Design method of heat-conductivity-adjustable heat-cloak based on neutral inclusion principle

Abstract

This invention relates to a design method for a thermally adjustable thermal stealth cloak based on the principle of neutral inclusions, belonging to the field of thermal technology. This invention solves the problems of existing thermal stealth cloak designs that rely on cumbersome methods for adjusting the thermal conductivity of the stealth layer using convection heat transfer to overcome the limitations of the background medium's thermal conductivity, and the numerous limitations imposed by the liquid phase medium during thermal conductivity adjustment. Based on the existing thermal stealth cloak structure, this invention adds a thermoelectric layer Zs between the thermal insulation layer Z2 and the stealth layer Z3. The temperature of the thermoelectric layer Zs is adjustable, and the thermoelectric layer Zs... S The equivalent thermal conductivity k* of the multi-layered structure interspersed region formed by the cloaking layer Z3 is the same as the thermal conductivity k4 of the background layer Z4, thus obtaining the thermal conductivity k3 of the cloaking layer Z3, making its k3 adjustable. This invention is mainly used to adjust the thermal conductivity of a thermal cloak.

Description

Technical Field

[0001] This invention belongs to the field of thermal technology. Background Technology

[0002] A thermal stealth cloak is a thermal functional device that blocks heat flow from entering its internal area, providing thermal protection for the target. Simultaneously, the thermal stealth cloak prevents the target from having any influence or disturbance on the external temperature field, making it impossible for observers to detect the presence and characteristics of the target inside the cloak through the external temperature distribution. Thermal stealth cloaks have broad application prospects in both military and civilian fields. Thermal stealth technology can be used to conceal military personnel and equipment or for thermal protection of devices such as chips. The main characteristics of a thermal stealth cloak are: 1) Heat flow cannot enter the stealth area, and there is no temperature gradient within the stealth area; 2) The target has no influence on the external temperature field of the thermal stealth cloak.

[0003] Traditional thermal stealth cloaks are typically designed based on transformational thermal methods. However, the thermal conductivity of the material in the resulting design area is non-uniform and anisotropic, and natural material properties cannot directly meet this requirement. Researchers have introduced topology optimization methods into thermal stealth cloak design. Topology optimization is highly adaptable and can be designed for different materials and geometries. However, the resulting geometric configurations are complex, difficult to process and fabricate, limiting their application. Therefore, some researchers have proposed scattering cancellation methods or neutral inclusion methods to design a simple, double-layer thermal stealth cloak. One layer is an insulating layer Z2 with a thermal conductivity of k2 = 0. The target is placed inside the insulating layer, which prevents heat flow from entering the target, achieving the thermal protection effect of the cloak. Therefore, the thermal conductivity k1 of the target can be any value. The other layer is a stealth layer Z3. The presence of the stealth layer Z3 allows Z2 and Z3 to constitute the entire thermal stealth system without disturbing the external temperature field; that is, the stealth layer achieves the non-invasive effect of the thermal cloak. The thermal conductivity of the stealth layer Z3 is determined by the following formula:

[0004]

[0005] In the formula, k4 represents the thermal conductivity of the background medium. The double-layer thermal cloak has a simple structure, requiring only isotropic and homogeneous materials, thus avoiding the need for anisotropic and non-homogeneous material parameters required by thermal cloaks. However, it can be seen from formula (1) that the double-layer thermal cloak requires the thermal conductivity of the design layer to be greater than that of the background medium, i.e., k3 > k4. Among common materials, the thermal conductivity generally does not exceed that of copper (thermal conductivity 400W). -1 m -1 K -1When the background medium is a material with the highest thermal conductivity, such as copper, no material can meet the required thermal conductivity k3 of the design layer, making a double-layer thermal stealth cloak impossible. Therefore, the challenge lies in achieving higher thermal conductivity (breaking through the 400W limit of common materials). -1 m -1 K -1 The application of double-layer thermal cloaks to background media with high thermal conductivity has become an urgent problem to be solved.

[0006] To achieve higher equivalent thermal conductivity, researchers have introduced convective heat transfer methods to actively control in-plane thermal conductivity. This approach typically involves replacing the design layer medium with a liquid (such as water) and rotating the liquid medium to increase convective heat transfer between the liquid and the surrounding environment, reducing in-plane thermal conductivity and thus achieving a higher equivalent thermal conductivity. However, this active control method requires external mechanical devices to rotate the liquid medium, and strict requirements are placed on the rotation angular velocity. For different boundary temperatures and different ambient temperatures, the rotation angular velocity needs to be recalculated and adjusted, which is very cumbersome. Furthermore, liquid phase media are difficult to store and prone to leakage, posing many limitations to their application. Therefore, establishing a new method for thermal conductivity adjustment that overcomes the limitations of the methods described above has become a critical bottleneck problem that urgently needs to be solved for thermal stealth cloaks. Summary of the Invention

[0007] To address the problems of existing thermal stealth cloak designs that rely on cumbersome methods for adjusting the thermal conductivity of the stealth layer using convection heat transfer to overcome the limitations of the background medium's thermal conductivity, and the numerous limitations imposed by the liquid phase medium during thermal conductivity adjustment, this invention provides a thermal stealth cloak design method based on the principle of neutral inclusions. This method overcomes the limitations of the background medium's thermal conductivity and allows for arbitrary adjustment of the stealth layer's thermal conductivity.

[0008] The thermal invisibility cloak design method based on the principle of neutral inclusion includes a thermal insulation layer Z2, an invisibility layer Z3 and a background layer Z4 distributed from the inside to the outside in the horizontal direction.

[0009] The thermal stealth cloak also includes a thermoelectric layer Zs, which is located between the thermal insulation layer Z2 and the stealth layer Z3. The thermal insulation layer Z2, the thermoelectric layer Zs, and the stealth layer Z3 are concentric, and the radial cross-sections of the thermoelectric layer Zs and the stealth layer Z3 are both annular. The radial cross-section of the thermal insulation layer Z2 is circular and is used to cover the target Z1.

[0010] Temperature control is applied to the thermoelectric layer Zs to make the thermoelectric layer Z S The equivalent thermal conductivity of the multi-layered structure mixed region formed by the stealth layer Z3 is k*=k4, and combined with The thermal conductivity of the stealth layer Z3 was obtained.

[0011] Where k4 is the thermal conductivity of the background layer Z4, R s R3 is the outer diameter of the thermoelectric layer Zs, and R3 is the outer diameter of the stealth layer Z3.

[0012] By adjusting R s By adjusting the values ​​of R3 and R3, the thermal conductivity k3 of the stealth layer Z3 can be adjusted, thus completing the design of a thermal stealth cloak with adjustable thermal conductivity.

[0013] Preferably, the temperature required for the thermoelectric layer Zs is...

[0014] Among them, T H and T L , respectively, are the boundary temperatures on the left and right sides of the background layer Z4, L is the length of the background layer Z4, and x0 is the abscissa of the center of the thermal insulation layer Z2 of the thermal cloak when a planar coordinate system is established with the lower left corner of the thermal cloak as the center.

[0015] Preferably, the heat flow J within the thermoelectric layer Zs, and between the thermoelectric layer Zs and the stealth layer Z3, is described by Fourier's law of heat transfer, expressed as: J = -k s ▽T;

[0016] Where, k s Let J be the thermal conductivity of the thermoelectric layer Zs, where J is a finite value, and ▽T be the temperature difference at the interface between the thermoelectric layer Zs and the stealth layer Z3, with ▽T approaching 0.

[0017] Preferably, the thermoelectric layer Zs is made of thermoelectric material.

[0018] Preferably, the thermoelectric layer Zs is used to connect to an external power source to achieve temperature control.

[0019] A computer-readable medium storing a computer program that, when executed, implements a method for designing a thermally conductive stealth cloak based on the principle of neutral inclusions.

[0020] An electronic device includes a storage device, a processor, and a computer program stored in the storage device and executable on the processor, wherein the processor executes the computer program to implement a thermally conductive cloak design method based on the principle of neutral inclusions.

[0021] Advantages of this invention:

[0022] The thermoelectric layer of this invention controls its temperature through external electric heating, achieving an infinitely high equivalent thermal conductivity. This is achieved by adjusting R... sBy adjusting the value of R3, the thermal conductivity k3 of the stealth layer Z3 can be adjusted. This invention provides a design method for a thermally adjustable stealth cloak based on the principle of neutral inclusion, breaking through the limitation of the thermal conductivity of the background medium.

[0023] The present invention has a simple structural design, is easy to process and manufacture, and has a simple temperature control method, requiring no mechanical adjustment such as rotation, and is not affected by ambient temperature.

[0024] In this invention, the thermal conductivity k3 of the stealth layer is less than the thermal conductivity k4 of the background layer, therefore, it is suitable for background media with high thermal conductivity.

[0025] In this invention, only the temperature of the thermoelectric layer Zs needs to be controlled; the material properties of the thermoelectric layer Zs are not required, and the temperature of the thermoelectric layer Zs can be controlled by an external voltage. The control method is simple, and common thermoelectric materials can be selected, such as bismuth telluride for a typical PN junction and copper or aluminum for the node. See [link to relevant documentation]. Figure 3 .

[0026] In this invention, the thermal conductivity k3 of the stealth layer can be adjusted by modifying geometric parameters. Adjustments can be made by modifying geometric parameters based on the given thermal conductivity properties of the material. Achieving thermal stealth requires minimal restrictions on material parameters and offers design flexibility. Attached Figure Description

[0027] Figure 1 The background diagram shows the layout of a traditional scattering-based heat-removing cloak.

[0028] Figure 2 This is a layout diagram of the thermally adjustable thermal stealth cloak based on the principle of neutral inclusion, as described in this invention.

[0029] Figure 3 This is a schematic diagram of the structure of a thermoelectric material formed by PN junction nodes;

[0030] Figure 4 The numerical simulation results are shown in the figure to verify the infinite thermal conductivity. Figure 4 Temperature field distribution diagram when the thermal conductivity of the central target body is set to infinity (a); Figure 4 b represents the temperature field distribution diagram when the thermal conductivity of the central target body is set to a finite value, but the target body temperature is set according to Formula 2. Figure 4 c represents the temperature field distribution diagram when the thermal conductivity of the central target body is set to a finite value and the temperature of the target body is not controlled.

[0031] Figure 5 This is a temperature field distribution diagram of the thermal cloak under different heat sources on the left and right sides when the temperature of the thermoelectric layer Zs is controlled under two-dimensional simulation conditions.

[0032] Figure 6 This is a temperature field distribution diagram of the thermal cloak on the left and right sides under two-dimensional simulation conditions, without temperature control of the thermoelectric layer Zs. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0035] This invention aims to overcome the limitations of background medium thermal conductivity, making the thermal cloak suitable for background media with high thermal conductivity. See [link to related document]. Figure 2 A specific implementation method is provided. This invention provides a design method for a thermally conductive stealth cloak based on the principle of neutral inclusion. The thermal stealth cloak includes a thermal insulation layer Z2, a stealth layer Z3, and a background layer Z4 distributed from the inside to the outside in the horizontal direction.

[0036] The thermal stealth cloak also includes a thermoelectric layer Zs, which is located between the thermal insulation layer Z2 and the stealth layer Z3. The thermal insulation layer Z2, the thermoelectric layer Zs, and the stealth layer Z3 are concentric, and the radial cross-sections of the thermoelectric layer Zs and the stealth layer Z3 are both annular. The radial cross-section of the thermal insulation layer Z2 is circular and is used to cover the target Z1.

[0037] Temperature control is applied to the thermoelectric layer Zs to make the thermoelectric layer Z S The equivalent thermal conductivity of the multi-layered structure mixed region formed by the stealth layer Z3 is k*=k4, and combined with The thermal conductivity of the stealth layer Z3 was obtained.

[0038] Where k4 is the thermal conductivity of the background layer Z4, R s R3 is the outer diameter of the thermoelectric layer Zs, and R3 is the outer diameter of the stealth layer Z3.

[0039] By adjusting R s By adjusting the values ​​of R3 and R3, the thermal conductivity k3 of the stealth layer Z3 can be adjusted, thus completing the design of a thermal stealth cloak with adjustable thermal conductivity.

[0040] Within the area where the thermal cloak is located, the area excluding the thermal insulation layer Z2, the thermoelectric layer Zs, and the cloaking layer Z3 is the background layer Z4.

[0041] The thermoelectric layer Zs is used to connect to an external power source for temperature control. Based on the Peltier effect, when an external voltage is applied to the thermoelectric layer Zs, its temperature can be actively controlled, and the temperature is uniformly distributed within the thermoelectric layer Zs. The relationship between the external voltage and the temperature of the thermoelectric layer Zs can be obtained as follows: Figure 3 In this process, an external voltage is applied, and the temperature of the thermoelectric layer Zs is measured using a thermocouple or infrared camera. The external voltage value is changed, and the process is repeated multiple times to establish the relationship between the external voltage and the temperature of the thermoelectric layer Zs.

[0042] In the design of a thermal stealth cloak, the temperature of the thermoelectric layer Zs is determined by the following formula:

[0043]

[0044] Among them, T H and T L , respectively, are the boundary temperatures on the left and right sides of the background layer Z4, L is the length of the background layer Z4, and x0 is the abscissa of the center of the thermal insulation layer Z2 of the thermal cloak when a planar coordinate system is established with the lower left corner of the thermal cloak as the center.

[0045] The heat flow J within the thermoelectric layer Zs, and between the thermoelectric layer Zs and the stealth layer Z3, is described by Fourier's law of heat transfer, which is expressed as:

[0046] J = -k s ▽T (3);

[0047] Where, k s Let J be the thermal conductivity of the thermoelectric layer Zs, where J is a finite value, and ▽T be the temperature difference at the interface between the thermoelectric layer Zs and the stealth layer Z3, with ▽T approaching 0.

[0048] When an external voltage is applied to the cloaking layer Z3, the temperature is uniformly distributed within Z3. Whether heat flows from the thermoelectric layer Zs to the cloaking layer Z3, or from the cloaking layer Z3 to the thermoelectric layer Zs, the temperature of the thermoelectric layer Zs and the cloaking layer Z3 are at the boundary r = R. s The temperatures at the boundary are equal, resulting in a temperature difference ▽T→0 at that boundary. Since the heat flux J in equation (3) is a finite value, the thermal conductivity of the thermoelectric layer Zs is equivalent to k S →+∞. In other words, by controlling the temperature of the thermoelectric layer Zs, making it equal to the inner boundary r = R of the stealth layer Z3. s The temperature at that point is equal, which is equivalent to making the thermal conductivity k of the thermoelectric layer Zs equal. S Its value is infinite, which breaks through the limitation of the thermal conductivity of natural materials.

[0049] The reliability of the method for obtaining infinite equivalent thermal conductivity is verified through the following numerical simulation. Figure 4 In the middle, the thermal conductivity of the background medium is 400W. -1 m-1 K -1 , Figure 4 In a, the thermal conductivity of the central target body is set to infinity; Figure 4 In b, the thermal conductivity of the target body is a finite value of 10 W -1 m -1 K -1 , but the temperature value of the target body is set according to Equation (2); Figure 4 In c, the thermal conductivity of the target body is a finite value of 10 W - 1 m -1 K -1 , and the temperature value of the target body is not controlled. By comparing Figure 4 a and Figure 4 b, it can be seen that for a target body with finite thermal conductivity, the temperature distribution of the entire system obtained after controlling the temperature of the target body is exactly the same as the temperature distribution of the target body with infinite thermal conductivity, indicating that at this time Figure 4 the thermal conductivity of the target body in b can be considered infinite. As a comparison, Figure 4 in c, the temperature of the target body is not controlled, and at this time, the temperature fields caused by the target body with finite thermal conductivity and the target body with infinite thermal conductivity are completely different. The above analysis shows that controlling the temperature of a certain region (the target body region in this example) according to Formula (2) can make the equivalent thermal conductivity of this region infinite. This result provides a basis for controlling the temperature of the thermoelectric material layer according to Formula (2) and making its equivalent thermal conductivity infinite in the present invention.

[0050] According to the principle of neutral inclusions, Figure 2 in it, the region where r < R3 (that is, the region composed of Z2, Zs, and Z3 as a whole) is regarded as a multi-layer structure inclusion region. When the equivalent thermal conductivity of the multi-layer structure inclusion region is the same as that of the background medium k4, the inclusion region does not cause disturbance to the temperature field of the background medium, that is, the non-invasive effect of the thermal cloaking is achieved. Since the thermal conductivity of the thermal insulation layer Z2 is 0, the thermal conductivity k* of the multi-layer structure inclusion region can be obtained by the following formula:

[0051]

[0052] According to the principle of neutral inclusions, by implementing the condition k* = k4, the thermal conductivity k3 of the medium of the cloaking layer Z3 in the present invention can be obtained:

[0053]

[0054] It can be seen from Equation (5) that the thermal conductivity k3 of the cloaking layer Z3 of the thermal cloaking in the present invention is less than the thermal conductivity k4 of the background medium, that is, k3 < k4. When the background medium is copper (thermal conductivity 400 W -1 m -1 K -1When using high thermal conductivity materials such as [material name], natural materials can be selected to meet the thermal conductivity requirements of the design layer. Furthermore, for a specific background medium with a thermal conductivity k4, this can be achieved by adjusting R. s By adjusting the value of R3 and the corresponding value of k3, more flexibility is provided in material selection, solving the problem of limitations on thermal conductivity material parameters in traditional design.

[0055] Verification experiment:

[0056] To ensure the accuracy of this invention, simulations were performed using the finite element simulation software COMSOL Multiphysics. Figure 5 and Figure 6 The simulation results are for a two-dimensional thermal cloak. Figure 5 and Figure 6 The background color gradually darkens from left to right. The lighter background on the left represents the high-temperature area, and the darker background on the right represents the low-temperature area. The color changes in the diagram represent different temperature distributions, and the white lines are isotherms. The isotherms on the outer region of the thermal cloak are straight lines, indicating that the temperature field has not been disturbed. The simulated dimensions of the thermal cloak are L = 0.12m, R1 = 0.01m, R2 = 0.012m, R... S =0.014m, R3=0.02m, the thermal conductivity of the target body can be set arbitrarily, the thermal conductivity parameter of the thermal insulation layer Z2 is k2=0, and the material of the thermoelectric layer Zs is metallic copper with a thermal conductivity k S =394W -1 m -1 K -1 The stealth layer Z3 is made of metallic aluminum, k3 = 237W. -1 m -1 K -1 The background medium is metallic copper, k4 = 394 W. -1 m -1 K -1 The material and geometric parameters are set according to equation (5), and the boundary conditions are set as follows: the left and right boundaries of the thermal stealth cloak are respectively a high-temperature heat source and a low-temperature cold source, and the upper and lower boundaries are insulated. In the horizontal direction, the target body Z1 is approximated as a circle, R1 is the radius of the target body, R2 is the outer diameter of the thermal insulation layer Z2, and R S R is the outer diameter of the thermoelectric layer Zs, and R3 is the outer diameter of the stealth layer Z3.

[0057] Figure 5In this invention, the temperature of the thermoelectric layer Zs is controlled according to equation (2). The isotherm of the background layer Z4 is not distorted, and the heat flow cannot enter the interior of the cloak, thus achieving the effect of thermal stealth. Specifically, according to the principle of neutral inclusion, when the thermal conductivity of the inclusion is the same as that of the background material, the inclusion does not affect the temperature field of the background material. That is, the design of this invention can eliminate the disturbance of the external temperature field by the thermal stealth cloak, and achieve the non-invasive effect of the thermal stealth cloak. The presence of the thermal insulation layer Z2 makes it difficult for the heat flow to enter the target body, thereby achieving thermal protection of the target body and thus achieving the thermal protection effect of the thermal stealth cloak.

[0058] In contrast. Figure 6 In the process, the temperature of the thermoelectric layer Zs is not controlled, heat flow invades the target body, and the external temperature field is disturbed, causing the isotherms of the background layer to be significantly distorted, thus failing to achieve thermal stealth effect.

[0059] While the invention has been described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the invention. Therefore, it should be understood that many modifications can be made to the exemplary embodiments, and other arrangements can be designed without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood that different dependent claims and features described herein can be combined in ways different from those described in the original claims. It is also understood that features described in conjunction with individual embodiments can be used in other described embodiments.

Claims

1. A design method for a thermally conductive cloak based on the principle of neutral inclusion, wherein the thermally conductive cloak comprises a thermally insulating layer Z2, a cloaking layer Z3, and a background layer Z4 distributed horizontally from the inside out; characterized in that, The thermal stealth cloak also includes a thermoelectric layer Zs, which is located between the thermal insulation layer Z2 and the stealth layer Z3. The thermal insulation layer Z2, the thermoelectric layer Zs, and the stealth layer Z3 are concentric, and the radial cross-sections of the thermoelectric layer Zs and the stealth layer Z3 are both annular. The radial cross-section of the thermal insulation layer Z2 is circular and is used to cover the target Z1. Temperature control is applied to the thermoelectric layer Zs to ensure that the equivalent thermal conductivity k* of the multilayer structure intergrowth region formed by the thermoelectric layer Zs and the stealth layer Z3 is k4, and this is combined with... The thermal conductivity of the stealth layer Z3 was obtained. Where k4 is the thermal conductivity of the background layer Z4, R s R3 is the outer diameter of the thermoelectric layer Zs, and R3 is the outer diameter of the stealth layer Z3. By adjusting R s By adjusting the values ​​of R3 and R3, the thermal conductivity k3 of the stealth layer Z3 can be adjusted, thus completing the design of a thermal stealth cloak with adjustable thermal conductivity.

2. The design method for a thermally adjustable thermal stealth cloak based on the principle of neutral inclusions according to claim 1, characterized in that, Temperature required for thermoelectric layer Zs Among them, T H and T L , respectively, are the boundary temperatures on the left and right sides of the background layer Z4, L is the length of the background layer Z4, and x0 is the abscissa of the center of the thermal insulation layer Z2 of the thermal cloak when a planar coordinate system is established with the lower left corner of the thermal cloak as the center.

3. The thermal conductivity adjustable thermal stealth cloak design method based on the neutral inclusion principle according to claim 1, characterized in that, The heat flow J within the thermoelectric layer Zs, and between the thermoelectric layer Zs and the stealth layer Z3, is described by Fourier's law of heat transfer, expressed as: J = -k s ▽T; Where, k s Let J be the thermal conductivity of the thermoelectric layer Zs, where J is a finite value, and ▽T be the temperature difference at the interface between the thermoelectric layer Zs and the stealth layer Z3, with ▽T approaching 0.

4. The design method for a thermally adjustable thermal stealth cloak based on the principle of neutral inclusions according to claim 1, characterized in that, The thermoelectric layer Zs is made of thermoelectric material.

5. The design method for a thermally adjustable thermal stealth cloak based on the principle of neutral inclusions according to claim 1, characterized in that, The thermoelectric layer Zs is used to connect to an external power source to achieve temperature control.

6. A computer-readable medium storing a computer program, characterized in that, When the computer program is executed, it implements the method as described in any one of claims 1 to 5.

7. An electronic device comprising a storage device, a processor, and a computer program stored in the storage device and executable on the processor, characterized in that, The processor executes the computer program to implement the method as described in any one of claims 1 to 5.

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