US20100212871A1

US20100212871A1 - Heat pipe and manufacturing method thereof

Info

Publication number: US20100212871A1
Application number: US12/494,339
Authority: US
Inventors: Yi-Shih Hsieh; Yong-Jian Wang
Original assignee: Furui Precise Component Kunshan Co Ltd; Foxconn Technology Co Ltd
Current assignee: Furui Precise Component Kunshan Co Ltd; Foxconn Technology Co Ltd
Priority date: 2009-02-20
Filing date: 2009-06-30
Publication date: 2010-08-26
Also published as: CN101813429B; CN101813429A

Abstract

A heat pipe includes a sealed hollow casing, a wick structure lining an inner surface of the casing and a working medium contained in an interior of the casing. The casing includes an elongated main body having an elongated opening extending axially in the main body and a transparent cover fixed onto the main body and sealing the opening of the main body. The wick structure is provided by only lining an inner surface of the main body of the casing.

Description

BACKGROUND

1. Technical Field
The disclosure relates to heat pipes, and more particularly to a heat pipe that states of a working medium contained in the heat pipe is visible and a manufacturing method thereof.
2. Description of Related Art
With continuing development of the electronic technology, electronic components such as CPUs generate more and more heat that is required to be dissipated immediately. Heat pipes are commonly used for cooling the electronic components for their excellent heat transfer performances.
Commonly, a heat pipe includes a sealed aluminum or copper container with an internal surface lined with a capillary wick mesh and a working medium contained in the container. When used, one end of the heat pipe is thermally attached to an electronic component to absorb heat therefrom, and the other end of the heat pipe is thermally connected to the heat sink. As the heat pipe absorbs heat at the one end thereof, the working medium is vaporized, and a pressure gradient is formed in the heat pipe. This pressure gradient forces the vapor to flow along the heat pipe from the one end to the other end where the vapor condenses and gives out its latent heat of vaporization. The working medium is then returned back to the one end of the heat pipe via the capillary forces developed in the wick mesh. Thus, the heat generated by the electronic component can be rapidly transferred to the heat sink via the heat pipe for further dissipating to ambient air.
Since the container is made of aluminum or copper, states of the working medium in the container is not visual observation from outside of the heat pipe during operation of the heat pipe. The states of the working medium in the container can only be deduced by phase change theory, which is not convenient for real-time observation or real-time monitoring a working process of the heat pipe. Furthermore, an aging degree of the heat pipe is unable to judge. After the heat pipe being used a period of time, the heat pipe usually results in overheat and even in damage of the electronic component before the users know an excessive aging of the heat pipe.
It is thus desirable to provide a heat pipe which can overcome the described limitations.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric, assembled view of a heat dissipation device according to an exemplary embodiment of present disclosure.

FIG. 2 is an isometric, assembled view of a heat pipe of the heat dissipation device of FIG. 1.

FIGS. 3A-3C are views respectively showing steps of a manufacturing method of the heat pipe of FIG. 2.

DETAILED DESCRIPTION

Reference will now be made to the drawing figures to describe the present heat dissipation device and heat pipe thereof in detail.
FIG. 1 illustrates a heat dissipation device in accordance with an exemplary embodiment of the disclosure. The heat dissipation device is for dissipating heat generated by an electronic component 20. The heat dissipation device includes a fin unit 30, a heat pipe 10 thermally connecting the electronic component 20 to the fin unit 30, and a centrifugal fan 40 for providing an airflow flowing through the fin unit 30 to take heat away.
Referring to FIG. 2, the heat pipe 10 includes a sealed hollow casing 11, a wick structure 12 formed on an inner surface of the casing 11, and a working medium 17 contained in an interior of the casing 11. The heat pipe 10 includes an evaporating section 13, an adiabatic section 15 and a condensing section 14 along an axial direction of the casing 11. The adiabatic section 15 is located between the evaporating section 13 and the condensing section 14.
A cross-section of the casing 11 is substantially “D” shaped. The casing 11 includes an elongated main body 111 having an elongated opening 110 extending from the evaporating section 13 to the condensing section 14 and a transparent cover 112 for hermetically sealing the opening 110 of the main body 111.
A cross-section of the main body 111 is about “C” shaped. The main body 111 is made of high thermally conductive material such as copper or aluminum. The opening 110 is defined in a top side of the main body 111 and extends along the axial direction of the main body 111. An outline of the opening 110 includes a first linear portion 114, a second linear portion 115 parallel to the first linear portion 114, and first and second arced portions 116, 117 respectively connected between two opposite ends of the first and second linear portions 114, 115. A length of the opening 110 substantially equals to a length of the main body 111. However, a width of the opening 110, i.e., a distance between the first and second linear portions 114, 115, is smaller than a diameter of the main body 111. The wick structure 12 is only provided lining an inner surface of the main body 111 of the casing 11. The wick structure 12 includes a plurality of micro grooves defined in the inner surface of the main body 111. The micro grooves are evenly arranged along a circumference direction of the main body 111 of the casing 11. Each of the micro grooves extends along the axial direction of the main body 111 from the evaporating section 13 to the condensing section 14. Alternatively, the wick structure 12 can be other known type wicks, such as screen mesh, sintering powders, etc.
The transparent cover 112 is a rectangular flat plate. The transparent cover 112 is made of transparent materials such as acryl, glass or the like. A size of the transparent cover 112 is slightly larger than that of the opening 110 of the main body 111 for hermetically covering on the opening 110 of the main body 111. Alternatively, the size of the transparent cover 112 can be equal to that of the opening 110. The transparent cover 112 and the main body 111 cooperatively define a sealed space in the interior of the casing 11 with the wick structure 12 and working medium 17 received therein.
The working medium 17 can be water, alcohol or methanol. The wick structure 12 is saturated with the working medium 17, which acts as a heat carrier when undergoing phase transitions between liquid state and vaporous state during operation of the heat pipe 10. The working medium 17 and the wick structure 12 contained in the interior of the casing 11 are visually observable from the top side of the heat pipe 10 via the transparent cover 112.
Referring back to FIG. 1, when assembled, the fin unit 30 is arranged at an air outlet 42 of the centrifugal fan 40. The fin unit 30 defines a slot 32 at a middle of a top surface thereof. The slot 32 has a shape and a size respectively corresponding to a shape and a size of the main body 111 of the casing 11 of the heat pipe 10. The condensing section 14 and the adiabatic section 15 of the heat pipe 10 are receiving in the slot 32, with an outer surface of the main body 111 at the condensing and adiabatic sections 14, 15 contacting with the top surface of the fin unit 30 around the slot 32. The transparent cover 112 protrudes out of the slot 32 of the fin unit 30 and faces a top side of the heat dissipation device. An outer surface of another end of the main body 111 corresponding to the evaporation section 13 of the heat pipe 10 is thermally contacted with a top surface of the electronic component 20.
During operation, the main body 111 at the evaporation section 13 of the heat pipe 10 absorbs heat from the electronic component 20, the working medium 17 is vaporized to vapor, and a pressure gradient is formed in the interior of the casing 11. This pressure gradient forces the vapor to flow along the casing 11 from the evaporating section 13 to the condensing section 14, where the vapor condenses back to liquid and gives out its latent heat of vaporization. The liquid is then returned back to the evaporating section 13 under a capillary force of the wick structure 12 of the heat pipe 10. Such a process is repeated so that heat is continuously transferred from the evaporating section 13 into the condensing section 14. Thus, the heat generated by the electronic component 20 is rapidly transferred to the fin unit 30 via the heat pipe 10 for further dissipating to the ambient air by the airflow generated by the fan 40.
Due to the transparent cover 112 formed on the top side of the casing 111, a phase changing process of the working medium 17 in the interior of casing 111, i.e., the working medium 17 vaporized to vapor at the evaporating section 13 to flow towards the condensing section 14 along the casing 111, and then condensed back to liquid at the condensing section 14 to flow back towards the evaporating section 13 under the capillary force of the wick structure 12, is visually observable from the top side of the heat pipe 10. Thus, it is intuitively to know a working principle of the phase transition of the working medium 17 in the interior of the casing 111 of the heat pipe 10 and accurately to know a working process of the heat pipe 10. Therefore, the heat pipe 10 can be better used in educational training for learners or in researching and experimenting for researchers. Furthermore, the phase changing process of the working medium 17 in the interior of the heat pipe 10 can be recorded by a video camera or camcorder from outside of the heat pipe 10 via the transparent cover 112, which provides more intellectualized, more convenient, and highly effective learning for more learners and researchers. Moreover, users can well know a working performance of the heat pipe 10 by observing speed of the phase changing process of the working medium 17 via the transparent cover 112 and easily judge an aging degree of the heat pipe 10 after the heat pipe 10 has been used a period of time. Thus, the users can easily judge whether the heat pipe 10 needs to be replaced or repaired to ensure that the electronic component 20 can always work normally.
FIGS. 3A-3C respectively show steps for a manufacturing method of the heat pipe 10. Referring to FIG. 3A, a rudimentary rounded hollow pipe body 60 with wick structure lining against an inner surface thereof is provided. The pipe body 60 is made of high thermally conductive material such as copper or aluminum. A cross section of the pipe body 60 is annular. One end of the pipe body 60 is enclosed, and the other end of the pipe body 60 is open. Referring to FIG. 3B, a top part 62 of the pipe body 60 is cut off from the pipe body 60 along an axial direction of the pipe body 60 via a cutting process. An opening 110 is thus formed on a remaining part 64 of the pipe body 60 along a cut plane of the pipe body 60. The remaining part 64 forms the main body 111 of the casing 11 of the heat pipe 10 of FIG. 2. The top part 62 has an arced cross-section which is smaller than a half cross-section of the pipe body 60. Then, residual stresses of the remaining part 64 of the pipe body 60 caused by the cutting process are released by stress relief annealing. Referring to FIG. 3C, a transparent cover 112 having a shape corresponding to the opening 110 of the main body 111 of the casing 11 is provided. The transparent cover 112 is fixedly affixed to the main body 111 by sealant and thus seals the opening 110, to thereby form the casing 11 of the heat pipe 10 of FIG. 2. Subsequently, the working medium 17 such as water, alcohol or methanol, is injected into the casing 11 via the open end, and finally, the casing 11 is vacuumed and the open end of the casing 11 is hermetically sealed so as to form the heat pipe 10 with the transparent cover 112 arranged on the top side thereof as shown in FIG. 2.
It is to be understood, however, that even though numerous characteristics and advantages of the disclosure have been set forth in the foregoing description, together with details of the structure and function of the embodiments, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.

Claims

1. A heat pipe comprising:

a sealed hollow casing comprising an elongated main body having an elongated opening extending axially in the main body and a transparent cover fixed onto the main body and sealing the opening of the main body;

a wick structure lining an inner surface of the main body of the casing; and

a working medium contained in an interior of the casing.

2. The heat pipe as described in claim 1, wherein the transparent cover is made of glass or acryl.

3. The heat pipe as described in claim 1, wherein a cross-section of the casing is “D” shaped.

4. The heat pipe as described in claim 1, wherein a cross-section of the main body is “C” shaped, and the transparent cover is planar.

5. The heat pipe as described in claim 1, wherein an outline of the opening has two linear portions extending axially and parallel to each other and two arced portions respectively connected between two opposite ends of the two linear portions.

6. The heat pipe as described in claim 1, wherein a width of the opening is smaller than a diameter of the main body of the casing.

7. A method of manufacturing a heat pipe, comprising:

providing a rudimentary rounded hollow pipe body with a wick structure lining against an inner surface thereof;

cutting a part of the pipe body along an axial direction of the pipe body out of the pipe body, an opening being formed on a remaining part of the pipe body;

releasing residual stresses of the remaining part of the pipe body;

providing a transparent cover having a shape corresponding to the opening of the main body, and affixing the cover to the remaining part of the pipe body for sealing the opening, cooperatively the remaining part of the pipe body and the cover forming a casing;

injecting a working medium into the casing; and

vacuuming and hermetically sealing the casing.

8. The heat pipe as described in claim 7, wherein the pipe body is made of copper or aluminum, and the transparent cover is made of glass or acryl.

9. The heat pipe as described in claim 7, wherein the part has a cross-section smaller than a half cross-section of the pipe body.

10. The heat pipe as described in claim 7, wherein the transparent cover is plate shaped.

11. The heat pipe as described in claim 10, wherein a cross-section of the casing is “D” shaped.