JPS58219399A - Heat accumulating material - Google Patents

Abstract

PURPOSE:To substantially prevent a phase separation of the titled material to each other, and to make it repeatedly usable without trouble, by mixing calcium silicate having specific properties with a latent heat accumulating material consisting of an inorganic compound which tends to be separated from each other. CONSTITUTION:A calcium silicate of sonolite and/or tobermorite is mixed with a latent heat accumulating material which tends to separate from each other. It is favorable that the mean diameter of granular calcium silicate is to be 20- 100mum, its apparent volumetric specific gravity is to be 0.07-0.15, and its mixing ratio is to be 0.8-1.2 times in the volumetric ratio. With such an arrangement, sediments will not at all be formed apparently, when the heat accumulating material is dissolved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat storage material, particularly a material that can efficiently store solar energy, efficiently discharge it as a heat source, and efficiently store energy again.

Regarding solar energy, various proposals have been made in various fields to actively utilize solar energy, reflecting the recent energy situation.

Solar heat is a heat source whose supply is unstable, and it is necessary to store heat in order to obtain the desired amount of energy at any time as needed.

Conventionally, heat storage materials for solar heat utilization have mainly been those that utilize the sensible heat of water, rocks, etc.

Although such materials are inexpensive and easy to handle, they have the drawback of having a small heat storage capacity.

Furthermore, other heat storage materials include paraffins, CaCl
Latent heat type heat storage materials such as eutectic salts such as 2-6T (20, Na2SO4.10H2O% hydrated salts, KC!1-KNOa, etc.) have also been proposed.

These heat storage systems utilize the flow of heat in and out due to the phase change of substances, and generally have a large heat storage capacity per volume.
In addition, considerable advantages such as the ability to store heat at a constant temperature are lost, but the so-called supercooling phenomenon in which crystallization does not occur unless the temperature is significantly lower than the melting point during cooling, and the phenomenon of anhydrous or low water content during melting. A so-called phase separation occurs in which a small amount of salt is separated from water or a solution with a low concentration, which has the disadvantage that it cannot be used repeatedly.

Among these drawbacks, for example, Na
Various means are known for suppressing and preventing this by adding several quantities of a nucleating agent such as borax to zSO4.10H20.

On the other hand, methods for suppressing and preventing phase separation include, for example, placing latent heat storage materials in small capsules to prevent significant phase separation, stirring in a tank to prevent separation, and inorganic materials such as clay. Add a kelizing agent to increase the viscosity and tighten it.
Measures to prevent solid sedimentation have been proposed.

However, among these methods, the method of putting it into small capsules has a limit on the size of the container and requires a large amount of containers.
It is also difficult to completely prevent phase separation, and methods using stirring are expensive for power and go against the original purpose of using solar energy to save energy. Also, the method of using a gelling agent in a kettle is a relatively preferable method among these methods, and the use of clay or finely powdered silica has been proposed, but these themselves have a specific gravity of The conventional methods each have drawbacks, such as sedimentation occurring over a long period of time and loss of phase separation prevention effect if left undisturbed.

In view of the above, the inventors of the present invention have conducted extensive research and investigation with the aim of finding a means to substantially prevent the phase separation phenomenon of latent heat storage materials. It has been found that the above object can be achieved.

Thus, the present invention provides a heat storage material comprising a latent heat type heat storage material made of an inorganic compound that undergoes phase separation and mixed with xonotlite and/or l-bamonite silica saturated calcium.

Examples of the latent heat storage material used in the present invention include sodium sulfate decahydrate, sodium thiosulfate pentahydrate, calcium chloride hexahydrate, sodium carbonate decahydrate, and phosphoric acid sorta 1
Dihydrate, calcium nitrate tetrahydrate, calcium carbonate decahydrate, sodium borate decahydrate, aluminum nitrate nonahydrate, barium hydroxide octahydrate, strontium hydroxide octahydrate, magnesium nitrate hexahydrate, ammonium light Ban] dihydrate salt,
Zinc chloride trihydrate, potassium phosphate hexahydrate, caustic soda 3.
Single inorganic compound hydrate salts such as pentahydrate, aluminum sulfate dodecahydrate, cao'l ・MgCl212H20, Mg
(N03) 26H20・A, 1 (NO3), 9H2
0,CaCl2・Ca(NOg)210H20,0a(
NOs)24H20・Zn (NO3)26H20, O
a (NOg)24H20-Mg (NO3), 6H
20.

084NO3), 4H20-A, 1. (No.3),
9H20, Mg(NOa), 6H20-Zn (
Examples include hydrated salts of inorganic composite compounds such as NOs)26H20, and these can be used appropriately depending on the thermal energy 411'' and temperature to be obtained.

Next, the calcium silicate used in the present invention needs to be xonotrite thread or tobermorite thread. When viewed microscopically, these calcium silicates are hollow bodies or solid bodies with an outer shell of calcium silicate, and they look just like a ball. covered with calcium. It is difficult to completely empty the hollow part, and it usually contains a small amount of water, which is the medium used for synthesis, and this amount of water is such that some water can enter and exit through the outer shell. have. Since xonotrite type calcium silicate is more hollow and has a limp shape, it is particularly preferable as the calcium silicate used in the present invention.

The inorganic compound that causes phase separation used as the latent heat type heat storage material in the present invention is a hydrated salt, and when heat is transferred in and out,
Once such a salt melts, it forms a lower hydrated salt and separates into an aqueous phase and a precipitate. When this phenomenon occurs, heat storage capacity etc. are significantly reduced, and most There may also be cases where it cannot be used as a heat storage material.

In the present invention, when the above-mentioned xonotrite-based or tobermorite-based calcium silicate (hereinafter referred to as calcium silicate) is mixed into such a hydrated salt, even if the hydrated salt is melted, the precipitate does not appear at all. Not generated.

The reason for this is not necessarily clear, but sediments are trapped between the many cilia of the calcium silicate outer shell, and the formation of low-level hydrated salts itself is suppressed by some action, resulting in a phase separation phenomenon. This seems unacceptable.

Calcium silicate used in the present invention can be obtained by various known methods that have already been proposed. The calcium silicate used preferably has an average particle size of about 20 to 100 microns. If the average particle size is less than the above range, the phase separation phenomenon of the hydrated salt cannot be suppressed sufficiently effectively, whereas if it exceeds the above range, sedimentation may occur or the heat storage efficiency of the hydrated salt may be reduced. This is not a good idea as it may cause a decrease in

Also, the apparent bulk specific gravity is also 0 for almost the same reason as above.
．． It is appropriate to adopt approximately 07 to 015.

Further, the amount of calcium silicate to be used is approximately 0.8 to 1.2 times, preferably approximately 1.0 times, the total volume of the molten hydrated salt.

If the amount used is less than the above range, phase separation due to increase in water content cannot be effectively suppressed, whereas if it exceeds the above range, the viscosity of the entire liquid will increase and it will not flow even when the hydrated salt is melted. This is not preferable because there is a risk that the thermal performance will decrease, the thermal efficiency will decrease, and handling will become inconvenient.

Next, the present invention will be explained by examples.

Example】.

Sodium sulfate 0 hydrate crystal I K9 was placed in a stirring tank, and the nuclide was immersed in warm water at 50°C to completely melt the crystal.

Next, xonotrite calcium silicate powder 0.1 K9 having an average particle size of 5 μm and a bulk specific gravity of O was introduced as a nuclide.1.
/ , a slurry-like material was obtained by thorough stirring.

Next, in order to facilitate observation of this slurry, the container was sealed in a transparent plastic container, and the container was immersed in a container containing 10°C water to perform heat exchange. The temperature rose to 20°C, and the slurry sealed in the transparent container appeared as a lumpy solid, and no free water or fine powder was observed, indicating that no phase separation phenomenon occurred. .

Next, the plastic container containing this lumpy solid was exposed to sunlight to make the solid into a slurry, and then immersed in cold water in the same manner as above, and the temperature of the cold water rose almost in the same way as above. , the slurry in the transparent container appeared as one lumpy solid as before.

Example 2 Sodium thiosulfate pentahydrate crystals IK9 were placed in a stirring tank, and the nuclide was immersed in hot water at 70°C to completely melt the crystals.

Next, 01 kg of xonotrite-based calcium silicate powder having an average particle size of 50 μm and a bulk specific gravity of 01 was introduced into the nuclide and sufficiently stirred to obtain a slurry.

Next, pour this slurry into a transparent plastic container.
-1 When the container was immersed in a container containing 5 tons of water at 10°C for heat exchange, the water temperature in the container rose to 20°C.
The slurry-like material sealed in the transparent container exhibited a single lumpy solid, and the presence of free water, fine powder, etc. was not observed, and it was confirmed that no phase separation phenomenon occurred.

Example 3 Barium hydroxide octahydrate crystal I K7 was placed in a stirring tank, and the nuclide was immersed in hot water at 90°C to completely melt the crystal.

Next, 01 kg of xonotrite calcium silicate powder having an average particle size of 50 μm and a bulk specific gravity of O1 was introduced into the nuclide and thoroughly stirred to obtain a slurry.

Next, this slurry-like material was inserted into a transparent plastic container, and the container was immersed in a container containing 5 tons of water at 10°C to perform heat exchange. It appeared as one lumpy solid, and no phase separation was observed.

Similar experiments were conducted using sodium carbonate 0 hydrate and sodium 11 acid decahydrate instead of barium hydroxide octahydrate, and good results were obtained in both cases.

Example 4゜Mg(NOa)26H20・A], (NO3), 9H
20 crystal I K9 was placed in a stirring tank, and the nuclide was immersed in warm water at 50°C to completely dissolve the crystal.

Next, 01 kg of xonotrite calcium silicate powder having an average particle size of 50 μm and a bulk specific gravity of 0 was introduced into the nuclide and sufficiently stirred to obtain a slurry.

Next, this slurry-like material is sealed in a transparent plastic container, and the container is immersed in a container containing 5 tons of water at 10°C for heat exchange. It appeared as a lumpy solid, and no phase separation was observed.

470-

Claims (1)

[Scope of Claims] (1) A heat storage material comprising a latent heat type heat storage material made of an inorganic compound that generates a phase fraction *gIt when melted and mixed with xonotrite-based and/or tobermorite-based calcium silicate. (2) The heat storage material according to claim (1), wherein the latent heat type heat storage material is a single inorganic compound hydrate salt or an inorganic composite compound hydrate salt. (8) The heat storage material according to claim (1), wherein the xonotrite calcium silicate has an average particle size of 20 μm to 100 μm. (4) The heat storage material according to claim (1), wherein the apparent bulk specific gravity of the xonotrite-based calcium silicate is 0.07 to 0.15. (5) The mixing ratio of the latent heat type heat storage material and the xonotrite calcium silicate is such that the latter has a volume ratio of 0.8 to 0.8 to the former.
12. The heat storage material according to claim (1).