JPS5996184A - Heat storage material - Google Patents

Abstract

PURPOSE:To provide a heat storage material which controls supercooling of MgCl2.6H2O and is easy to use, prepared by adding a specified nucleating agent to MgCl2.6H2O. CONSTITUTION:At least one nucleating agent selected from among Ca(OH)2, CaO and Mg(OH)2 to MgCl2.6H2O in an amount of 0.01-10wt%. EFFECT:Supercooling of MgCl2.6H2O is reduced to a marked extent and a latent heat storage material useful within a relatively high temperature range is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention J The present invention relates to a heat storage material mainly composed of magnesium chloride hexahydrate, and particularly to a latent heat storage material useful in a relatively high temperature range.

[Prior art]

Magnesium chloride hexahydrate (MgCt2.6H2O melting point t
Since t7C) is inexpensive and has a large latent heat, it is a promising material as a heat storage material for air conditioning or exhaust heat recovery. However, the phenomenon of supercooling occurs during heat dissipation, and latent heat is not released even if the temperature drops by about 25υ from the freezing point. FIG. 1 shows the solidification characteristics of magnesium chloride hexahydrate, with time t plotted on the horizontal axis and temperature T plotted on the axis. In this experiment, 100g of magnesium chloride hexahydrate was placed in a glass container.
After completely melting in an electric furnace at 150C, the temperature is about 2
The temperature was measured by cooling the thermocouple in the atmosphere at 5C, and by connecting the hot junction of the thermocouple to magnesium chloride 6 in a glass container.
The thermoelectromotive force was measured by placing it in a dot recorder. The temperature of magnesium chloride hexahydrate continues to decrease with time, and supercooling is corrected at 90C, after which it returns to its freezing point Tl] = 117C and begins to release latent heat. Freezing point Ts and supercooling recovery temperature T, = 90t:? The difference is 27C
This often causes difficulties in the thermal design of heat engines and refrigeration equipment that use latent heat storage tanks.For example, heat storage capsules containing heat storage material (magnesium chloride hexahydrate) In a capsule heat storage tank containing a large number of metals (copper, stainless steel, etc.), if the temperature of the heat medium (oil, fluorocarbon, etc.) flowing outside the tank is 100 R, the heat storage material does not release latent heat of solidification, so the temperature should be at least 90 C or lower. It has to be lowered.

If the latent heat of solidification is extremely lowered in this way, it is disadvantageous because it lowers the efficiency of heat engines and refrigeration equipment using latent heat storage tanks.

[Purpose of the invention]

The present invention aims to suppress the above-mentioned supercooling phenomenon of magnesium chloride hexahydrate and modify it into a substance that can be easily used as a heat storage material.

[Summary of the invention]

After searching through trial and error for a nucleating agent that facilitates nucleation of magnesium chloride hexahydrate, calcium hydroxide (Ca (OH
)2), calcium oxide (C,:10), and magnesium hydroxide (Mg(OH)2) were found to be extremely effective as nucleating agents.

[Embodiments of the invention]

[Example 1] A mixture of 100 g of magnesium chloride hexahydrate and 1 g of calcium hydroxide (Ca(OH)2) was placed in a glass container, and the container was placed in a 1500 electric furnace to completely boil it. After melting, this was allowed to cool in the atmosphere at a temperature of 25C. Supercooling is cured at 112C, freezing point Ts=11
The temperature returned to 7C and latent heat release started. In this experiment, the degree of supercooling ΔTs, the freezing point Ts, and the supercooling recovery temperature llI
It was found that the difference with r was as small as 5C. (Figure 2) When similar experiments were conducted 30 times using the same sample, the degree of supercooling ΔT8 was in the range of 2 to 5C. The latent heat of this heat storage material was measured with a differential calorimeter and was found to be 41 kal/Ky.

[Example 2] A mixture of 100 g of magnesium chloride hexahydrate and 0.01 g of calcium hydroxide (Ca(OH)z) was placed in a glass container, and the same test as in Example 1 was conducted. The degree of supercooling ΔTs was also 2 to 5C. The latent heat of this heat storage material was measured with a differential calorimeter and was found to be 41 days/nil.

2J Lucium oxide (CaO), Magnesium hydroxide (M
A similar experiment was conducted on (g (OH) 2 ), and the degree of supercooling was again in the range of 2 to 5C.

The amount added before nucleation may be extremely small, and Example 2
As shown in , even a concentration of 0.01 weight percent is sufficiently effective. There is no particular upper limit to the amount of nucleating agent added, but if too much is added, the heat storage capacity will decrease, so it is preferably 10% by weight or less.

〔Effect of the invention〕

As explained above, according to the present invention, the degree of supercooling of magnesium chloride hexahydrate, which is a heat storage material, is significantly reduced, making it suitable for practical use.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the solidification characteristics of a conventional heat storage material, and FIG. 2 is a diagram showing the solidification characteristics of the heat storage material of the present invention. -59(

Claims (1)

[Claims] 1. A heat storage material made by adding one or more substances from the group consisting of calcium hydroxide, calcium oxide, magnesium hydride and derivatives thereof as a nucleating agent to magnesium chloride hexahydrate. . 2. The heat storage material according to claim 1, wherein a nucleating agent is added to magnesium chloride hexahydrate in an amount of o, oi to 10 weight percent.