Cooling structure and manufacturing method of cooling structure

Abstract

To provide a cooling structure that has excellent weather resistance and can be realized by easy coating application, and a manufacturing method of the cooling structure.SOLUTION: A cooling structure includes an object to be cooled that is placed in a solar radiation environment, and a coating that is formed on a surface of the object to be cooled and contains ceramic particles. The ceramic particles have an average emissivity of 80% or more in a wavelength band of 8 to 13 μm, and an average reflectance of 80% or more in a wavelength band of 1 μm or less.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a cooling structure and a method for manufacturing a cooling structure. [Background technology]

[0002] For example, in facilities that house a variety of equipment, such as data centers, logistics warehouses, and factories, it is necessary to control the internal temperature within an appropriate range in order for the equipment to function properly. Conventionally, air conditioning equipment has often been used to control the temperature inside such facilities, but from the perspective of energy conservation and reducing environmental impact, new methods to replace air conditioning equipment are required.

[0003] As one of the means, a technology has been developed in recent years to improve cooling performance by applying a radiative cooling material to the exterior walls of the building in which the equipment is installed, thereby releasing the heat accumulated on the exterior walls due to sunlight to the outside. For example, Patent Document 1 proposes, as an example of this type of radiative cooling material, that a multi-layer coating made of a combination of multiple resin materials is applied to the surface of the object to be cooled, thereby obtaining good cooling performance in a sunshine environment through solar reflection and radiative cooling performance. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2021-143796 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the above Patent Document 1, a multilayer coating composed of a combination of multiple resin materials is used as a radiative cooling material. Since such a multilayer coating contains resin materials, its performance is likely to decrease or the coating is likely to peel off due to environmental degradation caused by ultraviolet rays contained in sunlight. In addition, in a structure formed in a sheet shape like a multilayer coating, application is not easy when the object to be cooled has a complex shape, and the cost is likely to be high.

[0006] At least one embodiment of the present disclosure has been made in consideration of the above-mentioned circumstances, and aims to provide a cooling structure that has excellent weather resistance and can be easily realized by coating application, and a method for manufacturing a cooling structure. [Means for solving the problem]

[0007] In order to solve the above problems, the cooling structure according to at least one embodiment of the present disclosure comprises: An object to be cooled that is placed in a solar radiation environment; A coating including ceramic particles formed on a surface of the object to be cooled; Equipped with The ceramic particles have an average emissivity of 80% or more in a wavelength band of 8 to 13 μm, and an average reflectance of 80% or more in a wavelength band of 1 μm or less.

[0008] In order to solve the above problems, a manufacturing method of a cooling structure according to at least one embodiment of the present disclosure includes: The method includes a step of forming a coating containing ceramic particles on a surface of an object to be cooled that is placed in a solar radiation environment, The ceramic particles have an average emissivity of 80% or more in a wavelength band of 8 to 13 μm, and an average reflectance of 80% or more in a wavelength band of 1 μm or less. Effect of the Invention

[0009] According to at least one embodiment of the present disclosure, it is possible to provide a cooling structure that has excellent weather resistance and can be realized by easy coating application, and a method for manufacturing the cooling structure. [Brief description of the drawings]

[0010] [Figure 1] FIG. 2 is a schematic configuration diagram showing a cooling structure according to one embodiment from the side; [Diagram 2] 2 is an example of the measurement results of the reflection characteristics of the thermal spray coating of yttria-stabilized zirconia contained in the coating of FIG. 1. [Diagram 3] 2 is an example of the measurement results of the radiation characteristics of the thermal spray coating of yttria-stabilized zirconia contained in the coating of FIG. 1. [Figure 4] FIG. 2 is a schematic diagram showing a verification test using a test specimen simulating the cooling structure of FIG. 1. [Diagram 5] These are the temperature measurement results for each sample of the test specimen. [Figure 6] FIG. 6 is an enlarged view of the vicinity of 14:00 in FIG. 5. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, some embodiments will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the configurations described as the embodiments or shown in the drawings are merely illustrative examples and are not intended to limit the scope of the invention.

[0012] 1 is a schematic diagram showing a cooling structure 10 according to one embodiment from the side. The cooling structure 10 includes an object to be cooled 12 that is placed in a solar radiation environment, and a coating 14 that is formed on the surface of the object to be cooled 12.

[0013] The object to be cooled 12 is, for example, an outer wall of a building equipped with equipment in a sunlit environment. In this embodiment, an outer wall facing upward is illustrated as the object to be cooled 12, but the object to be cooled 12 may face the other direction. The shape of the object to be cooled 12 shown in FIG. 1 is merely an example, and the object to be cooled 12 may have a more complicated shape, such as an uneven shape.

[0014] The coating 14 is provided so as to cover at least a portion of the surface of the object to be cooled 12. The coating 14 may be provided so as to cover the entire surface of the object to be cooled 12, or may be provided only on a portion of the surface.

[0015] The coating 14 includes ceramic particles. The ceramic particles included in the coating 14 have an average emissivity of 80% or more in a wavelength band of 8-13 μm and an average reflectance of 80% or more in a wavelength band of 1 μm or less. Specifically, the ceramic particles include a zirconia-based material, and more preferably, the zirconia-based material is yttria-stabilized zirconia.

[0016] 2 and 3, a description will be given of the characteristics of a thermally sprayed coating of yttria-stabilized zirconia, which is an example of the ceramic particles contained in coating 14. Fig. 2 shows an example of the measurement results of the reflection characteristics of the thermally sprayed coating of yttria-stabilized zirconia contained in coating 14 in Fig. 1, and Fig. 3 shows an example of the measurement results of the radiation characteristics of the thermally sprayed coating of yttria-stabilized zirconia contained in coating 14 in Fig. 1.

[0017] 2 shows the reflectance characteristics with respect to wavelength for each thickness of the coating 14 containing yttria-stabilized zirconia. As shown in FIG. 2, the coating 14 containing yttria-stabilized zirconia shows high reflectance in the wavelength range of 0.3 to 3 μm (see the hatched area in FIG. 2) at any thickness. It shows that the reflectance increases as the thickness of the coating 14 increases. This wavelength range corresponds to the wavelength range of the solar spectrum, and therefore shows that the coating 14 reflects solar light well, thereby making it difficult for the object to be cooled 12 covered with the coating 14 to heat up.

[0018] In Fig. 3, the emissivity characteristics with respect to wavelength are shown for each thickness of the coating 14 containing yttria-stabilized zirconia. As shown in Fig. 3, the coating 14 containing yttria-stabilized zirconia exhibits high emissivity in the wavelength range of 8 to 14 µm (see the hatched area in Fig. 3) at any thickness. It is shown that the emissivity increases as the thickness of the coating 14 decreases. This wavelength band corresponds to a wavelength band that is not absorbed by the atmosphere, and therefore is not easily absorbed by the atmosphere, which indicates that the object 12 covered by the coating 14 is easily cooled by the radiative cooling effect.

[0019] The wavelength range of 8 to 14 μm, which is not absorbed by the atmosphere, is known as the “atmospheric window.” In this wavelength range, a large amount of heat can be dissipated into space due to the large temperature difference with outer space, which is about -270°C.

[0020] In this way, by selecting an appropriate film thickness, yttria-stabilized zirconia can achieve both ideal reflection and radiation characteristics as a coolant. Therefore, by using yttria-stabilized zirconia as the ceramic particles contained in the coating 14, a good cooling effect can be obtained even in a single-layer configuration that can be easily applied. Specifically, in order to achieve an average reflectance of 80% or more in the wavelength band of 1 μm or less and an average emissivity of 80% or more in the wavelength band of 8-13 μm, in the case of a thermal spray coating, the film thickness is preferably about 0.3 to 0.5 mm.

[0021] Next, the results of a verification test on the cooling performance of the cooling structure 10 having the above configuration will be described. Fig. 4 is a schematic diagram showing the verification test using a test body 20 simulating the cooling structure of Fig. 1, Fig. 5 shows the temperature measurement results of each sample of the test body 20, and Fig. 6 is an enlarged view of Fig. 5 around 14:00. In addition to each sample, Figs. 5 and 6 also show, as reference data, the measurement results of a solid material with nothing applied to the surface of the metal box 28, a material with black paint applied, and the outside air temperature.

[0022] In this verification test, a test specimen 20 having the same configuration as the cooling structure 10 described above was used. As shown in FIG. 4, the test specimen 20 is constructed by laying, from the lower layer side, a urethane foam 24 and glass wool 26 in an acrylic box 22 having a hollow shape with an open top. A metal box 28 made of, for example, SUS is placed on the glass wool 26 as a simulated cooling target 12, and Samples 1 to 6 corresponding to the film 14 are provided on the upper surface of the metal box 28. The glass wool 26 is a heat insulating member for eliminating the thermal influence from the side of the acrylic box 22 on the metal box 28. Samples 1 to 6 are covered with a polyethylene film 30 along with the upper surface of the acrylic box 22 in order to eliminate the influence of convection.

[0023] Samples 1 to 3 are applied by thermal spraying and have different thicknesses t = 0.1, 0.3, and 0.5 mm. Sample 4 is applied by the sol-gel method and formed by spraying, drying, and firing. Sample 5 is applied by the sol-gel method and formed by spraying and drying (no firing). Sample 6 is applied by the sol-gel method and formed by brushing and drying.

[0024] As shown in Figures 5 and 6, Samples 1 to 6 all have lower surface temperatures than the black body and solid wood, and provide good cooling effects. Comparing the test results of Samples 1 to 13, it is shown that for the coating 14 applied by the thermal spraying method, the larger the film thickness t, the better the cooling effect. Also, Samples 4 to 6 have lower temperatures than Samples 1 to 3, which indicates that the coating 14 applied by the sol-gel method has better cooling effects than the thermal spraying method. Also, Sample 6 has the lowest temperature among Samples 4 to 6, which indicates that the sample that was applied by brushing and then dried provides the best cooling effect.

[0025] As described above, according to each of the above embodiments, the coating 14 containing ceramic particles is formed on the surface of the object to be cooled 12. The ceramic particles contained in the coating 14 have excellent emissivity in the 8-13 μm wavelength band that is highly transparent to the atmosphere (a wavelength band that is not absorbed by the atmosphere and corresponds to the so-called "atmospheric window"), and also have excellent reflectivity in a wavelength band of 1 μm or less that can effectively reflect the solar spectrum. By using a coating containing ceramic particles that have excellent reflectivity and emissivity for each wavelength band in this way, it is possible to effectively cool the object to be cooled 12.

[0026] In addition, within the scope of the present disclosure, the components in the above-described embodiments may be replaced with well-known components as appropriate, and the above-described embodiments may be combined as appropriate.

[0027] The contents described in each of the above embodiments can be understood, for example, as follows.

[0028] (1) A cooling structure according to one embodiment includes: An object to be cooled that is placed in a solar radiation environment; A coating including ceramic particles formed on a surface of the object to be cooled; Equipped with The ceramic particles have an average emissivity of 80% or more in a wavelength band of 8 to 13 μm, and an average reflectance of 80% or more in a wavelength band of 1 μm or less.

[0029] According to the above configuration (1), a coating containing ceramic particles is formed on the surface of the object to be cooled. The ceramic particles contained in the coating have excellent emissivity in the 8-13 μm wavelength band, which is highly transparent to the atmosphere (a wavelength band that is not absorbed by the atmosphere and corresponds to the so-called "atmospheric window"), and also have excellent reflectivity in a wavelength band of 1 μm or less that can effectively reflect the solar spectrum. By using a coating containing ceramic particles having excellent reflectivity and emissivity for each wavelength band, it is possible to effectively cool the object to be cooled.

[0030] (2) In another embodiment, in the above embodiment (1), The ceramic particles include a zirconia-based material.

[0031] According to the above aspect (2), by using a zirconia-based material as the ceramic particles contained in the coating, it is possible to realize excellent reflectance and emissivity for each of the above wavelength bands.

[0032] (3) In another embodiment, in the above embodiment (2), The zirconia-based material includes yttria-stabilized zirconia.

[0033] According to the above aspect (3), for example, yttria-stabilized zirconia can be used as the ceramic particles having excellent reflectance and emissivity in each of the above wavelength bands.

[0034] (4) In another embodiment, in any one of the above (1) to (3), The object to be cooled is an exterior wall of a building.

[0035] According to the above aspect (4), by applying the coating having the above configuration to the exterior wall of a building that is exposed to sunlight as an object to be cooled, a good cooling effect can be obtained.

[0036] (5) A method for manufacturing a cooling structure according to one embodiment includes the steps of: The method includes a step of forming a coating containing ceramic particles on a surface of an object to be cooled that is placed in a solar radiation environment, The ceramic particles have an average emissivity of 80% or more in a wavelength band of 8 to 13 μm, and an average reflectance of 80% or more in a wavelength band of 1 μm or less.

[0037] According to the above aspect (5), a coating containing ceramic particles is formed on the surface of an object to be cooled. The ceramic particles contained in the coating have excellent emissivity in the 8-13 μm wavelength band (a wavelength band that is not absorbed by the atmosphere, corresponding to the so-called "atmospheric window"), which is highly transparent to the atmosphere, and also have excellent reflectivity in a wavelength band of 1 μm or less that can effectively reflect the solar spectrum. By using a coating containing ceramic particles having excellent reflectivity and emissivity for each wavelength band, it is possible to effectively cool an object to be cooled.

[0038] (6) In another embodiment, in the above embodiment (5), The coating is formed by a sol-gel process.

[0039] According to the above aspect (6), the coating containing ceramic particles is applied to the surface of the object to be cooled by a sol-gel method, thereby exhibiting an excellent cooling effect.

[0040] (7) In another embodiment, in the above embodiment (5), The coating is formed by a thermal spraying method.

[0041] According to the above aspect (7), a coating containing ceramic particles is applied to the surface of an object to be cooled by a thermal spraying method. This results in a coating with superior adhesion and durability, although the cooling effect is inferior to that of the sol-gel method.

[0042] (8) In another embodiment, in the above embodiment (5), The coating is formed by a coating method or a spray method.

[0043] According to the above aspect (8), the coating containing ceramic particles is applied to the surface of the object to be cooled by a coating method or a spraying method, which requires simple equipment for application and allows the coating to be flexibly applied to the surface of objects to be cooled having various shapes. [Explanation of symbols]

[0044] 10 Cooling structure 12 Cooling object 14 Membrane 20 Test specimen 22 Acrylic Box 24 Urethane foam 26 Glass wool 28 metal box 30 Polyethylene film

Claims

1. An object to be cooled that is placed in a solar radiation environment; A coating including ceramic particles formed on a surface of the object to be cooled; Equipped with The ceramic particles have an average emissivity of 80% or more in a wavelength band of 8 to 13 μm, and an average reflectance of 80% or more in a wavelength band of 1 μm or less.

2. The cooling structure of claim 1 , wherein the ceramic particles comprise a zirconia-based material.

3. The cooling structure of claim 2 , wherein the zirconia-based material comprises yttria-stabilized zirconia.

4. The cooling structure according to claim 1 or 2, wherein the object to be cooled is an exterior wall of a building.

5. The method includes a step of forming a coating containing ceramic particles on a surface of an object to be cooled that is placed in a solar radiation environment, The ceramic particles have an average emissivity of 80% or more in a wavelength band of 8 to 13 μm and an average reflectance of 80% or more in a wavelength band of 1 μm or less.

6. The method for manufacturing a cooling structure according to claim 5 , wherein the coating is formed by a sol-gel method.

7. The method for manufacturing a cooling structure according to claim 5 , wherein the coating is formed by a thermal spraying method.

8. The method for manufacturing a cooling structure according to claim 5 , wherein the coating is formed by a coating method or a spray method.

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