JPH02298759A - Latent heat accumulation capsule used for latent heat accumulation tank - Google Patents

Abstract

PURPOSE:To increase a melting speed of a phase change substance by forming a latent heat accumulation capsule so that it is flat in a shape substantially and that the ratio between the average diameter of the main surface in the horizontal direction thereof and the average thickness is the vertical direction thereof is set in a specified range. CONSTITUTION:A latent heat accumulation capsule 1 is formed so that it is flat in a shape substantially and that the ratio between the average diameter in the horizontal direction of the capsule 1 and the average thickness in the vertical direction thereof is 2:1 to 10:1 or preferably 4:1 to 8:1. A phase change substance of this capsule 1 is a hydrate, and therefore it is melted by heating in some degree and separated vertically into a liquid phase 12 of small density and a solid phase 3 of large density. Since the capsule 1 is formed to be the flat one having the ratio as stated above, the area of contact of the phase change substance accommodated in the capsule 1 with the bottom part of the capsule is increased and the mixing properties of the liquid phase 2 of the phase change substance and the solid phase 3 thereof due to a vortex is promoted on a wide interface. By the improvement in contact melting and convection melting thus obtained, the melting speed of the phase change substance can be increased conspicuously.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a latent heat storage capsule used in a latent heat storage tank.

[Conventional technology]

Conventionally, latent heat storage tanks (hereinafter referred to as tanks) filled with latent heat storage capsules (hereinafter referred to as docapsules) are used to store heat in air conditioners and latent heat storage systems that use hot and cold water, etc. in Binobe houses. Known to store energy.

An air conditioner using a latent heat storage tank as a typical example of the above is explained with reference to FIG. A heat collector 21 is provided, and this is connected to a tank 22 constructed of iron, stainless steel, plastic, FRP, concrete, etc. via pipes 23 and 24.
A pump 25 is provided in the pipe 24, and a valve 26 is provided in the pipe 24.

The tank 22 typically has a volume of about 300 i' and has an internal capacity of about 70 i' made of thin-walled plastic such as high-density polyethylene.
Approximately 1,000 spherical capsules 27 (commercially available from Christobia, France) of diameter 27 are filled. The spherical capsule 27 contains, for example, calcium chloride hexahydrate (Ca
A phase change material (PCM) such as Cβ26Lo) is accommodated. While the medium heated in the heat collector 21 at about 60° C. passes around the capsule 27 in the tank 22, the capsule 27
The phase change material inside is heated to melt a portion of it. That is, during this melting, part of the heat of the medium is converted into latent heat of the phase change material.

The medium, which has thus been deprived of heat and has a low temperature of about 30° C., is again sent to the heat collector 21 and heated by solar heat. As the above cycle is repeated, all of the phase change material within the capsule melts, resulting in storage of high thermal energy of approximately 50°C.

When using this for air conditioning, the hot capsule 2
Another medium is flowed around 7, and the medium is heated by the heat released when the phase change material solidifies to obtain a high temperature medium, which is sent to a corresponding equipment for air conditioning (not shown).

If low-cost late-night electricity is used instead of a solar collector, a special heater is used to heat the circulating medium, thereby storing heat in the phase change material inside the capsule.

The following three performances are required for the above capsule.

■ The heat storage rate, that is, the melting rate is fast (especially when using late-night electricity, it is desirable that the melting rate is fast).

■ The heat dissipation rate, that is, the solidification rate, is fast (the solidification rate is approximately proportional to the melting rate).

■ Low unit price (low price is important since a large number of capsules are used).

[Problem to be solved by the invention]

Conventional spherical capsules have the advantage that the capsule body has a simple structure and is easy to manufacture, but because of their spherical shape, the distance to the center is long. Therefore, it takes a long time for external heat to be transferred to the phase change material in the center of the capsule, resulting in a slow melting rate.

It is therefore an object of the present invention to devise an alternative capsule shape to the conventional spherical capsule to increase the rate of melting of phase change materials.

[Means to solve the problem]

The above object is to provide a latent heat storage capsule having a phase change substance therein and stored in a stacked state in a substantially horizontal state in a latent heat storage tank, wherein the capsule has a substantially flat shape;
and the ratio of the average diameter of the main surface in the horizontal direction to the average thickness in the vertical direction of the capsule is 2=1 to 10:1, preferably 4.
This is achieved by a latent heat storage capsule used in a latent heat storage tank characterized by having a ratio of :1 to 8:1.

〔Example〕

The present invention will be described in detail below with reference to the drawings.

Example 1: As described above, the center of a conventional spherical capsule is located at the maximum distance from the outer surface of the capsule, and the melting rate of the phase change material is slow due to the external heat medium. Therefore, we focused on the fact that by reducing the vertical thickness of a spherical capsule, the distance from the outer surface to the center becomes shorter and the melting speed becomes faster. A comparative test was conducted on the spherical capsule 27 shown in FIG. In reality, both types of capsules were uniformly heated from the surroundings using a heater, and the temperature was controlled using a slider to observe changes in the phase-change material filled inside. Since the phase change substance (CaC126H20) inside the capsule is a hydrate, it is melted by heating to a certain extent and separates into a lower density liquid phase 2 and a higher density solid phase 3, respectively. 4 indicates the center of the capsule.

The melting mechanism in this case is divided into contact melting and convective melting, with most of the melting (70%) occurring through contact melting between the solid phase 3 and the bottom of the capsule 1, and the remaining 30% occurring through convective melting within the capsule. It was observed that M. This allows solid phase 3
It has been found that the larger the contact area between the capsule 1 and the capsule 1, the faster the melting rate.In other words, it has been found that it is effective to make the capsule flat.

Furthermore, if the capsule is flat, vortices 7 in the directions of arrows 6 are generated alternately in the liquid phase 2 on the interface 5 (this phenomenon has been proven by Benard's principle, so its explanation will be omitted). . That is, since a large number of vortices in opposite directions are generated in the liquid phase, convective melting occurs at the interface 5 between the liquid phase 2 and the solid phase 3, and the two phases mix well, which also increases the melting rate.

On the other hand, in the case of the conventional spherical capsule 27, as shown in FIG. 2, the contact area between the surface phase and the capsule is smaller than that in FIG. Only a pair of vortices 7 opposite to each other are generated, but these vortices 7 have a slow flow rate and a weak mixing force between the liquid phase 2 and the solid phase 3, resulting in a slow melting rate.

The above comparative test was conducted on high-density polyethylene capsules of the same thickness and volume.

FIG. 3 shows a comparison of the melting rates depending on the shape of each type of capsule. In the figure, the vertical axis represents the melt/bond ratio, ie, the melted volume/inner volume of the phase change material, and a value of 1 indicates that the phase change material has all melted, and the horizontal axis represents time. Note that each type of capsule is formed to have the same volume.

In the figure, A is a conventional spherical capsule, B, C, and D are spheroidal capsules, and B, C, and D are the ratio of the diameter of the main surface in the horizontal direction to the average thickness in the vertical direction (tentative name: aspect ratio). 2:1.4+1 and 8:1, respectively, and E indicates a disk-shaped capsule with an aspect ratio of 8=1.

As can be seen from the figure, the melting rate of the spheroidal capsule, particularly the disk-shaped capsule (both of which are in the shape of a rotating body), is extremely fast when compared to the melting rate of a spherical capsule of the same volume. In this way, a rotating capsule with an aspect ratio of 2 or more is superior to a spherical capsule, but when considering a disc-shaped capsule, for example, to determine the upper limit of the aspect ratio, a circular capsule with an aspect ratio of 10:1 is superior to a spherical capsule. The amount of material required for a plate-shaped capsule is as follows when the thickness is the same:
Since this is four times the volume of a spherical capsule with the same volume, it is desirable to set the upper limit to 10:1 or less.

Embodiment 2: FIG. 4 is a perspective view of a rectangular parallelepiped capsule 8. In this case as well, fast melting can be achieved if the ratio of the average diameter of the main surface 9 in the horizontal direction to the thickness 10 in the vertical direction is 2:1 or more. It turns out that speed can be achieved.

Embodiment 3: According to the present invention, the capsule is made into a flat shape, resulting in a slightly larger (large diameter) capsule.
) If a smaller number of large flat capsules are used than the spherical capsules used, the effort of arranging a large number of capsules horizontally can be simplified. However, in this case, the circulation of the medium around the flat capsule is poorer than that of the spherical capsule, so the fifth
As shown in the figure, it is convenient to provide, for example, at least one cylindrical through hole 12 that communicates with the upper and lower parts of the disc-shaped capsule 11. Further, when a plurality of outwardly projecting protrusions 13 are provided on the surface of the capsule 11, the protrusions 13 serve as spacers between the capsules 11 stacked one above the other, thereby improving the circulation of the medium. .

〔Effect of the invention〕

The present invention is constructed as described above, and the ratio of the diameter to the thickness of the main surface is 2.
= 1 to 10:1, the contact area between the surface phase of the phase change material housed in the capsule and the bottom of the capsule is increased, and the liquid phase of the phase change material and the surface phase are formed on a wide interface. The increased vortex mixing and the resulting enhanced catalytic and convective melting can significantly increase the melting rate of the phase change material.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal cross-sectional view of the capsule of the present invention, Fig. 2 is a longitudinal cross-sectional view of a conventional spherical capsule, Fig. 3 is a comparison of melting rates depending on the shape of each type of capsule, and Fig. 6 is a cross-sectional view. The figure is an overall schematic diagram showing a conventional air conditioner. i, a, ti...capsule, 12...cylindrical through hole, 13...protrusion.

Claims (1)

[Scope of Claims] 1. A latent heat storage capsule having a phase change substance therein and stored in a latent heat storage tank in a substantially horizontal manner in a stacked manner, wherein the capsule has a substantially flat shape; A latent heat storage tank characterized in that the ratio of the average diameter of the main surface in the horizontal direction to the average thickness in the vertical direction of the capsule is 2:1 to 10:1, preferably 4:1 to 8:1. Latent heat storage capsule used. 2. The latent heat storage capsule according to claim 1, wherein the capsule is in the form of a rotating body. 3. The latent heat storage capsule according to claim 1, wherein the capsule has a rectangular parallelepiped shape. 4. The latent heat storage capsule according to claim 2 or 3, wherein the capsule is provided with at least one cylindrical through hole that communicates with the top and bottom. 5. The latent heat storage capsule according to any one of claims 2, 3, and 4, further comprising a plurality of protrusions projecting outward on the surface of the capsule.