JPS585386A - Latent heat accumulating material composition - Google Patents

Abstract

PURPOSE:The titled composition useful for solar air conditioning, etc., prevented from undergoing phase separation in solidification and heat evolution and given a prolonged life, which is prepd. by compounding sodium sulfate decahydrate with specified amts. of acid clay and an O/W synthetic resin emulsion. CONSTITUTION:To 100pts.wt. sodium sulfate decahydrate are added 10-20pts.wt. acid clay and 5-15pts.wt. W/O synthetic resin emulsion such as styrene/acrylate copolymer emulsion to form the titled composition. The emulsifier used for said emulsion is pref. an anionic one, and the particle size of the emulsion is advantageously less than several mum.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat storage material composition mainly composed of sodium sulfate decahydrate. It has improved performance.

Conventional -1 Methods that utilize the sensible heat of water are mainly used for heat storage used for solar heating and cooling and hot water supply, but this method requires a larger heat storage device and also requires more heat release. At the same time, there is a drawback that the temperature of the heat storage material itself decreases. On the other hand, examples of methods using latent heat include those using organic crystalline substances and inorganic water salts.

In principle, this method utilizes the phase change phenomenon between the solid and liquid phases of a substance, so it is possible to release heat at a constant temperature unique to the substance, and the accompanying temperature change in the heat storage material is moderate. Moreover, since the amount of heat per volume (weight) is larger than that of sensible heat, there are advantages such as the ability to downsize the heat storage device.

The present invention is a technology for storing heat using the latent heat of fusion of inorganic water salt substances, which is particularly inexpensive, has a melting temperature range suitable for solar air conditioning systems and hot water supply, and has a heat storage capacity of approximately 60 Ca I/g.
The present invention relates to a technology for modifying sodium sulfate decahydrate, which is large in size, so that it can be used as a heat storage material for a long period of time.

Sodium sulfate decahydrate (hereinafter referred to as Na2SO4.10H
20) is obtained in large quantities and at low cost as a by-product during petroleum desulfurization, and has a relatively large amount of heat storage, but its melting point is the peritectic point, and as heat storage and release are repeated, it gradually 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 of the vessel.

The present invention uses a mixture of acid clay and O/W type emulsion latex as a phase separation inhibitor to further improve the phase separation prevention effect compared to conventional viscosity substances. Describe the details of the invention.

In general, the phase separation phenomenon is a phenomenon peculiar to peritectic point-based materials, and for this reason, its application to latent heat type heat storage materials has been significantly restricted. When the typical Na 280 a.10H20 is endothermically melted, about 30% of the total becomes Na25Oa (anhydride crystal), which separates into two phases from the remaining aqueous solution containing Na25O,a. During heat dissipation and solidification, it is necessary to cause a reaction between the two separated phases to produce Na2SO4.IDH2O, but this reverse reaction is extremely slow due to the water utilization reaction, and is further delayed due to the supercooling phenomenon during solidification. For this reason, the amount of heat released during solidification is greatly reduced, and the function as a heat storage material is completely lost. Up until now, methods have been used to prevent phase separation, such as mixing a chicken-tropic substance to maintain uniformity throughout.

For example, there is a method of adding attapulgite, which is a type of white earth. This substance has extremely high water absorption (Na
Na2SO4φ10 by adsorbing water molecules coordinated to ions
It seems that it wraps around H20 and contributes to preventing phase separation. However, since attapulgite also undergoes a dehydration phenomenon, the adsorbed water molecules are gradually released as the heat storage/release cycle is repeated. For this reason, although it depends on the conditions, in general, after several dozen cycles, a precipitate is formed due to phase separation and the amount of heat dissipation decreases.In other words, attapulgite's ability to prevent phase separation is limited to a short period of time. Thermal storage materials used in solar air conditioning systems and hot water supply systems are required to withstand use for at least 10 years.
Even if it is replaced midway through, it will require a service life of several years, and the phase separation prevention measures using acpulgite cannot meet this requirement.

The present inventors have been searching for a phase separation inhibitor that does not cause phase separation even after repeated heat storage and release over a long period of time and has a long lifespan. We have found that mixtures of synthetic resin emulsion latexes are extremely effective.

Acid clay is a highly adsorbent porous fine powder material whose main component is montmorillonite viscosity with a three-layer structure, and water molecules coordinated around Na2SO4 molecules and H+ ions between the layers are strongly bound and adsorbed. In addition, the resin emulsion molecules constituting the O/W type composite are bonded to the acid clay particles adsorbed through their hydrophilic group portions, acting as a binder between the acid clay particles, and forming a weak gel structure as a whole. This can be understood from the fact that acid clay has a thickening effect on emulsion latex. The emulsifier used in the emulsion latex may be either nonionic or anionic, but in the case of acid clay, anionic emulsifiers are preferred.

The synthetic resin may be of any type, but preferably has an emulsion particle size of several microns or less. In other words, acid clay and emulsion latex GX, Na25Oa・1ΩH20
It has a double effect of preventing phase separation and sedimentation phenomena by forming a weak gel structure.

Next, examples of the present invention will be described.

<Example> Borax 1.5gr in Na2SO4φ10H2045gr,
Acidic clay (85% or higher passing 200 meshes) 6g
4g of styrene-nacryl copolymer emulsion (Polysol CA-F manufactured by Showa Kobunshi ■, anionic concentration 45%)
This sample was prepared by adding r. Separately, as a comparison sample, Prisoner N
A25Oa・10 H2050gr with 2gr of borax added.

(Two types were prepared by adding 5 gr of attapulgium to the Bl (Al sample).) These were placed in a glass test tube into which a CC thermocouple was inserted, sealed tightly, and immersed in a water bath at 50°C. After melting and absorbing heat in the same way, it was immersed in a jewer bottle containing 1.000 ml of water to radiate heat. Changes in the heat storage material and water temperature were recorded and measured to determine the amount of heat released. This heat storage and heat release cycle was repeated. The rate of decrease in heat dissipation, solidification initiation temperature, and visual observation of the progress of the phase separation phenomenon were measured and tracked.

The results are shown in Table-1. This sample has a small heat storage material content, so the initial heat release amount is small, but it maintains 90% even after 60 cycles, whereas the comparative samples both have a large initial heat release amount, but the rate of decrease becomes larger as the number of cycles increases, and , the occurrence of phase separation phenomenon was observed.

In addition, the solidification start temperature (nucleation temperature) at 40 cycles is
(AI)Na 2804 ・10H20 at about 30°C, there is no significant difference in other samples. This indicates that the phase separation inhibitor used does not significantly contribute to the supercooling phenomenon.

2) Sediment generation patent applicant August 1982 2. h Mr. Haruki Shima, Commissioner of the Japan Patent Office, Indication of the case Patent Application No. 104210 of 1982 2, Name of the invention Latent heat storage material composition 3 Relationship with the person making the amendment Detailed description of the invention in the patent applicant's specification Description field

Claims (1)

[Claims] In a latent heat storage material made of sodium sulfate decahydrate, acid clay and oil-in-water synthetic resin emulsion (0/W type) are added in an amount of 10 to 20 parts by weight and 5 to 15 parts by weight, respectively, per 10 parts by weight of sodium sulfate decahydrate. 1. A latent heat storage material composition characterized by adding parts by weight.