JPH0449037B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a spherical heat storage body.

As is well known, the latent heat based on the phase change phenomenon of melting and solidification of substances that occurs at a constant temperature is generally large and has the advantage of being able to store heat compactly, so heat storage methods and devices that utilize this latent heat are put into practice in various fields. ing. In these methods or devices, the shell is usually filled with a shell,
A heat storage body made of a heat medium is used to store and radiate latent heat accompanying phase changes of melting and solidification.

In the past, a hard shell was filled with a heating medium. In this case, although the net amount of heat transfer medium can be increased, the shell will be damaged when the heat transfer medium expands in volume due to the operating temperature. In anticipation of the maximum volumetric expansion, the heating medium was filled leaving a space corresponding to that amount. For example, it is shown in Japanese Patent Publication No. 56-16876 and Japanese Utility Model Publication No. 57-52551. According to these conventional techniques, there is no damage to the shell due to volume expansion during solidification of the heating medium.
However, the net amount of heat medium decreases in that space, which becomes an obstacle in securing the necessary amount of heat storage or heat radiation.

The present invention has been made in view of the above-mentioned points, and its purpose is not only to increase the amount of heat medium filled in a spherical shell as much as possible, but also to The purpose of the present invention is to provide a spherical heat storage body that does not cause damage to the shell due to volumetric expansion, and in particular can be used in spite of repeated heat dissipation and storage, as well as expansion of the spherical shell due to volumetric expansion during solidification of the heat medium. The object of the present invention is to provide a means by which a spherical shell can be contracted to its current state as the volume contracts in the liquid phase, and the spherical shape of the spherical shell can always be maintained.

In order to achieve the above object, the present invention consists of a spherical shell and a heating medium filled in this spherical shell that stores and radiates latent heat during phase changes of melting and solidification, and this heating medium is a liquid. In a spherical heat storage body that has the property of expanding its volume when changing from a phase to a solid phase, and is set so that a space remains within the spherical shell when the heat medium is in a liquid phase; The volume of the space within the spherical shell that remains when the heating medium is in the liquid phase is not determined so as to be able to absorb all of the volumetric expansion of the heating medium when the heating medium changes from the liquid phase to the solid phase. The spherical shell is sized to absorb only a portion of the spherical shell, and the remaining volumetric expansion of the entire volumetric expansion can be absorbed by concentric expansion of the spherical shell. The spherical shell is formed of a material that can expand concentrically in response to the volumetric expansion of the heat medium, and the range of the concentric expansion of the spherical shell is set within the elastic limit of the material of the spherical shell. This is a spherical heat storage body.

Next, examples of the present invention will be described in detail.

Figure 1 is a vertical side view showing an example of a spherical heat storage body when the heat medium is in a liquid phase, and Figure 2 is a spherical heat storage body when the heat medium changes from a liquid phase to a solid phase and expands in volume. 1 is a longitudinal side view showing one example of a body, in which 1 indicates a spherical heat storage body, 2 indicates a spherical shell, and 3 indicates a heat medium filled in the shell. As is well known, when the heat medium 3 is intended for thermal heating, it accumulates heat as sensible heat in the solid state, and then when it changes from the solid phase to the liquid phase, it accumulates a large amount of heat as latent heat of melting. However, when it completely changes to the liquid phase, it accumulates heat as sensible heat, and from the high temperature liquid phase state to the solidification temperature, sensible heat is normally released, and at the solidification temperature, the latent heat of fusion is first released. The heat accumulated as solidification is released as latent heat of solidification, and when cold heat is the target, it is accumulated as latent heat of solidification when changing from liquid phase to solid phase at a constant temperature, and when changing from solid phase to liquid phase,
It releases as latent heat of fusion, and expands in volume when changing from a liquid phase to a solid phase. Examples include the following.

That is, conventionally known magnesium chloride (MgCl ₂ ). Sodium chloride (NaCl). Caustic soda (NaOH). Calcium chloride hexahydrate (CaCl ₂ 6H ₂ O). It is an aqueous solution such as sodium carbonate decahydrate (Na ₂ CO ₃・10H ₂ O).

These heat carriers undergo a slight volume change due to temperature change when in the liquid phase, but expand considerably when solidified. As is well known, the volume expansion varies depending on the type of heat medium, but it usually expands by about 5% to 8% of the volume of the liquid phase.

Conventionally, when the heat medium 3 is in a liquid phase, the shell 2
In setting the space 4 to remain inside, the size of the space was set to such an extent that the amount of volumetric expansion when the heating medium solidified could be absorbed. Therefore, the size of Ciel 2 itself remained unchanged at all times. For example, when the heat medium solidifies, a space equivalent to 1.08 times the volume when it is liquid, that is, 8%, is set in advance.

Therefore, in order to achieve the above object, the present invention provides a space 4 in which only a part of the volumetric expansion can be absorbed without the space 4 absorbing the entire volumetric expansion due to solidification of the heating medium. determined by the volume of
This is so determined that it is absorbed by both the space 4 and the concentric expansion of the shell 2.

For example, when the heat medium 3 solidifies, it expands by 1.08 times the volume when it is liquid, or 8%.The space 4 absorbs the expansion by 5.5% and by the expansion of the shell 2 by 2.5%. It determines the size of In other words, when the heat medium 3 is filled by injection into the spherical shell 2 processed by a blow molding method, a vacuum forming method, etc., the heat medium 3 is of course a liquid, but the heat of the liquid is When filling the medium 3, the space 4 is filled with a space equivalent to 5.5% in the above example.

The spherical shell 2 itself not only expands in accordance with the expansion of the heat medium due to the internal pressure when the solidified heat medium expands, but also returns to its original state naturally, leaving the initial space when the heat medium changes to a liquid phase. configure to restore. That is, the range of concentric expansion of the shell 2 is kept within the elastic limit of the material of the shell 2. As a result, the spherical heat storage body always maintains its spherical shape regardless of repeated expansion and contraction, and no concentrated stress remains in a specific portion of the spherical shell, thereby preventing breakage.

The material is preferably a synthetic resin with a softening point of 90℃ or higher, which has good expansion and contraction properties, and other materials with high resistance to stress.
Considering heat resistance and processability, polypropylene,
High density polyethylene is preferred.

An example is shown below.

The heating medium 3 used was a mixture of potassium chloride aqueous solution as the main liquid, calcium carbonate as a supercooling inhibitor, silver iodide as a crystal accelerator, and sodium polyacrylate as a phase separation inhibitor. In this case, it was confirmed that the volume expansion during solidification at the solidification temperature was 1.08 times that of liquid, that is, 8% expansion.

On the other hand, the shell 2 was made of high-density polyethylene and had an outer diameter of 65 mm and a thickness of 1.2 mm. Then, the expansion amount of the heat medium 3 is 5.5% in the space 4,
By expanding the shell, it was possible to absorb 2.5%.

That is, when the heat medium 3 is in the liquid phase, A is the internal volume (cm ³ ) of the spherical shell 2, r is the radius (cm) of the inner diameter of the spherical shell, and is the volume of the heat medium 3 (cm ³ ).
When V is the volume of space 4 (cm ³ ) and S is the volume of space 4 (cm 3 ), then A=4/3πr ³ =4/3×3.14×(6.5−0.12×2) ³ /2≒128.44cm ³ and A=S+V Therefore, V=121.74cm ³ and S=6.69cm ³ .

That is, 121.74 cm ³ of heat medium 3 is filled, and the space is 6.69 cm.
cm ³ left.

On the other hand, when the heating medium 3 solidifies; the internal volume (cm ³ ) of the spherical shell 2 at the time of expansion is A′,
If the volume (cm ³ ) of the heat medium 3 during expansion is V', then V' = 131.48 cm ³ .

Furthermore, since A'=V', A'≒131.48 cm ³ and S=0.

Therefore, if the radius extension (cm) of shell 2 is ΔR, ΔR = 0.024 cm, and the shell absorbs 2.95 cm ³ equivalent to 2.5% of the volumetric expansion of the heating medium, and the space 4 absorbs 2.95 cm 3 . Therefore, 6.69 cm ³ was absorbed, equivalent to 5.5%.

In other words, the amount of volumetric expansion of the heating medium is determined by V'-V, so solving this gives ^9.74cm3 , of which the absorption by the shell, ^2.95cm3 , is
This corresponds to 30.3%, of which 69.7 is absorbed by space.
%.

The presence or absence of material failure of the shell in this example was investigated.

Generally, calculation of membrane stress in a thin spherical shell is as follows: P=ΔR×2×E×t/R ² ×(1−ym) σ=Pr/2t However, P: Internal pressure Kg/cm ² ΔR: As mentioned above Radius extension cm r: As mentioned above, the radius of the inner diameter of the sphere cm E: Longitudinal elastic modulus Kg/cm ² ym: Poisson's ratio σ: Membrane stress Kg/cm ² .

Therefore, when asked about the above concrete example,
Since E=0.56~1.05×10 ⁴ Kg/cm ² ym=0.4, E; 0.56×10 ⁴ Kg/cm ² P=0.024×2×0.56×10 ⁴ ×0.12/(3.13) ² ×( 1-0
.4) = 5.49Kg/cm ² σ = 5.49 x 3.13/2 x 0.12 = 71.60Kg/cm ² E; 1.05 x 10 ⁴ Kg/cm ² P = 0.024 x 2 x 1.05 x 10 ⁴ x 0.12 (3.13 ) ² × (1−
0.4)=10.29Kg/cm ² σ=10.29×3.13/2×0.12=134.20Kg/cm ² On the other hand, the tensile strength of high-density polyethylene is 245
~385Kg/cm ² , so the safety factor f = 245/71.60 = 3.42 times f = 385/134.20 = 2.87 times.

However, it is within the elastic range of high-density polyethylene,
The shell not only expands when the heat medium expands in volume, but also returns to its original state when it is in the liquid phase.

As mentioned above, since the volume of the space inside the spherical shell is determined so that only a part of the volumetric expansion of the heat medium can be absorbed, the heat medium can be accommodated in the spherical shell as much as possible, and stored and released. A larger amount of heat can be secured than before, and at the same time, the rest of the volumetric expansion of the heating medium can be absorbed by the concentric bulges of the spherical shell, so there is no breakage of the spherical shell. That is, it does not break despite expansion and contraction during repeated use.

Further, as described above, after the spherical shell expands, when the heat medium becomes a liquid phase, the spherical shell returns to its original state.
This is because the spherical shell is designed to expand and contract within the elastic limits of its material.
Therefore, the spherical shell always maintains its spherical shape.

If it does not expand or contract, the expansion force will concentrate locally, the spherical state will easily deform, concentrated stress will remain in the deformed part, and it will be easy to break in that part, but this is not the case.

Furthermore, when spherical heat storage bodies are densely assembled, gaps are created between the spherical heat storage bodies at a certain rate, and the fluid to be heat exchanged passes through these gaps.
When the spherical heat storage bodies are partially deformed as described above, the gap between the spherical heat storage bodies becomes small, and the flow path resistance becomes large. If this happens, the heat exchange efficiency will decrease, but there is no risk of this happening.

As detailed above, according to the present invention, the volumetric expansion of the heating medium during the phase change from the liquid phase to the solid phase can be absorbed not only by the space but also by the concentric expansion of the shell, resulting in the following effects.

No damage occurs when the heat medium expands in volume from the liquid phase to the solid phase. The remaining space in the liquid phase is not large.
This is because the space is predetermined to be as small as possible since the shell can absorb it by expanding. Therefore, as much heat medium as possible can be accommodated.

In particular, the spherical shell not only expands but also contracts to its original state. That is, it is designed to expand and contract within the elastic limits of the selected material.
Therefore, regardless of repeated expansion and contraction, the spherical shape of the spherical heat storage body is always maintained. Therefore, no concentrated stress remains in a specific part of the spherical shell, and there is no risk of breakage.

In addition, since the spherical heat storage bodies always maintain their spherical shape, there is no fear that the gap between the spherical heat storage bodies will become smaller, and the resistance of the fluid to be heat exchanged will not become particularly large. Therefore, there is no fear of a decrease in heat exchange efficiency.

It exhibits various practical advantages such as

[Brief explanation of the drawing]

The accompanying drawings show embodiments of the present invention, in which FIG. 1 is a cross-sectional view of a spherical heat storage body when the heat medium is in a solution phase, and FIG. 2 is a cross-sectional view of the spherical heat storage body when the heat medium is solidified. In the figure, 1 is a spherical heat storage body, 2 is a shell, 3 is a heat medium, and 4 is a space.

Claims (1)

[Claims] 1 Consists of a spherical shell and a heating medium filled in this spherical shell that stores and radiates latent heat during phase changes of melting and solidification, and this heating medium changes from a liquid phase to a solid phase. In a spherical heat storage body, the volume of which expands when the heating medium changes to , and is set such that a space remains within the spherical shell when the heating medium is in the liquid phase; The volume of the remaining space within the spherical shell is not determined so as to be able to absorb all of the volumetric expansion of the heating medium when it changes from a liquid phase to a solid phase, but only a portion of the volumetric expansion. The shell is designed to have a size that absorbs the volume of the heat medium, and the shell is set to have a size that absorbs the volumetric expansion of the heating medium, and the remaining volumetric expansion of the total volumetric expansion can be absorbed by the concentric expansion of the spherical shell. A spherical heat storage body formed of a material that expands concentrically in response to expansion, and further characterized in that the range of the concentric expansion of the spherical shell is set within the elastic limit of the material of the spherical shell. 2. The spherical heat storage body according to claim 1, wherein the shell is made of a plastic material having a softening point of 90° C. or higher. 3. The spherical heat storage body according to claim 2, wherein the shell is made of polypropylene. 4. The spherical heat storage body according to claim 2, wherein the shell is made of high-density polyethylene.