JPS581715B2 - Heat storage agent composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat storage agent composition mainly containing sodium sulfate decahydrate (Na2SO4.10H20).

Generally, methods for storing heat include methods that utilize the sensible heat of substances and methods that utilize latent heat.

A typical example of a method that uses sensible heat is water.

Water has a large specific heat, is easy to handle, and above all, is extremely cheap.

In addition to water, gravel, crushed stone, and bricks are used.

However, if an attempt is made to store heat using sensible heat, the capacity and weight of the heat storage device will become considerably large.

Another drawback is that the temperature of the heat storage agent itself decreases in proportion to the release of heat.

On the other hand, examples of methods that utilize latent heat include methods that use inorganic aqueous salts and organic crystalline substances.

In principle, this method utilizes phase change phenomena such as melting that occur at a constant temperature, and the temperature drop of the heat storage agent due to heat release is small, and the latent heat of phase change such as melting is generally large, making it compact. can store heat.

The present invention relates to a technology for storing heat by utilizing the latent heat of fusion of this inorganic hydrated salt, and in particular to a technology for using sodium sulfate 1O hydrate and modifying it so that it is suitable for use as a heat storage agent.

The elemental sodium sulfate decahydrate is known as an inexpensive heat storage material, but it tends to have the disadvantage of being corrosive and exhibiting a noticeable supercooling phenomenon.

When the temperature of sodium sulfate 1O water salt is gradually lowered from the molten state, it does not assimilate (
The supercooling phenomenon of no crystallization and no heat dissipation causes practical inconveniences in that even if heat is stored in sodium sulfate decahydrate, the heat cannot be extracted at a predetermined temperature.

Therefore, in order to use sodium sulfate decahydrate as a heat storage agent, it is important to suppress this supercooling phenomenon.

An object of the present invention is to prevent the above-mentioned supercooling phenomenon of sodium sulfate decahydrate, to provide a heat storage agent composition that is inexpensive, has stable heat absorption and radiation performance, and has a high heat storage density.

In order to suppress the supercooling phenomenon of sodium sulfate decahydrate, the present inventors have conducted intensive research on nucleating agents that promote the generation of crystal nuclei during the exothermic crystallization process of sodium sulfate decahydrate. They discovered a nucleating agent effective for sodium sulfate decahydrate and completed the present invention.

That is, the gist of the present invention resides in a heat storage agent composition in which lithium tetraborate or ammonium tetraborate tetrahydrate is added to sodium sulfate decahydrate.

In the present invention, lithium tetraborate or ammonium tetraborate tetrahydrate comes into contact with sodium sulfate decahydrate to effectively act as a nucleating agent.

The amount of lithium tetraborate used in the present invention is preferably in the range of 0.1 to 15 parts by weight, more preferably 1 to 7 parts by weight, per 100 parts by weight of sodium sulfate decahydrate. Ranges are used effectively.

Further, the amount of ammonium tetraborate tetrahydrate used in the present invention is preferably in the range of 0.1 parts by weight to 30 parts by weight, more preferably 2 parts by weight, based on 100 parts by weight of sodium sulfate decahydrate. ~20 parts by weight are effectively used.

Note that lithium tetraborate and ammonium tetraborate tetrahydrate may be used in combination, or in combination with other nucleating agents.

As described above, the present invention provides a heat storage agent that does not accelerate supercooling by adding lithium tetraborate or ammonium tetraborate tetrahydrate to sodium sulfate decahydrate. Depending on the temperature at which it is exposed, in order to prevent precipitation and aggregation of lithium tetraborate or ammonium tetraborate tetrahydrate during heating and melting, a thickener such as carboxymethyl cellulose or fine silica powder may be added. Additives such as a solidification heat dissipation temperature regulator may be added as appropriate.

Therefore, when the heat storage agent composition of the present invention is heated normally,
First, heat is accumulated as sensible heat in the solid phase state, and then when the solid phase changes from the liquid phase, a large amount of heat is accumulated as the latent heat of melting, and when the phase completely changes to the liquid phase, heat is further accumulated as sensible heat. It accumulates.

When releasing heat, sensible heat is normally released from the high-temperature liquid phase state to the solidification temperature, and at the solidification temperature, the heat that was previously accumulated as latent heat of melting at that temperature is released without causing supercooling phenomenon. is released as latent heat of solidification (crystallization) over a long period of time, and when it completely changes to a solid phase, it releases heat as sensible heat while further lowering the temperature of the heat storage agent itself.

As mentioned above, the heat storage agent composition of the present invention is made by adding lithium tetraborate or ammonium tetraborate tetrahydrate to sodium sulfate decahydrate, so it is inexpensive and stable without causing supercooling. It has heat absorption and radiation performance and high heat storage density.

The heat storage agent composition of the present invention has a melting point slightly higher than room temperature (approximately 2
(6°C to 29°C), it can be used in residential equipment such as floor heating and wall heating, and for various other heat storage applications by combining it with solar energy or other heat sources.

The present invention will be explained in detail below using examples.

Example 1 3 parts by weight of finely powdered silica (Aerosil #380, manufactured by Nippon Aerosil ■) was added to 100 parts by weight of sodium sulfate decahydrate, and the mixture was stirred and mixed to prepare an original sample.

Add 0.9 g of lithium tetraborate to 30 g of this original sample and stir and mix.
A thermocouple (IC) was inserted into the center of the test tube, and the upper end was sealed with a rubber stopper.

Then, this test tube was immersed in a constant temperature water bath at 50°C and sufficiently heated until the inside was melted and the temperature reached 50°C.

Next, this test tube was immersed in a constant temperature water bath at 17° C. to cool it by heat radiation, and the temperature change of the heat storage agent composition in the test tube was measured.

The heat radiation cooling curve of this heat storage agent composition is as shown in 1 in Figure 1, and this heat storage agent composition does not cause supercooling.
It was confirmed that solidification heat was dissipated for a long time at about 28°C.

Example 2 2.5 g of ammonium tetraborate tetrahydrate was added to 30 g of the original sample prepared in Example 1, and a heat storage agent composition prepared by stirring and mixing was prepared in the same manner as in Example 1, and the temperature change of the heat dissipation cooling was measured. was measured.

The heat radiation cooling curve of this heat storage agent composition is as shown in 2 in Figure 1, and the heat storage agent composition does not cause supercooling.
It was confirmed that solidification heat was dissipated for a long time at about 26°C.

Comparative Example The radiation cooling behavior of 30 g of the original sample prepared in Example 1 to which no nucleating agent was added was measured in the same manner as in Example 1.

The heat radiation cooling curve of this original sample was as shown in 3 in FIG. 1, and it was confirmed that this original sample was supercooled and was cooled to ambient temperature without solidifying and radiating almost no heat.

Example 3 0.0 g of lithium tetraborate was added to 30 g of sodium sulfate decahydrate.
A heat storage agent composition in which 9 g of the heat storage agent was added and mixed with stirring was treated in the same manner as in Example 1, and the temperature change of the heat dissipation cooling was measured.

The heat dissipation cooling curve of this heat storage agent composition was as shown in 4 in FIG. 2, and it was confirmed that solidification heat dissipation was performed at about 29° C. for a long time without supercooling.

Example 4 A heat storage agent composition prepared by adding 2.51 parts of ammonium tetraborate to 301 parts of sodium sulfate decahydrate and stirring the mixture was prepared in the same manner as in Example 1, and the temperature change of the heat radiation cooling was measured.

The heat radiation cooling curve of this heat storage agent composition is as shown in 5 in FIG. 2, and this heat storage agent composition does not cause supercooling.
It was confirmed that solidification heat was dissipated for a long time at about 26°C.

Comparative Example 2 Sodium sulfate decahydrate 3 without added nucleating agent
The radiation cooling behavior at 0 g was measured in the same manner as in Example 1.

The radiation cooling curve of this sample is as shown in 6 in Figure 2,
It was confirmed that this sample caused supercooling and was cooled down to ambient temperature with almost no solidification heat dissipation.

[Brief explanation of drawings]

FIGS. 1 and 2 are graphs showing the radiation cooling behavior of the heat storage agent composition of the present invention and a conventional heat storage agent composition to which no nucleating agent is added.

Claims (1)

[Scope of Claims] 1. A heat storage agent composition in which lithium tetraborate or ammonium tetraborate tetrahydrate is added to sodium borate decahydrate. 2. The heat storage agent composition according to claim 1, wherein lithium tetraborate is added in an amount of 0.1 to 15 parts by weight to 100 parts by weight of sodium sulfate decahydrate. 3. The heat storage agent composition according to claim 1, wherein ammonium tetraborate tetrahydrate is added in an amount of 0.1 parts by weight to 30 parts by weight to 100 parts by weight of sodium sulfate decahydrate. .