HEAT PIPE AND PROCESSING METHOD THEREOF
A heat pipe processing method includes steps of providing a metal tube with openings at two ends, where an inner wall of the metal tube has a capillary structure surface; and oxidizing the capillary structure surface so as to form an oxidized structure surface. In another embodiment, a heat pipe includes is provided, including a metal tube, a working fluid, and a first oxidized structure. An inner wall of the metal tube has a first area. The working fluid is filled in the metal tube. The first oxidized structure is formed on the inner wall defined by the first area, and the working fluid has a first contact angle on the first oxidized structure.
This application also claims priority to Taiwan Patent Application No. 101145061 filed in the Taiwan Patent Office on Nov. 30, 2012, the entire content of which is incorporated herein by reference.
TECHNICAL FIELDThe disclosure relates to a heat conduction technology, and in particular, to a heat pipe and a processing method thereof.
RELATED ARTWith the evolution of the integrated circuit package technology and process, internal circuits are becoming more intensified and miniaturized, so that the processing speed and frequency of electronic components are rapidly improved. However, when the miniaturized electronic components are running with a high frequency, the heat generation per unit area of the components is significantly increased, resulting in the problem that the hotspot on the chip. The statistical result shows that, up to 55% of damages to electronic products are caused by overheat. According to the research, every 10° C. of temperature decrease improves the efficiency of the processing chip by 1 to 3%. Therefore, during operation, the electronic components require a set of effective heat dissipation design to solve the problem of excessively centralized heat source, thereby ensuring the reliability, stability and service life of the electronic device in long-term use.
Heat pipe products (such as a heat pipe or a plate heat pipe) are featured in rapidly conduction of heat generated by a heat source to a heat dissipation end, and therefore are widely applied to current components that produce highly exhaust heat and require rapid heat dissipation, for example, electronic components, light emitting diodes (LEDs), and solar panels. The internal of a heat pipe is a low-pressure sealed space, and has a capillary structure and a working fluid filled therein. The internal low-pressure state greatly decreases the vaporization temperature of the working fluid. During the operation, the working fluid evaporates in an evaporation area upon being heated, taking away a lot of latent heat. The vapor of working fluid flows to a condensation area due to a local high pressure in the evaporation area, and condenses in the condensation area upon being cooled. The capillary structure enables the condensed working fluid to flow back to the evaporation area, so that the evaporation area is continuously provided with the working fluid, thereby maintaining a closed circulating system with one end for evaporation and one end for condensation.
In application, the maximum allowable heat flux of the heat pipe is restricted by different limitations. Typically, the copper-water heat pipe used in common electronic heat dissipation is usually restricted by the capillary limit. As the heat flux increases, the evaporation rate and the mass flow rate of the working fluid increase; if the evaporation rate and mass flow rate of the working fluid exceeds the maximum amount of working fluid that the capillary force is capable of carrying back to the evaporation area, the evaporation area will dry out, and as a result, the heat pipe operation fails.
SUMMARYThe disclosure is directed to a heat pipe and a processing method thereof, where a feature of a capillary structure surface of an existing heat pipe or vapor chamber is changed through a chemical reaction, so that a working fluid in the heat pipe and a modified capillary structure of an inner wall of the heat pipe have different wettability, thereby improving a capillary pressure difference that is used for driving the working fluid to flow and provided by the capillary structure in the pipe, hence significantly improving the maximum heat transfer rate of the heat pipe.
In an embodiment, the disclosure provides a heat pipe processing method, which includes steps of: providing a metal tube with openings at two ends, where an inner wall of the metal tube has a capillary structure surface; and oxidizing the capillary structure surface so as to form an oxidized structure surface.
In another embodiment, the disclosure provides a heat pipe, which includes a metal tube having a first area on an inner wall thereof; a working fluid, filled in the metal tube; and a first oxidized structure, formed on the inner wall defined by the first area, where the working fluid on the first oxidized structure surface has a first contact angle.
In order to enable the examiner to further understand the features, objectives and functions of the disclosure, related detailed structures and design concepts and principles of the equipment of the disclosure are described in detail below, so that the examiner can understand the features of the disclosure. The detailed description is provided as follows:
Referring to
Referring to
Referring to
Cu+(NH4)2S2O8+NaOH→Cu(OH)2+2Na2SO4+2NH3+2H2O (1)
In another embodiment, in the oxidized structure surface, the blue copper hydroxide microstructure may further be dehydrated to form a black copper oxide microstructure, and a reaction equation thereof is shown in Equation (2) below.
Cu+(NH4)2S2O8+NaOH→Cu(OH)2+2Na2SO4+2NH3+2H2O
Cu(OH)2→CuO+H2O (2)
Another embodiment of the oxidization in Step 21 is basically similar to the method in above Equations (1) and (2), and the difference lies in that, in this embodiment, the copper surface is oxidized to be the blue copper hydroxide microstructure by adjusting the composition of the mixed reaction solution, the concentration, ratio, reaction time, and reaction temperature of the solution of potassium persulfate and potassium hydroxide, as shown in Equation (3) below. It should be noted that, the potassium persulfate may be substituted by sodium persulfate, and the potassium hydroxide may also be substituted by sodium hydroxide.
Cu+K2S2O8+2KOH→Cu(OH)2+2K2SO4 (3)
In another embodiment, in the oxidized structure surface, the copper hydroxide microstructure may further be dehydrated to form a black copper oxide microstructure, and a reaction equation thereof is shown in Equation (4) below.
Cu+K2S2O8+2KOH→Cu(OH)2+2K2SO4
Cu(OH)2→CuO+H2O (4)
In addition, another embodiment of the oxidization in Step 21 is to perform oxidization through temperature processing, that is, the oxidization in this embodiment does not require any reaction solution; instead, the oxidizing effect is achieved by controlling the temperature and time. In an embodiment, with two ends unclosed, a metal tube having a traditional capillary structure is placed into a high-temperature oven in an aerobic environment (such as an atmosphere environment), after an oxidizing temperature and an oxidizing time, the capillary structure on the inner wall of the metal tube is modified to be a metal oxide. Taking copper as an example, the copper may be reacted for 0.5 to 6 hours under a temperature ranging from 250 to 450° C., so that the surface of the inner wall of the copper tube is modified to be copper oxide, and the reaction equation is shown in Equation (5) below.
A contact angle between the oxidized structure surface formed according to foregoing Equation (1) to Equation (5), in which copper is taken as an example, and the oxidized microstructure formed by water and copper on the surface is close to zero degree, which improves the hydrophilicity of the modified oxidized capillary structure.
Referring to
As shown in 5C, a slash area inside the tube wall defined by the area 800 represents the second oxidized structure 83 formed on the inner wall. After Step 21, the oxidized structure formed in the area 801 may be regarded as a hydrophilic oxidized structure. After Step 22, compared with the oxidized structure in the area 801, the oxidized structure formed in the area 800 may be regarded as a hydrophobic oxidized area. Referring to
Referring to
Although the flows shown in
Referring to
Referring to Equation (6) below, Equation (6) is used for calculating a capillary pressure difference in the heat pipe.
ΔP is a capillary pressure difference; σ is a surface tension; θe is a contact angle between the working fluid and the capillary structure in the evaporation area; θc is a contact angle between the working fluid and the capillary structure in the condensation area; r is a capillary radius; evap represents the evaporation area; and cond represents the condensation area. In the conventional heat pipe, the amount of the filled working fluid is as high as the capillary structure; when the evaporation area is heated and the working fluid is volatilized, the contact angle of the working fluid in the evaporation area may be smaller than the contact angle in the condensation area, thereby generating a capillary pressure difference and driving the operation of the working fluid. Different capillary structures have different capillary radiuses. The design of changing the capillary structure may be used to improve the capillary pressure difference during operation. In addition, the capillary structure in a general heat pipe is made of a uniform material, so the contact angle between the working fluid and the capillary structure is a fixed value.
According to the manner in the disclosure, with the same radius of the capillary structure and with the surface tension of the working fluid being unchanged, the working fluid can have different wettability in the condensation area and the evaporation area through chemical surface modification, that is, the contact angle in the evaporation area and that in the condensation area are changed. After substitution into Equation (6), it is detected that the effect of improving the capillary pressure difference and generating the maximum heat conduction amount can also be achieved. Taking the embodiment shown in
For example, in an embodiment, the working fluid is water, the tube material of the heat pipe is copper, and the internal of the heat pipe is provided with a groove capillary structure. A total length of the pipe is 25 cm, a pipe diameter is 6 cm, a groove height is 0.34 cm, a groove width is 0.21 cm, and the total number of grooves is 55. Through the chemical surface modification processing, the contact angle between water and copper in the condensation area can be improved to 137 degrees. If the contact angle between water and copper is fixed at 78 degrees in the evaporation area, after the contact angles are substituted into the equation, the maximum heat conduction amount is calculated. The maximum heat conduction amount of the heat pipe is 128.3 W at this time. The maximum heat conduction amount of the conventional heat pipe is only 28.4 W. Upon comparison, the heat conduction amount of the capillary structure that undergoes the chemical oxidizing modification is significantly improved.
The exemplary implementations or embodiments of the technical solutions in the disclosure used for solving the problem are described above, which are not intended to limit the scope of the disclosure. Any equivalent change and modification made without departing from the content of the application scope of the disclosure or made according to the scope of the disclosure shall fall within the scope of the disclosure.
Claims
1. A heat pipe processing method, comprising steps of:
- providing a metal tube with openings at two ends, wherein an inner wall of the metal tube has a capillary structure surface; and
- oxidizing the capillary structure surface so as to form a first oxidized structure surface.
2. The heat pipe processing method according to claim 1, wherein a material of the metal tube is copper.
3. The heat pipe processing method according to claim 1, wherein a first contact angle exists between the first oxidized structure surface and a working fluid.
4. The heat pipe processing method according to claim 3, wherein a manner for oxidizing the inner wall of the metal tube further comprises steps of:
- providing an oxidizing solution; and
- enabling the oxidizing solution to oxidize an inner wall surface of the metal tube so as to form the first oxidized structure surface.
5. The heat pipe processing method according to claim 4, wherein the oxidizing solution is one selected from a mixed solution of ammonium persulfate and sodium hydroxide, a mixed solution of ammonium persulfate and potassium hydroxide, a mixed solution of potassium persulfate and potassium hydroxide, a mixed solution of potassium persulfate and sodium hydroxide, a mixed solution of sodium persulfate and potassium hydroxide, and a mixed solution of sodium persulfate and sodium hydroxide.
6. The heat pipe processing method according to claim 4, wherein the oxidized structure surface is a surfaced formed of a metal hydroxide or a metal oxide.
7. The heat pipe processing method according to claim 4, further comprising modifying partial area of the first oxidized structure surface by using an chemical solution so as to form a second oxidized structure surface with a long chain structure, wherein the working fluid on the second oxidized structure surface has a second contact angle with the working fluid, and the second contact angle is greater than the first contact angle.
8. The heat pipe processing method according to claim 7, wherein the chemical solution is a diluted solution of fluoroalkylsiloxane, fluoroalkyltrichlorosilane, fluoroalkyldimethylchlorosilane, alkylsiloxane, alkyltrichlorosilane, alkyldimethylchlorosilane or alkyl mercaptan.
9. The heat pipe processing method according to claim 7, wherein the long chain structure is a long chain fluoroalkyl group or long chain alkyl group.
10. The heat pipe processing method according to claim 3, wherein a manner for oxidizing the inner wall of the metal tube is to place the metal tube into an aerobic environment with an oxidizing temperature, and obtaining the first oxidized structure surface after a first oxidizing time.
11. The heat pipe processing method according to claim 10, wherein the oxidizing temperature is 250° C. to 450° C., and the oxidizing time is 0.5 to 6 hours.
12. The heat pipe processing method according to claim 11, further comprising modifying partial area of the first oxidized structure surface by using an chemical solution, so as to form a second oxidized structure surface with a long chain structure, wherein the working fluid on the second oxidized structure surface has a second contact angle with the working fluid, and the second contact angle is greater than the first contact angle.
13. The heat pipe processing method according to claim 12, wherein the chemical solution is a diluted solution of fluoroalkylsiloxane, fluoroalkyltrichlorosilane, fluoroalkyldimethylchlorosilane, alkylsiloxane, alkyltrichlorosilane, alkyldimethylchlorosilane or alkyl mercaptan.
14. The heat pipe processing method according to claim 12, wherein the long chain structure is a long chain fluoroalkyl group or long chain alkyl group.
15. The heat pipe processing method according to claim 10, wherein the first oxidizing temperature is 80° C. to 150° C., and the first oxidizing time is 0 to 10 hours.
16. The heat pipe processing method according to claim 15, further comprising steps of:
- providing an oxidizing solution; and
- enabling the oxidizing solution to oxidize the first oxidized structure surface so as to form a second oxidized structure surface, wherein the working fluid on the second oxidized structure surface has a second contact angle, and the second contact angle is smaller than the first contact angle.
17. The heat pipe processing method according to claim 16, wherein the oxidizing solution is one selected from a mixed solution of ammonium persulfate and sodium hydroxide, a mixed solution of ammonium persulfate and potassium hydroxide, a mixed solution of potassium persulfate and potassium hydroxide, a mixed solution of potassium persulfate and sodium hydroxide, a mixed solution of sodium persulfate and potassium hydroxide, and a mixed solution of sodium persulfate and sodium hydroxide.
18. The heat pipe processing method according to claim 16, wherein the second oxidized structure surface is a surface formed of a metal hydroxide or a metal oxide.
19. A heat pipe, comprising:
- a metal tube, having a first area on an inner wall thereof;
- a working fluid, filled in the metal tube; and
- a first oxidized structure, formed on the inner wall defined by the first area, wherein the working fluid has a first contact angle on the first oxidized structure.
20. The heat pipe according to claim 19, wherein the first oxidized structure is an oxidized structure formed of a metal hydroxide or a metal oxide.
21. The heat pipe according to claim 20, wherein the inner wall of the metal tube further has a second area and a second oxidized area that is formed on the inner wall defined by the second area; the working fluid has a second contact angle on the second oxidized structure, and the second contact angle is greater than the first contact angle.
22. The heat pipe according to claim 21, wherein the second oxidized structure is a structure surface with a long chain structure.
23. The heat pipe according to claim 22, wherein the long chain structure is a long chain fluoroalkyl group or long chain alkyl group.
24. The heat pipe according to claim 19, wherein a material of the metal tube is copper.
25. The heat pipe according to claim 24, wherein the first oxidized structure is copper oxide or cuprous oxide.
26. The heat pipe according to claim 19, wherein the first oxidized structure is a structure surface with a long chain structure.
27. The heat pipe according to claim 26, wherein the long chain structure is a long chain fluoroalkyl group or long chain alkyl group.
Type: Application
Filed: Jul 19, 2013
Publication Date: Jun 5, 2014
Inventors: Cheng-We TU (Taipei City), Kuo-Hsiang Chien (Hsinchu County), Ming-Shan Jeng (Sijhih City)
Application Number: 13/946,045
International Classification: F28D 15/04 (20060101); C23C 8/42 (20060101);