Micro-channel flow boiling enhanced heat transfer device based on bionic structure

Abstract

The invention discloses a micro-channel flow boiling enhanced heat transfer device based on a bionic structure. The device comprises a micro-channel structure base body, a channel inner surface wettability regulation and control layer, a working medium inlet and a working medium outlet. A bionic structure microchannel is arranged in the microchannel structure base body, the inner wall of the microchannel structure base body is provided with a micron-scale or nanometer-scale texture structure, the bionic structure microchannel is composed of a main channel and branch channels of at least three levels of fractal hierarchical structures, the width ratio of the branch channels is 1: 0.2-0.5, and the length range of the branch channels is 2-10 mm. And the contact angle gradient of the wettability regulation and control layer on the inner surface of the channel is 5-120 degrees. The tail end of each branch channel is provided with a bubble capturing groove with the diameter of 5-10 mm and the depth of 5 mm. The device can improve the boiling heat transfer coefficient, reduce the flow resistance and improve the bubble generation and desorption process, and is suitable for the fields of heat dissipation of high-heat-flux electronic equipment, aerospace heat management, chemical reaction and the like.

Description

Technical Field

[0001] The invention relates to the technical field of engineering heat and mass transfer, and in particular to a microchannel flow boiling enhanced heat transfer device based on a bionic structure. Background Art

[0002] With the development of microelectronic devices, high-power lasers and high-performance equipment, the heat flux density per unit area of ​​chips and electronic devices has increased dramatically, and their local hot spots and heat dissipation problems have become increasingly prominent. Traditional single-channel or simple-configuration microchannels often have shortcomings such as uneven fluid distribution and obvious local hot spots during flow boiling; large flow resistance and high energy consumption; unsatisfactory bubble formation and detachment processes, which affect heat transfer efficiency.

[0003] However, there are highly optimized fluid transport systems in nature, such as plant leaf veins and animal vascular networks. These bionic structures have excellent performance in fluid distribution, low resistance flow and material transfer, providing important inspiration for solving the difficult problems of microchannel flow boiling heat and mass transfer. Therefore, how to introduce bionic principles into the design of flow boiling in microchannels to achieve high heat transfer efficiency and low energy consumption operation is an urgent problem to be solved. Summary of the invention

[0004] The present invention aims to provide a microchannel flow boiling enhanced heat transfer device based on a bionic structure, which utilizes the excellent diversion characteristics of fractal or tree-like networks in biological systems to achieve uniform distribution of fluids; increases boiling nucleation sites through wall micron or nano textures to make bubbles easier to generate and detach; reduces flow resistance in the channel and improves the overall boiling heat transfer efficiency, thereby realizing the design of an efficient thermal management system.

[0005] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a microchannel flow boiling enhanced heat transfer device based on a bionic structure, comprising a microchannel structure matrix, a channel inner surface wettability regulating layer, a working fluid inlet and a working fluid outlet, wherein the microchannel structure matrix is ​​provided with a plurality of bionic structure microchannels, the inner wall of the bionic structure microchannel has a micrometer or nanometer texture structure, the bionic structure microchannel comprises a main channel, the main channel is connected with a plurality of branch channels of a fractal hierarchical structure, the fractal hierarchical structure comprises at least 3 levels of branches, the channel width ratio of the branch to the next level branch is 1:0.2~0.5, the length range is 2mm~10mm, the channel inner surface wettability regulating layer is a gradient wettability surface, and the contact angle gradient variation range is 5°~120°.

[0006] Specifically, the material of the microchannel structure matrix is ​​copper, aluminum alloy or composite material.

[0007] Specifically, the wettability regulating layer on the inner surface of the channel is realized by chemical vapor deposition or nano-coating technology.

[0008] Specifically, the channel angles of the branches at adjacent levels are 30° to 90°, and the ratio of the channel lengths of the branches at adjacent levels is 0.1 to 0.3.

[0009] Specifically, a bubble capturing groove is provided at the end of the branch channel, and the bubble capturing groove has a diameter of 5 to 10 mm and a depth of 5 mm.

[0010] Specifically, the bionic structure microchannel is manufactured by using 3D printing or micromachining technology and is prepared using materials with high thermal conductivity.

[0011] The principle and beneficial effects of this technical solution:

[0012] (1) Bionic geometric structure design: The microchannel structure adopts a fractal, tree-like network design similar to the veins of plant leaves or the vascular system of animals, including a main channel and several branch channels. Such biological systems have developed a nearly perfect material transfer mechanism after a long evolution process. The main channel is used to introduce fluid, and the branch channels evenly distribute the fluid to each working area, and the fluid outlet is set at an appropriate position. The microchannel in the present invention consists of a main channel and at least three-level fractal hierarchical branch channels. This multi-level branch structure increases the heat exchange area exponentially, while the increase in material volume is relatively limited. Specifically, when the main channel extends to the third-level branch, the effective heat exchange area can be increased by 2.5 to 4 times, while the occupied space is only increased by about 30%. This significant increase in area provides more sufficient interface contact for boiling heat transfer, so that the contact between the liquid working medium and the heating surface is more sufficient. In addition, in traditional microchannels, a higher flow pressure loss is generated when the fluid flows, and a larger pump power is required to maintain the flow, which not only increases the energy consumption of the system, but also limits the flow rate, thereby limiting the heat transfer performance. The fractal structure of the present invention makes the distribution of fluid in the multi-level branch structure more uniform by precisely controlling the width ratio of each level of branch channels, thereby reducing the resistance loss caused by local high-speed flow. Compared with the traditional channel structure, the fractal channel structure of the present invention can reduce the flow resistance by 20% to 40%.

[0013] (2) Micro / nano texture on the wall: Micro-machining or 3D printing technology is used to construct micro / nano texture structures on the inner wall of the microchannel to imitate the surface structure of nature, thereby increasing local boiling nucleation sites, promoting the generation and rapid desorption of bubbles, and accelerating the flow boiling process. The inner wall of a traditional microchannel is usually relatively smooth and lacks effective nucleation sites, which significantly limits the heat transfer efficiency in the initial stage of boiling. The core mechanism of boiling heat transfer is the generation, growth and detachment of bubbles, among which bubble nucleation is the starting point and key link of the entire boiling process. The micro-nano texture structure of the wall forms many tiny depressions, holes and grooves, whose sizes range from hundreds of nanometers to tens of micrometers. When the temperature of the heating surface increases, the temperature of the fluid in these tiny depressions will reach an overheated state more easily than the surrounding fluid, thereby preferentially forming a vapor core. The special geometric shape of the micro-nano texture can also effectively capture and stabilize tiny bubbles, providing ideal conditions for bubble nucleation.

[0014] (3) Materials and manufacturing technology: Microchannel structures can be made of high thermal conductivity materials (such as copper, aluminum alloys and composite materials). Modern 3D printing or micro-nano processing technology is used to accurately manufacture the pre-designed bionic structure to ensure that the fine structure is not distorted, so as to achieve the designed optimized heat transfer and flow effects.

[0015] (4) Overall optimization: During the design, the angle, diameter and bending radius between the main channel and the branch channel are optimized to reduce the liquid flow resistance and ensure that the system can still work stably under high load. At the same time, the design parameters are tuned through Fluent software numerical simulation and experimental verification to achieve the best heat transfer and flow performance.

[0016] In summary, the design of the flow boiling bionic structure in the microchannel of the present invention can significantly improve the heat transfer coefficient, and the heat transfer efficiency can be increased by more than 20% to 30% under the same heat load; reduce the fluid flow resistance, save energy and reduce emissions, and reduce pumping energy consumption by about 15%; improve the bubble generation and desorption process, avoid local overheating, and achieve a uniform and stable boiling process; the preparation process is simple, suitable for large-scale production, and can be flexibly applied to various fields such as heat dissipation of high heat flux density electronic equipment, thermal management of aerospace platforms, and chemical reactions. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a structural schematic diagram of the present invention;

[0018] In the figure: 1. microchannel structure matrix; 2. main channel; 3. branch channel; 4. working fluid inlet; 5. working fluid outlet. DETAILED DESCRIPTION

[0019] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments:

[0020] A microchannel flow boiling enhanced heat transfer device based on bionic structure

[0021] 1. Device composition

[0022] like Figure 1 As shown, the heat transfer device of the present invention mainly includes a microchannel structural matrix, a wettability regulating layer on the inner surface of the channel, a working fluid inlet and a working fluid outlet. The microchannel structural matrix is ​​the core part of the entire device, and a number of bionic structure microchannels are arranged inside it. The inner walls of these microchannels have a micron or nanometer texture structure, and their main function is to enhance the nucleation site of the bubble, thereby promoting the generation and rapid desorption of the bubble. This design is inspired by the efficient heat transfer and fluid transport mechanism of organisms in nature. By imitating these characteristics, the device can significantly improve the heat transfer efficiency.

[0023] 2. Microchannel design

[0024] The network structure of the bionic microchannel mimics the fractal hierarchical distribution of the veins of plant leaves or the vascular system of animals. This design can achieve uniform distribution of fluid and optimize heat transfer performance. Specifically, the bionic microchannel consists of a main channel and several branch channels with a fractal hierarchical structure, and the fractal hierarchical structure contains at least three levels of branches. The design of this multi-level branching structure is inspired by highly optimized fluid transport systems in nature, such as the veins of plant leaves and the vascular network of animals.

[0025] In the present invention, the main channel is used to introduce the fluid, while the branch channel evenly distributes the fluid to each working area, and the fluid outlet is set at a suitable position. Through this design, the heat exchange area increases geometrically, while the increase in material volume is relatively limited. Specifically, when the main channel extends to the third-level branch, the effective heat exchange area can be increased by 2.5 to 4 times, while the occupied space only increases by about 30%. This significant increase in area provides more sufficient interface contact for boiling heat transfer, allowing the liquid working medium to contact the heating surface more fully.

[0026] In addition, the channel width ratio of the branch to the next branch is 1:0.2-0.5, and the channel length ranges from 2 to 10 mm. This precise geometric proportion design can ensure that the fluid is distributed more evenly in the multi-level branch structure and reduce the resistance loss caused by local high-speed flow. Compared with the traditional channel structure, the fractal channel structure of the present invention can reduce the flow resistance by 20% to 40%.

[0027] 3. Surface wettability regulation

[0028] In order to further optimize the heat transfer performance, the present invention sets a gradient wettability regulating layer on the microchannel surface. The contact angle of this layer transitions from the super-hydrophilic region (contact angle 5°) to the hydrophobic region (contact angle 120°) along the flow direction of the working fluid. The design inspiration of this gradient wettability surface comes from the wettability changes of the surface of organisms in nature, such as the super-hydrophobic properties of the lotus leaf surface and the gradient wettability of some insect wings. Through this design, bubbles can move more efficiently during the generation and desorption process, thereby further improving the heat transfer efficiency.

[0029] Gradient wettability surfaces can be achieved by chemical vapor deposition or nano-coating technology. These technologies can precisely control the chemical composition and microstructure of the surface to achieve the desired wettability gradient. For example, chemical vapor deposition can deposit a thin film with specific chemical properties on the surface of the microchannel, while nano-coating technology can form a coating with a nano-scale structure on the surface. The application of these technologies can not only achieve the design requirements of the gradient wettability surface, but also ensure the durability and stability of the surface.

[0030] 4. Microchannel structure matrix material

[0031] In order to ensure efficient heat conduction, the microchannel structure matrix material of the present invention uses high thermal conductivity materials such as copper, aluminum alloy or composite materials. These materials have excellent thermal conductivity and can quickly transfer heat from the heat source to the fluid in the microchannel. For example, the thermal conductivity of copper is about 400W / (m·K), the thermal conductivity of aluminum alloy is about 200W / (m·K), and some composite materials can further improve thermal conductivity by optimizing their microstructure and composition.

[0032] In addition, these materials also have good mechanical properties and processing properties, which can meet the manufacturing requirements of microchannel structures. For example, copper and aluminum alloys can be precisely processed by traditional mechanical processing or modern micromachining technology, while composite materials can achieve complex structural design through 3D printing technology. The selection of these materials can not only meet the requirements of heat transfer performance, but also ensure the structural strength and reliability of the device.

[0033] 5. Branch channel design details

[0034] In the design of the branch channel, the angle between adjacent layers of branch channels is 30° to 90°, and the ratio of the length of adjacent layers of branch channels is 0.1 to 0.3. This design can ensure that the fluid flows more smoothly in the branch channel and reduce the flow resistance. In addition, a bubble capture groove with a diameter of 5 to 10 mm and a depth of 5 mm is provided at the end of the branch channel. The design of these bubble capture grooves is inspired by the microstructure of the surface of organisms in nature, such as the micro grooves on the surface of some plant leaves. These grooves can effectively capture and stabilize tiny bubbles, providing ideal conditions for the nucleation of bubbles.

[0035] By optimizing the design of the branch channel, the present invention can further improve the generation and desorption process of bubbles. In traditional microchannels, the generation and desorption of bubbles are often restricted, resulting in low heat transfer efficiency. However, by providing bubble capture grooves, the present invention can effectively promote the generation and rapid desorption of bubbles, thereby achieving local efficient heat transfer.

[0036] 6. Manufacturing process

[0037] The bionic structure microchannel of the present invention is manufactured by 3D printing or micromachining technology. These technologies can ensure high-precision structural realization and can flexibly manufacture complex geometric shapes. For example, 3D printing technology can accurately construct the fractal structure and surface texture of the microchannel by depositing materials layer by layer. Micromachining technology can realize high-precision manufacturing of microchannels through processes such as photolithography and etching.

[0038] During the manufacturing process, high thermal conductivity materials are selected to reduce fluid flow resistance and improve boiling heat transfer. For example, through laser micromachining or chemical etching processes, micro-concave and convex textures similar to leaf veins can be formed on the inner wall of the microchannel. These microstructures can not only increase the nucleation sites of bubbles, but also further optimize the heat transfer performance.

[0039] In addition, the flexibility of the manufacturing process can also meet the needs of different application scenarios. For example, for the heat dissipation of high heat flux density electronic equipment, a miniaturized microchannel design can be used; while for aerospace thermal management devices, a larger microchannel structure can be used. This flexibility enables the present invention to be widely used in multiple fields.

[0040] Example:

[0041] In this embodiment, a bionic tree-like microchannel design is adopted. The main channel is used as the fluid inlet. After the fluid is introduced from the left side, it is evenly distributed to the entire heat exchange area through multi-level branch channels. Each branch channel extends in a smooth curve to avoid sharp turns, thereby reducing flow resistance. The width of the main channel is 200μm, the width of the secondary branch is 80μm, and the depth is 300μm.

[0042] On the wall of each channel, micro-concave and convex textures similar to leaf veins are formed by laser micromachining or chemical etching. These microstructures can serve as boiling nucleation sites, promoting the rapid generation and desorption of bubbles in the channel, thereby achieving local efficient heat transfer. The super-hydrophilic surface (contact angle 5°) is formed at the inlet section by plasma treatment, and the outlet section is modified with a fluorinated carbon coating to achieve hydrophobicity (contact angle 110°).

[0043] Finally, deionized water was used as the working fluid at a heat flux of 10 kW / cm 2 The test results show that the heat transfer coefficient can be increased by 30% to 40% and the pressure drop can be reduced by 20% to 30% compared with the traditional channel. This result fully proves the significant advantages of the present invention in terms of heat transfer performance and energy saving effect.

[0044] Application prospects

[0045] The microchannel flow boiling enhanced heat transfer device based on the bionic structure of the present invention has a wide range of application prospects. It can not only be used for heat dissipation of high heat flux density electronic equipment, but also can be applied to aerospace thermal management devices, precision chemical reactions and other fields. For example, in the heat dissipation of electronic equipment, the present invention can effectively solve the local hot spot problem of chips and electronic devices, and improve the reliability and service life of the equipment; in the field of aerospace, the present invention can achieve efficient thermal management, reduce system weight, and improve flight performance; in chemical reactions, the present invention can optimize reaction conditions and improve reaction efficiency.

[0046] In addition, the manufacturing process of the present invention is simple and suitable for large-scale production. By optimizing the design parameters and manufacturing process, the present invention can further improve the heat transfer performance and energy saving effect. In the future, with the continuous development of material science and manufacturing technology, the present invention is expected to be applied in more fields and provide new ideas and methods for solving heat transfer problems.

[0047] In summary, the microchannel flow boiling enhanced heat transfer device based on bionic structure of the present invention achieves efficient heat transfer and energy saving effects through innovative design and manufacturing process. It not only has significant technical advantages, but also has broad application prospects, providing a new direction for the development of heat transfer technology.

[0048] The above is only an embodiment of the present invention, and the common knowledge such as the known specific technical solutions or characteristics in the solution is not described in detail here. For those skilled in the art, without departing from the technical solution of the present invention, several modifications and improvements can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A microchannel flow boiling enhanced heat transfer device based on a bionic structure, characterized by: The invention comprises a microchannel structure matrix, a channel inner surface wettability regulating layer, a working fluid inlet and a working fluid outlet, wherein the microchannel structure matrix is ​​provided with a plurality of bionic structure microchannels, the inner wall of the bionic structure microchannel has a micrometer or nanometer texture structure, the bionic structure microchannel comprises a main channel, the main channel is connected with a plurality of branch channels of a fractal hierarchical structure, the fractal hierarchical structure comprises at least 3 levels of branches, the channel width ratio of the branch to the next level branch is 1:0.2-0.5, the length range is 2mm-10mm, the channel inner surface wettability regulating layer is a gradient wettability surface, and the contact angle gradient variation range is 5°-120°.

2. The microchannel flow boiling enhanced heat transfer device based on a bionic structure according to claim 1, characterized in that: The material of the microchannel structure matrix is ​​copper, aluminum alloy or composite material.

3. The microchannel flow boiling enhanced heat transfer device based on a bionic structure according to claim 1, characterized in that: The wettability regulating layer on the inner surface of the channel is realized by chemical vapor deposition or nano-coating technology.

4. The microchannel flow boiling enhanced heat transfer device based on a bionic structure according to claim 1, characterized in that: The channel angles of the branches at adjacent levels are 30° to 90°, and the ratio of the channel lengths of the branches at adjacent levels is 0.1 to 0.

3.

5. The microchannel flow boiling enhanced heat transfer device based on a bionic structure according to claim 1, characterized in that: A bubble capturing groove is provided at the end of the branch channel, and the bubble capturing groove has a diameter of 5 to 10 mm and a depth of 5 mm.

6. The microchannel flow boiling enhanced heat transfer device based on a bionic structure according to claim 1, characterized in that: The bionic structure microchannel is manufactured by using 3D printing or micromachining technology and is prepared using high thermal conductivity materials.

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