JPH021194B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat storage material mainly composed of sodium acetate trihydrate.

In general, heat storage materials that utilize the sensible heat of substances and those that utilize latent heat are known. Heat storage materials that use latent heat have a larger amount of heat storage per unit weight or unit volume than heat storage materials that use sensible heat, and only a small amount is required to store the required amount of heat. It becomes possible to downsize the heat storage device. In addition, a heat storage material that uses latent heat has the characteristic that unlike a heat storage material that uses sensible heat, the temperature does not drop with heat radiation, and instead radiates heat at a constant temperature at a transition point. In particular, heat storage materials that utilize the latent heat of fusion of inorganic hydrates are known to have a large amount of heat storage per unit volume.

By the way, sodium acetate trihydrate (NaCH ₃ COO 3H ₂ O, melting point approximately 58°C) has traditionally had a high latent heat of 63 cal/g among inorganic hydrates, and has been considered a promising heat storage material for heating, for example. . but
It was recently discovered that when NaCH ₃ COO・3H ₂ O is stored in a heat storage tank and heat storage and heat release are repeated, the amount of heat storage decreases significantly as the process is repeated. This is considered to be due to a phase separation phenomenon. For that purpose, 50g of NaCH ₃ COO・3H ₂ O
Crystal nucleation material for NaCH ₃ COO・3H ₂ O Na ₄ P ₂ O ₇・
Store 0.2g of 10H ₂ O in a graduated cylinder with a stopper, place the graduated cylinder in a water bath,
Heating and cooling were repeated between 35℃ and 70℃, and heat storage and heat release were repeated. Then, changes in the heat storage material at that time were observed.

Figure 1A shows the appearance of the heat storage material at 35°C for the 5th test, Figure B for the 20th test, and Figure C for the 50th test. In the figure, 1 is a graduated cylinder, 2 is a stopper of the graduated cylinder, 3 is a solid phase part, and 4 is a liquid phase part. As is clear from this figure,
Part of the liquid phase of NaCH ₃ COO 3H ₂ O remains unsolidified from the 5th solidification, and the volume of the liquid phase increases as heat storage and heat radiation are repeated, until the 50th solidification. It can be seen that approximately 25% by volume remains in the liquid phase during solidification. Therefore, as a matter of course, the amount of heat storage decreases by the amount of the remaining liquid phase.

This phase separation phenomenon is shown in Figure 2.
Consider using the binary phase diagram of the NaCH ₃ COO-H ₂ O system. In this figure, NaCH ₃ COO 60.35% by weight
and H ₂ O39.65% by weight,
Corresponds to NaCH ₃ COO・3H ₂ O composition. So,
When a crystal of NaCH ₃ COO・3H ₂ O is placed in a container and heated, it melts at 58℃. When all melting is complete, the result is a 58% by weight saturated aqueous solution of NaCH ₃ COO and anhydrous NaCH ₃ COO. by the way,
The specific gravity of a 58% by weight aqueous solution of NaCH ₃ COO at this temperature is approximately 1.3, while the specific gravity of anhydrous NaCH ₃ COO is approximately
1.5, so anhydrous NaCH ₃ COO is
NaCH ₃ will be precipitated into a saturated aqueous solution of COO. However, during the initial stage, the particles of anhydrous NaCH ₃ COO are small and acicular in shape, so they remain retained in the container to some extent. Therefore, when the temperature is maintained at around 70°C for a certain period of time and then cooled again, heat is released while crystals of NaCH ₃ COO.3H ₂ O are precipitated. At that time, contrary to the time of melting,
Anhydrous NaCH ₃ COO.crystals and a saturated aqueous solution of NaCH ₃ COO must react to form NaCH ₃ COO.3H ₂ O crystals. If a thin film of NaCH ₃ COO・3H ₂ O is formed around the anhydrous NaCH ₃ COO particles, H ₂ O cannot easily penetrate to the center, so the anhydrous NaCH ₃ COO and
Anhydrous by reaction with a saturated aqueous solution of NaCH ₃ COO
It takes an extremely long time for all NaCH ₃ COO to change to NaCH ₃ COO.3H ₂ O. Therefore, in reality, anhydrous NaCH ₃ COO usually remains at the bottom of the container and a saturated aqueous solution of NaCH ₃ COO remains at the top of the container. Moreover, by repeating heating and cooling, NaCH ₃ COO・
When 3H ₂ O is melted, the particle size of anhydrous NaCH ₃ COO increases, and these particles solidify into a large lump. If this happens, even if it is cooled again, only the surface of the lump of anhydrous NaCH ₃ COO will change to NaCH ₃ COO・3H ₂ O, and most of the anhydrous NaCH COO will change to NaCH ₃ COO・3H ₂ O. It remains as it is. Therefore, as a matter of course, NaCH ₃ COO is reduced by the remaining anhydrous NaCH ₃ COO.
A saturated aqueous solution of is also left behind, and the amount of heat storage is greatly reduced compared to the initial stage. The decrease in heat storage due to this phase separation phenomenon is
This has been a major problem when putting NaCH ₃ COO/3H ₂ O into practical use as a heat storage material.

The present invention aims to provide a heat storage material that is inexpensive and has a large amount of heat storage per unit weight and volume by preventing a decrease in the amount of heat storage due to phase separation. The main features of the present invention are as follows:
The main component is NaCH ₃ COO.3H ₂ O, and calcium tartrate (CaC ₄ H ₄ O ₆ ) is added to prevent a decrease in heat storage due to phase separation.
The amount of CaC ₄ H ₄ O ₆ added is NaCH ₃ COO・3H ₂ O 100
The range of 0.01 to 40 parts by weight is good;
CaC ₄ H ₄ O ₆ may be added in the form of CaC ₄ H ₄ O ₆ .4H ₂ O.

In the same graduated cylinder with a stopper as shown in Figure 1, add 50 g of NaCH ₃ COO・3H ₂ O and NaCH ₃ COO・
Na ₄ P ₂ O ₇・10H ₂ O, which is a crystal nucleation material for 3H ₂ O, is
0.2 g and 50 mg of CaC ₄ H ₄ O ₆ were stored therein. In the same manner as described above, it was placed in a water bath and heated and cooled repeatedly between 35°C and 70°C, thereby repeatedly accumulating and dissipating heat. The changes in the heat storage material at that time were observed. The fifth time is shown in Figure 3 A, and the fifth time is shown in Figure 3 B.
Figure C shows the appearance of the 20th test at 35°C, and Figure C shows the appearance of the 50th test at 35°C. In this way, unlike Figure 1 where CaC ₄ H ₄ O ₆ was not added, in this case, even if heat storage and heat radiation were repeated 50 times,
There is no liquid phase at all in the heat dissipation state at 35°C, and there is almost no decrease in the amount of heat storage.

In this way, NaCH ₃ COO・3H ₂ O to CaC ₄ H ₄ O ₆
By adding and containing, it is possible to prevent a decrease in heat storage amount due to phase separation.

This is the cause of the action of CaC ₄ H ₄ O ₆ .
CaC ₄ H ₄ O ₆ partially dissolves in the melt of NaCH ₃ COO 3H ₂ O and dissociates into Ca ²⁺ ions and C ₄ H ₄ O ₆ ^2- ions,
Due to the action of these ions, anhydrous
It is thought that this may prevent the particle size of the NaCH ₃ COO particles from increasing or prevent the particles from coagulating with each other.

By the way, the amount of CaC ₄ H ₄ O ₆ added is
Approximately 0.01 part by weight per 100 parts by weight of NaCH ₃ COO・3H ₂ O is sufficiently effective. However, when the amount was about 0.001 parts by weight, no obvious effect of preventing phase separation could be obtained. Conversely, 0.01 parts by weight or more of CaC ₄ H ₄ O ₆
Even if added, the effect of preventing the decrease in latent heat due to phase separation remains unchanged. Adding too much CaC ₄ H ₄ O ₆ will result in a decrease in the amount of heat storage as a heat storage material. Therefore, in practical terms, the mixing ratio of CaC ₄ H ₄ O ₆ to 100 parts by weight of NaCH ₃ COO・3H ₂ O is
A range of 0.01 to 40 parts by weight is considered desirable.

Note that instead of CaC ₄ H ₄ O ₆ , NaCH ₃ COO・
CaC ₄ H 4 O ₆ 4H ₂ BO, which provides Ca ²⁺ ions and _{C 4} H ₄ O ₆ ^2- ions in the 3H ₂ O melt, may also be used, and furthermore, Ca ²⁺ ions and C ₄ H ₄ Of course, separate substances providing O ₆ ^2- ions may also be added.

As described above, the present invention provides NaCH ₃ COO・3H ₂ O
The purpose is to add CaC ₄ H ₄ O ₆ to provide a heat storage material that prevents a decrease in the amount of heat storage due to phase separation.
Na ₄ P ₂ O ₇ , Na ₄ P ₂ O ₇・10H ₂ O, Na ₃ HP ₂ O ₇ ,
Using crystal nucleation materials such as Na ₂ H ₂ P ₂ O ₇ , NaH ₃ P ₂ O ₇ , CO(NH ₂ ) ₂ , NH ₂ CH ₂ COOH, CH ₃
Additives such as solidification heat dissipation temperature regulators such as (NH ₂ )CHCOOH may be added. as needed,
_{The composition may be changed by adding H 2 O} or NaCH ₃ COO to NaCH 3 COO.3H ₂ O.

Examples of the present invention and comparative examples thereof will be described below.

Example 1 1000 g of NaCH ₃ COO・3H ₂ O and Na ₄ P ₂ O ₇・
_10H2O1g , _CaC4H4O6・_4H2O1g were stored in a heat storage tank 5 equipped with a heat exchanger as shown in _Fig . ₄ , and water at 70℃ and 20℃ was used as the heat medium for heat exchange. .

In the figure, 6 is a heat insulating material, 7 is a thermocouple for measuring the inlet temperature of the heat medium, 8 is a thermocouple for measuring the outlet temperature of the heat medium, and 9 is a heat exchanger for passing the heat medium. 10 is a heat storage material, and 11 is a flow meter.

Measure the inlet temperature, outlet temperature, and heat medium flow rate,
The amount of heat stored in the heat storage material in the container was determined using the following formula.

Q=∫(Tin−Tout)・V・dt Here, Tin is the inlet temperature of the heating medium, and Tout is
This is the exit temperature after heat is transferred to the heat storage material. V is the flow rate of the heat medium per unit time.

Heat dissipation was performed by flowing a heating medium at 20°C. In this way, the amount of heat stored was measured 100 times in succession by repeatedly flowing a heating medium at 70°C and 20°C, and the amount of change from the initial amount of stored heat was determined. The state of the change is shown in Figure 5. In this figure, the horizontal axis shows heat storage,
The number of times heat radiation is repeated is plotted on the vertical axis as the ratio of the amount of heat stored each time to the amount of heat stored the first time. From this, it can be seen that the amount of heat storage hardly changes due to the repetition of heat storage and heat radiation in this example, and it is an excellent heat storage material.

When the melting point and latent heat of the heat storage material of this example were measured, it was found that the melting point was 58.3° C. and 63 cal/g, which is almost the same as NaCH ₃ COO.3H ₂ O.

Example 2 800g of NaCH ₃ COO・3H ₂ O and Na ₄ P ₂ O ₇・
1g of 10H ₂ O and 200g of CaC ₄ H ₄ H ₄ O ₆ were stored in the same container as in Example 1, and the change in heat storage amount when heat storage and heat radiation were repeated was determined by the same operation as in Example 1. Ta. The results are shown in FIG. This results in
It can be seen that the amount of heat storage hardly changes due to the repetition of heat storage and heat radiation in this example, and it is an excellent heat storage material.

When the melting point and latent heat of the heat storage material of this example were measured, the melting point was 58.3℃, and the latent heat was
It had a sufficient function as a heat storage material, with a value of 50 cal/g.

Comparative example NaCH ₃ COO・3H ₂ O 1000g and Na ₄ P ₂ O ₇・
1g of 10H ₂ O was stored in the same container as in Example 1, and the same operation as in Example 1 was performed to determine the change in heat storage amount when heat storage and heat radiation were repeated. The results are shown in FIG. This results in NaCH ₃ COO・3H ₂ O.
If CaC ₄ H ₄ O ₆ is not added, the amount of heat storage will decrease as heat storage and heat radiation are repeated, and when repeated 100 times, the amount of heat storage will decrease to about 70% of the initial amount, making it impractical to use as it is. It turned out that it could not be used.

As _is clear from the above implementation and comparative examples, _the heat storage material of the present invention
Since it is a mixture containing CaC ₄ H ₄ O ₆ , the amount of heat storage hardly decreases through repeated heat storage and heat release, making it inexpensive and with a large amount of heat storage.
Therefore, the heat storage material of the present invention can be applied not only to heat storage devices for air conditioning, but also to all areas that utilize heat storage, such as heat storage type heat insulators.

[Brief explanation of drawings]

Figure 1 shows NaCH ₃ COO・3H ₂ O and Na ₄ P ₂ O ₇・
When a heat storage material made of 10H ₂ O is radiated and cooled between 35℃ and 70℃, and heat storage and heat radiation are repeated,
Figure A shows the changes in the heat storage material.
Figure B shows the appearance at 35°C for the 20th test, and Figure C shows the appearance at 35°C for the 50th test. Figure 2 is
It is a phase diagram of the NaCH ₃ COO·H ₂ O system. Figure 3 is
NaCH ₃ COO・3H ₂ O and Na ₄ P ₂ O ₇・10H ₂ O
The heat storage material of the present invention, which is composed of CaC ₄ H ₄ O ₆ , shows the changes when the heat storage material of the present invention is subjected to the same operation as the heat storage material shown in FIG. The 20th test and C in the same figure show the external appearance of the heat storage material of this example at 35° C. in the 50th test, respectively. FIG. 4 is a cross-sectional view of the device used to measure the amount of heat storage. FIGS. 5 and 6 show changes in the amount of heat storage when heat storage and heat radiation are continuously repeated 100 times for an example of the heat storage material according to the present invention. FIG. 7 shows the change in heat storage amount when heat storage and heat radiation were repeated 100 times in a row for the heat storage material of the comparative example.

Claims (1)

[Claims] 1. Sodium acetate trihydrate (NaCH ₃ COO.
3H ₂ O) and calcium tartrate (CaC ₄ H ₄ O ₆ ). 2 For 100 parts by weight of sodium acetate trihydrate,
The heat storage material according to claim 1, wherein the calcium tartrate is 0.01 to 40 parts by weight. 3. The heat storage material according to claim 1, wherein the calcium tartrate is calcium tartrate tetrahydrate (CaC ₄ H ₄ O ₆ .4H ₂ O).