JP2982397B2 - Latent heat storage material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a latent heat storage material.
More specifically, the present invention relates to a latent heat type heat storage material that reduces the degree of supercooling during solidification and exhibits stable performance over a long-term heat cycle.

[0002]

2. Description of the Related Art Water and crushed stone have conventionally been used as heat storage materials, but these materials have a low heat storage density (1 cal /
g · deg or less), which requires a fairly large regenerator in practical use. In addition, since the temperature inside the heat accumulator gradually decreases with the heat radiation, it is technically very difficult to obtain stable thermal energy.

On the other hand, in recent years, research and development for applying latent heat at the time of melting and solidification of a substance to heat storage have become active. A characteristic of such a latent heat type heat storage material is that it can stably absorb and release heat energy at a constant temperature corresponding to the melting temperature of the material at a high heat storage density of several tens cal / g.

[0004] By the way, with recent advances in solar heat utilization technology and waste heat recovery technology, heat storage at a relatively high temperature of about 90 ° C has attracted attention as a heat source for hot water supply. As a latent heat type heat storage material for performing heat storage at such a high temperature, an inorganic hydrate has attracted attention.

However, inorganic hydrates generally exhibit a so-called supercooling phenomenon in which the solidification starting temperature is lower than the melting temperature. Such a phenomenon significantly impairs the characteristic of the heat storage material that stably absorbs and releases thermal energy at a constant temperature when the inorganic hydrate is used as the heat storage material.

Ammonium alum NH ₄ Al (SO ₄ ) ₂ .12H ₂ O
Has a melting temperature of 94 ° C and a high latent heat of 54 cal / g (differential scanning calorimeter). A supercooling phenomenon is also observed. That is, the potassium alum once melted does not solidify even when left at room temperature of about 15 ° C. This is because the solidification start temperature of potassium alum is about-
It is 15 ° C., which results in overcooling corresponding to a temperature difference of about 110 ° C. Therefore, heat absorption at 94 ° C
It cannot be used alone as a heat storage material because the release is not smooth.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide an ammonium alum-based latent heat type heat storage material in which the degree of supercooling is reduced.

[0008]

The latent heat storage material of the present invention, which achieves the above object, comprises cesium sulfate Cs ₂ SO ₄ , cesium chloride CsCl, and cesium carbonate as nucleating agents on ammonium alum.
Cs ₂ CO ₃ or manganese ammonium sulfate (NH ₄ ) ₂ Mn
(SO ₄ ) ₂ [anhydride or hexahydrate] .

The degree of supercooling reduction varies depending on the proportion of the nucleating agent added. However, even if too much nucleating agent is added, not only the expected effect is not obtained but also the deterioration of the material is reduced. In general, it is used at a ratio of about 0.05 to 20% by weight, preferably about 0.1 to 10% by weight, based on ammonium alum.

[0010]

The degree of supercooling reduction exhibited by such a nucleation effect depends on the melting temperature Tm of the heat storage material and the solidification starting temperature.
Although indicated by the difference ΔTsc from Tsc, the value of ΔTsc can be significantly reduced by adding the nucleating agent in the above ratio to ammonium alum, and it is possible to use it as a heat storage material such as hot water supply. I do.

[0011] Along with this, the time required to return to the melting temperature is shortened, and in addition to exhibiting stable performance over a long period of time in a heat cycle test, more efficient heat storage action can be performed.

[0012]

Next, the present invention will be described with reference to examples.

Example 1 A mixture obtained by adding 0.2 g of Cs ₂ SO _{4 to} 10 g of NH ₄ Al (SO ₄ ) ₂ .12H ₂ O was sealed in a polyethylene container having a capacity of 20 ml.
Upon heating at 0 ° C., it melted at 94 ° C. When the melted sample was cooled at a cooling rate of 1 ° C./min, solidification started at 80 ° C. The solidification onset temperature was in the range of ± 5 ° C. even if the melting-solidification was repeated 20 times. Therefore, by adding this nucleating agent, the difference between the melting temperature and the solidification starting temperature (ΔT
sc) was raised from about 110 ° C. when no nucleating agent was added to about 14 ° C., and supercooling was significantly reduced.

Note that ΔTsc when Cs ₂ SO ₄ was added in the range of 0.05 to 20% by weight also distributed between about 10 to 20 ° C.

Example 2 In Example 1, when 0.1 g of CsCl was used instead of 0.2 g of Cs ₂ SO ₄ , the solidification starting temperature at that time was 70 ° C.
-Even when coagulation was repeated 20 times, it was within the range of ± 4 ° C. Therefore, by adding this nucleating agent, ΔTsc becomes about 1
From 10 ° C to about 24 ° C, supercooling was greatly reduced.

The ΔTsc when CsCl was added in the range of 0.05 to 20% by weight also distributed between about 20 to 30 ° C.

Example 3 In Example 1, 0.3 g of Cs ₂ CO ₃ was used instead of 0.2 g of Cs ₂ SO _4.
Was used, the solidification initiation temperature at that time was 76 ° C., and the temperature was within ± 6 ° C. even when melting-solidification was repeated 20 times. Therefore, by adding this nucleating agent, ΔTsc becomes about 1
From 10 ° C to about 20 ° C, supercooling was greatly reduced.

The ΔTsc when Cs ₂ CO ₃ was added in the range of 0.05 to 20% by weight also distributed between about 15 to 30 ° C.

Example 4 In Example 1, (NH ₄ ) ₂ Mn (SO ₄ ) was used instead of 0.2 g of Cs ₂ SO _4.
With ₂ · 6H ₂ O 0.3g, solidification starting temperature at this time is 75
° C, and when melting and coagulation were repeated 20 times, it was also within the range of ± 4 ° C. Therefore, by adding this nucleating agent, ΔTsc was changed from about 110 ° C. to about 20 ° C., and supercooling was significantly reduced.

Claims (1)

(57) [Claims] 1. An ammonium alum and sulfuric acid as a nucleating agent.
Cesium acid, cesium chloride, cesium carbonate or sulfuric acid
Latent heat storage material with gangnan ammonium added.