JPS59170178A - Heat storage material - Google Patents

Abstract

PURPOSE:A heat storage material, containing sodium carbonate decahydrate and sodium aluminate as principal components, capable of suppressing the supercooling phenomenon, having heat radiation characteristics, and usable for mainly passive solar houses and heating greenhouses, etc. CONSTITUTION:A heat storage material obtained by adding (B) preferably 0.01- 20wt% sodium aluminate as a supercooling inhibitor to (A) a heat storage material containing sodium carbonate decahydrate as a principal component or part of components. A crosslinking acrylic acid polymer, etc. as a gelling agent for preventing the phase separation may be further added thereto.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates primarily to a heat storage material used for heating passive solar houses, heating greenhouses, and the like.

Conventional configurations and their problems Storage of daytime solar heat during the winter and using it for nighttime heating has been attempted in passive solar houses and greenhouses. In these systems, the heat storage materials used include those that utilize the sensible heat of water, stones, etc., and latent heat storage materials that utilize the latent heat of materials during melting and solidification. In particular, the latter has characteristics such as a large amount of heat storage per unit volume, and heat storage and radiation are performed at a constant temperature.
Attention has been paid. There are various hydrates as heat storage materials suitable for use at temperatures below 40°C, which are used in passive solar heating systems, and among them, sodium carbonate decahydrate has a latent heat of approximately 6ocae/y. However, it has a melting temperature of about 36°C, making it a useful material.

Generally, when using hydrates as latent heat storage materials,
The problem is the supercooling phenomenon during solidification (heat dissipation). That is, it does not solidify even when the temperature reaches the box transformation temperature from the molten state, but it radiates heat and solidifies after the temperature becomes considerably lower than the phase transformation temperature. This means that heat cannot be radiated even if the desired heating temperature is reached, which is inconvenient. When heating sodium carbonate 1o hydrate, it changes from 10 hydrate to 7 hydrate at 32°C and 36°C.
However, when cooled from 35°C or higher, the reverse process does not necessarily occur, especially for monohydrate.
When producing 0-hydrate salt, supercooling tends to occur, and 10-hydrate salt is produced only when the temperature drops below 6°C.

Purpose of the Invention In view of the above circumstances, the purpose of the present invention was to suppress the supercooling phenomenon during solidification of sodium carbonate decahydrate.

Structure of the Invention The heat storage material of the present invention is a heat storage material mainly composed of sodium carbonate decahydrate, or a heat storage material obtained by adding sodium aluminate to the heat storage amount obtained by mixing sodium carbonate decahydrate with other substances. It will be done. The feature of the present invention is that sodium aluminate is added to the heat storage material containing sodium carbonate decahydrate as one of its components in order to suppress the supercooling phenomenon. The presence or absence of mixing of other substances for the purpose of adjustment, gelling agents, surfactants, etc. for the purpose of improving properties does not change the basic structure of the present invention and does not depart from the gist of the present invention.

DESCRIPTION OF EXAMPLE To sodium carbonate decahydrate was added a double cross-linked acrylic acid polymer as a gelling agent, and 0.01, 0.05, 0.1, and 1.5 of sodium aluminate were added, respectively.

A sample was prepared by adding 10% weight. Approximately 30p of the sample was placed in a sealed polyethylene container, a thermocouple for measuring the sample temperature was inserted into the center of the sample, the sample stored in the container was placed in a water tank, and the water temperature was adjusted to between 46°C and 10°C. The temperature profile of melting and solidification was measured by changing the temperature repeatedly. As a typical temperature profile, the temperature profile when five parts of sodium aluminate are added is shown in the figure. That is, during solidification, a large step indicating solidification is observed at about 30°C, and during melting, a corresponding step is observed at about 32°C. The effect of sodium aluminate as a nucleating agent for sodium carbonate decahydrate is clear because it stably shows the temperature profile shown in the figure even after repeated melting and solidification. As a result of examining the temperature profile of samples with varying amounts of sodium aluminate added, 0.01% by weight
This effect was also observed upon addition, and it was confirmed that decahydrate was produced after supercooling to about 17°C. In addition, a heat storage material whose main component is a eutectic mixture containing sodium carbonate decahydrate and sodium sulfate decahydrate in a ratio of 1 mole to 1 mole has already been disclosed as a supercooling inhibitor for sodium sulfate decahydrate. The sample to which only borax was added showed supercooling phenomenon when cooled from 35°C or above, but it was confirmed that supercooling was suppressed in the sample to which sodium aluminate was added. It was done.

Sodium carbonate of sodium aluminate according to the invention 1
The effect of suppressing supercooling on zero hydrate salt can be obtained from a concentration as low as 0.01% by weight.On the other hand, there is no reason to limit the upper limit of the amount added, considering the effect of suppressing supercooling. Since it causes a decrease in the amount of heat storage, it is practically undesirable to add more than 20% by weight.

Effects of the Invention As described above, the present invention provides a heat storage material containing sodium carbonate decahydrate as a main component, and a heat storage material containing sodium carbonate and lithium decahydrate as part of its components, in which sodium aluminate is added as a supercooling inhibitor. It has the advantage of suppressing the supercooling phenomenon and obtaining favorable heat storage and heat dissipation characteristics.

[Brief explanation of the drawing]

The figure shows the melting/solidification profile of a sample in which 5% by weight of a crosslinked acrylic acid type coalesced double layer and sodium aluminate were added as a phase separation inhibitor to sodium carbonate IJ decahydrate.

Claims (1)

[Claims] A heat storage material comprising at least sodium carbonate decahydrate and sodium albanate.