JP7543887B2 - Latent heat storage device and method for producing supercooling prevention medium used therein - Google Patents

Description

The present invention relates to a latent heat storage device and a method for manufacturing a supercooling prevention medium used therein.

Conventionally, various heat storage devices have been proposed that temporarily store thermal energy emitted from a moving object such as a vehicle in a heat storage material and use it to promote warming up when starting the engine, improve fuel efficiency, purify exhaust gas, and improve heating performance.

For example, Patent Document 1 describes a heat storage device that includes a heat storage container containing a latent heat storage material that creates a supercooled state when allowed to cool after being heated and melted, a heat transfer means to the heat storage material, a seed crystal container containing a crystal nucleus forming material that breaks down the supercooled state, a communication means that connects the inside of the heat storage container and the seed crystal container, and a communication interruption means for the communication means. This heat storage device is characterized in that the crystal nucleus forming material is filled in the portion of the seed crystal container that is furthest from the communication means, and the remaining space is filled with a latent heat storage material.

The heat storage principle of supercooled latent heat storage materials as described in Patent Document 1 is that when the material is heated above its melting point in a solid phase, it transforms into a liquid phase. This liquid phase does not recrystallize even when cooled below the melting point, but continues to remain in a supercooled liquid state, and the heat absorbed during heating is stored as latent heat. When it is desired to utilize this absorbed heat, the material is brought into contact with a crystal nucleus-forming material that acts to break down the supercooled state, causing it to recrystallize, and the stored latent heat can be extracted in an extremely short time as dissipated heat accompanying the change in state from liquid to solid.

Japanese Unexamined Patent Publication No. 63-68418

Thus, seed crystals are necessary to nucleate the heat storage material in the supercooled liquid phase at any time and cause it to change into a solid phase. In order to stably hold the seed crystals, it is known to use a supercooling prevention agent that forces the heat storage material to change into a solid phase below the melting point.

However, in the heat storage device described in Patent Document 1, if a supercooling prevention agent is used in the seed crystal container, the heat storage container and the seed crystal container are connected during heat release, and when the heat storage material in the heat storage container flows toward the seed crystal container, if the supercooling prevention agent dissolves into the heat storage material, the supercooling prevention agent will get mixed into the heat storage container, making it impossible to store heat in the heat storage container.

In particular, if the temperature of not only the heat storage container but also the seed crystal container rises during heat transfer to the heat storage material, the dissolution of the supercooling prevention agent increases, so the seed crystal container that holds the supercooling prevention agent needs to be positioned away from the heat storage container, which poses the problem that the heat storage device cannot be made compact.

In view of the above problems, the present invention aims to provide a latent heat storage device that can prevent heat storage problems caused by the dissolution of a supercooling prevention agent into the latent heat storage material, and that can place the supercooling prevention agent near the heat transfer means, thereby making the latent heat storage device compact, as well as a method for manufacturing a supercooling prevention medium used therein.

In order to achieve the above object, the present invention, as one embodiment thereof, is a method for producing a supercooling prevention medium for use in a latent heat storage device, which comprises mixing an aqueous solution containing an alkaline earth metal cation with an aqueous solution containing an anion that reacts with the alkaline earth metal cation to produce a salt that is insoluble or poorly soluble in water, and producing a salt that is insoluble or poorly soluble in water as a supercooling prevention agent, and includes the steps of immersing a porous body in one of the aqueous solutions containing the cation and the aqueous solution containing the anion, and adding the other aqueous solution containing the cation and the aqueous solution containing the anion to the aqueous solution in which the porous body is immersed, thereby supporting the water-insoluble or poorly soluble salt on the porous body.

In another aspect, the present invention provides a latent heat storage device, which includes a seed crystal section that houses a supercooling prevention medium in which a water-insoluble or poorly soluble alkaline earth metal salt is supported on a porous body, a heat storage section that houses a latent heat storage material that is in intermittent communication with the seed crystal section, and a heat transfer section to the latent heat storage material.

Thus, according to the present invention, the reaction to produce a salt that is insoluble or poorly soluble in water occurs in a state in which the pores of the porous body are sufficiently impregnated with alkaline earth metal cations or anions that react with the cations to produce a salt that is insoluble or poorly soluble in water, so that the supercooling prevention agent, a salt that is insoluble or poorly soluble in water, can be reliably supported in the porous body. Then, by storing a supercooling prevention medium in which the supercooling prevention agent is supported in a porous body in the seed crystal section of the latent heat storage device, it is possible to prevent heat storage problems caused by the supercooling prevention agent dissolving into the latent heat storage material, and this supercooling prevention medium can be placed near the heat transfer section, thereby making it possible to make the latent heat storage device compact.

FIG. 1 is a flow diagram for explaining a method for producing a supercooling prevention medium according to an embodiment of the present invention. 1 is a cross-sectional view showing a schematic diagram of an embodiment of a latent heat storage device according to the present invention. FIG. 3 is a flow diagram for explaining heat storage and heat release in the latent heat storage device shown in FIG. 2 . FIG. 1 is a cross-sectional view that illustrates a problem that occurs during heat storage in a conventional latent heat storage device. FIG. 4 is a cross-sectional view illustrating a schematic diagram of another embodiment of a latent heat storage device according to the present invention.

Below, an embodiment of the latent heat storage device and the method for manufacturing the supercooling prevention medium used therein according to the present invention will be described with reference to the attached drawings.

As shown in FIG. 1, the method for producing the supercooling prevention medium of this embodiment mainly includes an immersion step (FIG. 1(a)) in which a porous body 2 is immersed in an aqueous solution 1 containing alkaline earth metal cations (also simply referred to as a "cation-containing aqueous solution"), and a support step (FIG. 1(c)) in which an aqueous solution 3 containing anions (also simply referred to as an "anion-containing aqueous solution") that reacts with the alkaline earth metal cations to produce a salt that is insoluble or poorly soluble in water is added to the cation-containing aqueous solution 1 in which the porous body 2 is immersed, and the water-insoluble or poorly soluble salt (supercooling prevention agent) is supported on the porous body. This allows the supercooling prevention medium 5 in which the supercooling prevention agent is supported on the porous body to be obtained (FIG. 1(d)). Each step will be described in more detail.

In the immersion step, as shown in FIG. 1(a), an aqueous solution 1 containing alkaline earth metal cations is placed in a container 10 such as a screw bottle. As the alkaline earth metal, strontium, barium, etc. are preferred from the viewpoint of providing an excellent supercooling prevention effect as a supercooling prevention agent or supercooling prevention medium and generating a salt that is insoluble or poorly soluble in water. In addition, as the aqueous solution, an aqueous solution of alkaline earth metal chloride, an aqueous solution of alkaline earth metal hydroxide, an aqueous solution of alkaline earth metal nitrate, etc. are preferred from the viewpoint of immersing the porous body and generating a salt that is insoluble or poorly soluble in water. The concentration of the cation-containing aqueous solution 1 is not particularly limited, but is preferably 0.1 to 1.5 mol/L, and more preferably 1 to 1.2 mol/L, for example.

The porous body 2 is not particularly limited as long as it has pores that carry the supercooling prevention agent, but may be, for example, activated carbon, an organic porous body such as a resin porous membrane, or an inorganic porous body such as porous ceramic, zeolite, or silica gel. Activated carbon is sometimes broadly classified by the type of raw material, but may be wood-based or coal-based, for example, coconut shell, coal, or petroleum pitch. The shape of the porous body 2 is not particularly limited, and may be, for example, granular, rectangular, plate-like, or pellet-like, or may be a surface coating of a member inside the heat storage device.

In addition, if the porous body 2 absorbs moisture or the like, this may hinder the support of the supercooling prevention agent, so a process of heating and vacuum degassing the porous body 2 may be performed before placing it in the container 10 to remove moisture or the like in advance. The heating temperature is not particularly limited, but is preferably, for example, 80 to 100°C. Heating and vacuum degassing can be performed, for example, using a vacuum dryer.

The porous body 2 is placed in a container 10, and the porous body 2 is immersed in the cation-containing aqueous solution 1. At this time, as shown in FIG. 1(b), a step of keeping the porous body 2 immersed in the cation-containing aqueous solution 1 may be performed so that the alkaline earth metal cations are sufficiently permeated into the pores of the porous body 2. In the keeping step, the opening of the container 10 is closed with a lid 11, and the container 10 is immersed in warm water in a thermostatic bath 12. The temperature of the keeping is preferably, for example, 60 to 70°C. The time of keeping is preferably, for example, 5 to 30 minutes. This can promote the impregnation of the alkaline earth metal cations into the porous body 2. In addition, in order to promote the impregnation, the entire container 10 with the lid 11 closed may be vibrated.

In the loading step, as shown in FIG. 1(c), an aqueous solution 3 containing anions that react with alkaline earth metal cations to produce salts that are insoluble or poorly soluble in water is placed in a container 10. Such anions vary depending on the type of aqueous solution 1 containing alkaline earth metal cations, but are preferably, for example, sulfate ions, carbonate ions, oxide ions, etc. The concentration of the anion-containing aqueous solution 3 may be the theoretical amount required to produce salts that are insoluble or poorly soluble in water, depending on the concentration of the cation-containing aqueous solution 1.

As a result, the cations of the alkaline earth metal in the cation-containing aqueous solution 1 react with the anions in the anion-containing aqueous solution 3 to produce a salt that is insoluble or poorly soluble in water. This salt that is insoluble or poorly soluble in water functions as a supercooling inhibitor. As an example of this reaction, the reaction formula when the cation-containing aqueous solution 1 is an aqueous strontium chloride solution and the anion-containing aqueous solution 3 is dilute sulfuric acid is shown below. In this reaction, strontium sulfate is produced as the supercooling inhibitor.
SrCl ₂ +H ₂ SO ₄ →SrSO ₄ + ₂ HCl

In addition, the cations that have penetrated the pores of the porous body 2 react to generate a supercooling prevention agent, which is then supported by the porous body 2. As a result, as shown in FIG. 1(d), a supercooling prevention medium 5 can be obtained in which the supercooling prevention agent is supported by the porous body.

In addition to the above-mentioned strontium sulfate, examples of the supercooling prevention agent include strontium carbonate, barium sulfate, barium carbonate, etc. Furthermore, since this supercooling prevention agent is a salt that is insoluble or poorly soluble in water, it is possible to prevent the supercooling prevention agent from leaking out of the porous body.

In this specification, "water-insoluble" refers to a substance having a solubility of 0.01 g or less in 100 g of water at room temperature (25°C). "Poorly soluble in water" refers to a substance having a solubility of 0.1 g or less and more than 0.01 g in 100 g of water at room temperature (25°C). Strontium sulfate has a solubility of 0.014 g/100 ml of water, making it poorly soluble in water. Strontium carbonate has a solubility of 0.0011 g/100 ml of water, making it insoluble in water. Barium sulfate has a solubility of 2.5 x 10 ^-4 g/100 ml of water, making it insoluble in water.

In the embodiment shown in FIG. 1, the cation-containing aqueous solution 1 and the porous body 2 are placed in the container 10 and immersed in the immersion step, but the present invention is not limited to this. Instead of the cation-containing aqueous solution 1, the anion-containing aqueous solution 3 may be placed in the container 10 and the porous body 2 may be immersed in the anion-containing aqueous solution 3. In this case, in the carrying step, the cation-containing aqueous solution 1 is placed in the container 10 instead of the anion-containing aqueous solution 3, so that the porous body can carry a salt that is insoluble or poorly soluble in water. However, when a highly concentrated dilute sulfuric acid or the like is used as the anion-containing aqueous solution, the aqueous solution may generate heat when the cation-containing aqueous solution is added in the carrying step, and the dilute sulfuric acid or the like may splash, so care must be taken when handling it. In addition, when a highly concentrated dilute sulfuric acid or the like is used, care must be taken when warming or vibrating the porous body to promote the impregnation of anions such as sulfate ions into the porous body. Furthermore, depending on the type of porous body, immersion in dilute sulfuric acid or the like may cause corrosion.

Next, we will explain one embodiment of the latent heat storage device according to the present invention.

As shown in FIG. 2, the latent heat storage device 20 of this embodiment mainly comprises a seed crystal container 22 containing a supercooling prevention medium 25 in which a water-insoluble or poorly soluble alkaline earth metal salt is supported on a porous body, and a heat storage container 21 containing a latent heat storage material 26 that is in intermittent communication with the seed crystal container. The seed crystal container 22 also contains a latent heat storage material 26.

The latent heat storage material 26 is not particularly limited as long as it is a substance that changes from a solid phase to a liquid phase when heated above its melting point, and then maintains the liquid phase in a supercooled state even when cooled below its melting point, and can store the heat absorbed during heating as latent heat. For example, calcium chloride hydrate, sodium acetate hydrate, sodium sulfate hydrate, etc. are preferred.

The heat storage container 21 and the seed crystal container 22 may be capable of withstanding the heating and cooling required to change the state of the latent heat storage material 26 between the solid and liquid phases, and may use the same material and structure as the container for accommodating the latent heat storage material in a conventional latent heat storage device. For example, the material may be stainless steel, aluminum alloy, brass, etc., which have good thermal conductivity, and the structure may be a rectangular parallelepiped or any other three-dimensional shape. In addition, a heat transfer part (not shown), such as a fin for increasing the heat transfer area, is attached to the outer periphery of the latent heat storage device 20 as a heat transfer means to the latent heat storage material 26. As the fin, a fin-shaped fin, a corrugated fin, etc. may be used.

Between the heat storage container 21 and the seed crystal container 22, an on-off valve 23 such as a solenoid valve is provided, which allows the liquid phase latent heat storage material 26 to be intermittently connected between the heat storage container 21 and the seed crystal container 22. The on-off valve 23 is opened and closed by a control circuit (not shown) of the latent heat storage device 20.

The seed crystal container 22 is provided with a filter section 24 that divides the container into two compartments. One of the two compartments is not in contact with the flow path of the on-off valve 23, and the supercooling prevention medium 25 obtained by the above-mentioned manufacturing method is placed in this compartment that is not in contact with the flow path of the on-off valve 23. The filter section 24 is not particularly limited as long as it allows the latent heat storage material 26 to pass freely but does not allow the supercooling prevention medium 25 to pass through, and for example, a sponge, a metal mesh, a nonwoven fabric, etc. can be used. The filter section 24 can prevent the supercooling prevention medium 25 from moving to the other compartment in the seed crystal container 22 that is in contact with the flow path of the on-off valve 23, and therefore the supercooling prevention medium 25 can be stored in the seed crystal container 22.

The heat storage and heat release of the latent heat storage device 20 having such a configuration will be described with reference to FIG. 3. First, in the latent heat storage device 20 in a state where heat storage is completed and heat release is not yet performed, as shown in FIG. 3(a), the opening and closing valve 23 is closed and liquid phase latent heat storage material 26L is contained in the heat storage container 21. Since a supercooling prevention medium 25 is placed in the seed crystal container 22, the inside of the seed crystal container 22 contains solid phase latent heat storage material 26S, i.e., seed crystals.

Next, when dissipating heat from the latent heat storage device 20, as shown in FIG. 3(b), when the opening/closing valve 23 of the latent heat storage device 20 is opened, the liquid-phase latent heat storage material 26L in the heat storage container 21 flows into the seed crystal container 22 and comes into contact with the solid-phase latent heat storage material 26S that serves as a seed crystal in the seed crystal container 22. As a result, the liquid-phase latent heat storage material 26L nucleates and becomes solid, causing heat dissipation.

When the heat dissipation is complete, as shown in FIG. 3(c), the heat storage container 21 contains solid-phase latent heat storage material 26S. In this state, heat storage in the latent heat storage device 20 begins. Because both the heat storage container 21 and the seed crystal container 22 contain solid-phase latent heat storage material 26S, the opening and closing valve 23 cannot be closed.

When heat storage is completed, as shown in FIG. 3(d), the latent heat storage material 26 in the heat storage container 21 and the seed crystal container 22 is heated to above its melting point, and both become liquid phase latent heat storage material 26L. When this state is reached, the opening/closing valve 23 is closed.

After that, when the latent heat storage device 20 is cooled below its melting point, the latent heat storage material 26 in the seed crystal container 22 changes to a solid phase because the supercooling prevention medium 25 is placed therein. Therefore, as shown in FIG. 3(a), it is again in a state of preparation for heat release. In this way, the latent heat storage device 20 of this embodiment can repeatedly release and store heat.

On the other hand, in the latent heat storage device 40 shown in FIG. 4, in which the supercooling prevention agent is not supported on the porous body and the supercooling prevention agent is mixed into the latent heat storage material, when heat storage is completed, seed crystals 47 consisting of latent heat storage material and supercooling prevention agent remain in the liquid phase latent heat storage material 46L in the seed crystal container 42, and there is a risk that this seed crystal 47 will flow through the flow path of the opening and closing valve 43 to the liquid phase latent heat storage material 46L in the heat storage container 41. If the supercooling prevention agent is mixed into the heat storage container 41, the liquid phase latent heat storage material 46L in the heat storage container 41 will not be in a supercooled state, and a problem will occur in which heat storage will not be possible.

In the latent heat storage device 20 of this embodiment, the supercooling prevention agent is present in the seed crystal container 22 as the supercooling prevention medium 25 supported on the porous body, and since it is a salt that is insoluble or poorly soluble in water, it does not flow out of the porous body into the latent heat storage material, and therefore the supercooling prevention agent can be prevented from being mixed into the heat storage container 21. In addition, since the supercooling prevention medium 25 has a solid form like a porous body, it can be easily prevented from moving into the heat storage container 21 by the filter part 24 or the like.

In the embodiment shown in Figures 2 and 3, the heat storage container 21 and the seed crystal container 22 are containers of the same volume, but the present invention is not limited to this. For example, the seed crystal container 22 may have a smaller volume than the heat storage container 21. In addition, in the embodiment shown in Figures 2 and 3, the supercooling prevention medium 25 is shown as a granular material, but the present invention is not limited to this. For example, as shown in Figure 5, the supercooling prevention medium 50 may be a surface coating that covers the inner surface of the seed crystal container 22 of the latent heat storage device 20A. In this case, the inner surface of the seed crystal container 22 is covered with a porous body, and the porous body is made to carry a supercooling prevention agent, thereby obtaining the supercooling prevention medium 50 as a surface coating layer.

In the embodiment shown in Figures 2 and 3, a latent heat storage device 20 is shown that has two containers, a seed crystal container 22 that contains a supercooling prevention medium and a heat storage container 21 that contains a latent heat storage material 26. However, the present invention is not limited to this, and one container may have a seed crystal section that contains a supercooling prevention medium and a heat storage section that contains a latent heat storage material that is in intermittent communication with the seed crystal section.

The following describes examples of the present invention and comparative examples.

[Preparation of supercooling prevention medium: Supporting supercooling prevention agent on porous body]
First, since moisture and the like adsorbed on the coconut shell activated carbon used as the porous body may hinder the loading, the coconut shell activated carbon was heated and vacuum degassed at 100°C using a vacuum dryer (manufactured by ETTAS) to remove moisture and the like. Next, an aqueous solution of strontium chloride (SrCl ₂ ) was placed in a screw bottle, and coconut shell activated carbon (approximately 1 cm square) that had been previously heated and vacuum degassed was placed in it, and the coconut shell activated carbon was immersed in the aqueous solution of strontium chloride and held there. At this time, the temperature was kept at approximately 65°C so that the supercooling inhibitor would sufficiently penetrate into the pores of the coconut shell activated carbon.

Then, 10 wt % dilute sulfuric acid was added to the aqueous strontium chloride solution in which the coconut shell activated carbon was immersed, thereby generating strontium sulfate (SrSO ₄ ) supported on the coconut shell activated carbon. The coconut shell activated carbon supported by strontium sulfate (i.e., supercooling prevention medium) was then removed from the screw bottle.

Strontium carbonate (SrCO ₃ ) was supported on coconut shell activated carbon in the same manner, except that carbon dioxide was added to the aqueous solution of strontium hydroxide.

In addition, sodium _acetate trihydrate ( _{C2H3NaO2.3H2O} ), _sodium chloride ( _NaCl ), and strontium chloride hexahydrate ( _SrCl2.6H2O ) were supported on coconut shell activated carbon by the following procedure. First, coconut shell activated carbon _was immersed in and held in each aqueous solution of sodium acetate trihydrate, sodium chloride, and strontium chloride hexahydrate. The temperature was also kept at about 65°C during this process. The coconut shell activated carbon was then removed from each aqueous solution and placed in a vacuum dryer to dry it.

[Evaluation test of supercooling prevention effect (nucleation test)]
The above five types of substances, which are candidates for the supercooling prevention agent, were subjected to an evaluation test of the supercooling prevention effect. Coconut shell activated carbon (approximately 0.03 g) carrying each of these substances and calcium chloride hexahydrate (CaCl _{2.6H 2} O) (approximately 20 g) as a latent heat storage material were placed in a screw bottle and heated to 30°C or higher, which is the melting point of calcium chloride hexahydrate. After that, the screw bottle was placed on a cooling plate set to 2-5°C using a chiller, and it was investigated whether nucleation occurred. The cooling plate was immersed in water to promote heat transfer between the cooling plate and the screw bottle, and the bottom of the installed screw bottle was immersed in water to efficiently cool it. This heating and cooling operation was repeated five times (n=5), and the number of nucleation times was examined. The results are shown in Table 1. In addition, the state of nucleation of the latent heat storage material and the change in shape of the coconut shell activated carbon were also observed through the test.

[Supercooling prevention agent leakage confirmation test (leakage test)]
A test was conducted to confirm whether the candidate substance for the supercooling prevention agent had flowed out from the coconut shell activated carbon by repeatedly heating and cooling the latent heat storage material. After the above-mentioned evaluation test of the supercooling prevention effect was completed, only the supernatant liquid was separated from the screw bottle, and this supernatant liquid was repeatedly heated and cooled (n=5) to check whether nucleation occurred. If nucleation occurred five times, it was assumed that the candidate substance for the supercooling prevention agent had flowed out from the coconut shell activated carbon, and it was evaluated as "X". If nucleation occurred one to four times, it was assumed that some of the substance had flowed out, and it was evaluated as "△". If nucleation did not occur even once, it was assumed that no leakage had occurred, and it was evaluated as "○". The evaluation results are shown in Table 1.

As shown in Table 1, although sodium acetate trihydrate was found to have a supercooling prevention effect, it was found to have flowed out from the coconut shell activated carbon, and therefore it could not be used as a supercooling prevention medium of the present invention, and was given an overall rating of "x". Furthermore, although sodium chloride was found to have a supercooling prevention effect, it was found to have flowed out in part from the coconut shell activated carbon, and therefore it was unsuitable as a supercooling prevention medium of the present invention, and was given an overall rating of "x". Although strontium chloride hexahydrate nucleated quickly and had an excellent supercooling prevention effect, it was found to have flowed out in part from the coconut shell activated carbon, and therefore it could not be used as a supercooling prevention medium of the present invention, and was given an overall rating of "x".

On the other hand, although no leakage was observed from the coconut shell activated carbon, strontium carbonate took several minutes to several hours to nucleate, and was therefore given an overall rating of "○". Strontium sulfate nucleated quickly, was found to have an excellent effect in preventing supercooling, and was not observed to leak from the coconut shell activated carbon, so it was given an overall rating of "◎".

The results of the outflow test showed that the sodium acetate trihydrate, sodium chloride, and strontium chloride hexahydrate supported on the porous body, which were evaluated as "x" or "△", were all water-soluble substances. On the other hand, strontium carbonate and strontium sulfate, which were evaluated as "○" in the outflow test, are insoluble or poorly soluble in water. Therefore, it is presumed that salts that are insoluble or poorly soluble in water will not flow out of the porous body into the latent heat storage material even when repeatedly heated and cooled.

In addition, barium sulfate and barium carbonate, which are among the five types of substances mentioned above, share the same orthorhombic crystal structure as strontium sulfate and strontium carbonate, and their unit lattices are also very similar, so they are presumed to be evaluated as equivalent to strontium sulfate and strontium carbonate in nucleation tests. Also, barium sulfate and barium carbonate are insoluble in water. Therefore, it is presumed that barium sulfate and barium carbonate will also provide the same effect as strontium sulfate and strontium carbonate as a supercooling prevention medium of the present invention.

REFERENCE SIGNS LIST 1 Aqueous solution containing alkaline earth metal cations 2 Porous body 3 Aqueous solution containing anions that form salts that are insoluble or poorly soluble in water 10 Screw bottle 11 Lid 12 Thermostatic bath 20 Latent heat storage device 21 Heat storage container 22 Seed crystal container 23 Opening/closing valve 24 Filter section 25 Supercooling prevention medium 26 Latent heat storage material 47 Seed crystal 50 Supercooling prevention medium

Claims (6)

A method for producing a supercooling prevention medium for use in a latent heat storage device, comprising mixing an aqueous solution containing an alkaline earth metal cation with an aqueous solution containing an anion that reacts with the alkaline earth metal cation to produce a salt that is insoluble or poorly soluble in water, and producing the salt that is insoluble or poorly soluble in water as a supercooling prevention agent, comprising:
immersing a porous body in one of the aqueous solution containing the cations and the aqueous solution containing the anions;
adding the other of the aqueous solution containing the cations and the aqueous solution containing the anions to an aqueous solution in which the porous body is immersed, thereby causing the porous body to support a salt that is insoluble or poorly soluble in water. The method for producing a supercooling prevention medium for use in a latent heat storage device according to claim 1 further comprises a step of subjecting the porous body to a heating and vacuum degassing treatment in advance. A method for producing a supercooling prevention medium for use in a latent heat storage device according to claim 1 or 2, wherein the cation is a strontium ion and the anion is a sulfate ion. a seed crystal portion containing a supercooling prevention medium in which a water-insoluble or poorly soluble alkaline earth metal salt is supported on a porous body;
A heat storage section containing a latent heat storage material that is in intermittent communication with the seed crystal section;
a heat transfer section to the latent heat storage material, wherein the seed crystal section and the heat storage section are provided in a single container . a seed crystal portion containing a supercooling prevention medium in which a water-insoluble or poorly soluble alkaline earth metal salt is supported on a porous body;
A heat storage section containing a latent heat storage material that is in intermittent communication with the seed crystal section;
A heat transfer portion to the latent heat storage material;
wherein the supercooling prevention medium is a surface coating layer on an inner surface of the seed crystal portion. 6. The latent heat storage device according to claim 4, wherein the water-insoluble or poorly soluble alkaline earth metal salt is strontium sulfate, and the latent heat storage material is calcium chloride hydrate.