JPS604583A - Latent thermal energy storage material - Google Patents

Abstract

PURPOSE:To provide a latent thermal energy storage material capable of maintaining high thermal energy storage for a long period without degradation caused by phase-separation, and containing sodium sulfate decahydrate (or its eutectic mixture), a nucleating agent, and thickening agent comprising a water- insoluble and water-absorbing resin. CONSTITUTION:The objective material is composed of (A) 100pts.wt. of sodium sulfate decahydrate or its eutectic mixture, (B) a nucleating agent such as borax, and (C) usually 1-10% thickening agent composed of a water-insoluble and water-absorbing resin. The component C is those containing a polysaccharide and a water-soluble monomer as essential components, wherein the polysaccharide is preferably starch and/or cellulose and the water-soluble monomer is preferably a carboxyl-containing monomer such as (meth)acrylic acid, maleic anhydride, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides sodium sulfate decahydrate (hereinafter referred to as FNa2SO4.
101-120) or a eutectic thereof.

In order to reduce the load on solar heating and cooling systems and air conditioners, so-called thermal storage, which stores thermal energy and extracts it when needed, is required. Heat storage uses water, rocks,
There is a sensible heat storage method that uses sensible heat such as concrete, and a latent heat storage method that uses the latent heat associated with the phase change of organic crystalline substances and inorganic hydrated salts. The latent heat storage method is considered to be advantageous because of its advantages such as being able to release 20% of heat, and having a smaller heat storage device with a higher amount of heat per volume (M amount) than the sensible heat method. .

Na2SO4・10H20 can be obtained in large quantities and at low cost as a byproduct during petroleum desulfurization, and the company also produces approximately 6 o ca
It has been studied as a promising latent heat storage material because it has a high value of l/9- and is non-toxic. Na2SO4・1
The phase transition temperature of 0 J-J 20 is 32℃, 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. reactor. salt 1 arsenium, as a salt to make the eutectic;
Potassium nitrate, ammonium chloride, potassium chloride, etc. are known.

However, since the melting point of Na 2 SOa ・10H20 is the peritectic point, it separates into two phases with repeated heat storage and release, causing a phase separation phenomenon in which unmelted crystals settle to the bottom, so it cannot function as a latent heat storage material. There are no drawbacks.

When Na280A.10H20 undergoes endothermic melting, approximately 30% of the total becomes Na25OA (anhydride crystal), which separates into two phases from the remaining aqueous solution containing Na25Od. During heat dissipation solidification, the two separated phases react to form Na2SO4.1
0 H-20 must be produced, but this reaction is slow due to the hydration reaction and further delayed due to the supercooling phenomenon during solidification. For this reason, the amount of heat released during solidification is greatly reduced, and the material loses its function as a heat storage material. Conventionally, in order to prevent the phase separation phenomenon, a method has been adopted in which the mixture is kept homogeneous by mixing materials such as fine powder, diatomaceous earth, and atano (lugite clay). However, in many cases, water is separated during repeated melting and solidification, so the ability to prevent phase separation tends to be limited to a short period of time. Regarding a latent heat storage material mainly composed of a molten material, it is an object of the present invention to provide a heat storage material that does not undergo phase separation even after repeated heat storage and release over a long period of time, and therefore has a long life.

The latent heat storage material of the present invention is a latent heat storage material comprising Na2SO4-1oH20 or its eutectic, a crystal nucleating agent, and a thickening agent, in which a water-insoluble water-absorbing resin is used as a thickening agent. It is. Preferably, the water-absorbing resin contains a polysaccharide and a water-soluble monomer as essential components, or a polysaccharide, a water-soluble monomer, and a crosslinking agent as essential components, and is obtained by polymerizing and optionally hydrolyzing. A water-insoluble water-absorbing resin is used.

In the present invention, the inorganic salts used to make the eutectic include all conventionally known inorganic salts, typically salts (hysodium (NaC1), salt fhsodium (NH= C:l), potassium chloride (KCl,)
, sodium nitrate (ni-NO3). As the crystal nucleating agent, the already known borax (N a 2 B 407.10H20) or the like is used.

In the present invention, starch or cellulose, or starch and cellulose, is preferably used as the polysaccharide that is an essential component in the water-absorbing resin used as a thickening agent, and as the water-soluble monomer, acrylic acid, methacrylic acid, anhydrous It is preferable to use one monomer having a carboxyl group, such as maleic acid, because it has a high water absorption capacity and therefore performs an excellent function as a thickening agent.

Thickening agent (I) Add between 1 and 10 parts by weight per 100 parts by weight of Na25OA・101120 or its eutectic. If less than this, both viscosity and water absorption will be low and phase separation due to melting and solidification will occur. Even if it is used beyond this range, the effect of preventing phase separation is sufficient, so the effect beyond that is small and is rather economically disadvantageous.

When a water-absorbing resin is used as a thickening agent in the present invention, its function is to increase the viscosity. That is, by increasing the viscosity of the heat storage material solution, Na
Prevents precipitation of 25O4 (anhydride crystals). Furthermore, since the water-absorbing resin is water-insoluble and the heat storage material solution becomes gel-like, it exhibits a high yield value in viscosity. Therefore, it is characterized by a high ability to retain the generated Na2S04 (anhydride crystals) in the gel and a large phase separation prevention effect. Furthermore, since water can be reversibly taken in and out of the water-absorbing resin, the heat storage material can be maintained uniformly without separating water that is adsorbed and released from Na25O6 during melting and solidification.

Due to these functions, the heat storage material of the present invention exhibits less deterioration due to phase separation t than conventional heat storage materials such as ATB agents 1, such as attapulgite clay, and retains large heat storage properties over a long period of +C'. be able to.

Examples of the present invention are shown below.

Example 1 Water-absorbing resin (manufactured by Sanyo Hisei Kogyo ■, trade name: Zanwe 7 IM-100oMPs) was added to 53 ml of water heated to 40°C.
) and stir until uniform. To this, Na2so' (anhydride crystal) 421 and Na21340
Mix y ・10 H202,57- to make sample 1oo
Created y. When the latent heat of fusion was measured on the calorific value side, it was found to be 49 c = +l/'i. This sample was melted and solidified 50 times between 20°C and 40°C, but no water separation or precipitate was observed, indicating that phase separation was prevented. The amount of latent heat at this time is 44 cal
/ft.

As a comparative example, 40'CK heated water 49! After adding 9.4 g of attapulgite clay to iI- and stirring until it became thixotropic, N a a S OA
(Anhydride crystal) 39g- and Na zB407-10H2
When a similar test was conducted on a sample prepared by mixing 026I, the initial latent heat amount was 46 cal/y-
At a latent heat amount of 2 i C; + I/r after 50 cycles, upward separation of water due to phase separation σ) was observed, demonstrating the superiority of the heat storage material according to the present invention.

Example 2 Water 411 and Sanweno 1. I M -1000MJ'
Add 525z and stir until uniform, then add Na2
5OaC anhydride crystal) 32.2 g- and KNOs
218g- and N a 2 B t O7・101-
Mix 1202 and 551- to create sample ioog-1
-ta. When the latent heat of fusion was measured using a calorimeter, it was found to be 41
cal/1, the melting point of this sample was approximately 19°C, and although melting and solidification was repeated 50 times between 0°C and 35°C, no water separation or precipitate was observed, and phase separation was prevented. I understand that. The amount of latent heat at this time was 35C; 11/J.

As a comparative example, acpargite clay 941 was added to water 411.
was added, stirred until it became thixotropic, and then
a25OA (anhydride crystal) 3221 and KNO321
,8f and Na2B-07-108202,
When a similar test was conducted on a sample prepared by mixing 59- and 59-, the initial latent heat amount was 40 cal/latent heat amount was 29 cal/P after 7.50 cycles, and water separated upward due to phase separation. was observed, demonstrating the superiority of the heat storage system according to the present invention.

patent applicant Toppan Printing Co., Ltd.

Claims (3)

[Claims] (1) A latent heat storage material comprising sulfuric acid (IJ) hydrate or a eutectic thereof, a crystal nucleating agent, and a thickening agent, in which a water-insoluble water-absorbing resin is used as the thickening agent. (2) The water-absorbing resin contains polysaccharides and water-soluble monomers as essential components, or polysaccharides, water-soluble monomers, and crosslinking agents as essential components, and can be obtained by polymerizing and optionally hydrolyzing. The latent heat storage material according to claim 1, which is a water-insoluble water-absorbing resin. (3) The latent heat storage material according to claim 2, wherein the polysaccharide is starch, cellulose, or starch and cellulose. (The latent heat storage material according to claim 1, wherein the 4+pr aqueous agent is contained in an amount of 1 to 10 parts by weight per 100 parts by weight of sodium sulfate monohydrate or its eutectic.