A composite microstructure surface that utilizes microtubes and micropores to synergistically enhance boiling heat transfer

Abstract

The present invention discloses a composite microstructure surface that utilizes microtubes and micropores to synergistically enhance boiling heat transfer, comprising a microcolumn matrix and a plurality of microcolumn units distributed in an array on the microcolumn matrix. The microcolumn unit is composed of a plurality of microcolumns distributed in an array, and each microcolumn has microtubes symmetrically arranged on each side wall and micropores symmetrically arranged on the top. By adding micropores on the top surface of the microcolumn, the number of vaporization cores on the microstructure surface is effectively increased, the superheat of the surface is reduced, and thus the boiling heat transfer coefficient of the surface is improved; secondly, microtubes are provided on each side wall of the microcolumn, and by utilizing the interaction between microcolumns, micropores and microtubes in regulating the gas-liquid behavior during the boiling process, a multi-directional rehydration system is established from the rehydration channel to the microcolumn unit groove and the microtube rehydration, thereby enhancing the rehydration capacity of the surface, increasing the critical heat flux density of the surface, delaying the occurrence of boiling crisis, and achieving synergistic enhancement of the boiling heat transfer performance of the microstructure surface.

Description

Technical Field

[0001] The present invention belongs to the technical field of enhanced phase change heat transfer, and relates to a boiling heat transfer enhanced surface, in particular to a composite microstructure surface that utilizes microtubes and micropores to synergistically enhance boiling heat exchange. Background Art

[0002] The gas-liquid phase change process during boiling heat transfer makes it a highly efficient heat transfer method, making it widely used in cooling systems for devices such as nuclear reactors, electric vehicle batteries, aerospace thermal control systems, and microelectronic chips. However, with the development of production and the continuous evolution of micromachining technology, the heat dissipation requirements of highly integrated and high-power devices are constantly increasing, and the temperature conditions required for safe and stable operation of these devices are becoming increasingly stringent. Therefore, to maintain the long-term safe and stable operation of high-heat flux devices, it is necessary to enhance the heat transfer coefficient and critical heat flux of boiling heat transfer, thereby improving the heat dissipation efficiency and operating limits of the cooling system.

[0003] In recent years, modifying the morphology of heat transfer surfaces has attracted widespread attention as a safe and efficient passive boiling heat transfer enhancement technology. Adding micropillars to the heat transfer surface can effectively increase the boiling heat transfer area, separate the gas-liquid paths, improve the rehydration capacity, and increase the critical heat flux density of the heat transfer surface. Adding micropores to the heat transfer surface can increase the number of vaporization cores on the surface, reduce the surface superheat, and enhance the surface boiling heat transfer coefficient. However, enhancing boiling heat transfer performance with a single factor often has inevitable drawbacks, so it is necessary to combine different enhancement factors to achieve a comprehensive enhancement of boiling heat transfer performance.

[0004] Micropillar and micropore structures can improve the fluid replenishment capacity and vaporization core density of the heat exchange surface, respectively. Combining the two can take advantage of their respective advantages to comprehensively improve the boiling heat transfer performance of the heat exchange surface. However, while micropores increase the surface nucleation density, they also cause a large number of bubbles to merge and block the channels, thereby worsening the fluid replenishment capacity of the micropillar surface and reducing the critical heat flux density and boiling heat transfer coefficient of the surface. Therefore, how to improve the gas-liquid behavior on the surface of the micropillar-micropore composite microstructure and achieve a synergistic enhancement of the vaporization core density and fluid replenishment capacity of the micropillar surface has become the key to improving the boiling heat transfer performance of the microstructure surface. Summary of the Invention

[0005] The purpose of the present invention is to provide a composite microstructure surface that utilizes microtubes and micropores to synergistically enhance boiling heat transfer, thereby increasing the surface nucleation density while enhancing the surface liquid supply capacity, thereby improving the surface boiling heat transfer coefficient and critical heat flux density.

[0006] The present invention is achieved through the following technical solutions:

[0007] A composite microstructure surface that utilizes microtubes and micropores to synergistically enhance boiling heat transfer, comprising a microcolumn substrate and a plurality of microcolumn units distributed in an array on the microcolumn substrate. The gaps between adjacent microcolumn units constitute fluid refill channels on the composite microstructure surface.

[0008] The microcolumn unit is composed of a plurality of microcolumns distributed in an array, the gaps between adjacent microcolumns are grooves, and the width of each groove is the same; the microcolumns are prismatic structures, the side walls of the microcolumns are inclined surfaces, and the angles C between the side walls of the microcolumns and the vertical plane are the same; microtubes extending to and penetrating the top surface of the microcolumn are symmetrically opened on each side wall of each microcolumn, the microtubes on each side wall of each microcolumn are evenly spaced, and a number of microholes are symmetrically opened on the top of each microcolumn.

[0009] Furthermore, the microtubes are distributed in the upper half of each microcolumn and extend through the top surface of the microcolumn, and the length of the microtubes is half of the height of the microcolumn.

[0010] Furthermore, the angle C between the sidewall surface of the microcolumn and the vertical surface is 0.8 degrees to 1.2 degrees.

[0011] Furthermore, the microcolumns are square columns with a width of 60 to 80 μm and a height of 100 to 140 μm.

[0012] Furthermore, the width of the internal channel of the microcolumn unit is 10 to 40 μm.

[0013] Furthermore, the width of the fluid infusion channel is 100-400 μm, and the sum of the width of the fluid infusion channel and the width of the microcolumn unit on one side is 1000 μm.

[0014] Furthermore, the micropore has a diameter of 3 to 5 μm, a depth of 16 to 28 μm, and a distance from the center of the micropore to the edge of the top surface of the microcolumn is one-fourth of the width of the top surface of the microcolumn.

[0015] Furthermore, the diameter of the microtube is 3 to 5 μm.

[0016] Compared with the prior art, the present invention has the following beneficial technical effects:

[0017] The present invention utilizes a composite microstructure surface that synergistically enhances boiling heat transfer by utilizing microtubes and micropores. First, by adding micropores to the top surface of the microcolumn, the number of vaporization cores on the microstructure surface is effectively increased, the surface superheat is reduced, and thus the surface boiling heat transfer coefficient is improved. Secondly, microtubes extending to and through the top surface of the microcolumn are symmetrically provided on each side wall of the microcolumn. By utilizing the interaction among the microcolumns, micropores, and microtubes in regulating the gas-liquid behavior during the boiling process, a multi-directional fluid replenishment system is established from the fluid replenishment channel to the microcolumn unit groove and the microtube fluid replenishment, thereby enhancing the surface fluid replenishment capacity, increasing the critical heat flux density of the surface, delaying the occurrence of boiling crisis, and achieving synergistic enhancement of the boiling heat transfer performance of the microstructure surface.

[0018] In addition, the microcolumn units distributed in an array on the microcolumn matrix can effectively regulate the growth process of surface bubbles. The fluid replenishment channels between the microcolumn units can avoid excessive fusion of bubbles in the lateral direction and delay the formation of air films on the surface of the microstructure to cause film boiling.

[0019] Furthermore, the length of the microtube is half of the height of the microcolumn. During the boiling heat transfer process, the capillary wicking effect of the microtube can enhance the liquid replenishment capacity of the channel, thereby avoiding the complete blockage of the channel by nucleated bubbles, effectively ensuring the stable operation of the nucleate boiling process; and the micropores and microtube structures added to the microcolumn increase the surface boiling heat transfer area, which is also conducive to enhancing the boiling heat transfer performance of the microstructure surface.

[0020] Furthermore, the composite microstructured surface, which utilizes microtubes and micropores to enhance boiling heat transfer, is fabricated in a single step using deep silicon etching, using an organic silicon substrate. During fabrication, the structural features of the composite microstructured surface are achieved through mask design. This simple and low-cost process allows for mass production of this composite microstructured surface, resulting in high economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 3D schematic diagram of the composite microstructure surface for enhancing boiling heat transfer by synergistically utilizing microtubes and micropores in the present invention;

[0022] Figure 2 It is a three-dimensional schematic diagram of the local structure of the microcolumn unit of the present invention;

[0023] Figure 3 Schematic diagram of the angle C between the side wall of the microcolumn and the vertical plane of the present invention;

[0024] Figure 4 is a top view of the microcolumn of the present invention;

[0025] Figure 5 This is an oblique scanning electron microscope image of the surface of a composite microstructure using microtubes and micropores to synergistically enhance boiling heat transfer in Example 1 of the present invention;

[0026] Figure 6 This is a comparison chart of boiling curves of Example 1 of the present invention and conventional micro-pillar surfaces and pillar-hole composite surfaces of the same structural dimensions;

[0027] Among them: 1-microcolumn matrix; 2-microcolumn unit; 3-fluid replenishment channel; 4-microcolumn; 5-micropore; 6-microtube; 7-groove. DETAILED DESCRIPTION

[0028] The present invention will be further described in detail below with reference to specific embodiments, which are intended to explain the present invention rather than to limit it.

[0029] The present invention provides a composite microstructure surface that utilizes microtubes and micropores to synergistically enhance boiling heat transfer, see Figures 1 to 4 , including a microcolumn substrate 1, a microcolumn unit 2, a fluid replenishment channel 3, a microcolumn 4, a micropore 5, a microtube 6 and a groove 7: the microcolumn units 2 are distributed in an array on the microcolumn substrate 1, and the gaps between adjacent microcolumn units 2 constitute the fluid replenishment channel 3 on the surface of the composite microstructure, which is a macro fluid replenishment path during the boiling heat exchange process on the composite microstructure surface; the microcolumn unit 2 is composed of microcolumns 4 distributed in an array, and the gaps between adjacent microcolumns 4 are the grooves 7 on the surface of the composite microstructure, which provide fluid replenishment for the microcolumn units 2 during the boiling heat exchange process; wherein, the width of the fluid replenishment channel 3 of the macro fluid replenishment path ranges from 100 to 400 μm, the width of the groove 7 ranges from 10 to 40 μm, and the sum of the width of the microcolumn unit 2 and the width of the fluid replenishment channel 3 on one side is 1000 μm.

[0030] like Figure 3 As shown, the microcolumn 4 is a prismatic structure, the side walls of the microcolumn 4 are inclined surfaces, and the angles C between the side walls of the microcolumn 4 and the vertical plane are the same. A microtube 6 extending upward and penetrating the top surface of the microcolumn 4 is provided on the side wall of each microcolumn 4. During the boiling heat exchange process, the microtube 6 can enhance the fluid replenishment capacity of the channel 7; the microtubes 6 are symmetrically distributed on the top surface of the microcolumn 4, and the spacing between adjacent microtubes 6 is the same; wherein, the microcolumn 4 is a square column, the width of the microcolumn 4 ranges from 60 to 80 μm, and the height of the microcolumn 4 ranges from 100 to 140 μm; the angle C between the side walls of the microcolumn 4 and the vertical plane ranges from 0.8 degrees to 1.2 degrees; the diameter of the microtube 6 ranges from 3 to 5 μm, and the length of the microtube 6 is half of the height of the microcolumn 4.

[0031] Several micropores 5 are symmetrically distributed on the top of the micropillar 4, the spacing between adjacent micropores 5 is the same, and the spacing from the center of the micropore 5 to the edge of the top surface of the micropillar 4 is one-fourth of the width of the top surface of the micropillar 4; on the top surface of the micropillar 4, the diameter of the micropore 5 ranges from 3 to 5 μm, and the depth of the micropore 5 ranges from 16 to 28 μm.

[0032] The present invention is based on a micropillar array structure. By arranging microtubes and micropore structures on the side walls and tops of the micropillars, it achieves an integrated multi-dimensional composite of micropores, microtubes and micropillars, while increasing the surface vaporization core density and enhancing the surface liquid replenishment capacity, thereby achieving a synergistic enhancement of the boiling heat transfer performance of the microstructure surface.

[0033] The present invention utilizes a deep silicon etching method to fabricate a composite microstructured surface that utilizes microtubes and micropores to synergistically enhance boiling heat transfer. During this process, a corresponding mask is designed based on the structural characteristics of the composite microstructured surface. Next, the silicon wafer is pretreated and coated with a photoresist. Hardening bake, etching, and resist removal are then performed to obtain the desired composite microstructured surface.

[0034] The technical solution of the present invention is further described in detail below through examples:

[0035] Example 1:

[0036] 1. Prepare a composite microstructure surface that uses microtubes and micropores to synergistically enhance boiling heat transfer, with a microcolumn width of 70 μm, a microcolumn height of 120 μm, a groove of 20 μm, a microtube diameter of 4 μm, a microtube length of 60 μm, a microtube spacing of 14 μm, and 16 microtubes. The number of micropores on the top surface of the microcolumn is 4, the micropore diameter is 4 μm, and the spacing between the center of the micropore and the edge of the microcolumn top surface is 17.5 μm. The microcolumns are distributed in an 8×8 array, the rehydration channel width is 300 μm, and the microcolumn units are distributed in a 10×10 array.

[0037] 2. Based on the basic structural characteristics and size of the composite microstructure surface that utilizes microtubes and micropores to synergistically enhance boiling heat transfer, the corresponding mask pattern is first designed, and the mask processing is completed according to the designed mask size.

[0038] 3. The silicon wafer was first pretreated with hexamethyldisilazane (HMDS). After 10 minutes of pretreatment, the silicon wafer was placed on a coating machine and rotated forward at 600 rpm for 6 seconds and reversed at 4000 rpm for 30 seconds, so that the front of the silicon wafer was evenly coated with photoresist AZ6130 with a coating thickness of 7.5 μm.

[0039] 4. The coated silicon wafer was pre-dried on a contact hot plate at 100°C for 5 minutes to obtain a relatively strong photoresist layer. The wafer was then exposed on an MA6 lithography machine for 23 seconds and developed in a 2.38% tetramethylammonium hydroxide (TMAH) developer for 150 seconds.

[0040] 5. After the development process is complete, a hard film bake is performed at a temperature of 110°C for 5 minutes. After this 5-minute hard film bake, the etching process begins. During the etching process, the etching rate is tested for 5 minutes using a step profiler, which is 6μm per minute. An additional 16 minutes of etching is then performed. After microscopic inspection shows no obvious defects, the resist is removed and the process is complete.

[0041] Figure 5 The figure shows an oblique scanning electron microscope image of the composite microstructure surface prepared in Example 1 that utilizes microtubes and micropores to synergistically enhance boiling heat transfer. It can be seen that the novel composite microstructure surface designed in the present invention has a stable structure, reliable processing quality, and good application prospects. Furthermore, experimental measurements have shown that the composite microstructure surface in Example 1 that utilizes microtubes and micropores to synergistically enhance boiling heat transfer has improved boiling heat transfer coefficients and critical heat flux densities compared to conventional micropillar surfaces containing only micropillar structures and column-pore composite surfaces of the same size. Figure 6 .

Claims

1. A composite microstructure surface that utilizes microtubes and micropores to synergistically enhance boiling heat transfer, characterized by: The composite microstructure comprises a microcolumn substrate (1) and a plurality of microcolumn units (2) distributed in an array on the microcolumn substrate (1), wherein the gaps between adjacent microcolumn units (2) form a fluid replenishment channel (3) on the surface of the composite microstructure; The microcolumn unit (2) is composed of a plurality of microcolumns (4) distributed in an array, the gaps between adjacent microcolumns (4) are grooves (7), and the widths of the grooves (7) are the same; the microcolumns (4) are prismatic structures, the side walls of the microcolumns (4) are inclined surfaces, and the angles C between the side walls of the microcolumns (4) and the vertical surface are the same; microtubes (6) extending to and penetrating the top surface of the microcolumn (4) are symmetrically opened on the side walls of each microcolumn (4), the microtubes (6) on the side walls of each microcolumn (4) are distributed at equal intervals, and a plurality of micropores (5) are symmetrically opened on the top of each microcolumn (4).

2. The composite microstructure surface for enhancing boiling heat transfer by synergistically utilizing microtubes and micropores according to claim 1, characterized in that: The microtubes (6) are distributed in the upper half of each microcolumn (4) and extend through the top surface of the microcolumn (4). The length of the microtubes (6) is half the height of the microcolumn (4).

3. The composite microstructure surface for enhancing boiling heat transfer by synergistically utilizing microtubes and micropores according to claim 2, characterized in that: The included angle C between the side wall surface of the microcolumn (4) and the vertical surface is 0.8 degrees to 1.2 degrees.

4. The composite microstructure surface for enhancing boiling heat transfer by synergistically utilizing microtubes and micropores according to any one of claims 1 to 3, characterized in that: The microcolumns (4) are square columns with a width of 60 to 80 μm and a height of 100 to 140 μm.

5. The composite microstructure surface for enhancing boiling heat transfer by synergistically utilizing microtubes and micropores according to any one of claims 1 to 3, characterized in that: The width of the internal channel (7) of the microcolumn unit (2) is 10 to 40 μm.

6. The composite microstructure surface for enhancing boiling heat transfer by synergistically utilizing microtubes and micropores according to any one of claims 1 to 3, characterized in that: The width of the fluid replenishment channel (3) is 100-400 μm, and the sum of the width of the fluid replenishment channel (3) and the width of the microcolumn unit (2) on one side is 1000 μm.

7. The composite microstructure surface for enhancing boiling heat transfer by synergistically utilizing microtubes and micropores according to any one of claims 1 to 3, characterized in that: The pore diameter of the micropore (5) is 3-5 μm, the depth of the micropore (5) is 16-28 μm, and the distance from the center of the micropore (5) to the edge of the top surface of the microcolumn (4) is one-fourth of the width of the top surface of the microcolumn (4).

8. The composite microstructure surface for enhancing boiling heat transfer by synergistically utilizing microtubes and micropores according to any one of claims 1 to 3, characterized in that: The diameter of the microtube (6) is 3 to 5 μm.

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