U.S. patent application number 11/164325 was filed with the patent office on 2006-09-14 for heat pipe suitable for application in electronic device with limited mounting space.
Invention is credited to Ching-Tai Cheng, Chu-Wan Hong, Chang-Ting Lo, Jung-Yuan Wu.
Application Number | 20060201655 11/164325 |
Document ID | / |
Family ID | 36969591 |
Filed Date | 2006-09-14 |
United States Patent
Application |
20060201655 |
Kind Code |
A1 |
Hong; Chu-Wan ; et
al. |
September 14, 2006 |
HEAT PIPE SUITABLE FOR APPLICATION IN ELECTRONIC DEVICE WITH
LIMITED MOUNTING SPACE
Abstract
A mesh-type heat pipe (10) includes a casing (12), a tube (14)
located inside the casing and a screen mesh wick (16) located
between the casing and the tube. The tube defines therein a
plurality of through holes (142) and at least one cutout (144). The
wick is held against the casing by the tube. Under the support of
the tube, the wick as a whole engages closely an inner surface of
the casing, thereby establishing an effective heat transfer path
between the casing and a working fluid that is saturated in the
wick. Meanwhile, with the cutout in the tube presented, the heat
pipe incorporating such tube is easily to be bent or flattened so
as to enable the heat pipe to be applicable in electronic devices
with a limited mounting space for a cooling device, such as
notebook computers.
Inventors: |
Hong; Chu-Wan; (Shenzhen,
CN) ; Lo; Chang-Ting; (Shenzhen, CN) ; Wu;
Jung-Yuan; (Shenzhen, CN) ; Cheng; Ching-Tai;
(Shenzhen, CN) |
Correspondence
Address: |
NORTH AMERICA INTELLECTUAL PROPERTY CORPORATION
P.O. BOX 506
MERRIFIELD
VA
22116
US
|
Family ID: |
36969591 |
Appl. No.: |
11/164325 |
Filed: |
November 18, 2005 |
Current U.S.
Class: |
165/104.26 ;
165/104.21; 257/E23.088; 361/700 |
Current CPC
Class: |
H01L 23/427 20130101;
F28F 1/003 20130101; H01L 2924/00 20130101; H01L 2924/0002
20130101; H01L 2924/0002 20130101; F28D 15/046 20130101 |
Class at
Publication: |
165/104.26 ;
165/104.21; 361/700 |
International
Class: |
F28D 15/00 20060101
F28D015/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 11, 2005 |
TW |
094107449 |
Claims
1. A heat pipe comprising: a casing; a tube located inside the
casing, the tube defining therein a plurality of through holes and
at least one cutout; and a screen mesh wick located between the
casing and the tube and held by the tube against the casing.
2. The heat pipe of claim 1, wherein the at least one cutout
extends along one of circumferential and longitudinal directions of
the tube.
3. The heat pipe of claim 1, wherein the tube is divided into
multiple separate pieces by the at least one cutout.
4. The heat pipe of claim 1, wherein the tube is made of one of
organic material and metal material.
5. The heat pipe of claim 1, wherein the through holes account for
70 percent of a total surface area of the tube.
6. The heat pipe of claim 1, wherein the screen mesh wick is made
of a plurality of flexible wires by weaving technology.
7. A method for manufacturing a heat pipe comprising steps of:
providing a tube with a plurality of through holes and at least one
cutout defined therein; wrapping a screen mesh wick onto an outer
surface of the tube; and inserting the tube and the wick into a
hollow casing.
8. The method of claim 7, wherein the tube and the wick are
inserted into said casing after said casing is heated to expand
with a required extent.
9. The method of claim 7, wherein the screen mesh wick is made of a
plurality of flexible wires by weaving technology.
10. The method of claim 7, wherein the at least one cutout is
formed along one of circumferential and longitudinal directions of
the tube.
11. The method of claim 7, wherein the tube is made of one of
organic material and metal material.
12. A heat pipe for transferring heat from one section to another
section thereof, comprising: a metal casing having an inner surface
defining a hollow space therein; a screen mesh wick contacting the
inner surface of the metal casing; and a tube received in the
hollow space and pressing the wick against the inner surface of the
metal casing, wherein the tube defines a plurality of holes
therethrough and at least one elongated cutout therein.
13. The heat pipe of claim 12, wherein the at least one cutout is
defined in the tube along a circumferential direction thereof.
14. The heat pipe of claim 13, wherein the at least one cutout
extends all through the tube and divides the tube into two
pieces.
15. The heat pipe of claim 13, wherein the least one cutout is
perpendicular to an axis of the tube.
16. The heat pipe of claim 13, wherein the at least one cutout is
slanted to an axis of the tube.
17. The heat pipe of claim 12, wherein the at least one cutout is
defined in the tube along a longitudinal direction thereof.
18. The heat pipe of claim 17, wherein the at least one cutout
comprises two sections extending from two opposite ends of the tube
toward a middle thereof.
19. The heat pipe claim 17, wherein the tube comprises an
additional cutout extending along the longitudinal direction
thereof and located opposite the at least one cutout.
20. The heat pipe of claim 19, wherein each of the at least one
cutout and the additional cutout comprises two sections extending
from two opposite ends of the tube toward a middle thereof.
Description
FIELD OF THE INVENTION
[0001] The present invention relates generally to an apparatus for
transfer or dissipation of heat from heat-generating components
such as electronic components, and more particularly to a heat pipe
that is suitable for use in electronic devices that have a limited
mounting space, such as notebook computers.
DESCRIPTION OF RELATED ART
[0002] Heat pipes have excellent heat transfer performance due to
their low thermal resistance, and therefore are an effective means
for transfer or dissipation of heat from heat sources. Currently,
heat pipes are widely used for removing heat from heat-generating
components such as central processing units (CPUs) of computers. A
heat pipe is usually a vacuum casing containing therein a working
fluid, which is employed to carry, under phase transitions between
liquid state and vapor state, thermal energy from one section of
the heat pipe (typically referring to as "evaporating section") to
another section thereof (typically referring to as "condensing
section"). Preferably, a wick structure is provided inside the heat
pipe, lining an inner wall of the casing, for drawing the working
fluid back to the evaporating section after it is condensed at the
condensing section. Specifically, as the evaporating section of the
heat pipe is maintained in thermal contact with a heat-generating
component, the working fluid contained at the evaporating section
absorbs heat generated by the heat-generating component and then
turns into vapor. Due to the difference of vapor pressure between
the two sections of the heat pipe, the generated vapor moves
towards and carries the heat simultaneously to the condensing
section where the vapor is condensed into liquid after releasing
the heat into ambient environment by, for example, fins thermally
contacting the condensing section. Due to the difference of
capillary pressure developed by the wick structure between the two
sections, the condensed liquid is then drawn back by the wick
structure to the evaporating section where it is again available
for evaporation.
[0003] The wick structure currently available for the heat pipe
includes fine grooves integrally formed at the inner wall of the
casing, screen mesh or bundles of fiber inserted into the casing
and held against the inner wall thereof, or sintered powder
combined to the inner wall of the casing by sintering process. As
for the screen mesh wick, its manufacture generally involves
weaving together a plurality of pliable wires or threads such as
metal wires or synthetic fibers. In this sense, the screen mesh
wick is formed separately and is then inserted into the casing of
the heat pipe.
[0004] In the heat pipe, except the function to generate capillary
force for drawing the condensed liquid back to the evaporating
section of the heat pipe, another function of the wick structure is
to provide a heat transfer path between the casing of the heat pipe
and the working fluid that is contained in the casing and saturated
in the wick structure. Therefore, whether the wick is maintained
into intimate contact with the casing will have a great impact on
the heat transfer effect of the heat pipe. However, since the
screen mesh wick is made separately, in many cases a gap will exist
between the screen mesh wick and the casing of the heat pipe after
the screen mesh wick is inserted into the heat pipe. In order to
hold the screen mesh wick against and ultimately into close contact
with the casing of the heat pipe, retaining means are often used.
For example, a helical spring or a round tube will generally serve
this purpose. The helical spring is not satisfactory in holding the
screen mesh wick against the casing of heat pipe since it generally
cannot apply a uniform force on the wick for pressing it against
the casing due to a limited contact area between the spring and the
wick.
[0005] In many cases, a heat pipe is required to be bent into a
curved one or pressed into a flattened one in order to be
applicable in electronic devices that have very limited mounting
space, for example, in some portable electronic devices such as
notebook computers. Although the round tube could provide a more
uniform pressing force for the wick in comparison to the helical
spring, the tube generally is made of rigid material such as metals
and therefore adds difficulty to the bending or flattening work,
since the rigidity of the tube has to be overcome in order to bend
or flatten the heat pipe.
[0006] Therefore, it is desirable to provide a retaining means for
the screen mesh wick that could apply a uniform pressing force for
the wick and meantime make the bending or flattening work to the
heat pipe, if necessary, more easier.
SUMMARY OF INVENTION
[0007] A heat pipe in accordance with one embodiment of the present
invention includes a casing, a tube located inside the casing and a
screen mesh wick located between the casing and the tube. The tube
defines therein a plurality of through holes and at least one
cutout. The wick is held against the casing by the tube. Under the
support of the tube, the wick as a whole engages closely an inner
surface of the casing, thereby establishing an effective heat
transfer path between the casing and a working fluid that is
saturated in the wick. Meanwhile, with the cutout in the tube
presented, the heat pipe incorporating such tube is easily to be
bent or flattened so as to enable the heat pipe to be applicable in
electronic devices with limited mounting space for cooling device,
such as notebook computers.
[0008] Other advantages and novel features of the present invention
will become more apparent from the following detailed description
of preferred embodiment when taken in conjunction with the
accompanying drawings, in which:
BRIEF DESCRIPTION OF DRAWINGS
[0009] FIG. 1 is a longitudinal cross-sectional view of a heat pipe
in accordance with a first embodiment of the present invention;
[0010] FIG. 2 is an isometric view of the heat pipe of FIG. 1,
showing various parts thereof in the assembly process;
[0011] FIG. 3 is a side elevation view of a tube suitable for the
heat pipe of FIG. 1, according to a second embodiment of the
present invention;
[0012] FIG. 4 is a side elevation view of a tube suitable for the
heat pipe of FIG. 1, according to a third embodiment of the present
invention; and
[0013] FIG. 5 is a cross-sectional view of the tube of FIG. 4,
taken along line V-V thereof.
DETAILED DESCRIPTION
[0014] FIG. 1 illustrates a heat pipe 10 in accordance with one
embodiment of the present invention. The heat pipe 10 includes a
casing 12, a tube 14 inserted into the casing 12 and a capillary
wick 16 located between the casing 12 and the tube 14. The wick 16
is held by the tube 14 to engage closely an inner surface of the
casing 12. The casing 12 is typically made of high thermally
conductive materials such as copper or copper alloys. Although the
casing 12 as illustrated is in a round shape, it should be
recognized that other shapes, such as rectangle or the like, may
also be suitable. The wick 16 is a screen mesh wick having a porous
structure and is saturated with a working fluid (not shown), which
acts as a heat carrier for carry thermal energy inside the heat
pipe 10 when undergoing a phase transition from liquid state to
vaporous state. The working fluid is usually selected from liquids
such as water or alcohol and is compatible with the wick 16, the
tube 14 and the casing 12.
[0015] The screen mesh wick 16 is typically made independently of
the casing 12 by weaving together a plurality of flexible wires or
threads such as metal wires or synthetic fibers. Then the wick 16
is rolled and inserted into the casing 12. The tube 14 is capable
of applying a uniform pressing force on the wick 16 in order to
maintain the wick 16 as a whole into close contact with the casing
12, thus providing an effective heat transfer path between the
casing 12 and the working fluid saturated in the wick 16. The tube
14 defines therein a plurality of through holes 142 through its
inner and outer surfaces thereof. These through holes 142 are round
in shape, although other shapes such as rectangle or triangle or
the like may also be suitable. In addition, the through holes 142
may be arranged at the tube 14 regularly or irregularly. The design
of the through holes 142 is to enable a communication of the
working fluid between the wick 16 and a hollow vapor channel (not
labeled) defined in the casing 12 and the tube 14. Specifically,
when the working fluid contained in the wick 16 receives heat from
a heat source in thermal connection with an evaporating section
(not labeled) of the heat pipe 10 and turns into vapor, the vapor
goes into the vapor channel defined by the casing 12 via the
through holes 142 and then moves, through the vapor channel, toward
a condensing section (not labeled) of the heat pipe 10 where the
vapor releases its heat and turns into liquid. Then, the condensed
liquid returns from the vapor channel into the wick 16 again via
the through holes 142. Thereafter, the liquid is drawn back to the
evaporating section of the heat pipe 10 via the wick 16 where it is
available again for evaporation. The through holes 142, preferably,
account for about 70 percents of a total surface area of the tube
14 so as to enable the vapor to go into the vapor channel and the
liquid to return back the wick 16 smoothly. In this situation,
however, the tube 14 is still capable of providing enough support
for the wick 16.
[0016] In order for the heat pipe 10 to be suitable for use in
electronic devices such as notebook computers where the heat pipe
10 is usually required to be in a curved or flattened configuration
due to limited mounting space inside these electronic devices, the
tube 14 defines therein a cutout 144 along a circumferential
direction thereof. The cutout 144 is elongated. The cutout 144
extends through a large portion of a circumferential periphery of
the tube 14, but does not cut the tube 14 into two pieces. Due to
the existence of the cutout 144, the heat pipe 10 is easily to be
bent into a curved configuration from the location where the cutout
144 is located, without the necessity of overcoming the rigidity of
the tube 14 especially if the tube 14 is made of rigid material
such as metals. Although in this embodiment the cutout 144 forms a
right angle with respect to an axis (not labeled) of tube 14, it
should be recognized that in some other circumstances the cutout
144 may also be defined slantwise in the tube 14 and in doing so,
an acute angle is formed between the cutout 144 thus defined and
the axis of the tube 14. It should also be recognized that if the
heat pipe 10 is needed to be bent in more than one location, more
than one cutout 144 may be formed in the tube 14. The tube 14 may
be made of metals such as copper or aluminum, and in order to
reduce the rigidity of the tube 14, organic material such as
polyethylene, polycarbonate, polyamide, or the like may also be
suitable for the tube 14.
[0017] As shown in FIG. 2, in assembly, the wick 16 which is
typically made by weaving technology is firstly wrapped around on
the tube 14. The tube 14 may be manufactured by pressing or forging
or injection molding to form firstly a flat plate with the through
holes 142 formed therein and then rolling the flat plate into the
tube 14. Then, the tube 14, together with the wick 16 wrapped
therearound, is inserted into the casing 12 after the casing 12 is
heated to expand with a required extent. As the casing 12 is cooled
down to its original size, the wick 16 is thereby tightly and
evenly held against the inner surface of the casing 12 under the
support of the tube 14.
[0018] FIG. 3 illustrates a tube 14a according to a second
embodiment of the present invention. Compared with the
above-mentioned first embodiment, the tube 14a is divided into two
separate pieces by an elongated cutout 145 transversely cutting
through the tube 14a.
[0019] FIGS. 4-5 illustrate a tube 14b according to a third
embodiment of the present invention. The tube 14b defines therein a
pair of opposite elongate cutouts 146 along a longitudinal
direction thereof. Each cutout 146 has two sections (not labeled)
extending from opposite ends of the tube 14b till a middle thereof.
The two sections do not communicate with each other. In the
presence of the cutouts 146, this tube 14b is typically suitable
for use in heat pipes that need to be pressed into flattened
configurations.
[0020] According to the above-mentioned embodiments, each of the
tubes is capable of providing a uniform pressing force against the
wick of the heat pipe so as to maintain the wick into intimate
contact with the casing of the heat pipe, thereby establishing an
effective heat transfer path between the casing and the working
fluid saturated in the wick. Meanwhile, with the cutouts in the
tubes presented, the heat pipes incorporating such tubes are easier
to be bent or flattened in order to be applicable in modern
electronic devices having a limited mounting space for a cooling
device.
[0021] It is to be understood, however, that even though numerous
characteristics and advantages of the present invention have been
set forth in the foregoing description, together with details of
the structure and function of the invention, 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.
* * * * *