JP2001031956A - Latent heat storage material composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a latent heat storage material composition whose melting point/solidification point is within a temperature range of 28 to 50 deg.C and which can be used for heat insulation of heating tools and as a heat storage material for waste heat recovery systems and air-conditioning heating systems. SOLUTION: The composition is obtained by mixing 100 pts.wt. of sodium acetate hydrate having a composition of the formula CH3COONa.nH2O (wherein n is 2.8 to 3.2), 1 to 20 pts.wt. of ethylene glycol, 1 to 20 pts.wt. of plural salts including potassium chloride, lithium chloride and sodium chloride, used singly or in combination, and 0.1 to 20 pts.wt. of chelating compounds of acetic acid used singly or in combination as a complex salt, preferably a mixing having a mixing ratio (by weight) of chelating compound/of 9/1 to 1/9, and further mixing with 0.1 to 10 pts.wt. of a filler and 0.1 to 10 pts.wt. of graphite.

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. In detail, the temperature range (around 28-50 ° C) suitable for systems such as floor heating using nighttime electricity, passive energy, recovery of unused waste heat (heat storage tank), and electric appliances that require heat storage and heat retention. The present invention relates to a latent heat storage material composition useful for use in (1).

[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 used effectively, it is widely used as a latent heat storage material, for example, for heat storage for recovering and using passive energy such as heating and waste heat, and for using nighttime electric 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.
Hydrate separates into two phases of anhydrous crystals and its saturated aqueous solution during the melting / solidification process, or generates two transition points depending on the substance used to lower the freezing point / melting point, and can release heat at a certain temperature. Did not. In addition, the phenomenon that hydrated salts are not formed even if the saturated aqueous solution phenomenon is left to cool even if it is cooled (phase separation), or that it does not solidify at the freezing point even if the temperature is lowered, does not cause heat dissipation of latent heat (supercooling). And 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 sodium acetate hydrate is around 58.5 ° C. at constant pressure, and the heat of fusion is 264 joules / g. The latent heat storage material is a material in the middle temperature range, but is generally not suitable for use in heat dissipation (around 40 ° C.) such as floor heating because the 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 sodium acetate 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 sodium acetate is used. A temperature drop by the addition of salts is preferred. In addition, sodium salts, potassium chloride, and lithium chloride are economically used as salts, 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 ethylene glycol is added in a relatively small amount, the melting point can be lowered according to the amount of ethylene glycol. However, when the amount is increased, the melting point / solidification point drops extremely, making it difficult to form crystals. No longer coagulates. In addition, ethylene glycol is 10% for sodium acetate hydrate.
If the additive content is further increased beyond the weight%, the hydrated salt generally has a crystallized crystal and extremely low melting point / solidification point, is easily supercooled, has a low heat storage density, and has a heat storage density. Is less effective as a latent heat storage material. For these reasons, the amount of addition is in the range of 1 to 25% by weight.

Therefore, a latent heat storage material that can be used in a limited temperature range (around 28 to 50 ° C.), which is the object of the present invention, cannot be used with sodium acetate alone. It is a latent heat storage material that can effectively use latent heat.

[0008]

DISCLOSURE OF THE INVENTION The present invention has studied a solar heat collector and a latent heat storage material mainly composed of sodium acetate hydrate which can be used in a temperature range suitable for storing energy for nighttime power use. As a result, among ethylene glycol and salts, lithium chloride, potassium chloride, and sodium chloride alone or in combination or in combination with a chelate compound (for example, ethylenediaminetetrahydrogen acetate
EDTA-2Na · 2H ₂ as sodium dihydrate)
O, EDTA-3Na · 2H ₂ O, EDTA-H · 3N
a · 3H ₂ O, EDTA-4Na · 4H ₂ O, NTA-
It is effective to add 3Na · H ₂ O alone or as a mixture, whereby even if ethylene glycol is added in an amount of 15% by weight or more, the melting point / freezing point can be adjusted without any problem.
A latent heat storage material composition that can be lowered to a temperature suitable for use, and can be used for a floor heating heat storage system using nighttime electric power, a hot water system heat storage tank using solar heat, waste heat use, and the like.

[0009]

That is, the present invention relates to 100 parts by weight of sodium acetate hydrate having a composition of the general formula CH ₃ COONa · nH ₂ O (n is 2.8 to 3.2), 1 to 20 parts by weight, 0.1 to 20 parts by weight of a salt alone or a mixture of lithium chloride, potassium chloride and sodium chloride and a chelate compound EDTA
-2Na · 2H ₂ O, EDTA-3Na · 2H ₂ O, E
DTA-H · 3Na · 3H ₂ O, EDTA-4Na · 4
A latent heat storage material composition comprising 0.1 to 20 parts by weight of a single or a mixture of H ₂ O and NTA-3Na · H ₂ O.

In the present invention, among the above chelating compound agents, EDTA-2Na.2H ₂ O and EDTA-3
Na · 2H ₂ O, EDTA-H · 3Na · 3H ₂ O, E
DTA-4Na · 4H ₂ O, NTA-3Na · H ₂ O,
It is a preferred embodiment to use the acetic acid complex salts of the above alone or in combination.

Further, the present invention relates to the heat storage material composition, wherein 0.1 to 10 parts by weight of sepiolite or 0.1 to 10 parts by weight of fiber is used as a phase separation preventing material among inorganic ceramics mainly composed of silicate. It includes a composition added alone or as a mixture.

[0012]

DETAILED DESCRIPTION OF THE INVENTION Sodium acetate hydrate used as a main component of the latent heat storage material of the present invention has a chemical formula of CH ₃ CO.
The so-called sodium acetate hydrate represented by ONa · 3H ₂ O includes CH ₃ COONa · nH ₂ O (n is 2.8 to less), including those in which the amount of crystallization water is slightly increased or decreased.
It is a sodium acetate hydrate having the composition of 3.2).
n is a number corresponding to the number of moles of water of crystallization of the hydrate, and n = 3
Is sodium acetate trihydrate. Such sodium acetate hydrate can be prepared by adding ethylene glycol which binds and matches sodium acetate anhydride or sodium acetate 2.8 hydrate.

Examples of the temperature lowering substance include various ammonium (nitric acid, sulfuric acid, urea), ethylene glycol and the like. Salts include potassium chloride, sodium chloride, ammonium chloride and the like. Ethylene glycol alone or in combination with a plurality of salts is preferable because it has a large melting point / solidification point drop and a large economic effect.

It is preferable to use the chelate compound alone or as a mixture of two types, since the effect can be further improved.

In the present invention, the amount of ethylene glycol added to sodium acetate hydrate, which is 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 sodium acetate 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 is melted within the temperature range of the present invention and within about 3 ° C. or less from the melting temperature. Solidifies, but in the present invention,
By adding a chelate compound alone or in a mixture to be a 2,3,4-acetic acid complex salt, the effect of adding such a large amount of ethylene glycol can be exerted and the desired temperature can be adjusted. For example, chelate compound parts by weight,
5.0 parts by weight (all based on 100 parts by weight of main agent)
In the case of addition, by adding 20% of ethylene glycol, the melting point / solidification point can be lowered to 28 ° C., 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 affected by the proportion of water of crystallization of the sodium acetate hydrate used. Using a hydrate with more water of crystallization rather than pure sodium acetate trihydrate has a melting point /
The transition point such as the freezing point can be changed, in this case, the temperature can be lowered, and the amount of ethylene glycol added to obtain the same transition point can be reduced. Therefore, the sodium acetate hydrate used in the present invention is not limited to trihydrate, but may be represented by the general formula CH ₃
Sodium acetate hydrate having a composition of COONa.nH2O (n is 2.8 to 3.2) is used. Such sodium acetate hydrate is characterized in that an arbitrary melting point is adjusted by partially adjusting the amount of water added to sodium acetate hydrate to ethylene glycol.

The amount of the chelate compound is 0.1 to 20 parts by weight, preferably 2 to 10 parts by weight, based on 100 parts by weight of sodium acetate 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, a chelate compound is effective. For example, by adding 0.1 to 10 parts by weight of a chelate compound alone or in combination or by adding 0.1 to 10 parts by weight of a chelate compound, the melting point / freezing point is sufficiently low. The effect of lowering the transition point and the prevention of supercooling can be obtained.

Further, since the latent heat storage material composition of the present invention is an inorganic hydrate salt, a phase separation phenomenon is liable to occur when it is melted. Have a problem with the heat transfer properties of the As a solution for preventing separation, the present invention further comprises adding 0.1 to 10 parts by weight of sepiolite as a phase separation inhibitor, or adding 0.1 to 10 parts by weight of a mixture of graphite fine powder and a filler on the same as thermal conductivity. It is preferred to add a partial range. That is, a more preferred embodiment of the present invention,
For 100 parts by weight of sodium acetate hydrate as the main agent,
1 to 20 parts by weight of ethylene glycol, 0.1 to 20 parts by weight of a mixture of a single salt or a plurality of salts (lithium chloride, potassium chloride, sodium chloride), and 0.1 to 10 parts by weight of a mixture of a chelate compound and sepiolite and a filler. Parts by weight,
A latent heat storage material composition comprising 0.1 to 10 parts by weight of graphite.

Here, sepiolite is called sepiolite,
It is a hydrated magnesium silicate ceramic having a structural formula of 2MgO.3SiO ₂ .nH ₂ O. The crystal structure is a very fine fiber crystal, and tunnel-like pores having a fine pore diameter are innumerably present between fibers. In a state where the specific adsorption effect by the tunnel and the main agent are mixed, a network structure is formed, and a very small cell structure is formed to prevent separation of water of crystallization. The substance has an amphoteric action of both a phase separation inhibitor and a crystallization agent.

Sepiolite can be used as a fibrous material, as a pulverized powder, or as a mixture thereof. Also, by adding various fillers such as fibers in addition to sepiolite, sepialite can be reduced, which is more effective in the mass of heat storage.

[0023]

The present invention will be specifically described below with reference to examples. Example 1 Sodium acetate hydrate was added with sodium acetate anhydride to prepare a compound of the general formula CH ₃ COONa · 2.8.
Sodium acetate hydrate having a composition of between H ₂ O and 3.2H ₂ O was prepared. Sodium acetate hydrate: 100 parts by weight Chelate compound: 2.5 parts by weight Ethylene glycol and salts were added at the respective addition amounts shown in Table 1 to prepare a latent heat storage material composition. After keeping at 2 ° C. for 2 hours, the temperature was lowered to 28 ° 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 20 parts by weight, the phase changed smoothly, and the melting point could be lowered to 40 ° C.

[Table 1] Unit: parts by weight

[0025] Comparative Example 1 A latent heat storage material composition was prepared by adding 20 parts by weight of ethylene glycol to 100 parts by weight of sodium acetate hydrate without adding a chelate compound / filler, in the same manner as in Example 1. An attempt was made to measure the melting point / freezing point but did not solidify and the desired results were not obtained.

Example 2 Using the same sodium acetate hydrate used in Example 1, sodium acetate hydrate: 100.0 parts by weight Chelate compound: 3.0 parts by weight Ethylene glycol: 20.0 parts by weight Salts: 6.0 parts by weight Filler 3.0 parts by weight Graphite 1.5 parts by weight was mixed and stirred.
The mixture was heated to a temperature set at each stage from 20 to 70 ° C. in a constant temperature bath in which a program could be set to 25 ° C., melted, and then forcibly cooled to a temperature set to 20 ° C. to solidify. The solidification start temperature and melting point at that time are almost the same 28 ° C
Is constant endothermic melting / radiation solidification. The process of melting and solidifying was repeated 1,000 times in this way, 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 comprises sodium acetate hydrate, ethylene glycol, potassium chloride, sodium chloride, lithium chloride alone or a mixture of a plurality of salts, and a chelate compound alone / mixture fixed with a filler. As a result, the transition point of the melting point / freezing point can be changed stably at a constant temperature, so that the heat storage material, in which the melting point / freezing point can be arbitrarily set in a temperature range of about 28 to 50 ° C., particularly a heating system and a heating system, which has been discarded up to now. It is useful as a heat storage material for utilizing waste heat, which is unused energy. Preferably, the addition of graphite is useful for improving the thermal conductivity.

Claims (4)

[Claims] 1. The chemical structural formula: CH ₃ COONa.nH ₂ O
(N is 2.8 to 3.2), 100 parts by weight of sodium acetate hydrate having a composition of
0 parts by weight and salts (lithium chloride, potassium chloride,
Sodium chloride, etc.) 1 to 20 parts by weight alone or in combination with a mixture, the chelate compound forming a complex salt with acetic acid is 0.1 to 20 parts by weight, and the filler is 0.1 to 10 parts by weight. A latent heat storage material composition obtained by mixing parts. 2. The latent heat storage material composition according to claim 1, wherein the composition is prepared by using ethylene glycol alone or in combination with lithium chloride, potassium chloride or sodium chloride alone or in combination as a salt. _EDTA-2Na · 2H 2 O of 3. A chelate compound complex is 2,3,4 acid, NTA-3Na · H
₂ O, EDTA-3Na.2H ₂ O, EDTA-H3N
3. The latent heat storage material composition according to claim 1, wherein the latent heat storage material composition is a constituent product of a single / mixture of a chelate compound, such as a · 3H ₂ O or EDTA-4Na · 4H ₂ O. 4. 4. The latent heat storage material composition according to claim 1, wherein the filler of the composition is a mixture of 0.1 to 10 parts by weight of a vegetable fiber, a chemical substance fiber, an inorganic substance fiber or the like alone or as a mixture.