JPS6153385A - Heat-storing material - Google Patents

Abstract

PURPOSE:A heat-storing material of latent heat utilization type that is prepared by adding, as a supercooling preventive, sodium carbonate to sodium acetate trihydrate, thus showing stabilized thermal radiation without supercooling phenomenon. CONSTITUTION:The objective heat-storing material is obtained by adding, as a supercooling preventive, sodium carbonate to sodium acetate trihydrate or a composition containing more than 40wt% of the same. The sodium carbonate may be in any form selected its anhydride, monohydrate, decahydrate or their mixture and its amount to be added is 0.001-30pts.wt., in case of its anhydride, 0.05-30pts.wt. in monohydrate and 0.1-30pts.wt., in decahydrate, per 100pts.wt. of sodium acetate trihydrate. EFFECT:The breakage of supercooling is ensured over 56-57 deg.C and stabilized thermal radiation is obtained over 58 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field to which the invention pertains] The present invention relates to a heat storage material containing CH3COONa@3H2O as a main component.

[Technical background of the invention and its problems]

In general, there are two types of heat storage materials known: those that utilize the sensible heat of substances and those that utilize latent heat.

A heat storage material that uses latent heat has a feature that it has a larger amount of heat storage per unit weight or unit volume than a heat storage material that uses sensible heat, and can extract heat at a constant temperature at a phase change point. Therefore, by using a latent heat storage material, it is possible to create a compact heat storage system that can efficiently utilize thermal energy.

A large number of organic and inorganic substances are being considered as latent heat storage materials. Among them, hydrated salts undergo a phase change due to the involvement of water molecules in their crystals.

In particular, it generates a large amount of latent heat during melting and solidification, making it a promising material for heat storage.

However, in general, hydrated salts exhibit a supercooling phenomenon and the degree of supercooling is large, making it extremely difficult to reliably cause a phase change at a desired temperature over a long period of time.

CHa COON a, which is the main component of the heat storage material of the present invention
3H2O is also CH3CO, which is the main component of hydrated salt heat storage material.
ONa.3H2O is also excellent as a hydrated salt type heat storage material, but when it is put to practical use as a heat storage material, it is necessary to prevent the above-mentioned supercooling.

That is, CHs C00N a 93 H2O has a melting-eN solid phase change temperature of 58°C, and the calendar heat at that time is about 340 J/ar? Because it has a large + value, it is suitable as a heat storage material for use in heat storage systems for heating or hot water supply.

However, CH3COONa 3H2O has a large degree of supercooling, and if it is completely melted by heating and then cooled,
It has the property of not being easily supercooled to around 0°C and solidifying. This supercooling phenomenon may occur once CH3COONa@3
Even if heat is stored in H2O, the problem arises that the heat at a predetermined temperature cannot be taken out. Therefore CHs C00N a
- When using 3H2O as a heat storage material, preventing this supercooling is an important issue for practical use.

[Purpose of the invention]

The present invention aims to prevent overcooling of CHsCOONa 3H2O, which is a hydrated salt, and to provide a heat storage material with excellent practicality.

[Summary of the invention]

The feature of the present invention is that CHsCOONa 3H2O is the main component of the heat storage material, and sodium carbonate is added to prevent supercooling.As the sodium carbonate, anhydrous salt (Na2C
03) or monohydrate salt (NazCO3'H2O) or decahydrate salt (Na2COs@10H2O).

When a mixture of CHsCOONa-3H2O and Na2COs or Na2COs''H2O is heated to 30℃ or higher, CHsCOONa-3H2O melts at 58℃, but N12COs and Na2CO3''H2O do not melt and remain as solids. It settles to the bottom. Completely CH
After 3COONa・3H2O is melted, this mixture is cooled to about 57°C, and at the same time, CH3COONa・3H2O crystals begin to grow from the surface of the particles precipitated at the bottom, and these crystals are growing. During this time, the temperature of the mixture is maintained at approximately 58°C. Also NazCOs @
10H2O loses 9 molecules of water at temperatures above 35°C and changes to Na2CO3・H2O, so Na2CO3
The same supercooling prevention effect as when -10H2O is added can be obtained.

Since "Na2COs" hardly dissolves in the melt of CHsCOONa-3H2O, CHsCOONa・
3H2O 100 parts by weight [Na2CO3 0.00
By adding 1 part by weight or more, a reliable supercooling prevention effect can be obtained. Also, Na2COa/H2O is C
Because it dissolves slightly in the melt of H3COONa@3H2O,
For reliable supercooling prevention effect, use CH3COONa.
- It is necessary to add α05 parts by weight or more to 3Hz0100 parts by weight. Furthermore, NazCOs #10H
As mentioned earlier, 2O exhibits a supercooling prevention function after changing to NagCOs/H2O, and NazCOs
``About twice as much as when adding H2O, that is, CHsC
Na2CO3 per 100 parts by weight of OONa.5H2O
It is necessary to add 0.1 part by weight or more of 410H2O.

For the above minimum addition amount of sodium carbonate,
Of course, even if a large excess amount is added, it will have the effect of preventing supercooling, but if too much is added, the ratio of CHs COONa 3H2O in the unit volume will decrease, which will affect the heat storage material as a whole. This is not very preferable because it leads to a decrease in the amount of heat stored in the case. Therefore, from a practical standpoint, it is desirable to add 30 parts by weight or less of C to 100 parts by weight of CH3COONa'3H2O.

When using sodium carbonate as a supercooling prevention material for CHsCOONa・3H2O, other CHsCOON
It may be used in combination with a supercooling prevention material such as a.3H2O.

In addition, in order to uniformly disperse Na2CO3 in the melt of CHsCOONm・5H2O, a gelling agent such as carboxymethyl cellulose may be further added, or it may be used in combination with other additives such as a solidification temperature regulating material. , a reliable supercooling prevention effect is recognized.

By the way, the composition of the melt produced when CH3COONa@3H2O is heated to 30°C or higher is 30% of CHsCOONa.
．． It is the same as a 35% by weight aqueous solution.

Therefore, CH3C00N a is mixed with 6α35m11 parts and H2O
Even if the mixture obtained by adding NaxCOs to the aqueous solution obtained by mixing 39.65 parts by weight of NaxCOs and raising the temperature to 30°C or higher is cooled, the CHsCOO as described above does not change.
It goes without saying that the same solidification exothermic behavior is observed when the melt obtained by heating a mixture of Na 3 Hz O and Na 2 COs to 30° C. or higher is cooled.

[Embodiments of the invention]

Example 1゜CHsCOONa'3Hz02Og and Na2CO3α
[12 g was placed in a test tube with an inner diameter of 18 rnrD and a length of 180 rnrD, a thermocouple (C, C) was inserted into the center, and the upper end was sealed with a rubber stopper. The test tube was then placed in a constant temperature bath at 70°C and sufficiently heated until CHa COON a.5H2O was completely melted and the temperature reached 70°C.

Next, this test tube was transferred to a constant temperature bath at 20° C. and cooled, and the temperature change inside the test tube at that time was measured. The results are shown in FIG. When the temperature at the center of the test tube containing the mixture of CHsCOONaφ3H2O and Na2COs drops to 57°C, CHsCOONa 3H is added from the lower part of the test tube.
Crystals of 2O began to grow, and the temperature at the center of the test tube rose to 58°C. Furthermore, for about 30 minutes thereafter, the temperature at the center of the test tube was maintained at 58°C. Next, the above thermal cycle of heating and cooling was continuously performed 1000 times. The temperature change observed during cooling in the center of the test tube during this 1000-time thermal cycle is the first.
It is almost the same as shown in the figure, and CHsCOONa・
The supercooling of 3H2O was reliably broken at a temperature of 56 to i7°C or higher, and the solidification exotherm could be repeated at 58°C.

Example 2゜CHsCOONa・5Hz02Og and NazCOs
A test tube containing 2 g of H2Oα was heated and cooled for 1000 cycles under the conditions described in Example 1.

The pattern of temperature change in the center of this test tube is exactly the same as in Example 1, and the supercooling of CHsCOONa.5H2O is reliably broken at a temperature of 56 to 57°C or higher, and 1000
The solidification exotherm at 58° C. could be repeated over the thermal cycle of the cycle.

Examples & CH3COONa・3H2O2Og and Na2COse1
0) As a result of repeating 1000 cycles of heating and cooling of a test tube containing 2 g of i2Oα under the same conditions as in Example 1, it was possible to repeat the solidification exotherm at 58° C. as in Example 1.

Example 4 2.1 g of CHsCOONa i, 7.9 g of H2O, and 12 g of Na2CO2O were placed in the test tube used in Example 1, and heated until the temperature at the center of the test tube reached 70°C.
The mixture in the test tube was thoroughly stirred.

Thereafter, heating and cooling cycles were repeated 1000 times under the same conditions as in Example 1. As a result, the solidification heat generation during cooling was 100%, which was exactly the same as the result in Example 1.
Observed over 0 heating and cooling thermal cycles.

〔Effect of the invention〕

As shown in the examples, CHxC with a large degree of supercooling
By adding sodium carbonate as a supercooling prevention agent to OONa@3H2O, supercooling can be reliably broken at temperatures above 56-57℃, and practicality with stable heat dissipation I# properties at 58℃ It has now become possible to provide a heat storage material that utilizes the latent heat of In.

[Brief explanation of drawings]

Figure 1 shows CHaCOONaφ3H2O described in Example 1.
FIG. 3 is a diagram showing the temperature change at the center of a test tube during cooling of a test tube containing a mixture of NaxCOs and NaxCOs.

Claims (1)

[Claims] 1. Sodium acetate trihydrate (CH_3COONa・3H
A heat storage material characterized in that it is a mixture obtained by adding sodium carbonate to a composition containing 40% by weight or more of sodium acetate trihydrate or sodium acetate trihydrate. 2. Sodium carbonate is an anhydrous salt (Na_2CO_3), 1
Water salt (Na_2CO_3・H_2O), Decahydrate salt (Na
_2CO_3.10H_2O) or any mixture thereof. 3. Sodium carbonate per 100 parts by weight of sodium acetate trihydrate, 0.001 to 30 parts by weight in the case of anhydrous salt,
The heat storage material according to claim 1, wherein the amount of the monohydrate is 0.05 to 30 parts by weight, and the amount of the decahydrate is 0.1 to 30 parts by weight.