JPH0450358B2 - - Google Patents

Description

[Detailed description of the invention]

[Field of Industrial Application] The present invention relates to a heat storage material composition containing K ₂ HPO ₄ .6H ₂ O as a main component, in which an appropriate amount of a nucleating agent is added to prevent supercooling. . [Prior art] Conventionally, heat storage material compositions used for low-temperature waste heat storage, air conditioning (cooling), chemical heat pumps, greenhouse heating, etc. have a freezing point near 30°C.
The main ingredients used are CaCl ₂ .6H ₂ O and Na ₂ SO ₄ .6H ₂ O (mirabilite), and the phase change point is adjusted to, for example, around room temperature by adding a freezing point regulator. [Problems to be Solved by the Invention] However, the heat storage material composition described above is a complex mixture system that significantly impairs the latent heat inherent in CaCl ₂ 6H ₂ O and Glauber's salt, and the amount of latent heat available per unit weight is It has become a small thing. Furthermore, the above-mentioned heat storage material compositions often undergo denaturation during repeated solidification and melting, resulting in a shift in solidification point, and have the disadvantage that they cannot withstand repeated use over a long period of time. Therefore, the present inventors sought to provide a heat storage material composition that is a single component or a composition, has a large amount of latent heat at a predetermined phase change temperature, and does not deteriorate in performance even after repeated use. I have conducted various research. As a result, as shown in Table 1, we focused on K ₂ HPO _{4.6H 2} O, which has a large amount of latent heat.

[Table] That is, K ₂ HPO ₄・6H ₂ O has a phase change point at 14℃,
When the temperature rises, the solid begins to melt at 14°C, and at the same time absorbs heat from the environment and becomes a liquid state. On the other hand, when the temperature drops, the liquid crystallizes and generates heat, becoming a solid state. However, K ₂ HPO ₄ .6H ₂ O has the characteristic that it is difficult to crystallize compared to CaCl ₂ .6H ₂ O, and when used as a heat storage material, a remarkable supercooling phenomenon occurs, causing various problems in its practical use. In other words, this supercooling phenomenon is a phenomenon in which during the cooling process of a liquid phase substance, the change from liquid phase to solid phase does not occur even after passing the freezing point, and solidification begins only after the temperature drops considerably below the freezing point. Therefore, the temperature at which latent heat of solidification should be generated, that is, the freezing point, is unspecified, which is a fatal defect for a heat storage material for maintaining a specific temperature range. The present invention has been made in view of these circumstances, and its purpose is to take advantage of the high latent heat properties of K ₂ HPO ₄ .6H ₂ O while solving the above-mentioned practical problems. [Means for Solving the Problems] However, the heat storage material composition of the present invention that achieves the above object has K ₂ HPO ₄ .6H ₂ O as a main component, and Ca ₂ P ₂ as a nucleating agent to prevent supercooling. O ₇ , Ca ₃ (PO ₄ ) ₂・2H ₂ O,
The gist is that it contains one or more types selected from the group consisting of _{Zn 3} (PO ₄ ) 2.4H ₂ O. [Function] When a heat storage material composition consisting essentially of only K ₂ HPO _{4.6H 2} O is lowered from a molten state, it does not solidify even after passing its freezing point of about 14°C, and as shown in Figure 1. As shown by the broken line, coagulation begins rapidly when the temperature reaches, for example, about 10°C. When the solidification is further progressed, if vibration is applied, a portion of the material re-melts and once the temperature rises, it solidifies again. As described above, the state of solidification progress from supercooling is unstable, and the degree of supercooling changes significantly depending on the temperature drop and disturbance of the melt, so it is impossible to specify the temperature at which latent heat is generated. Temperature control according to the usage temperature cannot help but be inaccurate. Therefore, in the present invention, in order to prevent the melt of K ₂ HPO ₄ .6H ₂ O from becoming supercooled, it was decided to add a nucleating agent that promotes crystallization. That is, when about 2% by weight of Ca ₂ P ₂ O ₇ was contained as a nucleating agent for preventing supercooling, the supercooling phenomenon was significantly alleviated and the temperature could be suppressed to about 0.5° C., as shown by the solid line in FIG. As a nucleating agent for supercooling prevention that exhibits the above function, as a result of various studies, in addition to Ca ₂ P ₂ O ₇ , Ca ₃ (PO ₄ ) ₂ .
It was found that 2H ₂ O and Zn ₃ (PO ₄ ) ₂・4H ₂ O are effective. By adding one type or a combination of two or more of these nucleating agents, supercooling of K ₂ HPO ₄ .6H ₂ O can be prevented. There is no particular restriction on the amount of the nucleating agent added, but in order to more reliably exhibit the effect of the addition, it may be added in a range of 1 to 20%. The reason for this is that if it is less than 1%, the supercooling prevention effect is insufficient, as shown in the examples below, and on the other hand, if it is added in excess of 20%, no further effect can be expected. . [Example] Ca ₂ P ₂ O ₇ , Ca ₃ as a nucleating agent in K ₂ HPO ₄ 6H ₂ O
(PO ₄ ) ₂・2H ₂ O, Zn ₃ (PO ₄ ) ₂・4H ₂ O as shown in Tables 2 to 4, each contained singly or in combination of two or more selected from these. The supercooling suppression effect in this case is shown in Figs. The experimental results were shown in terms of the degree of supercooling when melting and solidifying were repeated using each heat storage material composition.

【table】

【table】

[Table] As shown in Figure 2, when Ca ₂ P ₂ O ₇ is used alone as a nucleating agent, when the amount added is 0.5% (No.
Although 1) has an effect of suppressing supercooling, the effect varies, and the addition effect is insufficient overall. On the other hand, in Nos. 2 and 3 in which the addition amount was 1.0% or more, a sufficient supercooling suppressing effect could be obtained, and even if the number of repetitions increased, the same effect could be stably obtained. As shown in Figure 3, the nucleating agent is Ca ₃ (PO ₄ ) ₂ ,
Zn ₃ (PO ₄ ) ₂・4H ₂ O (single)
It was possible to obtain the same supercooling suppressing effect as Ca ₂ P ₂ O ₇ . Furthermore, the supercooling suppressing effect when two types of the above-mentioned nucleating agents were used in combination was as shown in FIG. 4, and the same supercooling suppressing effect as described above could be stably obtained. As shown in the above example, by adding an appropriate amount of a nucleating agent, it is possible to prevent the occurrence of supercooling phenomenon, which was a drawback of the main component K ₂ HPO ₄ 6H ₂ O, and reduce the latent heat per unit weight. Large amount of K ₂ HPO ₄・
It has become possible to effectively utilize the features of 6H ₂ O. That is, it has become possible to provide a heat storage material composition that generates a large amount of heat (or absorbs heat) at the usage temperature and exhibits little change in performance even after repeated melting and solidification. The heat storage material composition according to the present invention is as described above, but when putting it into practical use as a heat storage material, it is customary to use an appropriate amount of a thickener or a freezing point regulator as necessary. It is of course permissible to add these subcomponents as appropriate. Even when these subcomponents are added, the heat storage material composition of the present invention does not cause a decrease in the amount of latent heat or a significant supercooling phenomenon. Below, the composition, freezing point, and degree of supercooling (average value when repeated 10 times) of typical heat storage material compositions of the present invention containing these subcomponents are also listed. (A) Main component (K ₂ HPO ₄ 6H ₂ O): Residual freezing point regulator (K ₂ HPO ₄ ): 10% Nucleating agent (Ca ₂ P ₂ O ₇ ): 1% Thickener (ultrafine powder silica) ): 2% Freezing point: 5°C, degree of supercooling: 1.0°C [Effects of the invention] The present invention is configured as described above, and the nucleating agent is added to the main component K ₂ HPO ₄ 6H ₂ O. By doing so, we succeeded in eliminating the supercooling phenomenon that was a drawback of K ₂ HPO ₄ 6H ₂ O, and we were able to take advantage of its feature of high latent heat per unit weight. In this way, a composition containing K ₂ HPO ₄ .6H ₂ O, which was initially thought to be difficult to put into practical use as a heat storage material, could be made into a composition with excellent heat storage performance.

[Brief explanation of the drawing]

Figure 1 is a graph showing basic experimental data, Figure 2-
FIG. 4 is a graph showing the degree of supercooling of the heat storage material composition according to the present invention.

Claims (1)

[Claims] 1 Contains K ₂ HPO ₄・6H ₂ O as a main component, and uses Ca ₂ P ₂ O ₇ , Ca ₃ (PO ₄ ) ₂・2H ₂ O, as a nucleating agent to prevent supercooling.
A heat storage material composition comprising one or more selected from the group consisting of Zn ₃ (PO ₄ ) ₂ and 4H ₂ .