JP4830639B2 - Latent heat storage material - Google Patents

Description

  The present invention relates to a heat storage latent heat material, and more particularly to a latent heat storage material that can flow even during heat dissipation.

Conventionally, when heat such as exhaust heat or solar heat is used for hot water supply or the like, a heat storage material has been used for the purpose of energy saving and relaxation of load fluctuation of a supply heat source. In recent years, carbon dioxide (CO ₂ ) heat pump household water heaters and cogeneration exhaust heat recovery water heaters have become widespread, and these devices also have a space saving, power leveling, and energy saving viewpoint. Therefore, the use of heat storage materials is considered.

  Taking the above hot water heater as an example, the upper limit temperature of hot water to be supplied by the hot water heater is about 80 to 90 ° C, and the lower limit temperature as the hot water use temperature is about 40 to 60 ° C. The heat storage material used for is required to be in the temperature range of 60 to 90 ° C.

Here, as a general heat storage material can be cited water (H 2 _O). In using water as a heat storage material, there are two types of heat storage methods, sensible heat storage and latent heat storage, depending on the temperature range used. Sensible heat storage of water is a method of storing heat without using a phase change temperature range of 0 ° C. (ice) and 100 ° C. (steam), while latent heat storage of water is a heat storage using the phase change temperature range. Is the method.

  Thus, since the heat storage method using latent heat storage involves a phase change, the heat storage density at the same use temperature difference is larger than that of a heat storage method using sensible heat storage, which is preferable as a heat storage material.

  However, when utilizing the latent heat at the time of phase change (solid-liquid phase change), generally, when heat is taken out from the heat storage material, the heat storage material is solidified, and thus does not fluidize. Therefore, it is disadvantageous in that the heat storage material itself cannot be used as a fluidizable heat transfer medium, and sensible heat sampling after solidification is difficult to perform and heat transfer performance deteriorates.

Based on such problems, the following is a prior document on latent heat storage materials that can maintain a fluid state even during heat dissipation. (For example, see Patent Documents 1 to 3).
JP-A-53-089892 Japanese Patent Laid-Open No. 11-152466 JP 2000-160151 A

  Patent Document 1 discloses a latent heat storage material obtained by adding water to ammonium alum, and by adding the water, the melting point of the latent heat storage material is adjusted, and a latent heat storage material suitable for hot water supply use is disclosed. In addition, fluidity is exhibited even at room temperature.

  However, in the latent heat storage material disclosed in this document, ammonium alum is precipitated in water as a solid phase during heat dissipation. Then, since there is a density difference between the solid phase and water, the deposited solid phase is settled. For this reason, if heat radiation and heat storage are used repeatedly, the concentration distribution of the latent heat storage material is biased, and the dispersed state cannot be maintained, and finally the fluidized state cannot be maintained.

  Patent Document 2 discloses a latent heat storage material that can solve the problem of Patent Document 1, and specifically describes a microcapsulated latent heat storage material. If the latent heat storage material is microencapsulated, the latent heat storage material can surely be prevented from precipitating and settling, and the fluid state can be maintained by dispersing it in the solution.

  However, the ratio of the latent heat storage material itself in one microcapsule is about 60 to 75% by weight. Furthermore, in order to disperse the microcapsulated latent heat storage material in the solution and maintain the fluid state, The said microcapsule can contain only about 10 to 60 weight% with respect to a solution, and when it does so, the ratio with respect to the whole latent-heat storage material itself will be 45 weight% or less, and a thermal storage density will fall remarkably.

  In addition, the microcapsulated latent heat storage material is superior in that the latent heat storage material itself and the water for hot water supply do not come into direct contact with each other, so that they can be directly heat-exchanged. The resin constituting the capsule may be damaged by an external force, and the latent heat storage material itself contained therein may be eluted. In this case, the entire system may be adversely affected. In order to solve this problem, it is possible to design the microcapsule with a large film thickness, but in this case, the heat transfer performance is lowered.

  Furthermore, Patent Document 3 discloses a latent heat storage material to which water, a supercooling inhibitor, and a thickener are added, and by this combination, the fluidization is maintained while the concentration of the entire latent heat storage material is made uniform. It is said.

  However, in the latent heat storage material disclosed in the document, the use temperature range is not suitable for hot water use, and has not been completed to a practical level.

  The present invention has been made by paying attention to various problems of the conventional latent heat storage material as described above, and has higher fluidity and wider use temperature range than the conventional latent heat storage material. It is a main problem to provide a latent heat storage material that can be suitably used for the above.

  In order to solve the above-mentioned problems, the present invention provides a latent heat storage material comprising a water-soluble sugar alcohol or an inorganic hydrated salt, water, and water-insoluble microfibers. It is.

  In the latent heat storage material of the present invention, the melting point is preferably 60 to 90 ° C.

  In the latent heat storage material of the present invention, the sugar alcohol is one or more sugar alcohols selected from the group consisting of xylitol, threitol, erythritol, galactitol, iditol, and dulcitol. It is preferable.

  In the latent heat storage material of the present invention, the inorganic hydrate salt is selected from the group consisting of magnesium chloride, aluminum sulfate, ammonium aluminum sulfate, potassium ammonium sulfate, magnesium sulfate, and sodium phosphate. It is preferable that it is a hydrate salt.

  In the latent heat storage material of the present invention, the microfiber is preferably made of cellulose.

  Moreover, in the latent heat storage material of the present invention, the thickness of the microfiber is preferably 0.01 to 1 μm.

  In the latent heat storage material of the present invention, the content ratio of the microfibers is preferably 5% by weight or less with respect to the entire latent heat storage material.

  Moreover, in the latent-heat storage material of the said invention, it is preferable that the thickener is contained further.

  In the latent heat storage material of the present invention, the thickener is preferably a cellulose-based, acrylic-based, biopolymer-based, or glycol-based thickener.

  In the latent heat storage material of the present invention, the content of the thickener is preferably 1% by weight or less based on the entire latent heat storage material.

  Further, in the latent heat storage material of the present invention, the viscosity is preferably 2000 mPa · s or more.

  The latent heat storage material of the present invention is composed of water-soluble sugar alcohols or inorganic hydrated salts, and has water-insoluble microfibers instead of simply adding water to a substance having a latent heat storage effect. Therefore, the microfiber functions as a dispersant, and the concentration distribution of the entire latent heat storage material can be kept uniform. Therefore, even when heat storage and heat release are repeatedly performed, the substance having the latent heat storage effect does not settle and can always maintain a fluid state. As a result, the heat exchange performance can be improved as compared with the conventional system in which the latent heat storage material is fixed.

  Further, the latent heat storage material of the present invention can adjust the melting point of the entire latent heat storage material at low cost by adjusting the amount of water contained, for example, the melting temperature range is set to 60 to 90 ° C. It can also be used, and can be suitably used in a hot water supply system by setting the temperature range.

  Furthermore, by adding a thickener to the latent heat storage material of the present invention, the viscosity of the entire latent heat storage material can be adjusted, and fluidization can be further promoted.

  In addition, since the latent heat storage material of the present invention does not require the use of microcapsules in order to maintain a dispersed state / fluid state, the latent heat storage material is composed of a water-soluble sugar alcohol or an inorganic hydrated salt for the entire latent heat storage material. Since the ratio of the substance having the latent heat storage effect can be increased, the heat storage density can be improved accordingly.

  Below, the latent-heat storage material of this invention is demonstrated concretely.

  The latent heat storage material of the present invention is characterized by being composed of water-soluble sugar alcohols or inorganic hydrated salts, water, and water-insoluble microfibers.

  Below, it demonstrates in detail for every material required in order to comprise the latent-heat storage material of this invention.

(1) Water-soluble sugar alcohols or inorganic hydrated salt In the latent heat storage material of the present invention, the water-soluble sugar alcohols or inorganic hydrated salt is an essential component, and all of the materials are latent heat. It has a heat storage effect, and is therefore a material that is a main component in the latent heat storage material of the present invention.

  The water-soluble sugar alcohols (organic substances) used in the latent heat storage material of the present invention are not particularly limited and may be appropriately selected and used in consideration of their melting points and the like as long as they have a latent heat storage effect. can do.

  Specifically, for example, xylitol (melting point 94 ° C., latent heat amount 238 KJ / L), threitol (melting point 71 ° C., latent heat amount 325 kJ / L), erythritol (melting point 119 ° C., latent heat amount 446 kJ / L), dulcitol (melting point) 189 ° C., latent heat amount 537 kJ / L), etc., one of these groups may be selected and used, or two or more of these groups may be selected and used in combination. .

  Since such sugar alcohols are food additives, they are highly safe and have a large amount of latent heat. Also, safe and inexpensive water can be used as a melting point adjusting agent. The temperature can be adjusted to the hot water use temperature by adjusting the melting point, and the heat storage density can be made larger than the sensible heat storage of water. Furthermore, fluidization becomes possible by adding water.

Of these, a particularly desirable substance is erythritol. In order to adjust the melting point using water while maintaining the amount of heat, it is necessary to reduce the amount of water added as much as possible. For that purpose, it is desirable that the temperature before the melting point adjustment is close to the target temperature.
Erythritol has a large amount of latent heat compared to other substances, and since the melting point is close to the temperature of using hot water, there is little decrease in the amount of heat by adjusting the melting point.

  On the other hand, in the latent heat storage material of the present invention, it is possible to use an inorganic hydrate salt as a main component instead of the water-soluble sugar alcohols.

  Even in this case, the inorganic hydrate salt is not particularly limited, and can be appropriately selected and used in consideration of its melting point or the like as long as it has a latent heat storage effect. .

  Specifically, for example, magnesium chloride hexahydrate (melting point 117 ° C., latent heat 270 kJ / L), aluminum sulfate decahydrate (melting point 112 ° C., latent heat 270 kJ / L), ammonium aluminum sulfate 12 water Japanese salt (melting point 93.5 ° C., latent heat 440 kJ / L), ammonium sulfate potassium dodecahydrate (melting point 92.5 ° C., latent heat amount 418 kJ / L), magnesium sulfate hexahydrate (melting point 89 ° C., latent heat) (Amount 256 kJ / L), diphosphate sodium decahydrate (79 ° C., latent heat 385 kJ / L), etc., and one of these groups may be selected or used. Two or more of these groups may be selected and mixed for use.

  Compared to other salts, the hydrated salt is safer and has a greater latent heat. It is also possible to use safe and inexpensive water as a melting point modifier. The temperature can be adjusted to the hot water use temperature by adjusting the melting point, and the heat storage density can be made larger than the sensible heat storage of water. Furthermore, fluidization becomes possible by adding water.

  Among the above-mentioned substances, particularly preferable substances include ammonium aluminum sulfate decahydrate. Ammonium ammonium sulfate decahydrate is a food additive and has high safety. Further, in order to adjust the melting point using water while maintaining the amount of heat, it is necessary to reduce the amount of water added as much as possible. For that purpose, it is desirable that the temperature before the melting point adjustment is close to the target temperature. Compared with other substances, ammonium aluminum sulfate dodecahydrate has a large amount of latent heat, and its melting point is close to the temperature at which hot water is used. In addition, ammonium potassium sulfate dodecahydrate has a melting point close to the target temperature and a large amount of heat, but it is problematic in terms of stability because it is easily phase-separated by repeated use.

  In the latent heat storage material of the present invention, the content ratio of the water-soluble sugar alcohols or inorganic hydrate salts is not particularly limited, and the application field, required heat amount, temperature range, etc. It can be determined as appropriate while taking into consideration.

  FIG. 1 is a graph showing the relationship between the content ratio of erythritol relative to the entire latent heat storage material, the melting point, and the amount of heat when erythritol is used as the water-soluble sugar alcohol used in the latent heat storage material.

  As is apparent from FIG. 1, when erythritol is used, the content ratio is 45 to 75% by weight, particularly 65 to 75% by weight with respect to the weight of the entire latent heat storage material (water added). It is preferable to do.

  On the other hand, FIG. 2 shows the content and melting point of the ammonium aluminum sulfate / 12 hydrate salt relative to the whole latent heat storage material when ammonium sulfate / 12 hydrate is used as the inorganic hydrate salt used in the latent heat storage material. It is a graph which shows the relationship with a calorie | heat amount.

  As is clear from FIG. 2, when ammonium aluminum sulfate decahydrate is used, it is 35 to 70% by weight, especially 60 to 70% by weight based on the weight of the whole latent heat storage material (water added). The content ratio is preferably about%.

(2) Water The latent heat storage material of the present invention has the above-mentioned (1) water-soluble sugar alcohol or inorganic hydrate salt as a main component, but is characterized in that water is added thereto. is doing. By using water as the material constituting the latent heat storage material, the fluidity of the entire latent heat storage material can be improved, and the use temperature region (melting point) of the latent heat storage material can be adjusted at a low cost.

  Here, in the latent heat storage material of the present invention, the melting point is preferably set to 60 to 90 ° C. This is because the latent heat storage material of the present invention can be suitably used in a hot water supply system by setting the temperature range.

  About the water which comprises the latent-heat storage material of this invention, it does not specifically limit and normal tap water etc. can be used.

  Moreover, about the content rate of the said water, as above-mentioned, it can adjust suitably so that the utilization temperature area | region (melting | fusing point) of a latent heat storage material may be set in arbitrary ranges.

  For example, as shown in FIG. 1, when erythritol is used as the substance having the latent heat storage action described above, the use temperature region (melting point) of the latent heat storage material is set to 60 to 90 ° C. Then, it is preferable to set it as 45 to 25 weight% with respect to the whole latent heat storage material weight.

  On the other hand, as shown in FIG. 2, as the substance having the latent heat storage action, ammonium aluminum sulfate decahydrate is used, and the utilization temperature region (melting point) of the latent heat storage material is set to 60. In the case where the temperature is set to ˜90 ° C., it is preferably 65 to 30% by weight with respect to the entire latent heat storage material.

(3) Microfibers The latent heat storage material of the present invention is characterized in that microfibers are further contained in addition to (1) water-soluble sugar alcohols or inorganic hydrated salts and (2) water described above. Have. By using microfibers as the material constituting the latent heat storage material, (1) it is possible to prevent the water-soluble sugar alcohols or inorganic hydrate salts from precipitating and settling, and as a result, the latent heat storage material It becomes possible to keep the entire density distribution uniform. That is, in the present invention, it can be said that the microfiber functions as a dispersant for water-soluble sugar alcohols or inorganic hydrates having a latent heat storage effect.

  The fine fiber constituting the latent heat storage material of the present invention is not particularly limited as long as it is a fiber having an effect of dispersing a water-soluble sugar alcohol or inorganic hydrate salt as a main component in water. Is preferably used. This is because by using microfibers made of cellulose, the fibers can be entangled with water-soluble sugar alcohols or inorganic hydrated salts in water to maintain a dispersed state. In addition, since cellulose has a small viscosity change due to temperature in a temperature range (for example, 60 to 90 ° C.) in which a latent heat storage material is normally used (that is, the temperature dependence of viscosity is small), heat storage and heat dissipation were repeated. Even if it is a case, it can be said that it is a preferable material also at the point which can maintain the said dispersion | distribution state favorably.

  Here, in the present invention, the thickness of the microfiber can be appropriately designed in consideration of dispersibility and the like, and is preferably about 0.01 to 1 μm, for example. This is because the dispersion state can be maintained satisfactorily by using such fine fibers.

  Further, the content ratio of the microfibers can be appropriately designed. Specifically, the content ratio is 5% by weight or less based on the weight of the entire latent heat storage material (substance having heat storage action + water) described above. It is preferable. If the proportion of microfibers relative to the entire latent heat storage material is increased, the content ratio of water-soluble sugar alcohols or inorganic hydrate salts that exhibit latent heat storage action will decrease accordingly, leading to a decrease in heat storage density. It is. In addition, the lower limit of the content ratio of the microfiber is not particularly limited, and may be contained to such an extent that dispersibility can be ensured, but specifically, 1% by weight or more is considered necessary. If the amount is less than this, the dispersibility will be lowered, causing precipitation of water-soluble sugar alcohols or inorganic hydrated salts, which may make it difficult to maintain a uniform concentration distribution.

(4) Other materials As described above, the latent heat storage material of the present invention is composed of (1) water-soluble sugar alcohols or inorganic hydrated salts, (2) water, and (3) microfibers. However, it is also possible to include materials other than these.

  For example, in the latent heat storage material of the present invention, it is preferable to further contain a thickener. By incorporating a thickener, the dispersibility of the water-soluble sugar alcohols or inorganic hydrate salts as the main component can be further improved.

  Here, examples of the thickener used in the latent heat storage material of the present invention include a cellulose-based, acrylic-based, biopolymer-based, or glycol-based thickener, and among these, a cellulose-based agent is particularly preferable. The thickener is preferred. This is because these thickeners have relatively small temperature dependence, and therefore, even when heat storage and heat dissipation are repeated, there is little influence due to temperature changes.

  Examples of the cellulose-based thickener include carboxymethyl cellulose and hydroxylmethyl cellulose.

  The content of such a thickener is not particularly limited in the present invention. For example, it is 1% by weight or less based on the weight of the entire latent heat storage material (substance + water having a latent heat storage function) described above. It is preferable. This is because, as in the case of the above-described microfiber, if the content is larger than this, the heat storage density is reduced. In addition, when the addition amount is excessive, the fluid state cannot be maintained and the crystallization rate is slowed down. In addition, although there is no limitation in particular about the lower limit of the content rate of the said thickener, I think that specifically 0.1 weight% or more is required. If it is less than this, a dispersion effect cannot be obtained.

  Moreover, in the latent heat storage material of the present invention, when the above-mentioned thickener is included, the viscosity is preferably 2000 mPa · s or more. This is because, by setting the viscosity of the entire latent heat storage material to 2000 mPa · s or more, a good fluid state can be maintained while maintaining the dispersed state of the heat storage material.

  According to the latent heat storage material of the present invention described above, water-soluble sugar alcohols or inorganic hydrate salts can be prevented from precipitating and settling even during heat dissipation, and a uniform concentration distribution is always maintained. And good fluidity can be maintained. Therefore, it can be effectively used particularly in a hot water supply system.

  Table 1 below shows one specific example.

表１からも明らかなように、従来から用いられているエリスリトール、硫酸アンモニウムアルミニウム・１２水和塩と水とからなる潜熱蓄熱材を水に含有せしめた場合、撹拌等による分散効果を与えなければ数秒で沈降してしまった。しかしながら、本発明の潜熱蓄熱材、具体的には、潜熱蓄熱作用を有する物質としてエリスリトール、硫酸アンモニウムアルミニウム・１２水和塩を用い、これに水と微小繊維としてのセルロースとを含有してなる潜熱蓄熱材にあっては、撹拌等を行わずして半日以上も沈降しないで流動性を維持することができた。さらに、前記本発明の潜熱蓄熱材にさらに増粘剤としてヒドロキシルメチルセルロースを含有すると、１日後であっても沈殿することはなく、流動性を維持することができた。

As is clear from Table 1, when a latent heat storage material consisting of erythritol, ammonium aluminum sulfate, 12 hydrate salt and water, which has been used in the past, is contained in water, it does not give a dispersing effect by stirring or the like for several seconds. It settled in. However, the latent heat storage material of the present invention, specifically, erythritol and ammonium aluminum sulfate dodecahydrate are used as a substance having a latent heat storage action, and the latent heat storage material contains water and cellulose as microfibers. In the case of the material, it was possible to maintain fluidity without stirring or the like and without settling for more than half a day. Furthermore, when the latent heat storage material of the present invention further contains hydroxylmethylcellulose as a thickener, it did not precipitate even after one day and was able to maintain fluidity.

It is a graph which shows the relationship between the content rate with respect to the whole latent heat storage material of the said erythritol, melting | fusing point, and calorie | heat amount in the case of using erythritol as water-soluble sugar alcohol used in a latent heat storage material. As the inorganic hydrate salt used in the latent heat storage material, when ammonium aluminum sulfate / 12 hydrate is used, the relationship between the content ratio of the ammonium sulfate / 12 hydrate relative to the entire latent heat storage material, the melting point, and the amount of heat It is a graph to show.

Claims (11)

Water-soluble sugar alcohols or inorganic hydrate salts,
water and,
Water-insoluble microfibers,
A latent heat storage material comprising:   Melting | fusing point is 60-90 degreeC, The latent-heat storage material of Claim 1 characterized by the above-mentioned.   The latent heat according to claim 1 or 2, wherein the sugar alcohol is one or two or more sugar alcohols selected from the group consisting of xylitol, threitol, erythritol, galactitol, iditol, and dulcitol. Thermal storage material.   2. The inorganic hydrate salt is one or more hydrate salts selected from the group consisting of magnesium chloride, aluminum sulfate, ammonium aluminum sulfate, potassium ammonium sulfate, magnesium sulfate, and sodium phosphate. Or the latent heat storage material of 2.   The latent heat storage material according to any one of claims 1 to 4, wherein the microfiber is made of cellulose.   The latent heat storage material according to any one of claims 1 to 5, wherein a thickness of the microfiber is 0.01 to 1 µm.   The content rate of the said microfiber is 5 weight% or less with respect to the whole latent heat storage material, The latent heat storage material as described in any one of Claims 1-6 characterized by the above-mentioned.   Furthermore, the thickener is contained, The latent heat storage material as described in any one of Claims 1-7 characterized by the above-mentioned.   The latent heat storage material according to claim 8, wherein the thickener is a cellulose-based, acrylic-based, biopolymer-based, or glycol-based thickener.   The content rate of the said thickener is 1 weight% or less with respect to the whole latent heat storage material, The latent heat storage material of Claim 8 or 9 characterized by the above-mentioned.   The latent heat storage material according to any one of claims 8 to 10, wherein the viscosity is 2000 mPa · s or more.

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