A self-supporting channel heat pipe based on laser selective melting and its preparation method

Abstract

The present invention belongs to the field of heat transfer technology, and discloses a self-supporting grooved heat pipe based on laser selective melting and a preparation method thereof, wherein the self-supporting grooved heat pipe based on laser selective melting includes a heat pipe body, a circular tube with closed ends and a hollow cavity inside, a plurality of grooves are provided on the inner wall of the hollow cavity of the heat pipe body, and a groove with capillary effect is formed between two adjacent groups of grooves. It is characterized in that when the heat pipe body is placed horizontally, the hollow cavity includes an upper cavity area located above and a lower cavity area located below the upper cavity area, and the angle between the inclined surface of the groove teeth located in the upper cavity area and the horizontal direction of the position of the groove teeth is 45°-55°, so that self-support is formed by layer-by-layer stacking molding technology; the self-supporting grooved heat pipe improves the problem of poor forming effect of overhanging structure in the process of manufacturing heat pipes using additive manufacturing.

Description

Technical Field

[0001] The present invention relates to the field of heat transfer technology, and in particular to a self-supporting channel-type heat pipe based on selective laser melting and a preparation method thereof. Background Art

[0002] A heat pipe is a highly efficient thermal management device that utilizes the principle of phase change heat transfer and is widely used in electronic equipment, spacecraft, and industrial systems. Its core structure consists of a sealed tube body and an internal working fluid. The working fluid absorbs heat in the evaporation zone and turns into vapor. The heat is then transferred to the condensation zone through gas flow. In the condensation zone, the vapor condenses into liquid and releases heat. The liquid then returns to the evaporation zone through capillary action or gravity. This process can achieve extremely low thermal resistance and improve heat conduction efficiency. Heat pipe technology has become a key component of modern thermal control technology due to its excellent thermal management performance and compact design. The heat transfer performance of a heat pipe mainly depends on the capillary capacity and permeability of the wick. The grooved wick structure has become a widely used wick structure due to its advantages such as light weight, non-deformation, and no contact thermal resistance.

[0003] The current manufacturing process for grooved wick heat pipes primarily involves wick fabrication, heat pipe assembly, filling, and sealing. Key to the manufacturing of the grooved wick is the production of the key wick, primarily through stamping and laser cutting. While traditional methods are simple, they have limited precision for micro-scale applications, result in long production cycles, and result in low material utilization. However, the development of additive manufacturing technology has provided new approaches to the fabrication of grooved heat pipes.

[0004] Due to the characteristics of additive manufacturing processing itself, overhanging structures are prone to deformation or sagging. This is because the material will be affected by gravity before it is completely solidified during the deposition process, resulting in inaccurate molding. If support structures are added. However, these support structures need to be removed after printing is completed. The removal process may cause damage to the finished product or leave defects, and the removal of the support structure may not be complete. The remaining support will affect the performance or appearance of the final product. Although laser selective melting technology has unique advantages for processing channel-type liquid-wick heat pipes, the problems that may arise in the processing of overhanging structures greatly affect the molding effect of the heat pipe. In response to this situation, it is urgent to propose a new self-supporting channel structure based on additive manufacturing processing to improve the poor processing effect on the overhanging part. Summary of the Invention

[0005] In response to the above defects or improvement needs of the prior art, the present invention provides a self-supporting channel-type heat pipe based on selective laser melting and a preparation method thereof, so as to improve the problem of poor forming effect of the overhanging structure in the process of manufacturing heat pipes using additive manufacturing.

[0006] To achieve the above objectives, according to one aspect of the present invention, a self-supporting channel-type heat pipe based on selective laser melting is provided, comprising a heat pipe body, a circular tube with closed ends and a hollow cavity therein, a plurality of grooves being provided on the inner wall of the hollow cavity of the heat pipe body, and a groove with a capillary effect being formed between two adjacent groups of grooves. The heat pipe body is characterized in that when the heat pipe body is placed horizontally, the hollow cavity comprises an upper cavity area located above and a lower cavity area located below the upper cavity area, the angle between the inclined surface of the groove teeth located in the upper cavity area and the horizontal direction of the position of the groove teeth is 45°-55°, and self-support is formed by layer-by-layer stacking molding technology.

[0007] Preferably, the angle between the groove teeth located in the lower cavity area and the horizontal direction where the groove teeth are located is between 45° and 90°.

[0008] Preferably, the top of the upper cavity area is in an arc structure to reduce gaseous flow resistance; the inner wall spacing of the upper cavity area gradually decreases toward the arc structure at the top, so that steam can flow in the upper cavity area.

[0009] Preferably, in a cross section of any heat pipe body, the grooves and the groove teeth are symmetrically distributed on both sides of the hollow cavity.

[0010] Preferably, the groove width of the groove teeth is 0.60-1.00 mm.

[0011] Preferably, the groove depth of the groove teeth is 0.80-1.20 mm.

[0012] To achieve the above objectives, according to one aspect of the present invention, a method for preparing a self-supporting channel-type heat pipe based on selective laser melting is provided. The self-supporting channel-type heat pipe is prepared by an additive manufacturing method, and specifically comprises the following steps:

[0013] S1 modeling, build the CAD model of the parts to be processed and obtain the STL format file;

[0014] S2 slicing, importing the STL format model file obtained in step S1 into the forming control device, slicing the model using dedicated software to obtain part contour information;

[0015] S3 plans the scanning path and sets the forming process parameters based on step S2;

[0016] S4 pre-powder, using a scraper or powder roller to spread a uniform layer of powder on the substrate or formed parts;

[0017] S5 forming, according to the graphic slice information obtained in step S2 and the forming parameters set in step S3, controlling the galvanometer to select and melt the metal powder to form a metallurgical bonded entity;

[0018] S6 spreads powder again and the laser beam scans; after the current layer is formed, the forming cylinder drops a layer thickness, and the powder feeding cylinder rises a certain distance to continue spreading powder, repeating steps S4 and S5 until the part processing is completed.

[0019] Preferably, the powder spreading thickness in step S4 is 0.1 mm.

[0020] Preferably, in step S6, the laser beam power is 200 W, the spot diameter is 0.08 mm, the scanning speed is 1400-3000 mm / s, and the scanning interval is 0.06-0.10 mm.

[0021] In general, the above technical solutions conceived by the present invention have the following beneficial effects compared with the prior art:

[0022] 1. The heat pipe of the present invention is manufactured using laser selective melting technology, which has a simple and feasible process, high material utilization, short processing cycle and good processing effect of micro-size structure. The heat pipe of the present invention changes the structure of the traditional channel-type liquid absorption core and improves the overhanging structure that is prone to deformation during processing, which is conducive to improving the forming effect of the heat pipe under the additive manufacturing process and thus improving the heat transfer efficiency of the heat pipe.

[0023] 2. The heat pipe of the present invention adopts a new channel structure design, which improves the forming effect through additive manufacturing technology and makes the design of the heat pipe shape more flexible and changeable.

[0024] 3. The heat pipe of the present invention changes the top structure of the upper cavity area of ​​the heat pipe, reduces the flow resistance of the gaseous working medium, and is beneficial to improving the circulation efficiency of the gaseous working medium when the heat pipe is working, thereby improving the heat transfer efficiency of the heat pipe. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a cross-sectional view of the self-supporting channel heat pipe of the present invention. Figure 1 .

[0026] Figure 2 This is a cross-sectional view of the self-supporting channel heat pipe of the present invention. Figure 2 .

[0027] Figure 3 It is a structural schematic diagram of the self-supporting channel type heat pipe of the present invention.

[0028] Figure 4 This is a schematic diagram of the cross-sectional structure of a traditional grooved heat pipe.

[0029] Figure 5 It is a schematic diagram of the cross-sectional structure of the self-supporting channel type heat pipe of the present invention.

[0030] Figure 6 It is a schematic diagram of the preparation method of the self-supporting channel type heat pipe of the present invention.

[0031] Figure 7 This is a schematic diagram of the overhang defect that occurs in the groove structure of the upper cavity area during the traditional slotted heat pipe laser selective melting process.

[0032] In the accompanying drawings: 1-heat pipe body, 2-groove, 3-groove teeth, 11-upper cavity area, 12-lower cavity area. DETAILED DESCRIPTION

[0033] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0034] Overhanging structural defects are a common problem in additive manufacturing (e.g. Figure 7 Overhangs are areas with insufficient or no support during printing, typically extending upward from the build platform or lower layers. Adding support structures is often used to correct this problem. However, due to the small and complex structure of the channel heat pipe, adding support structures and removing them later can easily damage the original heat pipe structure. Therefore, we opted to optimize the heat pipe's channel structure.

[0035] See also Figure 1 and Figure 3 The present invention provides a self-supporting channel-type heat pipe based on selective laser melting, comprising a heat pipe body 1, which is a circular tube with a hollow cavity formed therein and closed at both ends. A plurality of groove teeth 3 are provided on the inner wall of the hollow cavity of the heat pipe body 1, and grooves 2 with capillary action are formed between two adjacent groups of groove teeth 3. When the heat pipe body 1 is placed horizontally, the hollow cavity includes an upper cavity area 11 located above and a lower cavity area 12 located below the upper cavity area 11. The inclined surface of the groove teeth 3 located in the upper cavity area 11 forms an angle of 45°-55° with the horizontal direction of the position of the groove teeth 3, and the self-supporting structure is formed by layer-by-layer stacking molding technology.

[0036] When additive manufacturing non-linear or large heat pipes, the heat pipes need to be positioned horizontally for processing. Due to the small size of the slotted heat pipes, the added support structure is difficult to remove and can easily damage the original structure. This can easily cause defects in the top groove teeth of the upper chamber area during processing. To address this issue, the slot teeth of the upper chamber area of ​​the conventional slotted heat pipe are modified. The angle between the inclined surface of the groove teeth 3 in the upper chamber area 11 and the horizontal position of the groove teeth 3 is set to 45°-55°. Because the minimum tilt angle for self-supporting layer-by-layer stacking technology is generally 45°, when the tilt angle of the part structure is less than 45 degrees, there will be more "overhanging parts" during printing, that is, there is no direct support material below the printed layer. These overhanging parts cannot be stably formed during the melting process due to the influence of gravity and thermal stress, which can easily cause processing defects and affect the processing quality. If the groove tooth angle is too large, the actual volume of the channel will be reduced, thereby affecting the efficiency of liquid reflux. Therefore, based on comprehensive considerations, the angle between the inclined surface of the groove teeth 3 in the upper chamber area 11 and the horizontal position of the groove teeth 3 is set to 45°-55°.

[0037] The angle between the groove teeth 3 in the lower cavity area 12 and the horizontal direction where the groove teeth 3 are located is between 45° and 90°, and the specific value is selected according to actual needs; the top of the upper cavity area 11 is an arc structure to reduce the gas flow resistance; specifically, Figure 3 As shown, the angle between the inclined surface of the groove tooth 3 located in the upper cavity area 11 and the horizontal direction of the position of the groove tooth 3 is a, and the angle of a is 45°-55°; the angle between the groove tooth 3 located in the lower cavity area 14 and the horizontal direction of the position of the groove tooth 3 is b, and the angle of b is 45°-90°.

[0038] During the operation of the heat pipe, the working fluid is heated and vaporized, and is mainly concentrated in the upper chamber area 11 of the heat pipe. During operation, the working fluid flows from the heating end to the condensing end. During the flow, the gaseous working fluid will be subjected to friction between the pipe wall and the grooves, thereby generating flow resistance. Designing the top of the upper chamber area 11 as a smooth circular pipe wall can make the gaseous working fluid flow more smoothly, reduce the flow resistance of the gaseous working fluid, improve the working fluid circulation efficiency, and thus improve the working efficiency of the heat pipe. At the same time, the grooves 2 in the lower chamber area 12 produce capillary action, prompting the liquid working fluid to flow back from the condensing section to the heating end.

[0039] The inner wall spacing of the upper cavity area 11 gradually decreases toward the arc structure at the top, so that steam can flow in the upper cavity area 11; on the cross section of any heat pipe body 1, the grooves 2 and the groove teeth 3 are symmetrically distributed on both sides of the hollow cavity.

[0040] The groove width of the groove teeth 3 is 0.60-1.00mm, and the groove depth of the groove teeth 3 is 0.80-1.20mm. Small grooves with capillary action are formed between adjacent groove teeth. Due to the surface tension between the liquid working medium and the groove surface, the working medium can flow along the groove, thereby providing power for the internal circulation of the heat pipe.

[0041] During the laser selective melting process, the common groove heat pipe Figure 4 The ribs in area A can be processed well, while the ribs in area B are in a hanging state. During the processing, defects are easily formed due to insufficient powder support, such as Figure 7 As shown, it affects the final heat pipe forming effect. The self-supporting channel heat pipe based on laser selective melting in this embodiment is as follows Figure 5 As shown, area C is the solid part of the metal heat pipe during the laser selective melting process, and area D is the internal cavity part of the heat pipe. During the processing, since the angle a between the inclined surface of the groove tooth 3 located in the upper cavity area 11 and the horizontal direction of the position of the groove tooth 3 is 45°-55°, the suspended part of the upper layer relative to the lower layer of powder during the printing process is reduced, the metal solid part and the metal powder can form a more effective support for the processing layer, which can effectively improve the heat pipe forming effect.

[0042] The self-supporting channel-type heat pipe of the present invention changes the structure of the traditional channel-type liquid-absorbing core, improves the overhanging structure that is prone to deformation during processing, and is conducive to improving the forming effect of the heat pipe under the additive manufacturing process; the process is simple and feasible, with high material utilization, short processing cycle and good micro-size structure processing effect.

[0043] This embodiment adopts the additive manufacturing method to prepare the self-supporting channel heat pipe. The forming process of laser selective melting is as follows: Figure 6 As shown, the preparation method of a self-supporting channel-type heat pipe based on laser selective melting specifically includes the following steps:

[0044] S1 modeling: Create a CAD model of the part to be processed and convert the design model into STL format or other file formats suitable for additive manufacturing;

[0045] S2 slicing: importing the STL format model file obtained in step S1 into the forming control device, and slicing the model using dedicated software. The thickness of each slice determines the forming accuracy and provides the contour information of the model part for subsequent processing;

[0046] S3 plans the scanning path and sets the forming process parameters based on step S2;

[0047] S4 pre-powder, using a scraper or powder roller to lay a layer of powder with a thickness of tens of microns on the substrate or formed parts;

[0048] S5 forming, according to the graphic slice information obtained in step S2 and the forming parameters set in step S3, controlling the galvanometer to select and melt the metal powder to form a metallurgical bonded entity;

[0049] S6 spreads powder again and the laser beam scans; after the current layer is formed, the forming cylinder drops a layer thickness, and the powder feeding cylinder rises a certain distance to continue spreading powder, repeating steps S4 and S5 until the part processing is completed.

[0050] During the forming process, the parameters were set as follows: fixed laser power of 200 W, scanning speed of 1400-3000 mm / s, powder thickness of 0.1 mm, spot diameter of 0.08 mm, and scanning spacing of 0.06-0.10 mm.

[0051] It will be easily understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A self-supporting channel-type heat pipe based on laser selective melting, comprising a heat pipe body (1), the heat pipe body (1) being a circular tube with closed ends and a hollow cavity therein, a plurality of groove teeth (3) being provided on the inner wall of the hollow cavity of the heat pipe body (1), a groove (2) with a capillary effect being formed between two adjacent groups of groove teeth (3), characterized in that: When the heat pipe body (1) is placed horizontally, the hollow cavity comprises an upper cavity area (11) located above and a lower cavity area (12) located below the upper cavity area (11); the angle between the inclined surface of the groove teeth (3) located in the upper cavity area (11) and the horizontal direction of the position of the groove teeth (3) is 45°-55°, and self-support is formed by layer-by-layer stacking molding technology.

2. The self-supporting channel heat pipe based on selective laser melting according to claim 1, characterized in that: The angle between the inclined surface of the groove tooth (3) located in the lower cavity area (12) and the horizontal direction where the groove tooth (3) is located is between 45° and 90°.

3. The self-supporting channel heat pipe based on selective laser melting according to claim 1, characterized in that: The top of the upper cavity area (11) is in an arc structure to reduce gas flow resistance.

4. The self-supporting channel heat pipe based on selective laser melting according to claim 3, characterized in that: The inner wall spacing of the upper cavity area (11) gradually decreases toward the arc structure at the top, so that steam flows in the upper cavity area (11).

5. The self-supporting channel heat pipe based on selective laser melting according to claim 1, characterized in that: On the cross section of any heat pipe body (1), the grooves (2) and the groove teeth (3) are symmetrically distributed on both sides of the hollow cavity.

6. The self-supporting channel heat pipe based on selective laser melting according to claim 1, characterized in that: The groove width of the groove teeth (3) is 0.60-1.00 mm.

7. The self-supporting channel heat pipe based on selective laser melting according to claim 1, characterized in that: The groove depth of the groove teeth (3) is 0.80-1.20 mm.

8. A method for preparing a self-supporting channel-type heat pipe based on selective laser melting, characterized in that: The self-supporting channel-type heat pipe according to any one of claims 1 to 7 is prepared by an additive manufacturing method, which specifically comprises the following steps: S1 modeling, build the CAD model of the parts to be processed and obtain the STL format file; S2 slicing, importing the STL format model file obtained in step S1 into the forming control device, slicing the model using dedicated software to obtain part contour information; S3 plans the scanning path and sets the forming process parameters based on step S2; S4 pre-powder, using a scraper or powder roller to spread a uniform layer of powder on the substrate or formed parts; S5 forming, according to the graphic slice information obtained in step S2 and the forming parameters set in step S3, controlling the galvanometer to select and melt the metal powder to form a metallurgical bonded entity; S6 spreads powder again and the laser beam scans; after the current layer is formed, the forming cylinder drops a layer thickness, and the powder feeding cylinder rises a certain distance to continue spreading powder, repeating steps S4 and S5 until the part processing is completed.

9. The method for preparing a self-supporting channel-type heat pipe based on selective laser melting according to claim 8, wherein: The thickness of the powder in step S4 is 0.1 mm.

10. The method for preparing a self-supporting channel-type heat pipe based on selective laser melting according to claim 8, wherein: In step S6 , the laser beam power is 200 W, the spot diameter is 0.08 mm, the scanning speed is 1400-3000 mm / s, and the scanning interval is 0.06-0.10 mm.

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