Layered gradient porous wick and preparation method and application thereof

Abstract

The application relates to the technical field of thermal management materials, in particular to a layered gradient porous wick and a preparation method and application thereof. A layered gradient porous wick is provided, which comprises a capillary enhancement layer and a permeation resistance reduction layer arranged in sequence along a preset liquid supply direction; the capillary enhancement layer is provided with a plurality of first through holes, the first through holes have at least one of a sharp corner and a high-curvature boundary characteristic; the permeation resistance reduction layer is provided with a plurality of second through holes, the opening area of the second through holes is larger than and contains the opening area of the corresponding first through holes, and the two are through at a layered interface; wherein each first through hole is in communication with the second through hole. The first through hole with the sharp corner or the high-curvature boundary characteristic provides a higher local capillary pressure difference, the flow resistance of the liquid working medium is reduced through the second through hole with a larger opening area, the continuity of the liquid supply channel is ensured through the communication between each first through hole and the second through hole, and the synergistic optimization of the capillary driving force and the flow permeability in a single component is facilitated.

Description

Technical Field

[0001] This application relates to the field of thermal management materials technology, and in particular to a layered gradient porous liquid absorbent core, its preparation method and application. Background Technology

[0002] Two-phase heat transfer devices such as heat pipes and vapor chambers rely on a wick to establish a capillary pressure difference between the evaporation and condensation ends, driving the working fluid to circulate. In engineering practice, the wick can be made of grooves, wire mesh, sintered powder, foamed metal, or composite structures. Its design faces inherent constraints from capillary drive and permeation transport: reducing the pore size can increase the capillary pressure difference, but it will increase the resistance to liquid flow; increasing the pore size can reduce the backflow resistance, but the capillary force will weaken accordingly, and insufficient liquid supply may occur under high heat flux or long-distance backflow conditions.

[0003] Additive manufacturing technologies such as laser powder bed melting provide a new path for the integrated fabrication of regular lattice structures, improving pore shape controllability and three-dimensional connectivity compared to traditional sintering processes. However, additive manufacturing still faces process constraints in areas such as the energy density window for fine feature forming, powder residue removal, and the influence of forming posture on orifice openness and interlayer connectivity. These factors affect the consistency and repeatability of liquid absorption performance.

[0004] Chinese patent CN111185725A discloses a gradient-aperture porous copper wick for loop heat pipes and its preparation method. The method involves mixing copper powder with pore-forming agents of different particle sizes, layering the mixture, and sintering it to gradually increase the pore size from bottom to top. This process is simple and low-cost. However, the resulting pore morphology is a randomly connected network. The three-dimensional channel orientation and interlayer transitions are affected by particle size distribution and the sintering process, making it difficult to obtain a regular and precisely designed connected topology. Furthermore, when further reducing the pore size to improve capillary suction performance, the spatial competition between vapor and liquid channels intensifies, limiting batch consistency and structural controllability.

[0005] Therefore, how to achieve synergistic optimization of capillary pressure difference and permeability while taking into account the manufacturability of the structure and the consistency of performance when using additive manufacturing to prepare porous liquid-absorbing cores is a technical problem that needs to be solved. Summary of the Invention

[0006] This application aims to address at least one of the technical problems existing in the prior art. To this end, this application provides a layered gradient porous absorbent core, its preparation method, and its application, aiming to achieve synergistic optimization of capillary pressure difference and permeability.

[0007] To achieve the above objectives, the technical solution adopted in this application is as follows: A layered gradient porous liquid-absorbing core includes a capillary reinforcement layer and a permeability-reducing layer arranged sequentially along a preset liquid supply direction; the capillary reinforcement layer has a plurality of first through holes, each of which has at least one of the following characteristics: sharp corners and high curvature boundary features; the permeability-reducing layer has a plurality of second through holes, the opening area of ​​which is larger than the opening area of ​​the corresponding first through hole; wherein each first through hole is connected to a corresponding second through hole in the permeability-reducing layer, and on a projection plane perpendicular to the preset liquid supply direction, the opening area of ​​the first through hole at the layering interface is located within the opening area of ​​the corresponding second through hole at the layering interface.

[0008] Through this technique, the first through-hole of the capillary reinforcement layer has sharp corners or high curvature boundary features, increasing the local curvature of the pore wall and raising the capillary pressure difference, allowing the working fluid to be rapidly drawn in under capillary force. The second through-hole of the permeation and drag-reducing layer has a larger opening area, which can reduce the liquid flow resistance, allowing the working fluid to flow back smoothly and be continuously supplied to the evaporation interface. Specifically, the first through-hole penetrates the capillary reinforcement layer and forms a first interface opening at the layered interface, and the second through-hole penetrates the permeation and drag-reducing layer and forms a second interface opening at the layered interface. On the projection plane perpendicular to the preset liquid supply direction, the first interface opening is located within the corresponding second interface opening, and the two are directly connected at the layered interface, allowing the liquid working fluid to directly enter the second through-hole from the first through-hole. The area of ​​the second through-hole is larger than that of the first through-hole, and there is no closed partition or local obstruction for the working fluid to enter the second through-hole from the first through-hole, forming a liquid supply channel that runs from the capillary reinforcement layer to the permeation and drag-reducing layer. Thus, the lower layer with a smaller opening area of ​​the first through-hole structure provides sufficient capillary driving force to achieve rapid liquid initiation, while the upper layer with a larger opening area of ​​the second through-hole structure provides a low-resistance channel to ensure continuous liquid supply. The connection between the two layers makes the liquid supply process continuous and stable, thereby solving the technical problem of simultaneously taking into account capillary driving force and flow permeability.

[0009] Furthermore, the first through hole is an equilateral triangle.

[0010] Furthermore, the second through hole is circular, and the diameter of the second through hole is not less than the circumcircle diameter of the first through hole.

[0011] Furthermore, the side length of the first through hole is 0.19~0.26 mm, the inner corner radius does not exceed 5% of the side length, and the minimum wall thickness between adjacent first through holes is 0.05~0.15 mm.

[0012] Furthermore, the opening area of ​​the second through hole is 2.0 to 3.5 times the opening area of ​​the corresponding first through hole, and the length of the capillary reinforcement layer along the preset liquid supply direction is 40% to 60% of the total length of the porous liquid-absorbing core along the preset liquid supply direction.

[0013] Optionally, the first through holes are arranged alternately along the circumference; the second through hole is a parallelogram hole, and the projections of two circumferentially adjacent first through holes along the preset liquid supply direction are both within the second through hole.

[0014] This application also provides a method for preparing the aforementioned layered gradient porous liquid-absorbing core, which is integrally formed by laser selective melting process, and uses stainless steel powder with a particle size of 15~53 µm and an oxygen content of no more than 0.02%; under laser power of 60~150W, scanning speed of 1200~1850 mm / s, scanning interval of 0.13~0.22 mm, and powder layer thickness of 20~40 µm, the powder is melted and deposited layer by layer in a vertical or inclined at 30°±5° relative to the vertical direction; the scanning strategy adopts outer contour scanning combined with staggered filling, and the scanning directions of adjacent layers are staggered.

[0015] Furthermore, the stainless steel powder is spherical powder of 316 or 316L stainless steel.

[0016] Furthermore, when forming the capillary reinforcement layer, an outer contour scanning combined with staggered filling is used.

[0017] This application also provides the application of the aforementioned layered gradient porous wick in heat pipes, loop heat pipes or heat spreaders, wherein the capillary reinforcement layer is located on the evaporation end side and the permeation resistance reduction layer is located on the condensation end side.

[0018] In summary, the beneficial effects of this application include: 1. The layered gradient porous liquid-absorbing core provided in this application adopts a capillary reinforcement layer and a permeability-reducing layer arranged sequentially along the preset liquid supply direction. The first through hole with sharp corners or high curvature boundary features provides a high local capillary pressure difference, while the second through hole with a larger opening area reduces the flow resistance of the liquid working fluid. The two layers are connected to ensure the continuity of the liquid supply channel, which is conducive to achieving synergistic optimization of capillary driving force and flow permeability in a single component.

[0019] 2. Experimental data show that in the vertical liquid aspiration test, compared with the single-layer full triangular hole structure, the layered gradient porous liquid aspiration core of this application has a good improvement in net liquid aspiration at 4 min and 20 min, indicating that the structure has an improved effect in balancing the rapid liquid aspiration capacity in the early and middle stages and the continuous liquid supply capacity in the later stages.

[0020] 3. The preparation method provided in this application adopts laser selective melting process for integral forming. By limiting process parameters such as powder particle size, oxygen content, laser power, scanning speed, scanning interval, powder layer thickness, forming posture and scanning strategy, it is beneficial to reproduce the target geometric dimensions while maintaining the stable forming of sharp corner features, and provides manufacturability guarantee for the above-mentioned layered gradient porous liquid absorption core structure.

[0021] 4. When the porous liquid wick provided in this application is applied to a heat pipe, a loop heat pipe or a vapor chamber, the capillary reinforcement layer is placed on the evaporation end side and the permeation resistance reduction layer is placed on the condensation end side. This is beneficial for the evaporation end to obtain high capillary driving force to achieve rapid start-up liquid supply. At the same time, the condensation end reduces the backflow resistance through the large opening area through-hole channel to ensure continuous liquid supply, thereby helping to improve the overall heat transfer performance and operational stability of the above heat transfer device. Attached Figure Description

[0022] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings: Figure 1 This is a schematic diagram of the structure of an optional layered gradient porous liquid-absorbing core in an embodiment of this application; Figure 2 This is a schematic diagram of the layered gradient porous liquid absorption core of Embodiment 1 of this application; Figure 3 This is a schematic diagram of the capillary reinforcement layer in Embodiment 1 of this application; where a represents the side length of the first through hole and b represents the minimum wall thickness between adjacent first through holes; Figure 4 This is a schematic diagram showing the geometric mapping relationship between the first through hole and the second through hole in Embodiment 1 of this application; Figure 5 This is a schematic diagram showing the geometric mapping relationship between the first through hole and the second through hole in Embodiment 2 of this application; Figure 6 This is a flowchart of the preparation method in Example 3 of this application; Figure 7 This is a schematic diagram of the vertical liquid aspiration test device provided in Embodiment 4 of this application.

[0023] Explanation of reference numerals in the attached figures: 1. Capillary reinforcement layer; 2. Permeability reduction layer; 3. Glass cover; 4. Iron stand; 5. Lifting platform; 6. Sample holder; 7. Sample to be tested; 8. Liquid working medium; 9. Observation port; 10. Infrared thermal imager. Detailed Implementation

[0024] To enable those skilled in the art to better understand the technical solutions of this application, the technical solutions of this application will be further described below in conjunction with the accompanying drawings and embodiments.

[0025] Example 1 Reference Figures 1 to 4 This embodiment provides a layered gradient porous wick for providing capillary drive and reflux channels in heat pipes, loop heat pipes or vapor chambers.

[0026] The liquid absorption core can be configured with different cross-sectional shapes, such as rectangular, circular, annular or other adaptable shapes, depending on the application scenario and installation space.

[0027] The liquid-absorbing core is sequentially provided with a capillary reinforcement layer 1 and a permeation resistance reduction layer 2 along the preset liquid supply direction. The two layers are connected at the layer interface, thereby forming a gradient flow channel that runs from a small opening area through hole to a large opening area through hole, so as to reduce the liquid backflow resistance while ensuring the capillary pressure difference.

[0028] (1) Capillary reinforcement layer 1 The capillary reinforcement layer 1 has multiple first through-holes. Each first through-hole has sharp corners or high curvature boundary features. In this embodiment, the first through-hole is an equilateral triangle. The equilateral triangular microporous structure establishes a large capillary pressure difference through its high interface curvature, enabling rapid initial intake of the working fluid.

[0029] The side length of the equilateral triangles is selected to be 0.19~0.26 mm, the minimum wall thickness between adjacent equilateral triangles is 0.05~0.15 mm, the radius of the interior corner fillet does not exceed 5% of the side length, and the array is arranged in a regular dot matrix to suppress the accumulation of dimensional dispersion and forming deformation.

[0030] In the annular liquid-absorbing core, multiple first through holes are arranged sequentially along the circumference and form multiple rings of holes in the radial direction. Staggered arrangement means that the first through holes are staggered along the circumferential extension direction, that is, adjacent equilateral triangular holes are relatively staggered, so that adjacent triangular holes face opposite directions (i.e., the apex of one triangular hole faces inward, and the apex of another triangular hole faces outward). Non-staggered arrangement means that the first through holes are not staggered along the circumference, specifically, adjacent equilateral triangular holes are correspondingly arranged without misalignment, and adjacent triangular holes face the same direction (i.e., the apex of each triangular hole faces outward, or both face inward). The minimum clear distance between the boundaries of adjacent first through holes is denoted as b, and this minimum clear distance b is the minimum wall thickness between adjacent first through holes. In the staggered arrangement embodiment, b also represents the minimum rib thickness of the connecting rib between adjacent first through holes; in the non-staggered arrangement embodiment, b represents the minimum clear distance between the boundaries of adjacent first through holes, and this minimum clear distance is the minimum wall thickness at that location.

[0031] (2) Permeability-reducing layer 2 The permeation and resistance-reducing layer 2 has multiple second through-holes. The opening area of ​​each second through-hole is larger than the opening area of ​​the corresponding first through-hole. On a projection plane perpendicular to the preset liquid supply direction, the opening area of ​​the first through-hole at the layer interface is located within the opening area of ​​the corresponding second through-hole at the layer interface. Therefore, the second through-holes not only provide a larger flow cross-section to reduce liquid backflow resistance, but also maintain stable communication with the first through-hole at the layer interface, preventing liquid supply interruption due to misalignment or partial obstruction of the upper and lower layer channels.

[0032] The second through-hole is circular, and the first through-hole is an equilateral triangle with side length *a*, whose circumcircle diameter is approximately 2*a* / 1.732. When the diameter of the second through-hole is equal to the circumcircle diameter, the ratio of the opening area of ​​the second through-hole to that of a single first through-hole is approximately 2.42. Increasing the diameter of the second through-hole can improve this ratio, but an excessively large diameter will result in excessively thin array walls and decreased forming stability. Accordingly, the opening area of ​​the second through-hole is controlled to be 2.0 to 3.5 times the opening area of ​​a single first through-hole. The length of the capillary reinforcement layer 1 along the preset liquid supply direction is 40% to 60% of the total length of the porous liquid-absorbing core along the preset liquid supply direction.

[0033] (3) Geometric mapping relationship like Figure 4 As shown, when the second through hole is circular, the first through hole is preferably arranged in a non-staggered manner. Figure 4 The circular outline represents the opening area of ​​the second through-hole in the permeability reduction layer 2, and the equilateral triangle outline within the circular outline represents the opening area of ​​the corresponding first through-hole in the capillary reinforcement layer 1. Each circular second through-hole corresponds to an equilateral triangle first through-hole. The center of the circular second through-hole and the geometric center of the corresponding equilateral triangle first through-hole are aligned along a preset liquid supply direction, and the diameter of the second through-hole is not less than the diameter of the circumcircle of the first through-hole. This ensures that the opening area of ​​the first through-hole at the layer interface is located within the opening area of ​​the corresponding second through-hole at the layer interface, thereby maintaining the geometric correspondence between the two layers of channels.

[0034] Each first through-hole is connected to a second through-hole, meaning that each first through-hole directly connects to the corresponding second through-hole at the layering interface, without a sealing layer or barrier wall at the layering interface. When the liquid working fluid enters the second through-hole of the permeability-reducing layer 2 from the first through-hole of the capillary reinforcement layer 1, it can smoothly transition along the through-channel, which helps to establish a balance between capillary driving force and flow resistance, and maintain a high final net lift height.

[0035] Example 2 like Figure 5 As shown, based on Embodiment 1, the second through hole in this embodiment is a parallelogram hole. The first through holes are staggered along the circumferential extension direction, that is, adjacent equilateral triangular holes are staggered relative to each other along the circumferential direction, so that the two adjacent triangular holes face opposite directions (i.e., the top apex of one triangular hole faces inward, and the top apex of another triangular hole faces outward). Figure 5The parallelogram outline represents the opening region of the second through-hole in the permeability-reducing layer 2, and the equilateral triangle outline within the parallelogram outline represents the opening region of the corresponding first through-hole in the capillary reinforcement layer 1. The second through-hole is formed by removing the rib walls between two adjacent first through-holes and connecting them. At the layer interface, the opening regions of two adjacent first through-holes are located within the opening region of the same parallelogram-shaped second through-hole, thus forming a geometric mapping relationship from multiple small-opening through-holes to a large-opening low-resistance channel. This parallelogram-shaped hole, while maintaining the array periodicity and geometric continuity, further enlarges the cross-sectional area of ​​the flow channel and reduces the liquid backflow resistance.

[0036] The second through-hole is formed by removing the rib walls from the upper regions of two adjacent first through-holes and connecting them. Let the side length of the first through-hole be *a*, and the minimum wall thickness between adjacent first through-holes be *b*. Then, the ratio of the opening area of ​​this parallelogram-shaped second through-hole to that of a single first through-hole is approximately 2 + 4b / (1.732a). Substituting *a* = 0.19~0.26 mm and *b* = 0.05~0.15 mm, the ratio is approximately 2.44~3.80. The combination of minimum *a* and maximum *b* (ratio approximately 3.8) is not a practically optimal design (too high rib wall ratio, reduced effective through-hole density). Therefore, the area ratio is also controlled to be 2~3.5 times.

[0037] Example 3 Reference Figure 6 This embodiment provides a method for preparing a porous liquid-absorbing core as described in Embodiment 1 or 2, which is integrally formed using a laser selective melting process.

[0038] The raw material is spherical powder of 316 or 316L stainless steel with a particle size of 15~53 μm and an oxygen content of no more than 0.02% to ensure the compactness of the powder and the stability of the forming.

[0039] The equipment parameters are: powder layer thickness 20~40 μm, laser power 60~150 W, scanning speed 1200~1850 mm / s, and scanning spacing 0.13~0.22 mm. To obtain clear sharp corners and stable thin walls, the forming posture is vertical or tilted at 30°±5° relative to the vertical direction. The scanning strategy adopts outer contour scanning combined with staggered filling, and the scanning directions of adjacent layers are staggered and moderately rotated to reduce anisotropy and thermal stress accumulation.

[0040] When forming the capillary reinforcement layer 1, an outer contour scanning combined with staggered filling is used.

[0041] After molding, the powder is removed, ultrasonically cleaned and dried. If necessary, low-temperature stress relief (low-temperature annealing) and surface activation treatment are carried out to improve wettability and stabilize the initial liquid absorption rate.

[0042] Quality control employs microscopic measurement to verify the side length, minimum wall thickness, and hole wall thickness of the triangular holes, combined with sampling inspections of the permeability and continuity, to ensure stable connection between the two layers of channels along the preset liquid supply direction.

[0043] By combining the above materials, parameters and post-processing, the target geometric dimensions and roughness window can be stably reproduced without closing the channels, providing manufacturability assurance for the layered gradient porous liquid-absorbing core structure of Example 1 or 2.

[0044] Example 4 This embodiment tests the liquid absorption performance of the porous liquid-absorbing cores from Examples 1 and 2. Specifically, infrared capillary rise height measurement is used to measure the capillary rise height of the porous liquid-absorbing core. Utilizing the difference in emissivity between the liquid working fluid and the liquid-absorbing core material, different temperature distributions are observed using an infrared thermal imager 10, thereby obtaining the capillary rise height of the liquid-absorbing core.

[0045] like Figure 7 As shown, the vertical liquid absorption test device includes a glass cover 3, an iron frame 4, a lifting platform 5, a sample clamp 6, a sample to be tested 7, a liquid working medium 8, an observation port 9, and an infrared thermal imager 10. The sample to be tested 7 is vertically fixed to the iron frame 4 by the sample clamp 6. The liquid working medium 8 is located below the bottom of the sample to be tested 7 and its height can be adjusted with the lifting platform 5. During the test, the bottom of the sample to be tested 7 is immersed in the liquid working medium 8 by adjusting the lifting platform 5. The infrared thermal imager 10 collects the liquid rising interface in the sample to be tested through the observation port 9. To reduce the influence of ambient temperature on the test results, the test area is shielded by the glass cover 3 during the test.

[0046] During the test, the position and height of the infrared thermal imager 10 were adjusted, and the focusing ring was adjusted to ensure clear image acquisition. The net rise height of anhydrous ethanol in the sample 7 under test was measured at 4 min, 20 min, and 60 min in a vertical position, and the rise height of the liquid in the channel was recorded over time. At the same time, the consistency between the rising interface of the inner and outer walls and the wetting front was observed in combination with the imaging results to ensure the repeatability of the readings.

[0047] The net height increase at 4 min and 20 min was used as the interim evaluation indicators, and the results of representative samples were used for explanation.

[0048] Two types of samples were selected for comparison under the same overall length and test conditions. The axial length of the ring sample was approximately 150 mm, the outer diameter was approximately 20 mm, and the inner diameter was approximately 14 mm.

[0049] One type is a single-layer structure with all triangular holes. The sample is approximately 15 cm long, with equilateral triangular holes having a side length of 0.20 mm and a minimum net spacing of 0.05 mm. As it is a single-layer homogeneous array configuration, layer thickness ratio is not considered. This sample typically exhibits a net lift of 92–98 mm at 4 minutes and 135–140 mm at 20 minutes, demonstrating good late-stage net lift height and repeatability.

[0050] The second example is the porous absorbent core of Example 1, with a sample length of approximately 15 cm. The layered interface is located in the middle of the sample, and the length of the capillary reinforcement layer 1 is approximately 50% of the total length of the porous absorbent core. Typical parameters for the equilateral triangular pores in the capillary reinforcement layer 1 are a side length of 0.22 mm and a minimum net distance of 0.09 mm. The second through-hole in the permeability-reducing layer 2 is circular, and the center of the circular second through-hole is aligned with the geometric center of the equilateral triangular first through-hole along the preset liquid supply direction. Furthermore, the diameter of the circular second through-hole is not less than the circumcircle diameter of the first through-hole, thus establishing a layered channel along the preset liquid supply direction where the small-opening first through-hole of the capillary reinforcement layer 1 and the large-opening second through-hole of the permeability-reducing layer 2 are connected at the layered interface. This layered composite representative sample achieved a net lift of approximately 110 mm in 4 minutes and approximately 150 mm in 20 minutes. Therefore, under the conditions of this annular embodiment, the layered composite structure of Example 1, compared with the single-layer full triangular hole structure, has a net lift of about 12% to 20% in the 4-minute stage and a net lift of about 7% to 11% in the 20-minute stage.

[0051] In Example 2, when the second through-hole is replaced with a parallelogram-shaped hole, the first through-hole is arranged in an alternating pattern. Compared to a single-layer full triangular hole structure, there is an improvement in both aspects: a net increase of approximately 101 mm at 4 minutes and approximately 149 mm at 20 minutes. The lower triangular holes maintain a high capillary pressure difference to ensure the early and mid-stage start-up speed, while the upper parallelogram-shaped holes reduce the later backflow resistance with a larger opening area. The two are connected through a through interface without crowding each other out. Thus, while the net increase height in the later stage is significantly improved compared to the single-layer structure, the early and mid-stage liquid absorption performance is not deteriorated due to the presence of the large holes in the upper layer.

[0052] The area magnification factor of the parallelogram-shaped second through-hole and the first through-hole is greater than that of the circular second through-hole (approximately 2.42), which can further reduce backflow resistance and improve permeability. At the same time, the two first through-holes share one second through-hole, so when one of the first through-holes is partially blocked, the other first through-hole can still supply liquid independently, providing redundancy and stability of the liquid supply channel.

[0053] In summary, combining the results from Examples 1 and 2, with the capillary reinforcement layer accounting for approximately 50% of the total length of the porous core and the through-holes in the upper and lower layers being interconnected, the net lift can reach approximately 100-110 mm in 4 minutes and approximately 149-150 mm in 20 minutes. Therefore, setting the capillary reinforcement layer length within the range of 40%-60%, combined with the interconnectedness of the upper and lower layers, helps to balance rapid early-stage liquid absorption with continuous liquid supply in the later stages.

[0054] Example 5 Based on the good performance tested in Example 4, this example provides the application of the porous liquid wick of Example 1 or Example 2 in a heat pipe, loop heat pipe or vapor chamber, wherein the capillary reinforcement layer 1 is located on the evaporation end side and the permeation resistance reduction layer 2 is located on the condensation end side.

[0055] The preset liquid supply direction is from the evaporation end to the condensation end. During operation, the liquid working fluid on the evaporation end side is heated and evaporated, and the vapor migrates to the condensation end and condenses into liquid. The condensed liquid working fluid flows back from the condensation end to the evaporation end under capillary drive, forming a self-circulation. Among them, the capillary reinforcement layer 1 on the evaporation end side uses the sharp corner or high curvature boundary features of the first through hole to establish a high capillary pressure difference, enabling the liquid working fluid to quickly wet the channel and overcome the backflow resistance to start the liquid supply; the permeation and resistance reduction layer 2 on the condensation end side uses the large opening area of ​​the second through hole to form a low-resistance transport channel, reducing the flow resistance of the liquid working fluid during long-distance backflow. Through the corresponding interconnection between the two layers at the interface, the liquid working fluid, after obtaining high capillary driving force at the evaporation end, smoothly transitions through the interface to the larger channel of the permeation and drag reduction layer 2 for reflux, forming a liquid supply path that continuously transitions from through holes with small opening areas to through holes with large opening areas. This takes into account both rapid response start-up and continuous stable liquid supply, thereby improving the overall heat transfer performance and operational stability of heat pipes, loop heat pipes, or vapor chambers.

[0056] The foregoing has shown and described the basic principles, main features, and advantages of this application. Those skilled in the art should understand that this application is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of this application. Various changes and modifications can be made to this application without departing from the spirit and scope thereof, and all such changes and modifications fall within the scope of this application as claimed. The scope of protection of this application is defined by the appended claims and their equivalents.

Claims

1. A layered gradient porous liquid-absorbing core, characterized in that, It includes a capillary reinforcement layer (1) and a permeability reduction layer (2) arranged sequentially along the preset liquid supply direction. The capillary reinforcement layer (1) has a plurality of first through holes, the first through holes having at least one of sharp corners and high curvature boundary features; The permeability-reducing layer (2) has a plurality of second through holes, the opening area of ​​the second through holes being larger than the opening area of ​​the first through holes; Each of the first through holes is connected to the second through hole.

2. The porous liquid-absorbing core according to claim 1, characterized in that, The first through hole is an equilateral triangle.

3. The porous liquid-absorbing core according to claim 2, characterized in that, The second through hole is circular, and the diameter of the second through hole is not less than the circumcircle diameter of the first through hole.

4. The porous liquid-absorbing core according to claim 2, characterized in that, The first through holes are arranged alternately along the circumferential direction; The second through hole is a parallelogram-shaped hole, and the projections of the two circumferentially adjacent first through holes along the preset liquid supply direction are both within the second through hole.

5. The porous liquid-absorbing core according to claim 2, characterized in that, The side length of the first through hole is 0.19~0.26mm, the inner corner radius does not exceed 5% of the side length, and the minimum wall thickness between adjacent first through holes is 0.05~0.15mm.

6. The porous liquid-absorbing core according to claim 1, characterized in that, The opening area of ​​the second through hole is 2.0 to 3.5 times the opening area of ​​the first through hole, and the length of the capillary reinforcement layer (1) along the preset liquid supply direction is 40% to 60% of the length of the porous liquid suction core along the preset liquid supply direction.

7. A method for preparing a layered gradient porous liquid-absorbing core, used to prepare a porous liquid-absorbing core as described in any one of claims 1 to 6, characterized in that, The process employs laser selective melting technology to form a single piece, including: We provide stainless steel powder with a particle size of 15~53 µm and an oxygen content of no more than 0.02%; Under laser power of 60~150 W, scanning speed of 1200~1850 mm / s, scanning spacing of 0.13~0.22 mm, and powder layer thickness of 20~40 µm, the powder is melted and deposited layer by layer in a vertical or inclined at 30°±5° relative to the vertical direction. The scanning strategy employs outer contour scanning combined with staggered filling, with adjacent layers scanning directions interleaved.

8. The preparation method according to claim 7, characterized in that, The stainless steel powder is spherical powder of 316 or 316L stainless steel.

9. The preparation method according to claim 7, characterized in that, When forming the capillary reinforcement layer (1), an outer contour scan combined with staggered filling is used.

10. The application of a layered gradient porous wick in a heat pipe, a loop heat pipe, or a vapor chamber, wherein the porous wick is the porous wick as described in any one of claims 1 to 6, characterized in that, The capillary reinforcement layer (1) is located on the evaporation end side, and the permeation resistance reduction layer (2) is located on the condensation end side.

Images