JPH10330741A - Heat storage composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a heat storage material composition which can be used repeatedly for a long time without a large decrease in heat storage capacity, having a small difference between the freezing temperature and the melting temperature and suited for air conditioning. SOLUTION: This composition comprises 60-85 pts.wt. sodium sulfate decahydrate (a) and 15-40 pts.wt. at least one member (b) selected among ammonium chloride, ammonium bromide, ammonium sulfate, ammonium nitrate, sodium chloride, sodium bromide, sodium sulfate, sodium nitrate and potassium chloride (provided that when component (b) is sodium sulfate, at least one of the eight remaining components is additionally contained) and 0.1-10 pts.wt., per 100 pts.wt. heat storage component having a melting point of 5-15 deg.C, crosslinked carboxymechyl cellulose.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a heat storage material composition. More specifically, the present invention relates to an improvement of a sodium sulfate-based heat storage material composition comprising sodium sulfate decahydrate, a melting point modifier, and the like. The heat storage material composition of the present invention has a small decrease in heat storage amount even after repeated use for a long period of time, and has a small temperature difference between a solidification temperature and a melting temperature, and is suitable for cooling air conditioning.

[0002]

2. Description of the Related Art Sodium nitrate decahydrate has a melting point (32.5%).
C) is high, but has a high heat storage (60 cal / g),
Since it is a safe and inexpensive substance, many researches and developments have been made to utilize it as a heat storage material composition.

There are three major technical points for using sodium sulfate decahydrate as a heat storage material.
First, when this is used for cooling and air conditioning, the high melting point is greatly reduced and adjusted to a desired temperature. In this case, at least one inorganic salt called a melting point modifier is added to sodium sulfate decahydrate to form
Adjustment is possible in the range of up to 32 ° C. Ammonium chloride, sodium chloride, potassium chloride and the like are known as melting point regulators, and compositions having various melting points by combining these are reported.

The present inventors have also disclosed a heat storage material composition comprising sodium sulfate decahydrate / ammonium chloride / sodium chloride / ammonium sulfate and having a melting temperature of 8 to 12 ° C.
No. 48564) and a heat storage material composition comprising sodium sulfate decahydrate / ammonium chloride / sodium bromide / ammonium sulfate and having a melting temperature of 5 to 10 ° C.
188648).

[0005] The second is to prevent supercooling of sodium sulfate decahydrate. The fact that sodium tetraborate decahydrate is effective as a supercooling inhibitor for sodium sulfate decahydrate is described in M.S.
Telkes (Ind. And
Eng. Chem. , 44, 6, 1308 (195
2)).

A third object is to prevent a phenomenon called phase separation, in which the amount of stored heat is greatly reduced when sodium sulfate decahydrate repeatedly solidifies and melts. This is caused by the precipitation of anhydrous sodium sulfate, which is partially insoluble when sodium sulfate decahydrate is melted. To avoid this, a number of thickeners called phase separation inhibitors have been studied. And
As thickeners, for example, attapulgite clay (U.S. Pat. No. 3,986,969), carboxymethyl cellulose (CMC) (JP-A-58-52996),
Hydrogel crosslinked by ion (Japanese Patent Application Laid-Open No. 54-16387)
And the water-insoluble water-absorbing resins (JP-A-56-143263 and JP-A-57-82).
No. 696) has been proposed so far.

[0007]

However, when attapulgite clay or CMC is used, there is a problem that the amount of heat storage is greatly reduced when repeatedly used. In addition, when a water-insoluble water-absorbent resin is used, the amount of heat storage is small even when used repeatedly for a long period of time, and is very effective as a phase separation preventing agent, but the temperature difference between the solidification temperature and the melting temperature is high. There is a large difference between the heat storage temperature at the time of solidifying the heat storage material and the heat radiation temperature at which the heat storage material is melted and taken out, thereby deteriorating the system efficiency of the heat storage system. The object of the present invention is that there is no decrease in heat storage even when used repeatedly for a long time, and the temperature difference between the solidification temperature and the melting temperature is small
An object of the present invention is to provide a sodium sulfate-based heat storage material having a melting temperature of 5 to 15 ° C.

[0008]

Means for Solving the Problems The present inventors have made intensive studies in view of the above circumstances, and as a result, have found that the above object can be achieved by blending a specific thickener with a sodium sulfate-based heat storage material. The present invention has been completed.

That is, the gist of the present invention is that (a) sodium sulfate decahydrate: 60 to 85 parts by weight, and (b) ammonium chloride, ammonium bromide, ammonium sulfate, ammonium nitrate, sodium chloride, sodium bromide, and sodium sulfate. At least one selected from sodium nitrate and potassium chloride (however, when component (b) is sodium sulfate, at least one of the remaining eight components is included): 15 to 40 parts by weight; And melting point 5
A heat storage material composition comprising 0.1 to 10 parts by weight of crosslinked carboxymethyl cellulose with respect to 100 parts by weight of a heat storage component at 15 ° C. Hereinafter, the present invention will be described in detail.

[0010]

DETAILED DESCRIPTION OF THE INVENTION The main component of the heat storage material composition of the present invention is sodium sulfate decahydrate. Since the melting point of sodium sulfate decahydrate is 32.5 ° C., in order to adjust the melting temperature to 5 to 15 ° C., it is necessary to add a melting point modifier. Examples of the melting point modifier include ammonium salts such as ammonium chloride, ammonium bromide, ammonium sulfate and ammonium nitrate, sodium salts such as sodium chloride, sodium bromide, sodium sulfate and sodium nitrate, and potassium salts such as potassium chloride. The amount of the melting point modifier is usually 10 to 40% by weight, preferably 15 to 35 parts by weight, based on 100 parts by weight of the total amount of sodium sulfate decahydrate and the melting point modifier. If the compounding amount of the melting point modifier is less than 10 parts by weight, the melting point does not decrease to 5 to 15 ° C., and if it exceeds 40 parts by weight, the compounding amount of sodium sulfate decahydrate decreases, and the heat storage amount decreases. . The amount of sodium sulfate decahydrate is 6 parts by weight based on 100 parts by weight of the total amount of sodium sulfate decahydrate and the melting point modifier.
0 to 85 parts by weight, preferably 70 to 80 parts by weight.

A feature of the present invention resides in that crosslinked carboxymethylcellulose (hereinafter abbreviated as crosslinked CMC) is blended with a heat storage material comprising sodium sulfate decahydrate and a melting point modifier. CMC is, for example, an anionic water-soluble cellulose ether obtained by immersing sulfite pulp in an aqueous solution of sodium hydroxide to form alkali cellulose, kneading and dissolving with chloroacetate, and precipitating with methyl alcohol. Is obtained by partially cross-linking this CMC, and is characterized by being insoluble in water. For example, Aquasorb A-380 (Hercules Japan KK) and Aquasorb A-50
0 (Hercules Japan KK).

The compounding amount of the crosslinked CMC is usually 0.1 to 10 parts by weight, preferably 0.5 to 5 parts by weight, based on 100 parts by weight of the total amount of sodium sulfate decahydrate and the melting point modifier. If the amount is less than 0.1 part by weight, the effect of preventing phase separation cannot be obtained. If the amount is more than 10 parts by weight, the amount of the main component decreases, and the amount of water absorbed by the cross-linked CMC increases. It is not preferable because the amount is reduced.

[0013] A supercooling inhibitor may be added to the heat storage material composition of the present invention in order to prevent supercooling. Examples of the supercooling inhibitor include sodium tetraborate decahydrate, cryolite and the like, and preferably sodium tetraborate decahydrate is used. The amount of the supercooling inhibitor is usually 0.1 part by weight based on 100 parts by weight of the total amount of sodium sulfate decahydrate and the melting point modifier.
It is 1 to 10 parts by weight, preferably 1 to 5 parts by weight.

A preservative may be added to the heat storage material composition of the present invention in order to prevent the crosslinked CMC which is a natural polymer from being spoiled by bacteria or the like. As the preservative, any one that does not affect the melting point of the heat storage material composition and the amount of heat storage can be used, but preferably sodium benzoate,
Butylhydroxytoluene is used. The amount of the preservative is 10 in total of sodium sulfate decahydrate and melting point modifier.
The amount is usually 0.001 to 3 parts by weight, preferably 0.01 to 1 part by weight with respect to 0 parts by weight.

The heat storage material composition of the present invention has a ΔT of 0 to 4 ° C.
It is preferred that If ΔT exceeds 4 ° C., the difference between the melting temperature and the solidification temperature becomes too large, which is not practical. In addition, solidification melting, which is an index of long-term stability performance, is reduced by 50%.
It is preferable that the heat storage amount after repeating 0 times is 30 cal / ml or more.

In the heat storage material composition of the present invention, the crosslinked CM
When C is used as a phase separation inhibitor, uncrosslinked CMC
The reason for improving long-term stability performance compared to when
I'm not sure, but there are two reasons. The first is CM
Since C is crosslinked, the region where crystals of sodium sulfate decahydrate can grow is limited, and the crystals hardly grow to a certain size or more, and the crystals do not easily settle.

Another reason is that grown sodium sulfate decahydrate crystals and other precipitated insoluble components are difficult to physically settle due to the three-dimensional knitted structure formed by crosslinking. I have. It is clear from the example of the crosslinked sodium polyacrylate of Comparative Example 2 that the crosslinked water-absorbent resin shows good long-term stability performance. Also,
The reason why ΔT is smaller than when cross-linked sodium polyacrylate generally used as a water-absorbing resin is used is that the cross-linked CMC has a small water absorption capacity and a different power for retaining the absorbed water. It is possible, but not certain.

[0018]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples as long as the gist of the present invention is not exceeded.

Example 1 The components were blended at the ratios shown in Table 1, and mixed by stirring with a mixer until the crosslinked CMC was uniformly dispersed. About 180 g of the obtained sample was placed in a polyethylene resin spherical capsule having a diameter of 67 mm. The thermocouple was inserted to fill and measure the change in the center temperature of the capsule. Next, the capsule was placed in a water tank filled with a refrigerant at 13 ° C.
Then, the refrigerant in the water tank was cooled to 5 ° C. at a rate of 13 to 4 ° C./hr and kept at 5 ° C. for 8 hours. The temperature (crystallization temperature) and the solidification temperature when the supercooling of the heat storage material composition in the capsule was broken and crystallization was started were measured. Next, the refrigerant is heated to 13 ° C at a rate of 5 to 4 ° C / hr,
For 8 hours. The melting start temperature and the melting end temperature were measured. FIG. 1 shows the temperature change (solidification and melting temperature curve) at this time. ΔT was calculated according to the following equation. Table 2 shows the results.
Shown in

[0020]

ΔT = (maximum melting temperature (° C.)) − (Crystallization temperature (° C.))

ΔT is used as an index indicating practicality,
A small ΔT indicates that solidification and melting are easy and practical. Next, the long-term stability performance of the heat storage material composition was evaluated. Each component is blended at the ratio shown in Table 1,
The latent heat of fusion of the sample obtained by stirring and mixing with a mixer until the crosslinked CMC was uniformly dispersed was measured using a differential scanning calorimeter (DSC210 manufactured by Seiko Instruments Inc.). Table 2 shows the latent heat of fusion at this time as the initial heat storage.

Next, about 80 g of the heat storage material composition of Example 1
Was filled into a 50-ml hard glass screw bottle, and five samples were prepared. This sample was placed in a water tank filled with a refrigerant, and the temperature of the refrigerant was rapidly raised and lowered between −5 ° C. and 25 ° C., and solidification and melting were repeated. One cycle was performed for about 3 hours. Coagulation, melting 100 times, 200 times,
Samples repeated 300 times, 400 times and 500 times were taken out of the water tank, and the latent heat of fusion was measured with a differential scanning calorimeter. FIG. 4 shows the results. As shown in FIG.
Latent heat of fusion at the time of repetition is about 35 cal / ml
It can be seen that it is stable without change up to 500 times thereafter. From this result, even if used repeatedly for a long time, 30
It can be seen that a latent heat of fusion of cal / ml or more can be used.

Comparative Example 1 A heat storage material composition was obtained by blending the components at the ratios shown in Table 1. Various measurements were performed in the same manner as in Example 1. Table 2 shows the measurement results. FIG. 2 shows the solidification melting temperature curve, and FIG. 4 shows the results of long-term stability performance. According to FIG. 4, the heat storage amount is 1
It can be seen that when the coagulation and melting were repeated 00 times, the concentration decreased to 25 cal / ml, and was stable at about 20 cal / ml up to 500 times thereafter. From this result, when uncrosslinked carboxymethyl cellulose is used as the phase separation inhibitor,
It can be seen that the amount of latent heat of fusion that can be used when repeatedly used for a long period of time is as extremely small as about 20 cal / ml. Example 1 has 31.5 cal / m after 500 times.
l, Comparative Example 1 is 20 cal / ml, and it can be seen that the heat storage amount is increased about 1.5 times by using the cross-linked CMC.

Comparative Example 2 Each component was blended in the ratio shown in Table 1 to obtain a heat storage material composition. Various measurements were performed in the same manner as in Example 1. Table 2 shows the measurement results, FIG. 3 shows the solidification melting temperature curve, and FIG. 4 shows the results of long-term stability performance. From FIG. 3, it can be seen that Comparative Example 2 requires 9 hours from the start of cooling until the temperature of the sample becomes equal to the temperature of the refrigerant, and it is difficult to solidify for 3 hours as compared with 6 hours in Example 1. Also, the melting temperature is 9.8-11.
It can be seen that the temperature is as high as 0 ° C., and the temperature is shifted to the high temperature side by about 1 ° C. as compared with the first embodiment. Further, ΔT of Comparative Example 2 was 4.8 ° C., which was 2.4 ° C. larger than that of Example 1, and when cross-linked sodium polyacrylate was used as the phase separation preventing agent, it hardly solidified and melted. When the material composition is used in a heat storage system, it hardly solidifies, so that the heat storage time becomes very long, and it is impossible to store heat within 10 hours of midnight power, which makes practical use difficult.

Examples 2 to 5 A heat storage material composition was obtained in the same manner as in Example 1 except that the components were blended in the proportions shown in Table 1, and the measurement was performed in the same manner as in Example 1. Table 2 shows the measurement results.

[0026]

[Table 1]

[0027]

[Table 2]

Examples 6 and 7 A heat storage material composition was obtained in the same manner as in Example 1 except that the components were blended at the ratios shown in Table 3, and the measurement was performed in the same manner as in Example 1. Table 4 shows the measurement results.

[0029]

[Table 3]

[0030]

[Table 4]

[0031]

According to the heat storage material composition of the present invention, since the temperature difference between the solidification temperature and the melting temperature is small, the heat storage system can be operated near the phase change temperature, and the system efficiency of the heat storage system is improved. In addition, when the heat storage material composition of the present invention having a phase change temperature around 9 ° C. is used for a heat storage system for cooling air conditioning, it is easy to solidify, so that the system can be designed with a general-purpose chilled water refrigerator, which is a great cost advantage. There is.

[Brief description of the drawings]

FIG. 1 is a solidification melting temperature curve of Example 1.

FIG. 2 is a solidification melting temperature curve of Comparative Example 1.

FIG. 3 is a solidification melting temperature curve of Comparative Example 2.

FIG. 4 shows evaluation results of long-term stability performance of Example 1, Comparative Examples 1 and 2.

[Explanation of symbols]

 1 crystallization temperature 2 solidification temperature 3 melting start temperature 4 melting end temperature ◆ Example 1 ■ Comparative Example 1 ● Comparative Example 2

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Seiichi Kubokawa 5-34-6 Shiba, Minato-ku, Tokyo Mitsubishi Chemical Engineering Corporation

Claims (3)

[Claims] (A) sodium sulfate decahydrate: 60 to 8
5 parts by weight, and (b) at least one selected from the group consisting of ammonium chloride, ammonium bromide, ammonium sulfate, ammonium nitrate, sodium chloride, sodium bromide, sodium sulfate, sodium nitrate and potassium chloride (provided that the component (b) is sodium sulfate And further includes at least one of the remaining eight components): 15 to 40
Parts by weight and having a melting point of 5 to 15 ° C.
A heat storage material composition comprising 0.1 to 10 parts by weight of crosslinked carboxymethyl cellulose based on 0 part by weight. 2. The heat storage component 10 as a supercooling inhibitor.
0.1 parts by weight of sodium tetraborate decahydrate
The heat storage material composition according to claim 1, which is contained in an amount of 10 to 10 parts by weight. 3. The heat storage according to claim 1, wherein the preservative contains 0.001 to 3 parts by weight of sodium benzoate and / or butylhydroxytoluene based on 100 parts by weight of the heat storage component. Material composition.