JP2019151751A - Heat storage composition and heat storage body - Google Patents

Abstract

To provide a heat storage composition useful for reducing energy consumption for preventing overcooling while containing disodium hydrogen phosphate dodecahydrate as a heat storage material.SOLUTION: A heat storage composition contains a heat storage material which is disodium hydrogen phosphate dodecahydrate, and fatty acid salt. The action of the fatty acid salt makes it possible to prevent overcooling of the heat storage material which is disodium hydrogen phosphate dodecahydrate without keeping part of the heat storage composition constantly at 35°C or less.SELECTED DRAWING: Figure 2

Description

  The present disclosure relates to a heat storage composition and a heat storage body.

  Conventionally, from the viewpoint of effectively using thermal energy in industry or home, proposals have been made to use a salt hydrate that changes phase between a solid phase and a liquid phase as a heat storage material. In particular, disodium hydrogen phosphate dodecahydrate has a melting point of 35 ° C. and a heat storage density of about 265 kJ / kg, and is attracting attention as a desirable option for a heat storage material. On the other hand, even if the heat storage material is cooled to a temperature equal to or lower than the melting point in order to change the liquid heat storage material to a solid phase, supercooling that does not solidify the heat storage material may occur. Technology has also been proposed.

  For example, Patent Document 1 describes a method for preventing overcooling of a latent heat storage material composition containing disodium hydrogen phosphate 12 hydrate as a main material. In this method, a part of the latent heat storage material composition is always kept at 35 ° C. or lower. Thereby, the seed crystal of disodium hydrogenphosphate 12 hydrate is preserved.

JP-A-8-85785

  According to the method described in Patent Document 1, energy is consumed in order to always keep a part of the latent heat storage material composition at 35 ° C. or lower. Therefore, the present disclosure provides a heat storage composition that is advantageous for reducing energy consumption for suppressing supercooling while containing disodium hydrogen phosphate dodecahydrate as a heat storage material.

This disclosure
A heat storage material that is disodium hydrogen phosphate dodecahydrate,
Fatty acid salt,
A heat storage composition is provided.

  The heat storage composition of the present disclosure is advantageous for reducing energy consumption for suppressing supercooling while containing disodium hydrogen phosphate dodecahydrate.

FIG. 1 is a diagram illustrating an example of a heat storage body of the present disclosure. FIG. 2 is a cross-sectional view of the heat storage body of FIG. 2 taken along the line II-II when viewed from the direction of the arrow. FIG. 3 is a graph showing the relationship between the limit degree of supercooling and the ratio (Ws / Wp) of the weight (Ws) of sodium stearate to the weight (Wp) of disodium hydrogenphosphate dodecahydrate.

(Knowledge that became the basis of this disclosure)
When using salt hydrate which shows supercooling as a heat storage material, in order to change a heat storage material into a solid phase, it is necessary to cool a heat storage material to temperature lower than melting | fusing point. For this reason, the energy consumption required for cooling of a thermal storage material will increase. This has been a major problem in using a salt hydrate exhibiting supercooling as a heat storage material. In order to solve this problem, it is conceivable that an additive having a crystal structure that matches the crystal structure of the heat storage material coexists with the heat storage material. For example, sodium tetraborate decahydrate having a melting point of 68 ° C. is known to be effective as a supercooling preventive agent for a heat storage material that is sodium sulfate decahydrate having a melting point of 32 ° C. However, it is difficult to say that the additive desirable for suppressing the supercooling of the heat storage material, which is disodium hydrogen phosphate dodecahydrate, has been sufficiently studied. Accordingly, the present inventors have made many trials and errors in order to find an additive that is desirable for suppressing the supercooling of the heat storage material that is disodium hydrogen phosphate dodecahydrate. As a result, the present inventors have newly found that when the heat storage composition contains a fatty acid salt, the supercooling of the heat storage material can be advantageously suppressed.

(Outline of aspects according to the present disclosure)
The heat storage composition according to the first aspect of the present disclosure is:
A heat storage material that is disodium hydrogen phosphate dodecahydrate,
Fatty acid salts.

  According to the first aspect, the action of the fatty acid salt suppresses overcooling of the heat storage material that is disodium hydrogenphosphate dodecahydrate without always maintaining a part of the heat storage composition at 35 ° C. or lower. it can.

  In the second aspect of the present disclosure, for example, the heat storage composition according to the first aspect has a solubility at the melting point when the heat storage composition is in a liquid phase at the melting point of the disodium hydrogen phosphate dodecahydrate. It contains the fatty acid salt at the above concentration. According to the second aspect, the supercooling of the heat storage material can be more reliably suppressed by the action of the fatty acid salt that is not dissolved in the heat storage composition that is in the liquid phase.

  In the third aspect of the present disclosure, for example, in the heat storage composition according to the first aspect or the second aspect, the fatty acid salt has 4 to 22 carbon atoms. According to the 3rd aspect, the overcooling of a thermal storage material can be suppressed more reliably.

  In the fourth aspect of the present disclosure, for example, in the heat storage composition according to any one of the first to third aspects, the fatty acid salt is stearate, butyrate, caproate, octanoate, At least one fatty acid salt selected from the group consisting of caprate, myristate, dodecanoate, palmitate, arachidate, and behenate. According to the 4th aspect, the overcooling of a thermal storage material can be suppressed more reliably.

  In the fifth aspect of the present disclosure, for example, in the heat storage composition according to any one of the first to fourth aspects, the cation in the fatty acid salt is a sodium ion. According to the fifth aspect, it is possible to more reliably suppress overcooling of the heat storage material.

The heat storage body according to the sixth aspect of the present disclosure is:
A heat storage composition according to any one of the first to fifth aspects;
And a package enclosing the heat storage composition.

  According to the sixth aspect, it is easy to handle a heat storage composition advantageous for reducing energy consumption for suppressing supercooling while containing disodium hydrogenphosphate dodecahydrate as a heat storage material. Become.

(Embodiment)
Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In addition, the following embodiment is only an illustration and the thermal storage composition and thermal storage body of this indication are not limited to the following embodiment.

  As shown in FIGS. 1 and 2, the heat storage body 1 includes a heat storage composition 2 and a package 4. The heat storage composition 2 contains a heat storage material that is disodium hydrogen phosphate dodecahydrate and a fatty acid salt. In the heat storage body 1, the heat storage composition 2 is enclosed in a package 4.

  The heat storage composition 2 typically contains a heat storage material as a main component. In the present specification, the “main component” means a component that is contained most on a mass basis.

  In this embodiment, when the heat storage composition 2 is in a liquid phase at the melting point (35 ° C.) of disodium hydrogen phosphate dodecahydrate, the heat storage composition 2 is a fatty acid salt having a concentration equal to or higher than the solubility at the melting point. Contains. The fact that the heat storage composition 2 contains a fatty acid salt having a concentration equal to or higher than the solubility at the melting point of disodium hydrogen phosphate dodecahydrate results in white turbidity in the liquid phase heat storage composition 2 at that melting point, for example. Can be confirmed.

  Fatty acid salts that cannot be dissolved in the liquid phase heat storage composition 2 are considered to form micelles. In the heat storage composition 2, this micelle is considered to function as a pseudo crystal nucleus for disodium hydrogen phosphate dodecahydrate. Thereby, even if it does not always maintain a part of heat storage composition 2 at 35 degrees C or less, it is thought that the supercooling of the heat storage material which is a disodium hydrogenphosphate dodecahydrate can be suppressed.

  The fatty acid salt contained in the heat storage composition 2 may have 4 to 22 carbon atoms. In this case, the fatty acid salt has a carbon chain of an appropriate length, and the overcooling of the heat storage material can be more reliably suppressed.

  The fatty acid salt contained in the heat storage composition 2 is, for example, stearate, butyrate, caproate, octanoate, caprate, myristate, dodecanoate, palmitate, arachidate, and At least one fatty acid salt selected from the group consisting of behenates.

  The cation in the fatty acid salt contained in the heat storage composition 2 may be sodium ion. In this case, since the fatty acid salt contains the same type of cation as the cation contained in the heat storage material, the compatibility between the heat storage material and the fatty acid salt is good. Thereby, the supercooling of the heat storage material can be suppressed more reliably.

  The heat storage composition 2 may contain components other than the heat storage material and the fatty acid salt as necessary. For example, the heat storage composition 2 may contain a viscosity modifier. The heat storage composition 2 may contain only a heat storage material and a fatty acid salt. Furthermore, the heat storage composition 2 may contain a phase separation inhibitor. Moreover, the heat storage composition 2 may contain water in an amount equal to or more than that which forms dodecahydrate of disodium hydrogen phosphate.

  The package 4 is not particularly limited as long as the heat storage composition 2 can be enclosed. As shown in FIG. 3, the package 4 has a seal portion 3. The inside of the package 4 is sealed by the seal portion 3. The package 4 is made of a film having a water vapor barrier property, for example. Thereby, the fluctuation | variation of content of the water contained in the thermal storage composition 2 can be suppressed. The package 4 is made of, for example, a laminate film in which layers of a resin such as polyethylene are laminated on both surfaces of an aluminum foil. For example, the seal portion 3 is formed by heat sealing the inner surfaces of the laminate film.

  The heat storage body 1 is not limited to a specific shape. From the viewpoint of efficiently heating or cooling the heat storage composition 2, the heat storage body 1 has, for example, a sheet shape or a rod shape.

  The thermal storage composition of this indication is demonstrated in detail using an Example. In addition, the thermal storage composition of this indication is not limited to an Example.

<Example 1-A to Example 1-X>
In a 9 cc glass sample bottle, 5.0 g of disodium hydrogen phosphate dodecahydrate is placed, and the contents of the sample bottle are heated in a hot water bath at 55 ° C. to disodium disodium hydrogen phosphate dodecahydrate. The material was melted to obtain a clear solution. The fatty acid salt shown in Table 1 was added to this solution in the amount shown in Table 1. Next, the liquid in the sample bottle was sufficiently stirred using a magnetic stirrer to obtain samples according to Example 1-A to Example 1-X. In addition, as shown in Table 1, in Example 1-A to Example 1-X, two samples that were the same in terms of the type of fatty acid salt and the amount of fatty acid salt added were prepared. In the samples according to Example 1-A to Example 1-H, at 35 ° C., the fatty acid salt that did not dissolve was micellized and suspended in the sample. In the samples according to Example 1-I to Example 1-X, at 35 ° C., the fatty acid salt that did not dissolve was micellized in the sample, and the entire sample was clouded. In Table 1, Ws / Wp means the ratio of the weight Ws of fatty acid salt to the weight Wp of disodium hydrogen phosphate dodecahydrate in each sample.

<Comparative Examples 1 and 2>
In a 9 cc glass sample bottle, 5.0 g of disodium hydrogen phosphate dodecahydrate is placed, and the contents of the sample bottle are heated in a hot water bath at 55 ° C. to disodium disodium hydrogen phosphate dodecahydrate. Thawed. This obtained the sample which concerns on the comparative examples 1 and 2 which is a transparent solution.

<Measurement of crystallization start temperature>
The crystallization start temperature was measured for the samples according to each Example or each Comparative Example contained in the sample bottle as follows. The sample bottle was allowed to stand on a temperature control plate equipped with a Peltier element. The temperature of the temperature control plate was adjusted to 15 ° C. Thereby, the sample bottle was cooled and the sample in the sample bottle was crystallized. After the release of the solidification heat generated during crystallization of the sample was completed, the temperature of the temperature control plate was adjusted to 25 ° C. Thereby, after the temperature of a sample bottle became constant at 25 degreeC, the sample bottle was put into the thermostat set to 50 degreeC, and the sample was melt | dissolved. Then, the sample bottle was taken out from the thermostat, and the sample bottle was allowed to stand for 10 minutes on a temperature control plate adjusted to a temperature of 40 ° C. Attach a thermocouple to the sample bottle, measure the temperature of the sample bottle, and confirm the temperature rise due to the generation of solidification heat at the start of crystallization of the sample. The onset temperature was determined. When the start of crystallization of the sample was not observed, the temperature of the temperature control plate was lowered by 1 ° C. and kept at that temperature for 10 minutes, and the determination of whether or not the crystallization of the sample was started was repeated. Thus, the set temperature of the temperature control plate when the crystallization of the sample finally started was recorded. In consideration of the variation in the crystallization start temperature of the samples, three measurements were performed for each sample. The crystallization start temperature of the sample thus measured was subtracted from 35 ° C., which is the melting point of disodium hydrogen phosphate dodecahydrate, to determine the limit supercooling degree ΔT in each measurement. The results are shown in Table 1.

  As shown in Table 1, the limit supercooling degree of the samples according to Example 1-A to Example 1-X was lower than the limit supercooling degree of the samples according to Comparative Examples 1 and 2. This is presumably because the fatty acid salt that did not dissolve in the liquid phase sample was micellized and functioned as a pseudo crystal nucleus of disodium hydrogen phosphate dodecahydrate.

<Sample 2-A to Sample 2-J>
5.0 g of disodium hydrogen phosphate dodecahydrate was placed in each of 10 sample bottles made of 9 cc glass. The contents of the sample bottle were heated in a hot water bath at 55 ° C. to melt the disodium hydrogen phosphate dodecahydrate to obtain a transparent solution. The amount of sodium stearate shown in Table 2 was added to the solution in the eight sample bottles. Next, the liquid in the sample bottle was sufficiently stirred using a magnetic stirrer with respect to the sample bottle to which sodium stearate was added. The liquid stirring using a magnetic stirrer was not performed on the two sample bottles to which sodium stearate was not added. Thus, Sample 2-A to Sample 2-J were obtained. In Sample 2-C to Sample 2-J, at 35 ° C., sodium stearate that did not dissolve was micellized in the solution, and the entire sample was cloudy. In Table 2, Ws / Wp means the ratio of the weight Ws of sodium stearate to the weight Wp of disodium hydrogen phosphate dodecahydrate in each sample.

  With respect to Sample 2-C to Sample 2-J, the crystallization start temperature was measured as described above. The results are shown in Table 2 and FIG. As shown in FIG. 3, when the amount of sodium stearate added was increased, the limit degree of supercooling decreased, and when Ws / Wp was 4% by weight, the limit degree of supercooling was saturated at 5 to 7K. For this reason, it was suggested that the addition amount of sodium stearate may be 2 to 4% by weight with respect to disodium hydrogen phosphate dodecahydrate.

  The heat storage composition and the heat storage body of the present disclosure can suppress overcooling of the heat storage material in a temperature range suitable for heat absorption or temperature control of a lithium ion battery and floor heating, and a battery cooling system for an electric vehicle (EV) and a house It can be used effectively in floor heating systems and the like.

DESCRIPTION OF SYMBOLS 1 Thermal storage body 2 Thermal storage composition 3 Seal part 4 Package

Claims (6)

A heat storage material that is disodium hydrogen phosphate dodecahydrate,
Fatty acid salt,
Thermal storage composition.   The heat storage according to claim 1, comprising the fatty acid salt having a concentration equal to or higher than the solubility at the melting point when the heat storage composition is in a liquid phase at the melting point of the disodium hydrogen phosphate dodecahydrate. Composition.   The heat storage composition according to claim 1 or 2, wherein the fatty acid salt has 4 to 22 carbon atoms.   The fatty acid salt is selected from the group consisting of stearate, butyrate, caproate, octanoate, caprate, myristate, dodecanoate, palmitate, arachidate, and behenate. The heat storage composition according to any one of claims 1 to 3, comprising at least one fatty acid salt.   The heat storage composition according to any one of claims 1 to 4, wherein a cation in the fatty acid salt is a sodium ion. The heat storage composition according to any one of claims 1 to 5,
A package enclosing the heat storage composition,
Thermal storage body.

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