JPH0788503B2 - Heat storage material composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a heat storage material composition containing water as a main material, and in particular, an appropriate amount of activated carbon, graphite or charcoal is added as a nucleating agent for preventing supercooling. The present invention relates to a heat storage material composition containing a crystal refining agent or a thickening agent if necessary.

[Prior Art] For a heat storage material composition used for low temperature exhaust heat storage and air conditioning with cooling / heating, it is essential to select an optimum main material according to the management target temperature. When targeting, it is most effective to choose water as the subject. That is, water has a large solidification-melting latent heat as compared with other substances, and is expected to be the most advantageous main material in a heat storage material composition whose management target is near its freezing point (0 ° C).

In the heat storage material composition, prevention of supercooling is a common problem, but there is a big problem that a remarkable supercooling phenomenon occurs even in a water-based material, which is an obstacle to practical use. . That is, the supercooling phenomenon is a phenomenon in which the change from the liquid phase to the solid phase does not occur even after the theoretical freezing point is passed in the process of cooling the liquid phase substance, and the solidification starts only after the freezing point is considerably lower. is there. Therefore, the temperature at which the latent heat of solidification is to be generated, that is, the freezing point becomes unspecified, which is a fatal defect as a heat storage material for absorbing and generating heat in a specific temperature range.

[Problems to be Solved by the Invention] Conventionally, other heat storage material compositions whose main material is other than water (for example,
A lot of research has been conducted on materials containing CaCl ₂ as the main material and having a freezing point of around 30 ° C., and various attempts have been made to prevent the supercooling phenomenon by adding various nucleating agents for preventing supercooling.
The current situation is that research has not been carried out sufficiently in the case of heat storage material compositions containing water as the main material.

The present invention has been made in view of these circumstances,
It is an object of the invention to provide a heat storage material composition containing water as a main material, which can prevent the supercooling phenomenon from dropping as much as possible.

[Means for Solving the Problems] The present invention which has achieved the above object includes the following four inventions.

A first aspect of the present invention is a heat storage material composition containing water as a main material, wherein the heat storage material composition contains one or more kinds selected from activated carbon, graphite and charcoal as a nucleating agent for preventing supercooling. Is.

The second invention is a heat storage material composition having a gist in that a salt is added as a crystal grain refiner in addition to the above.

The third invention has a gist in that a heat storage material composition containing water as a main component contains graphite as a nucleating agent for preventing supercooling and also contains a water-soluble polymer substance as a thickening agent. It is a heat storage material composition.

A fourth invention is a heat storage material composition having a gist in that a salt as a crystal refining agent and a thickening agent are added to the composition of the third invention.

[Operation] When the temperature of the heat storage material composition consisting essentially of water is lowered, it does not solidify even if it passes through the freezing point of 0 ° C.
When it reaches 6 ° C, it begins to solidify rapidly. When vibration is applied at the time when the solidification further progresses, a part of the solid material re-melts, the temperature once rises, and the solidification again occurs. In this way, the state of progress from supercooling to solidification is unstable, and the degree of supercooling changes significantly depending on the rate of temperature decrease and the state of disturbance of the melt (water), so the latent heat generation temperature can be specified. Inevitably, the temperature control according to the usage temperature is inaccurate.

Therefore, the present inventors have proposed a nucleating agent that promotes crystallization in order to prevent water from becoming supercooled (nucleating agent for preventing supercooling).
As a result of various studies from the viewpoint of adding, the present invention has been completed by finding that the supercooling phenomenon of water is significantly alleviated by adding an appropriate amount of activated carbon, graphite or charcoal. That is, the target temperature for supercooling is within ± (2 to 3 ° C),
When various nucleating agents, especially carbon materials or porous materials, were selected and added to water and investigated, a slight difference was observed in the effect, but when any of the above three nucleating agents were added, It has been found that a significant effect of preventing supercooling is exhibited as compared with the above substances (for example, coke, fly ash, or other porous substances).

Regarding the amount of the nucleating agent used in the present invention, there is no meaning to set a special limitation depending on the type, but in order to more reliably exert the effect of addition, 0.05 to 1.0% (meaning weight%, The same) is preferable. The reason is, as will be shown in Examples described later, if less than 0.05%, the effect of preventing supercooling due to the addition of a nucleating agent may be insufficient. On the other hand, regarding the upper limit, the effect of supercooling is saturated at about 1%. Even if it is reached and added beyond it, no further effect can be expected. However, the above range does not indicate a range in which the effect is proportionally improved depending on the amount of the nucleating agent added, and there is no regular correlation between the amount of the nucleating agent added and the supercooling preventing effect. I was not able to admit. In addition, it is not possible to fully understand the reason why the unique effects of only the above three were found among the various carbon materials and porous materials used in the experiment, but the reproducibility of these three materials only It is surprising that it works well.

On the other hand, when water is cooled to solidify, the solid phase (ice) is not always generated uniformly throughout the system, and it is well known that it shows a deviation. . When the temperature is continued to be lowered in such a state, the container in which the heat storage material composition containing water as a main material is hermetically housed is expanded in an offset direction due to the volume-expanded ice, which deforms the container. In view of the fact that the heat storage material composition storage container is generally used in a state of being in close proximity to each other, it is not preferable for stable heat exchange with the external medium. The present inventors have made various studies from the viewpoint of eliminating such inconvenience. As a result, it has been found that inorganic salts such as sodium chloride, potassium chloride, calcium chloride, ammonium sulfate, potassium phosphate, potassium alum, sodium acetate, potassium citrate, etc. It was found that the organic salt exerts an effect as a crystal refining agent. That is, when such a salt as described above was added to water together with a nucleating agent for preventing supercooling, it exerted a function of refining ice crystals although it had some adverse effect on the effect of the nucleating agent. From such a place,
It was found that the salt is extremely effective as a crystal refining agent rather than as a nucleating agent for preventing supercooling. It is necessary to change the amount of salt added to the extent that it does not hinder the action of the nucleating agent.
It is preferably 0.1% or less.

Next, the present inventors also considered the environment in which the heat storage material is actually used, and tried to study the relationship between the environment and the nucleating agent.
In other words, the environment in which the heat storage material is actually used may be used in an air environment or in a liquid environment.The difference in heat exchange performance and the direction of heat transfer have their own unique effects. It is possible to receive. Therefore, an air tank that is relatively cooled from above and a water tank that is relatively cooled from below are prepared and studied. When activated carbon or charcoal, which has an apparent specific gravity smaller than that of water, is used as the nucleating agent, it is recognized that it is more effective to use the heat storage material in the air tank. From this tendency, it seems that the type of nucleating agent should be selected according to the environment in which the heat storage material is used. However, when graphite having a larger specific gravity than water is used as a nucleating agent, it cannot always be said that it is more effective to use it in an aquarium.
In this case, it was effective regardless of the usage environment. Although the details of this reason are unknown, it is presumed that there is some relation with the phenomenon that the cooled water once moves downward and then solidifies.

Further, the present inventors have also studied from the viewpoint that the effect of the nucleating agent becomes more clear if the nucleating agent is appropriately dispersed in water, and graphite is used as a nucleating agent for preventing supercooling. It has been found that, when contained, for example, a water-soluble polymer substance is contained as a thickener. That is, graphite has a larger specific gravity than water and tends to precipitate at the bottom of the container.However, when a thickener is added together with graphite, the graphite is in a state of being appropriately dispersed in water. This is because it is in an optimum state as a nucleating agent for cooling prevention. On the other hand, when activated carbon or charcoal was added to water together with the thickener, the effect of the thickener was hardly recognized. As is clear from the above point, activated carbon and charcoal are porous and have an apparent specific gravity smaller than that of water, and therefore it is considered that even if a thickener is added, the function of dispersing the nucleating agent cannot be exerted. . When a thickener is added, it is optimal to use graphite as a nucleating agent for supercooling prevention and salt as a crystal refining agent in consideration of the function as a heat storage agent composition ( Fourth invention), it was found that the effect of the thickener itself can be expected even when it does not contain a salt (third invention). The thickener is not particularly limited, but water-soluble polymer substances such as polyacrylic acid, polyvinyl alcohol and CMC are effective.

[Example] Example 1 Various substances were added to water as a nucleating agent to prepare various heat storage agent compositions containing water as a main material. The obtained heat storage material composition was heat-exchanged in an air tank (-10 ° C) or a water tank (-6 ° C), and the temperature at which the nuclear heat storage material composition began to solidify was investigated.

The results are shown in Tables 1 and 2, where Table 1 shows the results in the air tank and Table 2 shows the effect in the water tank. The numerical values in the table indicate the solidification start temperature (° C).

As is clear from the results shown in Tables 1 and 2, it is well understood that activated carbon, graphite, charcoal, etc. are effective as the nucleating agent for preventing supercooling. It was also effective when two or three of these nucleating agents were used in combination.

Example 2 From the viewpoint that the heat storage material composition needs to be able to cope with heat fluctuations in the actual operation, the present inventors conducted heat resistance tests for each case where activated carbon or graphite was used as a nucleating agent. That is, when activated carbon or graphite was used as the nucleating agent, the solidification starting temperature (° C) of each heat storage agent composition was investigated after holding at 60 ° C for a predetermined time.

Tables 3 to 5 below show the results when activated carbon was used as a nucleating agent. Table 3 shows 60 ° C. for 3 hours, and Table 4 shows 60.
Table 5 shows the results when the respective treatments were carried out at 60 ° C for 25 hours and at 60 ° C for 25 hours. The results shown in Tables 3 to 5 were obtained with an air tank.

It can be considered as follows from the results of Tables 3 to 5. That is, it can be said that the heat storage material composition containing activated carbon as a nucleating agent also has excellent heat resistance, although the measurement results have some variations and the regularity is difficult to recognize.

Next, the results of using graphite as a nucleating agent are shown in
The results are shown in Tables and 7. This result shows the coagulation start temperature (first time) when treated at 60 ° C for 10 to 12 hours and the coagulation start temperature (second time) after the same treatment after leaving it for another day and night. is there. Table 6 shows the results in the air tank, and Table 7 shows the results in the water tank.

Although it is clear by comparing the results of Tables 6 and 7 with the results of Tables 3 to 5, there is a tendency that activated carbon is superior to graphite in terms of heat resistance.

Example 3 Activated carbon (addition amount: 0.05%) was used as a nucleating agent for preventing supercooling, and the effect of adding various salts was investigated. The results are shown in Table 8. Although the effect was different depending on the type of salt and the addition amount thereof, almost no effect of the nucleating agent was significantly inhibited. Further, in the case of using any of the salts, the volume expansion of the heat storage material composition does not locally proceed within a certain range of addition (depending on the salt), and fine crystals are uniformly formed. However, there was no tendency to locally expand significantly.
The solidification start temperature in Table 8 is each measured value when cooling and heat dissipation are repeated for each sample.

Example 4 The effects of using activated carbon and graphite as nucleating agents for preventing supercooling and adding polyacrylic acid as a thickening agent were investigated. The results are shown in Tables 9 and 10, with Table 9 showing the results in the air tank and Table 10 showing the results in the water tank, respectively.

As is clear from the results of Table 9 and Table 10, when graphite is used as the nucleating agent, the addition of a thickening agent works more effectively. In the case of graphite, the effect as a nucleating agent is originally remarkable regardless of whether it is an air tank or a water tank.However, the coexistence of a thickener causes the graphite to disperse appropriately in water. It is thought that this was demonstrated.

On the other hand, when activated carbon is used as the nucleating agent, no improvement in the effect due to the addition of the thickening agent is observed, and the thickening agent rather acts to suppress the effect of the nucleating agent. This is because even if a thickener is added, it does not have any effect on the activated carbon that floats on the surface of the water, and the upper and lower parts of the heat storage material container are rather blocked by the thickener. It is thought to be because.

Example 5 Graphite was used as a nucleating agent for preventing supercooling, sodium chloride was used as a crystal refining agent, polyacrylic acid was used as a thickening agent, and the effect of adding each predetermined amount to water was investigated. did.

The results are shown in Tables 11 and 12, with Table 11 showing the results in the air tank and Table 12 showing the results in the water tank. For comparison, the results when fly ash was used as a nucleating agent are also shown.

As is clear from the results of Table 11 and Table 12, the heat storage material composition in this example showed the most ideal solidification start temperature. In each case, the effect of salt was recognized.

[Effects of the Invention] As described above, according to the present invention, a heat storage material composition capable of preventing a supercooling phenomenon as much as possible by containing activated carbon, graphite, charcoal or the like as a nucleating agent for preventing supercooling. Was realized.

Claims (4)

[Claims] 1. A heat storage material composition containing water as a main material, containing at least one selected from activated carbon, graphite and charcoal as a nucleating agent for preventing supercooling. . 2. A heat storage material composition containing water as a main component, containing at least one selected from activated carbon, graphite and charcoal as a nucleating agent for preventing supercooling, and a salt as a crystal refining agent. A heat storage material composition comprising: 3. A heat storage material composition containing water as a main component, wherein graphite is contained as a nucleating agent for preventing supercooling and a water-soluble polymer substance is contained as a thickening agent. Heat storage material composition. 4. A heat storage material composition containing water as a main component, which contains graphite as a nucleating agent for preventing supercooling, a salt as a crystal refining agent, and a water-soluble polymer as a thickening agent. A heat storage material composition comprising a substance.