TW200533880A - Heat pipe and method for making the same - Google Patents

Abstract

A heat pipe includes a pipe, a wick and an operating fluid. The wick is disposed inside the pipe and contacted to inside walls of the pipe; and the operating fluid is sealed in the pipe and soaked in the wick. A number of concavities are defined on surfaces of the pipe in a regular array to increase a surface area of the pipe and further to promote the thermal conductivity of the heat pipe. A method for making the heat pipe is also provided.

Description

200533880 V. Description of Invention (1)

[Technical field to which the invention belongs] The present invention relates to a method for preparing a thermally conductive structure. In particular, it relates to a heat pipe and its system. [Previous technology] The heat pipe system relies on the phase change of its internal working fluid to realize the heat conduction component. It has excellent characteristics such as high thermal conductivity, excellent isothermal property, etc., and is widely used. The heat conduction effect of the heat conduction element and the technology of the second and second hairs are developing rapidly. The high stepper and high speed of electronic devices are dense and miniaturized, which makes the electronic volume per unit volume increase dramatically. The heat pipe technology is highly efficient, compact and Flexible and reliable features ", suitable for solving the current heat dissipation problem of electronic devices due to improved performance. Please refer to the first figure, a typical heat pipe 丨 〇 by the shell ii, the liquid wick 2 (capillary structure) and sealed in the tube The working fluid i 3 is composed of the heat pipe 丨 0 system = usually the tube is evacuated and then filled with a suitable working fluid 丨 3, so that the liquid wick 12 close to the inner wall of g is filled with the working fluid 13 and sealed. One end of the heat pipe i 〇 is the evaporation section 1 〇1 (heating section), and the other end is the condensation section 丨 〇2 (cooling section). 'It can be arranged between the evaporation section 丨 〇1 and the condensation section 丨 〇2 according to the needs of the application ~ Bar heat section. When the heat pipe 1 0 evaporation section 1 0 1 is heated, the working fluid 1 2 in the liquid wick 2 evaporates and vaporizes to form steam 14, and the steam 14 flows to the condensation section of the heat officer 10 under the action of a slight pressure difference. 1 0 2, condensed into working fluid 1 3 and releases heat 1 5 and the working fluid 1 3 flows back to the evaporation section 1 0 1 along the wick 12 by capillary action. In this cycle, the heat 15 is continuously transferred from the evaporation section 1 0 1 of the heat pipe 10 to the condensation The segment 10 2 'is absorbed by the cold source at the end of the condensation segment 10 2. In the process of heat conduction, the heat pipe 10 includes the following six interrelated ones:

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200533880 V. Description of the invention (2) Main process: (1) Heat 1 5 is transferred from the heat source to the working fluid 1 3 through the heat pipe shell 11 and the liquid wick 12 filled with the working fluid 1 3; (2) Working fluid 1 3 Evaporates on the liquid-vapor interface in the evaporation section 100; (3) Steam 1 4 flows from the evaporation section 101 to the condensation section 102; (4) Steam 1 4 in the condensation section 102 -Condensation on the liquid interface; (5) Heat 1 5 is transmitted from the gas-liquid interface through the wick 1 2, the working liquid 1 3 and the taste device 1 1 to the cold source; (6) in the wick 12 Capillary action causes the condensed working fluid 1 3 to return to the evaporation section 101. From the above six processes, it can be seen that the tube shell plays an important role in the heat conduction process. In the prior art, the heat pipe shell usually has a square, circular, triangular, etc. cross-section, and has a smooth surface. The material is copper, aluminum, steel, carbon steel, stainless steel, iron, nickel, titanium, or an alloy thereof. This metal or alloy has a high thermal conductivity, but the smooth surface reduces its thermal conductivity, which is not conducive to the improvement of the heat pipe's thermal conductivity. [Content] In order to solve the technical problem of the smooth surface of the heat pipe shell in the prior art, which is not conducive to the improvement of heat pipe heat conduction efficiency, the first / objective of the present invention is to provide a heat pipe with a plurality of micro depressions on the surface of the pipe shell, which enhances the heat conduction ability and ensures uniform heat conduction. . A second object of the present invention is to provide a method for preparing a heat pipe having a plurality of micro recesses arranged in an orderly manner on the surface of the shell.

200533880 V. Description of the invention (3) The heat pipe provided by the present invention includes a hollow-walled capillary wick and a capillary-filled wick as a fluid, wherein the outer surface of the tube shell has a plurality of depressions.

Orderly arranged micro-concavities The outer surface of the trapped heat-control tube of the present invention forms a capillary knot to evacuate; the other end seal of the tube is rough with the shell surface of the previous heat pipe, and the surface of the heat pipe is uniform, so that the “embodiment provides The method is to construct a complex structure as the entrance to the tube, and the heat transfer effect of the surface area of the technical phase is beneficial to the shell and tube table of Ai-pi Hiroko.) [The goods include the following steps: provide a middle * 4 small concave Officials; small depressions arranged in an order at φ; splitting the suction wick in Zhongyun #, Jiashangyu, y; and twisting one end of the hollow tube η,, ^ ^ in 'and filling the tube with an appropriate amount of liquid as Work, free scale, L '' 丨 L limbs, and seal Zhongyun as a fluid in the tube. In comparison, the heat pipe provided by the present invention has: rot = 2 micro ㈣, which makes the shell surface 2 ", radiation, convection and conduction, and the ratio; another 'multiple depressions are arranged in an orderly manner, and the heat pipes are evenly arranged to conduct heat The following describes the first embodiment of the heat pipe provided by the present invention with reference to the drawings: Please refer to the second and third figures. The heat pipe 20 provided by the present invention includes a tube shell 21, a capillary structure wick 22, and work. Fluid (unlabeled), the surface of the tube shell 21 has a plurality of micro-recesses 23 arranged in an orderly manner, and the diameter of the micro-recesses 23 is less than 100 micrometers, preferably less than 1 micrometer; 1 wall thickness is 1/10, preferably less than 10 microns. Tube shell 2 1 is generally a copper tube, and different materials can be used according to different needs.

200533880 V. Description of the invention (4) Materials such as Ming, steel, carbon steel, non-recorded steel, iron, record, titanium, etc. and their alloys. The radial cross-section of the tube housing 21 can be a standard circle or a special shape, such as oval, square, triangle, etc. The pipe diameter is 2mm ~ 200mm, and the pipe length can be from several millimeters to tens of meters. This embodiment adopts a round copper pipe with a diameter of 4 mm and a length of 50 mm. The outer surface of the copper pipe is formed with a plurality of tiny depressions arranged in an orderly manner. The wick 22 may be a wire mesh type, a groove type, or a sintered type.

Wire mesh type wicks are relatively easy to make. The wire mesh with a fixed mesh number purchased in the market is generally made of copper, stainless steel, or barbed wire, and can be selected based on the compatibility of the working fluid of the heat pipe. After the screen is purchased, it is cleaned and necessary processed, and then rolled into the required shape and inserted into the heat pipe. It is very important that the wick is closely attached to the inner wall of the tube, especially in the evaporation section. If the wick is unevenly attached to the inner wall of the tube, local overheating will occur. The grooved wick is in the form of an axial groove or an annular groove. Pumping grooves are formed by extrusion and broaching. Circumferential grooves are generally engraved into a spiral shape for easy processing.

The porosity of the sintered wick is generally 40 ~ 50%, which is made by firing a large amount of w metal powder particles. Appropriate selection of metal powder particles can result in wicks with different void sizes. The sintering temperature is generally 100 ° C to 200 ° C lower than the melting point of the sintering material. This embodiment adopts a copper powder sintered wick. Heat pipes can use liquids such as pure water, ammonia, methanol, acetone, or heptane as working fluids, or particles of thermally conductive materials, such as copper powder, can be added to the liquid to increase its thermal conductivity. This embodiment uses pure water as the working fluid.

Page 8 200533880 V. Description of the invention (5) Please refer to the eighth figure. The method for preparing the heat pipe 20 provided by the present invention includes the following steps: Step 1. Provide a hollow pipe; the hollow pipe is used as a heat pipe shell. Including copper tube, Ming tube, steel tube, stainless steel tube, iron tube, recording tube, titanium tube or its alloy tube, etc .; the radial section of the hollow tube can be a standard circle or a special shape, such as oval, square, triangle Etc .; the pipe diameter is 2mm ~ 200mm, and the pipe length can be from several millimeters to tens of meters. The hollow tube provided in this embodiment is a round copper tube.

Step 2. A screen printing method is used to form a plurality of microscopic depressions arranged in an order on the outer surface of the hollow tube. The screen printing method first uses laser processing to make a plate to form an array of screen sieve holes with a very small interval, wherein the diameter of the sieve holes is less than 100 micrometers, preferably less than 1 micrometer; and then ferrous chloride solution is used as the printing solution. The screen sieve is reprinted on the outer surface of the copper tube. After an appropriate reaction time, the ferrous vaporized printing liquid corrodes the copper tube, causing the outer surface to form a plurality of microscopic depressions in an orderly arrangement. And the depth required by the micro depressions is determined, the printing solution has a strong corrosion ability, and the shorter the reaction time is required. The present invention needs to ensure that the depth of the micro depressions is less than 1/10 of the wall thickness of the shell, and the depth of Youya micro depressions is less than 10 microns. The reaction array should not be too long. Step 3. Wash the hollow tube and remove the printing liquid. Step 4. A capillary structure is formed on the inner wall of the hollow tube as the liquid wick. This embodiment uses a sintering method to form the liquid wick. The general method of sintering is: insert a core rod (a stainless steel core rod can be used) in the center of the copper tube. The thickness of the core rod determines the size of the inner diameter of the steam cavity in the future, and then forms the core rod and the tube wall.

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V. Description of the invention (6) The annular space is filled with metal copper powder to be sintered. The core rod is fixed with a bracket and sent to a heating furnace. It is sintered under the protection of hydrogen for about half an hour. The sintering temperature is 81 ° C ~ 88 0 ° C. Take the tube out of the furnace, pull it out after cooling, and sinter it in the furnace for about an hour to obtain a sintered layer on the inner wall of the tube shell. The sintered layer has a capillary structure and can be used as a heat pipe wick. Step 5. Seal one end of the hollow tube and evacuate the inside of the tube. Step 6. Fill an appropriate amount of liquid into the tube as the working fluid; the liquid includes pure water, ammonia, methanol, acetone, or heptane. Pure water is used as the working fluid in this implementation. Λ% $ Step 7. Seal the other end of the hollow tube and seal the working fluid in the tube 'to form the heat pipe 21 as shown in the second and third figures. It is also possible to use screen printing to form a plurality of micro-depressions arranged in order on the surface of the pipe before forming the hollow pipe, and then shape the pipe so that the surface with the micro-depressions in plural order forms the outer surface of the hollow pipe. Thereby, a hollow tube having a plurality of minutely arranged arrays on the outer surface is formed, and then step / step 4 to step 7 is performed to form a heat pipe having a plurality of minutely arranged arrays on the outer surface of the shell. ^ It can be understood that 'through the above method, it is also possible to form a hollow hollow tube having a plurality of ordered arrays on the inner surface or the inner and outer surfaces, and then perform steps 4 to 7 to form a tube shell inner wall surface or inner and outer wall. The surface has a plurality of tiny recessed heat pipes arranged in order. ^ Please refer to the fourth and fifth figures. The heat pipe 30 provided in the second embodiment of the present invention includes a tube shell 31, a capillary wick 32 closely attached to the inner wall of the tube shell 31, and a capillary wick filled 32 2 and Working fluid sealed in the shell 31 (Figure 200533880

V. Description of the invention (7) (not shown) 'wherein the shell 31 is a square tube' and its surface has a plurality of minute depressions 3 3. The capillary wick 32 is a groove-type liquid absorbing μ, and the groove is formed on the inner wall of the tube shell by spreading pressure and broaching. The working fluid is basically the same as the method for producing the heat pipe 30 and the method for producing the heat pipe 20. The difference is that the printing liquid used in step 2 is a phosphoric acid solution and the tube is squeezed and drawn in step 4 The inner wall of the shell forms a groove-type capillary α, 70, 70, 70, and 60 °. Please refer to FIG. 6 and FIG. Capillary wick 42; and the work flow that fills the capillary wick 42 and is sealed in the shell 41 ^ (not shown) 'where the shell 41 is a triangular stainless steel tube with an orderly arrangement of H on the surface Of tiny depressions 43. The capillary wick 42 is a barbed wire. The barbed wire has good elasticity and can be closely adhered to the inner wall of the shell 41 after being inserted into the shell 41. The working fluid is Cgang. The method for preparing the heat pipe 40 is basically the same as the method for preparing the heat pipe 20. The difference is that the printing liquid used in step 2 is gas and water and the method in step 4 is filled with a wire mesh to form a capillary wick. In addition to typical heat pipes, there are gravity heat pipes (that is, the two-phase closed thermosiphon's evaporation section is placed below the condensation section during operation), rotating heat pipes and separate heat pipes, etc. The above-mentioned heat pipe has a capillary structure without liquid absorption core. After the working fluid condenses, it relies on gravity or centrifugal force to return. The material of this special heat pipe shell is not fundamentally different from that of ordinary heat pipes, so the surface of the special heat pipe shell can also form a plurality of micro-depressions arranged in order to increase the surface area of the shell and improve the heat conduction efficiency of the heat pipe.

Page Π 200533880 V. Description of the invention (8) Because the surface of the heat pipe shell is formed by a plurality of micro depressions through corrosion, the surface of the pipe shell is rough, and the surface area is increased, which is conducive to heat radiation, convection and conduction, thereby increasing the heat pipe heat conduction efficiency; The small depressions are arranged in an orderly manner and evenly arranged, so that the heat pipe shell conducts heat evenly. In summary, the present invention has indeed met the requirements for an invention patent, and a patent application was filed in accordance with the law. However, the above are only the preferred embodiments of the present invention, and cannot be used to limit the scope of patent application in this case. For those who are familiar with the skills of this case, equivalent modifications or changes made in accordance with the spirit of the present invention,

Page 12 200533880 Brief description of the diagram The first diagram is a schematic diagram of the working principle of a conventional heat pipe. The second figure is a schematic radial sectional view of the heat pipe according to the first embodiment of the present invention. The third figure is an enlarged schematic view of a heat pipe surface according to the first embodiment of the present invention. The fourth figure is a schematic radial sectional view of a heat pipe according to a second embodiment of the present invention. The fifth diagram is an enlarged schematic view of a heat pipe surface according to a second embodiment of the present invention. The sixth diagram is a schematic radial sectional view of a heat pipe according to a third embodiment of the present invention. The seventh diagram is an enlarged schematic view of a heat pipe surface according to a third embodiment of the present invention. The eighth diagram is a flowchart of a method for preparing a heat pipe according to the present invention. [Symbol description of main components] Heat pipe 20, 30, 40 Shell 21, 31, 41 Liquid wick 2 2, 3 2, 4 2 Micro depressions 2 3, 3 3, 4 3

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Claims (1)

200533880 VI. Scope of patent application 1. A heat pipe, which includes a hollow tube shell; a capillary wick; and a working fluid sealed in the tube shell; wherein the surface of the tube shell has a plurality of microscopic depressions arranged in an orderly manner. 2. The heat pipe according to item 1 of the scope of patent application, wherein the diameter of the minute depression is less than 100 microns. 3. The heat pipe according to item 2 of the scope of patent application, wherein the diameter of the minute depression is preferably less than 1 micron. 4. The heat pipe according to item 1 of the scope of patent application, wherein the depth of the minute depression is less than 10 microns. 5. The heat pipe as described in item 1 of the scope of patent application, wherein the material of the shell includes copper, Ming, iron, nickel, titanium, carbon steel, non-recorded steel and other metals or alloys. 6. The heat pipe according to item 1 of the scope of patent application, wherein the radial cross section of the shell includes a standard circle, square or triangle. 7. The heat pipe according to item 1 of the scope of patent application, wherein the capillary wick is a grooved type, a wire mesh type or a sintered type. 8. The heat pipe according to item Γ of the patent application scope, wherein the liquid in the working fluid includes water, acetone or heptane. 9. A heat pipe includes a tube shell and a heat pipe working liquid sealed in the tube shell, wherein the surface of the tube shell has a plurality of ordered depressions arranged in an orderly manner. 1 0 · —a method for preparing a heat pipe, comprising: ·· providing a hollow pipe; forming a plurality of ordered depressions on the outer surface of the hollow pipe; Page 14 200533880 6. Scope of patent application: A capillary structure is formed on the inner wall of the hollow tube as a wick; the end of the hollow tube is sealed and the inside of the tube is evacuated; a suitable amount of liquid is filled into the tube as a working fluid; and The other end of the empty tube is sealed, and the working fluid is sealed in the tube. 1 1. The method for preparing a heat pipe as described in item 10 of the scope of the patent application, wherein a screen printing method is used to form a plurality of ordered depressions on the outer surface of the hollow pipe. 1 2. The method for preparing a heat pipe according to item 11 of the scope of patent application, wherein the screen printing method includes the steps of: making a plate, forming a plurality of screens L with extremely small spacing and orderly arrangement on the screen; printing, screen printing and When the hollow tube contacts, the printing liquid is printed on the outer surface of the hollow tube through the sieve holes, and the above-mentioned orderly arranged sieve holes are reprinted on the outer surface of the hollow tube; rot #, the printing liquid rots the hollow tube to make the outer surface of the hollow tube A plurality of tiny depressions arranged in order. 1 3. The method for preparing a heat pipe as described in item 12 of the scope of patent application, wherein the method of making ~ plate, ¾: is a laser processing method. 14. The method for preparing a heat pipe according to item 12 of the scope of the patent application, wherein the material of the hollow pipe is copper, and the printing liquid used for printing is a vaporized ferrous solution. 1 5. The method for preparing a heat pipe as described in item 12 of the scope of the patent application, wherein the material of the hollow pipe is aluminum, and the printing solution used for printing is a phosphoric acid solution. 16. The method for preparing a heat pipe as described in item 12 of the scope of patent application, wherein the hollow pipe is made of stainless steel, and the printing liquid used for printing is gas and water. Page 15 200533880 VI. Scope of patent application 1 7. The method for preparing a heat pipe as described in Item 12 of the scope of interest, which further includes cleaning after the corrosion to remove the printing liquid remaining on the outer surface of the hollow pipe. 1 8. A method for preparing a heat pipe, comprising: providing a metal plate; forming a plurality of micro-depressions arranged in order on at least one surface of the metal plate; forming the metal plate into a hollow tube; A capillary structure is formed on the inner wall of the hollow tube as a wick; one end of the hollow tube is sealed and the inside of the tube is evacuated; a suitable amount of liquid is filled into the tube as a working fluid; and the other end of the hollow tube is sealed to seal the working fluid. In the tube. 19. The method for preparing a heat pipe as described in item 18 of the scope of the patent application, wherein screen printing is used to form a plurality of ordered depressions on the surface of the metal plate. 2 〇. The method for preparing a heat pipe according to item 19 of the scope of patent application, wherein the screen printing method includes the steps: Plate making, forming a plurality of sieve iLs with extremely small spacing and orderly arrangement on the screen; printing, the screen is in contact with the metal plate, and the printing liquid is printed on the surface of the metal plate through the sieve holes, and the ordered sieve holes are reprinted on the metal plate Surface; Corrosion, the printing solution corrodes the tube shell, causing the surface of the metal plate to form a plurality of tiny depressions in an orderly arrangement. 2 1. The method for preparing a heat pipe as described in item 20 of the scope of patent application, wherein Page 16 200533880 6. Scope of Patent Application The version method is laser processing method. 2 2. The method for preparing a heat pipe as described in Item 20 of the scope of patent application, wherein the metal plate is a copper plate and the printing liquid used for printing is a vaporized ferrous solution. 2 3. The method for preparing a heat pipe as described in Item 20 of the scope of patent application, wherein the metal plate is an aluminum plate, and the printing solution used for printing is a phosphoric acid solution. 2 4. The method for preparing a heat pipe according to item 20 of the scope of patent application, wherein the metal plate is a non-recording steel plate, and the printing liquid used for printing is gas and water. 2 5. The method for preparing a heat pipe as described in item 20 of the profit scope, wherein the corrosion is advanced after corrosion Page 17