Reinforced convection heat exchange elbow pipe based on TPMS structure topological optimization and design method thereof

Abstract

The invention relates to the technical field of heat exchange structures, in particular to an enhanced convection heat exchange elbow based on TPMS structure topological optimization and a design method thereof.The enhanced convection heat exchange elbow based on TPMS structure topological optimization comprises an elbow body, a TPMS structure is embedded in the elbow body, the TPMS structure divides an internal flow channel of the elbow body into a plurality of fluid domains, and the fluid domains are arranged in the elbow body. The elbow pipe body comprises a straight pipe section and an elbow pipe section, an internal flow channel of the straight pipe section is divided into a plurality of straight pipe section fluid areas by a TPMS structure, an internal flow channel of the elbow pipe section is divided into a plurality of elbow pipe section fluid areas by the TPMS structure, and the fluid areas in the elbow pipe body are formed by communicating the straight pipe section fluid areas with the elbow pipe section fluid areas in a one-to-one correspondence mode. The TPMS-elbow composite flow channel has the beneficial effects that the convective heat exchange theory, the field synergy theory, the turbulence enhancement heat exchange theory and the secondary flow theory are combined, the TPMS-elbow composite flow channel with geometric self-similar characteristics is constructed, the synergy effect of Dean vortex enhancement and TPMS turbulence enhancement is achieved, and higher heat exchange efficiency is achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of heat exchange structure, in particular 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. Its 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 traditional fins), and can effectively improve the heat transfer efficiency. In addition, TPMS has the advantages of environmental friendliness and compact structure, so TPMS structure is widely used in shell-and-tube heat exchangers, heat pipes and other reinforced heat exchange devices, and can be applied to chemical processes, 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 caused by specific working conditions (such as larger Dean number De ) leads to deterioration of heat transfer, resulting in a decrease in Nusselt number Nu ; the second is the limitation of the elbow geometry 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 it needs to adapt to the extreme working conditions (such as 80-120℃ / cm axial temperature gradient of fuel cell stack) in new energy equipment. Under this background, the application of TPMS structure in 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, which combines convection heat transfer theory, field synergy theory, turbulent flow heat transfer enhancement theory and secondary flow theory. By constructing a TPMS-elbow composite flow channel with geometric self-similarity characteristics, the synergistic effect of Dean vortex strengthening and TPMS turbulent flow enhancement is realized, and higher heat transfer efficiency is achieved.

[0006] The purpose of the present application is achieved by the following technical solutions: A kind of TPMS structure topology optimization-based enhanced convection heat exchange elbow design method, comprising: The parameterized model of the elbow body is constructed using non-uniform rational B-spline, and then field synergy theory analysis is performed on the parameterized model of the elbow body by 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 geometry model is established by a three-dimensional modeling software, the TPMS structure is topologically mapped into the fluid domain geometry model, and the TPMS structure divides the internal flow passage of the elbow body into multiple fluid domains.

[0007] Further, the elbow body includes a straight pipe section and an elbow section, the number of elbow sections is single or multiple, and when the number of elbow sections is multiple, the multiple elbow sections are continuous or discontinuous.

[0008] Further, the function of the TPMS structure includes all mathematical expressions that satisfy the periodic condition in three-dimensional space and have minimal surface characteristics.

[0009] Further, the size parameters of the elbow body include inner diameter D, curvature radius R, bending angle Θ and wall thickness Δ.

[0010] Further, the structure parameters of the TPMS structure include periodic unit size l x,y,z , porosity ε, surface thickness δ, magnification factor a and initial phase θ, l x,y,z / D>0, 0<δ / D≤0.5, a>0, θ≥0.

[0011] Further, when the TPMS structure is topologically mapped into the fluid domain geometry model, the centerline equation of the elbow body is first established by the three-dimensional modeling software and the function of the TPMS structure is embedded in the centerline equation, and then Boolean operation is performed to generate a composite fluid domain.

[0012] Further, when 0 x,y,z / D≤1, the internal flow passage of the elbow body is divided into two fluid domains; when l x,y,z / D>1, the internal flow passage of the elbow body is divided into more than two fluid domains.

[0013] 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.

[0014] Compared with the prior art, the application has the following beneficial effects: 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 through the construction of the TPMS-elbow composite flow channel with the geometric self-similarity characteristics, realizes higher heat exchange efficiency, and the Nusselt number and the comprehensive heat exchange coefficient of the optimized U-shaped pipe are significantly improved compared with the traditional U-shaped pipe.

[0015] 2、The application realizes the 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 the advantages of significant energy saving and cost reduction. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 It is a whole structure schematic view of the Diamond type U-shaped pipe in the application; Figure 2 It is a cross section schematic view of the Diamond type U-shaped pipe in the application; Figure 3 It is a whole structure schematic view of the Gyroid type 90° elbow in the application; Figure 4 It is a cross section schematic view of the Gyroid type 90° elbow in the application; Figure 5 It is a geometric model meshing schematic view of the Diamond type U-shaped pipe in the application; Figure 6 It is a geometric model meshing schematic view of the Gyroid type U-shaped pipe in the application; Figure 7 It is a geometric model meshing schematic view of the Schwarz type U-shaped pipe in the application; Figure 8 It is a whole structure schematic view of the Diamond type U-shaped pipe in the application, wherein the flow velocity is 1 m / s ~ 3 m / s, and the wall surface heat flux is 600 kW / m 2 ~ 800 kW / m 2PEC results of the Diamond type U-tube compared with the traditional U-tube under the working condition; Figure 9 For the application, under the working condition of the flow rate of 1 m / s ~ 3 m / s and the wall heat flux of 600 kW / m 2 ~ 800 kW / m 2 PEC results of the Gyroid type U-tube compared with the traditional U-tube under the working condition; Figure 10 For the application, under the working condition of the flow rate of 1 m / s ~ 3 m / s and the wall heat flux of 600 kW / m 2 ~ 800 kW / m 2 PEC results of the Schwarz type U-tube compared with the traditional U-tube under the working condition; Figure 11 For the application, under the working condition of the flow rate U = 1 m / s ~ 3 m / s and the wall heat flux q w = 700 kW / m 2 Comparison results of the Nusselt number of the three optimized U-tubes and the ordinary round tube under the working condition; Figure 12 For the application, under the working condition of the flow rate U = 2 m / s and the wall heat flux q w = 600 kW / m 2 ~ 800 kW / m 2 Comparison results of the Nusselt number of the three optimized U-tubes and the ordinary round tube under the working condition.

[0017] In the figure, 1 is a straight pipe section, 11 is a straight pipe section TPMS structure, 12 is a straight pipe section fluid domain A, 13 is a straight pipe section fluid domain B, 2 is a bend pipe section, 21 is a bend pipe section TPMS structure, 22 is a bend pipe section fluid domain A, 23 is a bend pipe section fluid domain B, 3 is a pipeline inlet, 31 is a fluid domain A inlet, 32 is a fluid domain B inlet, 4 is a pipeline outlet, 41 is a fluid domain A outlet, and 42 is a fluid domain B outlet. DETAILED DESCRIPTION

[0018] The application will be further described below in combination with the drawings, but the protection scope of the application is not limited to the following description.

[0019] A reinforced convection heat exchange bend pipe based on TPMS structure topology optimization, comprising a bend pipe body, a TPMS structure is embedded in the bend pipe body, and the TPMS structure divides the internal flow channel of the bend pipe body into multiple fluid domains.

[0020] The bend pipe body is all the pipe with certain bending angle and curvature radius in space, which is used to guide and change the flow direction of fluid. The bend pipe body includes straight pipe section 1 and bend pipe section 2, the number of bend pipe sections is single or multiple, and the multiple bend pipe sections 2 are continuous or discontinuous. Correspondingly, the internal flow channel of the straight pipe section 1 is divided into multiple straight pipe fluid domains by the TPMS structure, the internal flow channel of the bend pipe section 2 is divided into multiple bend pipe fluid domains by the TPMS structure, and the fluid domains in the bend pipe body are formed by the straight pipe fluid domains and the bend pipe fluid domains in one-to-one correspondence.

[0021] The TPMS structure is all the surface with periodic repetition and minimum average curvature in three-dimensional space, which can be expressed by the function φ ( x , y , z ) = C , wherein x 、 y 、 z are space coordinates, C is a non-zero constant. The TPMS structure includes Gyroid, Diamond, Schwarz, Schwarz-H, Neovius, Penta, F-RD and the like, and the function expression corresponding to each structure type is as follows: Gyroid surface: φ ( x , y , z ) = sin( x )cos( y ) + sin( y )cos( z ) + sin( z )cos( x ) = C .

[0022] Diamond surface: φ ( x , y , z ) = cos( x )cos( y )cos(z) - sin( x )sin( y )sin( z ) = C .

[0023] Schwarz surface: φ ( x , y , z ) = cos(x ) + cos( y ) + cos( z ) = C .

[0024] Schwarz-H surface: φ ( x , y , z ) = cos( x )cos( y ) + cos( y )cos( z ) + cos( z )cos( x ) = C .

[0025] Neovius surface: φ ( x , y , z ) = cos( x ) + cos( y ) + cos( z ) + 0.3cos( x )cos( y )cos( z ) = C .

[0026] 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 .

[0027] 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 .

[0028] Take the U-shaped tube with an embedded Diamond-type TPMS structure (i.e., Diamond-type U-shaped tube) and the 90° tube with an embedded Gyroid-type TPMS structure (i.e., Gyroid-type 90° tube) as examples, as shown in FIG. 1, the elbow body includes a straight pipe segment 1, an elbow segment 2, a pipeline inlet 3, and a pipeline outlet 4. The TPMS structure inside the elbow body divides the flow passage inside the elbow body as a whole 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. 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 elbow body is divided into straight pipe segment TPMS structure 11 and elbow segment TPMS structure 21. The straight pipe segment TPMS structure 11 divides the internal flow passage of the straight pipe segment 1 into straight pipe segment fluid domain A 12 and straight pipe segment fluid domain B 13. The elbow segment TPMS structure 21 divides the internal flow passage of the elbow segment 2 into elbow segment fluid domain A 22 and elbow segment fluid domain B 23. The straight pipe segment fluid domain A 12 and the elbow segment fluid domain A 22 correspondingly communicate to form the whole fluid domain A. The straight pipe segment fluid domain B 13 and the elbow segment fluid domain B 23 correspondingly communicate to form the whole fluid domain B. Figures 1-4

[0029] When designing the above-mentioned reinforced convective heat exchange elbow based on TPMS structure topology optimization, the following steps (1) to (4) are included: (1) Construct a parametric model of the elbow body using non-uniform rational B-splines, and then perform field synergy theory analysis on the parametric model of the elbow body by computational fluid dynamics method. Field synergy theory emphasizes the synergy of velocity field and temperature field, optimizes the distribution of fluid flow, reduces the local synergy angle, and thus improves the heat exchange efficiency.

[0030] (2) Determine the size parameters of the elbow body according to design standards or specifications (such as ASME B31.3 - Process Piping in the chemical industry and NASA-STD-5012 in the aerospace field). The size parameters of the elbow body include inner diameter D , curvature radius R , bending angle Θ , and wall thickness Δ . The above-mentioned size parameters are used as design input variables, and their specific values are determined by the process requirements of the target application, load conditions, and selected specifications.

[0031] ​(3) Select the TPMS structure and determine the structural parameters of the TPMS structure. The structural parameters of the TPMS structure include the periodic unit size l x,y,z , porosity ε , surface thickness δ , amplification factor a , initial phase θ , l x,y,z / D > 0, 0 < δ / D ≤ 0.5, a > 0, θ ≥ 0. The above structural parameters are used as design input variables, and their specific values ​​are determined by the process requirements, load conditions and selected specifications of the target application.

[0032] (4) According to the dimensional parameters of the elbow body, use 3D modeling software to build a geometric model of the fluid domain, thereby creating a 3D model that accurately reflects the actual shape and size of the elbow. Based on the established fluid domain geometric model, the centerline equation of the elbow body is defined by the 3D modeling software, that is, the pipeline axis that describes the direction of the elbow; the function expression of the TPMS structure is converted into φ ( x , y , z ) to cylindrical coordinate system φ ( ρ , θ , z )( ρ is the distance between a point on the cylinder and the axis z - perpendicular distance of the axis, θ The line connecting the origin and the point is xy -The projection line of the surface and the positive x - the angle between the axes, z The point distance x-y The distance between the planes is then embedded into the centerline equation above to achieve TPMS modeling in the cylindrical coordinate system. Finally, through Boolean operations in the 3D modeling software, the TPMS structure is used to "cut" the elbow body to obtain a solid domain TPMS structure and multiple independent fluid domains. When 0 < l x,y,z / D ≤ 1, the number of fluid domains into which the internal flow channel of the elbow body is divided is 2; when l x,y,z / D> 1, the number of fluid domains into which the internal flow channel of the elbow body is divided is greater than 2. Based on the enhanced convective heat transfer elbow and its design method based on the above-mentioned TPMS structural topology optimization, the present invention embeds the TPMS structure in the internal flow channel of the elbow to form a connected fluid domain. The TPMS structure repeats periodically in three-dimensional space, has a high degree of symmetry and abundant internal channels, and can enhance the deformation resistance of the elbow. By embedding the TPMS structure inside the elbow, the disturbance and turbulence of the fluid in the elbow can be effectively increased, and the centrifugal force in the elbow structure will cause the fluid to generate secondary flow, forming Dean vortex and secondary vortex structures. The vortex structure can enhance the mixing of the fluid 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.

[0033] The basic formula for convective heat transfer is Newton's law of cooling: Q = hA · ΔT , where Q To exchange heat, h is the convective heat transfer coefficient, A is the heat exchange area, ΔT The heat transfer efficiency can be significantly improved by increasing the heat transfer area and improving the convection heat transfer coefficient.

[0034] According to the above design method, the inner diameter D = 25.4 mm, wall thickness Δ = 0.0625 D (TPMS structure wall thickness), curvature radius is 2.5 D , the length of the straight pipe section is 12 D U-shaped tube ( Θ = 180°, Δ = 2.0 mm) as an example, the Diamond type TPMS structure, Gyroid type TPMS structure and Schwarz type TPMS structure are embedded in the curved tube body respectively, and the optimized Diamond type U-shaped tube, Gyroid type U-shaped tube and Schwarz type U-shaped tube are obtained. The geometric model mesh division of the three U-shaped tubes is as follows Figures 5-7 As shown, the heat transfer efficiency of the three U-shaped tubes was then measured as follows: Periodic unit sizes of three TPMS structures l x,y,z Both are 12.7 mm, curved surface thickness δ Both are 0.0625 D , amplification factor a Both are 1, initial phase θ are all 0, where the periodic unit size represents the three TPMS structures in x 、 y, z Three coordinate directions have the same length, the porosity of the Diamond type TPMS structure ε is 78.06%, the porosity of the Gyroid type TPMS structure ε is 80.68%, and the porosity of the Schwarz type TPMS structure is 85.35%.

[0035] The U-shaped tube of the above three embedded TPMS structures is filled with fluid PR-3 domestic aviation kerosene, the inlet temperature is 150℃, the flow rate is 1 m / s ~ 3 m / s, and the wall heat flux density is 600 kW / m 2 ~ 800 kW / m 2 .

[0036] According to the inlet temperature and flow rate of the fluid, the Reynolds number Re = 1.588 ×10 4 ~ 4.763 ×10 4 (all are turbulent flow) is calculated, and the Nusselt number Nu = 149.5 ~ 406.0 is calculated according to the Dittus-Boelter formula.

[0037] The total Nusselt number of the elbow section is calculated by the temperature difference between the outlet and the inlet of the elbow section, and the comprehensive heat transfer coefficient PEC of the above three embedded TPMS structure U-shaped tubes compared with the traditional U-shaped tube is 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 is the friction resistance coefficient of the optimized elbow (dimensionless); f * is the friction resistance coefficient of the traditional U-shaped tube (dimensionless). If PEC > 1, it indicates that the heat exchange efficiency is improved; if PEC < 1, it indicates that the heat exchange efficiency is deteriorated; and if PEC = 1, it indicates that the heat exchange efficiency is unchanged.

[0038] Under the flow rate U = 1 m / s ~ 3 m / s and the wall heat flux q w = 700 kW / m 2The Nusselt number of the three optimized U-tubes and the conventional U-tube (ordinary round tube) under the working condition of the flow velocity of 2 m / s and the wall heat flux of 600 kW / m Figure 11 U q w 2 2 The Nusselt number of the three optimized U-tubes and the conventional U-tube (ordinary round tube) under the working condition of the flow velocity of 2 m / s and the wall heat flux of 600 kW / m Figure 12 Under the same working condition, the Nusselt number of the three optimized U-tubes is significantly improved, wherein the Diamond-type U-tube is improved by 56.7% to 59.0%, the Gyroid-type U-tube is improved by 48.0% to 50.7%, and the Schwarz-type U-tube is improved by 36.2% to 38.9%.

[0039] Under the working condition of the flow velocity of 1 m / s to 3 m / s and the wall heat flux of 600 kW / m 2 2 The comprehensive heat exchange coefficient PEC of the three optimized U-tubes and the conventional U-tube under the working condition of the flow velocity of 1 m / s to 3 m / s and the wall heat flux of 600 kW / m Figures 8-10 to 800 kW / m is shown in FIG. 6, wherein the "(—)" in the figure represents dimensionless. Under the same working condition, the comprehensive heat exchange coefficient of the three optimized U-tubes is significantly improved compared with the conventional U-tube, wherein the Diamond-type U-tube is improved by 36.8% to 44.8%, the Gyroid-type U-tube is improved by 33.0% to 40.1%, and the Schwarz-type U-tube is improved by 30.5% to 34.7%. The heat exchange efficiency from high to low is Diamond-type U-tube, Gyroid-type U-tube, Schwarz-type U-tube, and ordinary U-tube.

[0040] Correspondingly, under the same working condition, the friction resistance coefficient of the three optimized U-tubes is increased, wherein the Diamond-type U-tube is increased by 32.7% to 53.7%, the Gyroid-type U-tube is increased by 23.6% to 39.0%, and the Schwarz-type U-tube is increased by 7.3% to 19.5%. The increase of the friction resistance coefficient indicates that the cost of the heat exchange enhancement is the increase of the flow resistance.

[0041] ​​​​​According to the design method of the reinforced convection heat exchange elbow pipe based on the TPMS structure topology optimization, the convection heat exchange theory, the field synergy theory, the turbulent flow reinforced heat exchange theory and the secondary flow theory are combined, the TPMS-elbow pipe composite flow channel with the geometric self-similarity characteristics is constructed, the synergistic effect of the Dean vortex reinforcement and the TPMS turbulent flow enhancement is realized, and higher heat exchange efficiency is realized. 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 design method of the application realizes the high-efficiency, low-resistance heat exchange effect by combining the TPMS structure and the reinforced heat exchange mechanism of the elbow pipe, has the advantages of significant energy saving and cost reduction, is beneficial to improving the energy utilization rate and reducing the operation cost, 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.

[0042] Although the embodiments of the present application have been shown and described, it is to be understood that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A design method for enhanced convection heat transfer elbow based on TPMS structural topology optimization, characterized in that: include: The parametric model of the elbow body is constructed using non-uniform rational B-splines, and then the field synergy theory analysis of the parametric model of the elbow body is carried out using the computational fluid dynamics method. Determine the size parameters of the elbow body according to the design standards or specifications; Select the TPMS structure and determine the structural parameters of the TPMS structure; According to the dimensional parameters of the elbow body, a fluid domain geometric model is established using 3D modeling software, and the TPMS structure is topologically integrated into the fluid domain geometric model, so that the TPMS structure divides the internal flow channel of the elbow body into multiple fluid domains.

2. The method for designing an enhanced convection heat transfer elbow based on TPMS structural topology optimization according to claim 1 is characterized in that: The elbow body includes a straight pipe section and a curved pipe section. The number of the curved pipe sections is single or multiple. When the number of the curved pipe sections is multiple, the multiple curved pipe sections are continuous or discontinuous.

3. The design method for enhanced convection heat transfer elbow based on TPMS structural topology optimization according to claim 1 is characterized in that: The functions of the TPMS structure include all mathematical expressions that meet periodic conditions in three-dimensional space and have minimal surface characteristics.

4. The design method for enhanced convection heat transfer elbow based on TPMS structural topology optimization according to claim 1 is characterized in that: The dimensional parameters of the elbow body include inner diameter D, curvature radius R, bending angle Θ, and wall thickness Δ.

5. The design method for enhanced convection heat transfer elbow based on TPMS structural topology optimization according to claim 1 is characterized in that: The structural parameters of the TPMS structure include the periodic unit size 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.

6. The method for designing an enhanced convection heat transfer elbow based on TPMS structural topology optimization according to claim 3 is characterized in that: When topologically embedding the TPMS structure into the fluid domain geometric model, the centerline equation of the elbow body is first established using 3D modeling software, and the function of the TPMS structure is embedded in the centerline equation. Then, Boolean operations are performed to generate a composite fluid domain.

7. The method for designing an enhanced convection heat transfer elbow based on TPMS structural topology optimization according to claim 5 is characterized in that: When 0 < l x,y,z / D ≤ 1, the number of fluid domains into which the internal flow channel of the elbow body is divided is 2; when l x,y,z When / D > 1, the number of fluid domains into which the internal flow channel of the elbow body is divided is greater than 2.

8. An enhanced convection heat exchange elbow based on TPMS structural topology optimization, comprising an elbow body, characterized in that: A TPMS structure is embedded in the elbow body, which divides the internal flow channel of the elbow body into multiple fluid domains. The elbow body includes a straight pipe section and a curved pipe section. The internal flow channel of the straight pipe section is divided into multiple straight pipe section fluid domains by the TPMS structure, and the internal flow channel of the curved pipe section is divided into multiple curved pipe section fluid domains by the TPMS structure. The fluid domain inside the elbow body is formed by the straight pipe section fluid domain and the curved pipe section fluid domain being connected one-to-one.

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