heat storage

Abstract

To provide a technique for holding a phase change material in a silica porous body and storing heat which improves stability of heat storage and heat storage property.SOLUTION: A heat storage body having a spherical silica porous body in which a plurality of substantially columnar pores are formed has a phase change material in the plurality of pores of the spherical silica porous body, wherein in the spherical silica porous body, the plurality of pores have uniform porous sizes, and are radially arranged toward the surface from the center of the spherical porous body, and a center pore diameter of the plurality of pores is 1 nm or more and 20 nm or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a heat storage body having a spherical silica porous body. [Background technology]

[0002] Conventionally, technologies have been proposed that involve holding a phase-change material in a solid to store heat (see, for example, Patent Document 1, Non-Patent Documents 1 and 2).

[0003] Patent Document 1 discloses a hard-shelled microencapsulated latent heat transport material in which a phase change material is encapsulated within non-porous hollow silica particles. Non-Patent Document 1 discloses a technique for encapsulating a phase change material inside the pores of mesoporous silica. Non-Patent Document 2 discloses a material in which LiOH is supported inside the pores of mesoporous silica that has water vapor adsorption properties. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] International Publication No. 2015 / 025529 [Non-patent literature]

[0005] [Non-Patent Document 1] Kota Nakano, et al., "Solidification and Melting Phenomena of Erythritol in the Pores of Mesoporous Silica," Proceedings of the 2013 Japan Society of Mechanical Engineers Thermal Engineering Conference, G133, Japan Society of Mechanical Engineers, No. 13-55, pp. 219-220. [Non-Patent Document 2] Mitsuhiro Kubota, "Development of Lithium Hydroxide-Mesoporous Silica Hybrid Materials Aiming for High-Density Chemical Heat Storage," Research Results Report of the Grant-in-Aid for Scientific Research, May 27, 2015. [Overview of the project] [Problems that the invention aims to solve]

[0006] The technology described in Patent Document 1 had problems with the packing density and dispersibility of the capsule particles, and sufficient heat storage stability could not be obtained. In the technology described in Non-Patent Document 1, leakage of erythritol as a heat storage material from the pores was confirmed. In the technology described in Non-Patent Document 2, a sufficient hydration reaction (=heat dissipation) rate could not be obtained. Thus, stable heat storage was difficult even with the technologies described in Patent Document 1 and Non-Patent Documents 1 and 2.

[0007] In view of the above issues, the objective is to provide a technology that improves the stability and heat storage capacity of heat storage in a technology that stores a phase change material in a silica porous body for heat storage. [Means for solving the problem]

[0008] The present invention has been made to solve at least some of the above-mentioned problems and can be realized in the following forms.

[0009] (1) According to one embodiment of the present invention, a heat storage body is provided having a spherical silica porous body in which a plurality of substantially cylindrical pores are formed. The heat storage body has a phase change material in the plurality of pores of the spherical silica porous body, and in the spherical silica porous body, the plurality of pores have a uniform pore diameter and are arranged radially from the center toward the surface of the spherical silica porous body, and the central pore diameter of the plurality of pores is 1 nm or more and 20 nm or less.

[0010] According to this configuration, multiple pores are arranged radially from the center toward the surface of the spherical silica porous body, so compared to, for example, the honeycomb-shaped silica porous body described in Non-Patent Document 1, Since one end of the pore is not open, leakage of the phase change material can be suppressed. Because the shape of the pore is approximately cylindrical, the phase change material is held by capillary force, and even if it liquefies due to melting, leakage to the outside can be suppressed, and the stability of the holding can be maintained.

[0011] If the diameter of the pores in the spherical silica porous material is too small, it becomes difficult to introduce the phase change material. Also, since the introduction of the phase change material into the pores of the spherical silica porous material is carried out by the capillary force of the pores, if the diameter of the pores in the spherical silica porous material is too large, the capillary force will not work effectively, and the phase change material will not be sufficiently filled. If the amount of phase change material filled is insufficient, the amount of heat stored by the heat storage body will be small. In contrast, with this configuration of heat storage body, the central pore diameter of the pores in the spherical silica porous material is between 1 nm and 20 nm, so a sufficient amount of phase change material is filled, and the heat storage performance of the heat storage body can be improved.

[0012] (2) In the heat storage body of the above form, the plurality of pores in the spherical silica porous body may have a standard deviation of within 25% of the central pore diameter in the range where the pore diameter of the pore diameter distribution curve is greater than 1 nm. In this case, the uniformity of the pore diameter of the spherical silica porous body is high, so the tubular force acts more uniformly, the packing rate of the phase change material can be improved, and the heat storage capacity of the heat storage body can be further improved.

[0013] (3) The heat storage body of the above form may have a diameter of 10 nm or more and 3000 nm or less. This makes it possible to improve the packing rate when using multiple heat storage bodies packed into a container, and the monodispersity when dispersing multiple heat storage bodies in a dispersion medium.

[0014] (4) A heat storage body of the above form, wherein the plurality of pores of the spherical silica porous body have a pore volume of 0.9 [ml / g] or more, and a specific surface area of ​​1.4 × 10 per unit pore volume. 9 [m 2 / m 3 It may also be less than or equal to ]. In this way, the proportion of phase change material that acts effectively as a latent heat storage material can be increased, thereby increasing the heat storage density.

[0015] (5) The heat storage body of the above form, wherein the phase change material may be at least one of sugar alcohol and paraffin. Since sugar alcohol has a high heat storage density, a heat storage body with good heat storage performance can be provided. Since paraffin has a low degree of supercooling, a decrease in heat storage efficiency can be suppressed.

[0016] In addition, the present invention can be realized in various forms. For example, it can be realized in the form of a heat transport system using a heat storage body, a system including the heat transport system, and the like.

Brief Description of the Drawings

[0017] [Figure 1] It is an explanatory diagram conceptually showing heat storage in the heat storage body of one embodiment of the present invention. [Figure 2] It is an explanatory diagram conceptually showing the configuration of the spherical silica porous body of the present embodiment. [Figure 3] It is an explanatory diagram conceptually showing the manufacturing method of the spherical silica porous body of the example. [Figure 4] It is an explanatory diagram conceptually showing the manufacturing method of the spherical silica porous body of the example. [Figure 5] It is an explanatory diagram conceptually showing the manufacturing method of the spherical silica porous body of the comparative example. [Figure 6] It is a SEM image of the spherical silica porous body used in the heat storage body of the example. [Figure 7] It is a SEM image of the spherical silica porous body used in the heat storage body of the example. [Figure 8] It is a SEM image of the spherical silica porous body used in the heat storage body of the comparative example. [Figure 9] It is a diagram showing the nitrogen adsorption isotherm of the spherical silica porous body used in the heat storage body. [Figure 10] It is a diagram showing the pore size distribution curve of the spherical silica porous body used in the heat storage body. [Figure 11] It is a diagram showing the physical properties of the phase change materials used in the example and the comparative example. [Figure 12]This diagram shows the pore parameters of the heat storage material and the amount of phase change material (erythritol). [Figure 13] This figure shows the pore parameters of the heat storage material and the amount of phase change material (linear paraffin). [Figure 14] This figure shows the TGA curve of a phase-change material. [Figure 15] This figure shows the DSC curve of a phase-change material. [Figure 16] This figure shows the filling rate of erythritol and the ratio of effective / ineffective heat storage material. [Figure 17] This figure shows the filling rate of linear paraffin and the ratio of effective / ineffective heat storage material. [Figure 18] This is an explanatory diagram conceptually illustrating the effective and ineffective heat storage molecules within the pores. [Figure 19] This is a conceptual diagram illustrating the relationship between specific surface area per unit pore volume and effective heat storage material. [Figure 20] This is an explanatory diagram showing the dependence of the heat storage density of erythritol on pore capacity. [Figure 21] This is an explanatory diagram showing the dependence of the heat storage density of erythritol on its specific surface area. [Figure 22] This is an explanatory diagram showing the dependence of the heat storage density of linear paraffins on pore capacity. [Figure 23] This is an explanatory diagram showing the dependence of the heat storage density of linear paraffins on their specific surface area. [Modes for carrying out the invention]

[0018] Figure 1 is a conceptual diagram illustrating heat storage in a heat storage body 1 according to one embodiment of the present invention. In Figure 1, a portion of the heat storage body 1 is cut out to illustrate its internal structure. The heat storage body 1 comprises a spherical silica porous body 100 having a plurality of pores 10, and a phase change material 200 located within the pores 10. The shape of the pores 10 of the spherical silica porous body 100 is approximately cylindrical. The plurality of pores 10 have a uniform pore diameter and are arranged radially from the center of the spherical silica porous body 100 toward the surface. In the figure, some of the pores 10 and some of the phase change material 200 are labeled with reference numerals, while the labeling of other parts is omitted. Figure 1 is a conceptual representation of the heat storage body 1, and the number of pores may be more or less than that shown. In addition, although an example is shown in which the phase change material 200 fills the entire pore 10, the phase change material 200 may be filled only in a portion of the pores 10.

[0019] The phase change material 200 absorbs and releases latent heat in response to temperature changes. The heat storage body 1 absorbs and releases heat by utilizing the phase change (solid to liquid) of the phase change material 200. Specifically, when the phase change material 200 held in the spherical silica porous body 100 changes from solid phase change material 200S (upper part of Figure 1) to liquid phase change material 200L (lower part of Figure 1), it absorbs heat from the surroundings near the melting point and tries to maintain the temperature near the melting point. Conversely, when the liquid phase change material 200L (lower part of Figure 1) changes to solid phase change material 200S (upper part of Figure 1), it releases heat to the surroundings near the freezing point and tries to maintain the temperature near the freezing point until it completely solidifies. In other words, the heat storage body 1 stores heat by utilizing the absorption and release of latent heat associated with the solidification and melting of the phase change material 200. In Figure 1, the solid phase change material 200 is shown with cross-hatching and labeled 200S, while the liquid phase change material 200 is shown with dot-hatching and labeled 200L.

[0020] (1) Spherical silica porous material 100 Figure 2 is a conceptual diagram illustrating the structure of the spherical silica porous body 100 of this embodiment. In Figure 2, as in Figure 1, a portion of the spherical silica porous body 100 is cut out to illustrate the shape and arrangement of the pores 10. The pores 10 are shown with hatching in the cross-section. As shown in the figure, the spherical silica porous body 100 of this embodiment has a plurality of substantially cylindrical pores 10, and the plurality of pores 10 are arranged radially from the center of the spherical silica porous body 100 toward the surface. The arrangement of the plurality of pores 10 can be confirmed by observing the heat storage body 1 with a TEM (Transmission Electron Microscope). Furthermore, by introducing a metal (for example, platinum) into the pores of the heat storage body 1 and observing it with a TEM, the arrangement of the plurality of pores can be confirmed more clearly.

[0021] Multiple pores 10 are arranged radially from the center toward the surface of the spherical silica porous body 100. Compared to, for example, the honeycomb-shaped silica porous body described in Non-Patent Document 1, one end of the pores 10 is not open, thus suppressing leakage of the phase change material 200. Because the shape of the pores 10 is approximately cylindrical, the phase change material 200 is held by capillary force, and even if it liquefies due to melting, leakage to the outside can be suppressed, and the stability of the hold can be maintained.

[0022] The central pore diameter of the multiple pores 10 is between 1 nm and 20 nm. More preferably, it is between 2 nm and 10 nm. If the diameter of the pores 10 of the spherical silica porous body 100 is too small, it is difficult to introduce the phase change material 200. Also, since the introduction of the phase change material 200 into the pores 10 of the spherical silica porous body 100 is performed using the capillary force of the pores 10, if the diameter of the pores 10 of the spherical silica porous body 100 is too large, the capillary force will not work effectively, and the phase change material 200 will not be sufficiently filled. If the amount of phase change material 200 filled is insufficient, the amount of heat stored by the heat storage body 1 will be small. In contrast, according to the heat storage body 1 of this embodiment, since the central pore diameter of the pores 10 of the spherical silica porous body 100 is between 1 nm and 20 nm, a sufficient amount of phase change material 200 is filled, and the heat storage performance of the heat storage body 1 can be improved.

[0023] The pore diameters of the multiple pores 10 in the spherical silica porous body 100 are uniform. Here, uniform pore diameter means that the standard deviation of the pore diameter distribution curve in the range where the pore diameter is greater than 1 nm is within 35% of the central pore diameter. The central pore diameter refers to the pore diameter that shows a maximum peak in the range where the pore diameter is greater than 1 nm in the pore diameter distribution curve. Preferably, the standard deviation of the multiple pores 10 in the spherical silica porous body 100 in the range where the pore diameter is greater than 1 nm in the pore diameter distribution curve is within 25% of the central pore diameter. More preferably, it is within 20%. In this way, because the uniformity of the pore diameters of the multiple pores 10 in the spherical silica porous body 100 is high, the capillary force acts more uniformly, and the packing rate of the phase change material 200 can be improved, making it possible to create a heat storage body 1 with higher heat storage capacity.

[0024] The diameter of the spherical silica porous body 100 is not particularly limited, but it is preferably on the order of several hundred nanometers. More preferably, the diameter of the spherical silica porous body 100 is between 10 nm and 30,000 nm. This improves the packing efficiency when multiple heat storage bodies 1 are packed into a container and the monodispersity when multiple heat storage bodies 1 are dispersed in a dispersion medium. The spherical silica porous body 100 of this embodiment has a uniform pore diameter for the multiple pores 10, and the multiple pores 10 are arranged radially from the center toward the surface of the spherical silica porous body 100, so it can also be called a "spherical silica porous body with highly regular pores."

[0025] The pore volume and specific surface area per unit pore volume of the spherical silica porous body 100 are not particularly limited, but the pore volume is 0.9 [ml / g] or more, and the specific surface area per unit pore volume is 1.4 × 10⁻⁶. 9 [m 2 / m 3 It is preferable that the value is less than or equal to ]. In this way, the proportion of the phase change material 200 that acts effectively as a latent heat storage material increases, making it possible to create a heat storage body 1 with a high heat storage density.

[0026] The spherical silica porous body 100 can be synthesized by the method described in Japanese Patent No. 5480461. During synthesis, the diameter of the pores 10 can be adjusted by changing the type of surfactant. Furthermore, the pore diameter can be enlarged after synthesis by replacing the surfactant with another surfactant, introducing a swelling agent, or performing hydrothermal treatment under acidic conditions.

[0027] (2) Phase change materials In the heat storage body 1, a phase change material 200 is held within the pores 10 of the spherical silica porous body 100 (Figure 1). The phase change material 200 is not particularly limited, but sugar alcohols are preferred because they have a high heat storage density and can provide a heat storage body with good heat storage capacity. Paraffins are also preferred because they have a low degree of supercooling and can suppress a decrease in heat storage efficiency. Erythritol is preferred as the sugar alcohol, and linear paraffin is preferred as the paraffin. Others include mannitol, galactitol, xylitol, and sorbitol. Sugar alcohols such as phosphates, inorganic salts such as inorganic phosphates, branched paraffins, inorganic hydrates, etc., can be used as the phase change material 200.

[0028] (3) Manufacturing method The heat storage body 1 can be synthesized by mixing a predetermined amount of liquid phase change material 200L, which has been melted by heating it above its melting point, with a predetermined amount of spherical silica porous body 100. The liquid phase change material 200L is introduced into the pores 10 of the spherical silica porous body 100 by capillary force and is held there.

[0029] In the heat storage body 1 of this embodiment, since the multiple pores 10 are arranged radially from the center toward the surface of the spherical silica porous body 100, for example, compared to the honeycomb-shaped silica porous body described in Non-Patent Literature 1, one end of the pores 10 is not open, thus suppressing leakage of the phase change material 200. Furthermore, since the shape of the pores 10 is substantially cylindrical, the phase change material 200 is held by capillary force, and even if it liquefies due to melting, leakage to the outside can be suppressed, improving the stability of retention.

[0030] Furthermore, in the heat storage body 1, the central pore diameter of the multiple pores 10 is between 1 nm and 20 nm. If the diameter of the pores 10 of the spherical silica porous body 100 is too small, it becomes difficult to introduce the phase change material 200. Also, since the introduction of the phase change material 200 into the pores 10 of the spherical silica porous body 100 is performed using the capillary force of the pores 10, if the diameter of the pores 10 of the spherical silica porous body 100 is too large, the capillary force will not work effectively, and the phase change material 200 will not be sufficiently filled. If the amount of phase change material 200 filled is insufficient, the amount of heat stored by the heat storage body 1 will be small. In contrast, according to the heat storage body 1 of this embodiment, since the central pore diameter of the pores 10 of the spherical silica porous body 100 is between 1 nm and 20 nm, a sufficient amount of phase change material 200 is filled, and the heat storage performance of the heat storage body 1 can be improved.

[0031] The heat storage body 1 of this embodiment has a spherical silica porous body 100 having highly regular pores 10. Silica has better thermal conductivity than the phase change material, and heat is easily transferred from the spherical silica porous body 100 to the phase change material. Because the spherical silica porous body 100 has highly regular pores 10, the phase change material can be introduced uniformly, and the thermal conductivity from silica to the phase change material can be improved. As a result, the degree of supercooling of the phase change material can be reduced, and the decrease in the amount of heat stored can be suppressed.

[0032] The heat storage body 1 of this embodiment can be used, for example, to regulate the temperature of clothing, building materials, and automotive components. For example, in electric vehicles, the heat storage body 1 can be used to cool the battery by filling the area around the battery pack. [Examples]

[0033] The present invention will be further described in detail by Examples 1-6 and Comparative Examples 1-3, but the present invention is not limited to the following examples. Both the examples and comparative examples are heat storage bodies in which a phase change material is filled into the pores of a spherical silica porous body. The examples and comparative examples differ in the pore diameter of the spherical silica porous body. The spherical silica porous body in the examples is the spherical silica porous body 100 (Figure 2) described in the above embodiment. Examples 1-3 and Comparative Examples 1 and 2 used erythritol as the phase change material, while Examples 4-6 and Comparative Example 3 used linear paraffin (RT90HC, supplier: Rubizerm GmbH) as the phase change material.

[0034] Figure 3 is a conceptual diagram illustrating the manufacturing method of the spherical silica porous body 100B used in Examples 2 and 5. Figure 4 is a conceptual diagram illustrating the manufacturing method of the spherical silica porous body 100C used in Examples 3 and 6. Figure 5 is a conceptual diagram illustrating the manufacturing method of the spherical silica porous body 100D used in Comparative Example 2. Figures 3 and 4 are similar to Figure 1. Similarly, a portion of the spherical silica porous body is cut out to illustrate its internal structure. Figure 5 shows a cross-section of the spherical silica porous body, which has been cut in half.

[0035] The spherical silica porous materials of Examples 2, 3, 5, 6 and Comparative Examples 1-3 were obtained by treating the spherical silica porous materials of Examples 1 and 4 (before surfactant removal) with the pore size enlarged, referring to Japanese Patent Publication No. 2011-111332 and Japanese Patent Publication No. 2007-45701.

[0036] The spherical silica porous body 100A used in Examples 1 and 4 was synthesized by the method described in Japanese Patent No. 5480461, with the surfactant changed from hexadecyltrimethylammonium chloride (C16Cl) to octadecyltrimethylammonium chloride (C18Cl). The surfactant 12A remaining in the pores 10A of the spherical silica porous body 100A is C18Cl. The central pore diameter of the pores of the spherical silica porous body 100A is 2.0 nm (details will be provided later). The surfactant was removed from the synthesized spherical silica porous body 100A by calcining at 550°C for 8 hours, and then a phase change material was introduced into the pores. Similarly, in the examples and comparative examples described below, surfactants and other substances used to enlarge the pore size were removed.

[0037] The spherical silica porous material 100B used in Examples 2 and 5 was formed by treating the spherical silica porous material 100A (before surfactant removal) to enlarge the diameter of the pores 10A and create pores 10B, as shown in Figure 3. Specifically, 1.0 g of spherical silica porous material 100A was mixed / dispersed with 2.26 g of swelling agent 14 (trimethylbenzene, TMB), 30 cc of ethanol, and 30 cc of pure water, and held at 100°C for three days. The pore diameter expanded to 7.1 nm as TMB penetrated the hydrophobic portion of the surfactant.

[0038] The spherical silica porous material 100C used in Examples 3 and 6 was formed by treating the spherical silica porous material 100A (before surfactant removal) to enlarge the diameter of the pores 10A and create pores 10C, as shown in Figure 4. Specifically, 1.0 g of spherical silica porous material 100A was mixed / dispersed with 3.03 g of surfactant (C22(behenic acid) TMACl(Tetramethylammonium chloride)), 30 cc of ethanol, and 30 cc of pure water, and held at 80°C for one week. The pore diameter was enlarged to 3.5 nm by the substitution of surfactant 12C (C22 TMACl) with surfactant 12A (C18Cl).

[0039] The spherical silica porous materials used in Comparative Examples 1 and 3 were subjected to a treatment similar to that used in Examples 2 and 5, by which the diameter of the pores 10A was enlarged by treating the spherical silica porous material 100A (before surfactant removal). However, while the spherical silica porous material 100B used in Examples 2 and 5 was held at 100°C for three days, the spherical silica porous materials used in Comparative Examples 1 and 3 were held at 100°C for one week. As a result, although the pore diameter of the central pore expanded to 2.4 nm, it became non-uniform. In other words, the multiple pores of the spherical silica porous materials used in Comparative Examples 1 and 3 had low regularity.

[0040] As shown in Figure 5, the spherical silica porous material 100D used in Comparative Example 2 was subjected to a treatment that enlarged the diameter of the pores 10A by treating the spherical silica porous material 100A (before surfactant removal). Specifically, 30 g of HCl at a concentration of 2.0 mol / l was mixed / dispersed with 1.0 g of spherical silica porous material 100A and held at 120°C for three days. By hydrothermal treatment under acidic conditions, the honeycomb pores collapsed, and then silica nanoparticles were generated, with pores forming between the nanoparticles. The central pore diameter enlarged to 5.0 nm, but it was non-uniform. The pore shape of the spherical silica porous material 100D is not cylindrical, and the multiple pores are not arranged radially from the center of the spherical silica porous material toward the surface, and the pore diameter is not uniform. The multiple pores in the silica porous material 100D exhibit low regularity.

[0041] Figures 6 and 7 are SEM (Scanning Electron Microscope) images of the spherical silica porous material 100 used in the heat storage body of the example. Figure 8 is an SEM image of the spherical silica porous material used in the heat storage body of the comparative example. Figures 8 and 7 show the average particle diameter and monodispersity of the spherical silica porous material. The average particle diameter was calculated by measuring the diameter of 200 particles using the SEM images and using the arithmetic mean. The monodispersity [%] was calculated by dividing the standard deviation of the particle diameter by the average particle diameter.

[0042] As shown in Figures 6 to 8, the average particle size of the spherical silica porous material used in the heat storage bodies of the examples and comparative examples is approximately 1 μm, and the monodispersity is approximately 7 to 11%, indicating that the particles are uniform.

[0043] Figure 9 shows the nitrogen adsorption isotherms of the spherical silica porous material used in the heat storage bodies of the examples and comparative examples. Figure 10 shows the pore size distribution curves of the spherical silica porous material used in the heat storage bodies of the examples and comparative examples.

[0044] The pore size distribution curves shown in Figure 10 were estimated from the measured nitrogen adsorption isotherms (Figure 9) using the BJH (Barrett, Joyner, and Halenda) method. As shown in Figure 9, in all pore expansion methods, the rise of the nitrogen adsorption isotherm shifted to the high relative pressure side, indicating pore expansion. Furthermore, as shown in Figure 10, in Examples 2, 5 and 3, 6, the shape of the distribution curve did not change, but the position of the peak top shifted to the larger pore size side, indicating that the pores expanded while maintaining pore regularity. On the other hand, in Comparative Examples 1, 3 and 2, although the pore size expanded, the expanded pore size had a wide distribution, indicating a loss of regularity. Hereafter, this pore regularity will be expressed as high / low.

[0045] As shown in Figure 10, the central pore diameter of the spherical silica porous bodies in Examples 1 and 4 is 2.0 nm, with a standard deviation of 10%. The central pore diameter of the spherical silica porous bodies in Examples 2 and 5 is 7.1 nm, with a standard deviation of 20%. The central pore diameter of the spherical silica porous bodies in Examples 3 and 6 is 3.5 nm, with a standard deviation of 13%. The central pore diameter of the spherical silica porous bodies in Comparative Examples 1 and 3 is 2.4 nm, with a standard deviation of 55%. The central pore diameter of the spherical silica porous body in Comparative Example 2 is 5.0 nm, with a standard deviation of 60%. The multiple pores in the spherical silica porous bodies of the examples show a high degree of regularity, as the standard deviation of the pore diameter distribution curve in the range where the pore diameter is greater than 1 nm is within 25% of the central pore diameter.

[0046] FIG. 11 is a diagram showing the physical properties of the phase change materials used in the examples and comparative examples. FIG. 11 shows the material manufacturer's property values. As shown in the figure, although erythritol has a high heat storage density, it has a high degree of supercooling, and linear paraffin has a small degree of supercooling.

[0047] FIG. 12 is a diagram showing the pore specifications of the heat storage bodies and the amount of the phase change material (erythritol) in the examples and comparative examples. FIG. 13 is a diagram showing the pore specifications of the heat storage bodies and the amount of the phase change material (linear paraffin) in the examples and comparative examples.

[0048] In FIGS. 12 and 13, the pore volume [ml / g] and the specific surface area [m 2 / g] were estimated from the measured nitrogen adsorption isotherm (FIG. 9) by a BET (Brunauer, Emmett, and Teller) plot. The pore size distribution curve was estimated by the BJH method, and the central pore diameter [nm] was obtained. The specific surface area [m 2 / m 3 is the specific surface area per unit pore volume and is calculated from the pore volume [ml / g] and the specific surface area [m 2 / g].

[0049] The filling rate represents the ratio occupied by the introduced phase change material (hereinafter also referred to as "PCM") in the total pore volume and can be estimated from thermogravimetry-differential thermal simultaneous measurement (TG-DTA: Thermogravimetry―Differential Theremal Analysis). In this example, measurement was carried out using a thermogravimetry-differential thermal simultaneous measurement device Thermoplus TG-8120 (manufactured by RIGAKU).

[0050] FIG. 14 is a diagram showing the TGA (Thermogravimetric analysis) curve of the phase change material. The weight loss at 150 to 700 °C was used as the organic fraction derived from the PCM, and the filling rate of the PCM in the pores was calculated. Specifically, it was calculated by the following (Equation 1).

[0051] Packing density [vol%] = Organic fraction / PCM density / Pore volume × 100 … (Equation 1)

[0052] In a heat storage body, the PCM density of PCM held in the silica porous material can be measured, for example, by the following method: The PCM gas, which is evaporated by heating the heat storage body, can be calculated using mass information obtained by gas chromatography-mass spectrometry (GC / MS).

[0053] Figure 15 shows the DSC curves of phase-change materials. Figure 15(a) shows a typical differential scanning calorimetry (DSC) curve for erythritol, and Figure 11(b) shows a typical DSC curve for linear paraffin. As shown in the figure, the difference between the endothermic peak and the heat-releasing peak represents the degree of supercooling. Also, as shown in the figure, the peak area of ​​the endothermic curve (shown with hatching in the figure) corresponds to the amount of heat stored.

[0054] Effective heat storage material represents the proportion of PCM (polycrystalline polymer) occupying the pores that can generate latent heat through melting / solidification, and can be estimated by differential scanning calorimetry (DSC) (latent heat storage density [J / g]). In this example, differential scanning calorimetry was performed using a differential scanning calorimetry meter DSC Q1000 (manufactured by TA Instruments) under conditions of -20°C to 150°C with a heating / cooling rate of 10°C / min. On the other hand, ineffective heat storage material is the total PCM minus the effective heat storage material.

[0055] The effective heat storage material can be calculated using the following equations (2) and (3). Effective heat storage material [vol%] = Apparent latent heat / PCM latent heat × 100 … (Equation 2) Apparent latent heat = heat storage capacity / PCM density / pore capacity … (Equation 3)

[0056] Furthermore, differential scanning calorimetry was performed as described above to determine the melting point and degree of supercooling of the phase-change material, as shown in Figure 11.

[0057] Figure 16 shows the packing density and effective / ineffective heat storage ratio of erythritol. Figure 17 shows the packing density and effective / ineffective heat storage ratio of linear paraffin. As described above, in Figures 16 and 17, the example is described as having high pore regularity in the silica porous material, and the comparative example is described as having low pore regularity in the silica porous material. Figure 16 uses the data from Figure 12, and Figure 17 uses the data from Figure 13.

[0058] As shown in Figures 16 and 17, in the case of particles with high pore regularity (Example), regardless of the type of PCM, the PCM filling rate tends to decrease as the pore diameter increases. Furthermore, it can be seen that the proportion of effective heat storage material is larger in particles with high pore regularity (Example) compared to particles with low pore regularity (Comparative Example).

[0059] Figure 18 is a conceptual diagram illustrating the effective and ineffective heat storage molecules within the pores. Figure 19 is a conceptual diagram illustrating the relationship between the specific surface area per unit pore volume and the effective heat storage material. In the figure, the effective heat storage material molecules are hatched with diagonal lines sloping downwards to the right, and the ineffective heat storage material molecules are hatched with diagonal lines sloping upwards to the right.

[0060] The following three factors are considered to be the main factors influencing the amount of PCM introduced into the pores. (1) Pore regularity: It is presumed that the higher the pore regularity, the more uniformly capillary force acts, and the more uniformly PCM is introduced into the pores. (2) Specific surface area per unit pore volume [m²] 2 / m 3 PCM molecules close to the pore walls strongly interact with them and therefore cannot act as latent heat storage materials without melting / solidifying, making them highly likely to become ineffective heat storage materials (Figure 18). Therefore, it is inferred that a smaller specific surface area per unit pore volume reduces the proportion of pore walls and thus reduces the proportion of ineffective heat storage materials. For example, Figure 19(b) has a smaller specific surface area per unit pore volume than Figure 19(a). Therefore, the proportion of ineffective heat storage materials can be reduced. (3) Pore size: Since PCM is introduced using the capillary force of the pores, if the pore size is too large relative to the PCM molecule size, the capillary force may not work effectively.

[0061] Figure 20 is an explanatory diagram showing the dependence of erythritol's heat storage density on pore capacity. Figure 21 is an explanatory diagram showing the dependence of erythritol's heat storage density on specific surface area. Figures 20 and 21 show the heat storage density when erythritol is introduced into the pores of a silica porous material, using the data shown in Figure 12. In Figures 20 and 21, pore regularity is simply referred to as "regularity".

[0062] As shown in Figures 20 and 21, the heat storage density is significantly lower when pore regularity is low (comparative example) compared to when pore regularity is high (example). When comparing particles with high pore regularity (example), the heat storage density remained almost constant regardless of pore volume or specific surface area. This is thought to be because the pore diameter is large compared to the molecular size of erythritol, resulting in weaker capillary action and a decrease in the amount introduced into the pores.

[0063] Figure 22 is an explanatory diagram showing the dependence of the heat storage density of linear paraffin on pore capacity. Figure 23 is an explanatory diagram showing the dependence of the heat storage density of linear paraffin on specific surface area. Figures 22 and 23 show the heat storage density when linear paraffin is introduced into the pores of a silica porous material, using the data shown in Figure 13. In Figures 22 and 23, pore regularity is simply referred to as "regularity".

[0064] As shown in Figures 22 and 23, the heat storage density decreases significantly when pore regularity is low (comparative example) compared to when pore regularity is high (example). When comparing particles with high pore regularity (example), as the pore capacity (pore diameter) increases, and the specific surface area [m²] increases, the heat storage density decreases. 2 / m 3 As [ ] decreases, the heat storage density increases. As mentioned above, a smaller specific surface area per unit pore volume results in a smaller proportion of pore walls, which reduces the proportion of PCM molecules (ineffective heat storage material) adjacent to the pore walls, thus increasing the heat storage density.

[0065] When using linear paraffin as the phase change material, the pore volume must be 0.9 [ml / g] or more, and the specific surface area per unit pore volume must be 1.4 × 10⁻⁶. 9 [m 2 / m 3 Setting it to ] or less is preferable because it results in a heat storage density of 50 J / g or more (Figures 22 and 23).

[0066] As explained above, the heat storage material of this embodiment has a higher degree of pore regularity and the central pore diameter is between 1 nm and 20 nm, compared to the heat storage material of the comparative example. Therefore, the heat storage density can be improved and the heat storage performance can be improved.

[0067] The present invention has been described above based on embodiments and examples, but the implementation of the above embodiments The forms provided are for the purpose of facilitating the understanding of the present invention and do not limit it. The present invention may be modified and improved without departing from its spirit and claims, and equivalents thereof are included. Furthermore, any technical features not described herein as essential may be appropriately deleted. [Explanation of Symbols]

[0068] 1… Heat storage element 10, 10A, 10B, 10C… Pores 12, 12A, 12C…surfactants 100, 100A, 100B, 100C, 100D... Spherical porous silica 200, 200L, 200S… Phase change materials

Claims

1. A heat storage body having a spherical silica porous body in which a plurality of substantially cylindrical pores are formed, The spherical silica porous body has a phase change material in the plurality of pores, In the aforementioned spherical silica porous body, The plurality of pores have a uniform pore diameter, are connected to the central hollow portion of the spherical silica porous body, and are arranged radially from the hollow portion toward the surface. The central pore diameter of the plurality of pores is 1 nm or more and 20 nm or less. Heat storage device.

2. A heat storage body according to claim 1, The plurality of pores in the spherical silica porous body are The standard deviation of the pore size distribution curve in the range where the pore size is greater than 1 nm is within 25% of the central pore diameter. Heat storage device.

3. A heat storage body according to claim 1 or claim 2, The diameter of the spherical silica porous body is 10 nm or more and 3000 nm or less. Heat storage device.

4. A heat storage body according to any one of claims 1 to 3, The plurality of pores in the spherical silica porous body are The pore volume is 0.9 [ml / g] or more, and the specific surface area per unit pore volume is 1.4 × 10⁻⁶ 9 [m 2 / m 3 The following is true: Heat storage device.

5. A heat storage body according to any one of claims 1 to 4, The phase change material is at least one of a sugar alcohol and paraffin. Heat storage device.

Images