A thermal insulation board based on a bionic butterfly light-trapping structure

Abstract

The present invention discloses a heat-insulating board based on a bionic butterfly light-trapping structure, belonging to the technical field of bionic materials. Inspired by the light-trapping structures on the lepidopteran surfaces of Kaniska canace and Papilio xuthus, two light-trapping structures are obtained therefrom, namely a ridge-type light-trapping structure or a grid groove light-trapping structure. Among them, the ridge-type light-trapping structure is composed of a plane and strip-shaped ridges protruding on the plane. The cross-section of the strip-shaped ridge is a trapezoid with a narrow upper base and a wide lower base. The width of the upper base of the trapezoid is 1.2 μm - 2.5 μm, the width of the lower base is 2 - 3.5 μm, the height is 2.4 μm - 3 μm, and the spacing between the ridges is 5 - 6 μm. The grid groove light-trapping structure is composed of an arrangement of a plurality of grid grooves. The shape of the grid groove is a frustum of a quadrangular pyramid. The cross-section of the grid groove is a trapezoid with a narrow upper base and a wide lower base. The width of the upper base is 0.6 μm to 0.8 μm, the width of the lower base is 0.3 μm to 0.4 μm, the height is 0.5 μm to 1 μm, and the groove interval is 0.1 μm. Through simulation tests, it is verified that its heat-insulating effect is significantly better than that of the existing heat-insulating wall body.

Description

Technical Field

[0001] The present invention belongs to the technical field of bionic materials, and particularly relates to a heat-insulating wall based on a bionic butterfly light-trapping structure. Background Art

[0002] Residential buildings, as the building type with the largest construction scale in China, account for an important proportion of energy consumption. China has a vast territory, and a large part of the territory is in cold regions, where a large amount of energy is continuously consumed for winter heating every year. Among residential buildings, the most heat loss occurs in the building envelope structure. Building walls are an important part of the building protection structure, and the heat loss caused by the exterior wall accounts for 40% of the total energy consumption of the envelope structure. Reducing the heat loss of the envelope structure and improving the heat insulation performance of the exterior wall are the most important energy-saving measures for residential buildings and are of great significance.

[0003] In the application of traditional heat-insulating walls, most still use ordinary concrete, which cannot effectively solve the cold bridge effect of wall panels. And due to insufficient research on mechanical efficiency, there is a lack of a quantitative relationship between the heat transfer coefficient and building energy consumption. In terms of the structural role of heat-insulating wall panels, they can be divided into three categories: internal insulation, external insulation, and sandwich insulation walls. Internal insulation building walls generally have problems such as easy damage to the internal insulation layer and being greatly affected by the indoor decoration environment. External insulation building walls have relatively serious problems such as poor fire resistance and poor durability. If the structure of the wall panel is improved, it is difficult to further improve the economic and energy-saving characteristics of the wall panel itself, and in most cases, it is not applicable to all types of buildings.

[0004] The light-trapping structure can also be called a "light trap". When light irradiates into this structure, through reflection, refraction, and scattering, the incident light is dispersed to various angles, thereby increasing the absorption of light energy by the structure. Currently, a large number of studies have found that introducing a light-trapping structure into a solar cell can effectively improve the short-circuit current and conversion efficiency of the solar cell. Through the observation of the butterfly lepidoptera in nature, it is found that the surface of the butterfly wings is distributed with micro-nano scale ridges and tower-shaped multi-layer physical structures, and different surface morphology models such as concave pit-shaped, ridge-shaped, and grid-shaped of butterfly scales are constructed to form a light-trapping structure. The light-trapping structure on the butterfly body surface can achieve photothermal conversion. Applying it to building heat-insulating wall panels through bionic methods can achieve the heat insulation of the wall, providing an important inspiration for further improving the economic and energy-saving characteristics of the wall panel itself.

[0005] Figure 1 、 Figure 2Scanning electron microscope images of Kaniska canace and Papilio xuthus respectively. It can be seen from the figure that the surfaces of the two butterflies have similar micro-nano scale multi-layer physical structures. On the left are the scanning electron microscope images of the wing surfaces of Kaniska canace and Papilio xuthus magnified 500 times respectively. It can be clearly observed that the wing surfaces of the butterflies are composed of neatly arranged scales. Further magnifying the scale structure, as shown on the right, the surface of the butterfly scales presents a regular strip-shaped ridge structure and there are porous groove structures distributed between the ridge structures. Inspired by this structure, the present invention designs a heat-insulating board based on the bionic butterfly light-trapping structure. Summary of the Invention

[0006] In order to solve the defects of poor heat insulation effect, easy damage, easy combustion, poor safety, poor versatility, etc. of traditional heat-insulating walls, and at the same time meet the national policy requirements of energy conservation and emission reduction, the present invention proposes a heat-insulating board based on the bionic butterfly light-trapping structure.

[0007] The technical solution adopted by the present invention is as follows:

[0008] In the heat-insulating board based on the bionic butterfly light-trapping structure of the present invention, its surface is provided with a bionic butterfly light-trapping structure, and the bionic butterfly light-trapping structure has two structures, namely a ridge-type light-trapping structure or a grid groove light-trapping structure;

[0009] Among them, the ridge-type light-trapping structure is composed of a plane and strip-shaped ridges protruding on the plane. The cross-section of the strip-shaped ridge is a trapezoid with a narrow upper base and a wide lower base. The width of the upper base of the trapezoid is 1.2 μm - 2.5 μm, the width of the lower base is 2 - 3.5 μm, the height is 2.4 μm - 3 μm, and the spacing between the ridges is 5 - 6 μm.

[0010] The grid groove light-trapping structure is composed of a plurality of grid grooves arranged. The shape of the grid groove is a frustum of a pyramid. The cross-section of the grid groove is a trapezoid with a wide upper base and a narrow lower base. The width of the upper base is 0.6 μm - 0.8 μm, the width of the lower base is 0.3 μm - 0.4 μm, the height is 0.5 μm - 1 μm, and the groove interval is 0.1 μm.

[0011] The material of the heat-insulating board is polystyrene or polyurethane material.

[0012] A heat-insulating wall body including the heat-insulating board based on the bionic butterfly light-trapping structure is composed of a concrete exterior wall 1, a heat-insulating board 2 based on the bionic butterfly light-trapping structure, and auxiliary fixing parts. The heat-insulating board 2 based on the bionic butterfly light-trapping structure is fixedly installed on the surface of the concrete exterior wall 1 through the auxiliary fixing parts.

[0013] Advantages of the present invention: Traditional thermal insulation wall panels mainly focus more on the thermal insulation effect and do not pay attention to building energy conservation and the impact on the environment. Structurally, they cannot well exert the thermal insulation effect, and it is difficult to meet the ideal standards in terms of mechanical properties and fire resistance. Wall cracking and frequent fire accidents often occur. Therefore, researching and developing new composite material wall panels and new structural wall panels based on traditional thermal insulation wall panels is a hot topic in current building wall research. In the process of researching new thermal insulation wall panels, the present invention also integrates the concept of natural bionics into them. By observing the surface of butterflies in nature, the light-trapping structure on the body surface of bionic butterflies is applied to the field of thermal insulation wall panels, improving the photo-thermal conversion effect of building thermal insulation wall panels and having great application value. Brief Description of the Drawings

[0014] Figure 1 Scanning electron microscope image of Kaniska canace

[0015] Figure 2 Scanning electron microscope image of Papilio xuthus

[0016] Figure 3 Schematic diagram of EPS / XPS / PUR thermal insulation wall

[0017] Schematic diagram of ridge-type light-trapping structure in Figure 4(a)

[0018] Ridge-type light-trapping structure in Example 1 in Figure 4(b)

[0019] Ridge-type light-trapping structure in Example 2 in Figure 4(c)

[0020] Schematic diagram of grid-groove light-trapping structure in Figure 5(a)

[0021] Top view of grid-groove light-trapping structure in Figure 5(b)

[0022] Grid-groove light-trapping structure in Example 3 in Figure 5(c) (A-A cross-sectional view)

[0023] Grid-groove light-trapping structure in Example 4 in Figure 5(d) (A-A cross-sectional view)

[0024] Figures 6(a) to 6(c) Structure of traditional thermal insulation board in the comparative example

[0025] Figures 7(a) to 7(e) Absorbance simulation test results of Examples 1 to 4 and the comparative example respectively (surface radiance (W / m 2 ))

[0026] Figures 8(a) to 8(e) Thermal energy simulation test results of Examples 1 to 4 and the comparative example respectively (temperature (K))

[0027] Figures 9(a) to 9(e)Thermal conductivity simulation test results of Examples 1 to 4 and the comparative example respectively (radiant heat flux (W / m 2 )) Detailed implementation manners

[0028] The technical solution of the present invention will be further explained and described below in the form of specific embodiments.

[0029] The heat-insulating wall structure based on the bionic butterfly light-trapping structure in the present invention is as Figure 3 shown, and is composed of a concrete exterior wall 1, a heat-insulating board 2 based on the bionic butterfly light-trapping structure, and auxiliary fixing parts. The heat-insulating board 2 based on the bionic butterfly light-trapping structure is fixedly installed on the surface of the concrete exterior wall 1 through the auxiliary fixing parts.

[0030] The heat-insulating board 2 based on the bionic butterfly light-trapping structure has a bionic butterfly light-trapping structure on its surface. The bionic butterfly light-trapping structure includes two structures, namely a ridge-type light-trapping structure or a grid groove light-trapping structure;

[0031] As shown in FIG. 4(a), the ridge-type light-trapping structure is composed of a plane and strip-shaped ridges protruding on the plane. The cross-section of the strip-shaped ridges is a trapezoid with a narrow upper base and a wide lower base. The width of the upper base of the trapezoid is 1.2 μm - 2.5 μm, the width of the lower base is 2 - 3.5 μm, the height is 2.4 μm - 3 μm, and the spacing between the ridges is 4 - 6 μm.

[0032] Example 1 (ridge-type light-trapping structure ①)

[0033] As shown in FIG. 4(b), in the cross-section of the strip-shaped ridges in this example, the width of the upper base of the trapezoid is 1.2 μm, the width of the lower base is 2 μm, and the height is 3 μm; the spacing between the ridges is 5.5 μm.

[0034] Example 2 (ridge-type light-trapping structure ②)

[0035] As shown in FIG. 4(c), in the cross-section of the strip-shaped ridges in this example, the width of the upper base of the trapezoid is 2.5 μm, the width of the lower base is 3.5 μm, and the height is 2.4 μm; the spacing between the ridges is 4 μm.

[0036] As shown in FIG. 5(a), the grid groove light-trapping structure is composed of a plurality of grid grooves arranged. The shape of the grid groove is a frustum of a pyramid. The cross-section of the grid groove is a trapezoid with a wide upper base and a narrow lower base. The width of the upper base is 0.6 μm - 0.8 μm, the width of the lower base is 0.3 μm - 0.4 μm, the height is 0.5 μm - 1 μm, and the groove interval is 0.1 μm.

[0037] Example 3 (grid groove light-trapping structure ①)

[0038] As shown in FIG. 5(c), in the cross-section of the grid groove in this example, the upper base of the trapezoid is 0.8 μm, the lower base is 0.3 μm; the height (i.e., the depth) is 0.5 μm, and the groove interval is 0.1 μm.

[0039] Example 4 (Grid Groove Light Trapping Structure ②)

[0040] As shown in Fig. 5(d), in the cross-section of the grid groove of this embodiment, the upper base of the trapezoid is 0.6 μm, the lower base is 0.4 μm, the height (i.e., the depth) is 1 μm, and the groove interval is 0.1 μm.

[0041] Comparative Example (Traditional Planar Structure)

[0042] As Figures 6(a) to 6(c) shown, the insulation board in this embodiment is a rectangular board with a length of 5 μm, a width of 2 μm, and a height of 0.5 μm.

[0043] Currently feasible preparation methods for this structure include: nanoimprinting technology, laser etching technology, etc.

[0044] Effect Verification

[0045] The main criterion for judging the heat insulation performance of the thermal insulation wallboard is the thermal conductivity. According to the "Technical Standard for External Thermal Insulation Engineering of Exterior Walls" (JGJ 144-2019), the average thermal conductivity of the insulation layer is:

[0046]

[0047] In the formula, ——Average thermal conductivity of the insulation layer; λ1——Thermal conductivity of the EPS board; λ2——Thermal conductivity of the plastering mortar; F1——Area of the EPS board; F2——Area of the plastering mortar at the joint.

[0048] For the cast-in-place concrete external thermal insulation system with EPS board, the cast-in-place concrete exterior wall should be used as the base wall, the EPS board should be used as the insulation layer, grooves should be opened on the inner surface (the surface in contact with the cast-in-place concrete) of the EPS board, and the interface mortar should be fully coated on both the inner and outer surfaces. During construction, the EPS board should be placed inside the outer formwork, and auxiliary fixing parts should be installed. A plastering mortar finishing layer should be applied on the surface of the EPS board, and the finishing layer should be filled with fiberglass mesh. The decorative layer can be paint or decorative mortar.

[0049] (2) Requirements for the thermal conductivity performance of the external thermal insulation of exterior walls are shown in Table 1.

[0050] Table 1

[0051]

[0052] At the same time, for the thermal conductivity formula:

[0053]

[0054] In the formula: Q——Heat; δ——Thickness; A——Area; ΔT——Temperature difference between the two end faces of the specimen.

[0055] Furthermore, for the heat flux density formula:

[0056]

[0057] In the formula:

[0058] q——heat flux density (heat flux).

[0059] Substituting the heat flux density into the thermal conductivity formula, we can obtain

[0060]

[0061] From this formula, it can be seen that the heat flux density is directly proportional to the thermal conductivity and inversely proportional to the temperature difference inside and outside. Therefore, for the heat insulation performance of the heat insulation wall panel, it is closely related to the heat flux of its structure and the temperature difference inside and outside. The smaller the heat flux, the better the heat insulation performance of the structure. As the temperature outside the external heat insulation wall panel rises, increasing the temperature difference ΔT inside and outside the heat insulation wall panel can also reduce the thermal conductivity λ. After obtaining the relationship between the thermal conductivity, heat flux, and temperature difference, the data sources required for the following bionic simulation analysis can be known.

[0062] To verify the effect, the present invention has carried out simulation tests on light absorption, thermal performance, and heat flux respectively. The test process and results are as follows:

[0063] 1. Light absorption test

[0064] Test method: Under the actual light source environment, the light irradiance obtained by different structures varies greatly. The present invention uses COMSOL software for light absorption simulation. First, set up and import the wall panel model, load various model materials, define the property, set the location of the environmental light source as Changchun Longjia Meteorological Station, the solar radiation as 1400W, and the light time as 12 hours. Using the surface radiation heat transfer module, add external natural convection heat exchange with parallel upper and lower plate surfaces in the solid heat transfer option, and add vertical external natural convection heat exchange on the side. The material type is solid, both the absolute pressure and the environmental temperature are set as the environment, and the initial value temperature is changed to the environmental temperature.

[0065] The results of Examples 1 to 4 and the comparative example are as Figures 7(a) to 7(e) shown, and the average surface light absorbance of the insulation board is as shown in the following table.

[0066] Table 2

[0067]

[0068] According to the simulation experiment data, the average surface light absorbance of the ridge-type light-trapping structure is increased by about 77W / m compared with the traditional flat structure 2 ; the average surface light absorbance of the grid groove light-trapping structure is increased by about 92W / m on average compared with the traditional flat heat insulation wall panel 2 .

[0069] 2. Thermal performance test

[0070] Under the same light source environment as the light absorption test, based on the test results of the wallboard irradiance, the amount of photothermal conversion heat obtained by the wallboard itself is analyzed through COMSOL software.

[0071] The results of Examples 1-4 and the comparative example are as Figures 8(a) to 8(e) shown. The average surface temperature of the insulation board is shown in the following table.

[0072] Table 3

[0073]

[0074] According to the simulation experiment data, the average surface temperature of the ridge-type light trapping structure is about 1.925 °C higher than that of the traditional flat structure; the average surface temperature of the grid groove light trapping structure is about 3.8 °C higher than that of the traditional flat structure.

[0075] 3. Heat transfer performance test

[0076] Sunlight irradiates an object through a medium. Most of the solar radiation energy is absorbed by the absorber, converted into heat energy and analyzed for heat. In the present invention, COMSOL software is used to evaluate the heat dissipation of different structure surfaces, and the higher the simulation value, the faster the heat dissipation.

[0077] The results of Examples 1-4 and the comparative example are as Figures 9(a) to 9(e) shown. The average heat flux of the insulation wallboard surface is shown in the following table.

[0078] Table 4

[0079]

[0080] According to the simulation experiment data, the average heat dissipation of the ridge-type light trapping structure surface is about 92 W / m 2 lower than that of the traditional flat structure; the average surface temperature of the grid groove light trapping structure is about 450.5 W / m 2 lower than that of the traditional flat structure. The experimental results show that the heat dissipation of the two light trapping structures is slower than that of the traditional flat structure.

[0081] From the above verified effects, it can be seen that the insulation effect of the insulation board proposed by the present invention is significantly better than that of the traditional insulation board.

Claims

1. A heat-insulating board based on a bionic butterfly light-trapping structure, characterized in that, The surface of the thermal insulation board is provided with a bionic butterfly light-trapping structure, and the bionic butterfly light-trapping structure is a ridge-type light-trapping structure or a grid groove light-trapping structure; Among them, the ridge-type light-trapping structure is composed of a plane and raised strip-shaped ridges on the plane. The cross-section of the strip-shaped ridges is a trapezoid with a narrow upper base and a wide lower base. The width of the upper base of the trapezoid is 1.2 μm - 2.5 μm, the width of the lower base is 2 - 3.5 μm, the height is 2.4 μm - 3 μm, and the distance between the ridges is 4 - 6 μm; The grid groove light-trapping structure is composed of the arrangement of a number of grid grooves. The shape of the grid groove is a frustum of a pyramid. The cross-section of the grid groove is a trapezoid with a wide upper base and a narrow lower base. The width of the upper base is 0.6 μm - 0.8 μm, the width of the lower base is 0.3 μm - 0.4 μm, the height is 0.5 μm - 1 μm, and the groove interval is 0.1 μm.

2. The heat preservation board based on the bionic butterfly light trapping structure according to claim 1, wherein In the cross-section of the strip-shaped ridge, the width of the upper base of the trapezoid is 1.2 μm, the width of the lower base is 2 μm, and the height is 3 μm; the distance between the ridges is 5.5 μm.

3. The heat-insulating board based on the bionic butterfly light-trapping structure according to claim 1, wherein In the cross-section of the strip-shaped ridge, the width of the upper base of the trapezoid is 2.5 μm, the width of the lower base is 3.5 μm, and the height is 2.4 μm; the distance between the ridges is 4 μm.

4. The heat preservation board based on the bionic butterfly light trapping structure according to claim 1, characterized in that, In the cross-section of the grid groove, the upper base of the trapezoid is 0.8 μm, the lower base is 0.3 μm; the height is 0.5 μm, and the groove interval is 0.1 μm.

5. The heat preservation board based on the bionic butterfly light trapping structure according to claim 1, wherein In the cross-section of the grid groove, the upper base of the trapezoid is 0.6 μm, the lower base is 0.4 μm; the height is 1 μm, and the groove interval is 0.1 μm.

6. The heat-insulating board based on the bionic butterfly light-trapping structure according to any one of claims 1 to 5, characterized in that The material of the thermal insulation board is polystyrene or polyurethane material.

7. A thermal insulation wall comprising the thermal insulation board with the bionic butterfly light trapping structure described in claim 1, characterized in that, The wall is composed of a concrete exterior wall (1), a thermal insulation board (2) based on the bionic butterfly light-trapping structure, and auxiliary fixing parts. The thermal insulation board (2) based on the bionic butterfly light-trapping structure is fixedly installed on the surface of the concrete exterior wall (1) through the auxiliary fixing parts.

Images