Preparation method of a bionic double-layer fractal micro-channel radiator and fin group thereof

Abstract

The application discloses a kind of bionic double-layer fractal micro-channel radiator and its fin group preparation method, it is related to radiator technical field, including the fin group being fixed on cooling liquid channel, fin group includes multiple wave-shaped fin matrix, two groups of symmetrically arranged inclined scales are fixedly arranged on both sides of fin matrix, each group of inclined scales includes multiple inclinedly arranged inclined scale main body, and inclined scale main body includes upper layer imitation butterfly scale and lower layer imitation butterfly scale.The application can form flow separation, destroy air boundary layer, increase heat exchange capacity, strengthen disturbance capacity and local fluid medium flushing, reduce fluid impurity attachment and deposition, improve the long-term working stability of radiator.By additive manufacturing technology, the size of butterfly scale sawtooth edge tip can be customized, which can avoid the problems of traditional process, such as difficulty in one-piece forming, complex structure difficult to process, low material utilization, etc.

Description

Technical Field

[0001] This invention relates to the field of radiator technology, specifically to a biomimetic double-layer fractal microchannel radiator and its fin assembly preparation method. Background Technology

[0002] With the continuous development and vigorous promotion of the automotive industry, high-efficiency and lightweight automotive radiators, especially louvered finned parallel flow heat exchangers, have become a research hotspot. Parallel flow radiators are characterized by their compact structure, small size, low material consumption, and high heat transfer coefficient. Currently widely used louvered fins all have uniformly distributed louvered turbulence structures within their substrate. Existing louvered fins are generally straight fins. When air flows within the louvered area, the louvered fins can guide the airflow and hinder the development of the fluid boundary layer, increasing turbulence and enhancing heat transfer. To further improve heat dissipation performance, breakthroughs in structural design are needed, requiring the development of more efficient heat transfer fins to enhance heat transfer performance.

[0003] Furthermore, the inclined fins of traditional radiators are mainly manufactured using conventional processes such as stamping and bending. These processes have drawbacks, including limited structural forming, difficulty in integrated molding, difficulty in processing complex flow channels and fine structures, and low material utilization. They cannot meet the requirements of high-performance radiators and louvered fins for optimized heat exchange structures. Therefore, efficient and convenient manufacturing processes are needed.

[0004] Therefore, a biomimetic double-layer fractal microchannel heat sink and its fin assembly fabrication method are proposed to solve the above problems. Summary of the Invention

[0005] To achieve the above objectives, the present invention provides the following technical solution: a biomimetic double-layer fractal microchannel radiator, comprising a fin assembly fixed on a coolant channel, the fin assembly comprising multiple wavy fin substrates, windows on both sides of the fin substrates, and two sets of symmetrically arranged inclined scales fixedly arranged in each window, each set of inclined scales comprising multiple inclined scale bodies, the inclined scale body comprising an upper butterfly-shaped scale and a lower butterfly-shaped scale connected together by a hexahedral connecting post, the top of both the upper and lower butterfly-shaped scales being provided with butterfly-scale serrated edges, the width of the multiple serrations in the butterfly-scale serrated edges gradually increasing from both sides to the middle, the upper butterfly-shaped scale having fractal hollow microchannels, and the lower butterfly-shaped scale having two symmetrically distributed wavy hollow microchannels, the width of the multiple waves in the wavy hollow microchannels gradually decreasing from both sides to the middle.

[0006] As a preferred embodiment, the fractal hollow microchannel includes a primary main channel, a secondary branch channel, and terminal turbulence branches. A secondary branch channel is provided at both ends of the primary main channel, and the primary main channel and the secondary branch channel are connected in the middle. Multiple inclined terminal turbulence branches are provided at both ends of the secondary branch channel.

[0007] Preferably, the angle between the terminal turbulence branch and the secondary branch is 30°.

[0008] As a preferred option, the lengths of the primary main channel, the secondary tributary channel, and the terminal turbulence branch decrease sequentially.

[0009] The present invention also provides a method for preparing a fin assembly for preparing the fin assembly of the biomimetic double-layer fractal microchannel heat sink as described above, comprising the following steps: Step 1: The fin substrate is prepared by stamping process to realize the fabrication of large-scale frame structure; Step 2: Construct a 3D model of the inclined scale body using 3D modeling software, and optimize the precision of the butterfly-shaped sawtooth edges, fractal hollow microchannels, and wave hollow microchannels in the 3D model. Then, import the optimized 3D model into the additive manufacturing equipment and use the laser selective melting (SLM) process to form the model in one piece. After forming, clean the surface of the inclined scale body to remove residual powder. Step 3: Weld two sets of inclined scales on both sides of each fin substrate. The two sets of inclined scales on the same side are symmetrically distributed to obtain a fin group.

[0010] Preferably, in step 2, when using the laser selective melting (SLM) process for integral molding, 6061 aluminum alloy powder is selected as the molding material, with a powder particle size of 15–53 μm and the molding layer thickness controlled to be 0.02 mm.

[0011] The present invention has the following beneficial effects: This invention enables flow separation, disrupts the air boundary layer, increases heat transfer capacity, enhances disturbance capability and local fluid medium scouring, reduces fluid impurity adhesion and deposition, and improves the long-term operational stability of the radiator. The butterfly-scale-like edges of this invention incorporate the structural features of natural butterfly scales, exhibiting a butterfly-scale-shaped serrated edge at the tip. This feature enables flow separation, disrupts the air boundary layer, increases heat transfer capacity, enhances disturbance capability and local fluid medium scouring, reduces fluid impurity adhesion and deposition, and improves the long-term operational stability of the radiator. By using additive manufacturing technology to customize the tip size of the butterfly-scale-shaped serrated edge, problems such as the difficulty of one-piece molding, the difficulty of processing complex structures, and low material utilization rates inherent in traditional processing methods can be avoided.

[0012] The butterfly-scale-like microchannels of this invention are complete, enhancing heat transfer efficiency. The double-layer fractal microchannels form closed cavities, ensuring leak-free fluid flow within the sealed channels. The continuous and intact heat dissipation walls, compared to surface grooved or protruding channels, avoid problems such as fluid side leakage and boundary layer disturbance, significantly improving internal convective heat transfer efficiency. The inclined scale body surface is free of grooves and gaps, exhibiting strong overall continuity, enhancing structural rigidity and deformation resistance while maintaining lightweight design. The closed cavity of the double-layer fractal microchannels eliminates the risk of fluid leakage, making it suitable for high-pressure, high-flow-rate automotive radiator applications. The double-layer fractal microchannels greatly increase the heat dissipation area of ​​the fluid medium, and the orderly flow of the internal fluid medium avoids local flow obstruction, resulting in more uniform fin temperature distribution and lower thermal stress. The double-layer fractal microchannels on the butterfly-scale-like fins enhance fluid-side heat transfer and improve turbulence. Working in synergy with the butterfly-scale serrated edges and heat transfer mechanism, they achieve layered, multi-stage turbulence, significantly improving the overall heat transfer performance of the fin assembly. Additive manufacturing of the double-layer fractal microchannel structure overcomes traditional process limitations, eliminates assembly-type contact thermal resistance, and further increases heat transfer performance. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 This is a schematic diagram of the structure of the finned substrate in this invention; Figure 3 This is a schematic diagram of the structure of the wing base and the upper butterfly-scale pattern in this invention; Figure 4 This is a schematic diagram of the upper and lower butterfly-scale structures in this invention. Figure 5 This is a schematic diagram of the structure of the lower layer of butterfly-scale-like scales, butterfly-scale-shaped serrated edges, and wavy hollowed-out microchannels in this invention. Figure 6 This is a schematic diagram of the upper butterfly-scale-like structure and the primary main channel in this invention; Figure 7 This is a schematic diagram of the structure of the primary main channel, secondary branch channels, and terminal turbulence branches in this invention.

[0014] In the diagram: 10, inlet area; 20, channel; 40, outlet area; 60, fin substrate; 80, inclined scale body; 81, upper butterfly-like scale; 82, lower butterfly-like scale; 83, hexahedral connecting column; 84, butterfly-scale serrated edge; 90, fractal hollow microchannel; 91, primary main channel; 92, secondary branch channel; 93, end turbulence branch; 100, wave-shaped hollow microchannel. Detailed Implementation

[0015] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0017] Embodiments of the present invention refer to Figures 1 to 7 A biomimetic double-layer fractal microchannel radiator includes a fin assembly fixed on a coolant channel. The fin assembly includes multiple wavy fin substrates 60 connected together (the fin substrates 60 and the coolant channel together form a channel 20). One side of the fin assembly is an inlet area 10, and the other side of the fin assembly is an outlet area 40. Windows are provided on both sides of the fin substrates 60. Two sets of symmetrically arranged inclined scales are fixedly arranged in each window. Each set of inclined scales includes multiple inclined scale bodies 80, and an airflow channel is formed between adjacent inclined scale bodies 80. The inclined scale body 80 includes an upper butterfly-shaped scale 81 and a lower butterfly-shaped scale 82 connected by a hexahedral connecting post 83. Both the upper and lower butterfly-shaped scales 81 and 82 have butterfly-scale serrated edges 84 at their tops. The width of the serrations in the butterfly-scale serrated edges 84 gradually increases from the sides towards the center. The upper butterfly-shaped scale 81 has fractal-shaped perforated microchannels 90, and the lower butterfly-shaped scale 82 has two symmetrically distributed wave-shaped perforated microchannels 100. The width of the waves in the wave-shaped perforated microchannels 100 gradually decreases from the sides towards the center. In this embodiment, both the upper and lower butterfly-shaped scales 81 and 82 have a length of 24.5 mm, a width of 9.75 mm, and a thickness of 0.1 mm. The distance between the upper and lower butterfly-shaped scales 81 and 82 is 0.1 mm.

[0018] like Figure 5 As shown, the width of multiple serrations in the butterfly-scale serrated edge 84 gradually increases from both sides towards the middle, and the width of the multiple serrations satisfies the following relationship: ; in, The serration unit number increases from both sides of the fin towards the center; the serration height is a fixed value of 0.76 mm. , These represent the widths of the outer and inner serrations, respectively, with a serration width increment factor of 1.03. <1.06. In this embodiment, the serration width sequence from the left edge of the fin towards the center: the outermost serration width... ; towards the middle are successively , , , , , , , to the maximum serration width in the middle The width difference between adjacent serrations is 0.05mm, and they gradually increase. The edge distribution of the butterfly-scale serrations on the right side of the fin is completely symmetrical with that on the left side. That is, from the right edge to the middle, the serration width also gradually increases from 1.0mm to 1.45mm, forming a symmetrical serration structure that is "narrow on both sides and wide in the middle".

[0019] like Figure 5 As shown, the width of multiple waves in the wave-shaped perforated microchannel 100 gradually decreases from both sides towards the middle, and the width of the multiple waves satisfies the following relationship: ; in, The wave unit number increases from both sides of the fin towards the center; the wave height is a fixed value of 0.76 mm. , These represent the widths of the outer and inner waves, respectively. The wave width reduction factor is 1.03. <1.06. In this embodiment, the wave width sequence from the left edge of the fin towards the center: the outermost wave width ; towards the middle are successively , , , , Minimum wave width in the middle The width difference between adjacent fins is 0.05 mm, and the distribution gradually decreases. The distribution of the wavy perforated microchannels on the right side of the fin is completely symmetrical to that on the left side, that is, from the right edge to the middle, the width also gradually decreases from 1.45 mm to 1.15 mm.

[0020] When air enters, it reaches the fin assembly from the inlet area 10 and then enters the fin substrate 60. The provided window section (i.e., the position corresponding to the window on the fin substrate 60) can change the airflow direction and interrupt the formation of a thermal boundary layer on the side of the fin substrate 60. Moreover, due to the turbulence effect of the window section, the thickness of the thermal boundary layer on the fin substrate 60 is greatly reduced, thereby enhancing the heat dissipation effect of the fins. In addition, the provided butterfly-scale serrated edge 84 can make the air flow into a turbulent state. At the same time, a gap for air diversion is formed between the inclined fin body 80 and the fin substrate 60. This gap, together with the fractal hollow microchannel 90 and the wave hollow microchannel 100, forms a ventilation gap for air diversion, allowing some air to flow to the outside through the ventilation gap for heat exchange. The fractal perforated microchannel 90 and the wave perforated microchannel 100 can divert and guide the airflow, generating disturbances and further enhancing the turbulence of the airflow. The two work together to continuously disrupt the low-speed laminar boundary layer that was originally close to the fin surface, disturbing the stable laminar flow state of the airflow and forming multi-scale turbulence and eddies in the microchannel. This continuously washes over the heat exchange surface of the fin, significantly reducing the air-side thermal boundary layer and lowering the air thermal resistance, thereby enhancing the heat exchange efficiency of the fin assembly and improving the heat dissipation effect.

[0021] The fractal perforated microchannel 90 includes a primary main channel 91, secondary branch channels 92, and an end turbulence branch 93. The lengths of the primary main channel 91, secondary branch channels 92, and end turbulence branch 93 decrease sequentially. The primary main channel 91 is the main air turbulence and heat exchange area. The width of the primary main channel 91 is B1=0.25mm, and the length is S1=11mm. It is a single-segment through-flow channel symmetrically arranged along the central axis of the fin. A secondary branch channel 92 is provided at both ends of the primary main channel 91. The width of the secondary branch channel 92 is B2=0.25mm, and the length is S2=5.25mm. The primary main channel 91 and... The middle of the secondary branch channel 92 is connected, and the two secondary branch channels 92 are symmetrically distributed and smoothly connected to the central main channel, forming a two-level hierarchical structure. Both ends of the secondary branch channel 92 are connected with terminal turbulence branches 93, and two inclined terminal turbulence branches 93 are provided on both sides of each end of the secondary branch channel 92. The angle α between the terminal turbulence branches 93 and the secondary branch channel 92 is 30°. The width of the terminal turbulence branches 93 is 0.25 mm and the length is 0.3 mm. The terminal turbulence branches 93 are equidistantly distributed along the side wall of the secondary branch channel 92 to enhance the airflow boundary layer disturbance and improve the local heat exchange efficiency.

[0022] The fractal perforated microchannels 90 on the upper butterfly-scale fin 81 and the wavy perforated microchannels 100 on the lower butterfly-scale fin 82, while increasing the heat dissipation area in contact with air, also have different obstructive effects on airflow, making airflow turbulence more uniform and avoiding local flow dead zones. This enhances the turbulence phenomenon in the channel 20, thereby effectively accelerating heat exchange efficiency. The upper butterfly-scale fin 81 and the lower butterfly-scale fin 82, with the same fin volume, significantly increase the effective heat exchange area, making airflow more orderly, the fin temperature distribution more uniform, and reducing thermal stress concentration. The laminar flow near the fin assembly is transformed into turbulent flow by the fin substrate 60. Subsequently, the turbulent flow is gradually widened by the influence of the butterfly-shaped serrated edge 84, the fractal hollow microchannel 90, and the wave hollow microchannel 100 (double-layer fractal microchannel). When the flow velocity is sufficient, the fluid will form a disordered flow, which is beneficial for heat transfer or full mixing.

[0023] This embodiment also provides a method for preparing a fin assembly, used to prepare the fin assembly of the biomimetic double-layer fractal microchannel heat sink as described above, comprising the following steps: Step 1: The fin substrate 60 is prepared using a traditional stamping process to achieve multi-batch production of large-scale frame structures and main channels; Step 2: Based on the parameters of each structure in the inclined scale body 80, a 3D model of the inclined scale body 80 is constructed using 3D modeling software (Solidworks). The butterfly-scale serrated edge 84, fractal hollow microchannel 90, and wave hollow microchannel 100 in the 3D model are optimized for precision to ensure that the inner wall of the microchannel is smooth and the serrated contour is regular. The optimized 3D model is then imported into additive manufacturing equipment and integrally formed using selective laser melting (SLM) process. After forming, the inclined scale body 80 is simply cleaned to remove residual powder. No additional machining, polishing, or other subsequent processing is required. The additive manufacturing process can achieve high-precision forming of the above-mentioned micro-complex structures, ensuring structural integrity and dimensional accuracy. Step 3: Weld two sets of inclined scales on both sides of each fin substrate 60. The two sets of inclined scales on the same side are symmetrically distributed to obtain a fin group.

[0024] In step 2, when using the laser selective melting (SLM) process for integral molding, 6061 aluminum alloy powder is selected as the molding material. The powder particle size is 15-53μm, and the molding layer thickness is controlled to be 0.02mm. This can achieve the structural molding requirements of double-layer fractal microchannels and butterfly-scale serrated edges 84, ensuring that the inner wall of the channel is smooth and defect-free, and the serrated contour is regular.

[0025] The inclined fin body 80 is integrally formed using additive manufacturing, breaking through the limitations of traditional stamping on fin structures. It allows for the design of butterfly-shaped serrated edges 84, fractal hollow microchannels 90, and wave-shaped hollow microchannels 100 according to actual heat exchange requirements, without being limited by mold forming processes. The fin substrate 60 is formed using traditional stamping processes, enabling the mass production of large-scale frame structures and main channels. The inclined fin body 80 and the fin substrate 60 are rigidly connected through welding, achieving optimized and improved fin structure.

[0026] In summary, the butterfly-scale-like flakes of this invention (upper butterfly-scale-like flakes 81 and lower butterfly-scale-like flakes 82) combine the structural features of butterfly scales found in nature, exhibiting a butterfly-scale-shaped serrated edge at the tip. This feature can create flow separation, disrupt the air boundary layer, increase heat transfer capacity, enhance turbulence and local fluid medium scouring, reduce fluid impurity adhesion and deposition, and improve the long-term operational stability of the radiator. By customizing the tip size of the butterfly-scale-shaped serrated edge using additive manufacturing technology, problems such as the difficulty of one-piece molding, the difficulty in processing complex structures, and low material utilization rates inherent in traditional processing methods can be avoided.

[0027] The butterfly-scale-like microchannels of this invention are complete, enhancing heat transfer efficiency. The double-layer fractal microchannels are closed cavities (the cavity is circumferentially closed, meaning the microchannel cross-sectional outline is closed and has no openings), ensuring fluid flow within the closed channels without leakage. The heat dissipation walls are continuous and complete, avoiding problems such as fluid side leakage and boundary layer disorder compared to surface grooved or protruding channels, significantly improving internal convective heat transfer efficiency. The inclined scale body has no grooves or gaps on its 80° surface, exhibiting strong overall continuity. This ensures lightweight design while improving the structural rigidity and deformation resistance of the inclined scales. The closed cavity of the double-layer fractal microchannels eliminates the risk of fluid leakage, making it suitable for high-pressure, high-flow-rate automotive radiator conditions. The double-layer fractal microchannels greatly increase the heat dissipation area of ​​the fluid medium, and the orderly flow of the internal fluid medium avoids local flow obstruction, resulting in more uniform fin temperature distribution and lower thermal stress. The double-layer fractal microchannels on the butterfly-scale-like fins enhance fluid-side heat transfer and improve turbulence. Working in synergy with the butterfly-scale serrated edges and the heat transfer mechanism, they achieve layered, multi-stage turbulence, significantly improving the overall heat transfer performance of the fin assembly. Additive manufacturing of the double-layer fractal microchannel structure overcomes traditional process limitations, eliminates assembly-type contact thermal resistance, and further increases heat transfer performance.

[0028] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A biomimetic double-layer fractal microchannel radiator, comprising a fin assembly fixed on a coolant flow channel, characterized in that, The fin assembly includes multiple wavy fin substrates (60). Windows are provided on both sides of each fin substrate (60). Two sets of symmetrically arranged inclined scales are fixedly installed within each window. Each set of inclined scales includes multiple inclined scale bodies (80). Each inclined scale body (80) includes an upper layer of butterfly-like scales (81) and a lower layer of butterfly-like scales (82) connected by a hexahedral connecting post (83). The upper layer of butterfly-like scales (81...) Both the upper butterfly scale (81) and the lower butterfly scale (82) have butterfly scale-shaped serrated edges (84) on their tops. The width of the multiple serrations in the butterfly scale-shaped serrated edges (84) gradually increases from the sides to the middle. The upper butterfly scale (81) has fractal hollow microchannels (90) and the lower butterfly scale (82) has two symmetrically distributed wave hollow microchannels (100). The width of the multiple waves in the wave hollow microchannels (100) gradually decreases from the sides to the middle.

2. The biomimetic double-layer fractal microchannel heat sink according to claim 1, characterized in that, The fractal hollow microchannel (90) includes a primary main channel (91), a secondary branch channel (92) and an end turbulence branch (93). A secondary branch channel (92) is provided at both ends of the primary main channel (91). The primary main channel (91) and the secondary branch channel (92) are connected in the middle. Multiple inclined end turbulence branches (93) are provided at both ends of the secondary branch channel (92).

3. The biomimetic double-layer fractal microchannel heat sink according to claim 2, characterized in that, The angle between the terminal turbulence branch (93) and the secondary branch channel (92) is 30°.

4. A biomimetic double-layer fractal microchannel heat sink according to claim 3, characterized in that, The lengths of the primary main channel (91), the secondary tributary channel (92), and the terminal turbulence branch (93) decrease sequentially.

5. A method for preparing a fin assembly, used to prepare the fin assembly of the biomimetic double-layer fractal microchannel heat sink as described in claim 4, characterized in that, Includes the following steps: Step 1: The fin substrate (60) is prepared by stamping process to realize the preparation of large-scale frame structure; Step 2: Construct a three-dimensional model of the inclined scale body (80) using three-dimensional modeling software, and optimize the precision of the butterfly-shaped sawtooth edge (84), fractal hollow microchannel (90), and wave hollow microchannel (100) in the three-dimensional model. Then, import the optimized three-dimensional model into the additive manufacturing equipment and use the laser selective melting (SLM) process to integrally form the model. After forming, clean the surface of the inclined scale body (80) to remove residual powder. Step 3: Weld two sets of inclined scales on both sides of each fin substrate (60). The two sets of inclined scales on the same side are symmetrically distributed to obtain a fin group.

6. The method for preparing a fin assembly according to claim 5, characterized in that, In step 2, when using the laser selective melting (SLM) process for integral molding, 6061 aluminum alloy powder is selected as the molding material, with a powder particle size of 15-53 μm and the molding layer thickness is controlled to be 0.02 mm.

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