Biomimetic microchannel heat sink

Abstract

The application discloses a kind of bionic microchannel heat sink, including working medium inlet, inlet flow equalization buffer tank, first microchannel structure, second microchannel structure, outlet header tank and working medium outlet;The first microchannel structure is ladder microchannel structure, including the microcolumn array being arranged below high heat flux density point heat source, the microchannel structure of first low heat flux density area and the imitation bicuspid structure, the microchannel structure is located in microcolumn array both sides, the second microchannel structure is located in the second low heat flux density area between two first microchannel structures;Each microchannel has the same height and height, and is symmetrically distributed along the heat sink center line.The microchannel structure of the application is optimized and designed, improves the liquid film spreading process three-phase line movement, liquid film thickness and other gas-liquid two-phase evolution behaviors in microchannel, effectively reduces the working medium flow resistance, and improves the heat performance of microchannel heat sink under high heat flux density condition.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of micro-channel two-phase flow boiling heat transfer, and particularly relates to a micro-channel heat sink structure for non-uniformly distributed point heat sources. BACKGROUND

[0002] With the rapid development of modern electronic technology towards high power density and high integration, the local heat flux of electronic components is even higher than 1000W / cm 2 However, traditional cooling methods such as air cooling and single-phase liquid cooling cannot meet the high-level heat dissipation requirements, and micro-channel heat sinks have gradually become the preferred components for high-efficiency and reliable thermal management of electronic devices due to their compact structure, large heat transfer area, and significant advantages such as strong heat transfer performance, good temperature uniformity, and high heat transfer limit.

[0003] Among the existing micro-channel heat sink structures, parallel micro-channels have been widely used in various micro-scale thermal management systems due to their simple design and easy processing. However, traditional parallel micro-channels usually adopt an equal-interval and same-size channel layout method, which can easily cause a series of heat flow and flow mismatching problems during actual two-phase flow. Especially under gas-liquid two-phase working conditions, due to uneven pressure loss and gas-liquid distribution among channels, gas blockage and backflow phenomena are easily formed in the middle and rear sections of the micro-channels, which aggravates the instability of the fluid phase interface and even leads to local dryout, seriously affecting the heat transfer performance and system reliability. In addition, in actual engineering applications, such as high-integration electronic chips and power devices, the heat dissipation objects often exhibit non-uniform and arrayed heat source distribution characteristics. Under the background of such non-uniform heat load, the traditional parallel micro-channel structure is difficult to perform targeted strengthening cooling according to the heat source position, which can easily cause problems such as local hot spots that cannot be effectively cooled and low energy utilization efficiency, and has limited ability to cope with multiple high heat flux regions. Therefore, it is urgent to develop a micro-channel heat sink structure with stronger adaptability, higher local heat transfer efficiency, and better flow stability to meet the fine thermal management needs of non-uniform high heat flux devices in complex thermal environments. SUMMARY

[0004] The technical problem to be solved by the present application is to provide a bionic stepped micro-channel heat sink structure that can match the heat source distribution and improve the local heat dissipation capacity for high heat flux regions.

[0005] To solve the above technical problems, the technical solution adopted by the present application is:

[0006] A kind of bionic microchannel heat sink, including working medium inlet, inlet flow uniformity buffer tank, first microchannel structure, second microchannel structure, outlet header tank and working medium outlet, working medium flows into inlet flow uniformity buffer tank from working medium inlet and enters first microchannel structure and second microchannel structure respectively, flows to outlet header tank after absorbing wall heat by latent heat and sensible heat of working medium, and finally flows out from working medium outlet;The first microchannel structure is a stepped microchannel structure, including microcolumn array arranged below high heat flux density point heat source, microchannel structure of first low heat flux density area and bionic mitral valve structure, the microchannel structure is located on both sides of microcolumn array, the microchannel structure is made of several parallel microchannels, the bionic mitral valve structure is located in the connecting area of the microchannel and microcolumn array;The second microchannel structure is located in the second low heat flux density area between two first microchannel structures, and the second microchannel structure is made of at least one microchannel;Each microchannel has the same height and height, and is symmetrically distributed along the center line of the heat sink.

[0007] The stepped microchannel is arranged differently according to the hot spot distribution characteristics on the device, including microchannel array arranged below high heat flux density point heat source, single channel structure of low heat flux density area and bionic mitral valve structure of channel bifurcation or confluence area, which can effectively guide flow and suppress flow instability. All microchannels have the same height and width, and are symmetrically arranged along the center line of the heat sink structure to optimize the overall fluid path and temperature field distribution.

[0008] The stepped microchannel uses diamond as the base material, which has excellent thermal conductivity and structural stability. Its surface is constructed by drop casting deposition and inductively coupled plasma etching (ICP-RIE) process to form a micro-nano structure interface layer with bionic function, further improving the wetting performance and heat exchange efficiency in microscale gas-liquid phase change process.

[0009] A method for preparing a bionic micro-nano structure surface structure of a microchannel heat sink includes the following steps:

[0010] S1. Microchannel processing and nanoparticle deposition: a microchannel structure is formed on the surface of a diamond substrate by laser cutting method;Then, nano gold particles are deposited on the inner wall of the microchannel groove by drop casting method, which serves as the mask template for subsequent plasma etching.

[0011] S2. Inductively coupled plasma etching to construct nanowire array structure: the diamond surface is etched by inductively coupled plasma etching (ICP-RIE) to form a biomimetic nanowire array. The geometric parameters such as the spacing and length of the nanowire can be precisely controlled by adjusting the process parameters such as power density, reaction chamber pressure, temperature, gas ratio and flow rate during etching. The structural morphology (such as cylindrical, conical or circular truncated cone) of the nanowire can be customized by changing the material (such as SiO2, Al2O3) of the nanoparticle mask plate.

[0012] S3. Microstructure reconstruction and functional surface formation: after completing the nanowire array etching, the micro-gap structure is processed in the array area by using precise laser cutting technology, and the residual mask plate material on the surface is removed, to obtain a micro-nano functional surface with multi-scale biomimetic characteristics.

[0013] S4. Surface metallization and device integration: the constructed diamond microchannel structure and cover plate are respectively subjected to surface metallization treatment, and a gold layer is deposited as a bonding layer by using a magnetron sputtering method. Then, device packaging bonding is realized by using gold-tin solder, and a high-thermal-conductivity and high-strength diamond-based microchannel heat sink structure is constructed.

[0014] The working medium adopts low-boiling-point working medium HFE7100 or refrigerant R134a or R1233zd.

[0015] Compared with the prior art, the present application has the following beneficial effects:

[0016] 1. The biomimetic stepped microchannel heat sink structure proposed in the present application is designed and arranged differently in the microchannel area according to the spatial distribution characteristics of the non-uniform heat source, a plurality of parallel microchannels (microchannel structure of the first microchannel structure) are arranged in the high heat flux density area, and a plurality of small channels (second microchannel structure) are arranged in the low heat flux density area, so that the cooling capacity and the heat source power density are accurately matched, thereby significantly improving the local heat dissipation capacity and reducing the risk of local overheating, and the present application has higher adaptability and uniformity compared with the traditional parallel microchannel structure.

[0017] 2. The present application constructs a biomimetic micro-nano structure on the surface of the microchannel, which is prepared by using drop casting and depositing nanoparticles and inductively coupled plasma etching (ICP-RIE) technology. By adjusting the size and spacing of the nanowire array, the micro-nano level crack is used to significantly enhance the suction force on the liquid working medium, effectively enhance the wettability of the microchannel surface, thereby improving the liquid film spreading speed, inhibiting bubble aggregation, significantly improving the micro-scale gas-liquid two-phase flow evolution behavior, and improving the heat sink heat transfer limit.

[0018] 3、The present application further designs to introduce the bicuspid structure in the channel change area, guides the fluid flow direction, effectively suppresses the backflow and cross counterflow phenomenon, thereby suppressing the boiling two-phase flow instability.

[0019] 4、The microchannel adopts diamond as the base material, has excellent heat diffusion performance and structural strength, is suitable for the heat dissipation demand of various typical high heat flow density devices such as electronic chips, lasers and power devices, and has good process compatibility and integration capacity. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 It is the whole structure schematic diagram of the embodiment of the present application;

[0021] Figure 2 It is the distribution top view of the stepped microchannel of the embodiment of the present application;

[0022] Figure 3 It is the schematic diagram of the bionic micro-nano structure functional surface of the embodiment of the present application;

[0023] Figure 4 It is the schematic diagram of the microcolumn array structure of the embodiment of the present application;

[0024] Figure 5 It is the schematic diagram of the bicuspid structure of the embodiment of the present application;

[0025] Figure 6 It is the preparation process flow of the bionic micro-nano structure functional surface of the microchannel heat sink of the embodiment of the present application;

[0026] Figure 7 It is the schematic diagram of the bionic micro-nano multi-scale structure surface of the embodiment of the present application;

[0027] Figure 8 It is the local enlarged view of the nano array and the micro gap of the bionic micro-nano multi-scale structure surface of the embodiment of the present application;

[0028] Figure 9 It is the boiling bionic strengthening mechanism analysis of the low dryness area of the bionic micro-nano multi-scale structure surface of the embodiment of the present application;

[0029] Figure 10 It is the boiling bionic strengthening mechanism analysis of the high dryness area of the bionic micro-nano multi-scale structure surface of the embodiment of the present application.

[0030] Wherein: 1 - working fluid inlet; 2 - inlet flow uniformity buffer tank; 3 - first microchannel structure; 4 - second microchannel structure; 5, outlet header tank; 6 - working fluid outlet; 31 - microchannel structure; 311 - nanowire array; 32 - microcolumn array; 321 - microcolumn; 33 - bicuspid valve structure. DETAILED DESCRIPTION

[0031] In order to deepen the understanding of the present application, we will make further detailed description of the present application in conjunction with the accompanying drawings, the embodiment is only used to explain the present application, and does not constitute the limitation of the scope of protection of the present application.

[0032] Figure 1 A specific embodiment of a microchannel heat sink structure is shown, including: working fluid inlet 1, inlet flow uniformity buffer tank 2, first microchannel structure 3, second microchannel structure 4, outlet header tank 5 and working fluid outlet 6. Refrigerant liquid flows from working fluid inlet 1 into inlet flow uniformity buffer tank 2, then uniformly flows into first microchannel structure 3 and second microchannel structure 4, and flows to outlet header tank 5 after absorbing wall heat through working fluid latent heat and sensible heat, and finally flows out from working fluid outlet 6. The first microchannel structure 3 is a stepped microchannel structure, including a microcolumn array 32 arranged below a high heat flux density point heat source, a microchannel structure 31 of a first low heat flux density region, and a bicuspid valve structure 33. The microchannel structure 31 is located on both sides of the microcolumn array 32, the microchannel structure 31 is composed of a plurality of parallel microchannels, and the bicuspid valve structure 33 is located at the connection region of the parallel microchannels and the microcolumn array; the second microchannel structure is located in the second low heat flux density region between the two first microchannel structures 3, and the second microchannel structure 4 is composed of at least one microchannel; each microchannel has the same height and height, and is symmetrically distributed along the center line of the heat sink.

[0033] The following is an example of 4 local heat sources with 2x2 distribution, wherein the size of a single heat source is 3mmx2mm.

[0034] Figure 2The top view of the stepped microchannel arrangement of the embodiment of the present application is shown. According to the spatial size and distribution characteristics of the heat source, a micro-pillar array 32 region with a size of 3.4 mm x 3.85 mm is arranged directly above the heat source. The micro-pillar array 32 region is composed of 25 cylindrical micro-pillars with a diameter of 400 μm and a height of 500 μm, which are uniformly arranged in a regular matrix, so as to enhance the local heat exchange area and turbulent flow characteristics, thereby improving the boiling heat transfer efficiency of the high heat flux region. Seven parallel microchannels are arranged on both sides of the heat source, each with a width of 250 μm and a depth of 500 μm, for guiding the working medium to the micro-pillar array 32 region and participating in the preliminary heat exchange process. In order to prevent the backflow problem caused by the local pressure difference when the working medium is transferred from the parallel channel to the micro-pillar region, a bicuspid valve structure 33 is designed and introduced at the tail of the parallel flow channel. The structure realizes the function of one-way rectification through asymmetric geometric arrangement, which can effectively inhibit the reverse flow of the fluid in the boiling state, thereby significantly improving the flow stability of the system and further enhancing the local heat transfer capacity. In the second low heat flux region in the middle region of the heat sink far from the heat source, three parallel microchannels with a size of 198 mm x 0.25 mm x 0.5 mm (length x width x height) are arranged in the second microchannel structure 4 to meet the cooling requirements of the low heat flux region while considering the control of the working medium pressure loss. The channel structure in this part is simple and has low flow resistance, which can meet the heat dissipation requirements under low heat flux. The bottom of the microchannel is processed with a biomimetic micro-nano structure functional surface. The overall structure adopts a zoning and stepped microchannel arrangement strategy based on the distribution characteristics of the heat source, realizing the coordinated transition of the flow and heat transfer performance from the high heat flux (micro-pillar) region to the medium and low heat flux (micro-channel) region. This structure optimization can significantly improve the spatial utilization rate and heat transfer uniformity of the working medium, while reducing the overall pressure drop and heat exchange temperature difference of the system, realizing more efficient and reliable micro-scale thermal management performance.

[0035] Figure 3 、 Figure 4 and Figure 5 respectively illustrate the key functional regions in the heat sink stepped microchannel structure adopted in the embodiment of the present application. Figure 3 The biomimetic micro-nano structure functional surface formed by the microchannel structure 31 arranged on the inner wall of the microchannel in the present application. A regular distributed nano-wire array 311 is constructed on the surface of the diamond substrate, with an array spacing of 5-10 μm, arranged in a regular square matrix. The nano-wire array 311 significantly enhances the wall wetting property and gas-liquid interface stability. The nano-wire array 311 is composed of cylindrical nano-wires with a height of 2-3 μm and a diameter of 200-300 nm, and a spacing of about 500 nm. The arrayed nano-wires can effectively improve the local liquid film spreading capacity and phase change heat transfer efficiency. Figure 4Structure diagram of micro-pillar array 32 used in the embodiment of the present application. The structure is located directly above the heat source, providing enhanced heat exchange channels for high heat flux density areas. The micro-pillar array 32 is formed by micro-pillars 321 arranged in an array, and the micro-pillars 321 have an equal-interval cylindrical shape with a diameter of 400 μm and a height of 500 μm. The overall size of the area is 3.4 mm x 3.85 mm, and the total number of micro-pillars is 25, which are evenly arranged in a 5 x 5 array, aiming to increase the local heat exchange area and improve the heat exchange efficiency. Figure 5 Structure diagram of the bicuspid valve structure 33, which is arranged at the connection area between the parallel micro-channels and the micro-pillar array 32. The bicuspid valve structure 33 adopts a valve-like flow guide design with an asymmetric channel geometry, which is used to simulate the valve guide function of biological fluids and can realize one-way fluid guidance and effectively suppress backflow.

[0036] Figure 6 Preparation process of the functional surface of the bionic micro-nano structure formed by arranging the micro-channel structure 31 on the inner wall of the micro-channel in the embodiment of the present application. The micro-channel adopts diamond as the substrate, which has excellent thermal conductivity and structural stability. The surface is constructed by drop casting deposition and inductively coupled plasma etching (ICP-RIE) process to form a micro-nano structure interface layer with bionic function, further improving the wetting performance and heat exchange efficiency in the micro-scale gas-liquid phase change process. The preparation of the functional surface of the bionic micro-nano structure formed by arranging the micro-channel structure 31 on the inner wall of the micro-channel includes the following steps:

[0037] S1. Micro-channel processing and nanoparticle deposition: the micro-channel structure is formed on the surface of the diamond substrate by laser cutting method; then, the nanoparticle deposition method is used to deposit gold nanoparticles on the inner wall of the micro-channel, which serves as the mask template for subsequent plasma etching.

[0038] S2. Inductively coupled plasma etching to construct nanowire array structure: the diamond surface is etched by inductively coupled plasma etching (ICP-RIE) method to form a bionic nanowire array. The geometric parameters such as the spacing and length of the nanowire can be precisely controlled by adjusting the process parameters such as power density, reaction chamber pressure, temperature, gas ratio and flow rate during etching. The structural morphology of the nanowire (such as cylindrical, conical or circular truncated cone) can be customized by changing the material of the nanoparticle mask template (such as SiO2, Al2O3).

[0039] S3. Microstructure reconstruction and functional surface formation: after the nanowire array etching is completed, the micro-gap structure is processed in the array area by using the precise laser cutting method, and the residual mask template material on the surface is removed, thereby obtaining a micro-nano functional surface with multi-scale bionic characteristics.

[0040] S4. Surface metallization and device integration: The constructed diamond microchannel structure and cover plate are respectively subjected to surface metallization treatment, and a gold layer is deposited as a bonding layer by using a magnetron sputtering method. Subsequently, device packaging bonding is achieved by using gold-tin solder, and a high-thermal-conductivity and high-strength diamond-based microchannel heat sink structure is constructed.

[0041] Figure 7 、 Figure 8 、 Figure 9 and Figure 10 The present application is an embodiment of a biomimetic micro-nano multi-scale structure surface boiling biomimetic enhancement mechanism analysis. In the present application, Figure 7 and Figure 8 The nanowires of the nanowire array 311 are arranged in a 3*3 array. Figure 9 and Figure 10 The nanowires of the nanowire array 311 are arranged in an 8*8 array. The micro-nano multi-scale functional surface of the present application refers to the arrangement of a nanoscale cylindrical array structure on the inner wall of the microchannel, and the array spacing is micrometer scale, so as to realize multi-scale synergistic effect in the microscale flow and heat exchange channel. The functional surface has multiple effects of strengthening wetting, inducing nucleation, and enhancing capillary driving through biomimetic design, and exhibits significant heat transfer enhancement effect in different dryness regions. Specifically, in the low dryness region of the microchannel inlet section, the microchannel structure 31 breaks the original smooth surface and enhances the roughness of the microchannel bottom surface, and the gaps between the nanowire arrays constitute a capillary structure with enhanced wettability. The liquid can effectively maintain the liquid layer at the bottom of the bubble after contacting the functional surface, enhance the wall surface wettability, and significantly inhibit the local dryout phenomenon; at the same time, the micrometer gaps between the nanowire arrays provide stable vaporization cores, which helps to reduce the nucleation superheat and increase the vaporization core density, thereby significantly enhancing the nucleate boiling heat transfer performance. In the high dryness region of the microchannel, due to the low proportion of liquid phase, the heat exchange depends on the efficient evaporation of the liquid film. At this time, the capillary channel composed of the nanowire array and the micrometer gap between the nanowire arrays can continuously attract the downstream residual liquid or the upstream working medium backflow into the gas-liquid interface, enhance the re-wetting ability of the wall surface, and maintain the continuity of the liquid film. This process promotes the reconstruction of the liquid film at the bottom of the bubble and the spreading of the annular flow liquid film, which helps to realize high-intensity thin film evaporation heat transfer under high heat flux, effectively delays dryout and improves heat transfer uniformity. Therefore, the micro-nano multi-scale structure surface constructed by the present application not only has good adaptability in different dryness conditions, but also can enhance local wettability, optimize nucleation environment and enhance capillary transport mechanism, comprehensively improve the phase change heat transfer performance in the microchannel, and significantly improve the boiling instability and local overheating problem.

[0042] The working medium is a low-boiling-point refrigerant HFE7100 or R134a or R1233zd.

[0043] The above detailed description is only for illustrating the technical concept and structural features of the present application, and is intended to enable the skilled in the art to implement it, but the above content does not limit the protection scope of the present application, and any equivalent changes or modifications made according to the spirit and principle of the present application shall fall within the protection scope of the present application.

Claims

1. A bionic micro-channel heat sink, comprising a working medium inlet (1), an inlet flow uniformization buffer tank (2), a first micro-channel structure (3), a second micro-channel structure (4), an outlet liquid collecting tank (5) and a working medium outlet (6), the working medium flowing into the inlet flow uniformization buffer tank (2) from the working medium inlet (1) and then entering the first micro-channel structure (3) and the second micro-channel structure (4) respectively, flowing to the outlet liquid collecting tank (5) after absorbing wall heat through latent heat and sensible heat of the working medium, and finally flowing out from the working medium outlet (6); characterized in that: The first microchannel structure (3) is a stepped microchannel structure, comprising a microcolumn array (32), a microchannel structure (31), and a bicuspid valve structure (33). The microcolumn array (32) is arranged below a high heat flux density point heat source. The microchannel structure (31) is located in a first low heat flux density area on both sides of the microcolumn array (32). The microchannel structure is composed of a plurality of parallel microchannels. The bicuspid valve structure (33) is located in a connecting area of the microchannel and the microcolumn array. The second microchannel structure is located in a second low heat flux density area between two first microchannel structures (3). The second microchannel structure is composed of at least one microchannel. Each microchannel has the same height and width and is symmetrically distributed along the heat sink center line. ​ 2. The biomimetic microchannel heat sink of claim 1, wherein: The microchannel bottom is arranged with a nanowire array, the nanowire array has a spacing of 5-10 μm and is arranged in a regular square array. Each nanowire of the nanowire array has a height of 2-3 μm and a diameter of 200-300 nm, and the nanowires have a spacing of 400-500 nm.

3. The biomimetic microchannel heat sink of claim 1, wherein: Each microcolumn of the microcolumn array (32) has a height of 480-500 μm and a diameter of 380-400 μm, and the microcolumns have a spacing of 280-300 μm.

4. The biomimetic microchannel heat sink of claim 1, wherein: The first microchannel structure (3) is two, symmetrically distributed along the heat sink center line. The second microchannel structure (4) is composed of three microchannels, one of which is located on the heat sink center line.

5. The biomimetic microchannel heat sink of claim 1, wherein: The first microchannel structure (3) is provided with two microcolumn arrays (32).

6. The biomimetic microchannel heat sink of claim 1, wherein: The bicuspid valve structure (33) is located on the side wall surface of the connecting area of the microchannel and the microcolumn array (32) and is composed of two asymmetric flow guide columns. One side is a circular arc profile downstream guide surface for guiding the main flow fluid to smoothly enter the downstream area. The other side is an outward convex reverse flow blocking surface for enhancing the reverse fluid pressure loss.

7. The biomimetic microchannel heat sink of claim 2, wherein: The stepped microchannel structure uses diamond as a substrate, and the surface uses drop casting deposition and inductively coupled plasma etching method to construct the nanowire array.

8. The biomimetic microchannel heat sink of claim 7, wherein: The steps for constructing the nanowire array are: S1. Microchannel processing and nanoparticle deposition: a microchannel structure is formed on the surface of the diamond substrate by laser cutting method. Then, nanometer gold particles are deposited on the inner wall of the microchannel groove by drop casting method as a mask template for subsequent plasma etching. S2. Inductively coupled plasma etching to construct a nanowire array structure: the surface of the diamond is etched by plasma to form a nanowire array. S3. Microstructure reconstruction and functional surface formation: after completing the nanowire array etching, the microgap of the nanowire array is processed in the nanowire array area, and the residual mask template material on the surface is removed to obtain the nanowire array.

9. The biomimetic microchannel heat sink of claim 8, wherein: In step S2, the spacing, length and height of the nanowire are precisely controlled by adjusting the power density, reaction chamber pressure, temperature, gas ratio and flow rate during the etching process. The structure of the nanowire is customized by replacing the material of the nanometer particle mask template.

10. The biomimetic microchannel heat sink of any one of claims 1-9, wherein: The working medium uses low-boiling-point refrigerant working medium HFE7100, R134a or R1233zd.

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