Heat pipe with asymmetrically sintered wick and preparation process of heat pipe

Abstract

The invention relates to the field of heat pipes, and discloses a heat pipe with an asymmetrically sintered wick and a preparation process of the heat pipe. A heat pipe with an asymmetrically sintered wick comprises a pipe shell and the wick, the wick is annularly arranged, a steam area is defined by the inner wall of the wick, and the thickness of the wick wall of the wick is gradually increased from the two sides of the top of the wick to the bottom of the wick; the liquid absorbing core is prepared by sintering copper powder, the liquid absorbing core is composed of a first liquid absorbing part and a second liquid absorbing part, the first liquid absorbing part corresponds to the top area of the tube shell and corresponds to the position above the median line of the steam area, and the second liquid absorbing part corresponds to the bottom area of the tube shell and corresponds to the position below the median line of the steam area; the particle size of the copper powder of the first liquid absorption part is smaller than that of the copper powder of the second liquid absorption part. According to the heat pipe, the liquid absorption core is arranged in an offset mode, and the copper powder with different particle sizes is distributed, so that the heat pipe has the low heat resistance, meanwhile, the high liquid supply rate of the liquid absorption core is achieved, and the overall heat dissipation efficiency is high.

Description

Technical Field

[0001] The present application relates to the field of heat pipes, and more particularly, to a heat pipe with an asymmetric sintered wick and a preparation process thereof. Background Art

[0002] With the continuous advancement of technology, electronic devices are moving towards higher density, miniaturization, and integration. This has led to a dramatic increase in chip heat flux density, making heat dissipation a particularly prominent issue. Air cooling has long been widely used for electronic device heat dissipation due to its simple structure and high reliability. As a key component of air-cooled heat sinks, improving the heat transfer performance of heat pipes plays a significant role in enhancing their heat dissipation capabilities.

[0003] A heat pipe consists of a tube, a wick, and end caps. Negative pressure is applied to the tube and the tube is filled with liquid. Once the wick is full of liquid, it is sealed. One end of the tube is the evaporation section, and the other is the condensation section. When one end of the heat pipe is heated, the liquid in the wick evaporates and vaporizes. Under the pressure differential, the vapor flows along the vapor zone to the other end, releasing heat and condensing into liquid. The liquid then flows back to the evaporation section along the wick due to capillary forces, thus dissipating heat.

[0004] Thermal resistance and wick supply capacity are two important indicators of a heat pipe's overall heat transfer performance. The heat pipe's thermal resistance determines the temperature difference between the hot and cold ends of the heat pipe under a given heat load, while the wick's supply capacity determines the upper limit of the heat flow rate the heat pipe can handle. Due to the combined influence of multiple material and process parameters, these factors often exhibit a trade-off relationship. In the prior art, to improve the heat dissipation performance and reduce the thermal resistance of heat pipes, the wick inside the heat pipe is thinned. The thinner the wick, the lower the thermal resistance, and under a given heat load and ambient temperature, the temperature of the cooled object is also lower. However, a thinner wick also results in a lower liquid transport capacity. Under a given heat load, the pressure drop generated to transport the required flow of liquid from the condenser section to the evaporator section of the heat pipe increases, making the heat pipe more susceptible to drying out under a given capillary force. Summary of the Invention

[0005] In order to solve the problem that the heat pipe cannot better balance the thermal resistance and the liquid supply capacity of the liquid wick, the present application provides a heat pipe with an asymmetric sintered liquid wick and a preparation process thereof.

[0006] In a first aspect, the present application provides a heat pipe with an asymmetric sintered liquid-absorbing core, adopting the following technical solution: a heat pipe with an asymmetric sintered liquid-absorbing core, comprising a tube shell and a liquid-absorbing core, the liquid-absorbing core being arranged in a ring shape, the inner wall of the liquid-absorbing core forming a vapor zone, the thickness of the core wall of the liquid-absorbing core gradually increasing along the top sides to the bottom of the liquid-absorbing core; the liquid-absorbing core is made by sintering copper powder, and the liquid-absorbing core consists of a first liquid-absorbing part and a second liquid-absorbing part, the first liquid-absorbing part corresponds to the top area of ​​the tube shell and is arranged above the midline of the vapor zone, the second liquid-absorbing part corresponds to the bottom area of ​​the tube shell and is arranged below the midline of the vapor zone, and the particle size of the copper powder in the first liquid-absorbing part is smaller than the particle size of the copper powder in the second liquid-absorbing part.

[0007] By adopting the above technical solution, the liquid wick is annular and its thickness gradually increases from both sides of the top to the bottom, so that the liquid wick is asymmetrically arranged corresponding to the top and bottom of the heat pipe, and the thickness of the top of the liquid wick is less than that of the bottom, thereby making the steam area offset toward the top position of the heat pipe, which can achieve the reduction of the thermal resistance of the local position of the heat pipe; the first liquid wick portion corresponds to the top area of ​​the tube shell and the copper powder particle size is small, and the second liquid wick portion corresponds to the bottom area of ​​the tube shell and the copper powder particle size is large. When in use, the top of the liquid wick is placed close to the heat dissipation object, and most of the heat will be transferred through the larger The thinner side of the wick conducts heat to the gas-liquid interface, allowing the first wick portion at the top of the wick to be primarily responsible for absorbing and transferring heat, while the thicker bottom portion has a higher absorption rate, which can reduce the flow resistance of liquid reflux. The second wick portion is primarily responsible for liquid reflux, providing timely liquid supply to the first wick portion, effectively ensuring the liquid flow demand of the first wick portion and reducing the risk of dry burning in the thinner first wick portion. This decouples and jointly optimizes the thermal resistance and liquid supply capacity of the heat pipe, while reducing the thermal resistance of the heat pipe and improving the liquid supply capacity of the wick, greatly increasing the heat dissipation of the heat pipe. The heat pipe of this application is suitable for heat dissipation from CPUs and cooling systems of electronic products such as computers, and has excellent heat dissipation performance.

[0008] Preferably, the width ratio of the top width of the absorbent core to the bottom width of the absorbent core is 1:(2-3.5).

[0009] By adopting the above technical solution, the width ratio of the top to the bottom of the wick is 1:(2-3.5), which can better achieve the reduction of local thermal conductivity resistance and the increase of permeability and reduction of flow resistance on the thicker side of the wick, further achieving the decoupling and joint synergy of the thermal resistance and liquid supply capacity of the heat pipe; if the top of the wick is thinner, it will easily cause the problem of unbalanced heat transfer and liquid absorption; if the top of the wick is thicker, the heat transfer efficiency will be reduced.

[0010] Preferably, the particle size of the copper powder in the first liquid absorption part is 40-60 μm, and the particle size of the copper powder in the second liquid absorption part is 100-150 μm.

[0011] By adopting the above technical solution, the first liquid absorption part is formed by sintering copper powder of 40-60μm. The first liquid absorption part has a fine liquid absorption capillary structure, has good thermal conductivity, and can conduct heat with faster efficiency; the second liquid absorption part is formed by sintering copper powder of 100-150μm. Compared with the first liquid absorption part, it has better liquid permeability and can absorb the refluxed liquid, effectively ensuring the liquid flow requirement during the heat transfer process of the first liquid absorption part, and improving the heat dissipation of the heat pipe.

[0012] Preferably, the tube shell is a copper shell or an aluminum shell.

[0013] By adopting the above technical solution, the tube shell is made of copper shell or aluminum shell, which has good thermal conductivity and further improves the heat dissipation performance of the heat pipe.

[0014] In a second aspect, the present application provides a process for preparing a heat pipe having an asymmetric sintered wick, which adopts the following technical solution: A process for preparing a heat pipe with an asymmetric sintered wick comprises the following steps: S1. Place a core rod in a tube shell, with the core rod positioned close to the top side of the tube shell, forming an annular space between the tube shell and the core rod. Fill the annular space corresponding to the top area of ​​the tube shell and above the center line of the core rod with a first copper powder. Fill the annular space corresponding to the bottom area of ​​the tube shell and below the center line of the core rod with a second copper powder, thereby producing a heat pipe to be sintered. S2. Sintering the heat pipe to be sintered, and then taking out the core rod to obtain a heat pipe with a liquid wick.

[0015] By adopting the above technical solution, the core rod is first placed in the tube shell, and is arranged and fixed near the top side of the tube shell, so that an annular space is formed between the tube shell and the core rod, and the annular space is asymmetrically arranged corresponding to the top and bottom of the tube shell. Then, the first copper powder is filled in the annular space corresponding to the top area of ​​the tube shell, and is filled above the center line of the core rod. The second copper powder is filled in the annular space corresponding to the bottom position of the tube shell, and is filled below the center line of the core rod, so that the first copper powder and the second copper powder are stably filled in the annular space and form the prototype of the liquid wick, thereby obtaining a heat pipe to be sintered. Then, the sintered heat pipe is sintered, so that the first copper powder and the second copper powder form a continuous capillary channel structure under the action of sintering, forming a complete liquid wick, and obtaining a heat pipe with a liquid wick.

[0016] Preferably, the first copper powder in step S1 is prepared from the following raw materials in weight percentage: 90-95% of 40-60 μm copper powder, 4-7% of dispersant, and 1-3% of pore-forming stabilizer; the second copper powder is prepared from the following raw materials in weight parts: 93-97% of 100-150 μm copper powder, 2-5% of dispersant, and 1-2% of pore-forming stabilizer.

[0017] By adopting the above technical solution, the first copper powder is prepared from 90-95% 40-60μm copper powder, 4-7% dispersant and 1-3% pore-forming stabilizer, and the second copper powder is prepared from 93-97% 100-150μm copper powder, 2-5% dispersant and 1-2% pore-forming stabilizer. The dispersant can be evenly dispersed into the copper powder, reducing the problems of agglomeration and agglomeration of the copper powder, so that the copper powder forms a uniformly bonded bonding system. The pore-forming stabilizer can increase the porosity of the first copper powder and the second copper powder during sintering, and improve the working liquid permeability. The dispersant and the pore-forming stabilizer play a good synergistic role, which can improve the heat dissipation efficiency of the heat pipe.

[0018] Preferably, the dispersant in the first copper powder and the second copper powder consists of cashew nut shell liquid modified polyol and 2-octenyl succinic anhydride in a weight ratio of 1:(0.2-0.5).

[0019] By adopting the above technical solution, using cashew nut shell liquid-modified polyol and 2-octenyl succinic anhydride in an optimal weight ratio as dispersants for the first copper powder and the second copper powder, the copper powder can be better dispersed, volatilized evenly and stably during the sintering process, thereby improving the uniformity of the capillary pore structure of the liquid-absorbing wick and reducing the problem of large capillary pore structure caused by rapid volatilization, which in turn damages the capillary pore structure.

[0020] Preferably, the pore-forming stabilizers in the first copper powder and the second copper powder are both composed of copper carbonate and ammonium carbonate in a weight ratio of (1-2):1.

[0021] By adopting the above technical solution, copper carbonate and ammonium carbonate in a relatively optimal weight ratio are used as pore-forming stabilizers for the first copper powder and the second copper powder. During the sintering process, they can be decomposed into gases containing C, H, and O and copper oxides. The volatilization of the gases has a pore-forming effect, which can further increase the porosity of the capillary channel structure and form through holes. The copper oxides are further reduced to pure copper in a reducing atmosphere of hydrogen, which can further improve the stability of the capillary structure and the liquid absorption performance of the liquid absorption core, thereby improving the heat dissipation performance of the heat pipe.

[0022] Preferably, the sintering atmosphere in step S2 is a mixed atmosphere of nitrogen and hydrogen.

[0023] By adopting the above technical solution and using a mixed atmosphere of nitrogen and hydrogen for sintering, the sintering process of the liquid absorbent core can be ensured to proceed smoothly, and adverse phenomena such as oxidation of the first copper powder and the second copper powder can be avoided, thereby ensuring the performance of the liquid absorbent core.

[0024] Preferably, the sintering temperature in step S2 is divided into three stages: the sintering temperature of the first stage is 380-480°C, and the sintering time is 20-40 min; the sintering temperature of the second stage is 550-600°C, and the sintering time is 10-20 min; the sintering temperature of the third stage is 700-800°C, and the sintering time is 120-180 min.

[0025] By adopting the above technical solution, the sintering temperature and time are optimized, so that the first copper powder and the second copper powder can be sintered to form a continuous liquid-absorbing core with a capillary channel structure, thereby improving the liquid absorption rate of the heat pipe while reducing thermal resistance and improving heat dissipation performance.

[0026] The sintering temperature of the first stage is 380-480°C, and the sintering time is 20-40 minutes, which can stably decompose the dispersant and pore-forming stabilizer in the first copper powder, form pores in the prototype of the liquid-absorbing core formed by the first copper powder and the second copper powder, and increase the porosity of the liquid-absorbing core. Then, under the conditions of the sintering temperature of the second stage is 550-600°C, and the sintering time is 10-20 minutes, as the sintering temperature increases, the density between the copper powder particles increases, causing the pores to expand to form a continuous capillary channel structure. Finally, under the conditions of the sintering temperature of the third stage is 700-800°C, and the sintering time is 120-180 minutes, the surface of the copper powder particles melts to form a stable capillary channel skeleton structure, thereby obtaining a liquid-absorbing core with a stable structure and a continuous capillary channel structure, and the obtained heat pipe has good heat dissipation performance.

[0027] In summary, this application includes at least one of the following beneficial technical effects: 1. The present application discloses a heat pipe having an asymmetric sintered wick. The wick is annular and its thickness gradually increases from the top to the bottom, so that the wick is asymmetrically arranged relative to the top and bottom of the heat pipe, and the vapor zone is offset toward the top of the heat pipe. When in use, the top of the wick is placed close to the object to be dissipated, and most of the heat will be transferred to the gas-liquid interface through the thinner side of the wick. This allows the first wick at the top of the wick to be primarily responsible for heat absorption and heat transfer, while the thicker bottom has a higher liquid absorption rate, which can reduce the flow resistance of liquid reflux. The second wick is primarily responsible for liquid reflux, providing timely liquid supply to the first wick, effectively ensuring the liquid flow demand of the first wick, and reducing the risk of dry burning in the thinner first wick. This decoupling and joint optimization of the heat pipe's thermal resistance and liquid supply capacity are achieved, reducing the heat pipe's thermal resistance while increasing the wick's liquid supply capacity, greatly improving the heat dissipation of the heat pipe. The present application's heat pipe is suitable for heat dissipation from CPUs and cooling systems of electronic products such as computers, and has excellent heat dissipation performance.

[0028] 2. The copper powder particle size of the first liquid absorption part is 40-60μm, and the copper powder particle size of the second liquid absorption part is 100-150μm. The first liquid absorption part has a fine liquid absorption capillary structure, has good thermal conductivity, and can conduct heat at a faster efficiency. The second liquid absorption part has better liquid permeability than the first liquid absorption part, and can absorb the refluxed liquid, which effectively guarantees the liquid flow requirement during the heat transfer process of the first liquid absorption part and improves the heat dissipation of the heat pipe.

[0029] 3. The preparation process of the present application is to first place the core rod in the tube shell, and set and fix it close to the top side of the tube shell, so that an annular space is formed between the tube shell and the core rod, and the annular space is asymmetrically arranged corresponding to the top and bottom of the tube shell. Then, the first copper powder is filled in the annular space corresponding to the top area of ​​the tube shell, and is filled above the center line of the core rod. The second copper powder is filled in the annular space corresponding to the bottom position of the tube shell, and is filled below the center line of the core rod, so that the first copper powder and the second copper powder are stably filled in the annular space and form the prototype of the liquid wick, thereby preparing a heat pipe to be sintered, and then the sintered heat pipe is sintered, so that the first copper powder and the second copper powder form a continuous capillary channel structure under the action of sintering, forming a complete liquid wick, and preparing a heat pipe with a liquid wick.

[0030] 4. Optimize the sintering temperature and time. The sintering temperature of the first stage is 380-480°C, and the sintering time is 20-40 minutes. The sintering temperature of the second stage is 550-600°C, and the sintering time is 10-20 minutes. The sintering temperature of the third stage is 700-800°C, and the sintering time is 120-180 minutes. This allows the first copper powder and the second copper powder to be sintered to form a continuous liquid-absorbing core with a capillary channel structure, thereby improving the liquid absorption rate of the heat pipe while reducing the thermal resistance and improving the heat dissipation performance.

[0031] 5. The first copper powder is prepared from 40-60 μm copper powder, a dispersant, and a pore-forming stabilizer. The second copper powder is prepared from 100-150 μm copper powder, a dispersant, and a pore-forming stabilizer. The dispersant in the first copper powder and the second copper powder is composed of cashew nut shell oil-modified polyol and 2-octenyl succinic anhydride in a weight ratio of 1: (0.2-0.5), and the pore-forming stabilizer is composed of copper carbonate and ammonium carbonate in a weight ratio of (1-2): 1. The dispersant can be evenly dispersed in the copper powder, reducing the problems of agglomeration and agglomeration of the copper powder, so that the copper powder forms a uniformly bonded bonding system. The pore-forming stabilizer can increase the porosity of the first copper powder and the second copper powder during sintering, improve the working liquid permeability, and the dispersant and the pore-forming stabilizer play a good synergistic role, which can improve the heat dissipation efficiency of the heat pipe. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a schematic longitudinal cross-sectional view of a heat pipe with an asymmetric sintered wick according to the present application; Figure 2 This is a schematic diagram of the assembly of a heat pipe with an asymmetric sintered liquid wick in the present application.

[0033] Description of reference numerals: 1. Tube shell; 2. Liquid absorption core; 21. First liquid absorption part; 22. Second liquid absorption part; 3. Steam zone. DETAILED DESCRIPTION

[0034] The following is combined with Figure 1-2 The present application is further described in detail with reference to the accompanying drawings and examples.

[0035] The following are the sources and specifications of some raw materials of this application. The raw materials used in the preparation examples and examples of this application can be obtained from commercial sources, including but not limited to the following models and manufacturers. Raw materials with equivalent performance can be used: 1. Cashew nut shell liquid modified polyol: Haoyi New Materials, FX-9001; 2. 2-Octenylsuccinic anhydride: CAS No. 26680-54-6, content 99%.

[0036] Preparation Example of the First Copper Powder and the Second Copper Powder Preparation Example 1 Preparation Example 1 discloses a first copper powder and a second copper powder, which are prepared by the following steps: The first copper powder material was prepared by uniformly mixing 9 kg of 50 μm copper powder, 0.7 kg of cashew nut shell liquid modified polyol as a dispersant, and 0.3 kg of a pore-forming stabilizer (composed of copper carbonate and ammonium carbonate in a weight ratio of 1:1).

[0037] The second copper powder was prepared by uniformly mixing 9.3 kg of 150 μm copper powder, 0.5 kg of cashew nut shell liquid modified polyol as a dispersant, and 0.2 kg of a pore-forming stabilizer (composed of copper carbonate and ammonium carbonate in a weight ratio of 1:1).

[0038] Preparation Example 2-3 The difference between Preparation Example 2-3 and Preparation Example 1 is that the raw material amounts and parameters are different, see Table 1 below for details.

[0039] Table 1 Raw material dosage and parameters of Preparation Examples 1-3 Preparation Example 4 The difference between Preparation Example 4 and Preparation Example 1 is that the dispersion stabilizer in the first copper powder and the second copper powder is composed of cashew nut shell liquid modified polyol and 2-octenyl succinic anhydride in a weight ratio of 1:0.2, and the rest is the same as Preparation Example 1.

[0040] Preparation Example 5 The difference between Preparation Example 5 and Preparation Example 1 is that the dispersion stabilizer in the first copper powder and the second copper powder is composed of cashew nut shell liquid modified polyol and 2-octenyl succinic anhydride in a weight ratio of 1:0.5, and the rest is the same as Preparation Example 1. Example

[0041] Example 1 Example 1 discloses a heat pipe with an asymmetric sintered wick, referring to Figure 1The heat pipe comprises a tube shell 1 and a wick 2. The tube shell 1 is a copper shell or an aluminum shell. In this embodiment, the tube shell 1 is a copper shell, which has good heat dissipation. The wick 2 is arranged in an annular shape. The inner wall of the wick 2 is surrounded by a vapor zone 3 for steam to pass through. The thickness of the wick 2 wall gradually increases along the bottom of the top and sides of the wick 2, so that the wick 2 is asymmetrically arranged with respect to the top and bottom of the tube shell 1. The vapor zone 3 is offset from the top of the heat pipe. Preferably, the width ratio of the top width of the wick 2 to the bottom width of the wick 2 is 1:(2-3.5). In this embodiment, the width ratio of the top width of the wick 2 to the bottom width of the wick 2 is 1:3. The liquid absorbent core 2 is made by sintering copper powder. The liquid absorbent core 2 consists of a first liquid absorbent part 21 and a second liquid absorbent part 22. The first liquid absorbent part 21 corresponds to the top area of ​​the tube shell 1 and is arranged above the midline of the steam zone 3. The second liquid absorbent part 22 corresponds to the bottom area of ​​the tube shell 1 and is arranged below the midline of the steam zone 3. The particle size of the copper powder of the first liquid absorbent part 21 is smaller than the particle size of the copper powder of the second liquid absorbent part 22. Preferably, the particle size of the copper powder of the first liquid absorbent part 21 is 40-60 μm, and the particle size of the copper powder of the second liquid absorbent part 22 is 100-150 μm. In this embodiment, the particle size of the copper powder of the first liquid absorbent part 21 is 50 μm, and the particle size of the copper powder of the second liquid absorbent part 22 is 150 μm. It should be noted that the top in this application refers to the side corresponding to the thinner thickness of the liquid absorbent core 2, and the bottom refers to the side corresponding to the thicker thickness of the liquid absorbent core 2.

[0042] When using, refer to Figure 2 , several heat pipes are fixed to a fixed shell, and the top side of the heat pipe corresponding to the liquid wick 2 is close to the cooled object. Most of the heat will be transferred to the gas-liquid interface through the thinner liquid wick 2 on the top side. The larger permeability of the thicker large-diameter copper powder sintered liquid wick 2 on the bottom side ensures the working liquid flow requirement during the heat transfer process of the thinner small-diameter copper powder sintered liquid wick, thereby greatly improving the heat dissipation of the heat pipe.

[0043] The preparation process of the heat pipe with an asymmetric sintered liquid wick comprises the following steps: Take a heat pipe with a length of 120mm, an outer diameter of 6mm, a steam zone diameter of 4.8mm, and a shell thickness of 0.5mm as an example: S1. Place a ceramic core rod in a tube shell, arrange and fix the core rod near the top side of the tube shell, form an annular space between the tube shell and the core rod, control the width ratio of the top width of the wick to the bottom width of the wick 2 to be 1:3, fill the annular space corresponding to the top area of ​​the tube shell with commercially available copper powder with a particle size of 50 μm as a first copper powder material, and fill it above the center line of the core rod. Fill the annular space corresponding to the bottom position of the tube shell with commercially available copper powder with a particle size of 150 μm as a second copper powder material and fill it below the center line of the core rod, thereby preparing a heat pipe to be sintered; S2. Place the heat pipe to be sintered in a sintering furnace and sinter it in a mixed atmosphere of 95% nitrogen and 5% hydrogen. The sintering is divided into three stages: the sintering temperature of the first stage is 380°C and the sintering time is 40 minutes; the sintering temperature of the second stage is 550°C and the sintering time is 20 minutes; the sintering temperature of the third stage is 700°C and the sintering time is 180 minutes. Then, remove the core rod to obtain a heat pipe with a liquid wick.

[0044] Examples 2-4 The difference between Example 2-4 and Example 1 is that the preparation process parameters and the sources of copper powder are different, see Table 2 below for details.

[0045] Table 2 Parameters of Examples 1-4 Example 5 The difference between Example 5 and Example 1 is that the first copper powder and the second copper powder are both derived from Preparation Example 4, and the rest are the same as Example 1.

[0046] Example 6 The difference between Example 6 and Example 1 is that the first copper powder and the second copper powder are both derived from Preparation Example 5, and the rest are the same as Example 1.

[0047] Example 7 The difference between Example 7 and Example 1 is that the sintering in step S2 is divided into two stages, the sintering temperature of the first stage is 380°C, and the sintering time is 40 min; the sintering temperature of the second stage is 700°C, and the sintering time is 180 min. The rest is the same as Example 2.

[0048] Example 8 The difference between Example 8 and Example 1 is that the particle size of the first copper powder in step S1 is 80 μm, and the rest is the same as Example 1.

[0049] Comparative Example Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the particle size of the first copper powder and the particle size of the second copper powder are the same, both of which are 150 μm. The other parameters are the same as those of Example 1.

[0050] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that the liquid absorbent core is arranged in a ring shape, and the width of the core wall at any position of the liquid absorbent core is the same. The other features are the same as those of Example 1.

[0051] Performance testing The following performance tests were conducted on the heat pipes prepared in Examples 1-8 and Comparative Examples 1-2: 1. Heat dissipation efficiency test Use water as the working liquid and inject it into the heat pipe. Control the amount of water injected to be 60% of the amount of liquid absorbed by the wick. Exhaust and seal to obtain the finished heat pipe. Take a 65℃ CPU board as the object to be cooled. Refer to the attached Figure 2 In the assembly method, the aluminum shell is used as the fixed shell, and the four heat pipes are installed horizontally and arranged. The test is carried out for 2 minutes. The temperature of the CPU board before and after heat dissipation is measured, and the temperature difference (unit: ℃) is calculated. The larger the temperature difference, the better the heat dissipation efficiency.

[0052] 2. Liquid absorption rate test of heat pipe Immerse the heat pipe vertically in water and record the amount of water absorbed by the heat pipe in 5 seconds. Test the water absorption rate of the heat pipe (unit: mL / s). The greater the absorption rate, the stronger the liquid supply capacity.

[0053] The following are the performance test data of the heat pipes of Examples 1-8 and Comparative Examples 1-2, see Table 3 below for details.

[0054] Table 3 Performance data of heat pipes of Examples 1-8 and Comparative Examples 1-2 “ / ” means not tested.

[0055] Combining Example 11 with Examples 2-6 and Table 3, it can be concluded that the heat pipes prepared by sintering the first and second copper powders prepared in this application have a high liquid absorption rate and good heat dissipation effect. Compared with Example 1, Examples 2-4 add a dispersant and a pore-forming stabilizer to the copper powder, which improves the liquid supply performance, liquid absorption rate, and heat dissipation performance of the resulting liquid absorption wicks. Compared with Example 2, Examples 5-6 further optimize the components and ratios of the dispersant, resulting in a heat pipe with an increased heat dissipation temperature difference and an improved liquid absorption rate.

[0056] Combining Example 1 and Example 7 with Table 3, it can be concluded that by optimizing the sintering temperature and time of the liquid wick of the heat pipe, the heat dissipation efficiency and liquid supply capacity of the heat pipe can be improved. This may be because the optimal sintering temperature and time can increase the porosity and stability of the capillary channel structure of the liquid wick.

[0057] Combining Example 1 and Example 8, Comparative Example 1 and Table 3, it can be concluded that by optimizing the particle size of the copper powder in the first and second liquid absorbing parts of the liquid absorbing core, the heat dissipation efficiency of the heat pipe can be significantly improved.

[0058] Combining Example 1 and Comparative Example 2 with Table 3, it can be concluded that the heat pipe made using the asymmetric sintered liquid wick of the present application has significantly higher heat dissipation efficiency. In Comparative Example 2, heat dissipation testing using heat pipes of the same wall thickness revealed significantly lower heat dissipation efficiency, so the liquid absorption rate was not tested.

[0059] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A heat pipe with an asymmetric sintered wick, comprising a tube shell and a wick, characterized in that: The liquid wick is arranged in a ring shape, and the inner wall of the liquid wick is arranged to form a vapor zone. The thickness of the core wall of the liquid wick gradually increases along the top and sides of the liquid wick to the bottom; the liquid wick is made by sintering copper powder, and the liquid wick consists of a first liquid wick part and a second liquid wick part. The first liquid wick part corresponds to the top area of ​​the tube shell and is arranged above the midline of the vapor zone, and the second liquid wick part corresponds to the bottom area of ​​the tube shell and is arranged below the midline of the vapor zone. The particle size of the copper powder in the first liquid wick part is smaller than the particle size of the copper powder in the second liquid wick part.

2. The heat pipe with an asymmetric sintered wick according to claim 1, characterized in that: The width ratio of the top width of the wick to the bottom width of the wick is 1:(2-3.5).

3. The heat pipe with an asymmetric sintered wick according to claim 1, characterized in that: The particle size of the copper powder in the first liquid absorption part is 40-60 μm, and the particle size of the copper powder in the second liquid absorption part is 100-150 μm.

4. The heat pipe with an asymmetric sintered wick according to claim 1, characterized in that: The tube shell is a copper shell or an aluminum shell.

5. A process for preparing a heat pipe having an asymmetric sintered wick according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1. Place a core rod in a tube shell, arrange and fix the core rod near the top side of the tube shell, and form an annular space between the tube shell and the core rod. Fill the annular space corresponding to the top area of ​​the tube shell and the position above the center line of the core rod with a first copper powder. Fill the annular space corresponding to the bottom area of ​​the tube shell and the position below the center line of the core rod with a second copper powder, thereby producing a heat pipe to be sintered. S2. Sintering the heat pipe to be sintered, and then taking out the core rod to obtain a heat pipe with a liquid wick.

6. The process for preparing a heat pipe with an asymmetric sintered wick according to claim 5, characterized in that: The first copper powder in step S1 is prepared from the following raw materials in weight percentage: 90-95% of 40-60µm copper powder, 4-7% of dispersant, and 1-3% of pore-forming stabilizer; the second copper powder is prepared from the following raw materials in weight parts: 93-97% of 100-150µm copper powder, 2-5% of dispersant, and 1-2% of pore-forming stabilizer.

7. The process for preparing a heat pipe with an asymmetric sintered wick according to claim 6, wherein: The dispersant in the first copper powder and the second copper powder consists of cashew nut shell liquid modified polyol and 2-octenyl succinic anhydride in a weight ratio of 1:(0.2-0.5).

8. The process for preparing a heat pipe with an asymmetric sintered wick according to claim 6, wherein: The pore-forming stabilizers in the first copper powder and the second copper powder are both composed of copper carbonate and ammonium carbonate in a weight ratio of (1-2):

1.

9. The process for preparing a heat pipe with an asymmetric sintered wick according to claim 5, wherein: The sintering atmosphere in the step S2 is a mixed atmosphere of nitrogen and hydrogen.

10. The process for preparing a heat pipe with an asymmetric sintered wick according to claim 5, wherein: The sintering temperature in step S2 is divided into three stages. The sintering temperature of the first stage is 380-480°C and the sintering time is 20-40 min; the sintering temperature of the second stage is 550-600°C and the sintering time is 10-20 min; the sintering temperature of the third stage is 700-800°C and the sintering time is 120-180 min.

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