Reinforced convective heat exchange elbow based on TPMS structure topology optimization and design method thereof

Abstract

The present application relates to heat exchange structure technical field, specifically relates to a kind of based on TPMS structure topological optimization's reinforced convection heat exchange elbow pipe and its design method, based on TPMS structure topological optimization's reinforced convection heat exchange elbow pipe includes elbow pipe body, TPMS structure is inlaid in elbow pipe body, TPMS structure will the internal flow passage of elbow pipe body be divided into multiple fluid domains, elbow pipe body includes straight pipe section and elbow pipe section, the internal flow passage of straight pipe section is divided into multiple straight pipe section fluid domains by TPMS structure, the internal flow passage of elbow pipe section is divided into multiple elbow pipe section fluid domains by TPMS structure, the fluid domain in the elbow pipe body is by straight pipe section fluid domain and elbow pipe section fluid domain one-to-one correspondence intercommunication and is formed.The beneficial effects of the present application are that: combined with the theory of convection heat exchange, field synergy theory, turbulent flow reinforced heat exchange theory and secondary flow theory, by constructing the TPMS-elbow pipe composite flow passage with geometric self-similarity characteristics, the synergistic effect of Dean vortex strengthening and TPMS turbulent flow enhancement is realized, and higher heat exchange efficiency is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of heat exchange structure, and particularly relates to a reinforced convection heat exchange elbow based on TPMS structure topology optimization and a design method thereof. BACKGROUND

[0002] As a three-dimensional periodic topology with zero mean curvature, the triply periodic minimal surface (TPMS) structure has unique advantages in strengthening convection heat exchange. The continuous double-connected structure can generate self-similar vortex cascade, has rich vortex structure, stronger flow disturbance and larger specific surface area (up to 3-8 times of that of traditional fins), and can effectively improve the heat transfer efficiency. In addition, the TPMS has the advantages of environmental friendliness and compact structure, and therefore is widely applied to the TPMS structure in the fields of pipe shell heat exchanger, heat pipe and other reinforced heat exchange devices, and can be applied to the fields of chemical process, aerospace, environmental engineering and safety engineering.

[0003] Elbow is a common design element in engineering equipment, including elbow or U-shaped pipe with various bending angles, curvature radii and diameters. These elbow structures can increase the length of the heat exchange path and provide more heat exchange area, but the traditional elbow heat exchanger has two technical bottlenecks: one is that the flow separation generated under a specific working condition (such as a larger Dean number De ) leads to deterioration of heat transfer, resulting in a decrease in Nusselt number Nu ; the other is that the geometric characteristics of the elbow determine its limitations in further increasing the heat exchange area in the limited space of the reinforced heat exchange device.

[0004] With the promotion of global energy efficiency standards and the goal of carbon neutralization, the design of the new generation of heat exchangers is facing the demand for multi-dimensional technological innovation, that is, the energy efficiency density of the heat transfer element in the limited space is required to be doubled, and the extreme working conditions (such as 80-120℃ / cm axial temperature gradient of fuel cell stack) appear in new energy equipment. Under this background, the application of TPMS structure to the design of heat exchange elbow is one of the research directions of the new generation of miniaturized and intelligent heat exchange devices. SUMMARY

[0005] The purpose of the present application is to overcome the shortcomings of the prior art and provide a reinforced convection heat exchange elbow based on TPMS structure topology optimization and a design method thereof. The convection heat exchange theory, field synergy theory, turbulent flow heat transfer enhancement theory and secondary flow theory are combined, the TPMS-elbow composite flow channel with geometric self-similarity characteristics is constructed, the synergistic effect of Dean vortex strengthening and TPMS turbulent flow enhancement is realized, and higher heat exchange efficiency is achieved.

[0006] The purpose of the present application is achieved by the following technical solutions:

[0007] The application discloses a reinforced convection heat exchange elbow pipe design method based on TPMS structure topology optimization.

[0008] A non-uniform rational B-spline is adopted to construct a parameterized model of the elbow pipe body, and then field synergy theory analysis is performed on the parameterized model of the elbow pipe body by using a computational fluid dynamics method.

[0009] The size parameters of the elbow pipe body are determined according to design standards or specifications.

[0010] The TPMS structure is selected and the structure parameters of the TPMS structure are determined.

[0011] According to the size parameters of the elbow pipe body, a fluid domain geometric model is established by using a three-dimensional modeling software, the TPMS structure is topologically located in the fluid domain geometric model, and the TPMS structure divides the internal flow channel of the elbow pipe body into a plurality of fluid domains.

[0012] Further, the elbow pipe body comprises a straight pipe section and an elbow pipe section, the number of the elbow pipe sections is single or multiple, and when the number of the elbow pipe sections is multiple, the multiple elbow pipe sections are continuous or discontinuous.

[0013] Further, the function of the TPMS structure comprises mathematical expressions that satisfy periodic conditions and have minimum surface characteristics in three-dimensional space.

[0014] Further, the size parameters of the elbow pipe body comprise an inner diameter D, a curvature radius R, a bending angle Θ and a wall thickness Δ.

[0015] Further, the structure parameters of the TPMS structure comprise a periodic unit size l x,y,z , a porosity ε, a surface thickness δ, a magnification coefficient a and an initial phase θ, and l x,y,z / D>0, 0<δ / D≤0.5, a>0 and θ≥0.

[0016] Further, when the TPMS structure is topologically located in the fluid domain geometric model, a center line equation of the elbow pipe body is first established by using the three-dimensional modeling software, the function of the TPMS structure is embedded in the center line equation, and then a Boolean operation is performed to generate a composite fluid domain.

[0017] Further, when 0 x,y,z / D≤1, the internal flow channel of the elbow pipe body is divided into two fluid domains; and when l x,y,z / D>1, the internal flow channel of the elbow pipe body is divided into more than two fluid domains.

[0018] Further, based on the above design method, the application also provides a reinforced convection heat exchange elbow based on TPMS structure topology optimization, which comprises an elbow body, a TPMS structure embedded in the elbow body, the TPMS structure divides the internal flow channel of the elbow body into a plurality of fluid domains, the elbow body comprises a straight pipe section and an elbow section, the internal flow channel of the straight pipe section is divided into a plurality of straight pipe section fluid domains by the TPMS structure, the internal flow channel of the elbow section is divided into a plurality of elbow section fluid domains by the TPMS structure, and the fluid domains in the elbow body are formed by one-to-one correspondence and communication of the straight pipe section fluid domains and the elbow section fluid domains.

[0019] Compared with the prior art, the application has the following beneficial effects:

[0020] 1、The application combines the convection heat exchange theory, the field synergy theory, the turbulent flow reinforced heat exchange theory and the secondary flow theory, realizes the synergistic effect of Dean vortex reinforcement and TPMS turbulent flow enhancement by constructing a TPMS-elbow composite flow channel with geometric self-similarity characteristics, realizes higher heat exchange efficiency, and the Nusselt number and comprehensive heat exchange coefficient of the optimized U-shaped pipe are significantly improved compared with the traditional U-shaped pipe.

[0021] 2、The application realizes high-efficiency and low-resistance heat exchange effect by combining the TPMS structure and the reinforced heat exchange mechanism of the elbow, is suitable for various industrial heat exchange occasions, and has significant energy saving and cost reduction advantages. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 It is a whole structure schematic diagram of Diamond type U-shaped pipe in the application;

[0023] Figure 2 It is a cross section schematic diagram of Diamond type U-shaped pipe in the application;

[0024] Figure 3 It is a whole structure schematic diagram of Gyroid type 90 elbow pipe in the application;

[0025] Figure 4 It is a cross section schematic diagram of Gyroid type 90 elbow pipe in the application;

[0026] Figure 5 It is a geometric model meshing schematic diagram of Diamond type U-shaped pipe in the application;

[0027] Figure 6 It is a geometric model meshing schematic diagram of Gyroid type U-shaped pipe in the application;

[0028] Figure 7 It is a geometric model meshing schematic diagram of Schwarz type U-shaped pipe in the application;

[0029] Figure 8 In this invention, the flow velocity is 1 m / s ~ 3 m / s and the wall heat flux is 600 kW / m. 2 ~ 800 kW / m 2 PEC results of Diamond-type U-tubes compared with traditional U-tubes under operating conditions;

[0030] Figure 9 In this invention, the flow velocity is 1 m / s ~ 3 m / s and the wall heat flux is 600 kW / m. 2 ~ 800 kW / m 2 PEC results of Gyroid-type U-tubes compared with traditional U-tubes under operating conditions;

[0031] Figure 10 In this invention, the flow velocity is 1 m / s ~ 3 m / s and the wall heat flux is 600 kW / m. 2 ~ 800 kW / m 2 PEC results of Schwarz-type U-tubes compared with traditional U-tubes under operating conditions;

[0032] Figure 11 In this invention, at the flow rate U = 1 m / s ~ 3 m / s, wall heat flux q w = 700 kW / m 2 A schematic diagram showing the comparison of the Nusselt numbers of three optimized U-shaped tubes and ordinary round tubes under different operating conditions;

[0033] Figure 12 In this invention, at the flow rate U = 2 m / s, wall heat flux q w = 600 kW / m 2 ~ 800 kW / m 2 A schematic diagram showing the comparison of the Nusselt numbers of three optimized U-shaped tubes and ordinary round tubes under operating conditions.

[0034] In the diagram: 1. Straight pipe section; 11. TPMS structure of straight pipe section; 12. Fluid domain A of straight pipe section; 13. Fluid domain B of straight pipe section; 2. Bend section; 21. TPMS structure of bend section; 22. Fluid domain A of bend section; 23. Fluid domain B of bend section; 3. Pipe inlet; 31. Inlet of fluid domain A; 32. Inlet of fluid domain B; 4. Pipe outlet; 41. Outlet of fluid domain A; 42. Outlet of fluid domain B. Detailed Implementation

[0035] The present invention will be further described below with reference to the accompanying drawings, but the scope of protection of the present invention is not limited to the following description.

[0036] An enhanced convection heat transfer bend based on TPMS structure topology optimization includes a bend body with an embedded TPMS structure that divides the internal flow channel of the bend body into multiple fluid domains.

[0037] A bend is a pipe with a certain bending angle and radius of curvature in space, used to guide and change the flow direction of fluid. A bend consists of a straight pipe section 1 and a bend section 2. There can be one or more bend sections; when there are multiple bend sections, they can be continuous or discontinuous. Correspondingly, the internal flow channel of the straight pipe section 1 is divided into multiple straight pipe section fluid domains by the TPMS structure, and the internal flow channel of the bend section 2 is divided into multiple bend section fluid domains by the TPMS structure. The fluid domains inside the bend are formed by the one-to-one connection of the straight pipe section fluid domains and the bend section fluid domains.

[0038] TPMS structures are all surfaces that periodically repeat in three-dimensional space and have minimal average curvature, which, according to mathematical definition, can be expressed by a function. φ ( x , y , z ) = C To express, in the formula x , y , z For spatial coordinates, C This is a non-zero constant. The TPMS structure includes types such as Gyroid, Diamond, Schwarz, Schwarz-H, Neovius, Penta, and F-RD. The function expressions corresponding to each structure type are as follows:

[0039] Gyroid surface: φ ( x , y , z ) = sin( x cos( y ) + sin( y cos( z ) + sin( z cos( x ) = C .

[0040] Diamond surface: φ ( x , y , z ) = cos( x cos( y cos(z) - sin( x sin( y)sin( z ) = C .

[0041] Schwarz surface: φ ( x , y , z ) = cos( x ) + cos( y ) + cos( z ) = C .

[0042] Schwarz-H surface: φ ( x , y , z ) = cos( x )cos( y ) + cos( y )cos( z ) + cos( z )cos( x ) = C .

[0043] Neovius surface: φ ( x , y , z ) = cos( x ) + cos( y ) + cos( z ) + 0.3cos( x )cos( y )cos( z ) = C .

[0044] Penta surface: φ ( x , y , z ) = cos( x ) + cos( y ) + cos( z ) + 0.2cos( x+y ) + 0.2cos( y+z ) + 0.2cos( z+x ) = C .

[0045] F-RD (Fischer-Koch network) surface: φ ( x , y, z ) = cos( x cos( y cos( z ) + cos( x sin( y sin( z ) + sin( x cos( y sin( z ) + sin( x sin( y cos( z ) = C .

[0046] Taking the U-shaped tube with an embedded Diamond-type TPMS structure (i.e., the Diamond-type U-shaped tube) and the 90° tube with an embedded Gyroid-type TPMS structure (i.e., the Gyroid-type 90° tube) as examples, such as Figures 1-4 As shown, the bend body includes a straight pipe section 1, a bend section 2, a pipe inlet 3, and a pipe outlet 4. The TPMS structure inside the bend body divides the flow channel inside the bend body into fluid domain A and fluid domain B. The two ends of fluid domain A are fluid domain A inlet 31 and fluid domain A outlet 41, respectively, and the two ends of fluid domain B are fluid domain B inlet 32 ​​and fluid domain B outlet 42, respectively. Correspondingly, the TPMS structure inside the bend body is divided into a straight pipe section TPMS structure 11 and a bend section TPMS structure 21. The straight pipe section TPMS structure 11 divides the internal flow channel of the straight pipe section 1 into a straight pipe section fluid domain A12 and a straight pipe section fluid domain B13. The bend section TPMS structure 21 divides the internal flow channel of the bend section 2 into a bend section fluid domain A22 and a bend section fluid domain B23. The straight pipe section fluid domain A12 and the bend section fluid domain A22 are connected to form the entire fluid domain A, and the straight pipe section fluid domain B13 and the bend section fluid domain B23 are connected to form the entire fluid domain B.

[0047] The design of the enhanced convection heat transfer bend based on TPMS structural topology optimization includes the following steps (1) to (4):

[0048] (1) A parameterized model of the bent pipe body is constructed using non-uniform rational B-splines, and then the parameterized model of the bent pipe body is analyzed by field synergy theory using computational fluid dynamics. Field synergy theory emphasizes the synergistic effect of velocity field and temperature field. By optimizing the distribution of fluid flow, the local synergy angle is reduced, thereby improving heat transfer efficiency.

[0049] (2) Determine the dimensional parameters of the bend body according to the design standards or specifications (such as ASME B31.3 - Process Piping in the chemical industry, and NASA-STD-5012 in the aerospace industry). The dimensional parameters of the bend body include the inner diameter. D radius of curvature R Bending angle Θ Wall thickness Δ The aforementioned dimensional parameters serve as design input variables, and their specific values ​​are determined by the process requirements, load conditions, and selected specifications of the target application.

[0050] (3) Select the TPMS structure and determine its structural parameters. The structural parameters of the TPMS structure include the size of the periodic unit. l x,y,z Porosity ε Surface thickness δ Magnification factor a Initial phase θ , l x,y,z / D > 0, 0 < δ / D ≤ 0.5, a > 0, θ ≥ 0. The above structural parameters serve as design input variables, and their specific values ​​are determined by the process requirements, load conditions, and selected specifications of the target application.

[0051] (4) Based on the dimensional parameters of the bend body, a geometric model of the fluid domain is constructed using 3D modeling software, thereby creating a 3D model that accurately reflects the actual shape and size of the bend. Based on the established fluid domain geometric model, the centerline equation of the bend body, i.e., the pipe axis describing the bend's direction, is defined using 3D modeling software; the function expression of the TPMS structure is then... φ ( x , y , z Convert to cylindrical coordinate system φ ( ρ , θ , z )( ρ For a point on a cylinder, the direction of the axis is... z - Vertical distance of the axis θ The line connecting the origin of the line and that point lies in... xy - The projection lines of the surface and the orthographic projection lines x - Angle between axes, z The distance from this point x-yThe distance between the planes is then embedded into the aforementioned centerline equation to achieve TPMS modeling in cylindrical coordinates. Finally, using Boolean operations in 3D modeling software, the TPMS structure is used to "cut" the bent pipe body, obtaining a solid domain TPMS structure and multiple independent fluid domains. When 0 < l x,y,z / D When ≤ 1, the internal flow channel of the bend body is divided into 2 fluid domains; when l x,y,z / D When the value is greater than 1, the internal flow channels of the bend are divided into more than 2 fluid domains. Based on the above-mentioned enhanced convective heat transfer bend and its design method with TPMS structure topology optimization, this invention embeds the TPMS structure within the internal flow channels of the bend to form interconnected fluid domains. The TPMS structure repeats periodically in three-dimensional space, possessing high symmetry and abundant internal channels, which can improve the bend's resistance to deformation. By embedding the TPMS structure inside the bend, the disturbance and turbulence of the fluid within the bend can be effectively increased. Furthermore, the centrifugal force in the bend structure causes the fluid to generate secondary flow, forming Dean vortices and secondary vortex structures. These vortex structures can enhance fluid mixing and promote heat transfer. The TPMS structure further enhances the complexity and strength of these vortex structures, thereby improving the convective heat transfer coefficient and heat transfer efficiency.

[0052] The fundamental formula for convective heat transfer is Newton's law of cooling: Q = hA · ΔT In the formula, Q To exchange heat, h The convective heat transfer coefficient is... A For heat exchange area, ΔT The temperature difference is the factor. Increasing the heat exchange area and improving the convective heat transfer coefficient can significantly improve heat exchange efficiency.

[0053] Based on the above design method, with inner diameter D = 25.4 mm, wall thickness Δ = 0.0625 D (TPMS structural wall thickness), radius of curvature is 2.5. D The length of the straight pipe section is 12. D U-shaped tube ( Θ = 180° Δ = Taking a diameter of 2.0 mm as an example, Diamond-type TPMS structures, Gyroid-type TPMS structures, and Schwarz-type TPMS structures are embedded into the body of the bent pipe, respectively, to obtain optimized Diamond-type U-shaped pipes, Gyroid-type U-shaped pipes, and Schwarz-type U-shaped pipes. The geometric model mesh division of the three types of U-shaped pipes is as follows: Figures 5-7The heat exchange efficiency of the three U-shaped tubes was then measured as follows:

[0054] Periodic cell size of the three TPMS structures l x,y,z The curved surface thickness was 12.7 mm δ The curved surface thickness was 0.0625 D The magnification factor was 1 a The initial phase was 0 θ The periodic cell size indicates that the three TPMS structures have the same length in the three coordinate directions x , y , z The porosity of the Diamond TPMS structure was 78.06% ε The porosity of the Gyroid TPMS structure was 80.68% ε The porosity of the Schwarz TPMS structure was 85.35%.

[0055] The U-shaped tubes with the three embedded TPMS structures were filled with fluid PR-3 domestic aviation kerosene, the inlet temperature was 150℃, the flow rate was 1 m / s ~ 3 m / s, and the wall heat flux density was 600 kW / m 2 ~ 800 kW / m 2 .

[0056] According to the inlet temperature and flow rate of the fluid, the Reynolds number Re = 1.588 ×10 4 ~ 4.763 ×10 4 (all turbulent flow) was calculated, and the Nusselt number Nu = 149.5 ~ 406.0 was calculated according to the Dittus-Boelter formula.

[0057] The total Nusselt number of the elbow section was calculated by the temperature difference between the outlet and inlet of the elbow section, and the comprehensive heat exchange coefficient PEC of the U-shaped tube with the three embedded TPMS structures compared with the traditional U-shaped tube was calculated according to the formula PEC = ( Nu / Nu * ) / ( f / f * 1 / 3 ; in the formula, Nu is the total Nusselt number of the elbow section of the optimized elbow (dimensionless); Nu * is the total Nusselt number of the elbow section of the traditional U-shaped tube (dimensionless), f ​The optimized friction resistance coefficient of the bend (dimensionless). f * PEC is the frictional resistance coefficient (dimensionless) of a traditional U-shaped tube. If PEC > 1, it indicates improved heat exchange efficiency; if PEC < 1, it indicates decreased heat exchange efficiency; if PEC = 1, it indicates unchanged heat exchange efficiency.

[0058] At flow rate U = 1 m / s ~ 3 m / s, wall heat flux q w = 700 kW / m 2 Under operating conditions, the comparison results of the Nusselt numbers of the three optimized U-shaped tubes and the traditional U-shaped tube (ordinary round tube) are as follows: Figure 11 As shown; at the flow rate U = 2 m / s, wall heat flux q w = 600 kW / m 2 ~ 800 kW / m 2 Under operating conditions, the comparison results of the Nusselt numbers of the three optimized U-shaped tubes and the traditional U-shaped tube (ordinary round tube) are as follows: Figure 12 As shown, under the same operating conditions, the Nusselt number of the three optimized U-shaped tubes mentioned above was significantly improved compared to the traditional U-shaped tube. Specifically, the Diamond type U-shaped tube improved by 56.7% to 59.0%, the Gyroid type U-shaped tube improved by 48.0% to 50.7%, and the Schwarz type U-shaped tube improved by 36.2% to 38.9%.

[0059] At a flow velocity of 1 m / s to 3 m / s and a wall heat flux of 600 kW / m 2 ~800 kW / m 2 Under operating conditions, the overall heat transfer coefficient (PEC) results of the three optimized U-tubes compared to the traditional U-tube are as follows: Figures 8-10 As shown in the figure, "(-)" indicates dimensionless. Under the same operating conditions, the overall heat transfer coefficients of the three optimized U-tubes mentioned above were significantly improved compared to the traditional U-tubes. Specifically, the Diamond type U-tube improved by 36.8% to 44.8%, the Gyroid type U-tube improved by 33.0% to 40.1%, and the Schwarz type U-tube improved by 30.5% to 34.7%. The enhanced heat transfer efficiency, from highest to lowest, was Diamond type U-tube, Gyroid type U-tube, Schwarz type U-tube, and ordinary U-tube.

[0060] Correspondingly, under the same working condition, the friction resistance coefficients of the three optimized U-shaped tubes increase, wherein the Diamond type U-shaped tube increases by 32.7% ~ 53.7%, the Gyroid type U-shaped tube increases by 23.6% ~ 39.0%, and the Schwarz type U-shaped tube increases by 7.3% ~ 19.5%. The increase of the friction resistance coefficient indicates that the cost of strengthening heat exchange is to increase the flow resistance.

[0061] According to the design method of the reinforced convective heat exchange elbow pipe based on the TPMS structure topology optimization, the application combines the convective heat exchange theory, the field synergy theory, the turbulent flow reinforced heat exchange theory and the secondary flow theory, realizes the synergistic effect of Dean vortex reinforcement and TPMS turbulent flow enhancement through the construction of the TPMS-elbow pipe composite flow channel with geometric self-similarity characteristics, and realizes higher heat exchange efficiency. The design method of the application can be used for optimizing the elbow pipe made of any material meeting the strength and mechanical requirements, and only needs to ensure that the elbow pipe structure can be actually manufactured and applied. The application realizes the high-efficiency and low-resistance heat exchange effect by combining the TPMS structure and the elbow pipe reinforced heat exchange mechanism, has significant energy saving and cost reduction advantages, is not only beneficial to improving the energy utilization rate and reducing the operation cost, but also can simplify the equipment application conditions, makes the installation and maintenance process more convenient, and is suitable for the harsh industrial scenes such as the aviation engine fuel cooling and the chemical process waste heat recovery.

[0062] Although the embodiments of the application have been shown and described, it is to be understood that for the purpose of the present application, the embodiments can be substantially changed without departing from the spirit and the scope of the present application, the scope of the present application being defined by the appended claims and their equivalents.

Claims

1. A method for designing a TPMS structure topology-optimized reinforced convective heat exchange elbow, characterized in that: The TPMS structure topology-optimized reinforced convective heat exchange elbow comprises an elbow body, the TPMS structure is embedded in the elbow body, the TPMS structure divides the internal flow passage of the elbow body into multiple fluid domains, the elbow body comprises a straight pipe section and an elbow section, the internal flow passage of the straight pipe section is divided by the TPMS structure into multiple straight pipe section fluid domains, the internal flow passage of the elbow section is divided by the TPMS structure into multiple elbow section fluid domains, and the fluid domains inside the elbow body are formed by one-to-one correspondence and communication of the straight pipe section fluid domains and the elbow section fluid domains; The method for designing the TPMS structure topology-optimized reinforced convective heat exchange elbow comprises the following steps: A non-uniform rational B-spline is used to construct a parametric model of the elbow body, and then a field synergy theory analysis is performed on the parametric model of the elbow body by a computational fluid dynamics method; The size parameters of the elbow body are determined according to design standards or specifications; The TPMS structure is selected and the structure parameters of the TPMS structure are determined; According to the size parameters of the elbow body, a fluid domain geometric model is established by a three-dimensional modeling software, the TPMS structure is topologically mapped into the fluid domain geometric model, and the TPMS structure divides the internal flow passage of the elbow body into multiple fluid domains; The size parameter of the bent pipe body includes an inner diameter D, and the structure parameter of the TPMS structure includes a period unit size l x,y,z When 0 < l x,y,z / D ≤ 1, the internal flow passage of the bent pipe body is divided into two fluid domains; when l x,y,z / D > 1, the internal flow passage of the bent pipe body is divided into more than two fluid domains.

2. The method of claim 1, wherein the method is characterized by: The elbow body comprises a straight pipe section and an elbow section, the number of the elbow sections is single or multiple, and when the number of the elbow sections is multiple, the multiple elbow sections are continuous or discontinuous.

3. The method of claim 1, wherein the method is characterized by: The function of the TPMS structure comprises a mathematical expression that satisfies a periodic condition in a three-dimensional space and has a minimum surface characteristic.

4. The method of claim 1, wherein: The size parameters of the elbow body further comprise a curvature radius R, a bending angle Θ, and a wall thickness Δ.

5. The method of claim 1, wherein: The structural parameters of the TPMS structure further include porosity ε, curved surface thickness δ, magnification factor a, initial phase θ, and l x,y,z / D > 0, 0 < δ / D ≤ 0.5, a > 0, θ ≥ 0.

6. The method of claim 3, wherein: When the TPMS structure is topologically mapped into the fluid domain geometric model, a center line equation of the elbow body is first established by the three-dimensional modeling software, the function of the TPMS structure is embedded in the center line equation, and then a Boolean operation is performed to generate a composite fluid domain.

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