JPH0641583B2 - Heat storage material - Google Patents

Description

The present invention relates to a heat storage material mainly composed of polyethylene glycol having a molecular weight of about 100 to about 7,000.

[Conventional technology]

The conventional heat storage materials mainly composed of polyethylene glycol are disclosed in JP-A-59-174683 and JP-A-60.
No. 53,585 and JP-A No. 59-140283. Polyethylene glycol has a hygroscopic property, and when it contains water, the freezing point and latent heat are lowered, and the degree of supercooling is increased, which causes inconvenience in actual use. No consideration has been given to the conventional heat storage material.

[Problems to be solved by the invention]

As described above, the conventional heat storage material mainly composed of polyethylene glycol has a hygroscopic property and thus contains water during use,
Freezing point and latent heat decrease. In addition, polyethylene glycol which does not contain water originally supercools by about 2 ° C, but when water is contained, the degree of supercooling increases to about 5 ° C. The degree of supercooling is generally smaller than that of the inorganic hydrous salt, but depending on the usage, such degree of supercooling may not be allowed. For example, polyethylene glycol # 400 has a freezing point of 5 ° C, but it is stored in a heat storage capsule and placed outside of it at 4 ° C.
In the case where solidification is carried out for a sufficient period of time while flowing the above fluid and performing heat exchange, the degree of supercooling is 2 ° C (supercooling recovery temperature is 3
Even at (° C.), the heat storage material cannot be solidified.

An object of the present invention is to provide a heat storage material capable of preventing a decrease in freezing point and a decrease in latent heat due to moisture absorption and a reduction in supercooling degree.

[Means for solving problems]

The above-mentioned purpose is anhydrous Na ₂ CO ₃ , anhydrous K ₂ CO ₃ , anhydrous Mg.
This is accomplished by adding one or more substances from the group consisting of CO ₃ , anhydrous Li ₂ CO ₃ , and zeolites. That is, the feature of the present invention is to use an anhydrous inorganic substance which is difficult to melt in polyethylene glycol.

[Action]

The above substances adsorb the water contained in polyethylene glycol, prevent the freezing point of the heat storage material from lowering, prevent the latent heat from lowering, facilitate the crystallization of polyethylene glycol itself, and reduce the degree of supercooling to 0.5 ° C or less. Has a suppressing effect.

〔Example〕

[Example 1] 100 g of polyethylene glycol # 400 was placed in a polyethylene container with a lid, 1 g of anhydrous Na ₂ CO ₃ was added, and a coagulation-melting heat cycle test was performed using cold water and warm water. The initial freezing point of this heat storage material was 5 ° C, and the latent heat was 36 Ca / g. The degree of supercooling was 0.5 ° C. or less, but no change was observed after 1000 heat cycles.

Example 2 100 g of polyethylene glycol # 6000 was placed in a polyethylene container with a lid, and anhydrous MgCO ₃ 0.1 g,
0.1 g of zeolite was added, and a heat cycle test of coagulation-melting was performed using cold water and hot water. The initial freezing point of this heat storage material is 56 ° C, the latent heat is 46 Ca / g, and the degree of supercooling is 0.
Although the temperature was 5 ° C. or lower, no change was observed even after 1000 heat cycles.

Example 3 100 g of polyethylene glycol # 6000 was placed in a polyethylene container with a lid, and anhydrous K ₂ CO ₃ 0.1 g,
Anhydrous La ₂ CO ₃ 0.1 g and zeolite 0.1 g were added, and a heat cycle test of coagulation-melting was performed using cold water and warm water. The initial freezing point of this heat storage material is 56 ° C and the latent heat is 46C.
The degree of a / g and the degree of supercooling were 0.5 ° C. or less, but no change was observed after 1000 heat cycles.

Polyethylene glycol # 600, # 1000, # 15
The same test was conducted for 40 and the like, but the same effect as that of the above-mentioned example was obtained.

Addition amount of additive materials such as Na ₂ CO ₃ and K ₂ CO ₃ is 0.01% by weight
It is effective even in the degree, and the more it is added, the more effective
If it is too large, the heat storage density of the heat storage material will be reduced, so the upper limit is 1.
It is better to set it to about 0% by weight.

[Comparative Example 1] 100 g of polyethylene glycol # 400 was placed in a polyethylene container with a lid, and a coagulation-melting heat cycle test was performed using cold water and warm water without adding any additive. The initial freezing point of this heat storage material is 5 ° C and the latent heat is 36
Ca / g, degree of supercooling is 2 ° C (supercooling recovery temperature is 3 ° C)
However, after 1000 heat cycles, the freezing point decreased to 3 ° C, the latent heat decreased to 28Ca / g, and the degree of supercooling was 5 ° C.
(The supercooling recovery temperature is −2 ° C.). During the heat cycle, external moisture-containing air has entered the container through the lid.

[Comparative Example 2] 100 g of polyethylene glycol # 6000 was placed in a nylon bag, and a heat cycle test of coagulation-melting was performed using cold water and warm water without adding any additive. The initial freezing point of this heat storage material is 56 ° C and the latent heat is 46 Ca /
g, supercooling degree was 3 ° C. (supercooling recovery temperature was 53 ° C.), but the freezing point was 52 after 1000 heat cycles.
C., latent heat was 37 Ca / g, and supercooling degree was 6 ° C. (supercooling recovery temperature was 46 ° C.). This is because moisture-containing air was introduced into the inside of the nylon bag from the defective part of the pinhole and sealing part during the heat cycle.

[Comparative Example 3] 100 g of polyethylene glycol # 6000 was placed in an Al container, and inorganic hydrate Na ₂ C was used as an additive.
After adding 1 g of O ₃ .10H ₂ O, the container was completely sealed by welding. The initial freezing point of this heat storage material was 56 ° C, the latent heat was 46Ca / g, and the degree of supercooling was 3 ° C (the supercooling recovery temperature was 53 ° C), but after 1000 heat cycles, the freezing point was 53 ° C and the latent heat was The temperature was 39 Ca / g and the degree of supercooling was changed to 5 ° C (the supercooling recovery temperature was 48 ° C). The hydrate was found to be ineffective.

〔The invention's effect〕

As described above, according to the present invention, the freezing point and latent heat of the heat storage material mainly composed of polyethylene glycol are not lowered, and the degree of supercooling is suppressed to be small, which facilitates the thermal design of the heat storage device.

[Brief description of drawings]

FIG. 1 shows the coagulation characteristics of Example 1 and Comparative Example 1 using polyethylene glycol # 400, and FIG. 2 shows the coagulation characteristics of Example 2 and Comparative Example 2 using polyethylene glycol # 6000.

Claims (2)

[Claims] 1. Addition of one or more substances selected from the group consisting of anhydrous Na ₂ CO ₃ , anhydrous K ₂ CO ₃ , anhydrous MgCO ₃ , anhydrous Li ₂ CO ₃ and zeolite as an additive to polyethylene glycol. Heat storage material characterized by. 2. The heat storage material according to claim 1, wherein the addition amount of the addition material is 0.01 to 10% by weight.