JPH11166176A - Latent-heat storage composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a latent-heat storage compsn. which has an m.p./solidifying point in the range of 70-100 deg.C and can be used for keeping heating apparatuses warm and as a heat storage material for waste heat recovery systems and air-conditioning and heating systems. SOLUTION: This compsn. is prepd. by mixing 100 pts.wt. magnesium chloride hydrate represented by the formula: MgCl2 .nH2 O (wherein n is 6.1-10) with 1-20 pts.wt. ethylene glycol, 0.1-20 pts.wt. at least one salt selected esp. from lithium chloride, potassium chloride, and sodium chloride, 0.1-20 pts.wt. strontium chloride and/or barium chloride, pref. their mixture in a wt. ratio of (9/1)-(1/9), and 0.1-10 pts.wt. sepiolite.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a latent heat storage material. More specifically, latent heat storage is useful for passive energy, mainly in the temperature range (around 70 to 100 ° C) suitable for systems such as recovery of unused waste heat (heat storage tank) and electric appliances that require heating and heat retention. Material composition.

[0002]

2. Description of the Related Art In the process of melting and solidification, a substance which releases a large amount of latent heat and heat at a certain temperature stores this latent heat without a temperature change, and releases or heats this latent heat without a temperature change when necessary. Since the mechanism of absorbing heat can be effectively used, it is widely used as a latent heat storage material, such as cooling and heating, waste heat, passive energy recovery, heat storage for use, and use of nighttime power.

[0003] Various inorganic hydrate salts and paraffins are known. Inorganic hydrate salts are excellent as a heat storage material in terms of calorific value and thermal conductivity and density in their specificity.
The hydrate separates into two phases of inorganic anhydride crystals and a saturated aqueous solution thereof during melting / solidification. When this phenomenon is left untreated, hydrated salts are not generated even when cooled (phase separation), and even when the temperature is lowered, there is no solidification at the freezing point, so that the heat of latent heat does not occur (supercooling). It lacks stability and reliability as a heat storage material. In order to function as a latent heat storage material, it is necessary to make a profit adjustment so that its melting point and freezing point work effectively in the temperature range used.

The melting point of magnesium chloride hydrate is 117-120 ° C. at a constant pressure, and the heat of fusion is 170 joules /
g. The latent heat storage material is a material in a medium temperature range, but is generally not suitable for use in keeping the temperature (around 100 ° C.) because its melting point is too high. Further, there is a disadvantage that supercooling and phase separation easily occur.

In order to make inorganic hydrates such as magnesium chloride hydrate a heat storage material suitable for use by applying the melting point and the transition point of freezing point, ethylene glycol or the like having a shared melting point lower than that of magnesium chloride is used. A temperature drop due to the addition of chloride is preferred. In addition, sodium chloride and potassium chloride are economically used as chlorides, but the drop rate is small when used alone. Ethylene glycol is effective, but has been found to increase supercooling. Combined use with salts is effective in lowering the melting point.

That is, when the amount of ethylene glycol added is relatively small, the effect of lowering the melting point can be seen in accordance with the amount of addition. However, when the amount added is large, the melting point / solidification point drops extremely or crystal formation is difficult. And no longer coagulates.
Also, when the amount of ethylene glycol exceeds 10% by weight of magnesium chloride / hydrate and the additive is further increased, the melting point and the freezing point become extremely slow as general properties of the hydrated salt, and it is easily supercooled, and the heat storage density And the effect of the present invention as a latent heat storage material in the target temperature range is reduced. For these reasons, the amount of addition is in the range of 1 to 20% by weight.

[0007] Accordingly, the present invention provides a method for determining a predetermined temperature level (70 to 70).
As a latent heat storage material that can be used to operate at about 100 ° C.), magnesium chloride alone cannot be used, and a latent heat storage material made of such a substance that can effectively use latent heat in a use temperature range has not been obtained.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a latent heat storage material mainly composed of magnesium chloride hydrate which can be used in a temperature range suitable for storing waste heat and energy generated during combustion or heating for a certain purpose. As a result of the examination, by adding strontium chloride and / or barium chloride alone or in combination of ethylene glycol and lithium chloride, potassium chloride, and sodium chloride alone or in a mixture, even if ethylene glycol is added by 10% by weight or more,
A latent heat storage material composition whose melting point / freezing point can be adjusted without any trouble, can be lowered to a temperature suitable for use, and can be used in a waste heat heat storage system, a hot water system heat storage tank utilizing solar heat, and the like.

[0009]

That is, the present invention relates to 100 parts by weight of magnesium chloride hydrate having a composition of the general formula MgCL ₂ .nH ₂ O (n is 6.1 to 10), and ethylene glycol 1 to 20 parts by weight. Part by weight, 0.1 to 20 parts by weight of a single or a mixture of lithium chloride, potassium chloride, and sodium chloride as salts, and 0.1 to 20 parts by weight of strontium chloride and / or barium chloride are mixed. It is.

In a preferred embodiment of the present invention, a mixture having a strontium chloride / barium chloride mixture ratio (weight) of 9/1 to 1/9 is used as the strontium chloride and / or barium chloride.

The present invention further includes a composition in which 0.1 to 10 parts by weight of sepiolite is added as a phase separation preventing material to the heat storage material composition.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Magnesium chloride hydrate used as a main component of the latent heat storage material of the present invention has a chemical formula of MgCL
Represented by ₂ · 6H ₂ O, the so-called magnesium chloride hydrate, and include those the amount of crystal water than was slightly increased or _{decreased, MgCL 2 · nH 2 O (} n is from 6.1 to 10, preferably Is a magnesium chloride hydrate having a composition of 6.5 to 8). n is a number corresponding to the number of moles of water of crystallization of the hydrate, and when n = 6, it is magnesium chloride hexahydrate. Such magnesium chloride hydrate can be prepared by adding water to anhydrous magnesium chloride or magnesium chloride hexahydrate.

[0013] The temperature-lowering substances include ammonium chloride, ammonium nitrate, ammonium sulfate, urea, ethylene glycol and salts (lithium chloride, potassium chloride,
Sodium chloride) and the like, but ethylene glycol alone or in combination with a plurality of salts is preferable since the melting point / freezing point is lowered and the economic effect is large.

Strontium chloride and barium chloride can be used alone or in combination.
In particular, strontium chloride and barium chloride are mixed with a strontium chloride / barium chloride mixture ratio (weight ratio) of 9/1 to 1/1.
The use of a mixture of 9, especially 3/1 to 1/1, is preferable because the effect can be obtained with a smaller amount of addition.

In the present invention, the amount of ethylene glycol added to magnesium chloride hydrate as the main ingredient is 1 to 20 parts by weight, preferably 3 to 15 parts by weight of ethylene glycol per 100 parts by weight of magnesium chloride hydrate. If the amount is too large, the melting point / solidification point is too low, which is not practical. On the other hand, if the addition amount is small, a latent heat storage material in the temperature range as intended by the present invention cannot be obtained. Within the above range, the amount of addition can be arbitrarily selected depending on the temperature range in which the latent heat storage material is used.

By increasing the use of ethylene glycol alone or in combination with salts, the endothermic onset temperature falls according to an appropriate amount, and the melting point melts within the temperature range of the present invention, and is within about 3 ° C. or less from the melting temperature. In the present invention, by adding strontium chloride and / or barium chloride, the effect of adding such a large amount of ethylene glycol can be exerted, and the temperature can be adjusted to a desired value. For example, 1.5 parts by weight of strontium chloride,
In the case of adding 1.1 parts by weight of barium chloride (all based on 100 parts by weight of the main ingredient), ethylene glycol is added in an amount of 20%.
The addition can reduce the melting point / solidification point to 80 ° C. or less, so that a latent heat storage material in a desired use range can be obtained, and the system can be sufficiently supported.

The melting point / freezing point due to the addition of ethylene glycol is influenced by the ratio of the amount of water of crystallization of the magnesium chloride hydrate used. Pure magnesium chloride ・ 6
Using a hydrate having a large amount of water of crystallization rather than a hydrate can change the transition point such as melting point / solidification point, in which case the temperature can be lowered, and the amount of ethylene glycol added to obtain the same transition point is smaller. can do. Therefore, the magnesium chloride hydrate used in the present invention is not limited to hexahydrate,
A magnesium chloride hydrate having a composition represented by the general formula MgCL2 · nH2O (n is 6.1 to 10, preferably 6.5 to 8) is used. Such magnesium chloride hydrate can be arbitrarily adjusted by adjusting the amount of water added to magnesium chloride hexahydrate.
As another method, when the magnesium chloride hydrate is hexahydrate, it can be supplemented by adjusting the melting point / freezing point and the water content of the composition used for the temperature drop.

The addition amount of strontium chloride and / or barium chloride is 0.1 to 20 parts by weight, preferably 1 to 10 parts by weight, based on 100 parts by weight of magnesium chloride hydrate. If the addition amount is smaller than this range, solidification becomes difficult when a large amount of ethylene glycol is added, so that the function of the latent heat storage material cannot be obtained. On the other hand, if the addition amount is larger than this, the heat storage density decreases, the effect as a latent heat storage material decreases, and it is economically disadvantageous.

As described above, in the present invention, it is most effective to use a mixture of strontium chloride and barium chloride.
By adding a mixture of 7 to 7 parts by weight and 0.3 to 3 parts by weight of barium chloride, the effect of sufficiently lowering the melting point / solidification point to a low transition point can be obtained even if the total addition amount of both is relatively small. Can be

Further, since the latent heat storage material composition of the present invention is an inorganic hydrated salt, a phase separation phenomenon is likely to occur when it is melted, and the heat storage effect tends to be reduced by repeating melting and solidification. As a solution to this problem, in the present invention, it is preferable to further add 0.1 to 10 parts by weight of sepiolite as a phase separation inhibitor. That is, a more preferred embodiment of the present invention is a method wherein the main ingredient magnesium chloride hydrate 100
1 to 20 parts by weight of ethylene glycol, 0.1 to 20 parts by weight of a single or a plurality of mixtures of salts (lithium chloride, potassium chloride, sodium chloride), and strontium chloride and / or barium chloride 0.1 to 1 part by weight. It is a latent heat storage material composition obtained by mixing 20 parts by weight and 0.1-10 parts by weight of sepiolite.

Here, sepiolite is a hydrated magnesium silicate ceramic having a structural formula of 2MgO.3SiO ₂ .nH ₂ O, which is called sepiolite.
The crystal structure is a very fine fiber crystal, and tunnel-like pores having a fine pore diameter are innumerably present between fibers.
The unique adsorption effect of the tunnel and the network structure in a mixed state prevent separation of water of crystallization, and act as a phase separation inhibitor.

Sepiolite can be used as a fibrous material, as a pulverized powder, or as a mixture thereof. In addition to the sepiolite, a filler such as glass fiber can be further added.

[0023]

The present invention will be specifically described below with reference to examples. [Example 1] Water was added to the magnesium chloride hydrate to prepare a magnesium chloride hydrate having a composition of general formula MgCL ₂ · 7.5H ₂ O. Magnesium chloride hydrate: 100 parts by weight Strontium chloride: 1.5 parts by weight To a mixture of barium chloride: 1.1 parts by weight, ethylene glycol and salts were added at the respective addition amounts shown in Table 1 to form a latent heat storage material composition. The product was prepared and kept at 95 ° C. for 2 hours, then cooled to 40 ° C. and kept for 2 hours to measure the melting point and freezing point. Table 1 shows the results.
Even when ethylene glycol was added up to a maximum of 20 parts by weight, the phase changed smoothly and the melting point could be lowered to 62 ° C.

Unit: parts by weight

[0025]

[Table 1] Comparative Example 1 Neither strontium chloride nor barium chloride was added, and 20 parts by weight of ethylene glycol was added to 100 parts by weight of magnesium chloride hydrate to prepare a latent heat storage material composition. An attempt was made to measure the melting point / freezing point, but the desired result could not be obtained without solidification.

Example 2 Using the same magnesium chloride hydrate used in Example 1, magnesium chloride hydrate: 100.0 parts by weight Strontium chloride: 1.5 parts by weight Barium chloride: 1.1 parts by weight Ethylene glycol: 15.0 parts by weight Lithium chloride Outside: 1.0 parts by weight Sepiolite: 3.0 parts by weight The latent heat storage material obtained by mixing and stirring was used at -25 ° C to +1
In a constant temperature bath where the program can be set up to 25 ° C, the temperature is raised from 80 to 120 ° C to the temperature set in each stage and melted.
Subsequently, it was forcibly cooled to a temperature set to 60 ° C. to solidify. The solidification onset temperature and melting point at that time are almost the same.
° C. The process of melting and solidifying was repeated 500 times in this manner, but there was no change in the cycle function of heat storage and heat radiation.

[0027]

According to the present invention, the latent heat storage material is a mixture of magnesium chloride hydrate, ethylene glycol, lithium chloride, potassium chloride, sodium chloride alone or a mixture of strontium chloride and / or barium chloride among a plurality of salts. Since the transition point of the melting point / solidification point can be changed stably by using the fixing method, the use of heat storage materials in the temperature range around 100 ° C, especially the cooling / heating system and the waste heat, which is unused energy that has been discarded until now, It is useful as a heat storage material.

Claims (4)

[Claims] 1. A method according to claim 1, wherein 1 to 20 parts by weight of a polyhydric alcohol and 100 parts by weight of magnesium chloride hydrate having a composition of the chemical formula MgCL ₂ .nH ₂ O (n is 6.1 to 10) are used. 0.1 to 20 parts by weight of lithium, potassium chloride or sodium chloride alone / mixed with strontium chloride and barium chloride 0.1 to 20
A latent heat storage material composition obtained by mixing parts by weight. 2. The composition according to claim 1, wherein the polyhydric alcohol in the composition is ethylene glycol alone or in combination with other salts (lithium chloride, barium chloride, sodium chloride, etc.) alone or in combination. Latent heat storage material composition. 3. The latent heat storage device according to claim 1, wherein the strontium chloride and / or barium chloride is a mixture having a strontium chloride / barium chloride mixture ratio (weight) of 9/1 to 1/9. Material composition. 4. MgCl ₂ .nH ₂ O (n is 6.1 to 1)
0) to 100 parts by weight of magnesium chloride hydrate having the composition of 0), and 1 to 20 parts by weight of ethylene glycol and 0.1 to 20 of lithium chloride, potassium chloride, and sodium chloride alone or as a mixture of addition salts. A latent heat storage material composition comprising 0.1 to 20 parts by weight of strontium and / or barium chloride and 0.1 to 10 parts by weight of sepiolite.