An ultra-thin heat pipe with directional rectification and a manufacturing method thereof

Abstract

The present application relates to a kind of directional rectification ultra-thin heat pipe and manufacturing method, including the pipe body being made of first heat-conducting sheet and second heat-conducting sheet, one end of pipe body is as condensing end, the other end is as evaporation end, the cavity is inside the pipe body, the bottom cavity surface of cavity is provided with multiple microchannels being set along condensing end to evaporation end, the two sides of microchannel are provided with multiple inclined grooves being communicated with it, the inclined groove is set with microchannel and presents first set acute angle and is inclined to evaporation end, the ultra-thin heat pipe of the present application solves the difficult problem that traditional groove type wick heat pipe, condensing working medium transport slowly and wick material pump liquid phase working medium capacity is insufficient, to effectively control gas-liquid circulation flow, improve gas-liquid circulation efficiency, improve the heat dissipation capacity and environmental stability of ultra-thin heat pipe.

Description

Technical Field

[0001] This invention relates to the field of heat pipe technology, specifically to an ultrathin heat pipe with directional rectification and its manufacturing method. Background Technology

[0002] The statements herein provide only background information in relation to this invention and do not necessarily constitute prior art.

[0003] Heat pipes, as components that utilize the latent heat of phase change in their internal working fluid for rapid and efficient heat conduction, possess numerous advantages such as high thermal conductivity, good operational stability, self-adaptive equilibrium, small size, and no need for external energy drive. They have replaced traditional non-phase-change cooling methods and are widely used in heat dissipation for electronic devices in many fields. To adapt to the trend towards thinner and lighter electronic devices and increasingly limited heat dissipation space, traditional heat pipes are also evolving towards ultra-thin designs. Unlike traditional circular heat pipes, ultra-thin heat pipes have a larger surface area and a higher degree of tightness in contact with the surface; the spatial arrangement of the evaporation and condensation sections of ultra-thin heat pipes can be dynamically adjusted. These numerous advantages make ultra-thin heat pipes one of the effective strategies for heat dissipation and cooling of thin and light portable electronic devices.

[0004] Ultrathin heat pipes refer to heat pipes with a thickness of less than 2 mm. The thickness of ultrathin heat pipes is generally less than 2 mm, and the internal gas-liquid circulation occurs within a sub-millimeter space. This confined working space presents significant challenges to the development of ultrathin heat pipes, primarily including significantly increased internal gas-liquid circulation resistance, insufficient pumping capacity of the wick material, slow delivery of the condensing fluid, and extreme sensitivity of the gas cavity space to minute deformations of the shell. The stable operation of ultrathin heat pipes mainly depends on the capillary force of the wick and the liquid's permeation and reflux rate. The capillary pressure and permeability of the wick are the most important parameters affecting heat transfer performance and limits. Currently, there are three main types of wicks: grooved, sintered, and composite. The capillary structure is attached to the inner wall of the heat pipe, allowing liquid to flow from the condenser end to the evaporator end through capillary action. Each type has its advantages and disadvantages, and each has its own limitations. Sintered and composite wicks have greater capillary force and better anti-gravity ability, but they cannot further adapt to the trend of thinner heat pipes. Grooved wicks have higher permeability and are easier to make thinner, but they only use rectangular groove capillary wick structures, have low capillary force, and are easily affected by gravity, resulting in condensate backflow. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the purpose of this invention is to provide an ultra-thin heat pipe with directional rectification and its manufacturing method, which has strong capillary force and is not easily affected by gravity.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0007] In a first aspect, embodiments of the present invention provide an ultrathin heat pipe with directional rectification, comprising a tube body composed of a first heat-conducting plate and a second heat-conducting plate, one end of the tube body serving as a condensing end and the other end serving as an evaporating end, the tube body having a cavity inside, the bottom cavity surface of the cavity being provided with a plurality of microchannels arranged along the condensing end to the evaporating end, and a plurality of inclined grooves communicating with the microchannels on both sides, the inclined grooves being arranged at a first predetermined acute angle with the microchannels and inclined toward the evaporating end.

[0008] Optionally, in the inclined groove, two parallel groove surfaces form a second set acute angle with the bottom groove surface and are inclined toward the evaporation end.

[0009] Optionally, the first set acute angle between the inclined groove and the microchannel is 30°-60°.

[0010] Optionally, the length of the inclined groove is 0.1mm-0.4mm.

[0011] Optionally, the second heat-conducting sheet has a groove on its surface facing the first heat-conducting sheet to form a cavity, and the first heat-conducting sheet has microchannels and inclined grooves on its surface facing the second heat-conducting sheet.

[0012] Optionally, the thickness of the second heat-conducting sheet is 0.1mm-0.2mm, and correspondingly, the depth of the groove is 0.05mm-0.1mm, and the thickness of the first heat-conducting sheet is 0.3mm-0.5mm.

[0013] Optionally, both the first and second heat-conducting sheets are made of copper.

[0014] Secondly, embodiments of the present invention provide a method for manufacturing the directional rectified ultrathin heat pipe described in the first aspect, comprising the following steps:

[0015] Multiple microchannels and inclined grooves communicating with the microchannels are machined on one side surface of the first heat-conducting sheet, and a groove is machined on one side surface of the second heat-conducting sheet.

[0016] The first and second heat-conducting sheets are fixed by diffusion welding, wherein the surface of the first heat-conducting sheet with microchannels and inclined grooves is positioned opposite to the surface of the second heat-conducting sheet with grooves to form a cavity through the grooves.

[0017] Optionally, microchannels and inclined grooves are processed on the surface of the first heat-conducting sheet using laser etching or cutting methods, and grooves are processed on the surface of the second heat-conducting sheet using laser etching or cutting methods.

[0018] Optionally, before diffusion welding, the first and second heat-conducting sheets are immersed in phosphoric acid for a set time to remove the surface oxides. After the oxides are removed, the first and second heat-conducting sheets are ultrasonically cleaned with acetone.

[0019] The beneficial effects of this invention are as follows:

[0020] 1. The ultrathin heat pipe of the present invention is provided with microchannels and inclined grooves, forming a liquid wick structure through the microchannels and inclined grooves. The grooved liquid wick form meets the requirement of thinness and lightness of the heat pipe. At the same time, the inclined grooves are set towards the evaporation end, forming a biomimetic directional rectification surface. Compared with the microchannels with a simple rectangular cross section, it has stronger capillary force, realizing rapid directional liquid transfer from the condensation end to the evaporation end, and timely replenishing the liquid working fluid at the evaporation end. At the same time, the setting of the inclined grooves makes the heat pipe have a strong ability to prevent backflow, so that the liquid flows unidirectionally towards the evaporation end, which overcomes the influence of gravity to a certain extent.

[0021] 2. In the ultra-thin heat pipe of the present invention, the two parallel groove surfaces of the inclined groove form a second set acute angle with the bottom groove surface and are inclined toward the evaporation end, which further improves the ability to prevent liquid backflow and improves the pumping capacity of the liquid. Attached Figure Description

[0022] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0023] Figure 1 This is a front view of the overall structure of Embodiment 1 of the present invention;

[0024] Figure 2 This is a schematic diagram of the groove structure on the first heat-conducting sheet in Embodiment 1 of the present invention;

[0025] Figure 3 This is a top view of the overall structure of Embodiment 1 of the present invention;

[0026] Figure 4 This is a microstructure diagram of the surface of the trench structure in Embodiment 1 of the present invention;

[0027] Figure 5 This is a schematic diagram of the unidirectional flow of the liquid working fluid in Embodiment 1 of the present invention;

[0028] Figure 6 This is a schematic diagram of the trench structure preventing the reverse flow of the liquid working fluid in Embodiment 1 of the present invention;

[0029] Figure 7 This is an analysis diagram of the liquid working fluid advance contact angle model in Embodiment 1 of the present invention;

[0030] Figure 8 This is an analysis diagram of the liquid working fluid retreat contact angle model in Embodiment 1 of the present invention;

[0031] Among them, 1. tube body, 2. cavity, 3. microchannel, 4. inclined groove. Detailed Implementation

[0032] For ease of description, the words "upper" and "lower" appearing in this invention only indicate that they are consistent with the upper and lower directions of the accompanying drawings and do not limit the structure. They are merely for the purpose of facilitating the description of this invention and simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0033] Example 1

[0034] This embodiment provides an ultrathin heat pipe with directional rectification, such as Figures 1-4 As shown, the device includes a tube body 1, with a cavity 2 inside the tube body 1 containing a working fluid. One end of the tube body 1 serves as a condenser end, and the other end serves as an evaporator end. The evaporator end is used to contact a heat source. The bottom surface of the cavity 2 has multiple groove structures. The axis of the groove structures is set along the length of the tube body, that is, the groove structures are set from the condenser end to the evaporator end. The groove structures are used to condense the working fluid from the condenser end to the evaporator end. The internal space of the cavity above the groove structures serves as a channel for the flow of steam working fluid, so that the heated and evaporated steam working fluid flows from the evaporator end to the condenser end.

[0035] In this embodiment, the groove structure forms a liquid-absorbing core. Traditional groove-type liquid-absorbing cores have rectangular grooves, which have relatively small capillary force and are easily affected by gravity, resulting in backflow. This embodiment improves the groove structure.

[0036] The groove structure includes multiple parallel microchannels 3. The microchannels 3 are rectangular grooves, and the length direction of the microchannels 3 is set along the length direction of the tube body, that is, the microchannels 3 are set from the condensing end to the evaporating end.

[0037] The size of the microchannel 3 can be the same as the groove size of the existing grooved liquid aspiration core, and will not be described in detail here.

[0038] Multiple inclined grooves 4 are provided on both sides of the microchannel 3, and one end of the inclined groove 4 is connected to the microchannel.

[0039] Multiple inclined grooves 4 are distributed along the length of the microchannel 3 on one side. Preferably, the multiple inclined grooves 4 are arranged at equal intervals.

[0040] The inclined grooves 4 on both sides of the microchannel 3 are symmetrically arranged with respect to the center line of the microchannel.

[0041] In this embodiment, the inclined groove 4 and the microchannel 3 are set at a set first acute angle, and the inclined groove 4 is inclined toward the evaporation end. That is, for the same inclined groove 4, the distance between the end of the inclined groove 4 connected to the microchannel 3 and the evaporation end is greater than the distance between the other end and the evaporation end.

[0042] like Figures 5-6 As shown, the inclined groove 4 forms a biomimetic rectifying structure, giving the groove structure stronger capillary force, realizing rapid directional liquid transport from the condensing end to the evaporating end, timely replenishing the liquid working fluid at the evaporating end. At the same time, the inclined groove 4 can promote the liquid condensing working fluid to flow unidirectionally from the condensing end to the evaporating end and prevent the liquid condensing working fluid from flowing in the opposite direction. Under the same condensation conditions, the working fluid in the condensing section no longer flows bidirectionally, but flows back towards the evaporating section, so that the flow of the liquid condensing working fluid is not affected by gravity to a certain extent, reducing the impact of gravity on the operation of the ultrathin heat pipe.

[0043] Furthermore, the degree of the first acute angle is set to be 30°-60°, and the length of the inclined groove 4 is 0.1mm-0.4mm. Those skilled in the art can integrate and adjust the first acute angle and the length of the inclined groove 4 according to actual needs to achieve the best directional liquid transmission capability.

[0044] In this embodiment, the inclined groove 4 includes a bottom groove surface and three side groove surfaces, wherein two side groove surfaces are parallel to each other, and the third side groove surface is disposed between the two parallel side groove surfaces.

[0045] To further improve the directional liquid transport capability of the trench structure, the two parallel side trench surfaces are set at a second acute angle to the bottom trench surface, and the side trench surfaces are inclined towards the evaporation end. That is, in the side trench surface, the distance between the lower edge connecting the bottom trench surface and the evaporation end is greater than the distance between the upper edge and the evaporation end.

[0046] In this embodiment, the tube body is formed by fixing a first heat-conducting sheet and a second heat-conducting sheet together. Both the first heat-conducting sheet and the second heat-conducting sheet are made of heat-conducting metal materials. Preferably, both the first heat-conducting sheet and the second heat-conducting sheet are made of copper sheets, which have low manufacturing cost and good thermal conductivity.

[0047] The first heat-conducting sheet has a groove structure formed by multiple microchannels 3 and inclined grooves 4 on one side surface, and the second heat-conducting sheet has a groove on one side surface. When the first heat-conducting sheet and the second heat-conducting sheet are fixed, the side surface of the first heat-conducting sheet with the groove structure and the side surface of the second heat-conducting sheet with the groove structure are arranged opposite to each other. The groove and the side surface of the first heat-conducting sheet together form a cavity for the flow of steam working fluid.

[0048] The thickness of the first heat-conducting sheet is 0.3mm-0.5mm, which can be set by those skilled in the art according to actual needs. The thickness of the second heat-conducting sheet is 0.1mm-0.2mm. Correspondingly, the depth of the groove is 0.05mm-0.1mm. The dimensions of the first heat-conducting sheet, the second heat-conducting sheet, and the groove can be set by those skilled in the art according to actual needs, and will not be described in detail here.

[0049] The ultrathin heat pipe of this embodiment forms a wick structure through microchannels and inclined grooves. The grooved wick design meets the requirements for a thinner and lighter heat pipe. The inclined grooves are oriented towards the evaporation end, creating a biomimetic directional rectifying surface. Compared to simply using microchannels with rectangular cross-sections, this provides stronger capillary force, enabling rapid directional liquid transport from the condensation end to the evaporation end and timely replenishment of the liquid water film at the evaporation end. Furthermore, the inclined grooves give the heat pipe a strong ability to prevent backflow, allowing the liquid to flow unidirectionally towards the evaporation end, thus overcoming the influence of gravity to some extent. This solves the problems of slow condensate delivery and insufficient pumping capacity of the wick material for liquid phase in traditional grooved wick heat pipes. Therefore, it effectively regulates the gas-liquid circulation, improves gas-liquid circulation efficiency, and enhances the heat dissipation capacity and environmental stability of the ultrathin heat pipe.

[0050] like Figures 7-8 As shown, in this embodiment, a flow model of the working fluid is established, the contact angle hysteresis model is corrected, and the pinning resistance F caused by the biomimetic topology is quantitatively analyzed.

[0051] F≈kbγ(cos(max{θ r0 -β,0})-cos(min{θ a0 +α,π}))

[0052] k represents the ratio of the trench structure area to the total area of ​​the trench structure region on the first heat-conducting plate, b represents the width of the microchannel, γ represents the surface tension of the liquid working fluid, and θ represents the surface tension of the liquid working fluid. a0 θ represents the intrinsic advancing contact angle. r0 The intrinsic retreat contact angle is represented by α, the inclination angle of the side surface of the inclined groove, and the inclination angle of the top surface of the inclined groove. Due to the different pinning resistance in the forward and reverse directions, the groove structure based on this embodiment has approximately 1.5-2.5 times the amount of condensate return compared to the rectangular groove capillary wick structure, depending on the angle between the inclined groove and the microchannel.

[0053] Example 2

[0054] This embodiment provides a method for manufacturing the ultrathin heat pipe described in Embodiment 1, including the following steps:

[0055] Step 1: Multiple microchannels and inclined grooves communicating with the microchannels are machined on one side surface of the first heat-conducting sheet, and a groove is machined on one side surface of the second heat-conducting sheet.

[0056] The first heat-conducting sheet is made of copper sheet with a thickness of 0.3mm-0.5mm. Multiple microchannels and corresponding inclined grooves are processed on one side surface of the first heat-conducting sheet by laser etching or laser cutting.

[0057] The second heat-conducting sheet uses a 0.1mm-0.2mm copper sheet, and a groove 0.05mm-0.1mm deep is machined on one side of the second heat-conducting sheet using laser etching or laser cutting.

[0058] Laser etching and laser cutting can be performed using existing technologies, and will not be described in detail here.

[0059] Step 2: Fix the first and second heat-conducting sheets using diffusion welding. The surface of the first heat-conducting sheet with microchannels and inclined grooves is positioned opposite the surface of the second heat-conducting sheet with grooves to form a cavity through the grooves. Specifically, this includes the following steps:

[0060] Step 2.1: Immerse the processed first and second heat-conducting sheets in a phosphoric acid solution for a set time to remove the oxidized parts on the surface of the first and second heat-conducting sheets. Preferably, the set time is 2-3 hours to ensure the removal effect of the oxidized parts.

[0061] Step 2.2: Use acetone to ultrasonically clean the surface oil of the first and second heat-conducting sheets after removing the oxidized parts, so that the surfaces of the first and second heat-conducting sheets are smooth.

[0062] Step 2.3: Place the first heat-conducting sheet and the second heat-conducting sheet into the mold. The mold is designed with the corresponding size according to the structure of the welded copper sheet. The first heat-conducting sheet and the second heat-conducting sheet are placed and fixed between the molds.

[0063] The mold can be set according to the dimensions of the first and second heat-conducting plates. It adopts existing technology, and its specific structure will not be described in detail here.

[0064] Step 3.3: Under a nitrogen protective gas atmosphere and at a set pressure, a multi-stage heating process is carried out to reach the solid-phase diffusion temperature of 600-750℃. This temperature is maintained for 5-6 hours, and then the pressure is released and the temperature is lowered to complete the diffusion welding of the first and second heat-conducting sheets, thereby completing the fabrication of the ultra-thin heat pipe.

[0065] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A directional rectified ultrathin heat pipe, characterized in that, The tube includes a tube body composed of a first heat-conducting plate and a second heat-conducting plate. One end of the tube body serves as a condensing end and the other end serves as an evaporating end. The tube body has a cavity inside. The bottom surface of the cavity is provided with multiple microchannels arranged from the condensing end to the evaporating end. Multiple inclined grooves are provided on both sides of the microchannels and communicate with them. The inclined grooves are arranged at a first set acute angle with the microchannels and are inclined towards the evaporating end.

2. The ultrathin heat pipe with directional rectification as described in claim 1, characterized in that, In the inclined groove, two parallel groove surfaces form a second set acute angle with the bottom groove surface and are inclined toward the evaporation end.

3. The ultrathin heat pipe with directional rectification as described in claim 1, characterized in that, The first set acute angle between the inclined groove and the microchannel is 30°-60°.

4. The ultrathin heat pipe with directional rectification as described in claim 1, characterized in that, The length of the inclined groove is 0.1mm-0.4mm.

5. The ultrathin heat pipe with directional rectification as described in claim 1, characterized in that, The second heat-conducting sheet has grooves on its surface facing the first heat-conducting sheet to form a cavity, and the first heat-conducting sheet has microchannels and inclined grooves on its surface facing the second heat-conducting sheet.

6. The ultrathin heat pipe with directional rectification as described in claim 5, characterized in that, The thickness of the second heat-conducting sheet is 0.1mm-0.2mm, and the corresponding depth of the groove is 0.05mm-0.1mm. The thickness of the first heat-conducting sheet is 0.3mm-0.5mm.

7. The ultrathin heat pipe with directional rectification as described in claim 1, characterized in that, Both the first and second heat-conducting sheets are made of copper.

8. A method for manufacturing an ultrathin heat pipe with directional rectification as described in any one of claims 1-7, characterized in that, Includes the following steps: Multiple microchannels and inclined grooves communicating with the microchannels are machined on one side surface of the first heat-conducting sheet, and a groove is machined on one side surface of the second heat-conducting sheet. The first and second heat-conducting sheets are fixed by diffusion welding, wherein the surface of the first heat-conducting sheet with microchannels and inclined grooves is positioned opposite to the surface of the second heat-conducting sheet with grooves to form a cavity through the grooves.

9. A method for manufacturing a directional rectified ultrathin heat pipe as described in claim 8, characterized in that, Microchannels and inclined grooves are fabricated on the surface of the first heat-conducting sheet using laser etching or cutting methods, and grooves are fabricated on the surface of the second heat-conducting sheet using laser etching or cutting methods.

10. A method for manufacturing a directional rectified ultrathin heat pipe as described in claim 8, characterized in that, Before diffusion welding, the first and second heat-conducting sheets are immersed in phosphoric acid for a set time to remove the surface oxides. After the oxides are removed, the first and second heat-conducting sheets are ultrasonically cleaned with acetone.

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