A high-multiplying thermoelectric conversion device and a design method

Abstract

This invention relates to the field of thermal protection structures for low Earth orbit (LEO) vehicles, specifically to a high-density thermoelectric conversion device and its design method. The high-density thermoelectric conversion device includes: a high-density thermal layer disposed on the inner side of the vehicle surface; a heat exchanger surrounding the inner side of the high-density thermal layer; and a thermoelectric converter disposed between the high-density thermal layer and the heat exchanger. The heat-absorbing end of the thermoelectric converter is connected to the high-density thermal layer, and the heat-releasing end of the thermoelectric converter is connected to the wall of the heat exchanger. Embodiments of this invention, by setting a high-density thermal layer and a heat exchanger on the surface of the vehicle, create a large temperature difference between the heat-absorbing and heat-releasing ends of the thermoelectric converter on the vehicle surface. This reduces the surface temperature of the vehicle and provides power to the vehicle, thereby solving the thermal protection and power supply problems of LEO vehicles.

Description

Technical Field

[0001] This invention relates to the field of thermal protection structures for low-orbit vehicles, specifically to a high-concentration thermoelectric conversion device and its design method. Background Technology

[0002] Low Earth orbit (LEO) vehicles have a wide range of applications in remote sensing communication, environmental monitoring, resource management, disaster response, and scientific research. They are considered a new solution for future space missions. LEO vehicles have many advantages, such as high signal-to-noise ratio of instruments, high accuracy of space mapping, low launch cost, low risk of on-orbit collision, and simple system structure. They have attracted widespread attention from researchers and commercial space companies and have become one of the research hotspots.

[0003] However, due to the special space environment of low Earth orbit (orbital altitude 100km - 180km), low Earth orbit satellites face many technical challenges, including overcoming the significant aerodynamic heating caused by hypersonic flight in a thin atmosphere, mainly including convective heat, chemical heat and radiative heat. When the spacecraft is at an orbital altitude of 110km, the heat flux value of the frontal windward area is as high as 21kW / m2. Therefore, thermal protection technology is one of the technical problems that low Earth orbit spacecraft urgently need to solve.

[0004] In addition, power supply is also a major problem for low-Earth orbit spacecraft. Due to the low orbit, the amount of solar radiation is not stable, and traditional photovoltaic power generation is difficult to meet the overall power demand of the spacecraft. Summary of the Invention

[0005] The purpose of this invention is to provide a high-concentration thermoelectric conversion device and design method to solve the thermal protection and power supply problems of low-orbit spacecraft.

[0006] To solve the above-mentioned technical problems, the present invention specifically provides the following technical solution:

[0007] A high-concentration thermoelectric conversion device includes: a high-concentration layer disposed on the inner side of the surface of an aircraft, a heat exchanger surrounding the inner side of the high-concentration layer, and a thermoelectric converter disposed between the high-concentration layer and the heat exchanger, wherein the heat-absorbing end of the thermoelectric converter is connected to the high-concentration layer, and the heat-releasing end of the thermoelectric converter is connected to the wall of the heat exchanger.

[0008] Furthermore, the high-density thermal layer is shaped like a frustum or a multi-faceted frustum, with its lower surface contacting the surface of the aircraft and its upper surface contacting the heat-absorbing end of the thermoelectric converter.

[0009] Furthermore, the high-density heat-concentrating layer is shaped like a frustum, with a cross-section that is a square with continuously varying side lengths.

[0010] Furthermore, the heat exchanger includes a heat-conducting layer and a substrate layer. The heat-conducting layer is directly attached to the heat-dissipating end of the thermoelectric converter, and the substrate layer is attached to the side of the heat-conducting layer away from the thermoelectric converter. A heat exchange chamber is formed inside the heat-conducting layer, and a cooling medium inlet and a cooling medium outlet are provided on both sides of the heat-conducting layer, which penetrate the heat-conducting layer and connect to the heat exchange chamber.

[0011] Furthermore, the heat exchange chamber includes several heat exchange channels with a square cross-section. The side length and spacing of each heat exchange channel are equal, and the two ends of each heat exchange channel are respectively connected to the cooling medium inlet and the cooling medium outlet.

[0012] Furthermore, the thickness δ1 of the high-density heat-concentrating layer is 2-7 mm, the thickness δ2 of the thermoelectric converter is 8-13 mm, the thickness δ3 of the thermally conductive layer is 2-5 mm, the thickness δ4 of the substrate layer is 5-15 mm, the cross-sectional dimension d of the heat exchange channel is 2-5 mm, the number of heat exchange channels n is 5, the side length D of the heat-absorbing end of the thermoelectric converter is 20-40 mm, the ratio of the side length L of the substrate layer to the side length D of the heat-absorbing end of the thermoelectric converter is 5:4 to 4:3, the side length M of the bottom of the high-density heat-concentrating layer is 90-134 mm, and the heat concentration ratio P of the high-density heat-concentrating layer is 9:1 to 16.75:1.

[0013] Furthermore, the material of the heat-conducting layer is a copper alloy, the material of the substrate layer is stainless steel, and the material of the thermoelectric converter is a semi-Hersler alloy.

[0014] Furthermore, both the cooling medium inlet and the cooling medium outlet are equipped with flow meters, flow controllers, and temperature sensors, and both the heat absorption end and the heat release end of the thermoelectric converter are equipped with temperature sensors.

[0015] A design method for a high-concentration thermoelectric conversion device, the design method comprising the following steps:

[0016] Step 1: Determine the total heat flux on the outer surface of the low Earth orbit spacecraft;

[0017] Step 2: Determine the heat concentration ratio P of the high-density heat-concentrating layer, the cross-sectional dimension d of the heat exchange channel, the number n of the heat exchange channels, the reference temperature of the cooling medium, and the heat transfer coefficient.

[0018] Step 3: Determine the thickness δ1 of the high-density heat-concentrating layer, the thickness δ2 of the thermoelectric converter, the thickness δ3 of the thermally conductive layer, the thickness δ4 of the substrate layer, and the ratio D / L of the side length of the heat-absorbing end of the thermoelectric converter to the side length of the substrate layer through experimental experience and theoretical calculations.

[0019] Step 4: Solve the thermoelectric-cooling integrated coupled equations based on thermoelectric theory and thermal resistance analysis;

[0020] Step 5: Obtain the temperature of the heat-absorbing end of the thermoelectric converter, and determine whether the temperature of the heat-absorbing end of the thermoelectric converter is less than the maximum withstand temperature of its own material. If yes, proceed to step 6; otherwise, proceed to step 2.

[0021] Step 6: Obtain the energy conversion efficiency and output power per unit area of ​​the thermoelectric converter, and determine whether the energy conversion efficiency is greater than the predetermined requirement. If yes, proceed to step 7; otherwise, proceed to step 3.

[0022] Step 7: Determine the parameters of the high-concentration thermoelectric conversion device.

[0023] A high-polymerization thermoelectric conversion device, comprising, in sequence: a high-polymerization layer, a thermoelectric converter, a heat-conducting layer, and a substrate layer; wherein, the bottom wall of the high-polymerization layer serves as the surface of an aircraft, the heat-conducting layer is directly attached to the heat-dissipating end of the thermoelectric converter, the substrate layer is attached to the side of the heat-conducting layer away from the thermoelectric converter, a heat exchange chamber is formed inside the heat-conducting layer, and a cooling medium inlet and a cooling medium outlet are provided on both sides of the heat-conducting layer, penetrating the heat-conducting layer and connecting to the heat exchange chamber.

[0024] Compared with the prior art, this application has the following advantages:

[0025] This invention provides a high-concentration thermoelectric conversion device and its design method. By setting a high-concentration layer and a heat exchanger on the surface of the aircraft, a large temperature difference is generated between the heat absorption end and the heat release end of the thermoelectric converter on the surface of the aircraft. On the one hand, it can reduce the surface temperature of the aircraft, and on the other hand, it can provide power to the aircraft, thereby solving the thermal protection and power supply problems of low-orbit aircraft. Attached Figure Description

[0026] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0027] Figure 1 This is a perspective view of the high-concentration thermoelectric conversion model according to an embodiment of the present invention;

[0028] Figure 2 This is a perspective view of the high-concentration thermoelectric conversion model according to an embodiment of the present invention;

[0029] Figure 3 This is a cross-sectional view from one perspective of the high-concentration thermoelectric conversion model of an embodiment of the present invention;

[0030] Figure 4 A cross-sectional view from another perspective of the high-concentration thermoelectric conversion model of this invention.

[0031] Figure 5 This is a flowchart illustrating the design method of a high-concentration thermoelectric conversion device according to an embodiment of the present invention;

[0032] Figure 6 A graph showing the relationship between the orbital altitude of an aircraft and the heat flux value of the frontal windward region;

[0033] Figure 7 This is a graph showing the relationship between the heat-concentrating ratio of the high-heat-concentrating layer and the temperature of the heat-absorbing end of the thermoelectric converter in an embodiment of the present invention.

[0034] Figure 8 This is a graph showing the relationship between the heat-concentrating ratio of the high-heat-concentrating layer and the temperature of the heat-dissipating end of the thermoelectric converter in an embodiment of the present invention.

[0035] Figure 9 This is a graph showing the relationship between the heat-concentrating ratio of the high-heat-concentrating layer and the energy conversion efficiency of the thermoelectric converter in an embodiment of the present invention.

[0036] Figure 10 This is a graph showing the relationship between the heat concentration ratio of the high-heat-concentrating layer and the output power per unit area of ​​the thermoelectric converter in an embodiment of the present invention.

[0037] Figure 11 This is a diagram illustrating the cooling effect of the thermoelectric converter on the aircraft wall according to an embodiment of the present invention.

[0038] The labels in the diagram represent the following:

[0039] 1-High-concentration heat-concentrating layer; 2-Thermoelectric converter; 3-Heat-conducting layer; 4-Heat exchange channel; 5-Substrate layer. Detailed Implementation

[0040] 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.

[0041] Thermoelectric conversion is a promising technology for thermal protection systems in low Earth orbit (LEO) vehicles. On one hand, it converts heat energy into electrical energy to power the vehicle itself and onboard instruments, reducing the need for battery capacity and high-strength photovoltaic panels, and improving the flight payload ratio.

[0042] On the other hand, thermoelectric conversion technology can absorb heat from the surface of low-Earth orbit vehicles through a high-concentration heat design, thereby achieving thermal protection for the vehicle. Combining thermoelectric conversion technology with active cooling not only meets the thermal protection requirements of low-Earth orbit vehicles but also turns waste into treasure, thus improving the energy utilization efficiency of the vehicle.

[0043] Based on the above concept, a high-concentration thermoelectric conversion device is provided below, including: a high-concentration layer 1 disposed on the inner side of the surface of an aircraft, a heat exchanger surrounding the inner side of the high-concentration layer 1, and a thermoelectric converter 2 disposed between the high-concentration layer 1 and the heat exchanger. The heat-absorbing end of the thermoelectric converter 2 is connected to the wall of the high-concentration layer 1, and the heat-releasing end of the thermoelectric converter 2 is connected to the wall of the heat exchanger.

[0044] That is, the internal structure of the aircraft, from the outside to the inside, consists of the aircraft surface, the high-density thermal layer 1, the thermoelectric converter 2, and the heat exchanger. The aircraft heats the high-density thermal layer 1 through aerodynamic heating generated by its own hypersonic flight in the thin atmosphere. The high-density thermal layer 1 concentrates the heat at the heat-absorbing end of the thermoelectric converter 2. The heat exchanger generates a low temperature on its own wall surface through the flow of the cooling working fluid inside, thus creating a large temperature difference between the heat-absorbing end and the heat-releasing end of the thermoelectric converter 2. The thermoelectric converter 2 absorbs heat from the high-density thermal layer 1, releases heat to the heat exchanger, and converts part of the heat into electrical work, thereby achieving the purpose of integrated cooling and power generation.

[0045] The thermoelectric converter 2 is made of semi-Hersler alloy.

[0046] The high-concentration heat layer 1 amplifies the limited heat flow by a factor of ten or more when it reaches the hot end of the thermoelectric converter 2 by shrinking its cross section, so as to meet the energy conversion efficiency and output power requirements of the thermoelectric converter 2. The heat flow amplification factor is the heat concentration ratio.

[0047] To achieve this goal, the shape of the high-density thermal layer 1 can be selected from a frustum or a pyramidal shape. The bottom of the high-density thermal layer 1 contacts the surface of the aircraft, and the top of the high-density thermal layer 1 contacts the heat-absorbing end of the thermoelectric converter 2.

[0048] In this embodiment, the high-heat-concentrating layer 1 is made of a material with high heat resistance and high thermal conductivity, such as silicon carbide (SiC) composite material, aluminum nitride (AlN) material, aluminum-based composite material (Al-SiC), etc.

[0049] The high-density heat-concentrating layer 1 is shaped like a square platform, with a cross-section that is a square with continuously varying side lengths.

[0050] The heat exchanger is used to cool the heat-dissipating end of the thermoelectric converter 2, ensuring that the temperature of the heat-absorbing end of the thermoelectric converter 2 with high heat flux is within the maximum tolerance temperature of the thermoelectric material, thereby increasing the temperature difference between the heat-absorbing end and the heat-dissipating end of the thermoelectric converter 2, thereby improving the energy conversion efficiency and output power per unit area of ​​the thermoelectric converter 2; thus giving the invention advantages such as providing electrical energy and enhancing thermal protection.

[0051] To achieve this goal, heat exchangers can employ heat exchange methods such as film cooling, regenerative cooling, impingement jet cooling, and spray cooling. These are active cooling structures within the wall structure that utilize the flow and heat exchange characteristics of the cooling medium to absorb heat and reduce the wall temperature.

[0052] In this embodiment, the heat exchanger includes a heat-conducting layer 3 and a substrate layer 5. The heat-conducting layer 3 is made of copper alloy, and the substrate layer 5 is made of stainless steel. The heat-conducting layer 3 is directly attached to the heat-dissipating end of the thermoelectric converter 2, and the substrate layer 5 is attached to the side of the heat-conducting layer 3 away from the thermoelectric converter 2. A heat exchange chamber is formed inside the heat-conducting layer 3. Cooling medium inlet and cooling medium outlet are provided on both sides of the heat-conducting layer 3, which penetrate the heat-conducting layer 3 and connect to the heat exchange chamber.

[0053] The heat exchange chamber includes several heat exchange channels 4 with square cross-sections. The side length and spacing of each heat exchange channel 4 are equal. The two ends of each heat exchange channel 4 are connected to the cooling medium inlet and the cooling medium outlet, respectively.

[0054] In addition, flow meters, flow controllers and temperature sensors are installed at both the cooling medium inlet and outlet. Temperature sensors are installed at both the heat absorption end and the heat release end of thermoelectric converter 2. The temperature sensors can be K-type thermocouples. The power output end of thermoelectric converter 2 is connected to a power testing system.

[0055] The flow meter, flow controller, and temperature sensor are used to detect the temperature of thermoelectric converter 2, adjust the flow rate of the cooling medium, and ensure that the temperature of the heat absorption end of thermoelectric converter 2 is within the normal operating range. The power testing system is used to detect the energy conversion efficiency of thermoelectric converter 2.

[0056] On the other hand, in order to verify the feasibility of the above embodiments, refer to Figure 1 , Figure 2 , Figure 3 , Figure 4 The following provides a high-concentration thermoelectric conversion model, which includes a high-concentration layer 1, a thermoelectric converter 2, a heat-conducting layer 3, and a substrate layer 5 connected in sequence. The bottom wall of the high-concentration layer 1 is used for the surface of the aircraft, and the heat-conducting layer 3 and the substrate layer 5 are used to simulate the heat exchanger.

[0057] The relevant parameters for the design method of high-concentration thermoelectric conversion devices include:

[0058] The total heat flux of the outer wall of the aircraft, the heat concentration ratio of the high-density heat-concentrating layer 1, P=M 2 / D 2 The cross-sectional side length d of heat exchange channel 4, the number n of heat exchange channels 4, the reference temperature of the cooling medium, the heat transfer coefficient of the cooling medium, the thickness δ1 of the high-density heat-concentrating layer 1, the thickness δ2 of the thermoelectric converter 2, the thickness δ3 of the copper alloy thermally conductive layer 3, the thickness δ4 of the stainless steel substrate layer 5, and the size ratio D / L of the thermoelectric converter 2 and the substrate layer 5.

[0059] Where M is the side length of the lower base of the high-density thermal layer 1, and the area of ​​the lower base of the high-density thermal layer 1 is M. 2 D is the side length of the upper base of the high-density thermal layer 1, and the area of ​​the upper base of the high-density thermal layer 1 is D. 2 L is the side length of matrix layer 5, and the area of ​​matrix layer 5 is L. 2 .

[0060] refer to Figure 5 The design methods for high-concentration thermoelectric conversion devices include:

[0061] Step 1: Determine the total heat flux on the outer surface of the low Earth orbit spacecraft.

[0062] Step 2: Determine the heat concentration ratio P of the high-density heat-concentrating layer 1, the cross-sectional dimension d of the heat exchange channel 4, the number n of the heat exchange channels 4, the reference temperature of the cooling medium, and the heat transfer coefficient.

[0063] Step 3: Determine the thickness δ1 of the high-density heat-concentrating layer 1, the thickness δ2 of the thermoelectric converter 2, the thickness δ3 of the heat-conducting layer 3, the thickness δ4 of the substrate layer 5, and the ratio D / L of the side length of the heat-absorbing end of the thermoelectric converter 2 to the side length of the substrate layer 5 through experimental experience and theoretical calculations.

[0064] Step 4: Solve the thermoelectric-cooling integrated coupled equations based on thermoelectric theory and thermal resistance analysis.

[0065] Step 5: Calculate the heat absorption end temperature of thermoelectric converter 2 and determine whether the heat absorption end temperature of thermoelectric converter 2 is less than the maximum withstand temperature of its own material. If yes, proceed to step 6; otherwise, proceed to step 2.

[0066] Step 6: Obtain the energy conversion efficiency and output power per unit area of ​​thermoelectric converter 2, and determine whether the energy conversion efficiency is greater than the predetermined requirement. If yes, proceed to step 7; otherwise, proceed to step 3.

[0067] Step 7: Determine the parameters of the high-concentration thermoelectric conversion device, construct a high-concentration thermoelectric conversion model, and verify the accuracy of the above parameters through experiments.

[0068] In step three, since the thickness δ2 of thermoelectric converter 2 and the ratio D / L of the side length of the heat-absorbing end of thermoelectric converter 2 to the side length of the substrate layer 5 are two key parameters, which affect the heat flow distribution and electrical performance of the thermoelectric converter, the following section uses the thickness δ2 of thermoelectric converter 2 and the ratio D / L of the side length of the heat-absorbing end of thermoelectric converter 2 to the side length of the substrate layer 5 as examples to illustrate the specific steps for determining these parameters through experimental experience:

[0069] Different thermoelectric materials have different optimal thickness ranges, which mainly depend on the material's thermoelectric properties (such as Seebeck coefficient, electrical conductivity, and thermal conductivity) and operating temperature range.

[0070] The optimal thickness for bismuth telluride (Bi2Te3) thermoelectric converters is typically between 3mm and 5mm. This thickness range ensures sufficient thermoelectric conversion efficiency while avoiding increased thermal resistance due to excessive thickness.

[0071] The optimal thickness range for half-Heusler thermoelectric converters is relatively wide, typically between 8 mm and 13 mm. The thermoelectric properties of this material are better at higher temperatures, thus requiring greater thickness to accommodate higher heat flux densities.

[0072] Multi-stage thermoelectric converters are typically thicker because they require multiple layers of material to achieve higher thermoelectric conversion efficiency.

[0073] In practical applications, thermoelectric converters are usually arranged in a sandwich structure. A certain amount of space needs to be reserved in the sandwich for wiring and to avoid thermal interference between them. Experiments show that the thermoelectric converter performs best when the side length ratio D / L is 3 / 4.

[0074] In summary, those skilled in the art can determine the thickness δ2 of the thermoelectric converter 2 and the ratio D / L of the side length of the heat-absorbing end of the thermoelectric converter 2 to the side length of the substrate layer 5 through experimental experience. Other parameters, such as the thickness δ1 of the high-density heat-concentrating layer 1, the thickness δ3 of the thermally conductive layer 3, and the thickness δ4 of the substrate layer 5, can also be obtained by the same means, and will not be elaborated upon in this article.

[0075] Specifically, in step three, the theoretical calculations are explained in detail below:

[0076] By establishing a thermal resistance analysis model and combining the Seebeck effect and thermoelectric conversion performance relationship of thermoelectric materials, the temperature characteristics and power generation performance of the sandwich-type integrated cooling and power generation model are analyzed.

[0077] Thermoelectric conversion efficiency:

[0078]

[0079]

[0080] Among them, T H and T C ZT represents the temperatures of the hot and cold ends of the thermoelectric converter, respectively; S is the Seebeck coefficient; k is the thermal conductivity; σ = 1 / ρ is the electrical conductivity; and T is the absolute temperature of the thermoelectric material, which is the average temperature of the cold and hot ends of the device in the thermoelectric conversion device.

[0081] The model can examine the influence of parameters such as the thickness δ1 of the high-density heat-concentrating layer 1, the thickness δ2 of the thermoelectric converter 2, the thickness δ3 of the heat-conducting layer 3, the thickness δ4 of the substrate layer 5, and the ratio D / L of the side length of the heat-absorbing end of the thermoelectric converter 2 to the side length of the substrate layer 5 on the temperature and power generation characteristics of the integrated model.

[0082] Specifically, in step four, the thermoelectric-cooling integrated coupling equations are as follows:

[0083] T1-T2=Qδ1(1 / D-1 / M) / [k1(MD)];

[0084] T2-T3=(1-η / 2) Qδ2 / (k2D2);

[0085] T3-T4=(1-η) Qδ3 / (k3L2);

[0086] T4-Tc=(1-η) Q / (4n hc Ld);

[0087] η=(T2-T3) / T2 (sqrt(1+Z (T2+T3) / 2)-1) / (sqrt(1+Z (T2+T3) / 2)+T3 / T2);

[0088] Where Q is the total heat generated by the integrated model; Tc is the temperature of the cooling medium; hc is the heat transfer coefficient of the cooling medium; n is the number of cooling channels; d is the side length of the cooling channel; M is the side length of the bottom of the high-density heat-concentrating layer 1; D is the side length of the heat-absorbing end of the thermoelectric converter 2; L is the side length of the substrate layer 5; and η is the conversion efficiency of the thermoelectric converter, which represents the ratio of its maximum power generation to the heat flow through the thermoelectric converter.

[0089] k1-k3 are the thermal conductivity of each layer, which varies with temperature. Specifically, K1 is the thermal conductivity of the high-density heat-concentrating layer 1, K2 is the thermal conductivity of the thermoelectric converter 2, and K3 is the thermal conductivity of the heat-conducting layer 3.

[0090] T1-T4 represent the temperatures of the hot ends of each layer from top to bottom: T1 is the hot end temperature of the high-density thermal layer 1, T2 is the hot end temperature of the thermoelectric converter 2, T3 is the hot end temperature of the thermally conductive layer 3, and T4 is the hot end temperature of the substrate layer 5.

[0091] In addition, it should be noted that the temperature of the cold end of the other layer that the hot end of each layer contacts is the same. For example, T2 is both the hot end temperature of thermoelectric converter 2 and the cold end temperature of high-density heat-concentrating layer 1.

[0092] The following is an example with specific parameters.

[0093] refer to Figure 6 Given that the orbital altitude of the low Earth orbit spacecraft is 110km, the heat flux value of the frontal windward region is 21kW / m2.

[0094] The dimensions of the high-density heat-concentrating thermoelectric conversion model are as follows: the thickness δ1 of the high-density heat-concentrating layer 1 is 2-7 mm (preferably 5 mm), the thickness δ2 of the thermoelectric converter 2 is 8-13 mm (preferably 10 mm), the thickness δ3 of the heat-conducting layer 3 is 2-5 mm (preferably 4 mm), the thickness δ4 of the substrate layer 5 is 5-15 mm (preferably 10 mm), the cross-sectional dimension d of the heat exchange channel 4 is 2-5 mm (preferably 4 mm), the number of heat exchange channels 4 is 5, the side length D of the heat-absorbing end of the thermoelectric converter 2 is 20-40 mm (preferably 30 mm), the ratio of the side length L of the substrate layer 5 to the side length D of the heat-absorbing end of the thermoelectric converter 2 is 5:4~4:3 (preferably 4:3), the side length M of the bottom of the high-density heat-concentrating layer 1 is 90-134 mm, and the heat concentration ratio P of the high-density heat-concentrating layer 1 is 9:1~20:1.

[0095] The cooling medium is liquid water at a temperature of 300 K. The flow velocity of the cooling medium at the inlet is 2 m / s, corresponding to a Reynolds number of 7000. The convective heat transfer coefficient is calculated to be 8000 W / m² using the Dittus-Boelter correlation. 2 K.

[0096] The heat ratio P can be selected from a value between 9:1 and 20:1. The heat ratio P can be changed by changing the side length L of the matrix layer 5.

[0097] refer to Figure 7 , Figure 8 , Figure 9 , Figure 10 Heat transfer calculations were performed using a set of coupled equations for high-density heat transfer and cooling based on thermoelectric theory and thermal resistance analysis. The calculated hot-end temperature, hot-end temperature difference, energy conversion efficiency, and output power per unit area of ​​the two thermoelectric converters were then analyzed to show the variation of heat transfer ratio P.

[0098] As the average heat transfer coefficient of spray cooling increases, the temperature difference between the hot and cold ends of the two thermoelectric converters, the energy conversion efficiency, and the output power per unit area all increase significantly. This indicates that increasing the heat transfer ratio P significantly improves the power generation characteristics of the integrated system.

[0099] In complex thermal environments such as aircraft walls, wall temperature directly affects the safety and performance of the aircraft. To evaluate the impact of thermoelectric converter 2 on wall temperature, under the condition of keeping structural parameters, heat flux parameters, and cooling parameters constant, a comparative analysis of the aircraft wall temperature before and after the installation of thermoelectric converter 2 was conducted using a high-concentration thermoelectric conversion model. The cooling effect of thermoelectric converter 2 on the aircraft wall is as follows: Figure 11 As shown in the data, after installing thermoelectric converter 2, the temperature of the aircraft wall decreased significantly by more than 30K. Considering the temperature resistance of the high-temperature alloy material used in the aircraft wall, this temperature reduction significantly improves the cooling effect of the aircraft wall and provides an important guarantee for the safe operation of the aircraft.

[0100] Since the heat concentration ratio P is greater than 16.75:1, the hot end temperature of the two thermoelectric converters is greater than the maximum heat resistance temperature of 1123K of the semi-Hersler thermoelectric material, which does not meet the safety requirements of the device, the heat concentration ratio P of the high-concentration heat-concentrating layer 1 used in the high-concentration heat-concentrating thermoelectric conversion device is selected from a value of 9:1 to 16.75:1.

[0101] In this specific embodiment, under the premise of meeting the heat resistance conditions, the high-concentration heat transfer thermoelectric conversion model achieves a maximum energy conversion efficiency of 9.7% and a maximum output power per unit area of ​​2.03 kW / m² when the heat transfer ratio P is 16.75:1. 2 .

[0102] The above embodiments are merely exemplary embodiments of the present invention and are not intended to limit the present invention. The scope of protection of the present invention is defined by the claims. Those skilled in the art can make various modifications or equivalent substitutions to the present invention within its spirit and scope of protection, and such modifications or equivalent substitutions should also be considered as falling within the scope of protection of the embodiments of the present invention.

Claims

1. A high-concentration thermoelectric conversion device, characterized in that, include: A high-density heat-concentrating layer (1) is disposed on the inner side of the surface of the aircraft, a heat exchanger is surrounded on the inner side of the high-density heat-concentrating layer (1), and a thermoelectric converter (2) is disposed between the high-density heat-concentrating layer (1) and the heat exchanger. The heat-absorbing end of the thermoelectric converter (2) is connected to the high-density heat-concentrating layer (1), and the heat-releasing end of the thermoelectric converter (2) is connected to the wall of the heat exchanger. The high-density heat-concentrating layer (1) is shaped like a frustum or a multi-faceted frustum. The bottom of the high-density heat-concentrating layer (1) contacts the surface of the aircraft, and the top of the high-density heat-concentrating layer (1) contacts the heat-absorbing end of the thermoelectric converter (2). The side length of the bottom of the high-density heat-concentrating layer (1) is M, the side length of the heat-absorbing end of the thermoelectric converter (2) is D, and the heat concentration ratio P of the high-density heat-concentrating layer (1) is M² / D² = 9:1~16.75:

1.

2. The high-concentration thermoelectric conversion device according to claim 1, characterized in that, The high-density heat-concentrating layer (1) is shaped like a square platform with a cross-section that is a square with continuously varying side lengths.

3. The high-concentration thermoelectric conversion device according to claim 1, characterized in that, The heat exchanger includes a heat-conducting layer (3) and a substrate layer (5). The heat-conducting layer (3) is directly attached to the heat-dissipating end of the thermoelectric converter (2). The substrate layer (5) is attached to the side of the heat-conducting layer (3) away from the thermoelectric converter (2). A heat exchange chamber is formed inside the heat-conducting layer (3). Cooling medium inlet and cooling medium outlet are provided on both sides of the heat-conducting layer (3) and are connected to the heat exchange chamber.

4. The high-concentration thermoelectric conversion device according to claim 3, characterized in that, The heat exchange chamber includes several heat exchange channels (4) with square cross-sections. The side length and spacing of each heat exchange channel (4) are equal. The two ends of each heat exchange channel (4) are respectively connected to the cooling medium inlet and the cooling medium outlet.

5. The high-concentration thermoelectric conversion device according to claim 4, characterized in that, The thickness δ1 of the high-density heat-concentrating layer (1) is 2-7 mm, the thickness δ2 of the thermoelectric converter (2) is 8-13 mm, the thickness δ3 of the heat-conducting layer (3) is 2-5 mm, the thickness δ4 of the substrate layer (5) is 5-15 mm, the cross-sectional dimension d of the heat exchange channel (4) is 2-5 mm, the number n of the heat exchange channel (4) is 5, the side length D of the heat-absorbing end of the thermoelectric converter (2) is 20-40 mm, the ratio of the side length L of the substrate layer (5) to the side length D of the heat-absorbing end of the thermoelectric converter (2) is 5:4~4:3, and the side length M of the bottom of the high-density heat-concentrating layer (1) is 90-134 mm.

6. The high-concentration thermoelectric conversion device according to claim 3, characterized in that, The thermal conductive layer (3) is made of copper alloy, the substrate layer (5) is made of stainless steel, and the thermoelectric converter (2) is made of semi-Hersler alloy.

7. The high-concentration thermoelectric conversion device according to claim 3, characterized in that, Both the cooling medium inlet and the cooling medium outlet are equipped with flow meters, flow controllers and temperature sensors, and both the heat absorption end and the heat release end of the thermoelectric converter (2) are equipped with temperature sensors.

8. A design method for a high-concentration thermoelectric conversion device, characterized in that, The design method is used to design the high-concentration thermoelectric conversion device according to any one of claims 5-7, and the design method includes the following steps: Step 1: Determine the total heat flux on the outer surface of the low Earth orbit spacecraft; Step 2: Determine the heat concentration ratio P of the high-density heat-concentrating layer (1), the cross-sectional size d of the heat exchange channel (4), the number n of the heat exchange channels (4), the reference temperature of the cooling medium, and the heat transfer coefficient. Step 3: Determine the thickness δ1 of the high-density heat-concentrating layer (1), the thickness δ2 of the thermoelectric converter (2), the thickness δ3 of the heat-conducting layer (3), the thickness δ4 of the substrate layer (5), and the ratio D / L of the side length of the heat-absorbing end of the thermoelectric converter (2) to the side length of the substrate layer (5) through experimental data and theoretical calculations. Step 4: Solve the thermoelectric-cooling integrated coupled equations based on thermoelectric theory and thermal resistance analysis; Step 5: Obtain the heat absorption end temperature of the thermoelectric converter (2), and determine whether the heat absorption end temperature of the thermoelectric converter (2) is less than the maximum withstand temperature of its own material. If yes, proceed to step 6; otherwise, proceed to step 2. Step 6: Obtain the energy conversion efficiency and output power per unit area of ​​the thermoelectric converter (2), and determine whether the energy conversion efficiency is greater than the predetermined requirement. If yes, proceed to step 7; otherwise, proceed to step 3. Step 7: Determine the parameters of the high-concentration thermoelectric conversion device.

9. The design method of a high-concentration thermoelectric conversion device according to claim 8, characterized in that, The high-concentration thermoelectric conversion device comprises, in sequence, the high-concentration layer (1), the thermoelectric converter (2), the heat-conducting layer (3), and the substrate layer (5); wherein, the bottom wall of the high-concentration layer (1) is used for the surface of the aircraft, the heat-conducting layer (3) is directly attached to the heat-dissipating end of the thermoelectric converter (2), the substrate layer (5) is attached to the side of the heat-conducting layer (3) away from the thermoelectric converter (2), the heat exchange chamber is formed inside the heat-conducting layer (3), and the heat-conducting layer (3) has a cooling medium inlet and a cooling medium outlet that penetrate the heat-conducting layer (3) and connect the heat exchange chamber on both sides.

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