High-performance low-thermal-resistance gradient heat pipe and manufacturing method thereof

Abstract

The invention discloses a high-performance low-thermal-resistance gradient heat pipe and a manufacturing method thereof. The high-performance low-thermal-resistance gradient heat pipe comprises a heat pipe body, a braided wire layer and a capillary structure layer. One end of each heat pipe is a large pipe, the other end of each heat pipe is a small pipe, and the joint of the large pipe and the small pipe is a gradually-changed slope; a braided wire layer is arranged in the middle of the bottom face of the heat pipe, and a capillary structure layer is arranged on the inner wall of the heat pipe. One side face of the braided wire layer is connected with the inner wall of the heat pipe, and the capillary structure layer is locally attached to and wraps the other side face, the upper face and the lower face of the braided wire layer. The capillary structure layer is of a porous structure formed by sintering copper powder. The manufacturing method is simple and convenient in manufacturing procedure, pipe wall damage caused by reaming of the outer diameter of the copper pipe is not needed, and a special stepped center rod (high in precision requirement and extremely easy to cause poor performance of the heat pipe due to slight abrasion) does not need to be manufactured according to the gradually-changed outer diameter during capillary structure manufacturing. And the inner part is of a composite structure (the copper wire and the copper powder), so that higher heat conduction performance and lower contact thermal resistance can be provided, and the overall heat conduction and heat exchange performance can be greatly improved.

Description

Technical Field

[0001] The invention relates to the field of heat pipe design, and more specifically to a high-performance low-thermal-resistance gradient heat pipe and a manufacturing method thereof. Background Art

[0002] The common thin tube structures and their disadvantages are as follows:

[0003] (1) Copper mesh + braided wire structure: Disadvantages: poor copper mesh adhesion, large contact thermal resistance, poor copper wire adhesion and weak capillary force;

[0004] (2) Single and double trimmed copper powder structure: Disadvantages: The performance of pure copper powder is relatively low, the resistance to gravity is extremely poor, and the contact thermal resistance is relatively large;

[0005] (3) Full copper powder + copper wire structure: Disadvantages: limited by space, thin copper wire thickness and weak performance, large working fluid reflux resistance, suitable for heat pipes with T ≥ 2.0 mm.

[0006] (4) Due to the limited internal space of the computer and the design limitations of the width and thickness of the local area, large diameter heat pipes cannot be used, and small diameter heat pipes cannot meet the requirements of thermal resistance and power.

[0007] (5) The current conventional manufacturing method of gradient heat pipes is: a large diameter heat pipe is shrunk into a small diameter in a local area of ​​a mold, or a small diameter heat pipe is expanded into a large diameter and then a capillary structure is manufactured. The disadvantages are: the wall thickness of the expanded diameter is uneven and easy to break, the capillary manufacturing requires a special stepped core rod, the core rod size requires high precision, the powder thickness is easy to be uneven, especially the powder layer is easy to crack at the gradual change of large and small diameters, and the copper wire and copper mesh cannot fit tightly to the pipe wall, which seriously affects the performance. Summary of the invention

[0008] In order to overcome the above defects of the prior art, the present invention provides a high-performance low thermal resistance gradient heat pipe and its manufacturing method. The local area is enlarged in diameter while the diameter of the rest of the heat pipe remains unchanged to avoid mechanical interference, thereby achieving the effect of reducing thermal resistance, improving performance and enhancing heat dissipation.

[0009] The technical solution of the present invention is as follows:

[0010] On one hand, the present invention provides a high-performance, low-thermal-resistance gradient heat pipe and a manufacturing method thereof, comprising a heat pipe, a braided wire layer, and a capillary structure layer; one end of the heat pipe is a large tube, the other end is a small tube, and the connection between the large tube and the small tube is a gradient slope; a braided wire layer is arranged at the center of the bottom surface of the heat pipe, and a capillary structure layer is arranged on the inner wall of the heat pipe; one side of the braided wire layer is connected to the inner wall of the heat pipe, and the capillary structure layer is partially attached to and coated on the other side and the upper and lower sides of the braided wire layer; the capillary structure layer is a porous structure formed by sintering copper powder.

[0011] The large tube is a heating part, and the small tube is a heat dissipation part.

[0012] The heat pipe is flat and hollow.

[0013] The braided wire layer extends from the heating portion of the heat pipe to the heat dissipation portion.

[0014] The capillary structure layer is sintered on the inner wall of the heat pipe, and the copper powder can be designed on one side or in a whole circle.

[0015] The capillary structure layer uses copper powder with a thickness of 0.20-0.50 mm and a mesh size of 100-150.

[0016] One end of the small tube is an arc-shaped curved tube.

[0017] Another aspect of the present invention provides a method for manufacturing a high-performance, low-thermal-resistance gradient heat pipe, comprising the following steps:

[0018] S1. Raw material cutting: Select appropriate raw materials according to the maximum outer diameter of the required gradient heat pipe, and cut the raw materials according to the designed length;

[0019] S2. Production of gas storage section - shrinking hard tube: Use shrinking head mold and high-speed rotation of the machine to push the cut raw materials into the gas storage section with a tapered small outer diameter, which is conducive to the later removal of non-condensable gas and sealing welding;

[0020] S3. The first capillary structure is the braided wire layer:

[0021] (31) The copper wire, i.e. the braided wire, is cut to the designed size and then placed in a baking oven for baking;

[0022] (32) Use a trimming mandrel, wrap one end of the braided wire around the tip of the mandrel and place it flat on the trimming surface, use the tip of the mandrel to bring the copper wire into the copper tube, and fix and press the copper wire with the mandrel to make it sintered and bonded better;

[0023] (33) Put the heat pipe with copper wire and the core rod into the sintering furnace for sintering so that the copper wire is tightly attached to the tube wall. The sintering temperature is 950±20°C. The furnace is pre-evacuated and filled with nitrogen and hydrogen mixed gas for sintering in a reducing atmosphere. The constant temperature time is 1.5 hours. After the first capillary structure is sintered, the adhesion of the copper wire is enhanced to provide the gradient heat pipe with high capillary force and anti-gravity characteristics.

[0024] S4. Manufacturing of the second capillary structure, i.e., the capillary structure layer:

[0025] (41) Take out the product after the first sintering and pull out the fixed core rod. The product is first rounded and straightened to increase the surface hardness;

[0026] (42) Copper powder ratio: Use 100-150 mesh and mix according to the proportion to enhance capillary force and improve heat conduction;

[0027] (43) Design the powder thickness according to the performance requirements and select the center rod. The copper powder needs to completely cover the first capillary copper wire structure. Insert the core rod into the copper tube and select the center rod with a crossbeam powder cup to keep it in the center of the copper tube. Fill in the proportioned copper powder and use a powder vibrator to vibrate and fill it up to ensure that the copper powder weight is within the design specifications.

[0028] (44) Put the copper tube filled with powder together with the core rod into a sintering furnace for sintering so that the copper powder is tightly attached to the tube wall and completely wraps the copper wire capillary structure. The sintering temperature is 980±10°C. The furnace is pre-evacuated and filled with nitrogen and hydrogen mixed gas for sintering in a reducing atmosphere. The constant temperature time is 2.5 hours. After the second capillary structure is sintered, the fine copper powder particles can provide strong capillaries and high thermal conductivity while increasing the contact area, enhancing heat exchange and reducing thermal resistance. The key core copper powder wraps the copper wire to make it fit tightly to prevent the copper wire from being thinned and broken when making a small outer diameter of a gradient heat pipe.

[0029] S5. Gradient tube size outer diameter processing:

[0030] (51) taking out the sintered product of the second capillary structure, and straightening and shaping it;

[0031] (52) Select a shrinking die according to the required diameter of the gradient tube, push the straightened and shaped product into a high-speed rotating die, and slightly strike the tube body through the small gap between the die and the tube wall to form the required gradient small outer diameter, and feed and shape it according to the designed length;

[0032] (53) After the gradual outer diameter processing is completed, the tail end is sealed and welded, and placed in a reduction furnace for reduction treatment according to the normal process;

[0033] S6. Gradient tube medium filling and internal vacuum treatment:

[0034] (61) Filling medium and primary degassing treatment: pre-vacuum pure water to remove gas, use a precision injection pump to fill the designed standard amount of water into the reduced heat pipe; place the heat pipe gas storage section deep into a vacuum pump machine for the first degassing treatment to achieve a certain vacuum degree inside;

[0035] (62) After the first degassing, the product is first placed in an oven for baking at a temperature of 180±20°C;

[0036] (63) The heat pipe after baking is subjected to secondary degassing. The product is vertically inserted into a heating mold so that the residual non-condensable gas inside is pushed to the gas storage section under the action of water vapor. The mold is pressed and sealed at the taper position. The head end gas storage section is completely cut off with a cutter to remove the gas so that the vacuum degree inside the heat pipe is further improved, thereby enhancing the thermal conductivity and temperature uniformity of the heat pipe and extending its service life.

[0037] S7. Bending, flattening, forming

[0038] Use an automatic bending machine to bend the product according to the design, and then use a hydraulic press to form and flatten it to form the required gradient heat pipe shape.

[0039] Technical effects and advantages of the present invention:

[0040] (1) Fine copper powder is conducive to heat conduction and heat exchange to reduce thermal resistance. At the same time, thin powder thickness ensures sufficient steam channels and reduces contact thermal resistance; it can effectively reduce the chip temperature; low thermal resistance, good power performance, and more stable process;

[0041] (2) Compared with the traditional powder + wire heat pipe, this design can use thicker and wider copper wire, that is, the braided wire layer, which has the function of working fluid reflux. At the same time, the gas-liquid separation design is adopted, and the capillary force and anti-gravity performance are greatly improved; it can provide higher thermal conductivity and lower contact thermal resistance, and the overall thermal conductivity and heat exchange performance are greatly improved;

[0042] (3) The steam space at the heat dissipation end is larger, the pressure drop is small, the temperature difference of the heat pipe is small, and there is no other capillary coverage, so the heat dissipation effect is better;

[0043] (4) The problem of braided sintering shedding has been solved. The copper powder in the heating area can effectively fix the braided wire to achieve better sintering adhesion.

[0044] (5) The capillary structures on the upper and lower surfaces of the heat pipe are in close contact, which reduces the steam carryover at the heating end and reduces the reflux resistance of the working fluid, making the heat conduction and heat exchange of the heat pipe better.

[0045] (6) There is no need to expand the outer diameter of the copper tube to cause damage to the tube wall, and the capillary structure does not need to be manufactured according to the gradual outer diameter. A special stepped center rod is also not required.

[0046] (7) The process is simple and convenient with high fault tolerance. The capillary structure has good adhesion and can be applied to thin tubes. The thermal resistance and anti-gravity performance of the same thickness are better.

[0047] (8) The braided wire is sintered in advance to have good adhesion to the tube wall, which greatly enhances the adhesion and capillary force, and improves the heat pipe performance and anti-gravity characteristics;

[0048] (9) Fine copper powder is sintered in two stages to enhance heat conduction, reduce thermal resistance and fix the braided wire to prevent it from falling off;

[0049] (10) After the capillary structure is manufactured, the process of rotating the shuttle into a gradient heat pipe is more convenient and simple, which solves the problems of capillary separation and cracking at the gradient position and the difficulty in processing the outer diameter of the gradient heat pipe;

[0050] (11) The size of the core rod used for the manufacture of the capillary structure is simpler and does not require a complex step-by-step design based on the gradually changing heat pipe diameter;

[0051] (12) The capillary structure design on the upper and lower surfaces of the heat pipe separates the gas-liquid channels to reduce steam carryover, lower reflux resistance and improve performance;

[0052] (13) This manufacturing method is simple and convenient. There is no need to expand the outer diameter of the copper tube to cause damage to the tube wall. The capillary structure does not need to be manufactured based on the gradient outer diameter to make a special stepped center rod (high precision requirements, slight wear can easily lead to poor heat pipe performance). The internal composite structure (copper wire + copper powder) can provide higher thermal conductivity and lower contact thermal resistance, and the overall thermal conductivity and heat transfer performance are greatly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 is a schematic diagram of the heat pipe as a whole;

[0054] Figure 2 for Figure 1 AA section view;

[0055] Figure 3 This is the layout diagram of braided wire layer 2;

[0056] Figure 4 The raw material after cutting;

[0057] Figure 5 This is a schematic diagram of the gas storage section after production;

[0058] Figure 6 This is a schematic diagram of the interior of the first capillary structure after manufacture;

[0059] Figure 7 This is a schematic diagram of the interior of the second capillary structure after manufacture;

[0060] Figure 8 This is the internal schematic diagram of the gradient tube after processing;

[0061] Fig. 9 This is the internal schematic diagram after liquid injection, primary degassing, baking, secondary degassing, and head welding;

[0062] Fig.10 This is the internal schematic diagram after molding;

[0063] Fig.11 for Figure 6 Schematic cross section of

[0064] Fig.12 for Figure 7 Schematic cross-section of . DETAILED DESCRIPTION

[0065] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0066] Embodiment 1

[0067] like Figures 1 to 3 A high-performance, low-thermal-resistance gradient heat pipe and a manufacturing method thereof are shown, comprising a heat pipe 1, a braided wire layer 2, and a capillary structure layer 3; one end of the heat pipe is a large tube 11, and the other end is a small tube 12, and the connection between the large tube and the small tube is a gradient slope 13; the large tube is a heating part 14, and the small tube is a heat dissipation part 15; a braided wire layer 2 is arranged at the center of the bottom surface of the heat pipe, and a capillary structure layer is sintered on the inner wall of the heat pipe; the right side of the braided wire layer 2 is sintered to the inner wall of the heat pipe 1, and the capillary structure layer 3 is partially attached to and coated on the outer top surface and two side surfaces of the braided wire layer; the capillary structure layer is a porous structure formed by sintering copper powder.

[0068] Furthermore, the heat pipe 1 is flat and hollow, and the hollow portion is the steam channel C.

[0069] Furthermore, the braided wire layer extends from the heating part to the heat dissipation part of the heat pipe.

[0070] Furthermore, the capillary structure layer is sintered on the inner wall of the heat pipe, and the copper powder can be designed to be on one side or in a whole circle.

[0071] Furthermore, the capillary structure layer uses copper powder with a thickness of 0.20-0.50 mm and a mesh size of 100-150.

[0072] Furthermore, one end of the small tube is an arc-shaped curved tube 16 .

[0073] Embodiment 2

[0074] Technical requirements:

[0075] (1) The first capillary structure, i.e. the capillary structure layer, uses copper powder with a thickness of 0.20-0.50 mm (which can reduce thermal resistance); the copper powder uses 100-150 mesh. If the copper powder is too thin, the process will be difficult and the powder filling will be uneven. If the copper powder is too thick, it will block the steam channel. The appropriate powder thickness should be selected according to the flattened thickness of the heat pipe. The copper powder filling width should cover the heating area; it is best to just cover it.

[0076] (2) The second capillary structure is the braided wire layer, which uses braided wire (copper wire); the braided wire is designed to have a thickness that separates the gas path from the water path, reducing steam carryover at the heating end; and has a certain thickness to enhance the capillary lifting power and anti-gravity performance;

[0077] (3) The first capillary and the second capillary are in close contact on the upper and lower surfaces of the heat pipe heating area;

[0078] (4) The heat dissipation area only uses a braided wire capillary structure.

[0079] Embodiment 3

[0080] like Figure 4-Figure 10 A method for manufacturing a high performance low thermal resistance gradient heat pipe

[0081] S1. Raw material cutting: ( Figure 4 )

[0082] Select appropriate raw materials according to the maximum outer diameter of the required gradient heat pipe, and cut the raw materials according to the designed length (including the size of the gas storage end);

[0083] S2. Gas storage section production - shrink hard pipe: ( Figure 5 )

[0084] Use a conical shrinking die with grooves (the grooves are beneficial to the heat dissipation of the die), and use the high-speed rotation of the machine to push the cut raw materials into the gas storage section with a small outer diameter of the taper, which is beneficial to the later removal of non-condensable gas and sealing welding;

[0085] S3. First capillary structure manufacturing: ( Figure 6 )

[0086] (1) The copper wire is cut according to the designed size and placed in a baking oven for baking (to remove impurities and moisture in the incoming materials and oil stains during processing, enhance the flexibility, strength and stability of the copper wire, and make the copper wire closer to the tube wall);

[0087] (2) Use a trimming mandrel, wrap one end of the braided wire around the tip of the mandrel and place it flat on the trimming surface. Use the tip of the mandrel to bring the copper wire into the copper tube. The mandrel fixes and presses the copper wire to make it sintered and bonded better.

[0088] (3) Put the heat pipe with copper wire and the core rod into the sintering furnace for sintering so that the copper wire is tightly attached to the tube wall. The sintering temperature is 950±20°C. The furnace is pre-evacuated and filled with nitrogen and hydrogen mixed gas for sintering in a reducing atmosphere. The constant temperature time is 1.5 hours. After the first capillary structure is sintered, the adhesion of the copper wire is enhanced to provide the gradient heat pipe with high capillary force and anti-gravity characteristics.

[0089] S4. Second capillary structure manufacturing: ( Figure 7 )

[0090] (1) Take out the product after the first sintering and pull out the fixed core rod. The product is first rounded and straightened to increase the surface hardness.

[0091] (2) Copper powder ratio: Use 100-150 mesh and mix according to the proportion to enhance capillary force and improve heat conduction.

[0092] (3) Design the powder thickness according to the performance requirements and select the center rod. The copper powder needs to completely cover the first capillary copper wire structure. Insert the core rod into the copper tube and select the center rod with a crossbeam powder cup to keep it in the center of the copper tube. Fill in the proportioned copper powder and use a powder vibrator to vibrate and fill it up to ensure that the copper powder weight is within the design specifications.

[0093] (4) Put the copper tube filled with powder together with the core rod into the sintering furnace for sintering so that the copper powder is tightly attached to the tube wall and completely wraps the copper wire capillary structure. The sintering temperature is 980±10℃. The furnace is pre-evacuated and filled with nitrogen and hydrogen mixed gas for sintering in a reducing atmosphere. The constant temperature time is 2.5 hours. After the second capillary structure is sintered ( Figure 7 ), fine copper powder particles can provide strong capillary and high thermal conductivity while increasing the contact area, enhancing heat exchange and reducing thermal resistance. The key core copper powder wraps the copper wire to make it fit tightly to prevent the copper wire from being pulled thin and broken when making a small outer diameter of a gradient heat pipe;

[0094] S5. Gradient tube size outer diameter processing: ( Figure 8 )

[0095] (1) taking out the product after sintering the second capillary structure, and straightening and shaping it;

[0096] (2) Select a shrinking die according to the required diameter of the gradient tube (the die adopts a four-piece arc-shaped point-shaped striking type, and the end through-hole size is the minimum diameter of the product - 3D as shown in the schematic diagram), push the rolled and straightened product into a high-speed rotating die, and slightly strike the tube body through the tiny gap between the die and the tube wall to form the required gradient small outer diameter, such as Figure 8 As shown in b, the molding is produced by feeding according to the designed length;

[0097] (3) After the gradual outer diameter processing is completed, the tail end a is sealed and welded, and then placed in a reduction furnace for reduction according to the normal process;

[0098] S6. Gradient tube medium filling and internal vacuum treatment: ( Fig. 9 )

[0099] (1) Filling medium and primary degassing treatment: Pre-vacuum pure water to remove gases (such as oxygen, carbon dioxide, etc.) and use a precision injection pump to fill the designed standard amount of water into the reduced heat pipe; Place the head end (heat pipe gas storage section) deep into a vacuum pump machine for the first degassing treatment to achieve a certain vacuum degree inside;

[0100] (2) After the primary degassing, the product is first placed in an oven for baking at a temperature of 180±20°C (the purpose is to make the non-condensable gas remaining in the copper tube move more actively after heating and gather more easily in the designated area (gas storage section));

[0101] (3) After baking, the heat pipe is degassed for the second time. The product is vertically inserted into a heating mold (temperature 140±20°C) so that the residual non-condensable gas inside is pushed to the gas storage section under the action of water vapor. The mold is pressed and sealed at the taper position. The head end gas storage section is completely cut off with a cutter to remove the gas and further improve the vacuum degree inside the heat pipe, thereby enhancing the thermal conductivity and temperature uniformity of the heat pipe and extending its service life.

[0102] S7. Bending, flattening, forming ( Fig.10 )

[0103] Use an automatic bending machine to bend the product according to the design (pay attention to the accuracy of the gradient position), and then use a hydraulic press to form and flatten it to form the required gradient heat pipe shape.

[0104] This manufacturing method is simple and convenient. There is no need to expand the outer diameter of the copper tube to cause damage to the tube wall. The capillary structure manufacturing also does not require the production of a special stepped center rod based on the gradual outer diameter (high precision requirements, slight wear can easily lead to poor heat pipe performance), and the internal composite structure (copper wire + copper powder) can provide higher thermal conductivity and lower contact thermal resistance, greatly improving the overall thermal conductivity and heat exchange performance.

[0105] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A high performance, low thermal resistance gradient heat pipe, characterized in that: It comprises a heat pipe, a braided wire layer and a capillary structure layer; one end of the heat pipe is a large tube and the other end is a small tube, and the connection between the large tube and the small tube is a gradual slope; a braided wire layer is arranged at the center of the bottom surface of the heat pipe, and a capillary structure layer is arranged on the inner wall of the heat pipe; one side of the braided wire layer is connected to the inner wall of the heat pipe, and the capillary structure layer is partially attached to and covered on the other side and the upper and lower sides of the braided wire layer, and the heat pipe is flat and hollow.

2. A high performance, low thermal resistance gradient heat pipe according to claim 1, characterized in that: The large tube is a heating part, and the small tube is a heat dissipation part.

3. A high performance, low thermal resistance gradient heat pipe according to claim 1, characterized in that: The braided wire layer extends from the heating portion of the heat pipe to the heat dissipation portion.

4. The high performance and low thermal resistance gradient heat pipe according to claim 1, characterized in that: The capillary structure layer is sintered on the inner wall of the heat pipe, and the copper powder can be designed on one side or in a whole circle.

5. The high performance and low thermal resistance gradient heat pipe according to claim 1, characterized in that: The capillary structure layer uses copper powder with a thickness of 0.20-0.50 mm and a mesh size of 100-150.

6. The high performance and low thermal resistance gradient heat pipe according to claim 1, characterized in that: The capillary structure layer is a porous structure formed by sintering copper powder.

7. A method for manufacturing a high-performance, low-thermal-resistance gradient heat pipe, characterized in that: The following steps are involved: S1. Raw material cutting: Select appropriate raw materials according to the maximum outer diameter of the required gradient heat pipe, and cut the raw materials according to the designed length; S2. Production of gas storage section - shrinking hard tube: Use shrinking head mold and high-speed rotation of the machine to push the cut raw materials into the gas storage section with a tapered small outer diameter, which is conducive to the later removal of non-condensable gas and sealing welding; S3. The first capillary structure is the braided wire layer: (31) The copper wire, i.e. the braided wire, is cut to the designed size and then placed in a baking oven for baking; (32) Use a trimming mandrel, wrap one end of the braided wire around the tip of the mandrel and place it flat on the trimming surface, use the tip of the mandrel to bring the copper wire into the copper tube, and fix and press the copper wire with the mandrel to make it sintered and bonded better; (33) Put the heat pipe with copper wire and the core rod into the sintering furnace for sintering so that the copper wire is tightly attached to the tube wall. The sintering temperature is 950±20°C. The furnace is pre-evacuated and filled with nitrogen and hydrogen mixed gas for sintering in a reducing atmosphere. The constant temperature time is 1.5 hours. After the first capillary structure is sintered, the adhesion of the copper wire is enhanced to provide the gradient heat pipe with high capillary force and anti-gravity characteristics. S4. Manufacturing of the second capillary structure, i.e., the capillary structure layer: (41) Take out the product after the first sintering and pull out the fixed core rod. The product is first rounded and straightened to increase the surface hardness; (42) Copper powder ratio: Use 100-150 mesh and mix according to the proportion to enhance capillary force and improve heat conduction; (43) Design the powder thickness according to the performance requirements and select the center rod. The copper powder needs to completely cover the first capillary copper wire structure. Insert the core rod into the copper tube and select the center rod with a crossbeam powder cup to keep it in the center of the copper tube. Fill in the proportioned copper powder and use a powder vibrator to vibrate and fill it up to ensure that the copper powder weight is within the design specifications. (44) Put the copper tube filled with powder together with the core rod into a sintering furnace for sintering so that the copper powder is tightly attached to the tube wall and completely wraps the copper wire capillary structure. The sintering temperature is 980±10°C. The furnace is pre-evacuated and filled with nitrogen and hydrogen mixed gas for sintering in a reducing atmosphere. The constant temperature time is 2.5 hours. After the second capillary structure is sintered, the fine copper powder particles can provide strong capillaries and high thermal conductivity while increasing the contact area, enhancing heat exchange and reducing thermal resistance. The key core copper powder wraps the copper wire to make it fit tightly to prevent the copper wire from being thinned and broken when making a small outer diameter of a gradient heat pipe. S5. Gradient tube size outer diameter processing: (51) taking out the sintered product of the second capillary structure, and straightening and shaping it; (52) Select a shrinking die according to the required diameter of the gradient tube, push the straightened and shaped product into a high-speed rotating die, and slightly strike the tube body through the small gap between the die and the tube wall to form the required gradient small outer diameter, and feed and shape it according to the designed length; (53) After the gradual outer diameter processing is completed, the tail end is sealed and welded, and placed in a reduction furnace for reduction treatment according to the normal process; S6. Gradient tube medium filling and internal vacuum treatment: (61) Filling medium and primary degassing treatment: pre-vacuum pure water to remove gas, use a precision injection pump to fill the designed standard amount of water into the reduced heat pipe; place the heat pipe gas storage section deep into a vacuum pump machine for the first degassing treatment to achieve a certain vacuum degree inside; (62) After the first degassing, the product is first placed in an oven for baking at a temperature of 180±20°C; (63) The heat pipe after baking is subjected to secondary degassing. The product is vertically inserted into a heating mold so that the residual non-condensable gas inside is pushed to the gas storage section under the action of water vapor. The mold is pressed and sealed at the taper position. The head end gas storage section is completely cut off with a cutter to remove the gas so that the vacuum degree inside the heat pipe is further improved, thereby enhancing the thermal conductivity and temperature uniformity of the heat pipe and extending its service life. S7. Bending, flattening, forming Use an automatic bending machine to bend the product according to the design, and then use a hydraulic press to form and flatten it to form the required gradient heat pipe shape.

8. The high performance and low thermal resistance gradient heat pipe according to claim 1, characterized in that: In the step (31), baking is performed to remove impurities and moisture in the incoming materials as well as oil stains generated during the processing, thereby enhancing the flexibility, strength and stability of the copper wire and making the copper wire adhere more closely to the tube wall.

9. The high performance and low thermal resistance gradient heat pipe according to claim 1, characterized in that: In the step (63), the temperature of the heating mold into which the product is vertically inserted is 140±20°C.

Images