Variable capillary heat pipe structure and additive manufacturing method

Abstract

The invention discloses a variable capillary heat pipe structure and an additive manufacturing method, and relates to the field of lightweight multifunctional structures.The variable capillary heat pipe structure comprises a heat pipe outer wall, a heat pipe inner wall and a heat pipe inner wall, the internal capillary core is connected to the inner wall of the heat pipe outer wall, and a cavity is formed in the center of the section of the internal capillary core and forms a middle cavity in the length direction; the internal capillary core comprises n sections of capillary core structures in the length direction of the internal capillary core, n is equal to the number of loads with different heat flow densities connected with the heat pipe, and the thicknesses, pore sizes and / or porosities of the different sections of capillary core structures are different. The heat capacity and the heat transfer speed of the working medium at different positions are changed, and adaptive regulation and control of the heat transfer capacity of the heat pipe at different positions are achieved.

Description

Technical Field

[0001] The present invention relates to a variable capillary heat pipe structure and an additive manufacturing method, belonging to the technical field of lightweight multi-functional structures. Background Art

[0002] The new generation of spacecraft is developing towards the direction of multi-functional integration. A variety of payloads need to be deployed in the spacecraft simultaneously. During the operation of the payloads, a large amount of instantaneous heat energy is generated, and the thermal control components are required to transfer the heat energy quickly and effectively in a limited space and time. This process is directly related to the working efficiency of the payloads. The heat generated by the payloads varies according to different working modes. High heat flux payloads have higher heat dissipation requirements compared to low heat flux payloads and need to transfer heat to the heat sink end more quickly. However, the heat pipe often passes through multiple payloads with different heat flux densities in sequence. When using traditional heat pipes, it is necessary to design according to the maximum heat flux density value in the payloads, resulting in waste of resources in the thermal control system.

[0003] Traditional heat pipes are usually Ω-shaped channel heat pipes, which are prepared by the drawing method. The channel size and shape of the heat pipe are fixed and cannot be changed. Therefore, the heat dissipation capabilities of the heat pipes developed in this way do not vary at different positions.

[0004] The variable capillary heat pipe structures based on selective laser melting (SLM) mainly include porous capillary structures and micro-lattice capillary structures. The porous capillary structure is formed by laser non-dense sintering to construct a porous capillary structure inside the material, and the pore size and quantity can be adjusted by adjusting process parameters. The micro-lattice capillary structure forms a capillary structure using the gaps between lattice rods, and the capillary characteristics can be precisely controlled through structural design. Both of these capillary structures can obtain variable capillary heat pipe structures through parametric design and forming process control to meet the different heat dissipation requirements at different positions of the heat pipe. Adopting the variable capillary heat pipe structure based on SLM forming is an effective technical approach to meet the above requirements. Summary of the Invention

[0005] The technical problem solved by this application is: overcoming the deficiencies of the prior art, providing a variable capillary heat pipe structure and an additive manufacturing method, so that payloads with different heat flux densities can all be stably at their required temperatures and meet the heat transfer requirements of different payloads in different regions.

[0006] Furthermore, realizing the integrated manufacturing of complex and fine features of the product.

[0007] The technical solution provided by this application is as follows:

[0008] A variable capillary heat pipe structure, the heat pipe is connected with multiple payloads with different heat flux densities along its own length direction, including:

[0009] The outer wall of the heat pipe forms a closed structure with a hollow interior;

[0010] An internal capillary wick is connected to the inner wall of the outer wall of the heat pipe. The central position of its cross-section is a cavity, forming an intermediate cavity along the length direction. The internal capillary wick includes n capillary wick structures along its own length direction, where n = the number of loads with different heat flux densities connected to the heat pipe, and the thickness, pore size, and / or porosity of different sections of the capillary wick structures are different.

[0011] Further, the internal capillary wick is a lattice capillary wick, and the lattice capillary wick is formed by sequentially connecting a plurality of unit cells.

[0012] Further, the size of the unit cell is 2 mm to 4 mm, the rod diameter of the unit cell is 0.4 to 1 mm, the pore size formed by the unit cell is 15 μm to 100 μm, and the porosity is 20% to 80%.

[0013] Further, the greater the heat flux density of the load connected by the capillary wick structure, the greater the thickness of the capillary wick structure, the smaller the pores, and the greater the porosity; when the load heat flux density is greater than 0.2 W / cm 2 At this time, the thickness of the capillary wick should not be less than 4 mm, the pores should not be greater than 60 μm, and the porosity should not be less than 50%.

[0014] Further, the SLM forming process parameters of the lattice capillary wick are: scanning speed 800 mm / s to 1600 mm / s, scanning spacing 0.08 to 0.12 mm, and laser power 280 W to 400 W.

[0015] Further, the internal capillary wick is a sponge capillary wick, and the porosity of the sponge capillary wick is 15 to 30%.

[0016] Further, the greater the heat flux density of the load connected by the capillary wick structure, the greater the thickness of the capillary wick structure and the greater the porosity; when the load heat flux density is greater than 0.1 W / cm 2 At this time, the thickness of the capillary wick should not be less than 6 mm, and the porosity should not be less than 20%.

[0017] Further, the sponge capillary wick is formed by SLM non-dense sintering; the SLM forming laser energy density of the sponge capillary wick is 20% to 40% of the SLM forming laser energy density of the lattice capillary wick.

[0018] An additive manufacturing method for a variable capillary heat pipe structure includes:

[0019] S1: According to the SLM forming process parameters of the lattice wick, form the lattice wick structure; by adjusting the SLM laser energy density to 20% - 40% of the SLM forming laser energy density of the lattice wick, obtain the sponge wick structure; through capillary force testing, establish a database of the relationship between the pore characteristics of different capillary structures and physical property parameters such as capillary force and permeability.

[0020] S2: Based on the mass transfer mathematical model, combined with the spatial layout mode of the product load, calculate the optimal matching scheme of capillary force and permeability at different mass transfer distances, and realize the variable-capillary design of the capillary wick in the heat pipe lumen.

[0021] S3: Based on finite element simulation analysis, according to the heat transfer requirements, design the heat pipe wall thickness, the inner diameter of the heat pipe lumen, the wick thickness, and the gas channel diameter, and complete the integrated design of the variable-capillary heat pipe and the structural plate.

[0022] S4: Based on the SLM forming process in step 1, form the heat pipe.

[0023] Further, the SLM forming process parameters of the lattice wick are: scanning speed 800mm / s - 1600mm / s, scanning spacing 0.08 - 0.12mm, and laser power 280W - 400W.

[0024] Through the variable-capillary structure design at different positions along the length direction of the heat pipe, which mainly includes the design of macroscopic parameters and capillary parameters. Macroscopic parameters such as the heat pipe wall thickness, the inner diameter of the heat pipe lumen, and the wick thickness can change the heat capacity of the liquid working medium; capillary parameters such as the cell configuration, cell size, and rod diameter of the lattice wick determine the porosity and pore size of the wick, and then change the transmission speed and permeability of the liquid working medium under the action of capillary force. Therefore, through the variable-capillary structure design of the above macroscopic parameters and capillary parameters, the heat capacity and heat transfer speed of the working medium at different positions are changed, and the adaptive regulation of the heat transfer capacity of the heat pipe at different positions is realized.

[0025] In summary, the present application at least includes the following beneficial technical effects:

[0026] Through the variable-capillary structure design, the regulation of porosity, pore size, and shape size is realized to meet the heat transfer requirements of different loads in different regions. Description of the Drawings

[0027] Figure 1 This is the variable-capillary heat pipe structure of the present invention.

[0028] Among them, 1 - outer wall of the heat pipe, 2 - internal wick, 3 - cross-section of the thick lattice wick, 4 - cross-section of the thick sponge wick, 5 - cross-section of the fine lattice wick, 6 - cross-section of the fine sponge wick, 7 - intermediate cavity, 8 - cell structure. Detailed implementation manners

[0029] To make the objectives, technical solutions and advantages of the present invention clearer, the disclosed implementation manners of the present invention will be further described in detail below with reference to the accompanying drawings.

[0030] An embodiment of the present application discloses a variable capillary heat pipe structure, as Figure 1 shown, which includes: a heat pipe outer wall 1, an internal capillary core 2, and an intermediate cavity 7. The heat pipe outer wall 1 is generally formed into a closed structure by a skin with a thickness of 1.0 - 1.5 mm to keep the vapor-liquid working medium inside the heat pipe from leaking during long-term operation. The function of the internal capillary core 2 is to contain the liquid working medium and make the liquid working medium transfer to the distal end under capillary action. The inner cavity of the heat pipe is the gas channel after the evaporation of the liquid working medium.

[0031] The internal capillary core 2 includes n sections of capillary core structures along its own axis direction, where n is determined according to the number of loads with different heat flux densities connected to the heat pipe. Specifically, n = the number of loads with different heat flux densities connected to the heat pipe. The thickness, pore size, and / or porosity of the capillary core structures in different sections are different. Through the above settings, the heat pipe has an adaptable heat transfer capacity in different parts, so that it has a faster heat conduction / dissipation effect for loads with different heat flux densities.

[0032] The internal capillary core 2 can be of two types. The first type is a lattice capillary core, formed by SLM under normal process parameters. Typical cell configurations are BCC, BCC-Z, Dodecahedron, BCC-ZH, BCC-H, etc. The cell size varies from 2 mm to 4 mm, the cell rod diameter varies from 0.4 to 1 mm, the formed pore size varies from 15 μm to 100 μm, and the porosity varies from 20% to 80%. As Figure 1 shown in a certain typical cell structure 8, and the cross-section 3 of the thick lattice capillary core and the cross-section 5 of the thin lattice capillary core are shown. In this embodiment, the heat pipe is connected to three loads with different heat flux densities from left to right. The heat flux densities of the loads from left to right are 0.6 W / cm 2 、0.25 W / cm 2 、0.12 W / cm 2, the internal capillary wick 2 from left to right is divided into three sections. The leftmost section of the unit cell is 4 mm in size, the rod diameter is 0.4 mm, the pore size formed is 30 μm, and the porosity is 80%; the middle section of the unit cell is 3 mm in size, the rod diameter is 0.5 mm, the pore size formed is 24 μm, and the porosity is 60%; the rightmost section of the unit cell is 2 mm in size, the rod diameter is 1 mm, the pore size formed is 15 μm, and the porosity is 20%. The second type of capillary wick is a sponge capillary wick, which is formed by non-dense sintering of a solid model through SLM. The SLM laser energy density of non-dense sintering is 20% - 40% of the normal forming laser energy density, and the porosity of the obtained sponge capillary wick is 15 - 30%. As Figure 1 shows the cross-section 4 of the thick sponge capillary wick and the cross-section 6 of the thin sponge capillary wick.

[0033] For the lattice capillary wick, the greater the heat flux density of the load connected by the capillary wick structure of a certain segment, the greater the thickness, the smaller the pores, and the greater the porosity of the capillary wick structure. The general relationship is: for example, when the load heat flux density is greater than 0.2 W / cm 2 , the thickness of the capillary wick should be not less than 4 mm, the pores should be not greater than 60 μm, and the porosity should be not less than 50%. For the sponge capillary wick, the greater the heat flux density of the load connected by the capillary wick structure of a certain segment, the greater the thickness and the greater the porosity of the capillary wick structure. The general relationship is: for example, when the load heat flux density is greater than 0.1 W / cm 2 , the thickness of the capillary wick should be not less than 6 mm, and the porosity should be not less than 20%.

[0034] The technical principle is as follows: The heat pipe is in close contact with the heat-generating component. The heat of the heat-generating component is conducted through the outer wall 1 of the heat pipe to the liquid working medium contained in the internal capillary wick 2. The liquid heat control working medium absorbs the heat and evaporates into a gas. The gaseous heat control working medium gathers in the inner cavity of the heat pipe and flows towards the low-temperature area at the far end under the action of the pressure difference, and condenses into a liquid at the far end upon cooling. The liquid flows back towards the heat source under the capillary action of the internal capillary wick 2, forming an internal circulation of the heat control working medium and conducting away the heat. Through the variable capillary structure design at different axial positions of the heat pipe, which mainly includes the design of macroscopic parameters and capillary parameters. The macroscopic parameters such as the wall thickness of the heat pipe, the inner cavity diameter of the heat pipe, and the thickness of the capillary wick are used to change the heat capacity of the liquid working medium. Typically, the wall thickness of the heat pipe is 1.0 - 1.5 mm, the inner cavity diameter of the heat pipe is 6 - 8 mm, the thickness of the capillary wick is 2 - 4 mm, and the diameter of the gas channel is 2 - 3 mm. For example, the larger the inner cavity diameter of the heat pipe and the thickness of the capillary wick, the greater the load heat power consumption that can be served. The capillary parameters such as the cell configuration, cell size, and rod diameter of the lattice capillary wick determine the porosity and pore size of the capillary wick, and thus change the transmission speed and permeability of the liquid working medium under the action of capillary force. Therefore, through the variable capillary structure design of the above macroscopic parameters and capillary parameters, the heat capacity and heat transfer speed of the working medium at different positions are changed, realizing the adaptive regulation of the heat transfer capacity of the heat pipe at different positions.

[0035] An additive manufacturing method for a variable capillary heat pipe structure specifically includes:

[0036] Step 1: Based on the SLM forming process, form a typical capillary wick structure. The SLM forming process parameters are: scanning speed (800 mm / s - 1600 mm / s), scanning spacing (0.08 - 0.12 mm), laser power (280 W - 400 W), to form a lattice capillary wick; by adjusting the SLM laser energy density (laser power / (scanning speed × scanning spacing)) to 20% - 40% of normal forming, a sponge capillary wick based on non-dense sintering is obtained. Through capillary force testing, establish a database of the relationship between the pore characteristics of different capillary structures and physical property parameters such as capillary force and permeability;

[0037] Step 2: Based on the mass transfer mathematical model, combined with the spatial layout of the product load, calculate the optimal matching scheme of capillary force and permeability at different mass transfer distances to realize the variable capillary design of the capillary wick in the inner cavity of the heat pipe;

[0038] Step 3: Based on finite element simulation analysis, design the wall thickness of the heat pipe, the inner cavity diameter of the heat pipe, the thickness of the capillary wick, and the diameter of the gas channel according to the heat transfer requirements, and complete the integrated design of the variable capillary heat pipe and the structural plate;

[0039] Step 4: Based on the SLM forming process in Step 1, complete the manufacturing of the thermal control - structure integrated product; perform cleaning and leak detection on the inside of the heat pipe (leak rate < 10 -8Conventional processes such as (Pa.s) and working fluid filling;

[0040] Step 5: Install a load simulation component to verify the uniform temperature performance of the variable capillary heat pipe.

[0041] The content not described in detail in the specification of this application belongs to the well-known technology of those skilled in the art.

[0042] The above has described this application in detail in combination with specific embodiments and exemplary examples, but these descriptions should not be construed as limitations on this application. Those skilled in the art understand that without departing from the spirit and scope of this application, various equivalent replacements, modifications or improvements can be made to the technical solutions of this application and their implementation manners, and these all fall within the scope of this application. The protection scope of this application shall be subject to the appended claims.

Claims

1. A variable capillary heat pipe structure, wherein the heat pipe is connected with a plurality of loads with different heat flux densities along its own length direction, and is characterized in that Comprising: The outer wall (1) of the heat pipe, forming a closed structure with a hollow interior; An internal capillary wick (2), connected to the inner wall of the outer wall (1) of the heat pipe, with a cavity at the center of its cross-section, forming an intermediate cavity (7) along the length direction; the internal capillary wick (2) includes n sections of capillary wick structures along its own length direction, where n = the number of loads with different heat flux densities connected to the heat pipe, and the thickness, pore size, and / or porosity of the capillary wick structures in different sections are different.

2. The variable capillary heat pipe structure according to claim 1, wherein: The internal capillary wick (2) is a lattice capillary wick, and the lattice capillary wick is formed by sequentially connecting multiple unit cells.

3. The variable capillary heat pipe structure according to claim 2, characterized in that: The size of the unit cell is 2 mm to 4 mm, the rod diameter of the unit cell is 0.4 to 1 mm, the pore size formed by the unit cell is 15 μm to 100 μm, and the porosity is 20% to 80%.

4. The variable capillary heat pipe structure according to claim 2, wherein: The greater the heat flux density of the load connected by the capillary wick structure, the greater the thickness, the smaller the pore size, and the greater the porosity of the capillary wick structure; when the load heat flux density is greater than 0.2 W / cm 2 ², the thickness of the capillary wick should be not less than 4 mm, the pore size should be not greater than 60 μm, and the porosity should be not less than 50%.

5. A variable capillary heat pipe structure according to claim 2, characterized in that: The SLM forming process parameters of the lattice capillary wick are: scanning speed 800 mm / s to 1600 mm / s, scanning spacing 0.08 to 0.12 mm, and laser power 280 W to 400 W.

6. The variable capillary heat pipe structure according to claim 1, characterized in that: The internal capillary wick (2) is a sponge capillary wick, and the porosity of the sponge capillary wick is 15 to 30%.

7. A variable capillary heat pipe structure according to claim 6, characterized in that: The greater the heat flux density of the load connected by the capillary core structure, the greater the thickness and porosity of the capillary core structure; when the load heat flux density is greater than 0.1 W / cm 2 ², the thickness of the capillary core should be not less than 6 mm and the porosity should be not less than 20%.

8. A variable capillary heat pipe structure according to claim 6, characterized in that: The sponge capillary wick is formed by SLM non-dense sintering; the SLM forming laser energy density of the sponge capillary wick is 20% to 40% of the SLM forming laser energy density of the lattice capillary wick.

9. The additive manufacturing method of a variable capillary heat pipe structure according to claim 1, characterized in that, Comprising: S1: According to the SLM forming process parameters of the lattice capillary wick, form the lattice capillary wick structure; By adjusting the SLM laser energy density to 20% to 40% of the SLM forming laser energy density of the lattice capillary wick, obtain the sponge capillary wick structure; through capillary force testing, establish a database of the relationship between the pore characteristics of different capillary structures and physical property parameters such as capillary force and permeability; S2: Based on the mass transfer mathematical model, combined with the spatial layout of the product load, calculate the optimal matching scheme of capillary force and permeability at different mass transfer distances, and realize the variable capillary design of the capillary wick in the inner cavity of the heat pipe; S3: Based on finite element simulation analysis, according to the heat transfer requirements, design the heat pipe wall thickness, the inner cavity diameter of the heat pipe, the capillary wick thickness, and the gas channel diameter, and complete the integrated design of the variable capillary heat pipe and the structural plate; S4: Based on the SLM forming process in step 1, form the heat pipe.

10. An additive manufacturing method for a variable capillary heat pipe structure according to claim 9, wherein the SLM forming process parameters of the lattice capillary wick are: scanning speed 800 mm / s to 1600 mm / s, scanning spacing 0.08 to 0.12 mm, and laser power 280 W to 400 W.

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