Tungsten-doped vanadium dioxide layer radiant heat management film

Abstract

A tungsten-doped vanadium dioxide layer radiant heat management film comprises a metal base layer; the tungsten-doped vanadium dioxide layer is arranged above the metal base layer; the first germanium layer is arranged above the tungsten-doped vanadium dioxide layer; the zinc sulfide layer is arranged above the germanium layer; the quasi-periodic structure layer is arranged above the zinc sulfide layer, and the quasi-periodic structure layer is formed by alternately stacking calcium fluoride layers and second germanium layers; through the room temperature phase change characteristic of the tungsten-doped vanadium dioxide layer, passive switching of the tungsten-doped vanadium dioxide layer radiant heat management film between relatively high emissivity cooling in the daytime and relatively low emissivity heat preservation at night is achieved. Through the room temperature phase change characteristic of W-VO2, passive switching between daytime high-emissivity cooling and night low-emissivity heat preservation is achieved, and the problems that in the prior art, a radiant heat management device is low in emissivity and cannot be manufactured on a large scale are solved.

Description

Technical Field

[0001] This invention belongs to the field of temperature control technology, and more specifically, relates to a tungsten-doped vanadium dioxide layer radiative heat management film. Background Technology

[0002] In recent years, researchers have designed and fabricated radiative cooling devices or nighttime thermal insulation devices through experiments or simulations, such as photonic crystals, optical composite metamaterials, and multi-level porous polymers. Due to the properties of these materials, the devices cannot be adjusted after design and can only achieve radiative cooling. Even at low temperatures, these devices continue to cool, increasing thermal insulation energy consumption. Therefore, researchers have begun designing radiative thermal management devices capable of dynamically adjusting emissivity to adapt to various radiative thermal management requirements.

[0003] Currently, radiative heat management devices are typically designed using methods such as wetting, mechanical methods, thermochromism, and electrochromism. Wetting places high demands on the materials, while mechanical and electrochromic methods require additional energy input. The emergence of thermochromic materials has solved these problems. Thermochromic materials can achieve passive regulation of thermal radiation, and among many materials, vanadium dioxide (VO2) has attracted considerable attention due to its unique thermal properties.

[0004] As a thermotropic phase change material, VO2 has a phase change temperature (Tc) of 341 K. Above Tc, VO2 exists in a metallic state; below Tc, it exists in a dielectric state. Due to its high phase change temperature, VO2 is often doped with elements such as molybdenum, tungsten, and / or strontium to lower it to near room temperature. In existing technologies, some researchers have designed pyramidal structures based on vanadium dioxide. While these structures achieve a radiative cooling efficiency of 97%, the use of metasurface structures limits their practical application in daily life. Other researchers have designed intelligent heat sinks based on Fabry-Perot cavities, but their emissivity is only 0.7917. Still others have proposed a selective emitter capable of day-night switching, enabling all-weather radiative heat management, but its emissivity is less than 80%. Summary of the Invention

[0005] (a) Technical issues Through research on existing technologies, although the current design achieves all-weather radiative heat management, it still has problems such as low emissivity and inability to be mass-produced.

[0006] (II) Technical Solution To address the above problems, this invention proposes a radiative thermal management film based on a tungsten-doped vanadium dioxide thin film with a periodic structure, aiming to solve the problems of low emissivity and inability to mass-produce existing radiative thermal management devices.

[0007] This invention provides a tungsten-doped vanadium dioxide layer radiative thermal management film, which comprises: Metal base layer; A tungsten-doped vanadium dioxide layer disposed above the metal substrate; A first germanium layer disposed above the tungsten-doped vanadium dioxide layer; A zinc sulfide layer disposed above the germanium layer; And, a quasi-periodic structure layer disposed above the zinc sulfide layer, the quasi-periodic structure layer being formed by alternating layers of calcium fluoride layer and second germanium layer; The room-temperature phase transition characteristics of the tungsten-doped vanadium dioxide layer are used to achieve passive switching between cooling at relatively high emissivity during the day and heat preservation at relatively low emissivity at night for the radiative thermal management film of the tungsten-doped vanadium dioxide layer.

[0008] Preferably, in the tungsten-doped vanadium dioxide layer radiative heat management thin film provided by the present invention, when the structural temperature of the tungsten-doped vanadium dioxide layer is T>22℃, the tungsten-doped vanadium dioxide layer is in a metallic state; when the structural temperature of the tungsten-doped vanadium dioxide layer is 19℃≤T≤22℃, the tungsten-doped vanadium dioxide layer is in a transition state; and when the structural temperature of the tungsten-doped vanadium dioxide layer is T<19℃, the tungsten-doped vanadium dioxide layer is in an insulating state.

[0009] Preferably, in the tungsten-doped vanadium dioxide layer radiation heat management thin film provided by the present invention, the bottom layer of the quasi-periodic structure layer is a calcium fluoride layer, and the top layer of the quasi-periodic structure layer is a calcium fluoride layer.

[0010] Preferably, in the tungsten-doped vanadium dioxide layer radiative thermal management thin film provided by the present invention, in the quasi-periodic structure layer, the thickness of each calcium fluoride layer is consistent, and the thickness of each second germanium layer is consistent.

[0011] Preferably, in the tungsten-doped vanadium dioxide radiative thermal management thin film provided by the present invention, the thickness of the calcium fluoride layer is h1, the thickness of the second germanium layer is h2, the thickness of the zinc sulfide layer is h3, the thickness of the first germanium layer is h4, the thickness of the tungsten-doped vanadium dioxide layer is h5, and the thickness of the metal substrate is h6; wherein, the value of h1 ranges from [value missing]. The range of values ​​for h2 is: The range of values ​​for h3 is: The range of values ​​for h4 is: The range of values ​​for h5 is: The range of values ​​for h6 is: .

[0012] Preferably, in the tungsten-doped vanadium dioxide radiative thermal management thin film provided by the present invention, the number of calcium fluoride layers in the quasi-periodic structure layer ranges from 4 to 6.

[0013] Preferably, in the tungsten-doped vanadium dioxide layer radiative thermal management thin film provided by the present invention, the metal substrate is made of metallic silver.

[0014] Preferably, in the tungsten-doped vanadium dioxide layer radiation thermal management thin film provided by the present invention, a selective filtering structure layer with the function of reflecting solar radiation and transmitting thermal radiation is disposed above the quasi-periodic structure layer.

[0015] Preferably, in the tungsten-doped vanadium dioxide layer radiative thermal management thin film provided by the present invention, the selective filtering structure layer is a multilayer film structure, and the number of layers in the multilayer film structure ranges from 20 to 24.

[0016] Preferably, in the tungsten-doped vanadium dioxide layer radiative thermal management film provided by the present invention, the usable angle range between the tungsten-doped vanadium dioxide layer radiative thermal management film and the horizontal plane is 0°-60°.

[0017] (III) Beneficial Effects As described above, the present invention provides a tungsten-doped vanadium dioxide layer radiative thermal management film. In this invention, the tungsten-doped vanadium dioxide layer radiative thermal management film has the following structure: a metal substrate; a tungsten-doped vanadium dioxide layer disposed above the metal substrate; a first germanium layer disposed above the tungsten-doped vanadium dioxide layer; a zinc sulfide layer disposed above the germanium layer; and a quasi-periodic structure layer disposed above the zinc sulfide layer, the quasi-periodic structure layer being formed by alternating layers of a calcium fluoride layer and a second germanium layer; the room-temperature phase transition characteristics of the tungsten-doped vanadium dioxide layer are used to achieve a passive switching between cooling at relatively high emissivity during the day and maintaining heat at relatively low emissivity at night.

[0018] Through the above structural design, the tungsten-doped vanadium dioxide (W-VO2) radiative thermal management film provided by this invention exhibits metallic properties during daytime operation (above the phase transition temperature (Tc), resulting in high emissivity and enhanced radiative cooling power for superior heat dissipation. Conversely, at night when the temperature is below the phase transition temperature (Tc), the W-VO2 layer reverts to its dielectric state, exhibiting low emissivity, thus promoting thermal insulation. This invention utilizes the room-temperature phase transition characteristics of W-VO2 to achieve a passive switching between high-emissivity cooling during the day and low-emissivity insulation at night, solving the problems of low emissivity and limited mass production in existing radiative thermal management devices. This invention has broad application prospects in building energy conservation, infrared camouflage, and adaptive thermal management. Attached Figure Description

[0019] Figure 1a The diagram shows the operation mode of the tungsten-doped vanadium dioxide layer radiation heat management film provided by the present invention during the day and at night; exist Figure 1a The top image shows the daytime operation mode, and the bottom image shows the nighttime operation mode; meanwhile, in Figure 1a The paper also shows the radiative heat exchange diagrams of the tungsten-doped vanadium dioxide radiative heat management thin film at high and low temperatures; Figure 1b The optimal spectral emissivity characteristics of the tungsten-doped vanadium dioxide radiation thermal management thin film provided by the present invention under radiation cooling conditions are shown in the figure. Figure 1c The optimal spectral emissivity distribution of the tungsten-doped vanadium dioxide layer radiation thermal management film provided by the present invention under radiation insulation conditions.

[0020] Figure 2 This is a simplified structural diagram of the tungsten-doped vanadium dioxide layer radiation heat management thin film provided by the present invention.

[0021] Figure 3 Including Figure 3 a to Figure 3 There are nine images in total, namely: Figure 3a is a perspective view of a tungsten-doped vanadium dioxide layer radiation heat management thin film provided in one embodiment of the present invention; Figure 3 b is a graph showing the emissivity of the tungsten-doped vanadium dioxide layer radiation thermal management thin film provided by the present invention in the solar radiation band; Figure 3 c is a graph showing the emissivity of the tungsten-doped vanadium dioxide layer radiation thermal management thin film provided by the present invention in the atmospheric window band. Figure 3 d is a schematic diagram of the selective filtering structure layer in an embodiment of the present invention; Figure 3 e is a graph of the spectral reflectance of the selective filtering structure layer in the solar spectrum in the embodiment of the present invention; Figure 3 f is a graph showing the spectral transmittance of the selective filtering structure layer in the solar spectrum in the embodiment of the present invention. Figure 3 g is a schematic diagram of the tungsten-doped vanadium dioxide layer radiation heat management film provided by the present invention having a selective filter structure layer on top; exist Figure 3 In g, the correspondence between component names and reference numerals in the attached drawings is as follows: 1. Metal substrate; 2. Tungsten-doped vanadium dioxide layer; 3. First germanium layer; 4. Zinc sulfide layer; 5. Calcium fluoride layer; 6. Second germanium layer; 7. Selective filter structure layer. Figure 3 h is an emissivity chart for the solar radiation band when the tungsten-doped vanadium dioxide layer radiation heat management film provided by the present invention has a selective filter structure layer on top; Figure 3 i represents the emissivity chart of the atmospheric window band when the tungsten-doped vanadium dioxide layer radiation heat management film provided by the present invention has a selective filter structure layer on top.

[0022] Figure 4a is a graph showing the spectral emissivity of the tungsten-doped vanadium dioxide layer in the metallic state in the radiative thermal management film of the tungsten-doped vanadium dioxide layer provided by the present invention. Figure 4b is a graph showing the spectral emissivity of the tungsten-doped vanadium dioxide layer in the dielectric state of the radiative thermal management thin film provided by the present invention.

[0023] Figure 5 shows the spectral emissivity of the tungsten-doped vanadium dioxide layer in the radiative thermal management film of the tungsten-doped vanadium dioxide layer in the metallic state at different thicknesses. exist Figure 5 middle, Figure 5 a corresponds to a thickness of h1. Figure 5 b corresponds to a thickness of h2. Figure 5 c corresponds to a thickness of h3. Figure 5 d corresponds to a thickness of h4. Figure 5 e corresponds to a thickness of h5. Figure 5 f corresponds to a thickness of h6.

[0024] Figure 6 shows the spectral emissivity of the tungsten-doped vanadium dioxide layer in the radiative thermal management film provided by the present invention at different thicknesses under dielectric conditions. exist Figure 6 middle, Figure 6 a corresponds to a thickness of h1. Figure 6 b corresponds to a thickness of h2. Figure 6 c corresponds to a thickness of h3. Figure 6 d corresponds to a thickness of h4. Figure 6 e corresponds to a thickness of h6. Figure 6 f corresponds to a thickness of h6.

[0025] Figure 7a is a graph showing the radiation power of the tungsten-doped vanadium dioxide layer radiation heat management film provided by the present invention at 22°C during the day. Figure 7b is a graph showing the radiation power of the tungsten-doped vanadium dioxide layer radiation heat management film provided by the present invention at 19°C at night.

[0026] Figure 8a shows the surface temperature curves of the tungsten-doped vanadium dioxide layer radiation heat management film and the emitter with SE and CTR characteristics provided by the present invention at 35°C during the day under different convective heat transfer coefficients. Figure 8b shows the surface temperature curves of the tungsten-doped vanadium dioxide layer radiation heat management film and the emitter with SE and CTR characteristics provided by the present invention at 19°C at night under different convective heat transfer coefficients.

[0027] Figure 9 is a graph showing the temperature T of the tungsten-doped vanadium dioxide radiative heat management film provided by the present invention versus the ambient temperature Tamb over a period of 24 hours.

[0028] exist Figure 9 In the diagram, the temperature T of the tungsten-doped vanadium dioxide radiative heat management film is represented by the red curve, while the ambient temperature Tamb is represented by the black curve. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0030] Furthermore, in the description of this invention, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," and "bottom," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and do not require the invention to be constructed and operated in a specific orientation; therefore, they should not be construed as limitations on the invention. The terms "connected" and "linked" used in this invention should be interpreted broadly. For example, they can refer to a fixed connection or a detachable connection; they can refer to a direct connection or an indirect connection through intermediate components. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0031] This invention provides a radiative thermal management thin film structure with a tungsten-doped vanadium dioxide layer and a quasi-periodic structure. The thin film structure provided by this invention is designed based on the thermal response phase transition characteristics of W-VO2 under natural environmental conditions. Simultaneously, by employing a quasi-periodic thin film structure, it achieves adjustable emissivity (self-adjusting with temperature changes), large-scale fabrication, and enhanced radiative cooling or thermal insulation performance.

[0032] The tungsten-doped vanadium dioxide layer radiation heat management film designed in this invention can operate above the phase transition temperature (T0). c During daytime operation, W-VO2 (i.e., the tungsten-doped vanadium dioxide layer in this invention) exhibits metallic properties, resulting in high emissivity and enhanced radiative cooling power for superior heat dissipation. Conversely, at night when temperatures are below the phase transition temperature (Tc), W-VO2 reverts to its dielectric state, exhibiting low emissivity, thus promoting thermal insulation. Overall, the tungsten-doped vanadium dioxide radiative thermal management film provided by this invention exhibits higher emissivity at higher daytime temperatures (compared to nighttime emissivity) and lower emissivity at lower nighttime temperatures (compared to daytime emissivity), while also demonstrating higher ductility and superior radiative cooling capability. In this invention, the tungsten-doped vanadium dioxide radiative thermal management film is a multilayer film structure. Due to its "thin film" structure design, it can be mass-produced. The aforementioned ductility does not refer to the tungsten-doped vanadium dioxide radiative thermal management film being stretchable, but rather to its ability to be fabricated over large areas.

[0033] The working principle of this invention is as follows.

[0034] As shown in Figure 1, in terms of radiative heat management, the solar reflectivity (in the solar radiation band (wavelength range of 0.3-2.5 μm) is... ) and longwave infrared (in the atmospheric window band (wavelength range of 8-13μm) Emissivity is the two most important parameters, representing solar irradiance and the ability to emit heat into outer space, respectively.

[0035] It is a measure of how much solar radiation a material reflects relative to the intensity of incident sunlight, and the formula is as follows: (1) In equation (1), λ is the wavelength. Typically, this is the AM 1.5G global solar intensity spectrum. Let dλ be the spectral reflectance of the material surface, and dλ be an integral over the specified wavelength band.

[0036] This refers to the property of a material to emit electromagnetic waves in the LWIR (Long Wave Infrared, referring to the electromagnetic spectrum band with wavelengths in the range of 8-13 μm) wavelength range, compared to a blackbody at room temperature. It is defined as follows: (2) In equation (2), It is the spectral intensity of the blackbody at the emitter temperature (T). It is the spectral emissivity of the emitter. Long-wave infrared emissivity is a physical quantity that characterizes the ability of an object to emit radiation in the long-wave infrared band (8-13 μm). It is the ratio of the radiative flux emitted by the object to the radiative flux emitted by a blackbody at the same temperature in the same band.

[0037] In equation (2), the numerator represents the radiative flux emitted by the object in the 8-13 μm band, which is related to temperature and wavelength, and the denominator represents the radiative flux emitted by a blackbody at the same temperature in the 8-13 μm band.

[0038] In order for the tungsten-doped vanadium dioxide layer radiation heat management thin film provided by this invention to achieve high-temperature radiation cooling function, high... With high In order to achieve daytime cooling, a low temperature is required at night. To achieve nighttime heat preservation, since there is no sunlight at night, nighttime heat preservation is not considered. .

[0039] According to Kirchhoff's laws and Stefan-Boltzman's law, the absorptivity and emissivity of an object are equal. At room temperature, the object radiates radiation in the 8-14 μm band. Therefore, the structure designed in this invention needs to have a high absorptivity in the 8-14 μm band.

[0040] The following formula (3) is the Stefan-Boltzman law, and the system's emissivity is: (3) In equation (3), Tr, Rc and Rr represent the power transmission coefficient of the spectral filter, the power reflection coefficient of the top surface of the selective emitter and the power reflection coefficient of the bottom surface of the spectral selective filter, respectively.

[0041] In classical transmission line theory, the relationship between the thickness of the absorbing material and the reflection loss is revealed. As shown in Figure 2, the vertical incident reflection loss RL of a multilayer absorbing material with a metal plate as the substrate can be calculated from the relative complex permittivity and relative complex permeability of each layer and the thickness. The input impedance of the multilayer structure is obtained by iterating upwards from the bottom layer by layer.

[0042] exist Figure 2 In the middle, the normalized input impedance of the upper surface of RAM1 The complex relative permittivity of RAM1 at the operating frequency can be obtained from the following formula (…). ) and complex relative permeability ( The calculation yielded the following: (4) In equation (4), For RAM1, the normalized eigenwave impedance, parameters , For the thickness of RAM1, The incident wave frequency is c, and the speed of light is c. The normalized input impedance is surface-normalized on RAM2. The complex relative permittivity of RAM2 at the operating frequency can be obtained from the following formula. and complex relative permeability as well as The calculation shows that: (5) In equation (5), For RAM2, the normalized eigenwave impedance, parameters , The thickness of RAM2.

[0043] Referring to equations (4) and (5) above, iterate layer by layer from bottom to top. The input impedance of the top layer RAMn is the overall input impedance of the multilayer structure. The complex relative permittivity of RAMn at the operating frequency can be obtained from the following formula. and complex relative permeability as well as The calculation shows that: (6) In equation (6), For RAMn, the normalized eigenwave impedance, parameters , Let be the thickness of RAMn.

[0044] Equation (6) is the iterative calculation method for multilayer absorbing materials, which will be used later. replace This represents the normalized input impedance of the multilayer absorbing material. Represented in complex form as The real part and These represent the normalized input resistance and reactance, respectively.

[0045] The vertical incident reflection loss of the multilayer absorbing material is: (7) To minimize reflection loss, i.e., RL = -∞, the absorbing material needs to achieve perfect impedance matching. According to equation (7), this condition is related to the normalized resistance of the absorbing material. Equal to 1, normalized input reactance It is achieved when the value is equal to 0.

[0046] Since impedance is related to refractive index, impedance matching theory analysis shows that when the impedances of each layer are similar, i.e., when the refractive indices of each layer are similar, high absorption and low reflection can be achieved. Therefore, thermally induced phase-change tungsten-doped vanadium dioxide is chosen to achieve adjustable absorption. When tungsten-doped vanadium dioxide is in a metallic state, the impedances of each layer are matched, achieving high absorption and low reflection. When tungsten-doped vanadium dioxide is in a dielectric state, the impedances of the vanadium dioxide layer and other thin film layers are mismatched, achieving low absorption and high reflection.

[0047] Based on the above theoretical analysis, this invention designs a temperature-controlled tungsten-doped vanadium dioxide layer radiation thermal management film, wherein the upper film is a selectively permeable film (i.e., the selective filtering structure layer 7 in this invention), which only reflects the 0.3-2.5μm band and can transmit radiation in most atmospheric window bands.

[0048] Figure 3 (a) illustrates the tungsten-doped vanadium dioxide layer radiative thermal management film designed according to the present invention, and the overall structure of the tungsten-doped vanadium dioxide layer radiative thermal management film (e.g.) Figure 3 (From top to bottom) in a is CaF2 / Ge / CaF2 / Ge / CaF2 / Ge / CaF2 / ZNS / Ge / VO2 / Ag, with the thicknesses of each layer being h1=110nm, h2=45nm, h3=40nm, h4=350nm, h5=1000nm, and h6=100nm, respectively.

[0049] It should be noted that the metal substrate 1 in this invention is preferably silver, but it can also be replaced with other materials, such as stable metals like aluminum. The metal substrate 1 can increase the service life of the radiative heat management film of the tungsten-doped vanadium dioxide layer. The metal substrate 1 being set at the bottom layer can also reduce the light transmittance of the film.

[0050] Figure 3(b) The reflectivity of the selective emission film in the solar radiation band under high temperature conditions is given.

[0051] Figure 3 (c) shows the emissivity of the selective emission film under high and low temperature conditions.

[0052] Depend on Figure 3 (b) It can be seen that the reflectivity of the tungsten-doped vanadium dioxide radiative thermal management film provided by this invention is not high enough in the solar radiation band. Therefore, a spectrally selective filter structure layer is placed above the emission film to further improve the daytime radiative cooling performance of the structure. This selective filter structure layer is as follows: Figure 3 As shown in (d), this is a 22-layer film structure. This selective filtering structure layer reflects solar radiation and transmits thermal radiation. The number of selective filtering layers is fixed; through multiple designs by engineers, stacking the film to 22 layers achieves high reflectivity of visible light and high transmission of 8-13 micrometer light. Specifically, the selective filtering structure layer is composed of alternating layers of BF2 and ZnSe.

[0053] Depend on Figure 3 As shown in (e), the selective filtering structure layer has high reflectivity in the solar radiation band, which can prevent solar radiation from incident on the emitting film.

[0054] Depend on Figure 3 As shown in (f), the selective filtering structure layer has high transmission characteristics in the atmospheric window band, so it has little impact on the radiative heat transfer between the bottom radiative cooler and the external space.

[0055] Next, the selective filtering structure layer is combined as the upper layer and the selective emission layer as the lower layer, as follows: Figure 3 As shown in (g). When it is daytime and the temperature is above the W-VO2 phase transition temperature, as... Figure 3 (h) and Figure 3 As shown by the red line in (i), this structure exhibits high reflectivity in the solar radiation band and high emissivity in the atmospheric window band to achieve radiative cooling. When it is nighttime and the temperature is below the W-VO2 phase transition temperature, as... Figure 3 As shown in (i), the structure has a low emissivity in the atmospheric window band, which suppresses the outward radiation of heat from the object, thereby achieving a heat preservation effect at night.

[0056] To study the cooling and heat preservation effects of the thin film, this invention uses radiant power to represent its cooling and heat preservation capabilities. A positive radiant power indicates that the film achieves cooling, while a negative radiant power indicates heating. During the day, to evaluate the cooling flux of the tungsten-doped vanadium dioxide layer radiative heat management thin film, this invention simulates the radiant power of the tungsten-doped vanadium dioxide layer radiative heat management thin film by solving the heat balance equations considering blackbody radiation, solar irradiance, heat exchange with the atmosphere, and two other heat exchange channels. (8) At night, the radiative heat loss of an object at temperature T can be obtained using the following formula: (9) in, This indicates the temperature of the radiative thermal management thin film of the tungsten-doped vanadium dioxide layer. Indicates ambient temperature. This indicates the radiative flux emitted by the radiative thermal management thin film of the tungsten-doped vanadium dioxide layer at temperature. (10) in, Indicates wavelength. Indicates the polar angle, and It represents the angular integral over a hemisphere. The emissivity represents the structure's emissivity. According to Kirchhoff's laws, an object's absorptivity equals its emissivity. Due to VO2... Related to temperature, this invention uses replace .

[0057] (11) This formula represents temperature. The spectral radiance density of the lower blackbody, where Denotes Planck's constant. Represents the speed of light in space. This represents the Boltzmann constant. The heat flux representing the absorption of solar irradiance: (12) in The AM1.5 spectrum represents solar radiation. The heat flux absorbed by atmospheric heat exchange is expressed as: (13) in Represents the emissivity of the atmosphere, where This represents the atmospheric transmittance from the zenith. The last term relates to conduction and convection, as shown below: (14) in It represents the heat transfer coefficient (convective heat transfer coefficient) generated by conduction and convection.

[0058] Considering that the tungsten-doped vanadium dioxide layer radiative thermal management film provided in this invention needs to be used on a large scale as a smart wall, this invention needs to consider the tolerance of the tungsten-doped vanadium dioxide layer radiative thermal management film to large-angle incident light (the wall is vertical, and sunlight shines from top to bottom, forming an angle with the wall). Therefore, this invention further calculates the effect of the incident angle on the emissivity of the structure.

[0059] Figures 4(a) and (b) show the emissivity of the tungsten-doped vanadium dioxide radiative thermal management film in the metallic and dielectric states (metallic and dielectric states of the tungsten-doped vanadium dioxide layer), respectively. Figure 4(a) shows the spectral absorption at different incident angles in the metallic state. Figure 4(a) shows that the emissivity of the structure gradually decreases in the 0-60º range, but it still maintains high absorption in the atmospheric window band, thus still achieving radiative cooling. Figure 4(b) shows the spectral absorption at different incident angles in the dielectric state. Figure 4(b) shows that the emissivity of the structure gradually redshifts and increases in the 0-60º range, but it can be seen that its emissivity remains low at low temperatures, thus achieving low-temperature insulation.

[0060] To verify the robustness of the tungsten-doped vanadium dioxide layer radiation heat management film designed in this invention in further applications, this invention studies common manufacturing errors (such as the thickness of each layer of film) that may occur during the manufacturing process of the tungsten-doped vanadium dioxide layer radiation heat management film.

[0061] Because the upper layer of the tungsten-doped vanadium dioxide radiation heat management film designed in this invention adopts a periodic structure, the thickness of the Ge films in layers 2, 4, and 6 is studied uniformly. Simultaneously, this invention also conducts a uniform study on the CaF2 film (calcium fluoride layer). In the study, the thickness of each film layer is discussed from -10% to 10% (increasing or decreasing the thickness by 10%). Therefore, it can be found that when W-VO2 is in a metallic state at high temperatures, such as Figure 5 As shown in (a)-(e), when the thickness h1 of CaF2 varies from 40.5 to 49.5 nm, the emissivity of the structure gradually blue-shifts; when the thickness h2 of the top three Ge layers varies from 99 to 121 nm, the emissivity of the structure shows a red-shift trend; when the thickness h3 of ZnS varies from 36 to 44 nm, the emissivity of the structure does not change; when the thickness h4 of the bottom Ge layer varies from 315 to 385 nm, the emissivity of the structure gradually blue-shifts; when the thickness h5 of W-VO2 varies from 900 to 1100 nm, the emissivity of the structure hardly changes.

[0062] Based on the above result analysis, the present invention can draw the conclusion that the thickness change of Ge in contact with W-VO2 has the greatest impact on this structure, but the radiative cooling function can still be achieved. When W-VO2 is in the dielectric state at low temperature, as Figure 6 shown in (a)-(f), the thickness change of each layer has almost no effect on the emissivity, and the emissivity of this structure is always very low, and the heat preservation function can be achieved at low temperature.

[0063] When the structure temperature T > 22 °C, W-VO2 is in the metallic state; when T < 19 °C, W-VO2 is in the insulating state. The middle is the transition state of W-VO2 (the so-called transition state is the intermediate state of vanadium dioxide changing between the metallic state and the non-metallic state. There is a process from the non-metallic state to the metallic state, and this is the transition state). The present invention calculates the radiative power of W-VO2 in different hcc states, as shown in Fig. 7(a). When the structure temperature T reaches 22 °C, the total net radiative cooling flux is 91.69 W / m 2 . Fig. 7(B) shows the net heat loss at night, assuming the ambient temperature Tamb = 19 °C. When the object temperature T is lower than the phase change temperature, W-VO2 is in the insulating state, and the net heat loss of the structure is as low as 9.35 W / m 2 . It can be concluded that this thin film can achieve the cooling function at high temperature and the heat preservation function at low night temperature.

[0064] Compare the large structural scheme studied in the present invention with other thin film properties. First, the present invention defines the difference between the structure temperature T and the ambient temperature Tamb when Pnet = 0 as ΔT. Figure 6 Shows the temperature regulation effects of the thin film provided by the present invention during the day and at night, and compares it with a conventional temperature adaptive radiation (CTR) cooler without radiative heating effect and a temperature adaptive tungsten-doped vanadium dioxide layer radiative heat management thin film (SE). Under natural convection conditions (3 °C < hcc < 20 °C), the average temperature of this structure during the day is 6.5573 °C lower than Tamb. Among them, the average temperature of CTR during the day is 6.88 °C lower than Tamb, and the average temperature of SE during the day is 5.512 °C lower than Tamb. The cooling temperature of the structure of the present invention is only about 0.2 °C lower than that of the CTR structure. The results show that the structure proposed by the present invention has a good cooling effect during the day.

[0065] As shown in Figure 8(B), the average nighttime temperature of the structure is only 1.378℃ lower than that of Tamb. Specifically, the average nighttime temperature of CTR is 2.93℃ lower than that of Tamb, and the average daytime temperature of SE is 1.12℃ lower than that of Tamb. The nighttime temperature of the structure provided by this invention is approximately 0.25℃ lower than that of the SE structure. This demonstrates that the structure provided by this invention can achieve nighttime heat preservation. Temperature changes under different hcc values ​​indicate that this structure can effectively achieve daytime radiative cooling and nighttime radiative heating, thereby effectively reducing the diurnal temperature difference. The structure designed in this invention can switch between daytime radiative cooling and nighttime radiative heating. It was compared with other spectrally selective radiation systems, and the results are shown in Table 1. The table lists the radiation performance of different studies. Compared with existing structures, the cooling power of this invention (91.69 W / m²) is significantly higher. 2 The results show relatively impressive values. Furthermore, the invention demonstrates greater flexibility in temperature management and is better able to adapt to environmental requirements at different times of the day.

[0066] The performance comparison table of the multilayer film provided by this invention with two mainstream technologies (CTR cooler and SE tungsten-doped vanadium dioxide layer radiative thermal management film) is as follows: Taking the outdoor environmental conditions of a certain region in my country as an example, this invention studies the temperature variation of a tungsten-doped vanadium dioxide radiative thermal management thin film over time. Environmental temperature and solar radiation data from a specific day in 2020 were utilized. Figure 9 The simulated temperature changes of the tungsten-doped vanadium dioxide radiative thermal management thin film over a 24-hour period are shown. From early morning to 7 AM and after 8 PM, the ambient temperature Tamb decreases. When the VO2 temperature drops below Tc, the structure acts as an insulator, keeping its temperature close to ambient. From 10 AM to around 8 PM, Tamb rises, and when the VO2 temperature exceeds Tc, the structure enters a cooling state. The cooling effect is most pronounced at 1 PM, resulting in a temperature reduction of approximately 13°C. These data indicate that the thin film can significantly reduce indoor temperatures during the high temperatures of the day and effectively maintain indoor temperatures at night.

[0067] This invention proposes a quasi-periodic radiative thermal management thin film structure of tungsten-doped vanadium dioxide (W-VO2). The structure employs a design of "top-layer spectral selective filter - bottom-layer phase-change tungsten-doped vanadium dioxide radiative thermal management thin film," utilizing the room-temperature phase-change characteristics of W-VO2 to achieve passive switching between high-emissivity cooling during the day and low-emissivity heat preservation at night. This technology boasts high cooling power (91.69 W / m²). 2With its strong thermal insulation effect (temperature drop of only 1.378℃ at night), excellent angular stability (0°-60°), and manufacturing tolerance compatibility (±10% layer thickness deviation), it has broad application prospects in building energy conservation, infrared camouflage, adaptive thermal management and other fields.

[0068] As is known from common technical knowledge, this invention can be implemented through other embodiments that do not depart from its spirit or essential characteristics. Therefore, the disclosed embodiments described above are merely illustrative in all respects and are not the only ones. All modifications within the scope of this invention or its equivalents are included in this invention.

Claims

1. A tungsten-doped vanadium dioxide layer radiation heat management film, characterized in that, It comprises: a metal base layer (1); a tungsten-doped vanadium dioxide layer (2) disposed above the metal base layer; a first germanium layer (3) disposed above the tungsten-doped vanadium dioxide layer; a zinc sulfide layer (4) disposed above the germanium layer; and a quasi-periodic structure layer disposed above the zinc sulfide layer, which is formed by alternately stacking a calcium fluoride layer (5) and a second germanium layer (6); Through the room temperature phase transition characteristics of the tungsten-doped vanadium dioxide layer, the tungsten-doped vanadium dioxide layer radiation heat management film is used to realize passive switching of relatively high emissivity cooling during the day and relatively low emissivity insulation at night.

2. The tungsten-doped vanadium dioxide layer radiation heat management film according to claim 1, wherein: when the structure temperature of the tungsten-doped vanadium dioxide layer is T > 22℃, the tungsten-doped vanadium dioxide layer is in a metallic state; when the structure temperature of the tungsten-doped vanadium dioxide layer is 19℃≤T≤ 22℃, the tungsten-doped vanadium dioxide layer is in a transition state; and when the structure temperature of the tungsten-doped vanadium dioxide layer is T <19℃, the tungsten-doped vanadium dioxide layer is in an insulating state.

3. The tungsten-doped vanadium dioxide layer radiation heat management film according to claim 1, wherein: the bottommost layer of the quasi-periodic structure layer is a calcium fluoride layer, and the topmost layer of the quasi-periodic structure layer is a calcium fluoride layer.

4. The tungsten-doped vanadium dioxide layer radiation heat management film according to claim 3, wherein: in the quasi-periodic structure layer, the thickness of each calcium fluoride layer is consistent, and the thickness of each second germanium layer is consistent.

5. The tungsten-doped vanadium dioxide layer radiation heat management film according to claim 4, wherein: the thickness of the calcium fluoride layer is h1, the thickness of the second germanium layer is h2, the thickness of the zinc sulfide layer is h3, the thickness of the first germanium layer is h4, the thickness of the tungsten-doped vanadium dioxide layer is h5, and the thickness of the metal base layer is h6. Wherein, h1 is in the range of , h2 is in the range of , h3 is in the range of , h4 is in the range of , h5 is in the range of , h6 is in the range of .

6. The tungsten-doped vanadium dioxide layer radiation heat management film according to claim 1, wherein: in the quasi-periodic structure layer, the number of layers of the calcium fluoride ranges from 4 to 6.

7. The tungsten-doped vanadium dioxide layer radiation heat management film according to claim 1, wherein: the manufacturing material of the metal base layer is metal silver.

8. The tungsten-doped vanadium dioxide layer radiation heat management film according to claim 1, wherein: a selective filtering structure layer (7) with the functions of reflecting solar radiation and transmitting thermal radiation is disposed above the quasi-periodic structure layer.

9. The tungsten-doped vanadium dioxide layer radiation heat management film according to claim 8, wherein: the selective filtering structure layer is a multilayer film structure, and the number of layers of the multilayer film structure ranges from 20 to 24.

10. The tungsten-doped vanadium dioxide layer radiation heat management film according to any one of claims 1 to 9, wherein: the use angle range between the tungsten-doped vanadium dioxide layer radiation heat management film and the horizontal plane is 0°-60°.

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