U.S. patent application number 11/164457 was filed with the patent office on 2006-09-07 for screen mesh wick and method for producing the same.
Invention is credited to Ching-Tai Cheng, Chu-Wan Hong, Chang-Ting Lo, Jung-Yuan Wu.
Application Number | 20060196641 11/164457 |
Document ID | / |
Family ID | 36943017 |
Filed Date | 2006-09-07 |
United States Patent
Application |
20060196641 |
Kind Code |
A1 |
Hong; Chu-Wan ; et
al. |
September 7, 2006 |
SCREEN MESH WICK AND METHOD FOR PRODUCING THE SAME
Abstract
A screen mesh wick (14) and a method of making the same are
disclosed. The wick is made separately and is adaptive for
inserting into a heat pipe as a wick structure. The wick includes a
plurality of elongated wires (141, 142) woven together and a
plurality of protruding portions (145) formed on the wires. The
protruding portions may be small metal powders attached to outer
surfaces of the wires. The method includes the steps of weaving a
plurality of wires to form a mesh (14') firstly and then forming a
plurality of protruding portions on the mesh, for example, by
spreading the metal powders onto the mesh while the mesh is subject
to heating. With these protruding portions formed on the wires, the
effective pore size defined between the wires is reduced and
therefore the wick is capable of providing a larger capillary
pressure.
Inventors: |
Hong; Chu-Wan; (Shenzhen,
CN) ; Cheng; Ching-Tai; (Shenzhen, CN) ; Wu;
Jung-Yuan; (Shenzhen, CN) ; Lo; Chang-Ting;
(Shenzhen, CN) |
Correspondence
Address: |
NORTH AMERICA INTELLECTUAL PROPERTY CORPORATION
P.O. BOX 506
MERRIFIELD
VA
22116
US
|
Family ID: |
36943017 |
Appl. No.: |
11/164457 |
Filed: |
November 23, 2005 |
Current U.S.
Class: |
165/104.26 ;
165/104.33 |
Current CPC
Class: |
F28D 15/046
20130101 |
Class at
Publication: |
165/104.26 ;
165/104.33 |
International
Class: |
F28D 15/04 20060101
F28D015/04 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 28, 2005 |
TW |
094102627 |
Claims
1. A screen mesh wick being made separately and adaptive for
inserting into a heat pipe as a wick structure, the screen mesh
wick comprising a plurality of elongated wires woven together and a
plurality of protruding portions formed on the wires.
2. The wick of claim 1, wherein the protruding portions are small
powders attached to outer surfaces of the wires.
3. The method of claim 2, wherein the wires are flexible and are
constructed from a single material or different materials.
4. The wick of claim 3, wherein the protruding portions are formed
from materials including copper, aluminum, stainless steel and
combinations thereof.
5. The wick of claim 4, wherein the melting points of the wires are
higher than those of the small powders.
6. The wick of claim 3, wherein the wires are formed from materials
including copper, aluminum, stainless steel and combinations
thereof.
7. The wick of claim 2, wherein the small powders have an average
particles size that is substantially one-fifth to one-third of a
diameter or a width of the wires.
8. The wick of claim 1, wherein the wires includes a first wire
having a plate-type configuration and a second wire having a rod
configuration.
9. A method for manufacturing a screen mesh wick for a heat pipe
comprising the steps of: forming a mesh by weaving technology; and
forming a plurality of protruding portions on the mesh.
10. The method of claim 9, wherein the mesh is formed by weaving a
plurality of flexible wires that are constructed from a single
material or different materials.
11. The method of claim 10, wherein the protruding portions are
formed by spreading small powders onto the mesh while the mesh is
heated.
12. The method of claim 11, wherein the melting points of the wires
are higher than those of the small powders.
13. The method of claim 10, wherein the protruding portions formed
on the mesh are small powders, and the small powders are combined
to the mesh by applying the mesh to the small powders after the
mesh is heated.
14. The method of claim 13, wherein the melting points of the wires
are higher than those of the small powders.
15. A screen mesh wick being inserted into a heat pipe for
transmitting heat from one end to another end thereof, comprising:
a mesh made of wires woven together, the mesh defining a plurality
of pores between the wires; and a plurality of protrusions having a
size smaller than that of the wires, secured to the wires and
protruding into the pores prior to insertion into the heat
pipe.
16. The screen mesh wick of claim 15, wherein the protrusions are
made of powders.
17. The screen mesh wick of claim 15, wherein the wires have a
rod-shaped configuration and a flat-plate configuration.
18. The screen mesh wick of claim 16, wherein the powders are made
of a metal of one of copper, aluminum and stainless steel.
19. The screen mesh wick of claim 16, wherein the powders have a
diameter which is about one-fifth to one-third of a diameter of the
wires.
20. The screen mesh wick of claim 15, wherein the protrusions are
secured to outer surfaces of the wires.
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 screen
mesh wick applicable in heat pipes and a method for producing such
wick.
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 the "evaporating section")
to another section thereof (typically referring to as the
"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 brought back by the wick structure to the
evaporating section where it is again available for
evaporation.
[0003] The wick structure currently available for heat pipes
includes fine grooves integrally formed at the inner wall of the
casing, screen mesh or bundles of fiber inserted into the casing
and typically held against the inner wall thereof, or sintered
powder combined to the inner wall of the casing by sintering
process. Among these wicks, the screen mesh wick is preferred to
the other wicks due to its economic advantage in manufacturing. The
manufacture of a screen mesh wick is comparatively simple and
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 then inserted into the
casing of a heat pipe.
[0004] In a heat pipe, the primary function of a wick is to draw
condensed liquid back to the evaporating section of the heat pipe
under the capillary pressure developed by the wick. Therefore,
whether the wick could provide a large capillary pressure is a
major consideration that is used to evaluate the performance of the
wick. A heat pipe with a wick that has too large a pore size
generally cannot provide a large capillary force and therefore
often suffers dry-out problem at the evaporating section as the
condensed liquid cannot be timely sent back to the evaporating
section of the heat pipe. Since it is well recognized that the
capillary pressure of a wick increases due to a decrease in pore
size of the wick, it is thus preferred to have the screen mesh wick
woven in a greater density so as to reduce the pore size formed
between the wires of the wick and accordingly obtain a relatively
large capillary pressure for the wick. However, under current
weaving technology, it is difficult to reduce the pore size of the
screen mesh wick further due to the restriction of the weaving
technology.
[0005] Therefore, it is desirable to provide a method for
manufacturing a screen mesh wick which can further reduce the pore
size of the wick. What is also desirable is to provide a screen
mesh wick made from this method and a heat pipe incorporating such
wick.
SUMMARY OF INVENTION
[0006] The present invention relates in one aspect, to a screen
mesh wick for a heat pipe. The screen mesh wick is made separately
and is adaptive for inserting into a heat pipe as a wick structure.
The screen mesh wick comprises a plurality of elongated wires woven
together and a plurality of protruding portions formed on the
wires. In one preferred embodiment, the protruding portions are
small metal powders attached to outer surfaces of the wires. With
these protruding portions formed on the wires, the effective pore
size defined between the wires is reduced and as a result, the wick
is capable of providing a larger capillary pressure for drawing
liquid condensed at a condensing section of the heat pipe towards
an evaporating section of the heat pipe.
[0007] The present invention relates in another aspect, to a method
for manufacturing a screen mesh wick for a heat pipe, wherein the
method comprises steps of forming a mesh firstly by weaving
technology and then forming a plurality of protruding portions on
the mesh. By using this method, the capillary force that the wick
could develop is increased as a result of a reduce in pore size of
the mesh due to the presence of the protruding portions, even
though the weaving density of the mesh is not increased.
[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 cross-sectional view of a heat pipe having a
screen mesh wick in accordance with one embodiment of the present
invention;
[0010] FIG. 2 is an isometric view of the screen mesh wick of FIG.
1, being in an expanded status;
[0011] FIG. 3 is a top plan view of the screen mesh wick of FIG.
2;
[0012] FIG. 4 is an enlarged view of the circled portion IV of FIG.
3;
[0013] FIG. 5 is a flow chart showing a preferred method for
manufacturing the screen mesh wick of FIG. 2; and
[0014] FIGS. 6-7 are isometric views showing the steps of the
preferred method of FIG. 5 in manufacturing the screen mesh wick of
FIG. 2.
DETAILED DESCRIPTION
[0015] FIG. 1 illustrates a heat pipe 10 in accordance with a
preferred embodiment of the present invention. The heat pipe 10
includes a casing 12 and a screen mesh wick 14 arranged against an
inner wall of the casing 12. The casing 12 is made of high
thermally conductive material such as copper or aluminum. 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 screen mesh wick 14 is a porous structure and
is saturated with a working fluid (not shown), which acts as a heat
carrier when undergoing a phase transition from liquid state to
vaporous state. The working fluid is usually selected from
liquids--such as water or alcohol--that have a low boiling point
and are compatible with the wick 14. In order to maintain the wick
14 to tightly engage the inner wall of the casing 12, retaining
means such as a helical spring (not shown) may be used to hold the
wick 14 against the casing 12.
[0016] The screen mesh wick 14 is typically made separately and
then is rolled and inserted into the heat pipe 10 as a wick
structure. Referring to FIGS. 2-4, the screen mesh wick 14 is
formed by weaving together a plurality of flexible wires or threads
such as metal wires or synthetic fibers. As illustrated in this
embodiment, the wick 14 is constructed by weaving a first wire 141
and a second wire 142 together, wherein the first wire 141 has
plate-type configuration while the second wire 142 has a rod
configuration. The wires 141, 142 have sufficient flexibility so
that they can be woven together easily. Each of the wires 141, 142
has a preferred diameter or width of 45 micrometers (.mu.m), and
may be constructed from a material with excellent thermal
conductivity such as copper, aluminum, or stainless steel. The
wires 141, 142 may be constructed from a single material or
different materials, and also may have identical configurations or
different configurations.
[0017] As shown in FIG. 4, a pore 143 is illustrated as defined
between a pair of adjacent first wires 141 and a pair of adjacent
second wires 142. In order to reduce the size of the pores 143 and
ultimately gain a relatively large capillary pressure for the
screen mesh wick 14, a plurality of micron-sized protruding
portions 145 is combined to outer surfaces of the wires 141, 142.
Some the protruding portions 145 protrude into the pores 143 to
reduce the size thereof. These protruding portions 145 may be small
particles such as metal powders that are attached to the wires 141,
142 after the wires 141, 142 are heated to a temperature near
one-third to two-third of their melting point. These particles may
be such materials as copper, aluminum, stainless steel or
combination thereof, and may have an average particle size that is
about one-fifth to one-third of the diameter or width of the wires
141, 142. Preferably, the melting points of these particles are not
higher than those of the wires 141, 142. More preferably, the
protrusions 145 and the wires 141, 142 are made of the same
metal.
[0018] With reference to FIG. 5, a preferred method 100 for
constructing such wick 14 is shown. The preferred method 100
generally includes two steps, i.e., the first step 101 and the
second step 102. The first step 101 is to form a mesh 14' by
weaving together a plurality of the first and second wires 141,
142, as shown in FIG. 6. The second step 102 is to form a plurality
of the protruding portions 145 on the outer surfaces of the mesh
14' formed by the foregoing first step 101, to thereby obtain the
screen mesh wick 14 as illustrated in FIG. 2. As with the second
step 102, if these protruding portions 145 to be formed on the mesh
14' are small metal powders, a nozzle 20 is typically used to
spread these metal particles onto the mesh 14' while the mesh 14'
is heated, for example, to a temperature substantially equal to
one-third to two-third of the melting point of the mesh 14', thus
combining these particles to the mesh 14' after these particles and
the mesh 14' are cooled. For combining these particles to the mesh
14', some other methods may also be suitable. For example, the
metal particles to be formed as the protruding portions 145 of the
wick 14 may be spread on a flat surface evenly to form a "bed of
powder" in advance, and then the mesh 14', after it is heated, is
applied to the bed of powder, optimally with a downward pressing
force, to thereby adhere the particles to the mesh 14' and form the
screen mesh wick 14.
[0019] In the above-illustrated embodiment, the wick 14 is formed
firstly by weaving technology and is then processed to further
reduce the effective pore size thereof by means of forming a
plurality of the protruding portions 145 thereon. The wick 14 is
thus capable of providing a larger capillary force than the mesh
without the protruding portions thereon, thereby effectively
solving the dry-out problem as experienced by the prior art.
[0020] 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.
* * * * *