JPS649559B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat storage device that utilizes the latent heat of fusion of chloride or gaseous hydrate, and is used for air conditioning, waste heat recovery, solar heat storage, and the like.

Since salt hydrates or gaseous hydrates are generally very susceptible to supercooling, how to prevent supercooling is an important point when utilizing their latent heat of fusion.

In order to improve these drawbacks, a nucleation material is generally added, but the density of the nucleation material is usually higher than the density of the heat storage material hydrate liquid, so the added nucleation material is not suitable for heat storage. It often sinks to the bottom of the container. Now, if we consider the case where the nucleation material 3 is precipitated at the bottom of the heat storage container 1 as shown in FIG. 1, as the melt 2 of the heat storage material is cooled, the nucleation material 3 The heat storage material solid crystal 4 starts to grow from the surface of 3, and along with this, solidification heat is generated. When the height of the heat storage container 1 is relatively small, or when the heat storage container itself is not very large, only a small number of crystal grains generated from the nucleation material 3 are sufficient, and there is no practical inconvenience. It will never occur. However, when the height of the heat storage container 1 is large or the capacity of the heat storage container 1 is large, the area where the heat storage material solid crystals 4 grow from the nucleation material 3 is very limited at the beginning of heat dissipation. It becomes small, and most of the remaining state continues to remain in the supercooled region and undergoes only sensible heat changes. In other words, the amount of heat that can be extracted from the heat storage container is proportional to the number of crystal grains (~number of nucleation materials) present at the beginning of heat radiation, and in order to increase the heat radiation rate, it is necessary to increase the number of crystal grains. There is. As shown in FIG. 1, when the nucleation material 3 is precipitated at the bottom of the heat storage container 1, the number of crystal grains is uniquely dependent on the number of nucleation material 3.
In order to increase the heat dissipation rate, it is necessary to increase the number of nucleation materials 3. However, simply increasing the concentration of nucleating materials added will not achieve the intended purpose as long as all of the nucleating materials settle to the bottom. Our prior invention (Japanese Unexamined Patent Publication No. 51-70554) shows an example of such a solution. Another prior invention of ours (Utility Model Application No. 53-052651) relates to a method for easily and reliably arranging a large number of nucleating materials. However, this method requires a large amount of nucleation material, the processing and arrangement of the nucleation material used is complicated, and it requires a lot of time and money, making it difficult to work with and economically. , it had many shortcomings.

This invention was made to eliminate the drawbacks of the conventional ones, and by supporting the nucleation material on a substance lighter than the heat storage material melt and suspending it on the surface of the heat storage material liquid or in the heat storage material liquid, The object of the present invention is to provide a heat storage device that increases the rate of heat dissipation and heat absorption, makes the liquid phase composition uniform, and improves phase change stability.

That is, according to the present invention, as shown in FIG. 2, the nucleation material 31 supported by a light substance is suspended on the surface of the heat storage material melt 2. Once cooled,
First, the heat storage material solid crystal 4 starts growing from the surface of the nucleation material 31, as in the case shown in FIG. And as long as the crystal grains grown from the nucleation material are small enough, the change in apparent density is small.
It continues to float on the surface of the heat storage material melt. However, when the grown crystal becomes more than 10 times the volume of the nucleation material, its overall apparent density becomes greater than the density of the heat storage material melt, and it begins to fall through the liquid.
In other words, the density of a salt hydrate liquid is generally lower than the density of its solid, so when a solid forms in a liquid, it falls due to the density difference, and we are trying to actively exploit this tendency. This is the gist of this invention. Crystal grains falling through the liquid cause secondary nucleation due to collisions between crystal grains and interaction with the liquid, and the number of crystal grains further doubles. Crystal grains that reach the bottom will begin to grow there, and those that are attached to a suitable location along the way will begin to grow there, and as a result, the heat storage material will begin to solidify almost simultaneously from a large number of locations. , a large heat dissipation rate can be obtained. Such an effect is seen every time and reliably during solidification during a heat cycle.

Here, the carrier supporting the nucleation material has a bulk specific gravity of 1.6 g/cm ³ or less, which is lower than the density of the heat storage material melt, does not cause a chemical reaction with the heat storage material and the nucleation material, and is a heat storage material. Any material may be used as long as it does not easily collapse under the pressure of solidification. For example, various plastics such as polyethylene, vinyl chloride resin, acrylic resin, polycarbonate, cellulose acetate, polystyrene, celluloid, and their foamable resins, various rubbers, various inorganic substances such as glass fiber, and their foaming properties. Materials etc. will be listed.

As shown in Figure 3 a, b, and c, their structure is that the nucleation material 3 and a suitable carrier material (5) are mixed in an arbitrary ratio and molded into a spherical shape. In order to give buoyancy to a material whose density is lower than that of the heat storage liquid, or to a nucleation material alone or to a nucleation material with an appropriate binder added and formed into a spherical shape, etc., a carrier substance is not added to the surface. One in which the nucleation material molded product is homogeneously attached, or a similar nucleation material molded product is made into a columnar shape, the outer periphery of which is covered with a carrier, and the nucleation material molded product is exposed at both ends,
etc. are mentioned.

Experimental results using CaCl ₂ 6H ₂ O show that solidification first begins near the surface of the heat storage material, and then also from the bottom, but solidification is predominant from the top, and finally solidification occurs near the bottom ( It was found that solidification was completed at about 1/3 of the total length). Some excess water contained in the heat storage material will eventually collect at the point where solidification ends, but the density of the liquid in that area will always be lower than that of a liquid with a near stoichiometric composition, so the heat storage will not be possible. In addition to thermal convection when the material melts, an upward flow based on the density difference of the liquid naturally occurs, and the composition of the heat storage material becomes more uniform with each cycle of melting and solidification. Further, when excess moisture is present, the dissolution of the heat storage material solid is further promoted, and the dissolution time is shortened, that is, the heat absorption rate is improved. The nucleation material that has fallen through the liquid as the crystal grains grow regains its buoyancy as the heat storage material melts, and attempts to float to the surface of the heat storage material liquid due to the density difference. Such movement is very effective in making the composition of the heat storage material uniform, and greatly improves the phase change stability during repeated heat cycles.

As described in detail above, according to the present invention, 1. Increase in solidification rate (heat release rate) 2. Increase in melting rate (heat absorption rate) 3. Improvement in uniformity of heat storage material composition 4. Improvement in heat cycle stability 5. Nucleation Since there is no need to arrange materials, there are advantages such as shortened working time and improved workability.

The above explanation has focused on the case where the nucleation material is floating on the surface of the heat storage material. Depending on the density of the nucleation material, it may float in the heat storage material liquid.
Similar effects can be obtained in such cases as well. However, preferably 1/2 or more of the nucleation material floats on the surface of the heat storage material.

Examples will be described below.

Example 1 30% by weight polyethylene powder was added to BaHPO ₄ powder and melted to form a wire rod of 0.8 mmφ.
1.5mm thick polyethylene coating, thickness 1
Cut into mm. After filling CaCl ₂ 6H ₂ O into a polyethylene container with an inner diameter of 60 mmφ and a depth of 1500 mm,
Enclose and seal 100 pieces of the above nucleation material. This product broke supercooling at 25°C, and the temperature inside the container immediately rose to over 27°C, and was maintained at that temperature until the end of solidification. Heat cycle stability was good.

Example 2 After mixing 30% by weight polystyrene beads with IHINa succinate powder, the mixture is semi-melted to create a nucleation material with a diameter of about 5 mm. NaCH ₃ COO・3H ₂ O
and 20 mol% of NaHCOO.3H ₂ O was added as a heat storage material into a vinyl chloride container with an inner diameter of 50 mm and a depth of 300 mm, and 10 of the above nucleating materials were enclosed and sealed. When this product was cooled to below 30°C, supercooling was always broken, the temperature of the heat storage material was maintained at 51°C, and repeated heat cycles were possible.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a conventional heat storage container in which a nucleation material has sunk to the bottom; FIG. FIGS. 3a, 3b, and 3c are block diagrams showing the structure of a nucleation material according to an actual example of the present invention, respectively. In the figure, 1... heat storage container, 2... heat storage material melt, 3, 31... nucleation material, 4... heat storage material solid crystal, 5... carrier. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] 1. A heat storage tank containing a heat storage material made of a salt hydrate or a gaseous hydrate, and a nucleation material supporting a nucleation material so that its apparent density is lower than the density of the melt of the heat storage material. A heat storage device comprising a carrier, the nucleation material carrier being suspended in a heat storage material melt or on the surface of the melt. 2. The heat storage device according to claim 1, wherein the nucleation material carrier is formed by molding and curing a mixture of a nucleation material and a thermosetting resin or a thermoplastic resin. 3. The heat storage according to claim 1, wherein the nucleation material carrier is a nucleation material or a molded body thereof adhered to the surface of a thermosetting resin or thermoplastic resin granule. Device. 4. Claim 1, characterized in that the nucleation material carrier is a nucleation material or a molded body thereof coated with a thermosetting resin or a thermoplastic resin, leaving at least one open surface. The heat storage device described. 5. The heat storage device according to claim 1, wherein the nucleation material carrier is a thermosetting resin or a thermoplastic resin pipe filled with the nucleation material or its molded product. . 6. Any of claims 3, 4 and 5, characterized in that the molded body of the nucleation material is formed by molding and curing a mixture of the nucleation material and a thermosetting resin or a thermoplastic resin. The heat storage device described in Crab.