U.S. patent application number 12/491245 was filed with the patent office on 2010-06-24 for heat pipe and method of making the same.
This patent application is currently assigned to FURUI PRECISE COMPONENT (KUNSHAN) CO., LTD.. Invention is credited to NIEN-TIEN CHENG, SHENG-LIANG DAI, YU-LIANG LO, SHENG-LIN WU.
Application Number | 20100155031 12/491245 |
Document ID | / |
Family ID | 41593795 |
Filed Date | 2010-06-24 |
United States Patent
Application |
20100155031 |
Kind Code |
A1 |
WU; SHENG-LIN ; et
al. |
June 24, 2010 |
HEAT PIPE AND METHOD OF MAKING THE SAME
Abstract
A heat pipe includes a casing, a main wick structure received in
the casing and attached to an inner surface of the casing, a
multi-layered auxiliary wick structure received in the main wick
structure and a working fluid contained in the casing and
saturating the main wick structure and the auxiliary wick
structure. An inner peripheral surface of the main wick structure
and an outer peripheral surface of the auxiliary wick structure
cooperatively define a vapor channel therebetween. The auxiliary
wick structure extends along a longitudinal direction of the casing
and defines a liquid channel therein. The auxiliary wick structure
is formed by a plurality of layers radially stacked on each other,
such that each outer layer is attached around an adjacent inner
layer.
Inventors: |
WU; SHENG-LIN; (Tu-Cheng,
TW) ; LO; YU-LIANG; (Tu-Cheng, TW) ; DAI;
SHENG-LIANG; (ShenZhen City, CN) ; CHENG;
NIEN-TIEN; (Tu-Cheng, TW) |
Correspondence
Address: |
PCE INDUSTRY, INC.;ATT. Steven Reiss
288 SOUTH MAYO AVENUE
CITY OF INDUSTRY
CA
91789
US
|
Assignee: |
FURUI PRECISE COMPONENT (KUNSHAN)
CO., LTD.
KunShan
CN
FOXCONN TECHNOLOGY CO., LTD.
Tu-Cheng
TW
|
Family ID: |
41593795 |
Appl. No.: |
12/491245 |
Filed: |
June 25, 2009 |
Current U.S.
Class: |
165/104.26 ;
29/890.032 |
Current CPC
Class: |
F28D 15/046 20130101;
Y10T 29/49353 20150115; F28D 15/0233 20130101 |
Class at
Publication: |
165/104.26 ;
29/890.032 |
International
Class: |
F28D 15/04 20060101
F28D015/04; B21D 53/06 20060101 B21D053/06 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 22, 2008 |
CN |
200810306425.X |
Claims
1. A heat pipe comprising: a casing; a main wick structure received
in the casing and attached to an inner surface of the casing; a
multi-layered auxiliary wick structure received in the main wick
structure, an inner peripheral surface of the main wick structure
and an outer peripheral surface of the auxiliary wick structure
cooperatively defining a vapor channel therebetween, the auxiliary
wick structure extending along a longitudinal direction of the
casing and defining a liquid channel therein; and a working fluid
contained in the casing and saturated in the main wick structure
and the auxiliary wick structure; wherein the auxiliary wick
structure is formed by a plurality of layers radially disposed on
each other in which each outer layer is attached immediately around
an adjacent inner layer.
2. The heat pipe as claimed in claim 1, wherein the auxiliary wick
structure comprises a first inner layer and a second outer layer
attached around the first layer, an inner surface of the first
inner layer defining the liquid channel, the inner surface of the
main wick structure and an outer peripheral surface of the
auxiliary wick structure defining the vapor channel.
3. The heat pipe as claimed in claim 1, wherein each layer of the
auxiliary wick structure is formed by weaving a plurality of
wires.
4. The heat pipe as claimed in claim 3, wherein the wires of an
inner layer have a greater wire diameter than that of the wires of
an adjacent outer layer of the auxiliary wick structure.
5. The heat pipe as claimed in claim 1, wherein an outer diameter
of the auxiliary wick structure is smaller than a bore diameter of
the main wick structure.
6. The heat pipe as claimed in claim 1, wherein the casing is
round.
7. The heat pipe as claimed in claim 1, wherein the casing is
flattened.
8. A method for manufacturing a heat pipe comprising the steps of:
providing an elongated pole, weaving a plurality of first wires on
an outer peripheral surface of the pole to form a first layer;
weaving a plurality of second wires on an outer peripheral surface
of the first layer to form a second layer; removing the pole from
the first layer to form an auxiliary wick structure, the auxiliary
wick structure defining a liquid channel therein; providing a
casing having a main wick structure, the main wick structure
attached to an inner surface of the casing, inserting the auxiliary
wick structure into the casing; vacuuming the casing and filling a
working fluid into the casing; and sealing the casing.
9. The method as claimed in claim 8, wherein the plurality of first
wires of the first layer has a greater wire diameter than that of
the plurality of second wires of the second layer.
Description
BACKGROUND
[0001] 1. Technical Field
[0002] The present invention relates generally to an apparatus for
transfer or dissipation of heat from heat-generating components,
and more particularly to a heat pipe applicable in electronic
products such as personal computers for removing heat from
electronic components installed therein and a method for
manufacturing the same.
[0003] 2. Description of Related Art
[0004] Heat pipes have excellent heat transfer performance due to
their low thermal resistance, and are therefore 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
medium, 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 "evaporator section")
to another section thereof (typically referring to as the
"condenser section"). Preferably, a wick structure is provided
inside the heat pipe, lining an inner wall of the casing, for
drawing the working medium back to the evaporator section after it
is condensed at the condenser section. The wick structure currently
available for the heat pipe includes fine grooves integrally formed
at the inner wall of the casing, screen mesh or fiber inserted into
the casing and held against the inner wall thereof, or sintered
powders combined to the inner wall of the casing by sintering
process.
[0005] In operation, the evaporator section of the heat pipe is
maintained in thermal contact with a heat-generating component. The
working medium contained at the evaporator 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 and thus
carries the heat towards the condenser section where the vapor is
condensed into condensate after releasing the heat into ambient
environment by, for example, fins thermally contacting the
condenser section. Due to the difference in capillary pressure
which develops in the wick structure between the two sections, the
condensate is then brought back by the wick structure to the
evaporator section where it is again available for evaporation.
[0006] In order to draw the condensate back timely, the wick
structure provided in the heat pipe is expected to provide a high
capillary force and meanwhile generate a low flow resistance for
the condensate. In ordinary use, the heat pipe needs to be
flattened to enable the miniaturization of electronic products,
which results in the wick structure of the heat pipe being damaged.
Therefore, the flow resistance of the wick structure is increased
and the capillary force provided by the wick structure is
decreased, which reduces the heat transfer capability of the heat
pipe. If the condensate is not quickly brought back from the
condenser section, the heat pipe will suffer a dry-out problem at
the evaporator section.
[0007] Therefore, it is desirable to provide a heat pipe with an
improved heat transfer capability, whose wick structure will not be
damaged when the heat pipe is flattened.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] Many aspects of the present embodiments can be better
understood with reference to the following drawings. The components
in the drawings are not necessarily drawn to scale, the emphasis
instead being placed upon clearly illustrating the principles of
the present embodiments. Moreover, in the drawings, like reference
numerals designate corresponding parts throughout the several
views.
[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 a transverse cross-sectional view of the heat pipe
of FIG. 1.
[0011] FIG. 3 is a flow chart showing a method for manufacturing
the heat pipe of FIG. 1.
[0012] FIG. 4 is a transverse cross-sectional view of a heat pipe
in accordance with a second embodiment of the present
invention.
DETAILED DESCRIPTION
[0013] Referring to FIGS. 1 and 2, a heat pipe 10 includes an
elongated, round casing 12 containing a working fluid therein, a
main wick structure 14 and an auxiliary wick structure 18.
[0014] The casing 12 is made of a highly thermally conductive
material such as copper or aluminum. The casing 12 includes an
evaporator section 121, an opposing condenser section 122, and an
adiabatic section 123 disposed between the evaporator section 121
and the condenser section 122.
[0015] The main wick structure 14 is tube-shaped in profile, which
is evenly distributed around and attached to an inner surface of
the casing 12. The main wick structure 14 defines a receiving space
therein. The main wick structure 14 extends along a longitudinal
direction of the casing 12. The main wick structure 14 is usually
selected from a porous structure such as fine grooves, sintered
powder, screen mesh, or bundles of fiber, and provides a capillary
force to drive condensed working fluid at the condenser section 122
to flow towards the evaporator section 121 of the heat pipe 10.
[0016] The auxiliary wick structure 18 is a longitudinal hollow
tube, which is received in the receiving space of the main wick
structure 14 and extends along the longitudinal direction of the
casing 12. The auxiliary wick structure 18 has a ring-like
transverse cross section. The auxiliary wick structure 18
longitudinally defines a liquid channel 172 therein. An outer
diameter of the auxiliary wick structure 18 is much smaller than a
bore diameter of the main wick structure 14.
[0017] The auxiliary wick structure 18 is a multi-layered
structure, which is outwardly and radially formed by a plurality of
round layers such that each successive layer is attached to a
previous layer. In the embodiment, the auxiliary wick structure 18
includes a first layer 181 at an inner side and a second layer 182
at an outer side and attached immediately around the first layer
181. An inner peripheral surface of the first layer 181
longitudinally defines the liquid channel 172 therein. An inner
peripheral surface of the main wick structure 14 and an outer
peripheral surface of the second layer 182 of the auxiliary wick
structure 18 cooperatively define a vapor channel 171 in the casing
12. The outer peripheral surface of the auxiliary wick structure 18
has a bottom side 164 contacting with the inner peripheral surface
of the main wick structure 14, and a top side 165 spaced from the
inner peripheral surface of the main wick structure 14.
[0018] The first and the second layers 181, 182 are formed by
weaving a plurality of metal wires, such as copper wires. A
plurality of pores is formed in the first and the second layer 181,
182, which provides a capillary action to the working fluid. The
metal wires of the first layer 181 has a greater wire diameter than
that of the metal wires of the second layer 182, whereby the metal
wires of the first layer 181 have a greater mechanical strength to
support the whole auxiliary wick structure 18, which prevents the
auxiliary wick structure 18 from collapsing down to thereby
maintain the intended shape of the pores and the liquid channel
172. Moreover, since the metal wires of the second layer 182 have a
smaller wire diameter than the metal wires of the first layer 181,
the second layer 182 has a smaller pore size than the first layer
181, whereby the second layer 182 has a greater capillary action to
absorb more working fluid.
[0019] The working fluid is saturated in the main and the auxiliary
wick structures 14, 18 and is usually selected from a liquid such
as water, methanol, or alcohol, which has a low boiling point and
is compatible with the main and the auxiliary wick structures 14,
18. Thus, the working fluid can easily evaporate to vapor when it
receives heat at the evaporator section 121 of the heat pipe
10.
[0020] In operation, the evaporator section 121 of the heat pipe 10
is placed in thermal contact with a heat source, for example, a
central processing unit (CPU) of a computer, which needs to be
cooled. The working fluid contained in the evaporator section 121
of the heat pipe 10 is vaporized into vapor upon receiving the heat
generated by the heat source. Then, the generated vapor moves via
the vapor channel 171 towards the condenser section 122 of the heat
pipe 10. After the vapor releases the heat carried thereby and is
condensed into the condensate in the condenser section 122, the
condensate is brought back by the main wick structure 14 and the
auxiliary wick structure 18 to the evaporator section 121 of the
heat pipe 10 for being available again for evaporation.
[0021] Referring to FIG. 3, a method for manufacturing the heat
pipe 10 includes the following steps: providing an elongated pole,
and weaving a plurality of first metal wires on an outer peripheral
surface of the pole to form the first layer 181; weaving a
plurality of second metal wires on an outer peripheral surface of
the first layer 181 to form a second layer 182; removing the pole
from the first layer 181 to form the auxiliary wick structure 18,
wherein the first layer 181 defines the liquid channel 172 therein;
providing a casing 12 having a main wick structure 14 attached to
an inner peripheral surface thereof, inserting the auxiliary wick
structure 18 into the casing 12; vacuuming an interior of the
casing 12 and filling the working fluid into the casing 12; and
sealing the casing 12.
[0022] Table 1 below shows an average of maximum heat transfer
rates (Qmax) and an average of heat resistances (Rth) of forty-five
conventional round grooved heat pipes and forty-five round heat
pipes 10 formed in accordance with the present disclosure. Qmax
represents the maximum heat transfer rate of the heat pipe at an
operational temperature of 50.degree. C. Rth is obtained by
dividing the margin between an average temperature of the
evaporator section 121 and an average temperature of the condenser
section 122 of the heat pipe 10 by Qmax. A diameter of the
transverse cross section and a longitudinal length of each of the
conventional grooved heat pipes are 6 mm and 160 mm, which are
respectively equal to the transverse diameter and the longitudinal
length of each of the present heat pipes 10. Table 1 shows that the
heat resistance of the present round heat pipe 10 is significantly
less than that of the conventional round grooved heat pipe, whilst
the Qmax of the round heat pipe 10 in accordance with the present
disclosure is significantly more than that of the conventional
round grooved heat pipe.
TABLE-US-00001 TABLE 1 average of Qmax average of Rth Types of heat
pipes (unit: w) (unit: .degree. C./w) Conventional grooved 65 0.025
heat pipes present heat pipes 95.5 0.024
[0023] As shown in FIG. 4, a flat heat pipe 50 in accordance with a
second embodiment of the present invention is obtained by
flattening the heat pipe 10 of FIGS. 1 and 2. The heat pipe 50 has
the same structure as the heat pipe 10 except that the heat pipe 50
is a flat one. After the flattening operation, the auxiliary wick
structure 18 is kept intact, and the auxiliary wick structure 18
spaces a gap from a top wall 52 of the heat pipe 50. The heat
transfer capability of the flat heat pipe 50 is not decreased due
to the flattening operation. The heat transfer capability of the
flat heat pipe 50 is better than a conventional flat heat pipe
whose wick structure is damaged in the flattening operation.
[0024] Table 2 below shows an average of maximum heat transfer
rates (Qmax) and an average of heat resistances (Rth) of ten
conventional flat grooved heat pipes and ten present heat pipes 50,
which are flattened to have a height of 3.5 mm. Before these heat
pipes are flattened, they have the same transverse diameter and
longitudinal length as the heat pipes mentioned in Table 1. Qmax
and Rth in Table 2 have the same meaning as the Qmax and Rth in
Table 1. Table 2 shows that the heat resistance of the present flat
heat pipe 50 is significantly less than that of the conventional
flat grooved heat pipes, whilst the Qmax of the flat present heat
pipes 50 is significantly more than that of the conventional flat
grooved heat pipes.
TABLE-US-00002 TABLE 2 average of Qmax average of Rth Types of heat
pipes (unit: w) (unit: .degree. C./w) Conventional grooved 32 0.055
heat pipes Present heat pipes 64 0.033
[0025] It is believed that the present embodiments and their
advantages will be understood from the foregoing description, and
it will be apparent that various changes may be made thereto
without departing from the spirit and scope of the invention or
sacrificing all of its material advantages, the examples
hereinbefore described merely being preferred or exemplary
embodiments of the invention.
* * * * *