using sodium dithionate as a crystal nucleation material. This figure shows how the difference in . The horizontal axis of the figure shows the number of repetitions of the heating/cooling cycle on a logarithmic scale, and the vertical axis shows the degree of supercooling (°C). From this figure, even if the heating and cooling of the heat storage material of this example is repeated ioo times, the degree of supercooling remains stable in the range of 3 to 4 degrees Celsius, and the supercooling prevention function remains effective without deterioration. I can see that you are doing it.

By the way, Figure 3 shows the degree of supercooling when potassium pyrosulfate is used as the crystal nucleation material, Figure 4 shows potassium sulfite, Figure 5 shows lithium sulfate, Figure 6 shows potassium tellurite, and Figure 7 shows the degree of supercooling when potassium pyrosulfate is used as the crystal nucleation material. The figure shows the case using potassium perchlorate.

In all of the samples of these Examples, the degree of supercooling is stable at around 5°C.

Example 2 500 g of crystal nucleus forming material and an inner diameter of 8 with a heater inside.
The sample was placed in a cylindrical container with a height of 0 cm and a height of 9 ocIn, and was sealed with a lid equipped with a thermocouple insertion tube. Na()(5COO・3H20 was heated to γo”C using a heater inside the container, and all of the Na CH5GOO・3H20 was melted. Then, heating by the heater was stopped and the mixture was cooled. As a crystal nucleation material, 2 Sodium thionate, potassium pyrosulfate, potassium sulfite, lithium sulfate.

In both cases where potassium tellurite and potassium perchlorate were used, supercooling was broken at around 53°C, and the temperature inside the container rose to 58°C. After that, heating and cooling were repeated 50 times, but in each case, the supercooling was broken stably at a degree of supercooling of about 5°C, confirming that the heat storage material of this example sufficiently functions as a heat storage material. Ta.

Comparative Example 1 1000g of NaCH3COO-3H, 01000g was stored in the same container as in Example 1, heated to 70°C, and NaG
All H5G OO・3H20 was melted. after that,
When cooled, even if it reached room temperature, N a OH3GO
O.3H20 did not crystallize.

Comparative Example 2 NaCH3COO-3H2050o1 (7) was stored in a container similar to Example 2, and NaCH3C was heated using a heater inside the container.
Heating OO・3H20 to 70”C, NaCH3
All COO.3H20 was melted. After that, when the heating by the heater was stopped and the temperature was cooled, the temperature was supercooled to room temperature.
In the COO-H2O system, NaCH, 5Coo ・3 H2
Sodium dithionate (Na
2S206), potassium pyrosulfate (K2S207).

Potassium sulfite (X2SO5), lithium sulfate (Li
2SO4) + potassium tellurite (K2S207)
Since it is a mixture containing at least one selected from the compound group consisting of potassium perchlorate (xcio4) and potassium perchlorate (xcio4), it has stable heat absorption performance with almost no supercooling, is inexpensive, and has a large amount of heat storage. It has become a thing. Although the examples show cases in which these crystal nucleation materials are used alone, equivalent effects can be obtained even when a plurality of these materials are used in combination.

Effects of the Invention The heat storage material of the present invention is applicable 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.

[Brief explanation of the drawing]

Figure 1 is a phase diagram of the acetic acid (IJ) water system. FIG. 2 to FIG. 7 show how the degree of supercooling changes when the heat storage material according to the embodiment of the present invention is repeatedly heated and cooled 100 times. Name of agent: Patent attorney Toshio Nakao and 1 other person
1 Figure 7420 s, c〃, ca turtle to, , /VarH3
C6'0 2nd figure f /θ lθρ Enri-hikishi Kidadan (@) 3rd figure Shigeru tI) iJL rotation (TfJn 4th figure f /ρ lθθ, attacking nest・) Top 4 Circling (＠) Figure 5 Thread reach @ 歇 (@n Figure 6 Chrysanthemum 7 Figure! θg Me East 1) Support 10 times (Ro)

Claims (3)

[Claims] (1) Sodium acetate (NaCH3COO) and water (H2
O), sodium dithionate (Na252o6) + potassium pyrosulfate (K2B4O
7). Potassium sulfite - (K2SO3) + Lithium sulfate (L
i25O4) + potassium tellurite (K2TeO,)
and at least one crystal nucleation material selected from the group of compounds consisting of potassium perchlorate (KClO2). (2) The heat storage material according to claim 1, characterized in that in a system consisting of sodium acetate and water, 40 to 80 weight percent of sodium acetate is contained. (3) The heat storage material according to claim 1, characterized in that the amount of the crystal nucleating agent added to 100 parts by weight of the system consisting of sodium acetate and water does not exceed 4 parts by weight.