JPH03181590A - Latent heat storage material - Google Patents

Abstract

PURPOSE:To obtain a latent heat storage material reduced in extent of supercooling in coagulation and capable of exhibiting stabilized performance to long-term heat cycle by adding cesium carbonate, cadmium carbonate or copper carbonate as a nucleating agent to potassium alum. CONSTITUTION:The aimed heat storage material obtained by adding (B) cesium carbonate (Cs2CO3), cadmium carbonate (CdCO3) or copper carbonate (CaCO3) to potassium alum [KAI(SO4)2 12H2O] at an amount of about 0.05-20wt.% (preferably about 0.1-10wt.%).

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] 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 long-term thermal cycles.

[Conventional technology]

Water and crushed stone have traditionally been used as heat storage materials, but these have low heat storage density (lcal/g-de
g), which requires a fairly large heat storage device for practical use. Furthermore, as the heat is radiated, the temperature inside the heat storage device gradually decreases, so it is technically quite difficult to obtain stable thermal energy.

In response, research and development on applying latent heat during melting and solidification of substances to heat storage has become active in recent years. A feature of such a latent heat type heat storage material is that it can stably absorb and release thermal energy at a constant temperature corresponding to the melting temperature of the material at a high heat storage density of several tens of cal/g.

Incidentally, with recent advances in solar heat utilization technology and waste heat recovery technology, heat storage at a relatively high temperature of about 90° C. is attracting attention as a heat source for hot water supply.

Inorganic hydrates are attracting attention as latent heat type heat storage materials when storing heat at such high temperatures.

However, inorganic hydrates generally exhibit a so-called supercooling phenomenon in which the solidification initiation temperature becomes lower than the melting temperature.

This phenomenon occurs when inorganic hydrates are used as heat storage materials.
This significantly impairs the characteristic of heat storage materials, which is to stably absorb and release thermal energy at a constant temperature.

Potassium alum KA Q (SO2)2・1.2H20
has a melting temperature of 91'C and a latent heat of 55 cal/
g (measured by differential scanning calorimeter), it is very promising as a latent heat storage material for hot water supply, etc., but a supercooling phenomenon is also observed in the case of this inorganic hydrate. In other words, once molten potassium hydroxide is left at room temperature of about 15° C., it does not solidify. This is because the solidification start temperature of potassium pharynx is approximately -25°C, which results in supercooling corresponding to a temperature difference of 116°C.

Therefore, it cannot absorb and release heat at 91° C. smoothly, so it cannot be used alone as a heat storage material.

[Problem to be solved by the invention]

An object of the present invention is to provide a latent heat type heat storage material based on potassium pouch, which reduces the degree of supercooling.

[Means to solve the problem]

The latent heat storage material of the present invention that achieves the above object contains cesium carbonate Cs2Co3 as a nucleating agent in potassium pharynx.
It is made by adding cadmium carbonate CdC0 or copper carbonate CuC0°.

The degree of supercooling reduction varies depending on the addition ratio of one nucleating agent, but adding too much nucleating agent will not only fail to produce the expected effect.

Since it also causes deterioration of the material, it is generally about 0.05 to 20% by weight2, preferably about 0.1 to 1%, for potassium pharynx.
It is used in a proportion of 0% by weight.

Among these nucleating agents, CdCO3 and CuCO3 do not exhibit a nucleating effect simply by adding them;
Although it does not solidify even at room temperature, it only begins to exhibit its nucleating effect when a potassium pouch containing a nucleating agent is treated in some way. That is, the supercooled molten liquid of potassium pharynx is cooled to about -30°C and solidified,
Alternatively, by adding a small amount of potassium pharyngeal to this molten liquid and causing it to solidify, it will exhibit a nucleating effect when it undergoes skin formation, and will stably prevent supercooling even during long-term thermal cycles. It begins to show effects.

〔Effect of the invention〕

The degree of supercooling reduction shown by such a nucleation effect is shown by the difference Δtsc between the melting temperature Tm and the solidification start temperature Tsc of the heat storage material, but when the nucleating agent is added in the above proportion to the potassium pouch, By doing so, the value of ΔTsc can be significantly reduced.

In addition, the time required to return to the melting temperature is shortened, and together with the ability to exhibit stable performance over a long period of time in thermal cycle tests, more efficient heat storage can be achieved.

〔Example〕

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

Example 1 Cs2C in KA Q (So,)2'12H20log
The mixture to which 0,0,4g was added was sealed in a polyethylene container with a capacity of 20 mQ, and when heated at 100°C, it melted at 91°C. When the molten sample was cooled at a cooling rate of 1 degree/min, solidification started at 80°C.

This solidification initiation temperature remained within the range of 75 to 80°C even after repeating melting and solidification 20 times. Therefore, by adding this nucleating agent, the difference between the melting temperature and the solidification start temperature (Δ
Tsc) from 116 degrees when no nucleating agent is added to 1
The temperature ranged from 1 to 16 degrees, making it possible to significantly reduce supercooling.

Note that when Cs2Co was added within the range of 0.05 to 20% by weight, ΔTsc was 10 to 18 degrees in all cases.

Example 2 KAQ (So, ), -128,010g CdC0,
The mixture to which 0.2 g was added was sealed in a polyethylene container with a capacity of 20 mQ, and after heating and melting this at 100°C, this sample was once cooled to -30°C and solidified. When the solidification initiation temperature was measured in the same manner as in Example 1 using the sample that had undergone this solidification, solidification started at 59°C.

This solidification start temperature was within the range of 54 to 76°C even after repeating melting and solidification 20 times.6 Therefore, by adding this nucleating agent, the difference between the melting temperature and the solidification start temperature (Δ
Tsc) from 116 degrees when no nucleating agent is added to 1
The temperature ranged from 5 to 37 degrees, making it possible to significantly reduce supercooling.

In addition, when CdC0, was added within the range of 0.05 to 20 weight points, ΔTse was 25 to 40 degrees in all cases.

Example 3 In Example 2, CdCO30,2g17) was replaced by 1c
cuco.

When using 0.1g, the solidification start temperature at that time is 55℃
, and even when melting and solidification were repeated 20 times, 52~
The temperature was within the range of 57°C. Therefore, by adding this nucleating agent, ΔTsc increased from 116 degrees to 34 to 39 degrees, making it possible to significantly reduce supercooling.

In addition, when CuC0, is added within the range of 0.05 to 20 weight 2, ΔTsc is 34 to 42 degrees,
It was.

Claims (1)

[Claims] 1. A latent heat storage material made by adding cesium carbonate, cadmium carbonate, or copper carbonate as a nucleating agent to potassium alum.