JPS584755B2 - heat storage material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat storage material that can be used, for example, in cold storage equipment for air conditioning.

In recent years, the heavy use of air conditioners in the summer has caused a sudden and large demand for electricity, so each electric power company has been forced to average out the amount of electricity used during peak hours, and have started using heat storage equipment (for cooling). There is also a growing demand for the dissemination of

The main part of heat storage equipment is heat storage material, but since no suitable heat storage material has been found so far, it can be said that the development of new heat storage equipment has been delayed.

That is, as a known heat storage material for air conditioning, glauber's salt type (Na2S
o4・10H20) mixture (melting point 13℃, heat of fusion 44c
al/g), but like mirabilite alone, this mixture has the disadvantage of not forming a homogeneous liquid phase even when melted, so unless precipitation of anhydrous mirabilite is prevented very well, practical application is extremely difficult. Have difficulty.

Furthermore, it can be said that there are no mixture-based heat storage materials that melt into a uniform liquid phase.

The present invention has been made in order to compensate for such deficiencies in the past, and provides a heat storage material that becomes a uniform liquid phase when melted and is optimal for practical use.

The figure shows the phase diagram of the NaHCOO-■202 element system, in which Pe
represents the eutectic point.

(The eutectic point at -17.5°C was determined by the inventors' experiments.

) From this figure, the melting point of NaHCOO・2H20 is 25℃, and the melting point of NaHC00・3H20 is 17℃, but the melting point of both is not the congruent melting point but the peritectic reaction point, and even when melted, it does not form a homogeneous liquid phase. I understand that.

Therefore, since trihydrate has a melting point of 17° C., it cannot be put into practical use for the reasons stated above, even though it alone has the potential to be used as a heat storage material for air conditioning.

However, the inventors found that P1 point (NaHCOO49
．． The results shown in Table 1 were obtained by examining compositions at point P1 (also 44.2 weight).

In other words, an aqueous solution with a P1 point composition easily solidifies when cooled to below 10°C, and when the temperature is raised, it becomes 13-17
℃, at which time the heat of fusion is 32 cal/g
It absorbs heat and becomes a homogeneous liquid phase around 25°C.

On the other hand, an aqueous solution with a P2 point/composition easily solidifies when cooled to around 5°C, and when the temperature is raised, it finishes melting between 11 and 14°C, absorbing about 20 cal/g as heat of fusion.
It becomes a homogeneous liquid phase around 17°C.

Note that both exhibit remarkable thixotropic properties.

For example, an aqueous solution condensed at P2 point is 0℃ from the lever relationship.
Although approximately 1/2 of the unsolidified aqueous solution should coexist, such separation of the liquid phase was not observed, and to the naked eye, it appeared that everything had solidified, and for example, the liquid phase The whole thing solidified so hard that even the thermocouple that was inside could not be removed.

Such special properties are extremely desirable for practical use as a heat storage material and for preventing phase separation.

In addition, both compositions did not cause any inconvenience no matter how many times the heat cycle of melting and solidification was repeated.

Practical aqueous solution concentration is NaHC0040~55
When the NaHCOO concentration exceeds 49.9, which can be said to be in the weight range, the excess NaHCOO is difficult to dissolve and precipitates, but it becomes very easy to solidify, and in terms of calorific value, some of it is peritectic. It was observed that the reaction occurred to form a trihydrate and the heat of fusion increased by more than 10%.

It goes without saying that the heat storage material according to the present invention can be used for purposes other than air conditioning.

The present invention will now be described in detail with reference to Examples.

Example 1 49.9 kg of anhydrous NaHCOO was dissolved in 50.1 kg of water and then placed in a heat storage tank.

When this material was cooled to 10°C, it started to solidify, and after that, the exothermic temperature reached 16°C, and then the heat storage was completed.

When this heat storage tank is used to cool the air using the air cooling method, the temperature reaches 20°C.
The following air was obtained over several hours.

Example 2 45 kg of anhydrous NaHCO0 was dissolved in 55 kg of water, put into a storage tank, and cooled to start solidifying at 6° C., and solidification was completed after the exothermic temperature rose to 10.5° C.

The melting temperature of this product 5 was 11 to 15°C, and a cooling effect was observed for several hours.

As explained above, according to the present invention, an extremely high-performance heat storage effect can be obtained without requiring any means for preventing precipitation.

[Brief explanation of drawings]

The figure is a phase diagram of the NaHCOO-H20 binary system, where the vertical axis represents temperature and the horizontal axis represents the concentration (wt%) of NaHCOO. In the figure, the dotted line indicates the unclear portion, Pe indicates the eutectic point, and the numbers in parentheses indicate the concentration (wt%) of anhydrous NaHCOO.

Claims (1)

[Claims] 1 Add anhydrous sodium formate (NaHCOO) to water from 40 to
A heat storage material characterized by containing 55% by weight.