JPS6011575A - Latent heat storage material - Google Patents

Abstract

PURPOSE:To provide a latent heat storage material which has a long life and does not cause phase separation on a repeated heat storage-dissipation cycle, by blending a specified carboxymethyl cellulose as a thickener in a latent heat storage material mainly composed of sodium sulfate decahydrate (or eutectic mixture). CONSTITUTION:Carboxymethylcellulose having a degree of etherification of 1.4 or above and a viscosity (1% aq. soln. viscosity) of 2,000cP or above, is used as a thickener. Sodium sulfate decahydrate (or eutectic mixture thereof with sodium chloride) (A), a nucleating agent (B) such as borax and 1-10pts.wt. (per 100pts.wt. component A) said thickener (C) are mixed together to obtain a latent heat storage material.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a latent heat storage material mainly composed of 804.10H20 and its eutectic. What is called heat storage is required, which extracts and uses it when it is needed.For heat storage, there are sensible heat storage methods that use the sensible heat of water, rocks, concrete, etc., and organic crystalline substances and inorganic water phase salts. There is a latent heat storage method that utilizes the latent heat that accompanies the phase change of The latent heat storage method is considered advantageous due to its advantages such as being able to be made smaller.

Na2S4.10H20 can be obtained in large quantities and at low cost as a by-product during petroleum desulfurization, has a large heat storage capacity of about 60 cal/7, and is non-toxic, so it has been studied as a promising latent heat storage material. The phase transition temperature of Na2S04.10H20 is 32°C, but this can be lowered by creating a eutectic with other inorganic salts, so an appropriate eutectic can be used depending on the heating setting temperature, etc. Sodium chloride, potassium nitrate, ammonium chloride, potassium chloride, etc. are known as salts for making eutectic products.

However, since the melting point of Na2SO4.10H20 is the peritectic point, it separates into two phases,
It has the disadvantage that it cannot function as a latent heat storage material because it causes a phase separation phenomenon in which unmelted crystals settle to the bottom. Na
During endothermic melting of 2S○4・10H20, approximately 30% of the total becomes Na2s04 (anhydride crystal), and the remaining Na2S
It separates into an aqueous solution containing O4 and two phases. During heat dissipation solidification, the two separated phases react to form Na2SC1+・10H20.
However, this reaction is slow due to the hydration reaction (and further delayed due to the supercooling phenomenon during solidification. Therefore, the amount of heat released during solidification is greatly reduced, making it difficult to use as a heat storage material. Conventionally, in order to prevent phase separation, thixotropic substances such as finely powdered silica, silica gravel, and attapulgite clay were mixed to maintain uniformity. However, since water is separated during repeated melting and solidification, the ability to prevent phase separation tends to be limited for a short period of time.

The present invention aims to provide a latent heat storage material mainly composed of Na2SO4.10H20 or its eutectic, which can store and release heat over a long period of time (does not cause phase separation even after repeated use), and therefore has a long lifespan. purpose.

The latent heat storage material of the present invention is a latent heat storage material consisting of Na2SO4.10H20 or its eutectic, a crystal nucleating agent, and a thickening agent. (Hereinafter referred to as CPS
It is characterized by using carboxymethyl cellulose as described above.

The inorganic salts used to make the eutectic in the present invention include all conventionally known salts, typically chlorides), IJ(NaCl), ammonium chloride (N(4Cl), chloride), Examples include potassium (Kcl) and potassium nitrate (KNO2).

Borax (N
a 2 B 407.10I (20) etc. are used.

The thickening agent is added in an amount of 1 to 10 parts by weight per 100 parts by weight of Na25O+.10H20 or its eutectic. If the amount is less than this range, the thickening effect will be low and phase separation due to melting and solidification cannot be prevented, and if it is used beyond this range, the increase in effect will be small and it will be economically disadvantageous.

Conventionally, when trying to use carboxymethylcellulose as a thickening agent in a heat storage material using Na2So4.10H20, the precipitation of cellulose glycolate occurs and the viscosity decreases, so the effect of preventing phase separation is small and the concentration increases. Although it was known that carboxymethyl cellulose does not act effectively as an agent, the inventors found that carboxymethyl cellulose with a degree of etherification of 1.4 or higher does not cause precipitation, and that the carboxymethyl cellulose has a high viscosity product with a 1% aqueous solution viscosity of 2000 CPS or higher. It was discovered that this material has sufficient viscosity to be used as a thickener for heat storage materials and prevents phase separation. In addition, carboxymethyl cellulose with a high degree of etherification has a small viscosity drop due to decomposition and deterioration, and has the effect of preventing phase separation over a long period of time, making it extremely effective as a thickening agent for heat storage materials.

Examples of the present invention are shown below.

Example 1 53gy of water heated to 40°C Carboxymethyl 5-cellulose (trade name Celogen HE15 manufactured by Daiichi Kogyo Seiyaku ■)
Add 2.5g of 00F) and stir until uniform. This is KNa2SO4 (anhydride crystal) 42I and Na2B40
A 100 g sample was prepared by mixing 7-1DH202, 5, and 9. The etherification degree of this carboxymethylcellulose is i, '46-1'f + aqueous solution viscosity is 2530CPS
It is. When the latent heat of fusion was measured using a calorimeter, it was found to be 4
5 Cal/,! It was i'. This sample was heated at 20°C and 40°C.
Melt and solidify 50 times between ℃ (repeated car, water separation,
No precipitate was observed, indicating that phase separation was prevented.

The amount of latent heat at this time is 38 cal! /jj.

As a comparative example, 9.4 g of attapulgite clay was added to 49 g of water heated to 40°C and stirred until it became thixotropic.
A similar test was conducted on a sample made by mixing Na2B4O7.10H202,69 and Na2B4O7, and the initial latent heat amount was 4' 6 Ca1l/g, and the latent heat amount after 5 o cycles was 21 cal! /g, upward separation of water due to phase separation was observed, demonstrating the superiority of the heat storage material according to the present invention.

Also, as a comparative example of carboxymethyl cellulose (A)
Daiichi Kogyo Seiyaku Co., Ltd.Product name: Celogen EP (degree of etherification: 065.1, viscosity of aqueous solution: 25,000 PS)
% water aqueous solution dust 10000 PS) as a thickening agent,
A sample was prepared in the same manner as in Example 1, but comparative example [A
), a fibrous precipitate was generated, making it impossible to create a uniform heat storage material, and in Comparative Example (B), due to insufficient viscosity, phase separation progressed with repeated melting and solidification.

Example 2 41 g of water and 2.5 g of Celogen HE1500F were added and stirred until uniform.
A sample of 100 g was prepared by mixing T(202,551).

When the latent heat of fusion was measured using a heat flow meter, it was found to be 38 cal.
It was J/9. The melting point of this sample is approximately 19°C;
After melting and solidifying 50 times between 0°C and 35°C, no water separation or precipitation was observed, indicating that phase separation was prevented.The latent heat amount at this time was 34Ca7/! It was 9.

As a comparative example, 9.4 g of attapulgite clay was added to 41 g of water.
After adding 9 and stirring until it becomes thixotropic,
When a similar test was conducted on a sample prepared by mixing 32 g of Na25O4 (anhydride crystal), 322 g of KNO, and Na, 2B407.10H202,59, the initial heat amount was 4 opal/, and the latent heat amount after 9.50 cycles was 2.
At q c a, I/FJ, upward separation of water due to phase separation was observed, demonstrating the superiority of the heat storage material according to the present invention.

patent applicant Toppan Printing Co., Ltd. Representative Kazuo Suzuki

Claims (2)

[Claims] (1) In a latent heat storage material consisting of sodium sulfate decahydrate or its eutectic, a crystal nucleating agent, and a thickening agent,
A latent heat storage material using carboxymethyl cellulose having a degree of etherification of 1.4 or more and a viscosity of aqueous solution of 2,000 centivoise or more as a thickening agent. (2) The latent heat storage material according to claim 1, wherein the thickening agent is contained in an amount of 1 to 10 parts by weight per 100 parts by weight of sodium sulfate decahydrate or its eutectic.