Method for regulating and controlling heat convection in porous medium through pressure intensity and achieving function switching effect

Abstract

The invention discloses a method for regulating and controlling heat convection in a porous medium through pressure intensity and achieving a function switching effect. According to the method, a control equation based on the Darcy law only needs to regulate the pressure intensity, so that the spatial distribution of the anisotropic permeability of the porous medium functional layer is regulated, the thermal field and the flow field can be controlled at the same time, and the functions of invisibility, aggregation and the like in the heat and mass transportation process are achieved. Meanwhile, a liquid gating technology is combined, and the porous medium metamaterial model with the adjustable stealth-aggregation function is provided. According to the method, different functions can be presented under different pressure differences, heat and mass transfer in the porous medium is adjusted and controlled through pressure, the function switching effect is achieved, and the method has potential application in the fields of medical treatment, chemical engineering, energy conversion and the like.

Description

Technical Field

[0001] The present invention relates to the field of metamaterial technology, and in particular to a method for controlling heat convection in a porous medium by pressure and achieving a function switching effect. Background Art

[0002] Heat and mass transport in porous media is a fundamental phenomenon ubiquitous in nature and in human life. Its transport laws span multiple disciplines, including physics, fluid dynamics, and heat transfer. In recent years, metamaterial design approaches such as transformation optics have penetrated the field of thermal convection, particularly heat and mass transfer in porous media, and have achieved remarkable theoretical success. A key factor is that the classic Darcy law describing heat and mass transfer in porous media remains invariant under arbitrary spatial coordinate transformations. Therefore, based on transformation theory and leveraging natural materials to design and construct complex porous systems with specialized structures and arrangements, novel transport properties not possessed by natural porous materials can be achieved. However, practical applications of these technologies are rarely reported. This is primarily because transformation-theory-based control methods require simultaneous spatial transformations of parameters such as thermal conductivity and permeability, making precise modulation of multiple parameters difficult within the confined space of porous media. Therefore, there is an urgent need to develop design methods that can simultaneously modulate multiple physical fields, including heat and fluid, using only a small number of parameters, or even a single parameter.

[0003] In response to the above-mentioned problem of multi-field control of porous medium metamaterials, existing solutions are limited to multifunctional control of a single physical field. That is, only for the thermal field or flow field, simplified structural parameters are designed to meet the single field function. However, there is still a lack of effective solutions for the simultaneous control of the thermal field and flow field. Most actual application processes are at room temperature or in places where the temperature is not too high, so the heat-flow coupling problem can be simplified to an isothermal flow problem. Under isothermal flow conditions, the Darcy equation that controls heat and mass transport in porous media can mathematically realize the unidirectional coupling of the thermal field and the flow field. In this way, the flow field and the thermal field can be controlled simultaneously by controlling the flow field and indirectly affecting the thermal field. Summary of the Invention

[0004] In order to solve the defects and shortcomings of the above-mentioned prior art, the present invention provides a method for controlling thermal convection in porous media by pressure and achieving functional switching effects; this method uses a single control of the pressure magnitude of the corresponding functional device structural area under the physical fields of mass transfer and heat and mass transfer, respectively, to achieve two different morphological functions of the thermal functional device.

[0005] The present invention provides a method for controlling thermal convection in a porous medium by pressure and achieving a functional switching effect. Based on the transformation equation of Darcy's law, the pressure in the structural area of a thermal functional device is regulated to modulate the spatial distribution of the anisotropic permeability of the porous medium to achieve precise control of convective transport, thereby indirectly controlling the field distribution of convective heat transfer, achieving simultaneous control of fluid flow and heat transfer, and functional switching of the thermal functional device as an invisible cloak-concentrator under thermal and flow fields.

[0006] In the present invention, the background area of the thermal functional device is a square, two concentric circles are set in the middle of the area, the area surrounded by the small circles is the central area, and the annular area surrounded by the concentric circles is the functional area. The entire device is paved with a porous medium fluid material structure.

[0007] In the present invention, the fluid in the flow field is selected from any one of polydimethylsiloxane, water, polyethylene glycol aqueous solution or polyurethane prepolymer.

[0008] In this invention, drawing on liquid gating technology and utilizing the phase transition theory of shape transformation parameters, the transformation radius corresponds to two different spatial transformation values under different pressure differences, thereby affecting the value distribution of effective permeability under different pressure differences, realizing the switchable invisibility cloak-concentrator function controlled by pressure; the details are as follows:

[0009] Based on the coordinate transformation principle, in the polar coordinate system, let the original coordinates be (r, θ) and the transformed coordinates be (r', θ'), satisfying:

[0010]

[0011] Where: R1 is the radius within the functional area, R2 is the radius outside the functional area; R * (p) is the shape transformation parameter, also called transformation radius; shape transformation parameter R * (p) is determined by the switching devices with different functions. To achieve function switching, there are the following transformation forms:

[0012]

[0013] Where R3 is the radius between the inner radius R1 and the outer radius R2 of the functional area, d is the sensitivity coefficient for adjusting the relationship between pressure difference and permeability, Δp is the pressure difference, p c To achieve the critical pressure difference value of function switching;

[0014] Furthermore, in polar coordinates, the radial permeability s of the functional area of the dual-function device is r (p) and tangential permeability s θ (p) are as follows:

[0015]

[0016] Where: s0 is the permeability of the background material; shape transformation parameter R * (p) corresponds to different values under different pressure differences, which in turn affects the distribution of effective permeability under different pressure differences. When the pressure difference Δp is small, R * (p) approaches R3, at which point the thermal function device is a concentrator; when the pressure difference Δp increases, R * (p) approaches 0, at which point the thermal functional device acts as an invisible cloak.

[0017] In the present invention, based on the form invariance of the Darcy flow equation under coordinate transformation, the tensor form of the permeability s in the Cartesian coordinate system is as follows:

[0018]

[0019] Where J is the Jacobian matrix, det J is the matrix determinant, J T is the transpose of the Jacobian matrix J;

[0020] Combining Equation (7) with Equation (2) to solve the spatial distribution of permeability in the form of anisotropic tensor, the device state under different functions is analyzed, and the spatial distribution of effective permeability of porous media is modulated.

[0021] In the present invention, the heat source and the cold source are respectively located on both sides of the thermal functional device structural area to form a flow area; the high pressure and low pressure of the thermal functional device are respectively set to 1000Pa and 0Pa; the high temperature and low temperature are respectively set to 343K and 283K.

[0022] Compared with the prior art, the beneficial effects of the present invention are: the present invention uses liquid gating technology to provide a porous medium metamaterial model with adjustable stealth-aggregation function; the present invention uses finite element software for verification, and the structural geometry sets the size of the background material area to be a square, and sets concentric circles in the middle of the area, the small circle is the central area, and the annular area outside the small circle is the functional area. The thermal functional material device structure of the present invention is laid out as a fluid material structure, and the high and low pressures are set to 1000Pa and 0Pa respectively; the high and low temperatures are set to 343K and 283K respectively. Under the high and low pressure design conditions of the present invention, the spatial distribution of the effective permeability of the porous medium is modulated to verify the effect of the single parameter pressure on the mass transfer physical field. Under the high and low temperature design conditions of the present invention, the spatial distribution of the effective permeability of the porous medium is modulated to verify the effect of the single parameter pressure on the heat and mass transfer physical field; the results show that

[0023] (1) The present invention achieves the effect of controlling the thermal field and flow field simultaneously with a single parameter.

[0024] (2) The present invention implements liquid gating technology to achieve a functional switching effect.

[0025] (3) The present invention can simultaneously demonstrate different functional effects on the same thermal functional device in the thermal field and the flow field, saving materials while reducing the difficulty of experimental preparation.

[0026] (4) The present invention can be fully realized in steady state, and can also be extended to transient state and other physical fields to realize the same function. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 On the left is a structural diagram of the method of the present invention, including an inner and outer circle structure, the circular area is the functional area, and the background area and the central area are background materials with unchanged parameters; the upper right diagram is a conceptual schematic diagram using polydimethylsiloxane as the fluid, and the lower right diagram indicates that it can be integrated inside the chip to realize the application and achieve liquid cooling of the chip.

[0028] Figure 2 This is a function switching effect diagram, including theoretical basis explanation. By theoretical transformation, the permeability tensor size of the functional area is changed to achieve the invisibility cloak / aggregator effect, and a set of deformation parameters R is given. * (p) enables it to achieve the effect of function switching.

[0029] Figure 3 The three-dimensional data graphs show the radial permeability, tangential permeability, and permeability of the functional area compared with the background material. The three 3D data graphs show the permeability comparisons of the thermal functional device in the clustered state, critical state, and stealth state, respectively.

[0030] Figure 4 (a)-(c) are the simulation results of the pressure field distribution inside the material, which are the simulated functions of the metamaterial when the background material inlet pressure is 100Pa, 500Pa, and 1000Pa, simulating the effect of switching from aggregation to stealth, and the white lines are isobars; at the same time, the velocity field generated by the fluid flow under the corresponding inlet pressure, the black arrow indicates the velocity direction, and also simulates the effect of switching from aggregation to stealth; (d)-(f) are the simulation results of the pressure field distribution of the reference model, which are illustrations of the reference model under the corresponding inlet pressure (that is, the functional area-related design is not considered and is consistent with the background area), the white lines are isobars, and the black arrows are the velocity direction.

[0031] Figure 5This figure compares the average flow velocity in the center region of the simulated material and the reference model as a function of inlet pressure. The vertical axis represents the average velocity in the center region. Analysis shows that under steady-state conditions, the flow velocity in the center region of the reference model is positively correlated with the inlet pressure. However, after setting the functional area parameters, as the inlet pressure increases, the flow velocity in the center region first increases rapidly (achieving a gathering effect), then rapidly decreases to near zero near the critical value of 500 Pa, indicating that the flow velocity in the center region is zero at this time (achieving a stealth effect). The simulation effect diagram in the figure shows the velocity field direction when the inlet pressure is 500 Pa, and the black arrow indicates the flow velocity direction.

[0032] Figure 6 This figure compares the average pressure of the simulated material and the reference model as a function of inlet pressure. The vertical axis represents the range of average pressures. We can see that as the inlet pressure increases, the ratio of the average pressures increases. That is, at the same inlet pressure, the average pressure of the simulated material is greater than that of the reference model. This is due to the metamaterial's ability to aggregate as the inlet pressure increases. However, near the critical value of 500 Pa, the aggregation effect disappears, and the metamaterial gradually becomes invisible.

[0033] Figure 7 (a)-(c) are the simulation results of the total heat flux distribution diagram of the simulated material. As we know, the direction of the total heat flux is dominated by the convection process at high Peclet numbers, so the direction of the total heat flux gradually shows the direction of convection heat flux, that is, the total heat flux realizes the functional switching from aggregation to stealth, achieving the effect of functional switching; (d)-(f) are the simulation results of the total heat flux distribution of the reference model, which are compared with the simulated material.

[0034] Figure 8 This figure compares the total heat flux in the center of the simulated material and the reference model as a function of inlet pressure. The total heat flux in the reference model's center increases with increasing inlet pressure, while the total heat flux in the simulated material's center initially increases (achieving the focusing function), then rapidly decreases near 500 Pa, and then slowly decreases to near zero (achieving the stealth function), achieving the switch from focusing to stealth.

[0035] Figure 9 The figure below compares the average velocity in the center of the simulated material and the reference model. The average velocity in the center of the reference model increases with increasing inlet pressure. Similarly, after setting the functional area parameters, the velocity in the center increases with increasing inlet pressure (achieving a focusing effect), then decreases to near zero after reaching a critical value of 500 Pa, indicating that the velocity in the center is zero (achieving a stealth effect). The line graph above the figure compares the average velocity under the same parameter settings for pure convection. It can be seen that the introduction of conduction at high Peclet numbers has no effect on the study, indicating that the thermal field does not affect the flow field distribution under isothermal flow conditions.

[0036] Figure 10 The figure below shows the relationship between the reference factor γ and the increase in inlet pressure. As the inlet pressure increases, the value of γ first increases and then decreases; that is, when γ is large, the thermal metastructure material exhibits an aggregated state, and when γ decreases to a critical value, the thermal metastructure material exhibits a stealth state.

[0037] Figure 11 A comparison of the total change in the central area of the simulated material and the reference model as a function of inlet pressure is shown. The heat fluxes of conduction and heat transfer are shown for the reference and virtual models, respectively, for pairwise comparison. DETAILED DESCRIPTION

[0038] The present invention will be described clearly and completely below with reference to the accompanying drawings and embodiments.

[0039] This invention utilizes the coordinate transformation theory of transformation thermodynamics to design the Jacobian matrix transformation of the permeability tensor of the functional area, while also providing a set of shape transformation parameters to achieve the switching function of the thermal functional device from a concentrator to an invisible cloak. The main scientific principles of this method are detailed below:

[0040] 1. Transformation Theory

[0041] Transformation optics theory points out that through coordinate transformation, the physical field can be mapped from one space to another space, and a mapping relationship between the two spaces can be established. Here, the design method we provide will be used for the mathematical transformation of functional areas. In order to study the form invariance of the governing equations for heat and mass transport in porous media under coordinate transformation, the present invention uses Darcy's law equation to replace the more general Navier-Stokes equation. Darcy's law mainly describes the law of fluid seepage in the gaps of porous media. Under steady-state conditions, the general form of Darcy's law is as follows:

[0042]

[0043] Where p is pressure, μ is dynamic viscosity, s is permeability, and v is the flow rate of the fluid. From formula (1), we can know that when the flow rate is small and the dynamic viscosity is constant, the pressure gradient and permeability are linearly related, that is, theoretically, by changing the pressure gradient To change the corresponding parameters of permeability.

[0044] Similar to the transformation of the general diffusion equation, based on the form invariance of the Darcy flow equation under coordinate transformation, we can obtain the tensor form of the permeability s in the Cartesian coordinate system as follows:

[0045]

[0046] Where s' is the permeability in tensor form, J is the Jacobian matrix, det J is the matrix determinant, and J T is the transpose of the Jacobian matrix J. The present invention designs thermal superstructure materials with different functions by designing permeabilities s' in different tensor forms.

[0047] From formula (1), we can know that the present invention changes the corresponding parameters of permeability by changing the pressure gradient. Therefore, we control the pressure gradient By changing the permeability s' in the tensor form, we can finally design thermal metamaterials with different functions.

[0048] 2. Function switch

[0049] Next, the present invention draws on the liquid gating technology to propose a shape transformation parameter R * (p) phase transition theory.

[0050] Previously, based on the principle of coordinate transformation, we know that in the polar coordinate system, for the case of an invisibility cloak, the relationship between the original coordinates (r, θ) and the transformed coordinates (r', θ') is as follows:

[0051]

[0052] The transformation formula of the aggregator in the polar coordinate system is as follows:

[0053]

[0054] Where r' is the parameter after polar coordinate transformation, r is before transformation, θ' is after transformation, and θ is before transformation. R2 is the radius of the outer circle of the geometric structure, R1 is the radius of the inner circle, and R3 is the transition radius between the outer circle and the inner circle.

[0055] From formula (4), we can see that when R3 is 0, formula (4) is the same as formula (3), and the aggregation becomes invisible. Inspired by this, the present invention proposes a shape transformation parameter R * (p) is used to replace R3 in formula (4), so that the transformation radius corresponds to two different values under different pressure differences, which in turn affects the value distribution of the permeability s' in tensor form under different pressure differences, thereby obtaining a pressure-controlled switchable invisibility cloak-concentrator functional device, namely:

[0056]

[0057] For the shape transformation parameter R * (p) is determined by the switching devices with different functions. To achieve function switching, there are the following transformation forms:

[0058]

[0059] Where R3 is the radius between R1 and R2, d is the sensitivity coefficient that adjusts the relationship between pressure difference and permeability, and Δp is the pressure difference, p c The critical pressure difference value for achieving function switching.

[0060] In the present invention, the pressure gradient is the pressure difference per unit distance Δp.

[0061] In polar coordinates, the radial permeability and tangential permeability of the functional area of the dual-function device can be expressed as:

[0062]

[0063] where s r (p) and s θ (p) are the radial permeability and tangential permeability, s0 is the background material permeability, and r' is the coordinate transformation relationship, i.e., Equation (5). Combining Equation (7) with Equation (2) can solve the permeability spatial distribution in the form of anisotropic tensors, and then analyze the device status under different functions.

[0064] For formula (7), when the pressure difference is small, R * (p) approaches R3, at which point the thermal function device is a concentrator; when the pressure difference increases, R * (p) approaches 0, and the thermal function device is an invisible cloak. Therefore, as the pressure difference gradually increases, R * (p) As R3 gradually approaches 0, the thermal function device switches from a concentrator to an invisible cloak.

[0065] 3. Heat convection transport

[0066] Combining the above two points, in order to achieve the corresponding functions, the present invention uses porous media heat transfer to allow conduction and convection to share the same space. When considering steady-state heat transport in the metamaterial, the total heat flow is controlled by the conservation equation, which is as follows:

[0067]

[0068] Among them, J 传导 is the conductive heat flow based on Fourier's law, J 对流 is the convective heat flux based on Darcy's law. When the convection reaches local stability, the above equation holds.

[0069] In order to further analyze the effect of function switching under the corresponding pressure difference control, this paper introduces a new variable γ as a reference factor, which is as follows:

[0070]

[0071] Among them J1hot The total heat flow in the center area of the functional device simulation material, J 2hot is the total heat flow in the central area of the reference model. Both are numerically calculated data results under the same inlet pressure conditions.

[0072] In summary, the theoretical approach described above is scientifically feasible. We further extended it to finite element simulations to verify its feasibility. We then applied it to flow and thermal fields, analyzing the resulting rainbow plots. We then compared the calculated pressure, velocity, and thermal flow fields with those from a reference model to validate the feasibility of the invention. By deducing and verifying the formula, we ultimately determined the functional switching effect of the thermally functional device.

[0073] The present invention uses COMSOL Multiphysics finite element simulation to design a model of thermal superstructure materials. Figure 1 As shown, first, for simple fluid mass transfer, the Darcy law module under porous media is used to design it: the background plate size is 8×8mm 2 The center circle radius is 1 mm, the outer circle radius is 2 mm, and the background area and the center area are set to the same permeability of 1.0×10 -12 m 2 , the permeability of the functional area material is set as anisotropic tensor form. At the left boundary of the material, the inlet pressure is set to P1, and the outlet pressure at the right boundary is set to P2 = 0Pa. The critical value of the pressure difference P c =500Pa.

[0074] Then the present invention combines the coordinate transformation theory model to set the function switching method. Figure 2 The following is a diagram showing the effect of function switching, including theoretical explanations. By theoretically transforming the permeability tensor of the functional area to achieve the invisibility cloak / aggregator effect, a set of deformation parameters R is given. * (p) enables it to achieve the effect of function switching. Figure 3 The three-dimensional data graphs show the radial permeability, tangential permeability, and permeability of the functional area compared with the background material. The three 3D data graphs show the permeability comparisons of the thermal functional device in the clustered state, critical state, and stealth state, respectively.

[0075] Then use parametric sweep to calculate all integer values of the material inlet pressure P1 from 0Pa to 1000Pa, such as Figure 4 As shown. Without affecting the background material, the simulation results show that when P1 < 500Pa, the metamaterial function is in the aggregation state; when P1 > 500Pa, the metamaterial function is in the stealth state. Figure 5-Figure 6As shown in the figure, in order to further analyze the functional characteristics of the metamaterial, we draw a comparison chart of the speed of the simulated material and the speed of the reference model; we also analyze the difference in the average pressure in the central area between the simulated material and the reference model.

[0076] Considering the coupled simulation of conduction and convection, the present invention uses the porous media heat transfer module for design: the background area and the central area are set to have the same permeability of 1.0×10 -12 m 2 The permeability of the functional area material is in the form of an anisotropic tensor. The inlet pressure P1 and high temperature T1 are applied to the left side of the material, and the outlet pressure P2 and low temperature T2 are applied to the right side, where T1 = 343K, T2 = 283K, and P2 = 0Pa.

[0077] same Figure 4 Similarly, parametric sweep is used to calculate all integer values of the inlet pressure P1 from 0Pa to 1000Pa. The results are as follows Figure 7 It was found that when the inlet pressure P1 < 500Pa, the metamaterial function was in an aggregation state without affecting the background material; when P1 > 500Pa, the metamaterial function was in a stealth state, that is, the function switching from aggregation to stealth was achieved. Figures 8-11 As shown, in order to explore the validity of the simulation results and the influence of heat transfer and conduction on heat flow, we analyzed and drew a comparison diagram of the total heat flow in the central area of the simulated material and the reference model, a comparison diagram of the average velocity, a diagram of the change relationship between the reference factor and the increase of the inlet pressure, and a comparison diagram of the total change with the inlet pressure, respectively verifying the feasibility and generalizability of the present invention from different angles.

[0078] Based on the principle of transformation optics, the present invention proposes a method for controlling heat convection in porous media by pressure and achieving a functional switching effect, thereby realizing the simultaneous control of the thermal field and flow field in porous media. Under high Peclet numbers, the transformation equation based on Darcy's law achieves precise control of convective transport through permeability modulation, thereby indirectly controlling the field distribution of convective heat transfer and realizing the simultaneous control of fluid flow and heat transfer. On this basis, drawing on the liquid gating technology, a shape transformation parameter R is proposed. * (p) phase transition theory, so that the transformation radius R * (p) Two different spatial transformations correspond to different pressure differences, thereby affecting the distribution of effective permeability values under different pressure differences, realizing a switchable invisibility cloak-concentrator function under dual pressure-controlled fields. Finite element simulations were then used to verify the feasibility of the design method. This invention can greatly simplify the preparation of porous medium metamaterials. The Darcy thermal convection considered in this invention is a simple unidirectionally coupled multi-physics process, making it naturally applicable to other unidirectionally coupled thermal convection processes. It has similar regulatory effects on other thermal convection models, such as creeping flow between two flat plates.

Claims

1. A method for controlling heat convection in a porous medium by pressure and achieving a functional switching effect, characterized in that: The transformation equation based on Darcy's law achieves precise control of convective transport by regulating the pressure in the structural area of the thermal functional device to modulate the spatial distribution of the anisotropic permeability of the porous medium, thereby indirectly regulating the field distribution of convective heat transfer, realizing simultaneous control of fluid flow and heat transfer, and switching the function of the thermal functional device as a cloak-concentrator under thermal and flow fields.

2. The method according to claim 1, characterized in that The background area of the thermal functional device is a square, with two concentric circles set in the middle of the area. The area surrounded by the small circles is the central area, and the circular area surrounded by the concentric circles is the functional area. The entire device is paved with a porous medium fluid material structure.

3. The method according to claim 2, characterized in that The fluid in the applicable flow field is selected from any one of polydimethylsiloxane, water, polyethylene glycol aqueous solution or polyurethane prepolymer.

4. The method according to claim 2, characterized in that Drawing on liquid gating technology and utilizing the phase transition theory of shape transformation parameters, the transformation radius corresponds to two different spatial transformation values under different pressure differences, thereby affecting the distribution of effective permeability values under different pressure differences, realizing a pressure-controlled switchable invisibility cloak-concentrator function; the details are as follows: Based on the coordinate transformation principle, in the polar coordinate system, let the original coordinates be (r, θ) and the transformed coordinates be (r', θ'), satisfying: Where: R1 is the radius within the functional area, R2 is the radius outside the functional area; R * (p) is the shape transformation parameter, also called transformation radius; shape transformation parameter R * (p) is determined by the switching devices with different functions. To achieve function switching, there are the following transformation forms: Where R3 is the radius between the inner radius R1 and the outer radius R2 of the functional area, d is the sensitivity coefficient for adjusting the relationship between pressure difference and permeability, Δp is the pressure difference, p c To achieve the critical pressure difference value of function switching; Furthermore, in polar coordinates, the radial permeability s of the functional area of the dual-function device is r (p) and tangential permeability s θ (p) are as follows: Where: s0 is the permeability of the background material; shape transformation parameter R * (p) corresponds to different values under different pressure differences, which in turn affects the distribution of effective permeability under different pressure differences. When the pressure difference Δp is small, R * (p) approaches R3, at which point the thermal function device is a concentrator; when the pressure difference Δp increases, R * (p) approaches 0, at which point the thermal functional device acts as an invisible cloak.

5. The method according to claim 4, characterized in that: Based on the form invariance of the Darcy flow equation under coordinate transformation, the tensor form of the permeability s in the Cartesian coordinate system is as follows: Where J is the Jacobian matrix, det J is the matrix determinant, J T is the transpose of the Jacobian matrix J; Combining Equation (7) with Equation (2) to solve the spatial distribution of permeability in the form of anisotropic tensor, the device state under different functions is analyzed, and the spatial distribution of effective permeability of porous media is modulated.

6. The method according to claim 1, characterized in that The heat source and cold source are located on both sides of the thermal functional device structure area to form a flow area; the high pressure and low pressure of the thermal functional device are set to 1000Pa and 0Pa respectively; the high temperature and low temperature are set to 343K and 283K respectively.

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