U.S. patent application number 11/164093 was filed with the patent office on 2006-07-27 for heat pipe with screen mesh wick structure.
Invention is credited to Ching-Tai Cheng, Chu-Wan Hong, Chang-Ting Lo, Jung-Yuan Wu.
Application Number | 20060162906 11/164093 |
Document ID | / |
Family ID | 36695488 |
Filed Date | 2006-07-27 |
United States Patent
Application |
20060162906 |
Kind Code |
A1 |
Hong; Chu-Wan ; et
al. |
July 27, 2006 |
HEAT PIPE WITH SCREEN MESH WICK STRUCTURE
Abstract
A heat pipe (10) includes a pipe body (20) having an inner wall
(22) and a screen mesh (30) disposed on the inner wall of the pipe
body. The screen mesh is in the form of a multi-layer structure
with at least one layer thereof having an average pore size
different from that of the other layers. The layer with large-sized
pores is capable of reducing the flow resistance to the condensed
fluid to flow back, whereas the layer with small-size pores is
capable of providing a relatively large capillary pressure for
drawing the condensed fluid from the condensing section to the
evaporating section.
Inventors: |
Hong; Chu-Wan; (Shenzhen,
CN) ; Wu; Jung-Yuan; (Shenzhen, CN) ; Cheng;
Ching-Tai; (Shenzhen, CN) ; Lo; Chang-Ting;
(Shenzhen, CN) |
Correspondence
Address: |
NORTH AMERICA INTELLECTUAL PROPERTY CORPORATION
P.O. BOX 506
MERRIFIELD
VA
22116
US
|
Family ID: |
36695488 |
Appl. No.: |
11/164093 |
Filed: |
November 10, 2005 |
Current U.S.
Class: |
165/104.26 ;
165/146 |
Current CPC
Class: |
F28D 15/046
20130101 |
Class at
Publication: |
165/104.26 ;
165/146 |
International
Class: |
F28D 15/02 20060101
F28D015/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 21, 2005 |
TW |
094101782 |
Mar 18, 2005 |
TW |
094108396 |
Claims
1. A heat pipe comprising: a pipe body having an inner wall; and a
screen mesh disposed on the inner wall of the pipe body; wherein
the screen mesh comprises several layers, at least one of the
several layers has an average pore size different from that of the
other layers.
2. The heat pipe of claim 1, wherein each layer of the several
layers has an average pore size different from that of a
neighboring layer thereof.
3. The heat pipe of claim 1, wherein the several layers are stacked
together along a radial direction of the pipe body.
4. The heat pipe of claim 3, wherein the several layers are stacked
in such a manner that the average pore sizes thereof increase along
the radial direction of the pipe body.
5. The heat pipe of claim 3, wherein the several layers comprise
three layers, two layers of the three layers disposed at respective
opposite sides of the other layer have the same average pore size,
the other layer located between the two layers have an average pore
size different from that of the two layers.
6. The heat pipe of claim 3, wherein at least one of the several
layers comprises several sections along a longitudinal direction of
the pipe body.
7. The heat pipe of claim 6, wherein the heat pipe is divided into
an evaporating section, a condensing section, and an adiabatic
section along a longitudinal direction of the pipe body, the
several sections of at least one of the several layers locate
corresponding to the three sections of the heat pipe,
respectively.
8. The heat pipe of claim 7, wherein each layer comprises three
sections corresponding to the three sections of the heat pipe
respectively.
9. The heat pipe of claim 6, wherein one of the sections of the at
least one layer has an average pore size different from that of a
neighboring section of the at least one layer.
10. The heat pipe of claim 6, wherein each section of the at least
one layer has an average pore size different from the other
sections of the at least one layer.
11. The heat pipe of claim 3, wherein along the radial direction of
the heat pipe, at least one of the several layers has a thickness
different from that of the other layers.
12. The heat pipe of claim 1, wherein the several layers are
arranged side by side along a longitudinal direction of the pipe
body.
13. The heat pipe of claim 12, wherein the several layers are
arranged in such a manner that the average pore sizes thereof
increase along the longitudinal direction of the pipe body.
14. The heat pipe of claim 13, wherein the heat pipe is divided
into an evaporating section and a condensing section at respective
opposite ends thereof, and a heat insulating section located
between the evaporating section and the condensing section, the
several layers comprises three layers at the three sections of the
heat pipe, respectively.
15. The heat pipe of claim 14, wherein the three layers of the
screen mesh are arranged in such a manner that the average pore
sizes thereof decrease from the evaporating section to the
condensing section of the heat pipe.
16. The heat pipe of claim 12, wherein along the longitudinal
direction of the heat pipe, at least one of the layers has a
thickness different from that of the other layers.
17. A heat pipe comprising: a pipe body having an inner wall and
defining an evaporating section and a condensing section; working
fluid received in the pipe body; a mesh screen attached on the
inner wall of the pipe body for drawing the working fluid in a
condensed state from the condensing section to the evaporating
section, the mesh screen including different layers arranged along
one of longitudinal direction and radial direction of the pipe
body, pores in the different layers having different pore
sizes.
18. The heat pipe of claim 17, wherein the pore sizes decrease
along a direction from a center of the pipe body toward the inner
wall of the pipe body.
19. The heat pipe of claim 17, wherein the pore sizes increase
along a direction from the evaporating section toward the
condensing section.
20. The heat pipe of claim 17, wherein the different layers are
arranged side by side when the different layers are arranged along
the longitudinal direction of the pipe body.
Description
FIELD OF THE INVENTION
[0001] The present invention relates generally to a heat pipe as a
heat transfer device, and more particularly to a heat pipe with a
screen mesh wick structure.
DESCRIPTION OF RELATED ART
[0002] As electronic industry continues to advance, electronic
components such as central processing units (CPUs), are made to
provide faster operation speeds and greater functional
capabilities. When a CPU operates at a high speed, its temperature
frequently increases greatly. It is desirable to dissipate the heat
generated by the CPU quickly.
[0003] To solve this problem of heat generated by the CPU, a
cooling device is often used to be mounted on top of the CPU to
dissipate heat generated thereby. It is well known that heat
absorbed by fluid having a phase change is ten times more than that
the fluid does not have a phase change; thus, the heat transfer
efficiency by phase change of fluid is better than other
mechanisms, such as heat conduction or heat convection. Thus a heat
pipe has been developed.
[0004] The heat pipe has a hollow pipe body receiving a working
fluid therein and a wick structure disposed on an inner wall of the
pipe body. During operation of the heat pipe, the working fluid
absorbs the heat generated by the CPU or other electronic device
and evaporates. Then the vapor moves to the condensing section to
release the heat thereof. The vapor cools and condenses at the
condensing section. The condensed working fluid returns to the
evaporating section and evaporates into vapor again, whereby the
heat is continuously transferred from the evaporating section to
the condensing section.
[0005] In general, movement of the working fluid depends on
capillary pressure of the wick structure. Usually the wick
structure has following four configurations: sintered power,
grooved, fiber and screen mesh. For the thickness and pore size of
the screen mesh can be easily changed, the screen mesh is widely
used in the heat pipe.
[0006] It is well recognized that the capillary pressure of a
screen mesh increases due to a decrease in pore size of the screen
mesh. In order to obtain a relatively large capillary pressure for
a screen mesh, a mesh screen having a small-sized pores is usually
adopted. However, it is not always the best way to choose a screen
mesh having small-sized pores, because the flow resistance to the
condensed working fluid also increases due to the decrease in pore
size of the screen mesh. The increased flow resistance reduces the
speed of the condensed working fluid in returning back to the
evaporating section and therefore limits the heat transfer
performance of the heat pipe. As a result, a heat pipe with a
screen mesh that has too large or too small pore size often suffers
dry-out problem at the evaporating section as the condensed fluid
cannot be timely return back to the evaporating section of the heat
pipe.
[0007] Therefore, there is a need for a heat pipe with a screen
mesh which can provide simultaneously a relatively large capillary
pressure and a relatively low flow resistance so as to effectively
and timely bring the condensed fluid back from its condensing
section to its evaporating section and thereby to avoid the
undesirable dry-out problem at the evaporating section. There is
also a need for a heat pipe with a screen mesh which has a range of
pore sizes so that the heat pipe can operate under different
conditions without the undesirable dry-out problem at the
evaporating section.
SUMMARY OF INVENTION
[0008] A heat pipe in accordance with a preferred embodiment of the
present invention comprises a pipe body having an inner wall and a
screen mesh disposed on the inner wall of the pipe body. The screen
mesh is in the form of a multi-layer structure with at least one
layer thereof has an average pore size different from that of the
other layers. The layer with large-sized pores is capable of
reducing the flow resistance to the condensed fluid to flow back,
whereas the layer with small-sized pores is still capable of
providing a relatively large capillary pressure for the condensed
fluid in the heat pipe.
[0009] 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
[0010] FIG. 1 is a longitudinal cross-sectional view of a heat pipe
in accordance with a first embodiment of the present invention;
[0011] FIG. 2 is a view similar to FIG. 1, showing a heat pipe
according to a second embodiment of the present invention;
[0012] FIG. 3 is a longitudinal cross-sectional view of a heat pipe
in accordance with a third embodiment of the present invention;
[0013] FIG. 4 is a longitudinal cross-sectional view of a heat pipe
in accordance with a fourth embodiment of the present
invention;
[0014] FIG. 5 is a longitudinal cross-sectional view of a heat pipe
in accordance with a fifth embodiment of the present invention;
[0015] FIG. 6 is a longitudinal cross-sectional view of a heat pipe
in accordance with a sixth embodiment of the present invention;
[0016] FIG. 7 is a longitudinal cross-sectional view of a heat pipe
in accordance with a seventh embodiment of the present
invention;
[0017] FIG. 8 is a longitudinal cross-sectional view of a heat pipe
in accordance with an eighth embodiment of the present
invention;
[0018] FIG. 9 is a longitudinal cross-sectional view of a heat pipe
in accordance with a ninth embodiment of the present invention;
and
[0019] FIG. 10 is a longitudinal cross-sectional view of a heat
pipe in accordance with a tenth embodiment of the present
invention;
DETAILED DESCRIPTION
[0020] FIG. 1 illustrates a heat pipe 10 in accordance with a first
embodiment of the present invention. The heat pipe 10 comprises a
pipe body 20 and a screen mesh 30 disposed on an inner wall 22 of
the pipe body 20. The heat pipe 10 comprises an evaporating section
70 and a condensing section 90 at respective opposite ends thereof,
and an adiabatic section 80 located between the evaporating section
70 and the condensing section 90.
[0021] The pipe body 20 is typically made of high thermally
conductive materials such as copper or copper alloys. The screen
mesh 30 is saturated with a working fluid (not shown), which acts
as a heat carrier for carry thermal energy from the evaporating
section 70 toward the condensing section 90 when undergoing phase
change from a fluid state to a vaporous state. The working fluid
may be water, alcohol or other material having a low boiling point
and the heat pipe 10 is vacuumed; thus, the working fluid can
easily evaporate to vapor during operation.
[0022] Along a longitudinal direction of the pipe body 20 from the
evaporating section 70 to the condensing section 90, the screen
mesh 30 has a multi-layer structure, which includes in sequence a
first layer 40, a second layer 50 and a third layer 60. In this
embodiment, the first, second and third layer 40, 50, 60 correspond
to the evaporating, adiabatic and condensing section 70, 80, 90 of
the heat pipe 10, respectively. Each layer of the screen mesh 30
has an average pore size different from that of the other layers.
The first layer 40 has the smallest average pore size, whereas the
third layer 60 has the largest average pore size. That is, the
three layers 40, 50, 60 are arranged side by side in such a manner
that the average pore sizes thereof gradually increase along the
longitudinal direction from the evaporating section 70 toward the
condensing section 90. According to the general rule, the capillary
pressure of the screen mesh 30 and its flow resistance to the
condensed fluid increase due to a decrease in pore size of the
screen mesh 30; the multi-layer construction of the screen mesh 30
is thus capable of providing a capillary pressure gradually
increasing from the condensing section 90 toward the evaporating
section 70, and a flow resistance gradually decreasing from the
evaporating section 70 toward the condensing section 90.
[0023] FIG. 2 shows a heat pipe 210 according to a second
embodiment of the present invention. The heat pipe 210 includes a
pipe body 20 and a screen mesh 230 in the form of a three-layer
structure arranged in the pipe body 20. The difference between the
second embodiment and the first embodiment is that the three layers
240, 250, 260 of this second embodiment are arranged together side
by side in such a manner that the average pore sizes thereof
gradually decrease along the longitudinal direction from the
evaporating section 270 toward the condensing section 290. The
first layer 240 corresponding to the evaporating section 270 of the
heat pipe 210 has the largest average pore size, whereas the third
layer 260 corresponding to the condensing section 290 of the heat
pipe 210 has the smallest average pore size. The second layer 250
corresponding to the adiabatic section 280 of the heat pipe 210 has
an average pore size larger than that of the first layer 240 and
smaller than that of the third layer 260.
[0024] FIG. 3 shows a third embodiment of the heat pipe 310.
Similar to the first embodiment, the heat pipe 310 also comprises a
pipe body 20 and a screen mesh 330 in the form of a three-layer
structure disposed in the pipe body 20. The difference of the third
embodiment over the first embodiment is that the first and third
layer 340, 360 of the this embodiment which are corresponding to
the evaporating and condensing section 370, 390 of the heat pipe
310 have the same average pore size. The second layer 350
corresponding to the adiabatic section 380 has an average pore size
different from that of the two layers 340, 360.
[0025] FIG. 4 illustrates a heat pipe 410 according to a fourth
embodiment of the present invention. The heat pipe 410 includes a
pipe body 20 and a screen mesh 430 arranged in the pipe body 20.
The screen mesh 430 is in the form of a multi-layer structure,
which comprises an outer layer 440, an intermediate layer 450 and
an inner layer 460. These layers 440, 450, 460 are stacked together
along a radial direction of the pipe body 20 with the outer layer
440 abutting the inner wall 22 of the pipe body 20. Each layer of
the screen mesh 430 has an average pore size different from that of
the other layers, and these layers 440, 450, 460 are stacked
together in such a manner that the average pore sizes thereof
gradually increase along the radial direction from the inner wall
22 of the pipe body 20 towards a central axis X-X of the pipe body
20.
[0026] According to the above-mentioned general rule, the capillary
pressure of a wick and its flow resistance to the condensed fluid
increase due to a decrease in pore size of the wick; the inner
layer 460 and the intermediate layer 450 have a relatively larger
average pore size and therefore are capable of providing a
relatively low resistance to the condensed working fluid to flow
back. The outer layer 440, however, has a relatively smaller
average pore size and therefore is capable of having a relatively
high capillary pressure for drawing the condensed working fluid
back to the evaporating section. Thus, the multi-layer construction
of the screen mesh 430 is capable of providing between these
layers, along the radial direction of the pipe body 20 a gradient
of capillary pressure gradually increasing from the central axis
X-X of the pipe body 20 toward the inner surface of the pipe body
20, and a gradient of flow resistance gradually decreasing from the
inner surface of the pipe body 20 toward a central axis X-X of the
pipe body 20. Furthermore, the outer layer 440 with small-sized
pores is also capable of maintaining an increased contact surface
area with the inner surface of the pipe body 20, as well as a large
contact surface with the working fluid saturated in the screen mesh
430, to thereby facilitate heat transfer between the working fluid
in the heat pipe 410 and a heat source outside the heat pipe 410
that needs to be cooled.
[0027] FIG. 5 illustrates a heat pipe 510 according to a fifth
embodiment of the present invention. Similar to the fourth
embodiment, the heat pipe 510 also has a multi-layer pore-based
capillary screen mesh 530 arranged at an inner wall 22 of the heat
pipe 510. The screen mesh 530 includes an outer layer 540, an
intermediate layer 550 and an inner layer 560, which are stacked
together along a radial direction of the heat pipe 510 with the
outer layer 540 being connected to the inner wall 22 of the heat
pipe 510. These layers 540, 550, 560 have different pore sizes to
each other. Conversely from the previous embodiment, these layers
540, 550, 560 are arranged in such an order that the pore sizes
thereof gradually decrease from the inner wall 22 of the heat pipe
510 towards a central axis Y-Y of the heat pipe 510. Therefore, the
large-sized outer layer 540 has a relatively large pore size and
accordingly develops a relatively low resistance to the condensed
fluid to return back. However, this construction of the screen mesh
530 is suitable for a heat pipe with a relatively short length.
[0028] Also the layers can be arranged variably according to the
heat flux of the heat source. As shown in FIG. 6, the screen mesh
630 of the heat pipe 610 comprises three layers 640, 650 660
arranged along a radial direction of the pipe body 20. The outer
and inner layer 640, 660 arranged at respective opposite sides of
the intermediate layer 650 have the same average pore size, the
intermediate layer 650 located between the two layers 640, 660 have
an average pore size larger than that of the other two layers 640,
660.
[0029] FIG. 7 illustrates a heat pipe 710 according to a seventh
embodiment of the present invention. The heat pipe 710 comprises a
screen mesh 730 having the outer, intermediate and inner layer 740,
750, 760 arranged along a radial direction of the pipe body 20.
Each layer comprises three sections arranged along the longitudinal
of the heat pipe 710. The outer layer 740 is divided into a first
section 67, a second section 68 and a third section 69
corresponding to the evaporating, adiabatic and condensing section
770, 780, 790 of the heat pipe 710, respectively. Similar to the
outer layer 740, the inner layer 760 comprises a first, second and
third section 47, 48, 49, and the intermediate layer 750 comprises
a first, second and third section 57, 58, 59. Each section of a
specific layer has an average pore size different from that of the
other sections of the specific layer. Thus the screen mesh 730 is
in the form of multi-layer structure either along the longitudinal
direction or along the radial direction of the pipe body 20. As a
result, the screen mesh 730 can provide a variable capillary
pressure and flow resistance along either the longitudinal or the
radial direction of the heat pipe 710.
[0030] FIG. 8 illustrates an eighth embodiment of the heat pipe
810. Similar to the seventh embodiment, the screen mesh 830 of the
heat pipe 810 comprises three layers 840, 850, 860 arranged along a
radial direction of the heat pipe 810. The difference of this
embodiment over the previous embodiment is that only the
intermediate layer 850 comprising three sections along a
longitudinal direction of the heat pipe 810. The outer and inner
layer 840, 860 has the same average pore size throughout all the
three sections of the heat pipe 810, i.e., the evaporating,
adiabatic and condensing sections.
[0031] Each layer or section of the screen mesh as shown above has
the same length or thickness along the longitudinal or the radial
direction of the heat pipe 10. It is to be understood that the
thickness or length of each layer or section can be changed and
different from the others. As shown in FIG. 9, the inner layer 960
of the screen mesh 930 has the smallest thickness, whereas the
intermediate layer 950 has the largest thickness along a radial
direction of the heat pipe 910. The layer 940 is the outer layer of
the screen mesh 930. Another embodiment of the heat pipe 110 as
shown in FIG. 10 illustrates a screen mesh 130 comprises three
layer arranged in the pipe body (not labeled) along a radial
direction of the pipe body. Each layer divided into three sections
along a longitudinal direction. The sections arranged corresponding
to the evaporating section 170 and the condensing section 190 of
the heat pipe 110 have a larger length along the longitudinal
direction of the heat pipe 110 than the section corresponding to
the adiabatic section 180 thereof.
[0032] It is understood that the invention may be embodied in other
forms without departing from the spirit thereof. Thus, the present
example and embodiment is to be considered in all respects as
illustrative and not restrictive, and the invention is not to be
limited to the details given herein.
* * * * *