Design method of TPMS (Tire Pressure Monitor System) heat exchanger core body for realizing local resistance reduction design

Abstract

The invention provides a method for designing a TPMS (Tire Pressure Monitor System) heat exchanger core body for realizing local resistance reduction design, and belongs to the technical field of heat exchangers. According to the design method for the 3D printing modularized TPMS heat exchanger core body, local resistance reduction design is achieved through a parameterization method, a traditional Gyandroid structure expression serves as the basis, parameterization expression is conducted on an offset parameter C item in the Gyandroid structure expression through a Sigmoid function, continuous change of the relative volume of an inlet area and an outlet area of the core body is achieved, and the local resistance reduction design is achieved. And the purpose of reducing resistance of the core inlet and outlet is achieved. Based on a parameterization method, TPMS curved surface offset with controllable local parameters is realized; the TPMS heat exchanger module is locally adjusted by applying a parameterized curved surface offset scheme, continuous change of the relative volume of single fluid is realized by changing cell elements at an inlet and an outlet of the TPMS heat exchanger module, sudden change of the flow area at the inlet and the outlet of cold fluid and hot fluid of the TPMS heat exchanger module is reduced, and local energy loss is effectively reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of heat exchangers and relates to a design method for a TPMS heat exchanger core that realizes a local drag reduction design, and in particular to a design method for a 3D-printed modular TPMS heat exchanger core that realizes a local drag reduction design by applying a parametric method. Background Art

[0002] The Triple Periodic Minimal Surface (TPMS) heat exchanger is a new type of high-efficiency heat exchanger that has emerged in recent years. Its manufacturing method is additive manufacturing technology (3D printing technology). A minimal surface is a surface with a constant average curvature of 0 and the smallest area within a given boundary. It is represented by implicit function approximation through a combination of trigonometric functions. For example, the Gyroid surface expression is:

[0003]

[0004] Where T is the period size, the surface G(x,y,z)=C divides the entire space Ω into two parts, Ω1: G(x,y,z)<C, Ω2: G(x,y,z)>C, let the volume of Ω1 be V1, the volume of Ω2 be V2, and the volume of Ω is V=V1+V2. The parameter C determines the relative size of V1 and V2, and defines the relative volume of Ω1 The relative volume ε of the TPMS structure is directly related to the offset parameter C [Shi Z, Wang W, Gao J. Parametric Design of Porous Scaffold with Deformed TriplyPeriodic Minimal Surface. J Comput-Aided Design Comput Graphics, 2022, 34(06): 970-976], [Feng J, Fu J, Shang C, et al. Porous scaffold design by solid T-splines and triply periodic minimal surfaces. Computer Methods in Applied Mechanics and Engineering, 2018, 336: 333-352]. By changing C, the relative volume can be locally changed. Figure 1 For the Gyroid surface, ε = 0.4186C + 0.502 (-1 < C < 1). When C = 1.5, ε = 100%, and the Ω1 portion occupies the entire space Ω. When generating the heat exchanger core, the parameters C1 and C2 satisfy (C1 < C2), and the core wall satisfies the expression C1 < G(x, y, z) < C2.

[0005] At present, in the TPMS heat exchanger design patents such as the cross-flow heat exchanger based on TPMS structure disclosed in Chinese invention patent CN117570763A and the heat exchanger based on three-periodic minimal surface structure and its working method disclosed in Chinese invention patent CN115752025A, the core inlet and outlet structures are mostly directly closed by adding solid walls to another fluid domain. Figure 2 This type of inlet and outlet has a large local pressure drop due to the sudden change in flow cross section. Summary of the Invention

[0006] In response to the problems existing in the existing technology, the present invention proposes a design method for a 3D-printed modular TPMS heat exchanger that uses a parametric method to achieve local drag reduction design. A local drag reduction design applied to the TPMS heat exchanger is provided, which can effectively reduce the degree of change in the flow cross-sectional area when the heat exchanger head enters the heat exchange core, thereby reducing the local pressure drop.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] A design method for a TPMS heat exchanger core that achieves localized drag reduction is disclosed. Specifically, a design method for a 3D-printed modular TPMS heat exchanger core that uses a parametric approach to achieve localized drag reduction. The design method is based on a traditional Gyroid structural expression. By applying a Sigmoid function to parameterize the offset parameter C in the Gyroid structural expression, the relative volume of the core inlet and outlet regions is continuously varied, thereby achieving the purpose of reducing drag at the core inlet and outlet. Figure 3 Specifically:

[0009] The Gyroid structure is a three-periodic minimal surface described by the level set equation, which can be used to generate the cold / hot fluid domain model. Specifically:

[0010] The Gyroid level set equation is:

[0011]

[0012] Where T is the period, and C is the parameter controlling the degree of surface offset. The surface G(x,y,z) = C divides the entire space Ω into two parts: Ω1: G(x,y,z) < C, and Ω2: G(x,y,z) > C. In this paper, Ω1 is taken as the hot fluid and Ω2 as the cold fluid to generate the fluid domain model. The volume of Ω1 is V1, and the volume of Ω2 is V2. The volume of Ω is V = V1 + V2. The offset parameter C determines the relative sizes of V1 and V2.

[0013] The relative volume of Ω1 is given by the formula It is found that the relative volume ε of the TPMS structure is directly related to the offset parameter C. In the Gyroid structure, when ε1 and the offset parameter C satisfy the relationship ε1=0.4186×C+0.502.

[0014] The Sigmoid function S i (x) is expressed as: Among them, β i Indicates S i (x) maximum value; S i (x) function value ranges from 0 to β i Change; k i Indicates S i (x) The speed of change of the function value, positive or negative, represents S i (x) Function monotonicity; f i (x) represents the inlet and outlet boundaries of the core, where the subscript i indicates boundary i, and x represents the independent variable (when the boundary has two-dimensional characteristics, the independent variables are x and y); j represents a point on the boundary i, x = x j When f i (x j )=0,

[0015] The k i Impact S i (x) The function value changes quickly, thus controlling the range of the offset. To quantify the range of surface offset, the coordinate x is taken when c = 0.001. 0.001 , define the surface offset area at boundary i as x j represents a point on the boundary i.

[0016] The Sigmoid function is used to parameterize the offset parameter C in the Gyroid structure expression, that is, At this time, C=S within the boundary i (x) = 0, outside the boundary C = S i (x) = β i , Sigmoid function S i (x) makes the offset parameter C at the boundary change continuously. Based on the relationship between the relative volume ε and the offset parameter C, the relative volume at the boundary changes continuously, reducing the energy loss caused by the sudden change of the flow cross section at the inlet and outlet.

[0017] The Sigmoid function S i (x) contains only local information, only at the boundary f i The function value at (x) varies from 0 to β i Change within the range, so that the outside of the boundary is β i, the boundary (inside the core) is 0. The TPMS heat exchanger has multiple boundaries for cold and hot inlets and outlets, and the overall information is used Description, at this time the core boundary inside

[0018] The parameterized expression is mainly expressed by The various parameters in are regulated and applied to the offset parameter C to obtain the expression Usage Generate hot fluid Ω1 and cold fluid Ω2 respectively, and use the overall space Ω to perform Boolean subtraction operation with Ω1 and Ω2 to obtain the final TPMS heat exchanger core.

[0019] When used, f is determined by the cold / hot fluid boundary position information i (x); β is determined by the relative volume information inside and outside the boundary, combined with the relationship between ε and the offset parameter C i ; Select the surface offset range deltaX size according to the TPMS heat exchanger core size, and then obtain k i , determine the parameter β i 、k i 、f i (x) After selecting the value scheme, determine The expression is used to complete the parametric characterization of the model, realize the continuous change of the relative volume at each boundary, and achieve the purpose of drag reduction.

[0020] The design method specifically includes the following steps:

[0021] The first step is to determine the overall structure size of the core, the flow form of cold and hot fluids, and the inlet and outlet information, and realize the boundary parameterization to obtain the local S i (x) f i Item (x).

[0022] 1.1) According to the working space limitation, determine the basic shape of the core, the location and method of the cold and hot fluid inlet and outlet. This article takes the cylindrical heat exchanger core as an example to describe the overall process. The dimensions of the cylindrical core include inner diameter d, outer diameter D, and height H; the hot fluid inlet is the outer cylindrical surface of the core, with the center at (x1, y1) and the radius r1 = D / 2; the hot fluid outlet is the inner cylindrical surface of the core, with the center at (x2, y2) and the radius r2 = d / 2; the cold fluid inlet is a circular tube, with the center at (x 3, The outlet of the cold fluid is two circular tubes with centers at (x4, y4) and (x5, y5) and radii r4 and r5 respectively.

[0023] 1.2) Parametrically express the inlet and outlet boundaries. In this case, the boundaries have two-dimensional features represented by f i (x,)

[0024] The boundary expression of the hot fluid inlet is:

[0025] The boundary expression of the hot fluid outlet is:

[0026] The boundary expression of the cold fluid inlet is:

[0027] The boundary expression of the cold fluid outlet is:

[0028] Among them, (x, y) represents the coordinates of any point; (x1, y1) is the center position of the hot fluid inlet, and the radius is r1=D / 2; (x2, y2) is the center position of the hot fluid outlet, and the radius is r2=d / 2; (x3, y3) represents the center position of the cold fluid inlet, and the radius is r3; (x4, y4) and (x5, y5) represent the center positions of the cold fluid outlet, and the radii are r4 and r5; D represents the outer diameter; d represents the inner diameter; when the coordinates (x, y) of any point simultaneously satisfy: f1(x, y)<0, f2(x, y)>0, f3(x, y)>0, f4(x, y)>0, f5(x, y)>0, it indicates that the point is located inside the core.

[0029] The second step is to determine the core TPMS structure type, determine the relative volume space distribution, and then determine the core inlet and outlet S i (x) β i 、k i When the TPMS structure is different, the relationship between the relative volume and the offset parameter C is different, and the Sigmoid function parameter values are different;

[0030] 2.1) Determine the core TPMS structure type. This article uses a Gyroid surface as an example. Obtain the relative spatial distribution of the cold and hot fluid volumes. As previously stated, the hot fluid domain is defined as Ω1: G(x,y,z) < S(x), with a relative volume of ε1. The cold fluid domain is defined as Ω2: G(x,y,z) > S(x), with a relative volume of ε2. For the hot fluid domain, ε1 = 100% locally outside the core hot fluid inlet (i.e., when f1(x,y) > 0), the local ε1 value within the core is 50%, and the local ε1 = 100% outside the core hot fluid outlet. The local ε2 = 100% outside the core inlet, ε2 = 1-ε1 = 50% within the core, and ε2 = 100% locally outside the core outlet.

[0031] 2.2) According to the relative volume spatial distribution of cold and hot fluids, obtain the spatial distribution of parameter C, that is, S i (x) Spatial distribution.

[0032] Due to the different types of TPMS structures, the offset parameter C used to ensure the continuity of the fluid domain is different. This paper takes the Gyroid surface thermal fluid inlet function S1(x) as an example. It is known that the local ε1 = 100% outside the core thermal fluid inlet. According to the relationship between the relative volume domain offset parameter C mentioned above, when C ≥ 1.5, ε1 = 100%, that is, when f1(x, y) > 0 outside the thermal fluid core inlet, S1(x) ≥ 1.5, and the boundary is equal; when f1(x, y) < 0 inside the core, S1(x) = 0;

[0033] 2.3) By S i (x) spatial distribution, obtain S i (x) The range or value of each parameter.

[0034] Continuing with the example of the hot fluid inlet function S1(x), the distribution of S1(x) is known in 2.3: when f1(x,y)>0, S1(x)≥1.5, and the boundary is equal, that is, x=x j When f1(x j )=0, When f1(x,y)<0, S1(x=0; and S i (x) decreases as f1(x,y) decreases, and k1 < 0. In summary, we can conclude that: k1 < 0, β1 ≥ 3, and the value only affects the speed of change of the S1(x) value, that is, the speed of change of the relative volume, which can be determined by the size of the heat exchanger core. When the core is relatively large, |k| can be smaller, the relative volume changes more slowly, and the change area is larger.

[0035] 2.4) Repeat steps 2.2) and 2.3) to obtain the hot fluid outlet local offset function S2(x), the cold fluid inlet local offset function S3(x), and the cold fluid outlet local offset functions S4(x) and S5(x).

[0036] The third step is to obtain the overall expression and construct the cold and hot fluid and core models;

[0037] 3.1) Due to S i (x) contains only a single import and export boundary information, and the core boundary S i (x)≠0, maintain S within the core boundary i (x) = 0, each S i (x) can be added to describe the overall heat exchanger Right now

[0038] 3.2) At this point, excluding the region of relative volume change near the inlet and outlet boundaries, S(x) within the core is 0, meaning the relative volumes of the hot and cold fluids within the core are ε2 = ε1 = 50%, excluding the wall structure. The relative volumes of the fluid domains within the core can be adjusted during heat exchanger design. This can be done by adjusting the relationship between relative volume and offset parameters (for a Gyroid structure, the relationship between the relative volume on the G(x,y,z)<C side and parameter C is: ε = 0.4186 × C + 0.502). By determining the values of ε1 and ε2 within the core during design, the overall offset parameters C1 and C2 are determined.

[0039] 3.3) Adjust the relative volume of the core by adding the following equations to S(x): Hot fluid Ω1: G(x,y,z) < S(x) + C1; Cold fluid Ω2: G(x,y,z) > S(x) + C2. Modeling is performed using these expressions to obtain the hot and cold fluid domain models. Perform a Boolean subtraction operation on the overall space Ω, subtracting the hot and cold fluid domain models to obtain the final heat exchanger core model.

[0040] The beneficial effects of the present invention are:

[0041] (1) The present invention is based on a parameterized method to achieve TPMS surface offset with controllable local parameters.

[0042] (2) The present invention uses a parametric surface offset scheme to perform local adjustments to the TPMS heat exchanger module. By changing the cells at the inlet and outlet of the TPMS heat exchanger module, the relative volume of a single fluid can be continuously changed, and the sudden change in the flow area at the inlet and outlet of the cold and hot fluids in the TPMS heat exchanger module can be reduced, thereby effectively reducing local energy losses. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 Are different TPMS models Schematic diagram of the change of relative volume of some parts with constant C;

[0044] Figure 2 Schematic diagram of a TPMS heat exchanger core that directly closes a single flow channel;

[0045] Figure 3 It is the Sigmoid function and the cross-sectional diagram of the fluid domain used in TPMS. Figure 3 (a) in the function Schematic diagram; Figure 3 (b) in Cross-section of the fluid domain;

[0046] Figure 4 This is a schematic diagram of the cold and hot fluid domains and the core model in Example 1. Figure 4 (a) is a schematic diagram of the cold fluid domain. Figure 4 (b) is a schematic diagram of the thermal fluid domain. Figure 4(c) is a schematic diagram of the heat exchanger core module; DETAILED DESCRIPTION

[0047] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0048] Example 1

[0049] The heat exchanger core is constructed by the above method. Figure 4 shown

[0050] The first step is to determine the overall structural size of the core, the flow form of cold and hot fluids, and the inlet and outlet information, and realize the boundary parameterization to obtain the local S i (x) f i Item (x).

[0051] 1.1) Inner diameter d = 60 mm, outer diameter D = 180 mm, height H = 100 mm; the hot fluid inlet is the outer cylindrical surface of the core, with the center at (0, 0) and the radius r1 = D / 2; the hot fluid outlet is the inner cylindrical surface of the core, with the center at (0, 0) and the radius r2 = d / 2; the cold fluid inlet is a circular tube with the center at (35, 0) and the radius r3 = 6 mm; the cold fluid outlet is two circular tubes with the centers at (-75, 30) and (-75, -30) respectively, and the radii r4 = r5 = 7 mm.

[0052] 1.2) Parametric expression of inlet and outlet boundaries

[0053] The boundary expression of the hot fluid inlet is:

[0054] The boundary expression of the hot fluid outlet is:

[0055] The boundary expression of the cold fluid inlet is:

[0056] The boundary expression of the cold fluid outlet is:

[0057] The second step is to determine the core TPMS structure type, determine the relative volume space distribution, and then determine the core inlet and outlet S i (x) β i 、k i 、.

[0058] 2.1) Determine the core TPMS structure type. This article uses a Gyroid surface as an example. Obtain the relative spatial distribution of the cold and hot fluid volumes. As previously stated, the hot fluid domain is defined as Ω1: G(x,y,z) < S(x), with a relative volume of ε1. The cold fluid domain is defined as Ω2: G(x,y,z) > S(x), with a relative volume of ε2. For the hot fluid domain, ε1 = 100% outside the core's hot fluid inlet. That is, when f1(x,y) > 0, the ε1 value inside the core is determined during design. ε1 = 100% outside the core's hot fluid outlet. ε2 = 100% outside the core's inlet, ε2 = 1-ε1 inside the core, and ε2 = 100% outside the core's outlet.

[0059] 2.2) According to the relative volume spatial distribution of cold and hot fluids, obtain the spatial distribution of parameter C, that is, S i (x) Spatial distribution.

[0060] Due to the different types of TPMS structures, the offset parameter C used to ensure the continuity of the fluid domain is different. This paper takes the Gyroid surface thermal fluid inlet function S1(x) as an example. It is known that ε1 = 100% outside the core thermal fluid inlet. According to the relationship between the relative volume domain offset parameter C mentioned above, when C ≥ 1.5, ε1 = 100%, that is, when f1(x, y) > 0 outside the thermal fluid core inlet, S1(x) ≥ 1.5, and the boundary is equal; when f1(x, y) < 0 inside the core, S1(x) = 0;

[0061] 2.3) By S i (x) spatial distribution, obtain S i (x) The range or value of each parameter.

[0062] Continuing with the example of the hot fluid inlet function S1(x), the distribution of S1(x) is known in 2.3: when f1(x,y)>0, S1(x)≥1.5, and the boundary is equal, that is, x=x j When f1(x j )=0, When f1(x,y)<0, S1(x=0; and S i (x) decreases as f1(x,y) decreases, and k1 < 0. In summary, we can conclude that: k1 < 0, β1 ≥ 3, and the value only affects the speed of change of S1(x), that is, the speed of change of the relative volume, which can be determined according to the size of the heat exchanger core. Here, k1 = -2, β1 = 3.

[0063] 2.4) Repeat steps 2.2) and 2.3) to obtain the parameter range of the hot fluid outlet local offset function S2(x), k2>0, β2≥3, and take k2=2, β2=3; the parameter range of the cold fluid inlet local offset function S3(x), k3<0, β2≤-3, and parameters k3=-2, β2=-3; the parameter range of the cold fluid outlet local offset function S4(x) and S5(x), k4<0, k5<0, β4≤-3, β5≤-3, and take k4, k5=-2, β4, β5=-3.

[0064] The third step is to obtain the overall expression and construct the cold and hot fluid and core models;

[0065] 3.1) Obtain the overall expression

[0066] 3.2) At this time, excluding the relative volume change area near the inlet and outlet boundaries, the relative volume of the internal hot and cold fluids is taken as ε2 = ε1 = 40%. The relationship between the relative volume and the offset parameter (Gyroid structure, the relationship between the relative volume of the G(x, y, z) < C side and the parameter C is: ε = 0.4186 × C + 0.502) can be calculated to obtain C1 = -0.24 and C2 = 0.24.

[0067] 3.3) Adjust the relative volume of the core for S(x): Hot fluid Ω1: G(x,y,z) < S(x) - 0.24; Cold fluid Ω2: G(x,y,z) > S(x) + 0.24. Modeling is performed using these expressions to obtain the hot and cold fluid domain models. A Boolean subtraction operation is performed on the overall space Ω to subtract the hot and cold fluid domain models to obtain the final heat exchanger core model. The relative volume of the heat exchanger core wall is 20%.

[0068] The solid model of the thermal fluid domain is constructed using the above expressions and numerical simulation is performed.

[0069] The effect of this example is verified: In Example 1, numerical simulation calculations were performed on the thermal fluid domain using the drag reduction design and the conventional design thermal fluid domain. Under the conditions of using water as the working fluid and the same mass flow inlet boundary conditions, the calculation results showed that the flow pressure drop after applying the inlet and outlet offsets was reduced by 40% compared with the conventional inlet and outlet pressure drop.

[0070] The above-described embodiments merely express the implementation methods of the present invention, but should not be understood as limiting the scope of the patent of the present invention. It should be pointed out that for those skilled in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention.

Claims

1. A design method for a TPMS heat exchanger core that achieves local drag reduction design, characterized in that: The proposed design method uses a parametric approach to achieve the design of a 3D-printed modular TPMS heat exchanger core with localized drag reduction. Specifically, based on the traditional Gyroid structural expression, the offset parameter C in the Gyroid structural expression is parametrically expressed using a Sigmoid function to achieve continuous variation in the relative volume of the core inlet and outlet regions, thereby achieving drag reduction at the core inlet and outlet regions.

2. The design method of a TPMS heat exchanger core for realizing local drag reduction design according to claim 1, characterized in that: The design method specifically includes the following steps: The first step is to determine the overall structure size of the core, the flow form of cold and hot fluids, and the inlet and outlet information, and realize the boundary parameterization to obtain the local S i (x) f i Item (x); 1.1) According to the working space limitation, determine the basic shape of the core, the location and method of the cold and hot fluid inlet and outlet; take the cylindrical heat exchanger core as an example to describe the overall process. The dimensions of the cylindrical core include inner diameter d, outer diameter D, and height H; the hot fluid inlet is the outer cylindrical surface of the core, with the center at (x1, y1) and the radius r1 = D / 2; the hot fluid outlet is the inner cylindrical surface of the core, with the center at (x2, y2) and the radius r2 = d / 2; the cold fluid inlet is a circular tube, with the center at (x 3, y3) and radius r3; the cold fluid outlet is two circular tubes with centers at (x4, y4) and (x5, y5) and radii r4 and r5 respectively; 1.2) Parametrically express the inlet and outlet boundaries. In this case, the boundaries have two-dimensional features represented by f i (x,) The boundary expression of the hot fluid inlet is: The boundary expression of the hot fluid outlet is: The boundary expression of the cold fluid inlet is: The boundary expression of the cold fluid outlet is: Wherein, (x, y) represents the coordinates of any point; (x1, y1) is the center position of the hot fluid inlet, with a radius of r1=D / 2; (x2, y2) is the center position of the hot fluid outlet, with a radius of r2=d / 2; (x3, y3) represents the center position of the cold fluid inlet, with a radius of r3; (x4, y4) and (x5, y5) represent the center positions of the cold fluid outlet, with radii of r4 and r5; D represents the outer diameter; d represents the inner diameter; when the coordinates of any point (x, y) simultaneously satisfy: f1(x, y) < 0, f2(x, y) > 0, f3(x, y) > 0, f4(x, y) > 0, f5(x, y) > 0, it indicates that the point is located inside the core; The second step is to determine the core TPMS structure type, determine the relative volume space distribution, and then determine the core inlet and outlet S i (x) β i 、k i ; When the TPMS structure type is different, the relationship between the relative volume and the offset parameter C is different, and the Sigmoid function parameter value is different; 2.1) Determine the core TPMS structure type and illustrate it with a Gyroid surface; obtain the relative volume spatial distribution of the cold and hot fluids, set the hot fluid domain to Ω1: G(x,y,z)<S(x), and the relative volume to ε1; set the cold fluid domain to Ω2: G(x,y,z)>S(x), and the relative volume to ε2; for the hot fluid domain, the local ε1 outside the core hot fluid inlet is 100%, that is, when f1(x,y)>0, the local ε1 value inside the core is 50%, and the local ε1 outside the core hot fluid outlet is 100%; the local ε2 outside the core inlet is 100%, the ε2 inside the core is 1-ε1=50%, and the local ε2 outside the core outlet is 100%; 2.2) According to the relative volume spatial distribution of cold and hot fluids, obtain the spatial distribution of parameter C, that is, S i (x) spatial distribution; Due to the different types of TPMS structures, the offset parameter C used to ensure the continuity of the fluid domain is different; using the Gyroid surface thermal fluid inlet function S1(x) to illustrate, it is known that the local ε1=100% outside the core thermal fluid inlet, from the relationship between the relative volume domain offset parameter C, it can be seen that when C≥1.5, ε1=100%, that is, when f1(x,y)>0 outside the thermal fluid core inlet, S1(x)≥1.5, and the same value is taken at the boundary; when f1(x,y)<0 inside the core, S1(x)=0; 2.3) By S i (x) spatial distribution, obtain S i (x) The range or value of each parameter; Continuing with the explanation of the hot fluid inlet function S1(x), it is known that the distribution of S1(x) is: when f1(x,y)>0, S1(x)≥1.5, and the boundary is equal, that is, x=x j When f1(x j )=0, When f1(x,y)<0, S1(x=0; and S i (x) decreases as f1(x,y) decreases, k1<0; in summary, we can conclude that: k1<0, β1≥3, the value size only affects the speed of change of S1(x), that is, the speed of change of relative volume, which is determined by the size of the heat exchanger core; 2.4) Repeat steps 2.2) and 2.3) to obtain the hot fluid outlet local offset function S2(x), the cold fluid inlet local offset function S3(x), and the cold fluid outlet local offset functions S4(x) and S5(x); The third step is to obtain the overall expression and construct the cold and hot fluid and core models; 3.1) Due to S i (x) contains only a single import and export boundary information, and the core boundary S i (x)≠0, maintain S within the core boundary i (x) = 0, each S i (x) can be added to describe the overall heat exchanger Right now 3.2) At this time, except for the area of relative volume change near the inlet and outlet boundaries, S(x) inside the core = 0, that is, the relative volume of the hot and cold fluids inside the core is ε2 = ε1 = 50%, and the wall structure is not included. In the heat exchanger design, the relative volume of the fluid domain inside the core is adjusted based on the relationship between the relative volume and the offset parameter. By determining the values of ε1 and ε2 in the core during design, the overall offset parameters C1 and C2 are determined. 3.3) Adjust the relative volume of the core by adding the following formula to S(x): hot fluid Ω1: G(x,y,z)<S(x)+C1; cold fluid Ω2: G(x,y,z)>S(x)+C2. Model the cold and hot fluid domain models using the above expressions. Perform a Boolean subtraction operation on the overall space Ω to subtract the cold and hot fluid domain models to obtain the final heat exchanger core model.

3. The design method of a TPMS heat exchanger core for realizing local drag reduction design according to claim 1, characterized in that: The Sigmoid function S i (x) is expressed as: Among them, β i Indicates S i (x) maximum value; S i (x) function value ranges from 0 to β i Change; k i Indicates S i (x) The speed of change of the function value, positive or negative, represents S i (x) Function monotonicity; f i (x) represents the core inlet and outlet boundaries, where the subscript i indicates the boundary i, and x represents the independent variable; the Sigmoid function S i (x) contains only local information, only at the boundary f i The function value at (x) varies from 0 to β i Change within the range, so that the outside of the boundary is β i , the boundary is 0, where the boundary represents the inside of the core; the TPMS heat exchanger has multiple boundaries of cold and hot inlets and outlets, and the overall information is used Description, at this time the core boundary inside The Sigmoid function is used to parameterize the offset parameter C in the Gyroid structure expression. In this case, C=S i (x) = 0, outside the boundary C = S i (x) = β i , Sigmoid function S i (x) makes the offset parameter C at the boundary change continuously. Based on the relationship between the relative volume ε and the offset parameter C, the relative volume at the boundary changes continuously, reducing the energy loss caused by the sudden change of the flow cross section at the inlet and outlet.

4. The design method of a TPMS heat exchanger core for realizing local drag reduction design according to claim 3, characterized in that: The parameterized expression is mainly expressed by The various parameters in are regulated and applied to the offset parameter C to obtain the expression Usage Generate hot fluid Ω1 and cold fluid Ω2 respectively, and use the overall space Ω to perform Boolean subtraction operation with Ω1 and Ω2 to obtain the final TPMS heat exchanger core.

5. The design method of a TPMS heat exchanger core for realizing local drag reduction design according to claim 4, characterized in that: When used, f is determined by the cold / hot fluid boundary position information i (x); β is determined by the relative volume information inside and outside the boundary, combined with the relationship between ε and the offset parameter C i ; Select the surface offset range deltaX size based on the TPMS heat exchanger core size, and then obtain k i , determine the parameter β i 、k i 、f i (x) After selecting the value scheme, determine The expression is used to complete the parametric characterization of the model, realize the continuous change of the relative volume at each boundary, and achieve the purpose of drag reduction.

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