Heat sink and method of designing heat sink

Abstract

A heat sink (1) is provided with a base body (10) and a plurality of fins (20) protruding from a surface (10a) of the base body (10). The plurality of fins (20) extend in a plate shape along a first direction (d1) parallel to the surface (10a) of the base body (10), and the fins are arranged at intervals in a second direction (d2) parallel to the surface (10a) of the base body (10) and perpendicular to the first direction (d1). Each of the plurality of fins (20) is provided with an opening (25) that penetrates the fin (20) in the thickness direction.

Description

Heat sink and method for designing the same

[0001] The present disclosure relates to heat sinks and methods for designing heat sinks.

[0002] Heat sinks are known as devices for dissipating heat from active heat sources such as motors, LED lights, and battery pack electronics. Patent Document 1 (US Pat. No. 5,499,299) discloses a heat sink with multiple fins. In this heat sink, the fins are spaced apart more sparsely near the center of the heat sink and more densely spaced in the outer regions.

[0003] Japanese Patent Application Publication No. 9-64568

[0004] However, with the heat sink disclosed in Patent Document 1, it is difficult to improve the amount of heat dissipation by convection.

[0005] The present disclosure provides a heat sink and the like that can improve the amount of heat dissipation by convection.

[0006] A heat sink according to one aspect of the present disclosure includes a base and a plurality of fins protruding from a surface of the base, the fins extending in a plate-like shape along a first direction parallel to the surface of the base and arranged at intervals along a second direction parallel to the surface of the base and perpendicular to the first direction, and each of the fins has an opening penetrating the fin in a thickness direction. A specific example of the above aspect is described in Embodiment 1 and Example 1 of this specification.

[0007] A heat sink design method according to one aspect of the present disclosure includes a substrate and a plurality of fins extending in a planar shape along a first direction parallel to a surface of the substrate and spaced apart along a second direction parallel to the surface of the substrate and perpendicular to the first direction, the method including the steps of: using a computer to design the central portions of each of the plurality of fins in the first direction;

[0008] According to the heat sink and the like of the present disclosure, the amount of heat dissipation by convection can be improved.

[0009] FIG. 1 is a diagram illustrating an example of a heat sink according to the first embodiment. FIG. 2 is a diagram illustrating variations of the heat sink according to the first embodiment. FIG. 3 is a diagram illustrating the performance of the heat sink according to the first embodiment. FIG. 4 is a diagram illustrating velocity distributions obtained from a CFD simulation of the heat sink according to the first embodiment. FIG. 5 is a diagram illustrating modeling of three-dimensional topology optimization. FIG. 6A is a diagram illustrating the number of fins of a heat sink. FIG. 6B is a diagram illustrating the relationship between the number of fins and the performance of the heat sink. FIG. 7 is a diagram illustrating the number of fins, heat sink parameters, thermal resistance, etc. FIG. 8 is a diagram illustrating multiple heat sinks generated by applying subtractive topology optimization to a design domain and the performance of the multiple heat sinks. FIG. 9 is a diagram illustrating the performance of a hybrid heat sink. FIG. 10 is a diagram illustrating velocity distributions obtained from a CFD simulation of a hybrid heat sink with design domain lengths of (a) 10 mm, (b) 20 mm, (c) 30 mm, (d) 40 mm, (e) 50 mm, and (f) 60 mm. Figure 11 shows the thermal performance of a conventional plate-fin heat sink and a hybrid heat sink with design area lengths of 10 mm, 20 mm, 30 mm, 40 mm, 50 mm, and 60 mm. Figure 12 shows the thermal performance of a conventional plate-fin heat sink and a hybrid heat sink with design area lengths of 10 mm, 20 mm, 30 mm, 40 mm, 50 mm, and 60 mm when radiation is considered. Figure 13 shows the solid volume fraction of an 11-fin PFACHS and a hybrid heat sink with design area lengths of 10 mm, 20 mm, 30 mm, 40 mm, 50 mm, and 60 mm. Figure 14 shows a three-dimensional view of three heat sinks fabricated by selective laser melting.Figure 15(a) shows the change in heat transfer coefficient with temperature difference for an 11-fin PFACHS with a 10 mm design area and a hybrid heat sink. Figure 15(b) shows the change in thermal resistance with respect to heat quantity for an 11-fin PFACHS with a 10 mm design area and a hybrid heat sink. Figure 15(c) shows the change in heat transfer coefficient with temperature difference for an 11-fin PFACHS and a hybrid heat sink with a 20 mm design area. Figure 15(d) shows the change in thermal resistance with respect to heat quantity for an 11-fin PFACHS with a 20 mm design area and a hybrid heat sink. Figure 16 shows the thermal resistance of three types of PFACHS experimentally determined at ambient temperatures ranging from 27.7°C to 29.6°C. Figure 17 shows the effect of design parameters on thermal resistance. Figure 18 shows a comparative heat sink. Figure 19 shows the heat transfer coefficient, etc., of a comparative heat sink. FIG. 20 is a diagram showing the heat transfer coefficients of various heat sinks. FIG. 21 is a diagram showing an example of a heat sink according to the second embodiment. FIG. 22 is a schematic diagram of a design domain when performing partitioned design. FIG. 23 is a diagram showing an example of a partitioned domain. FIG. 24 is a diagram showing another example of a partitioned domain. FIG. 25 is a diagram showing a specific example of a heat sink according to the second embodiment. FIG. 26 is a diagram showing the number of partitions in the design domain of a heat sink and the heat transfer coefficient. FIG. 27 is a diagram showing the structure, temperature field, and velocity field of a heat sink. FIG. 28 is a diagram showing the design domain size, volume, solid volume fraction, surface area, surface area-to-volume ratio, and heat transfer coefficient of a 1 / 16 design and a 1 / 16-R design heat sink. FIG. 29 is a diagram showing a conventional plate-fin heat sink. FIG. 30 is a diagram showing the overall heat flow rate in relation to emissivity. FIG. 31 is a temperature profile on the top surface of the fin. FIG. 32 is a diagram showing the velocity vector field in the plane z = 7 mm. FIG. 33 is a diagram showing temperature contours in the plane z = 7 mm. Figure 34 shows a cross-fin heat sink with different fin densities, Figure 35 shows a schematic of boundary conditions used in topology optimization, and Figure 36 shows a design space partitioning scheme.FIG. 37(a) shows the TO shape generated by COMSOL Multiphysics software, and FIG. 37(b) shows the exported ".STL" file. FIG. 38 shows the heat sink shape post-processed by SpaceClaim software. FIG. 39 shows a rendered CAD image of the heat sink. FIG. 40 shows a TO-designed heat sink and a hybrid heat sink. FIG. 41 shows a cross-sectional side view of the TF16 and CF0-TF16 heat sinks. FIG. 42 shows various heat sinks fabricated in this embodiment. FIG. 43 shows the thermal resistance and weight of various heat sinks.

[0010] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that each of the embodiments described below represents a specific example of the present disclosure. Therefore, the numerical values, shapes, materials, components, arrangement positions and connection forms of the components, etc. shown in the following embodiments are merely examples and are not intended to limit the present disclosure. Therefore, among the components in the following embodiments, components not recited in independent claims will be described as optional components.

[0011] Note that each figure is a schematic diagram and is not necessarily an exact illustration. Therefore, the scales and the like do not necessarily match in each figure. Furthermore, in each figure, substantially the same configuration is assigned the same reference numeral, and duplicate explanations are omitted or simplified. Furthermore, in this specification, the terms "up" and "down" do not necessarily refer to the upward direction (vertically upward) and downward direction (vertically downward) in absolute spatial recognition.

[0012] First Embodiment The configuration of a heat sink 1 according to a first embodiment will be described with reference to FIGS.

[0013] Fig. 1 is a diagram illustrating an example of a heat sink according to embodiment 1. Fig. 2 is a diagram illustrating a variation of the heat sink according to embodiment 1. In Fig. 1 and Fig. 2, the heat sink is shown in perspective.

[0014] The heat sink 1 is a heat dissipation member that dissipates heat generated in a heat source. The heat sink 1 functions as a heat exchanger, cooling the heat source by dissipating the heat generated in the heat source to the outside. In other words, the heat sink 1 functions as a cooler that cools the heat source. The heat sink 1 is made of a metal material with high thermal conductivity, such as aluminum, an aluminum alloy, or copper.

[0015] As shown in FIGS. 1 and 2, the heat sink 1 includes a base 10 and a plurality of fins 20 provided on the base 10 .

[0016] The base 10 is, for example, a rectangular parallelepiped substrate. The base 10 has a front surface 10a and a back surface 10b opposite to the front surface 10a. The front surface 10a and the back surface 10b are flat and parallel to each other.

[0017] In this embodiment, a predetermined direction parallel to the surface 10a of the base 10 is called the first direction d1, a direction parallel to the surface 10a of the base 10 and perpendicular to the first direction d1 is called the second direction d2, and a direction perpendicular to the surface 10a of the base 10 is called the third direction d3.

[0018] The multiple fins 20 protrude in the third direction d3 from the surface 10a of the base 10. Each fin 20 is a straight fin that extends linearly from the surface 10a of the base 10 in the third direction d3. Each fin 20 has a flat plate-like outer shape and both side surfaces (both surfaces) perpendicular to the surface 10a of the base 10. Assuming that each fin 20 has a flat plate shape (or that there are no openings 25, which will be described later), the multiple fins 20 have the same length in the first direction d1, the same protruding length (height) in the third direction d3, and the same length (thickness) in the second direction d2.

[0019] The fins 20 extend in a plate shape along the first direction d1 and are arranged at intervals in the second direction d2. The fins 20 are arranged parallel to one another and are arranged at equal intervals along the second direction d2. Air is present between two fins 20 adjacent to each other in the second direction d2.

[0020] In this example, the protruding length of the fins 20 in the third direction d3 is longer than the thickness dimension of the base 10 and shorter than the length of the fins 20 in the first direction d1. Furthermore, the thickness of the fins 20, which is the length of the fins 20 in the second direction d2, is thinner than the thickness of the base 10, and the distance between two adjacent fins 20 in the second direction d2 is shorter than the protruding length of the fins 20. Note that these long / short lengths and magnitude relationships are merely examples.

[0021] Each fin 20 has a central portion 21 including a central part in the first direction d1, and two end portions 22 located on either side of the central portion 21. In Fig. 2, the central portion 21 is indicated by hatched dots. The height of the central portion 21 and the height of the end portions 22 are the same as the height of the fin 20.

[0022] 2A shows an example in which the length of the central portion 21 is L / 6, in FIG. 2B shows an example in which the length of the central portion 21 is 2L / 6, in FIG. 2C shows an example in which the length of the central portion 21 is 3L / 6, in FIG. 2D shows an example in which the length of the central portion 21 is 4L / 6, in FIG. 2E shows an example in which the length of the central portion 21 is 5L / 6, and in FIG. 2F shows an example in which the length of the central portion 21 is L. For example, in the first direction d1, the length of the central portion 21 in which the opening 25 is provided is desirably 80% or less of the length of the fin 20.

[0023] 1 and 2 , each of the multiple fins 20 has an opening 25 penetrating the fin 20 in the thickness direction. The openings 25 are provided in all of the multiple fins 20, not just some of the multiple fins 20. The openings 25 are flow paths that connect the air in contact with both side surfaces (both surfaces) of the plate-like fin 20 in the second direction d2. When heat is dissipated by utilizing air convection, some of the air between two adjacent fins 20 flows through the openings 25.

[0024] Each opening 25 is provided in the central portion 21 of each fin 20. One or more openings 25 may be provided in the central portion 21. The openings 25 are at least one of a notched hole and a through hole.

[0025] Each opening 25 is formed symmetrically when viewed from the second direction d2. More specifically, each fin 20 including each opening 25 is plane-symmetric with respect to a plane that passes through the center of the base 10 and is perpendicular to the axis extending in the first direction d1. Furthermore, each opening 25 is formed symmetrically with respect to the first direction d1. More specifically, the multiple fins 20 are plane-symmetric with respect to a plane that passes through the center of the base 10 and is perpendicular to the axis extending in the second direction d2.

[0026] Furthermore, the opening 25 of the outermost fin 20 located furthest outward in the second direction d2 is a rectangular cutout hole. The opening 25 of the outermost fin 20 coincides with the area of ​​the central portion 21 and is formed so as to cut out the entire area of ​​the central portion 21 of the outermost fin 20. In other words, the area of ​​the central portion 21 in this embodiment is defined by the area of ​​the opening 25 of the outermost fin 20.

[0027] The openings 25 of the inner fins 20, which are located more inward than the outermost fins 20 in the second direction d2, have a curved shape. The openings 25 of two fins 20 adjacent to each other in the second direction d2 are different in shape and position. In other words, the openings 25 of two adjacent fins 20 are not perfectly aligned when viewed from the second direction d2. Therefore, the air between two adjacent fins 20 does not pass through the openings 25 in a straight line in the second direction d2, but at least a portion of the air comes into contact with the side surface of the fin 20 before passing through the openings 25.

[0028] For example, the openings 25 of the inner fins 20 may be formed so that the opening area is smaller than the openings 25 of the outermost fins 20. Specifically, in the second direction d2, the opening ratio (= area of ​​openings 25 / area of ​​central portion 21) may decrease from the outside to the center of the base 10, and the opening ratio may increase from the center to the outside of the base 10. Note that when multiple openings 25 are provided in the central portion 21, the area of ​​the openings 25 is the total area of ​​the multiple openings 25.

[0029] Fig. 3 is a diagram showing the performance of the heat sink according to embodiment 1. Fig. 4 is a diagram showing velocity distributions obtained from a CFD simulation of the heat sink according to embodiment 1. Figs. 3 and 4 show examples in which the lengths of the central portion 21 are (a) L / 6, (b) 2L / 6, (c) 3L / 6, (d) 4L / 6, (e) 5L / 6, and (f) L, respectively.

[0030] FIG. 3 shows the volume V (mm ) of the heat sink 1 when the length of the central portion 21 is changed. ３ ), solid volume fraction Φ (%), surface area A of the heat sink 1 (mm ２ ), surface area to volume ratio A / V (m －１ ), and thermal resistance R (K / W).

[0031] Figure 4 shows the air flow velocity distribution on the front surface 10a of the heat sink 1 when heat is uniformly applied to the rear surface 10b of the heat sink 1. In Figure 4, faster flow velocities are shown in black, and slower flow velocities are shown in white, indicating that faster flow velocities promote convection.

[0032] For example, in the first direction d1, the length of the central portion 21 where the openings 25 are provided is desirably 5 / 6 times or less the length of the fin 20. More desirably, the length of the central portion 21 where the openings 25 are provided is 1 / 6 times or more and 4 / 6 times or less the length of the fin 20.

[0033] The fins 20 having the openings 25 are designed, for example, by performing topology optimization using a computer. In this embodiment, when designing the central portions 21 of the plurality of fins 20 using a computer, topology optimization is performed using the constraint of arranging a heat source on the back surface 10b of the base body 10, which is the substrate, and the objective function is to improve the amount of heat dissipation by convection in the heat sink 1. The shape of the plurality of fins 20 is determined to be a shape including the central portions 21 obtained by the topology optimization.

[0034] For example, the fin 20 having the openings 25 is manufactured by additive manufacturing (AM). The AM method is a manufacturing method in which materials are stacked to form a product. The design method and manufacturing method of the fin 20 will be described in detail in Example 1 below.

[0035] (Configuration and Effects of Heat Sink According to First Embodiment) The configuration and effects of the heat sink 1 according to the first embodiment will be illustrated.

[0036] The heat sink 1 of Example 1 includes a base 10 and a plurality of fins 20 protruding from a surface 10a of the base 10. The plurality of fins 20 extend in a plate shape along a first direction d1 parallel to the surface 10a of the base 10, and are arranged at intervals in a second direction d2 parallel to the surface 10a of the base 10 and perpendicular to the first direction d1. Each of the plurality of fins 20 is provided with an opening 25 penetrating the fin 20 in its thickness direction.

[0037] In this way, by providing the openings 25 in each of the multiple fins 20, air between two adjacent fins 20 can easily flow through the openings 25. Therefore, the air between the two fins 20 can easily flow not only in the first direction d1 but also in the second direction d2. This can improve the amount of heat dissipation by convection.

[0038] The heat sink 1 of Example 2 is the heat sink described in Example 1, and the openings 25 provided in each of the multiple fins 20 may be provided in the central portion 21 of the fin 20 in the first direction d1.

[0039] In this way, by providing the openings 25 in the central portion 21, the air located in the central portion 21 can easily flow through the openings 25. This makes it possible to improve the amount of heat dissipation by convection throughout the entire heat sink 1, including the central portion 21.

[0040] The heat sink 1 of Example 3 is the heat sink described in Example 2, and the length of the central portion 21 in the first direction d1 may be 80% or less of the length of the fins 20.

[0041] This allows air near an area of ​​80% or less of the length of the fin 20 to easily flow through the openings 25. This improves the amount of heat dissipation by convection.

[0042] The heat sink 1 of Example 4 is the heat sink according to any one of Examples 1 to 3, and the shapes of the openings 25 provided in each of two fins 20 adjacent to each other in the second direction d2 may be different.

[0043] As described above, the different shapes of the openings 25 cause at least a portion of the air between two adjacent fins 20 to come into contact with the side surfaces of the fins 20 before passing through the openings 25. This improves the amount of heat dissipation by convection.

[0044] The heat sink 1 of Example 5 is a heat sink described in any of Examples 1 to 4, and the openings 25 provided in each of two fins 20 adjacent to each other in the second direction d2 may be formed so as not to be perfectly aligned when viewed from the second direction d2.

[0045] As described above, the openings 25 are formed so as not to completely coincide when viewed from the second direction d2, so that at least a portion of the air between two adjacent fins 20 comes into contact with the side surface of the fin 20 before passing through the openings 25. This improves the amount of heat dissipation by convection.

[0046] The heat sink 1 of Example 6 is the heat sink according to any one of Examples 1 to 5, and the opening 25 may be at least one of a notched hole and a through hole.

[0047] This allows air between two adjacent fins 20 to easily flow through the notched holes or through-holes, thereby improving the amount of heat dissipation by convection.

[0048] The heat sink 1 of Example 7 is the heat sink according to any one of Examples 1 to 6, and the opening 25 may have a curved shape when viewed from the second direction d2.

[0049] This allows air between two adjacent fins 20 to easily flow through the curved openings 25. This improves the amount of heat dissipation by convection.

[0050] The heat sink 1 of Example 8 is a heat sink described in any of Examples 1 to 7, in which the base 10 is a rectangular parallelepiped substrate, and the multiple fins 20 may be plane-symmetric with respect to a plane that passes through the center of the base 10 and is perpendicular to an axis extending in the first direction d1.

[0051] As a result, the shape and arrangement of the fins 20 are bilaterally symmetrical when viewed from the second direction d2. This heat sink 1 can dissipate heat uniformly from the surface 10a of the substrate.

[0052] The heat sink 1 of Example 9 is a heat sink described in any of Examples 1 to 7, in which the base 10 is a rectangular parallelepiped substrate, and the multiple fins 20 may be plane-symmetric with respect to a plane that passes through the center of the base 10 and is perpendicular to an axis extending in the second direction d2.

[0053] As a result, the shape and arrangement of the fins 20 are symmetrical when viewed from the first direction d1. With this heat sink 1, heat can be dissipated uniformly from the surface 10a of the substrate.

[0054] The design method for the heat sink 1 of Example 10 is a design method for a heat sink that includes a substrate and a plurality of fins 20 that extend flat along a first direction d1 parallel to the surface of the substrate and are arranged at intervals in a second direction d2 that is parallel to the surface 10a of the substrate and perpendicular to the first direction d1, and when designing the central portions 21 of each of the plurality of fins 20 in the first direction d1 using a computer, topology optimization is performed with the constraint of placing a heat source on the back surface 10b of the substrate and with the objective function of improving the amount of heat dissipation by convection from the heat sink 1, and the shape including the central portions 21 obtained by the topology optimization is used as the shape of the plurality of fins 20.

[0055] By performing the above-described topology optimization, the shape of the central portion 21 can be appropriately designed. Therefore, for example, the shape of the fins 20 can be designed so that air between the two fins 20 can easily flow not only in the first direction d1 but also in the second direction d2. This makes it possible to provide a heat sink 1 that can improve the amount of heat dissipation by convection. Furthermore, by performing topology optimization, it is possible to suppress a decrease in the amount of heat dissipation by radiation even when the surface area of ​​the fins 20 is reduced, and to improve the amount of heat dissipation by convection.

[0056] Example 1 The design method and the like of the heat sink 1 shown in the first embodiment will be described in detail in Example 1.

[0057] Hereinafter, topology optimization may be referred to as "TO (Topology Optimization)," the air-cooled heat sink may be referred to as "ACHS," and the plate-fin air-cooled heat sink may be referred to as "PFACHS." The design domain shown below corresponds to the central portion 21.

[0058] 1. Topology Optimization of a Natural Convection-Cooled Heat Sink In this example, three-dimensional topology optimization modeling was performed to obtain a design for an air-cooled heat sink. The heat sink was assumed to be cooled by natural convection.

[0059] FIG. 5 is a diagram illustrating modeling of three-dimensional topology optimization.

[0060] Figure 5(a) shows an isometric view of the domain where 3D topology optimization is performed, and Figure 5(b) shows the imposed boundary conditions.

[0061] The air domain used in the simulation is shown in Figure 5(a). The design domain for 3D topology optimization is set up inside a large enclosure measuring 1 m in length, 1 m in width, and 0.6 m in height.

[0062] The boundary conditions are shown in FIG. 5(b), and Γ D,1 , Γ D,2 , Γ D,3 , Γ D,4 , Γ D,5, Γ N , Γ N,1 , and Γ N,2 The Dirichlet boundary is defined as D,1 , Γ D,2 , Γ D,3 , Γ D,4 , and Γ D,5 and the temperature is set to 20°C. The Neumann boundary is N , Γ N,1 and Γ N,2 corresponds to Γ N,1 and Γ N,2 is the thermal insulation boundary, and Γ N defines a constant heat rate.

[0063] To mathematically describe topology optimization based on natural convection between a solid and its surrounding fluid, the equation is written as follows: ｆ ∪Ω ｓ ) is formulated as follows:

[0064] The modeling of the fluid dynamics is carried out as follows:

[0065]

[0066] where ρ ｆ , u, μ ｆ , β are the density, velocity, dynamic viscosity, and thermal expansion coefficient of the fluid, respectively. ｆ is the temperature field, and T ０ is the reference temperature.

[0067] To model buoyancy-driven flows, the Boussinesq approximation was applied. F is the Brinkman friction term, which is employed in topology optimization of fluid flows to penalize flow through solid regions in the design domain. It represents the force acting on a fluid moving through an ideal porous medium. F is defined as follows:

[0068]

[0069] where γ is the design variable in the design domain, and α (overlined above alpha) is the maximum inverse permeability of the porous medium. ａis a parameter that determines the convexity of the interpolation. Heat conduction is modeled as follows:

[0070]

[0071] Here, c ｆ is the specific heat capacity of the fluid, k ｆ is the thermal conductivity of the fluid, I ｋ (γ) is a function that interpolates between the thermal conductivity of the fluid and the thermal conductivity of the material that makes up the heat sink.

[0072] I ｋ Rational Approximation Interpolation (RAMP) of material properties is used for (γ) and is given by the following equation (4):

[0073]

[0074] Here, k ｓ is the thermal conductivity of the solid, q ｆ is a parameter that determines the convexity of the interpolation.

[0075] The topology optimization problem is defined as follows:

[0076]

[0077] where Φ is the solid fraction and S(T) is the average temperature of the bottom surface of the heat sink. ａ Let q be 1. ｆ is set to 1. ａ and q ｆ The influence of is also discussed in Section 12. Discussion below. The optimization problems were solved using the commercially available COMSOL Multiphysics software on an HP Z440 workstation. Each design domain was employed with 100,000 elements in the "normal mesh" scheme.

[0078] 2. Thermal Performance Simulation of Heat Sink After the topology optimization of ACHS (air-cooled heat sink) was completed, the thermal performance of the topology ACHS and other PFACHS (plate-fin air-cooled heat sink) designs was numerically evaluated by computational fluid dynamics (CFD) simulation using COMSOL Multiphysics software (version 6.1).

[0079] A steady laminar flow model was employed to investigate the natural convection between the TO ACHS or PFACHS and the surrounding air. The fluid and solid materials in the model were air and AlSi10Mg, respectively.

[0080] [3. Mesh Independence Check] A mesh independence check was performed to select an appropriate number of mesh elements to be used in the simulation. Two types of heat sinks were used for the mesh independence check: a PFACHS consisting of 11 plate-shaped fins with a thickness of 1 mm and a base with a thickness of 3 mm, and a TOACHS fabricated using a conventional topology optimization method. The mesh check analysis did not consider heat dissipation by radiation. The simulation domain and boundary conditions were set to Γ to simulate the maximum allowable temperature. N The experiment is the same as in Section 1. Topology optimization of a natural convection-cooled heat sink, except that the temperature is changed to a constant temperature of 85°C. The change in the heat flux of the ACHS with the mesh element size is shown in Figure 5(c).

[0081] Figure 5(c) shows the effect of mesh on the thermal performance of TO ACHS and PFACHS. As shown in this figure, for TO ACHS, as the mesh size decreases, the heat flux of TO ACHS initially decreases and then becomes relatively constant as the mesh size is further reduced. The difference in heat flux between the fine and "finer" mesh settings was only 2%. A similar trend was observed for PFACHS. Because the difference between the two mesh settings was small, the "finer" mesh was adopted.

[0082] [4. Model Verification] To verify the accuracy of the CFD simulation, a numerical model based on the experimental conditions was constructed, and the simulation results were compared with the experimental results. The numerical simulation was performed under steady-state natural convection cooling for a PFACHS consisting of 11 fins, each 1 mm long, 60 mm wide, and 10 mm high.

[0083] The dimensions of the bottom surface of the PFACHS are 60 mm x 60 mm x 3 mm. A heat source was placed on the bottom surface of the heat sink. Five simulations were performed with thermal conductivities of 4 W, 6 W, 8 W, 10 W, and 12 W. Thermal radiation was also considered in the validation of this model. The emissivity was set to 0.6, which is close to the emissivity of the test specimen. The boundary conditions were the same as those described in Section 1. Topology optimization of natural convection-cooled heat sinks, except for Γ D,1 , Γ D,2 , Γ D,3 , Γ D,4 , and Γ D,5 is set to 27°C to match the experimental conditions where the room temperature was in the range of 26.7°C to 27.3°C.

[0084] A comparison between the simulation results and the experimental results is shown in Fig. 5(d), which shows the experimental results and the CFD (Computational Fluid Dynamics) simulation results.

[0085] It can be seen that the temperature difference between the experimental results and the simulation results is small over the entire range of the investigated heat rate. ｓｉｍ and T ｅｘｐ is the average base temperature (in degrees Celsius) of the simulation and experimental results. ｓｉｍ -T ｅｘｐ ) / T ｅｘｐ The relative errors calculated by the method between the experimental and simulation results for the five heat rates were only 5%, 6%, 7%, 6%, and 5%, respectively. The simulation results were in good agreement with the experimental results, verifying the rationality of both the numerical simulation and the experimental process.

[0086] 5. Sample Fabrication and Experimental Setup In this example, three heat sink samples were fabricated using AlSi10Mg material by selective laser melting (SLM).

[0087] In this fabrication process, AlSi10Mg powder with a diameter of 20 μm to 63 μm was uniformly distributed on the print bed. A 350 W laser beam with an 80 μm spot size was then scanned at a speed of 1150 mm / s with a hatch spacing of 0.1 mm to melt and fuse the powder into the designed topology before proceeding to the next layer. Three variations of the ACHS were fabricated using additive manufacturing (AM). Specifically, a hybrid heat sink with a 10 mm design area length, a 20 mm design area length, and an 11-fin PFACHS were fabricated. After fabrication, the thermal performance of each heat sink was experimentally evaluated.

[0088] An experimental setup was prepared to evaluate the thermal performance of the heat sink. Figures 5(e) and 5(f) show a schematic diagram and an image of the experimental setup. Figure 5(e) shows a schematic diagram of the experimental setup. Figure 5(f) shows an image of the experimental setup.

[0089] An acrylic enclosure measuring 140 cm x 140 cm x 85 cm was constructed to mimic the CFD simulation domain. This acrylic enclosure minimized external interference and maintained consistent conditions throughout the experiment. Furthermore, to mimic natural convection conditions, the large dimensions of the enclosure were chosen to minimize the effect of the enclosure walls on the fluid flow field near the heat sink. A direct current (DC) power supply (Gwinstek GPS-3030D) was used to test the heat sinks. To supply heat to the heat sinks, a 60 mm x 60 mm silicone rubber heater with a power rating of 4 W to 14 W was attached to the bottom of each heat sink and connected to the DC power supply. The heating rate could be directly controlled by varying the voltage and current of the power supply. The supplied voltage and current were obtained through the power supply's digital display panel, and the heat output of the heater was determined. The amount of heat generated is expressed as the amount of power (W) obtained by measuring the voltage and current while applying a voltage to the heater to pass a current. The heat rate in this specification is the amount of heat applied to the heat sink from its rear surface, and is expressed as the amount of heat generated, i.e., the amount of power.

[0090] The measured temperatures of the AM PFACHS and AM ACHS were obtained using a K-type thermocouple. For each heat sink, three thermocouples were inserted 30 mm into the heat sink base plate and 1.5 mm from the bottom of the heat sink. The average temperature was calculated from the recorded temperatures and used as the base temperature of the heat sink. The heat sink used was the PFACHS manufactured by AM and was not changed during the experiment. The comparative heat sink was the AM TO ACHS.

[0091] 6. Hybrid Heat Sink Design Methodology To overcome the limitations of traditional topology optimization strategies and create an ACHS with a high surface area-to-volume ratio while simultaneously optimizing material distribution to maximize solid thermal conduction and natural air convection, an additive-subtractive approach was developed in this example. First, a surface area additive approach was employed to create a fin structure with a smaller thickness by dividing the region, thereby increasing the surface area and achieving a high heat removal rate. A rational subtractive topology optimization approach was then applied to integrate the TO fin structure, reducing airflow resistance in the air-deficient zone and enhancing airflow distribution throughout the heat sink.

[0092] Fig. 6A is a diagram showing the number of fins on a heat sink, Fig. 6B is a diagram showing the relationship between the number of fins and the performance of the heat sink, and Fig. 7 is a diagram showing the number of fins and the parameters and thermal resistance of the heat sink.

[0093] Figure 6A (a) shows n subdomains set when performing the surface area summation method. First, we design heat sinks with five different n values ​​(n = 3, 7, 11, 15, and 19). Figure 6A (b) shows a schematic model in which fins with a thickness of 1 mm, height of 10 mm, and length of 60 mm are placed in each subdomain, corresponding to n values ​​of 3, 7, 11, and 15. Figure 6A (b) shows the region divided into 3, 7, 11, and 15 subdomains.

[0094] Figure 6B(c) shows the surface area to volume ratio A / V and thermal resistance R of the heat sink with different subdomains. Figure 6B(d) shows the air velocity distribution of the heat sink with 3 subdomains, Figure 6B(e) shows the air velocity distribution of the heat sink with 7 subdomains, Figure 6B(f) shows the air velocity distribution of the heat sink with 11 subdomains, Figure 6B(g) shows the air velocity distribution of the heat sink with 15 subdomains, and Figure 6B(h) shows the air velocity distribution of the heat sink with 19 subdomains.

[0095] To verify the effectiveness of the surface area addition method in increasing the surface area, the surface area to volume ratio A / V was calculated (see Fig. 6B(c) and Fig. 7). In this example, the value of n was increased from 3 to 7, 11, 15, and 19, and the surface area to volume ratio A / V was increased to 16.5 m. －１ , 27m －１ , 37.4m －１ , 47.8m －１ , and 58.2 m －１ To evaluate the performance of these ACHSs, CFD simulations were performed by imposing a constant temperature of 85°C on the bottom surface of the heat sink. As shown in Figure 6B(c), the thermal resistance of the ACHS decreased from its initial value with increasing n, and then increased with further increases in n. The initial decrease in thermal resistance R with increasing n indicates the benefit of increasing the interfacial area for heat transfer. However, as can be seen from the velocity distributions obtained from the CFD results in Figures 6B(d)–(h), increasing n also decreases the magnitude of the velocities on the heat sink, especially in the region near the center of the heat sink. This results in a decrease in the convective heat flux per unit fin area when n exceeds 11. As shown in Figure 6B, when n = 11, the thermal resistance is lowest, but the air velocity in the central region is less than 0.02 m / s, significantly lower than that in the boundary region (∼0.1 m / s).

[0096] FIG. 8 is a diagram showing a plurality of heat sinks generated by applying subtractive topology optimization to a design domain, and the performance of the plurality of heat sinks.

[0097] The design region shown in Figure 8 is from (a) 10 mm to (b) 60 mm of the fin length of 60 mm. The lengths of the design region are (c) 10 mm, (d) 20 mm, (e) 30 mm, (f) 40 mm, (g) 50 mm, and (h) 60 mm, respectively.

[0098] The above analysis shows that even with the optimal number of fins, conventional plate fins cannot take advantage of the convention mechanism. To overcome the drawbacks of conventional fin structures, topology optimization is applied to reduce the airflow resistance in the air depletion zone, as described in [1. Topology Optimization of Natural Convection Cooled Heat Sinks]. In this example, the fin structure is rationally reduced to improve the airflow distribution throughout the fin system.

[0099] 8(a) and 8(b) show schematic diagrams of design regions with lengths of 10 mm and 60 mm. As shown in FIGS. 8(a) and 8(b), n = 11 was used to further define the design region within the fin region. Since n = 11 is the best among conventional heat sinks, and the subtraction method in this example aims to further improve its thermal performance, the number of fins was set to 11. The length of the design region was varied from 10 mm to 60 mm in 10 mm intervals, and the height and thickness were constant at 10 mm and 1 mm, respectively.

[0100] Figures 8(c) to 8(h) show hybrid fin structures that combine a topology-optimized structure with the original plate fins. In these figures, the central region (center) represents the TO fin structure, and the area outside the central region represents the original plate fins. In this hybrid heat sink, a portion of the fins in the central region is rationally removed with the goal of maximizing heat dissipation through natural convection. This reduces airflow resistance compared to conventional plate fins and improves airflow distribution over the heat sink.

[0101] Figure 8(i) shows the surface area-to-volume ratio A / V and thermal resistance R of the hybrid heat sink. For TO-fins with design domain lengths of 10 mm, 20 mm, 30 mm, 40 mm, 50 mm, and 60 mm, the surface area-to-volume ratio A / V is 34.5 m, respectively. －１ , 32.8m －１ , 29.3m －１ , 27.4m －１ , 24m －１ , and 21.3 m －１ As shown in Figure 8(i), when the design region is lengthened, the surface area to volume ratio A / V decreases and the thermal resistance R increases. Conversely, when the design region is shortened, the surface area to volume ratio A / V increases and the thermal resistance decreases.

[0102] FIG. 9 is a diagram showing the performance of the hybrid heat sink.

[0103] The heat sink to which this iterative additive-subtractive topology optimization method was applied had a surface area-to-volume ratio (18.7 m) of the ACHS designed by conventional topology optimization. －１ The surface area-to-volume ratio (A / V) can be improved by 84% compared to the conventional topology optimization. For TO fins with design domain lengths of 10 mm, 20 mm, 30 mm, 40 mm, 50 mm, and 60 mm, the thermal resistances are 8.64 K / W, 8.69 K / W, 8.94 K / W, 9.53 K / W, 10.53 K / W, and 11.93 K / W, respectively. Therefore, the proposed iterative additive-subtractive topology optimization method can significantly reduce the thermal resistance by 23% compared to the thermal resistance of the ACHS designed by conventional topology optimization (11.17 K / W).

[0104] 7. Velocity Distribution of Hybrid Heat Sinks In an ACHS with fewer divided domains, as shown in Figure 6B (d), air can freely enter the center of the flow passage. However, dividing the design domain into smaller subdomains increases the surface area of ​​the heat sink but decreases the width of the flow passage. As a result, a significant amount of air cannot reach the center of the flow passage, resulting in stagnation within the flow passage. This creates regions where effective natural convection is not established, as shown in Figure 6B (f)-(h), making it difficult to promote heat transfer by natural convection.

[0105] Figure 10 shows the velocity distributions obtained from CFD simulations of the hybrid heat sink with design domain lengths of (a) 10 mm, (b) 20 mm, (c) 30 mm, (d) 40 mm, (e) 50 mm, and (f) 60 mm.

[0106] As shown in Figure 10, the flow field distribution on the heat sink was analyzed for design domain lengths of 10 mm, 20 mm, 30 mm, 40 mm, 50 mm, and 60 mm. As a result, the heat sink of this example was able to increase the airflow velocity in the flow passages compared to the conventional PFACHS (see Figure 6B (f)) using 11 fins. In this way, the airflow in the flow passages can be improved by performing subtractive topology optimization, which partially removes the structure on the fins.

[0107] 8. Comparison of Thermal Performance Figure 11 shows the thermal performance of a conventional plate-fin heat sink and a hybrid heat sink with design domain lengths of 10 mm, 20 mm, 30 mm, 40 mm, 50 mm, and 60 mm. The horizontal axis of Figure 11 shows the surface area to volume ratio A / V, and the vertical axis shows the thermal resistance R.

[0108] The thermal resistance of the ACHS with various design domain lengths was investigated, resulting in the results shown in Figure 11. These results were obtained from CFD simulations with a constant temperature of 85°C imposed on the bottom surface of the heat sink. A conventional plate-fin heat sink with n = 11 (11-fin PFACHS) was used as a benchmark because it demonstrated superior thermal performance (thermal resistance of 10.22 K / W) among conventional heat sink designs. As shown in Figure 11, increasing the design domain length to 10 mm, 20 mm, 30 mm, and 40 mm resulted in thermal resistances of 8.64 K / W, 8.69 K / W, 8.94 K / W, and 9.53 K / W, respectively, which are lower than the thermal resistance of the 11-fin PFACHS. However, increasing the design domain length further to 50 mm and 60 mm increased the thermal resistance to 10.53 K / W and 11.93 K / W, respectively.

[0109] Thus, the hybrid heat sink with a design area length of 10 mm exhibited the best natural convection cooling performance, achieving a 15.46% reduction in thermal resistance compared to the conventional plate fin (11-fin PFACHS). Furthermore, the hybrid heat sink of this example can improve internal airflow distribution by selectively removing fin material to increase heat dissipation rate compared to the conventional 11-fin PFACHS when the design area length is less than 40 mm. On the other hand, extending the design area beyond 40 mm does not result in improved heat transfer. This is due to an excessive reduction in heat transfer area, as shown in Figures 11 and 9.

[0110] Figure 12 shows the thermal performance of a conventional plate-fin heat sink and a hybrid heat sink with design domain lengths of 10 mm, 20 mm, 30 mm, 40 mm, 50 mm, and 60 mm when radiation is considered. Figure 12(a) shows a comparison of heat dissipation, and Figure 12(b) shows a comparison of thermal resistance.

[0111] Figure 12(a) shows the heat dissipation rates for the 11-fin PFACHS and hybrid heat sink design domain lengths of 10 mm, 20 mm, 30 mm, 40 mm, 50 mm, and 60 mm at a base temperature of 85°C and an ambient temperature of 20°C. The heat dissipation rate is the amount of heat released from the heat sink, i.e., the amount of heat lost by the heat sink. The heat dissipation rate shown here is expressed in the same physical quantity (electrical energy) as the heat rate described above.

[0112] Heat dissipation is classified into three categories: convective heat dissipation (conv), radiative heat dissipation (rad), and total heat dissipation (total), which is the sum of convection and radiation. The radiative heat dissipation for hybrid heat sinks with design domain lengths of 10 mm, 20 mm, 30 mm, 40 mm, 50 mm, and 60 mm was 1.49 W, 1.43 W, 1.39 W, 1.34 W, 1.39 W, and 1.4 W. For all types of heat sinks, the radiative heat dissipation was approximately 1.5 W, suggesting that radiation plays a relatively small role in the total heat dissipation of the heat sink. The convective heat dissipation was much higher than the radiative heat dissipation, indicating that convective heat dissipation is the dominant factor. On the other hand, the hybrid heat sinks with design domain lengths of 10 mm, 20 mm, 30 mm, and 40 mm had a heat dissipation of 7.89 W.

[0113] The total heat dissipation rates were 9.01 W, 8.91 W, 8.66 W, and 8.16 W, respectively. However, increasing the design region length to 50 mm and 60 mm slightly reduced the total heat dissipation to 7.56 W and 6.85 W, respectively. The contribution of radiation was small, showing a similar trend to convective heat dissipation. Compared to the conventional plate fin (11 PFACHS), the hybrid heat sinks with design region lengths of 10 mm, 20 mm, 30 mm, and 40 mm achieved total heat dissipation rate improvements of 14%, 12.9%, 9.8%, and 3.4%.

[0114] Figure 12(b) shows the thermal resistance of the 11-fin PFACHS and hybrid heat sink with design region lengths of 10 mm, 20 mm, 30 mm, 40 mm, 50 mm, and 60 mm. Compared to the conventional plate fin (11-fin PFACHS), the thermal resistance of the hybrid heat sink with design region lengths of 10 mm, 20 mm, 30 mm, and 40 mm achieved reductions of 12%, 11%, 9%, and 3%, respectively. The hybrid heat sink with design region length of 10 mm showed the best cooling performance, achieving a 12% reduction in thermal resistance compared to the conventional plate fin (11-fin PFACHS).

[0115] 9. Weight Comparison FIG. 13 shows the solid volume fraction of the 11-fin PFACHS and hybrid heat sinks with design domain lengths of 10 mm, 20 mm, 30 mm, 40 mm, 50 mm, and 60 mm.

[0116] The solids volume fraction is divided into three categories: the fins, the base, and the total solids volume fraction, which is the sum of the fins and the base. For the 11-fin PFACHS and hybrid heat sink, the base is fixed at 60 mm x 60 mm x 3 mm. Therefore, the base solids volume fraction is constant and is 23% of the total solids volume fraction. The fin solids volume fraction of the 11-fin PFACHS is 13.23%. The fin solids volume fractions of the hybrid heat sink with design domain lengths of 10 mm, 20 mm, 30 mm, 40 mm, 50 mm, and 60 mm are 11.23%, 10.17%, 8.6%, 7.47%, 5.72%, and 4.75%, respectively. The fin solids volume fraction of the hybrid heat sink is reduced by up to 15%, 23%, 35%, 44%, 57%, and 64% compared to the 11-fin PFACHS. The total solids volume fraction (TSV) of the PFACHS (11-fin benchmark) shows a similar trend to that of the fins, since the TSV is constant. For the benchmark 11-fin PFACHS, the TSV is 37%. For ACHSs with design domain lengths of 10 mm, 20 mm, 30 mm, 40 mm, 50 mm, and 60 mm, the TSVs are 35%, 33.94%, 32.37%, 31.24%, 29.49%, and 28.52%, respectively. Therefore, compared to the 11-fin PFACHS, the TSVs are significantly reduced by 5.4%, 8.5%, 12.5%, 15.6%, 20.3%, and 22.9%, respectively.

[0117] The heat sink designed using the iterative additive-subtractive topology optimization method not only improves the heat dissipation rate, but also reduces the solid volume fraction of the heat sink, thereby achieving weight reduction.

[0118] 10. Functional AM-Processed Hybrid Heat Sink Prototypes Figure 14 shows three 3D views of heat sinks fabricated by selective laser melting. Images of three AM ACHS are shown in Figure 14. Figure 14(a) shows an 11-fin PF ACHS, Figure 14(b) shows a hybrid ACHS with a 10 mm design region length, and Figure 14(c) shows a hybrid ACHS with a 20 mm design region length.

[0119] (a) The 11-fin PFACHS has a linear overall structure with parallel, evenly spaced fins. (b) The hybrid heat sink with a 10 mm long design domain has fins with a more complex, irregular pattern compared to the straight fins. A 10 mm wide passage runs through the center of the heat sink. This passage houses a centrally located chevron-shaped fin and seamlessly integrates with the two rows of straight fins. (c) The hybrid heat sink with a 20 mm long design domain has a 20 mm wide passage running through the center of the heat sink. Here, a larger chevron-shaped fin is placed and connects the two rows of straight fins.

[0120] The thermal performance of the hybrid heat sinks with design domain lengths of 10 mm and 20 mm was experimentally measured and compared to the 11-fin PFACHS. Room temperatures were chosen to range from 21.8°C to 22.6°C to replicate the ambient temperatures used in the CFD simulations.

[0121] Figure 15(a) is a graph showing the change in heat transfer coefficient due to temperature difference for an 11-fin PFACHS with a design area length of 10 mm and a hybrid heat sink, Figure 15(b) is a graph showing the change in thermal resistance versus heat amount for an 11-fin PFACHS with a design area length of 10 mm and a hybrid heat sink, Figure 15(c) is a graph showing the change in heat transfer coefficient due to temperature difference for an 11-fin PFACHS and a hybrid heat sink with a design area length of 20 mm, and Figure 15(d) is a graph showing the change in thermal resistance versus heat amount for an 11-fin PFACHS with a design area length of 20 mm and a hybrid heat sink.

[0122] Figure 15(a) shows the relationship between the temperature difference ΔT and the heat transfer coefficient (linear approximation) for the 11-fin PFACHS and hybrid heat sink. Figure 15(a) shows the results of a comparative analysis of the heat transfer coefficient as a function of the temperature difference, i.e., the excess temperature of the heat sink base relative to the ambient air, for two different types of fin configurations (11 PFACHS and a hybrid heat sink with a 10 mm design domain length). The heat transfer rate increases with increasing temperature difference. As shown in this figure, the relationship between the heat transfer coefficient and the temperature difference is linear for each heat sink. This linear correlation trend is very similar to the results reported by Senol et al., which show a similar linear correlation between the heat transfer coefficient and the temperature difference. This is primarily due to the fact that when the airflow in the flow channel changes due to buoyancy, the Grashoff number needs to be changed by adjusting the spacing between the two fins, the fin height, and the fin length. As shown in this figure, the hybrid heat sink with a design domain length of 10 mm achieves a higher heat transfer coefficient than the 11-fin PFACHS.

[0123] Figure 15(b) shows the relationship between heat rate and thermal resistance R (polynomial approximation) for the 11-fin PFACHS and the hybrid heat sink. Figure 15(b) shows the results of a comparative analysis of heat rate and thermal resistance R for two different types of fin configurations. For example, the thermal resistance R of the 11-fin PFACHS is 8.4 K / W, 8.0 K / W, 7.8 K / W, 7.3 K / W, 7.0 K / W, and 6.7 K / W when the heat rate is 4.4 W, 6.0 W, 7.5 W, 9.3 W, 11.3 W, and 13.6 W, respectively. On the other hand, the thermal resistance R of the hybrid heat sink with a 10 mm design domain length is 7.8 K / W, 7.3 K / W, 7.0 K / W, 6.7 K / W, 6.4 K / W, and 6.1 K / W for heat rates of 4.48 W, 5.9 W, 7.6 W, 9.3 W, 11.3 W, and 13.2 W, respectively. The relationship between heat rate and thermal resistance in this data is quadratic, with an increase in heat rate correlating with a decrease in thermal resistance. For example, the 11-fin PFACHS (solid line) exhibits a higher thermal resistance R than the hybrid heat sink with a 10 mm design domain length (dashed line). Specifically, the thermal resistance R of the 11-fin PFACHS is approximately 10% higher than that of the 10 mm design domain length PFACHS. Note that differences between simulation and experiment may occur due to mesh element accuracy and air temperature fluctuations during the experiment.

[0124] Figures 15(c) and (d) show the results of a comparative experiment between an 11-fin PFACHS and a hybrid heat sink with a design domain length of 20 mm.

[0125] Figure 15(c) shows the relationship (linear approximation) between the temperature difference ΔT and the heat transfer coefficient for the 11-fin PFACHS and the hybrid heat sink. As shown in Figure 15(c), for the hybrid heat sink with a design domain length of 20 mm, the relationship between the heat transfer coefficient and the temperature difference ΔT is linear.

[0126] Figure 15(d) shows the relationship (polynomial approximation) between the heat rate and the thermal resistance R for the 11-fin PFACHS and the hybrid heat sink. As shown in Figure 15(d), the thermal resistance R of the 11-fin PFACHS is approximately 8% higher than that of the PFACHS with a design domain length of 20 mm.

[0127] Also, looking at the whole of FIG. 15, the hybrid heat sinks with design area lengths of 10 mm and 20 mm both have significantly reduced thermal resistance compared to the conventional plate fin (11-fin PFACHS).

[0128] Furthermore, when comparing hybrid heat sinks with design region lengths of 20 mm and 10 mm, the hybrid heat sink with a design region length of 10 mm has a slightly lower thermal resistance R than the hybrid heat sink with a design region length of 20 mm, and the rate of decrease (slope) of thermal resistance with increasing heat rate is greater (see (b) and (d) of Figure 15). The hybrid heat sink with a design region length of 10 mm is more efficient than the hybrid heat sink with a design region length of 20 mm, and can improve heat dissipation characteristics over a wide range of heat source power outputs.

[0129] 11. Effect of Ambient Temperature The hybrid heat sink described above was designed based on an ambient temperature of 20°C. While the above demonstrated that the heat dissipation performance of the hybrid heat sink was superior to that of the 11-fin PFACHS, changes in buoyancy may alter the fluid flow path, and the heat sink may be required to operate at different ambient temperatures. To verify whether the hybrid heat sink can maintain its thermal performance under different environmental conditions, additional experiments were conducted under tropical climate conditions with ambient temperatures ranging from 27.7°C to 29.6°C.

[0130] Figure 16 shows the thermal resistance of three types of ACHS experimentally determined at ambient temperatures ranging from 27.7°C to 29.6°C. Figure 16(a) shows the relationship between the heat rate and thermal resistance R of the 11-fin PFACHS and a hybrid heat sink with a design area length of 10 mm. Figure 16(b) shows the relationship between the heat rate and thermal resistance R of the 11-fin PFACHS and a hybrid heat sink with a design area length of 20 mm.

[0131] Specifically, Figure 16(a) shows the results of a comparative analysis of the heat rate and thermal resistance R for two different types of fin configurations, i.e., an 11-fin PFACHS and a hybrid heat sink with a design domain length of 10 mm. For example, the thermal resistance R for the 11-fin PFACHS is 8.1 K / W, 7.7 K / W, 7.3 K / W, 7.0 K / W, 6.7 K / W, and 6.5 K / W when the heat rates are 4.6 W, 6.0 W, 7.6 W, 9.3 W, 11.2 W, and 13.3 W, respectively. On the other hand, the thermal resistance R of the hybrid heat sink with a 10 mm design region is 7.9 K / W, 7.2 K / W, 6.8 K / W, 6.5 K / W, 6.2 K / W, and 6.0 K / W for heat rates of 4.4 W, 5.9 W, 7.6 W, 9.3 W, 11.2 W, and 13.3 W, respectively. The relationship between heat rate and thermal resistance in this data is quadratic, with an increase in heat rate correlating with a decrease in thermal resistance. The 11-fin PFACHS (solid line) has a higher thermal resistance R than the hybrid heat sink with a 10 mm design region (dashed line). Using this quadratic relationship to derive the thermal resistance R for the same heat load, the thermal resistance R of the PFACHS with a 10 mm design region is approximately 7% lower than the thermal resistance R of the 11-fin PFACHS.

[0132] Figure 16(b) shows the results of a comparative analysis of the heat rate and thermal resistance R of the 11-fin PFACHS and the hybrid heat sink with a design area length of 20 mm. The hybrid heat sink with a design area length of 20 mm has a lower thermal resistance R than the 11-fin PFACHS over the entire range of heat rates tested.

[0133] Comparing hybrid heat sinks with design region lengths of 20 mm and 10 mm, the hybrid heat sink with a design region length of 20 mm has a slightly lower thermal resistance R than the hybrid heat sink with a design region length of 10 mm when the heat rate is less than 7 W. Thus, the hybrid heat sinks with design region lengths of 10 mm and 20 mm have significantly lower thermal resistance R than the conventional plate fin (11-fin PFACHS), even when the ambient temperature is higher, between 27.7°C and 29.6°C.

[0134] [12. Discussion] Conventional topology optimization is limited to heat sinks with a small surface area-to-volume ratio A / V and large fin dimensions, resulting in limited effectiveness in reducing weight and improving heat dissipation. In this example, a sequential additive-subtractive topology optimization method is proposed to generate a structure with a high surface area-to-volume ratio in order to simultaneously improve cooling performance and reduce weight. Conventionally, applying topology optimization to ACHSs has been used to reduce thermal resistance, but this often comes at the expense of increased volume and weight. In contrast, the method proposed in this example not only reduces thermal resistance, but also reduces the overall weight of the ACHS.

[0135] Another important advantage of the iterative addition-subtraction topology optimization method proposed in this example is that it is independent of the design parameters used in the TO algorithm. ｆ , q ａ The sensitivity of design parameters including

[0136] FIG. 17 is a diagram showing the influence of design parameters on thermal resistance.

[0137] FIG. 17(a) shows the effect of volume constraints on thermal resistance R, and FIG. 17(b) shows the effect of volume constraints on thermal resistance R. ｆ The influence of q on the thermal resistance R is shown in FIG. ａ The effect of on the thermal resistance R is shown.

[0138] As shown in Fig. 17, for example, when the volume constraints are set to 0.3, 0.5, and 0.7, respectively, and the length of the design domain is set to 20 mm, the thermal resistances R are 8.70 K / W, 8.69 K / W, and 8.45 K / W, respectively, with a variation of only 0.25 K / W, and a relative variation of only 2.9%. ｆ When q is set to 0.1, 1, 10 and 100, respectively, the thermal resistance R becomes 8.46 K / W, 8.69 K / W, 8.82 K / W and 8.99 K / W, and the variation is only 0.53 K / W, and the relative variation is only 5.9%. ａ When the values ​​of R are set to 0.1, 1, 10, and 100, respectively, the thermal resistances R are 8.50 K / W, 8.69 K / W, 8.53 K / W, and 9.09 K / W, with a variation of only 0.59 K / W and a relative variation of only 6.5%. This demonstrates the robustness of the proposed iterative additive-subtractive topology optimization method. On the other hand, existing topology optimization methods often rely on extensive numerical studies and experiments to determine appropriate setup parameters. In contrast, the method proposed in this example does not require such an exhaustive procedure and is independent of the setup parameters.

[0139] [13. Conclusion] In this example, a new design-to-manufacturing approach is proposed to overcome the issues of insufficient optimization of heat transfer paths in conventional ACHS designs and the low surface area-to-volume ratio of conventional TO structures. Specifically, a sequential additive-subtractive topology optimization method is proposed to create a new hybrid ACHS, and a prototype is fabricated using metal AM. The main results of this example are as follows:

[0140] (1) The proposed iterative additive-subtractive topology optimization method simultaneously optimized the improvement of heat transfer area, heat conduction, and natural convection cooling.

[0141] (2) Compared with existing topology optimization methods, the proposed iterative additive-subtractive topology optimization method improved the surface area-to-volume ratio by as much as 84%.

[0142] (3) Compared with the conventional plate-fin heat sink (11-fin PFACHS), the hybrid ACHS exhibited lower airflow resistance, with a 15.46% reduction in convective thermal resistance.

[0143] (4) We fabricated an AM hybrid ACHS and experimentally evaluated its air-cooling performance. Compared with the benchmark 11-fin PFACHS, the hybrid ACHS reduced thermal resistance (convection and radiation) by 10% and reduced weight by 15%.

[0144] Second Embodiment A heat sink according to a second embodiment will be described with reference to FIGS.

[0145] 18 and 19 are diagrams illustrating the heat sink of the comparative example and the heat transfer coefficient of the heat sink of the comparative example.

[0146] In each of Figures 18 and 19, (a) shows a comparative example heat sink that underwent topology optimization, (b) shows a heat sink with five fins (HS1), (c) shows a heat sink with seven fins (HS2), and (d) shows a heat sink with 11 fins (HS3).

[0147] As shown in Figures 18 and 19, the heat sinks (b) to (d) with conventional comb-shaped fins have better heat dissipation performance than the heat sink (a) generated by TO (topology optimization) under the same conditions (constant solid ratio). Therefore, in this embodiment, we applied a division design and surface area addition method to generate a TO structure with a small size and increased surface area. Furthermore, rational subtraction of the TO structure was performed to reduce airflow resistance to the air deficiency zone and improve airflow distribution.

[0148] FIG. 20 is a diagram showing the heat transfer coefficients of various heat sinks.

[0149] Figure 20(a) shows the heat transfer coefficients of the heat sink of the comparative example that underwent topology optimization, and (b) to (f) show the heat transfer coefficients of the heat sink of this embodiment that is realized by the division design.

[0150] In this embodiment, a heat sink is designed using a partitioned design, which allows for mesh refinement (reducing element size) without increasing the computational load on the computer (without increasing the number of elements). This allows for the generation of finer shapes, increasing the surface area without increasing the solid content ratio, and improving heat dissipation performance. Another measure is to remove protrusions that prevent cooling air from flowing into the center region of the heat sink. This improves airflow and improves the heat dissipation performance of the heat sink.

[0151] The configuration of the heat sink according to the second embodiment will be specifically described below.

[0152] FIG. 21 is a diagram illustrating an example of a heat sink according to the second embodiment.

[0153] The heat sink 1A according to the second embodiment is a heat dissipation member that dissipates heat generated by a heat source. The heat sink 1A is made of a metal material with high thermal conductivity, such as aluminum, an aluminum alloy, or copper.

[0154] As shown in FIG. 21, the heat sink 1A includes a base 10 and a plurality of protrusions 40 provided on the base 10.

[0155] The base 10 is, for example, a rectangular parallelepiped substrate. The base 10 has a front surface 10a and a back surface 10b opposite to the front surface 10a. The front surface 10a and the back surface 10b of the base 10 are flat and parallel to each other.

[0156] In embodiment 2, too, a predetermined direction parallel to the surface 10a of the base 10 is called the first direction d1, a direction parallel to the surface 10a of the base 10 and perpendicular to the first direction d1 is called the second direction d2, and a direction perpendicular to the surface 10a of the base 10 is called the third direction d3.

[0157] The plurality of protrusions 40 protrude from the surface 10a of the base 10 in the third direction d3. Each protrusion 40 has a tree-like outer shape. Space, i.e., air, exists around the protrusions 40. When heat is dissipated using air convection, some of this air flows between the plurality of protrusions 40.

[0158] The plurality of protrusions 40 have at least two or more different shapes. At least one type of the plurality of protrusions 40 is branch-like and branches midway from the base to the tip. Furthermore, at least one type of the plurality of protrusions 40 has a curved surface on a portion of its surface.

[0159] The thickness of a portion of the protrusion 40 becomes thinner as it gets farther from the base body 10. For example, when focusing on one protrusion 40, the thickness of the tip portion far from the base body 10 is thinner than the thickness of the base portion close to the base body 10.

[0160] There are certain limitations on the number and volume of the protrusions 40 provided on the base 10. For example, the proportion of the multiple protrusions 40 provided on the surface 10a of the base 10 is 10% or more and less than 50%. More specifically, when focusing on a predetermined straight line along the surface 10a of the base 10, the total length of the line segments tangent to the predetermined straight line among the multiple protrusions 40 located on the predetermined straight line is 10% or more and less than 50% of the length of the predetermined straight line. In other words, the total length of the spatial region on the predetermined straight line is 50% or more and less than 90% of the length of the predetermined straight line segment.

[0161] The heat sink 1A of this embodiment has a plurality of divided regions D each having an equal area, and the aggregate structure of the plurality of protrusions 40 provided in one divided region D is formed so as to also apply to the other divided regions D different from the one divided region D. For example, the number of divisions of the plurality of divided regions D is 2 ｎ (n is a natural number), and the shape of the divided region D is a square. Note that the divided region D is not limited to a square, and may be an isosceles triangle.

[0162] FIG. 22 is a schematic diagram of a design domain when performing division design.

[0163] 22 shows an example in which the heat sink 1A is divided into 4, 8, 16, or 64 divided regions D. In FIG. 22, the number of divisions when performing the division design is 2. ｎ (where n is 2, 3, 4 or 6).

[0164] In this embodiment, by performing division design, the protrusions 40 in each divided region D have a similar structure. For example, when viewed from a direction perpendicular to the base 10 (third direction d3), the multiple protrusions 40 provided in one divided region D and the multiple protrusions 40 provided in the other divided regions D are line-symmetrical with respect to the boundary line between the one divided region D and the other divided regions D. Alternatively, when viewed from a direction perpendicular to the base 10, the multiple protrusions 40 provided in one divided region D and the multiple protrusions 40 provided in the other divided regions D are rotationally symmetrical with respect to the midpoint of the boundary line between the one divided region D and the other divided regions D.

[0165] The protrusions 40 are designed, for example, by performing topology optimization using a computer. In this embodiment, when the plurality of protrusions 40 are designed using a computer, topology optimization is performed using the constraint of arranging a heat source on the back surface 10b of the base 10, which is the substrate, and the objective function is to improve the amount of heat dissipation by convection in the heat sink 1A. The shape obtained by this topology optimization is used as the shape of the protrusions 40.

[0166] For example, first, a domain in which the protrusions 40 are to be generated is divided into multiple domains with equal volume and symmetry (line symmetry or point symmetry). Then, the structure of the protrusions 40 generated by topology optimization in one of the divided domains is applied to the other domains to generate all of the protrusions 40. The topology optimization calculation algorithm is based on an equation for maximizing heat conduction performance. The topology optimization calculation algorithm is also based on an equation for maximizing convection performance. Furthermore, the heat sink 1A generated as described above may be generated by removing some of the protrusions 40 that obstruct the airflow based on theoretical grounds. The theoretical grounds may be derived from the results of thermal fluid analysis.

[0167] A method for designing the heat sink 1A of the second embodiment will be described in detail.

[0168] In topology optimization algorithms, it is desirable to set the minimum element size small in advance to obtain a shape with a large surface area for the same volume. Considering the actual manufacture of the heat sink 1A, the minimum element size can be set as small as 0.2 mm, which is the printing capability of selective laser melting (SLM), an additive manufacturing technology. However, for example, if the minimum element size is changed from 1 mm to 0.2 mm, the number of elements to be calculated increases by three orders of magnitude, requiring enormous computational resources. This makes it unrealistic to implement a design process in which the results are analyzed and fed back into the design.

[0169] Therefore, the domain (design area) of the heat sink 1A is divided into 2 ｎ The area of ​​the design region relative to the area of ​​the base body 10 is designed to be 1 / 4, 1 / 8, 1 / 16, and 1 / 64, respectively (see FIG. 22).

[0170] Fig. 23 is a diagram showing an example of a divided region, and Fig. 24 is a diagram showing another example of a divided region.

[0171] 23 and 24 show the dimensional parameters of the split domains: l is the width of the split domain and h is the height of the split domain.

[0172] FIG. 25 is a diagram illustrating a specific example of a heat sink according to the second embodiment.

[0173] 25A shows an example where n=2 (the area of ​​the divided regions is 1 / 4), (b) shows an example where n=3 (the area of ​​the divided regions is 1 / 8), (c) shows an example where n=4 (the area of ​​the divided regions is 1 / 16), and (d) shows an example where n=6 (the area of ​​the divided regions is 1 / 64). For example, increasing the number of divisions reduces the size of the domains. Therefore, if one domain is designed using the same number of elements as before division, the minimum element size can be reduced.

[0174] FIG. 26 is a diagram showing the number of divisions into the design area of ​​the heat sink and the heat transfer coefficient.

[0175] Figure 26(a) shows the heat transfer coefficient of a heat sink designed without division (n=1), while Figures 26(b) to 26(e) show the heat transfer coefficient of a heat sink 1A with a divided region of 1 / 4, 1 / 8, 1 / 16, and 1 / 64, respectively.

[0176] Comparing the heat sinks 1A of this embodiment (b) to (e), the surface area of ​​the protrusions 40 increases as the size of the divided regions decreases. The heat sinks 1A of (b) to (e) also have improved heat transfer coefficients compared to the heat sink without division (n=1). Thus, the CFD simulation of the heat sink 1A of this embodiment shows that the heat transfer coefficient can be significantly improved.

[0177] On the other hand, as a result of the thermal fluid analysis, it was found that some of the protrusions 40 of the produced heat sink 1A obstruct the flow of air.

[0178] FIG. 27 shows the structure of the heat sink, the temperature field, and the velocity field.

[0179] In Fig. 27(a), the heat sink 1A before the protrusion 40 that obstructs the air flow is removed is a 1 / 16 design, and the heat sink 1A after the protrusion 40 is removed is a 1 / 16-R design. Fig. 27(b) shows a temperature distribution diagram, and Fig. 27(c) shows a velocity vector diagram.

[0180] Taking the 1 / 16-R heat sink 1A in FIG. 27 as an example, the circled protrusion 40 in (a) prevents air from flowing from the periphery toward the center of the heat sink 1A (see (c) on the left). Therefore, the circled protrusion 40 was removed from the heat sink 1A to create the 1 / 16-R heat sink shown in the right of FIG. 27. The 1 / 16-R heat sink 1A promotes airflow from the periphery toward the center (see (c) on the right).

[0181] FIG. 28 is a diagram showing the design area size, volume, solid volume fraction, surface area, surface area to volume ratio, and heat transfer coefficient of the heat sinks of the 1 / 16 design and the 1 / 16-R design.

[0182] As shown in FIG. 28, the heat sink of the 1 / 16-R design has a reduced volume and surface area due to the removal of part of the protrusion 40, but has an improved heat transfer coefficient compared to the heat sink of the 1 / 16 design.

[0183] (Configuration and Effects of Heat Sink According to Second Embodiment) The configuration and effects of the heat sink 1A according to the second embodiment will be illustrated.

[0184] The heat sink 1A of Example 1 includes a base 10 and a plurality of protrusions 40 provided on the base 10. The plurality of protrusions 40 have a plurality of divided regions D configured with equal areas. A collective structure of the plurality of protrusions 40 provided in one divided region D among the plurality of divided regions D is also provided in another divided region D different from the one divided region D.

[0185] By applying the collective structure of the multiple protrusions 40 provided in one divided region D as described above to the other divided regions D, the design load when designing the heat sink 1A can be reduced.

[0186] The heat sink 1A of Example 2 is the heat sink described in Example 1, and when viewed from a direction perpendicular to the base 10, the multiple protrusions 40 provided in one divided area D and the multiple protrusions 40 provided in another divided area D may be linearly symmetrical with respect to the boundary line between one divided area D and the other divided area D, or may be rotationally symmetrical with respect to the midpoint on the boundary line between one divided area D and the other divided area D.

[0187] In this way, by forming the protrusions 40 of one divided region D and the protrusions 40 of the other divided regions D in line symmetry or rotational symmetry, the design load when designing the heat sink 1A can be reduced.

[0188] The heat sink 1A of Example 3 is the heat sink described in Example 2, and the number of divisions of the plurality of division regions D is 2. ｎ (where n may be 2, 3, 4 or 6).

[0189] By forming the divided regions D with the above number of divisions, the design load when designing the heat sink 1A can be reduced.

[0190] The heat sink 1A of Example 4 is the heat sink according to any one of Examples 1 to 3, and the proportion of the plurality of protrusions 40 provided on the surface 10a of the base 10 may be 50% or less.

[0191] As described above, by setting the ratio of the plurality of protrusions 40 to 50% or less, it is possible to promote the flow of air from the outer periphery to the center, thereby improving the amount of heat dissipation by convection.

[0192] Third Embodiment A heat sink according to a third embodiment will be described with reference to FIGS.

[0193] Attempts to improve the performance of heat sinks have been made, for example, by changing the fin configuration, increasing the emissivity, etc. In recent years, many algorithms have been developed to generate optimal geometric designs to increase the heat transfer coefficient, and topology optimization (TO), for example, has attracted widespread interest because it can generate innovative structures that meet design goals without being bound by preconceptions.

[0194] Figure 29 shows a conventional plate-fin heat sink. Figure 30 shows the total heat flow with respect to emissivity. Figure 31 shows the temperature profile on the top surface of the fins. Figure 32 shows the velocity vector field in the plane at height z=7 mm of the heat sink. Figure 33 shows the temperature contours in the plane at height z=7 mm of the heat sink.

[0195] As shown in Figure 32, the heat flow rate of a conventional plate-fin heat sink is largely influenced by convection, but radiation also plays a role. As shown in Figure 32, the flow rate at the center of the conventional plate-fin heat sink is nearly zero, resulting in a lack of air supply. This results in insufficient convective cooling. Furthermore, as shown in Figure 33, the conventional plate-fin heat sink is only able to cool the outer peripheral edge area.

[0196] To solve these problems, we first fabricated cross plate fins (CF) that reduce convection heat resistance.

[0197] FIG. 34 shows cross-fin heat sinks with different fin densities.

[0198] Each of the heat sinks shown in Fig. 34 has four quadrants. The heat sink (CF1) shown in Fig. 34(a) has six fins in each quadrant. The heat sink (CF2) shown in Fig. 34(b) has ten fins in each quadrant. The heat sink (CF3) shown in Fig. 34(c) has twenty fins in each quadrant. For example, the spacing between the fins is narrower in CF2 than in CF1, and narrower in CF3 than in CF2.

[0199] 34, in order to facilitate the inflow of air from multiple directions, multiple plate fins 50 are arranged along or parallel to the diagonal lines of the heat sink, with some of the plate fins 50 crossing each other. With this configuration, air flows into the heat sink from all four sides, which is expected to improve the thermal performance of the heat sink.

[0200] In the third embodiment, a hybrid heat sink 1B was fabricated that has the functions of both the TO tree type fins (TF) of the second embodiment and the cross plate fins (CF).

[0201] Next, a TO-tree fin (TF) heat sink will be described.

[0202] Figure 35 is a schematic diagram of boundary conditions used in topology optimization, and Figure 36 is a division scheme of the design domain.

[0203] FIG. 37(a) is the TO shape generated by COMSOL Multiphysics software, and FIG. 37(b) is the exported ".STL" file.

[0204] Figure 38 shows the heat sink shape post-processed in SpaceClaim software. In this post-processing, the STL facets shown in Figure 38(a) were smoothed to the shape shown in Figure 38(b). The sharp edges (circled areas) shown in Figure 38(b) were then removed (see Figure 38(c)), and the resulting file was then converted to a CAD file (see Figure 38(d)).

[0205] FIG. 39 is a rendering CAD image of the heat sink.

[0206] 39(a) shows an example of TF8 employing a 1 / 8 division method (the area of ​​the divided regions is 1 / 8), TF16 shown in (b) shows an example of TF16 employing a 1 / 16 division method (the area of ​​the divided regions is 1 / 16), and TF64 shown in (c) shows an example of TF64 employing a 1 / 64 division method (the area of ​​the divided regions is 1 / 64). In this example, the shape of the divided regions is a square, but is not limited thereto and the shape of the divided regions may be an isosceles triangle.

[0207] Here, the function of a cross plate fin (CF) was further added to each of the above TF8, TF16, and TF64 to produce a hybrid type heat sink.

[0208] FIG. 40 shows a TO design heat sink and a hybrid heat sink.

[0209] TF16-R shown in FIG. 40(a) is a TO-designed heat sink designed by removing the small tree structure of TF16.

[0210] CF0-TF16 shown in FIG. 40(b) is a heat sink 1B designed by integrating the TF16-R with cross-shaped plate fins 50. In the CF0-TF16, two plate fins 50 are arranged diagonally, passing through the vertices of the square-shaped surface 10a. Furthermore, in the CF0-TF16, two plate fins 50 are arranged perpendicular to each side of the square-shaped surface 10a, passing through the midpoint of each side. In other words, in the CF0-TF16, the plate fins 50 are formed radially from the center of the substrate surface 10a. The angular interval (or angular pitch) between adjacent plate fins 50 in the rotational direction, with the center of the surface 10a as the center point, is 45°.

[0211] CF1-TF16 shown in FIG. 40(c) and CF2-TF16 shown in FIG. 40(d) are heat sinks 1B designed by removing the small tree structure of TF16 and integrating it with cross-shaped plate fins 50.

[0212] FIG. 41 is a cross-sectional side view of the heat sinks of TF16 and CF0-TF16.

[0213] While the heat sink for TF16 shown in Fig. 41(a) forms a projection area, the heat sink for CF0-TF16 shown in Fig. 41(b) is provided with cross-shaped plate fins 50, which prevents the formation of a projection area. This allows the heat sinks for CF0-TF16 to improve radiant heat transfer.

[0214] Fig. 42 shows various heat sinks manufactured in this embodiment, and Fig. 43 shows the thermal resistance and weight of various heat sinks.

[0215] The Al6061-S shown in (a) of Figure 42 is a heat sink with conventional fins. (f) of Figure 42 is the heat sink 1A of TF8, (g) is the heat sink 1A of TF16, (h) is the heat sink 1A of TF64, and (i) is the heat sink 1A of TF16-R. (j) of Figure 42 is the heat sink 1B of CF0-TF16, (k) is the heat sink 1B of CF1-TF16, and (l) is the heat sink 1B of CF2-TF16.

[0216] In Figure 43, the heat sinks with excellent thermal performance are CF0-TF16, CF2, and TF16-R. These heat sinks have a thermal resistance that is 10% or more lower than the conventional Al6061-S heat sink. In terms of weight, compared to the conventional Al6061-S, the TF16-R has a 20.7% weight reduction, the CF2 has an 18.7% weight reduction, and the CF0-TF16 have a 14.8% weight reduction.

[0217] The configuration of a heat sink 1B according to the third embodiment will be illustrated.

[0218] The heat sink 1B of Example 1 includes a base 10, which is a rectangular parallelepiped substrate, and a plurality of protrusions 40 provided on the base 10. The plurality of protrusions 40 have a plurality of divided regions D, each having an equal area. A collective structure of the plurality of protrusions 40 provided in one of the divided regions D is also provided in another divided region D different from the one divided region D. Furthermore, cross-shaped plate fins 50 are provided on the base 10. The plate fins 50 are arranged along the diagonal of the base 10.

[0219] According to this configuration, air can be introduced into the heat sink 1B from all four sides, improving the amount of heat dissipation by convection.

[0220] Other Embodiments Although the heat sink and the like according to the present disclosure have been described above based on the embodiments, the present disclosure is not limited to the above-described embodiments.

[0221] In the above, the shape of the fins 20 or the protrusions 40 is determined by topology optimization, but this is not limiting. For example, the shape of the fins 20 or the protrusions 40 may be determined by making slight modifications based on the shape of the fins 20 or the protrusions 40 obtained by topology optimization.

[0222] In addition, the present disclosure also includes forms obtained by applying various modifications to the above-described embodiments that a person skilled in the art would conceive, and forms realized by arbitrarily combining the components and functions of the embodiments within the scope of the present disclosure. Furthermore, the present disclosure also includes any combination of two or more claims from among the multiple claims set forth in the claims at the time of filing, within the scope of technical compatibility. For example, when a dependent claim set forth in the claims at the time of filing is made into a multiple claim or multiple multiple claims that cite all of the superordinate claims within the scope of technical compatibility, the present disclosure also includes all combinations of claims included in that multiple claim or multiple multiple multiple claims.

[0223] The technology of the present disclosure can be used in air-cooled heat sinks and the like.

[0224] 1, 1A, 1B Heat sink 10 Base body 10a Front surface 10b Back surface 20 Fin 21 Center portion 22 End portion 25 Opening 40 Protrusion portion 50 Plate fin d1 First direction d2 Second direction d3 Third direction D Divided region

Claims

1. A heat sink comprising: a base; and a plurality of fins protruding from a surface of the base, wherein the plurality of fins extend in a plate shape along a first direction parallel to the surface of the base and are arranged at intervals in a second direction parallel to the surface of the base and perpendicular to the first direction, and each of the plurality of fins is provided with an opening that penetrates the fin in its thickness direction.

2. The heat sink according to claim 1, wherein the openings provided in each of the plurality of fins are provided in the center of the fin in the first direction.

3. The heat sink according to claim 2, wherein the length of the central portion in the first direction is 80% or less of the length of the fins.

4. The heat sink according to claim 1, wherein the openings provided in two of the fins adjacent to each other in the second direction have different shapes.

5. The heat sink according to claim 1, wherein the openings provided in each of two fins adjacent to each other in the second direction are formed so as not to completely coincide when viewed from the second direction.

6. The heat sink according to any one of claims 1 to 5, wherein the opening is at least one of a notched hole and a through hole.

7. A heat sink according to any one of claims 1 to 5, wherein the opening has a curved shape when viewed from the second direction.

8. The heat sink according to claim 1, wherein the base is a rectangular parallelepiped substrate, and the plurality of fins are symmetrical with respect to a plane that passes through the center of the base and is perpendicular to an axis extending in the first direction.

9. The heat sink according to claim 1, wherein the base is a rectangular parallelepiped substrate, and the plurality of fins are symmetrical with respect to a plane that passes through the center of the base and is perpendicular to an axis extending in the second direction.

10. A method for designing a heat sink comprising a substrate and a plurality of fins extending in a flat shape along a first direction parallel to the surface of the substrate and arranged at intervals in a second direction parallel to the surface of the substrate and perpendicular to the first direction, wherein when using a computer to design the central portions of each of the plurality of fins in the first direction, topology optimization is performed with a constraint that a heat source be placed on the back surface of the substrate and an objective function of improving the amount of heat dissipation by convection from the heat sink, and a shape including the central portions obtained by the topology optimization is used as the shape of the plurality of fins.

Images