JPH0788504B2 - Heat storage material composition - Google Patents

Description

[Field of Industrial Application] The present invention relates to a heat storage material composition containing water as a main material, and in particular, for preventing an appropriate amount of water-repellent activated carbon, graphite or charcoal from being overcooled. TECHNICAL FIELD The present invention relates to a heat storage material composition which is added as a nucleating agent for use and optionally contains a crystal refining agent and a thickening agent.

[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 select water as the main material. 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 (for example, a main material 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 which can prevent the supercooling phenomenon as much as possible in the heat storage material composition containing water as a main material.

[Means for Solving Problems] The present invention capable of achieving the above object includes the following four inventions.

A first aspect of the present invention is that a heat storage material composition containing water as a main material contains at least one selected from a water repellent activated carbon, graphite and charcoal as a nucleating agent for preventing supercooling. It is a heat storage material composition having.

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

According to a third aspect of the present invention, in a heat storage material composition containing water as a main component, water-repellent graphite is contained as a nucleating agent for preventing supercooling, and a water-soluble polymer substance is contained as a thickener. It is a heat storage material composition having the gist in the point.

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 supercooled state to solidification is unstable, and the degree of supercooled changes significantly depending on the cooling temperature 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.

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

However, it was found that the supercooling prevention effect of these nucleating agents tends to gradually decrease as the number of times the heat storage material is repeatedly used increases.Especially with activated carbon, those that floated a lot on the water are used repeatedly. The fact that it began to sink with the increase in the number of times was also found. Therefore, the present inventor pays attention to the relationship with the porosity of the activated carbon, and water gradually penetrates into the micropores of the activated carbon, so that the activated carbon is completely “wetted”,
We suspected that the air existing between water and activated carbon would be purged and the nucleating agent effect would be lost.

From such a point, various investigations were carried out, assuming that coating of activated carbon with a water-repellent agent would prevent the infiltration of water and suppress the loss of the nucleating agent effect due to repeated long-term use. According to this, it was not possible to exert a particularly remarkable effect on the persistence of the nucleating agent action at room temperature, but it was found that the persistence of the nucleating agent action at repeated use at a high temperature was significantly improved, and further investigation was conducted. As a result of the repetition, the present invention has been completed.

There is no particular limitation on the chemical agent for the water repellent treatment, but typically, a silicone resin or a fluorine resin is recommended.

Regarding the amount of the nucleating agent used in the present invention, there is no significance to set a special limit depending on the kind, but in order to more reliably exhibit the effect of addition, it is 0.05 to 1.0% (meaning weight, the same below. ) Is preferable. The reason is that, as will be shown in Examples described later, if it is less than 0.05%, the effect of preventing supercooling due to the addition of a nucleating agent may be insufficient. 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 regulatory 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 only the above-mentioned three specific effects among the various carbon materials and porous materials used in the experiment were recognized, but only in the case of these three materials, reproducibility was found. 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. . And when the temperature reduction is continued in such a state,
The container that hermetically stores the heat storage material composition containing water as the main material expands in an unbalanced direction due to ice that is volume-expanded by solidification, causing the container to deform, and the heat storage material composition storage container is generally quite close. Considering that they are used in an aggregated state, 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 inconveniences. As a result, 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 an 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 keep the amount of salt added so as not to hinder the action of the nucleating agent.
It is preferably 1% or less.

Next, the present inventors considered the environment in which the heat storage material is actually used, and also examined 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 higher specific gravity than water is used as a nucleating agent, it cannot always be said that it is more effective to use it in a water tank, and in this case, it was effective regardless of the use 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.

Furthermore, the present inventors have also studied from the viewpoint that the effect of the nucleating agent will be further clarified if the nucleating agent is appropriately dispersed in water. In the case of containing treated graphite,
For example, they have found that it is effective to include a water-soluble polymer substance 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 the water-repellent 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, this is because activated carbon and charcoal are porous and have a smaller apparent specific gravity than water, and when water-repellent treatment is applied, they all float, and even if a thickener is added. It is considered that the function of dispersing the nucleating agent cannot be exerted. When a thickener is added, considering the function as a heat storage material composition, it is optimal to use graphite as a supercooling preventing nucleating agent and salt as a crystal refining agent together ( 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 As a nucleating agent for preventing supercooling, water-repellent activated carbon was used, and this nucleating agent was added to water to prepare various heat storage material 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 each heat storage material composition began to solidify was investigated.

The results are shown in Tables 1 and 2, with Table 1 showing the results in the air tank and Table 2 showing the results in the water tank. For comparison, the case where activated carbon, graphite, or charcoal was used as a nucleating agent without water-repellent treatment is also shown. The numerical values in the table indicate the solidification start temperature (° C), and
12) shows the product which has been subjected to water repellent treatment with Primatex F-12 (trade name, manufactured by Kyowa Sangyo Co., Ltd.), and (K-7) is Primatex K-7 (trade name, manufactured by Kyowa Sangyo Co., Ltd.). The water-repellent treatment is shown.

As is clear from the results shown in Tables 1 and 2, although there are some differences depending on the type of water repellent agent, it is clear that the water repellent treated nucleating agent is effective in preventing supercooling. .

Example 2 From the viewpoint that the heat storage material composition needs to be able to cope with heat fluctuations in actual operation, the present inventors have used water-repellent activated carbon (K-7), (F-12) as a nucleating agent. The heat resistance test was performed for each of the cases. That is, in the case where water-repellent activated carbon was used as a nucleating agent, the solidification start temperature (° C) of each heat storage material composition was investigated after holding at 60 ° C for a predetermined time.

The results are shown in Tables 3 and 4, and the results are 60
The coagulation start temperature (first time) when treated at ℃ × 10 to 12 hours and the coagulation start temperature (second time) when the same treatment was applied after leaving it for another day and night, and the same procedure was repeated. It shows the respective freezing start temperatures of the respective cases. In addition, in the case of activated carbon, this investigation was conducted in an air tank because it is more effective. Table 3 shows the results using activated carbon (K-7), and Table 4 shows the results using activated carbon (F-12).

As is clear from the results in Tables 3 and 4, it is understood that when heat-treated water-repellent activated carbon is used as a nucleating agent, excellent heat resistance is exhibited over a long period of time.

Next, a heat resistance test was conducted in the same procedure except that the temperature was set to 90 ° C for the same reason.

The results are shown in Tables 5 and 6. This result is the third,
As in Table 4, it is based on an air tank.

As is clear from the results shown in Tables 5 and 6, it can be seen that all of them have excellent heat resistance.

Example 3 The effect of using water-repellent activated carbon as a nucleating agent for preventing supercooling and adding various types of sodium chloride was investigated.

The results are shown in Tables 7 and 8, and although there was a difference in the effect depending on the amount of salt added, the effect of the nucleating agent was not significantly inhibited within a certain range. In any case, the volume expansion of the heat storage material composition does not locally proceed within a certain fixed amount range, and fine crystals are uniformly formed, so that the container tends to locally expand greatly. Was not recognized. In addition, Table 7 shows the result by the air tank (-10 ° C), and Table 8 shows the result by the water tank (-6 ° C). The numerical value in the table is the solidification start temperature (° C).

Comparative Example 1 The effect of using activated carbon and graphite as nucleating agents for supercooling prevention and adding polyacrylic acid as a thickening agent was 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. Even if it is added to the thickener, it does not act on the activated carbon floating 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. Then, the same investigation was conducted after the water repellent treatment of activated carbon and graphite, but the results were almost the same.

Comparative Example 2 As a nucleating agent for preventing supercooling, activated carbon (K
-7) was used, 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.

The results are shown in Tables 11 and 12, with Table 11 showing the results in the air layer and Table 12 showing the results in the water tank. This result was no different from the result of Comparative Example 1. The effect of salt was confirmed.

[Effects of the Invention] As described above, according to the present invention, the supercooling phenomenon is prevented as much as possible by including activated carbon, graphite, charcoal or the like that has been subjected to water repellent treatment as a nucleating agent for preventing supercooling. A heat storage material composition capable of being realized has been realized.

Claims (4)

[Claims] 1. A heat storage material composition containing water as a main material, which comprises at least one selected from water-repellent activated carbon, graphite and charcoal as a nucleating agent for preventing supercooling. And a heat storage material composition. 2. A heat storage material composition containing water as a main component, which contains at least one selected from water-repellent activated carbon, graphite, and charcoal as a nucleating agent for preventing supercooling, and crystallizes it. A heat storage material composition comprising a salt as an agent. 3. A heat storage material composition containing water as a main component, which contains water-repellent treated graphite as a nucleating agent for preventing supercooling and a water-soluble polymer substance as a thickening agent. A heat storage material composition comprising: 4. A heat storage material composition containing water as a main component, containing water-repellent treated graphite as a nucleating agent for preventing supercooling, and salt as a crystal refining agent, and further increasing the viscosity. A heat storage material composition comprising a water-soluble polymer substance as an agent.