A construction method of a heat exchanger based on radially heterogeneous graded three-periodic minimal surface structure

Abstract

The present invention discloses a construction method of a heat exchanger based on a radially heterogeneous graded three-period minimal surface structure, comprising: dividing the space in the heat exchanger into cold fluid channels and hot fluid channels that intersect but do not interpenetrate each other through selected three-period minimal surface cells, obtaining the rectangular coordinate system equations of the three-period minimal surface cells at the same time, and hybridizing and connecting the selected different three-period minimal surface cells to obtain a newly formed hybrid function; adjusting the overall structure of the cells according to the newly formed hybrid function, and performing coordinate transformation on the rectangular coordinate system equation to obtain a target function; adjusting the number of periods of the cells in each direction in the heat exchange core based on the target function, and adding a shell outside the core to obtain a newly constructed heat exchanger. The present invention realizes a multi-stage TPMS structural design with lower stress concentration, and effectively solves the problem of reduced compactness caused by the increase in the size of the minimal surface structure, thereby improving heat exchange performance.

Description

Technical Field

[0001] The present invention relates to the technical field of heat exchangers, and in particular to a construction method of a heat exchanger based on a radially heterogeneous graded three-period minimal surface structure. Background Art

[0002] With the rapid development of additive manufacturing technology, three-periodic minimal surfaces (TPMS), as a new type of heat exchange structure, are increasingly widely used in the field of heat exchange due to their conformable 3D printing and strong convective heat transfer performance. However, the research and application of TPMS in the field of heat exchangers is still in its infancy. Most of the TPMS heat exchangers currently used are designed with standard shapes and uniform porosity. How to further improve the heat transfer performance of TPMS heat exchangers is an issue worthy of attention.

[0003] At present, the cell structure generated based on the Cartesian coordinate system can be directly filled into the rectangular space, but the rectangular shell can withstand less internal and external pressure than the traditional cylindrical shell, and the fluid flow in the cylindrical container is more uniform, which can reduce the flow unevenness. Filling the cell structure in the rectangular coordinate system directly into the cylindrical heat exchanger is very likely to cause flow dead zones and flow unevenness. The prior art discloses a modular additive manufacturing TPMS cross-flow heat exchanger suitable for cylindrical areas and generated using a TPMS structure. However, in its technical solution, after the cells are filled into the cylindrical space, the volume of the cells on the outside increases, resulting in a decrease in the compactness of the entire heat exchanger and a decrease in heat exchange performance. Summary of the invention

[0004] In order to solve the above technical problems, the present invention proposes a construction method based on a radially heterogeneous graded three-period minimal surface structure heat exchanger, which can effectively improve the compactness of conventional cells when filling the heat exchange space, and more conveniently construct a TPMS heat exchanger with a nonlinearly changing porosity and complex gradient.

[0005] To achieve the above object, the present invention provides a method for constructing a radially heterogeneous graded three-periodic minimal surface structure heat exchanger, comprising:

[0006] Dividing the space in the heat exchanger into cold fluid channels and hot fluid channels that intersect but do not interpenetrate each other through the selected three-periodic minimal surface cells, obtaining the rectangular coordinate system equation of the three-periodic minimal surface cells, and hybridizing and connecting the selected different three-periodic minimal surface cells to obtain a newly formed hybrid function;

[0007] Adjusting the overall structure of the cell according to the newly formed hybrid function, and performing coordinate transformation on the rectangular coordinate system equation to obtain the target function;

[0008] The number of cycles of cells in each direction in the heat exchange core is adjusted based on the objective function, and a shell is added outside the core to obtain a newly constructed heat exchanger.

[0009] Preferably, the structure of the three-periodic minimal surface cell is any one or several of the following structures: Diamond surface, Gyroid surface, SchwarezP surface, F-RD surface, I-WP surface, GD hybrid surface, Scherk3 surface, Neovius surface, Dprime surface, Split P surface, Lidinoid surface, FKS surface, DoubleGyroid surface, Double SD surface, first surface, second surface, third surface, fourth surface, fifth surface, sixth surface, and seventh surface.

[0010] Preferably, the selected different three-periodic minimal surface cells are hybridized and connected, comprising:

[0011] The Sigmond function is used to hybridize the three-periodic minimal surface cells. The specific method is as follows:

[0012]

[0013] In the formula, F 1 (x,y,z),F 2 (x,y,z) and F(x,y,z) represent two minimal surface functions and the resulting new heterogeneous minimal surface respectively, k is the smoothness of the transition, G is a function related to one of the variables x, y, z, and e is an exponential function with the natural constant e as the base.

[0014] Preferably, adjusting the overall structure of the cell comprises:

[0015] The wall thickness and aperture size of the overall structure are adjusted by parameter adjustment, including: the volume ratio of the two sides of the cell, the radial wall thickness distribution, the proportion of different types of cells and the number of outer cell grades.

[0016] Preferably, coordinate transformation is performed on the rectangular coordinate system equation, including:

[0017] The rectangular coordinate system equation is transformed into polar coordinates to obtain a radially transformed three-periodic minimal surface structure.

[0018] Preferably, adjusting the number of cycles of cells in each direction in the heat exchange core based on the objective function includes:

[0019] The objective function is used to adjust the number of array periods in the radial, circumferential and axial directions of the cells and the size of the heat exchange core.

[0020] Preferably, the cold fluid channel and the hot fluid channel are provided with inlet and outlet pipes at any place of the formed three-period minimal surface heat exchange core according to needs.

[0021] Preferably, the heat exchanger is made of aluminum alloy, stainless steel, titanium alloy, die steel or nickel-based high-temperature alloy, and is integrally manufactured using 3D printing technology.

[0022] Compared with the prior art, the present invention has the following advantages and technical effects:

[0023] (1) The novel heterogeneous multi-stage TPMS heat exchanger formed by the present invention is still controlled by a functional equation, and the inner surface is still smooth, with ideal connectivity and continuity; the curvature, wall thickness, period and distribution range can be conveniently adjusted through functional parameters, thereby expanding the application range of the minimal curved surface heat exchanger;

[0024] (2) The present invention proposes a TPMS filling method suitable for the heat exchange area. While improving the boundary effect, flow dead zone and flow unevenness problems of the rectangular coordinate system TPMS directly filling the heat exchanger, a shell is added outside the core body so that the heat exchanger has better structural strength and can withstand greater internal and external pressures;

[0025] (3) Based on the heterogeneous multi-stage heat exchanger of the TPMS structure, a multi-level cellular structure is proposed in the outer ring, and the Sigmond function is used to realize the smooth connection of the single-stage and multi-stage regional surfaces, so as to realize the multi-level TPMS structure design with low stress concentration. At the same time, it effectively solves the problem of reduced compactness caused by the increase in the size of the extremely small surface structure of the circumferential outer ring. The appropriate TPMS structure can be selected in different areas according to application requirements, and the complementary effects between different structures can be fully utilized, which provides greater design freedom and obtains multiple ideal performances at the same time, meets more complex application requirements, and further improves the performance of the TPMS heat exchanger. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0027] Figure 1 This is a flow chart of a construction method of a radially heterogeneous graded three-periodic minimal surface structure heat exchanger according to an embodiment of the present invention;

[0028] Figure 2 A three-dimensional structural diagram of a three-periodic minimal surface structure according to an embodiment of the present invention;

[0029] Figure 3Schematic diagram of the process of designing a TPMS heterogeneous multi-stage heat exchanger according to an embodiment of the present invention, wherein (a) is a schematic diagram of a Gyroid single cell structure, (b) is a schematic diagram of a Diamond single cell structure, (c) is a schematic diagram of a Gyroid and Gyroid array combination structure, (d) is a schematic diagram of a Gyroid and Gyroid radial graded array combination structure, (e) is a schematic diagram of a Gyroid and Diamond radial heterogeneous array combination structure, (f) is a schematic diagram of a Gyroid and Diamond radial heterogeneous graded array combination structure, and (h)-(k) are schematic diagrams of structures generated after rotation of (c)-(f), respectively;

[0030] Figure 4 Schematic diagram of the fluid domain of the TPMS heterogeneous multi-stage heat exchanger core according to an embodiment of the present invention, wherein (a)-(d) are Figure 3 Schematic diagram of the fluid domain in the structures of (h)-(k);

[0031] Figure 5 It is a three-dimensional structural diagram of the TPMS heterogeneous multi-stage heat exchanger converted into polar coordinates in an embodiment of the present invention. DETAILED DESCRIPTION

[0032] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0033] It should be noted that the steps shown in the flowcharts of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and that, although a logical order is shown in the flowcharts, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0034] The present invention proposes a construction method based on a radially heterogeneous graded three-periodic minimal surface structure heat exchanger, such as Figure 1 ,include:

[0035] The space in the heat exchanger is divided into cold fluid channels and hot fluid channels that intersect but do not penetrate each other through the selected three-periodic minimal surface cells, and the rectangular coordinate system equations of the three-periodic minimal surface cells are obtained at the same time, and the selected different three-periodic minimal surface cells are hybridized and connected to obtain a newly formed hybrid function; in this embodiment, the heat exchanger space is a cylindrical space.

[0036] The structure of the three-periodic minimal surface cell is any one or several of the Diamond surface, Gyroid surface, Schwarez P surface, F-RD surface, I-WP surface, GD hybrid surface, Scherk3 surface, Neovius surface, Dprime surface, Split P surface, Lidinoid surface, FKS surface, Double Gyroid surface, Double SD surface, first surface, second surface, third surface, fourth surface, fifth surface, sixth surface, and seventh surface structures.

[0037] Specifically, different selected three-periodic minimal surface cells are hybridized and connected to obtain a newly formed hybrid function, including:

[0038] The Sigmond function is used to hybridize the three-periodic minimal surface cells. The specific method is as follows:

[0039]

[0040] In the formula, F 1 (x,y,z),F 2 (x,y,z) and F(x,y,z) represent two minimal surface functions and the resulting new heterogeneous minimal surface respectively, k is the smoothness of the transition, G is a function related to one of the variables x, y, z, and e is an exponential function with the natural constant e as the base.

[0041] The overall structure of the cell is adjusted according to the newly formed hybrid function, and the rectangular coordinate system equation is transformed to obtain the target function;

[0042] Furthermore, the overall structure of the cell is adjusted, including:

[0043] The wall thickness and aperture size of the overall structure are adjusted by parameter adjustment, including: the volume ratio of the two sides of the cell, the radial wall thickness distribution, the proportion of different types of cells and the number of outer cell grades.

[0044] Coordinate transformations for rectangular coordinate system equations, including:

[0045] The rectangular coordinate system equation is transformed into polar coordinates to obtain the radially transformed three-periodic minimal surface structure.

[0046] The number of periods in each direction of the cells in the cylindrical heat exchange core is adjusted based on the objective function to obtain a newly constructed heat exchanger.

[0047] The number of cycles in each direction of the cells in the cylindrical heat exchange core is adjusted based on the objective function, including:

[0048] The number of array periods in the radial, circumferential and axial directions of the cell is adjusted through the objective function, and the size of the cylindrical heat exchange core is adjusted.

[0049] The cold fluid channel and the hot fluid channel are provided with inlet and outlet pipes at any place of the three-period minimal surface heat exchange core according to the needs. The heat exchanger is made of aluminum alloy, stainless steel, titanium alloy, die steel or nickel-based high temperature alloy, and is manufactured in one piece using 3D printing technology.

[0050] In order to more clearly express the technical solution of the present invention, a specific embodiment is provided below to introduce the solution:

[0051] A construction method based on radial heterogeneous graded three-periodic minimal surface structure heat exchanger, such as Figure 1 ,include:

[0052] Firstly, a hexahedral unit cell is constructed based on the three-periodic minimal surface equation. The three-periodic minimal surface unit cell structure is any one or more of the structures of Diamond surface, Gyroid surface, Schwarez P surface, F-RD surface, I-WP surface, GD hybrid surface, Scherk3 surface, Neovius surface, Dprime surface, Split P surface, Lidinoid surface, FKS surface, Double Gyroid surface, Double SD surface, first surface, second surface, third surface, fourth surface, fifth surface, sixth surface, and seventh surface (such as Figure 2 ). The governing equations of the above three-periodic minimal surface are as follows in Table 1:

[0053] Table 1

[0054]

[0055]

[0056] Among them, x, y, z are the three-dimensional coordinate values ​​of a point in the three-dimensional space, sin is the trigonometric sine function, cos is the trigonometric cosine function, and L and c are constant terms.

[0057] c represents a certain distance offset perpendicular to the curved surface. After offset and closing, a very small curved surface structure with thickness is formed. Adjusting the c value can change the volume ratio of the cold and hot fluids in the channels on both sides. At the same time, L can be adjusted to adjust the unit cell size. By adjusting the parameters to adjust the wall thickness and aperture size of the overall structure, the overall performance can be adjusted.

[0058] Furthermore, the required type of cells in the above minimal surface are selected, and in this embodiment, the selected TPMS is hybridized using Sigmond and other functions to achieve smooth transition of the three-periodic minimal surface structure at the structural connection, avoiding stress concentration at the connection.

[0059] The basic TPMS types used in this embodiment are Gyroid and Diamond.

[0060] The rectangular coordinate expressions of the two minimal surface cells are:

[0061] Gyroid:

[0062] Diamond:

[0063] In this embodiment, the structure is generated in Matlab, Python and other software. Gyroid Figure 3 (a) and Diamond Figure 3 (b) Single cell structure, where the c value is adjusted to construct nonlinearly varying porosity and different volume ratios on both sides along the hybridization direction.

[0064] The above equations are hybridized using Sigmond function:

[0065]

[0066] Among them, when F 1 and F 2 When all are Gyroid functions, Figure 3 (c) structure. At this time, adjust F 2 The L parameter is F 1 In the middle half, generate Figure 3 (d) Structure. When F 1 and F 2 When they are Gyroid and Diamond functions respectively, they are generated Figure 3 (e) structure. At this time, adjust F 2 The L parameter is F 1 In the middle half, generate Figure 3 (f) Structure. In the above four structures, the variables in G are adjusted to ensure the same hybridization direction and control F 1 and F 2 Start the connection at a location that ensures a smooth transition.

[0067] The structure is further rotated. In this embodiment, taking the z-axis as an example, the overall minimal surface configuration rectangular coordinate system is transformed into polar coordinates to obtain a radially transformed three-periodic minimal surface structure:

[0068]

[0069] In the formula, m is the number of circumferential arrangements, r is the pole diameter, is the rotation angle and θ is the polar angle.

[0070] Furthermore, the above four structures ( Figure 3 (c)-(f)) The structures generated after rotation correspond to Figure 3 There are four structures: (h), (i), (j), and (k).

[0071] The above four types of heat exchanger structures can divide the space into two parts, forming a fluid domain schematic diagram as shown in Figure 4 (a), (b), (c), and (d).

[0072] The TPMS structure obtained by the above process can adjust the size of the columnar heat exchange core by adjusting the number of array periods in the radial, circumferential, and axial directions of the cell, such as Figure 5 .

[0073] Furthermore, the cold fluid inlet and outlet and the hot fluid inlet and outlet can be set with inlet and outlet pipes at any place of the formed three-period minimal surface heat exchange core according to needs.

[0074] By filling the overall changed minimal curved surface and the overall changed cube in different directions, special-shaped heat exchangers with different filling forms can be obtained, forming an integral molding of the outer shell and the entire inner core.

[0075] The heat exchanger is made of aluminum alloy, stainless steel, titanium alloy, mold steel or nickel-based high-temperature alloy, and is manufactured in one piece using 3D printing technology (selective laser melting SLM).

[0076] For the TPMS units mentioned in Table 1, one TPMS unit cannot obtain two ideal performances at the same time. Therefore, heterogeneous TPMS is proposed to meet more complex application requirements.

[0077] The task of generating heterogeneous porous structures is to select appropriate TPMS units in different areas. However, the use of multiple TPMS structures has considerable potential for further improving the heat transfer performance of TPMS heat exchangers, making the fluid flow more uniform, thereby reducing flow resistance and improving heat transfer performance.

[0078] The hierarchical porosity can be precisely controlled through the TPMS function; for example, the parameter C can be defined as a function related to the coordinates. Figure 4 The porosity of the graded TPMS shown varies linearly. TPMS can more conveniently construct more complex gradient porous structures with nonlinearly varying porosity. Second, due to the functionally controllable properties, the inner surface remains smooth with ideal connectivity and continuity. The curvature, period, and wall thickness can be adjusted to varying degrees. TPMS can provide greater design freedom to generate graded porous structures.

[0079] Take the heterogeneous multi-stage heat exchanger composed of Gyroid and Diamond cells as an example:

[0080] The TPMS structure obtained by the above process can adjust the size of the columnar heat exchange core by adjusting the number of array periods in the radial, circumferential and axial directions of the cell. When the radial and height dimensions of two adjacent periods are different, the volume density is no longer uniform in space.

[0081] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A method for constructing a radially heterogeneous graded three-period minimal surface structure heat exchanger, characterized in that: include: Dividing the space in the heat exchanger into cold fluid channels and hot fluid channels that intersect but do not interpenetrate each other through the selected three-periodic minimal surface cells, obtaining the rectangular coordinate system equation of the three-periodic minimal surface cells, and hybridizing and connecting the selected different three-periodic minimal surface cells to obtain a newly formed hybrid function; According to the newly formed hybrid function, the overall structure of the cell is adjusted, the number of outer cell levels of the overall structure is adjusted by parameter adjustment, and the rectangular coordinate system equation is transformed to obtain the target function; The rectangular coordinate system equation is subjected to coordinate transformation, comprising: The rectangular coordinate system equation is transformed into polar coordinates to obtain a radially transformed three-periodic minimal surface structure, which is specifically: The structure is rotated, and the overall minimal surface configuration rectangular coordinate system is transformed into polar coordinates to obtain a radially transformed three-periodic minimal surface structure: In the formula, m is the number of circumferential arrangements, r is the pole diameter, is the rotation angle, θ is the polar angle; The number of cycles of cells in each direction in the heat exchange core is adjusted based on the objective function, and a shell is added outside the core to obtain a newly constructed heat exchanger, including: The objective function is used to adjust the number of array periods in the radial, circumferential and axial directions of the cells and the size of the heat exchange core.

2. The method for constructing a radially isomeric graded three-periodic minimal surface structure heat exchanger according to claim 1, characterized in that: The structure of the three-periodic minimal surface cell is any one or several of the Diamond surface, Gyroid surface, Schwarez P surface, F-RD surface, I-WP surface, GD hybrid surface, Scherk3 surface, Neovius surface, Dprime surface, Split P surface, Lidinoid surface, FKS surface, Double Gyroid surface, Double SD surface, first surface, second surface, third surface, fourth surface, fifth surface, sixth surface, and seventh surface structures.

3. The method for constructing a radially isomeric graded three-periodic minimal surface structure heat exchanger according to claim 2, characterized in that: The selected different three-periodic minimal surface cells are hybridized and connected, including: The Sigmond function is used to hybridize the three-periodic minimal surface cells. The specific method is as follows: In the formula, F1(x,y,z), F2(x,y,z) and F(x,y,z) represent two minimal surface functions and the resulting new heterogeneous minimal surfaces, respectively, k is the smoothness of the transition, G is a function related to one of the variables x, y, z, and e is an exponential function with the natural constant e as the base.

4. The method for constructing a radially isomeric graded three-periodic minimal surface structure heat exchanger according to claim 1, characterized in that: Adjusting the overall structure of the cell includes: The wall thickness and aperture size of the overall structure are adjusted by parameter adjustment, including: the volume ratio on both sides of the cell, the radial wall thickness distribution, and the proportion of different types of cells.

5. The method for constructing a radially isomeric graded three-periodic minimal surface structure heat exchanger according to claim 1, characterized in that: The cold fluid channel and the hot fluid channel are provided with inlet and outlet pipes at any place of the formed three-period minimal curved surface heat exchange core according to the needs.

6. The method for constructing a radially isomeric graded three-periodic minimal surface structure heat exchanger according to claim 1, characterized in that: The heat exchanger is made of aluminum alloy, stainless steel, titanium alloy, die steel or nickel-based high-temperature alloy, and is manufactured in one piece using 3D printing technology.

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