U.S. patent application number 12/817203 was filed with the patent office on 2011-07-21 for flat heat pipe and method for manufacturing the same.
This patent application is currently assigned to FURUI PRECISE COMPONENT (KUNSHAN) CO., LTD.. Invention is credited to SHENG-LIANG DAI, JIN-PENG LIU, YUE LIU, YU-LIANG LO, SHENG-LIN WU, SHENG-GUO ZHOU.
Application Number | 20110174464 12/817203 |
Document ID | / |
Family ID | 43226262 |
Filed Date | 2011-07-21 |
United States Patent
Application |
20110174464 |
Kind Code |
A1 |
LIU; YUE ; et al. |
July 21, 2011 |
FLAT HEAT PIPE AND METHOD FOR MANUFACTURING THE SAME
Abstract
An exemplary flat heat pipe with an evaporator section and a
condenser section at opposite ends thereof includes a hollow flat
casing, a first wick structure and a solid and sintered second wick
structure. The first wick structure includes a top plate and a
bottom plate opposite to the top plate. The first wick structure is
received in the casing, and extends from the evaporator section to
the condenser section. The second wick structure is disposed in the
casing at the evaporator section. The second wick structure
contacts the top and bottom plates and joins the first wick
structure. A method for manufacturing the heat pipe is also
provided.
Inventors: |
LIU; YUE; (KunShan City,
CN) ; DAI; SHENG-LIANG; (KunShan City, CN) ;
LIU; JIN-PENG; (KunShan City, CN) ; ZHOU;
SHENG-GUO; (KunShan City, CN) ; WU; SHENG-LIN;
(Tu-Cheng, TW) ; LO; YU-LIANG; (Tu-Cheng,
TW) |
Assignee: |
FURUI PRECISE COMPONENT (KUNSHAN)
CO., LTD.
KunShan City
CN
FOXCONN TECHNOLOGY CO., LTD.
Tu-Cheng
TW
|
Family ID: |
43226262 |
Appl. No.: |
12/817203 |
Filed: |
June 17, 2010 |
Current U.S.
Class: |
165/104.26 ;
29/890.032 |
Current CPC
Class: |
F28D 15/046 20130101;
Y10T 29/49353 20150115; B23P 2700/09 20130101; F28D 15/0233
20130101 |
Class at
Publication: |
165/104.26 ;
29/890.032 |
International
Class: |
F28D 15/04 20060101
F28D015/04; B21D 53/02 20060101 B21D053/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 15, 2010 |
CN |
201010300331.9 |
Claims
1. A flat heat pipe with an evaporator section and a condenser
section at opposite ends thereof, the flat heat pipe comprising: a
hollow flat casing comprising a top plate and a bottom plate
opposite to the top plate; a first wick structure received in the
casing and extending from the evaporator section to the condenser
section; and a solid, sintered second wick structure disposed in
the casing at the evaporator section, the second wick structure
contacting the top and bottom plates and joining the first wick
structure.
2. The flat heat pipe of claim 1, wherein the second wick structure
is disposed along a center axis of the evaporator section.
3. The flat heat pipe of claim 1, wherein the first wick structure
is a hollow tube made of woven wires.
4. The flat heat pipe of claim 1, wherein the first and second wick
structures cooperatively form a composite wick structure via
sintering.
5. The flat heat pipe of claim 4, wherein a vapor channel is
defined between the composite wick structure and a lateral inner
surface of the casing.
6. The flat heat pipe of claim 1, further comprising another first
wick structure, the second wick structure disposed between the two
first wick structures.
7. The flat heat pipe of claim 6, wherein the casing further
comprises two side plates interconnecting the top and bottom
plates, one of the two first wick structures and one of the two
side plates cooperatively define a first vapor channel
therebetween, and the other first wick structure and the other side
plate cooperatively define a second vapor channel therebetween.
8. The flat heat pipe of claim 1, wherein the first wick structure
is enclosed in the second wick structure at the evaporator
section.
9. The flat heat pipe of claim 8, wherein the casing further
comprises two side plates interconnecting the top and bottom
plates, one of two lateral sides of the second wick structure and
one of the two side plates cooperatively define a first vapor
channel therebetween, and the other lateral side of the second wick
structure and the other side plate cooperatively define a second
vapor channel therebetween.
10. The flat heat pipe of claim 1, further comprising another two
first wick structures, wherein two of the three first wick
structures are disposed at opposite sides of the second wick
structure, respectively, and the other first wick structure is
enclosed in the second wick structure at the evaporator
section.
11. The flat heat pipe of claim 10, wherein the casing further
comprises two side plates interconnecting the top and bottom
plates, one of the two first wick structures disposed at opposite
sides of the second wick structure and one of the two side plates
cooperatively define a first vapor channel therebetween, and the
other of the two first wick structures disposed at opposite sides
of the second wick structure and the other side plate cooperatively
define a second vapor channel therebetween.
12. A flat heat pipe with an evaporator section and a condenser
section at opposite ends thereof, the flat heat pipe comprising: a
hollow flat casing cooperatively formed by a top plate, a bottom
plate opposite to the top plate, and two side plates
interconnecting the top and bottom plates; and a composite wick
structure disposed in the casing, the composite wick structure
comprising a first wick structure in the form of woven wires, and a
solid, sintered second wick structure joining the first wick
structure, the first wick structure extending from the evaporator
section to the condenser section, the second wick structure
disposed only in the evaporator section, and the first and second
wick structures contacting the top and bottom plates of the
casing.
13. The flat heat pipe of claim 12, wherein the second wick
structure is disposed along a center axis of the evaporator
section.
14. The flat heat pipe of claim 12, wherein a first vapor channel
and a second vapor channel are respectively defined between two
lateral sides of the structure and the two side plates of the
casing.
15. The flat heat pipe of claim 14, wherein the first wick
structure is enclosed in the second wick structure in the
evaporator section, and the first and second vapor channels are
respectively defined between two lateral sides of the second wick
structure and the two side plates of the casing.
16. The flat heat pipe of claim 14, wherein the composite wick
structure further comprises another one first wick structure, the
second wick structure is disposed between the two first wick
structures, and the first and second vapor channels are
respectively defined between the two first wick structures and the
two side plates of the casing.
17. The flat heat pipe of claim 16, wherein the composite wick
structure further comprises another one first wick structure
enclosed in the second wick structure in the evaporator
section.
18. A method for manufacturing a heat pipe, the method comprising:
providing a cylindrical mandrel, a hollow cylindrical tube and a
first wick structure, the mandrel defining a longitudinal slot in a
circumferential surface thereof, one end of the mandrel defining a
cutout in the circumferential surface, the cutout communicating
with the slot, and an inner diameter of the tube being
substantially equal to an outer diameter of the mandrel; inserting
the mandrel and the first wick structure into the tube, the first
wick structure received in the slot of the mandrel; filling an
amount of metal powder into the cutout of the mandrel in the tube,
and sintering the metal powder to form a solid second wick
structure, wherein the second wick structure is joined to the first
wick structure and part of an inner surface of the tube; drawing
the mandrel out of the tube; injecting a working medium into the
tube, and evacuating and sealing the tube; and flattening the tube
until the second wick structure contacts another part of the inner
surface of the tube, the two parts of the inner surface of the tube
being at opposite sides of the flattened tube.
19. The method for manufacturing a heat pipe of claim 18, wherein
the cutout is axially shorter than the slot.
20. The method for manufacturing a heat pipe of claim 19, wherein
the cutout defines a generally rainbow-shaped cross section.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is related to two co-pending applications
respectively entitled "FLAT HEAT PIPE WITH VAPOR CHANNEL" (attorney
docket number US32037) and "FLAT HEAT PIPE" (attorney docket number
US32038), assigned to the same assignee of this application and
filed on the same date as this application. The two related
applications are incorporated herein by reference.
BACKGROUND
[0002] 1. Technical Field
[0003] The disclosure generally relates to a heat transfer
apparatus, and particularly to a flat heat pipe with high heat
transfer efficiency.
[0004] 2. Description of Related Art
[0005] Heat pipes are widely used in various fields for heat
dissipation purposes due to their excellent heat transfer
performance. One commonly used heat pipe includes a sealed tube
made of thermally conductive material with a working fluid
contained therein. The working fluid conveys heat from one end of
the tube, typically referred to as an evaporator section, to the
other end of the tube, typically referred to as a condenser
section. Preferably, a wick structure is provided inside the heat
pipe, lining an inner wall of the tube, and drawing the working
fluid back to the evaporator section after it condenses at the
condenser section.
[0006] During operation, the evaporator section of the heat pipe
maintains thermal contact with a heat-generating electronic
component. The working fluid at the evaporator section absorbs heat
generated by the electronic component, and thereby turns to vapor.
Due to the difference in vapor pressure between the two sections of
the heat pipe, the generated vapor moves, carrying the heat with
it, toward the condenser section. At the condenser section, the
vapor condenses after transferring the heat to, for example, fins
thermally contacting the condenser section. The fins then release
the heat into the ambient environment. Due to the difference in
capillary pressure which develops in the wick structure between the
two sections, the condensate is then drawn back by the wick
structure to the evaporator section where it is again available for
evaporation.
[0007] In ordinary use, the heat pipe is flattened to increase a
contact area with the electronic component and enable smaller
electronic products to incorporate the heat pipe. However, this may
result in damage to the wick structure of the heat pipe. When the
wick structure of the heat pipe is damaged, the flow resistance of
the wick structure is liable to be considerably increased. In such
case, the condensate may not be retrieved from the condenser
section in a timely manner, and the heat pipe eventually dries out
at the evaporator section.
[0008] What is needed, therefore, is a flat heat pipe and a method
for manufacturing the heat pipe which can overcome the described
limitations.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] 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 placed upon clearly illustrating the principles of the
present embodiments. Moreover, in the drawings, like reference
numerals designate corresponding parts throughout the various
views, and all the views are schematic.
[0010] FIG. 1 is an abbreviated, side plan view of a heat pipe in
accordance with a first embodiment of the disclosure.
[0011] FIG. 2 is an enlarged, transverse cross section of the heat
pipe of FIG. 1, taken along line II-II thereof.
[0012] FIG. 3 is an enlarged, transverse cross section of the heat
pipe of FIG. 1, taken along line thereof.
[0013] FIG. 4 is similar to FIG. 2, but shows a transverse cross
section of a heat pipe according to a second embodiment of the
disclosure.
[0014] FIG. 5 is similar to FIG. 2, but shows a transverse cross
section of a heat pipe according to a third embodiment of the
disclosure.
[0015] FIG. 6 is a flowchart showing an exemplary method for
manufacturing the heat pipe of FIG. 1.
[0016] FIG. 7 is an exploded, isometric view of a cylindrical tube
and a cylindrical mandrel used for manufacturing the heat pipe
according to the method of FIG. 6.
[0017] FIG. 8 is a transverse cross section of a semi-finished heat
pipe manufactured according to the method of FIG. 6, showing two
first wick structures and a second wick structure received in the
cylindrical tube of FIG. 7.
DETAILED DESCRIPTION
[0018] Referring to FIGS. 1-3, a heat pipe 10 in accordance with a
first embodiment of the disclosure is shown. The heat pipe 10 is a
flat heat pipe, and includes a flat tube-like casing 11 with two
ends thereof sealed, and a variety of elements enclosed in the
casing 11. Such elements include two first wick structures 12, 13,
a second wick structure 14, and a working medium (not shown).
[0019] The casing 11 is made of metal or metal alloy with a high
heat conductivity coefficient, such as copper, copper-alloy, or
other suitable material. The casing 11 is elongated, and has an
evaporator section 111 and an opposite condenser section 113 along
a longitudinal direction thereof. The casing 11 has a width larger
than its height. In particular, the casing 11 has a flattened
transverse cross section. To meet the weight requirements of common
electronic products, the height of the casing 11 is preferably less
than 2 millimeters (mm) The casing 11 is hollow, and includes a top
plate 114, a bottom plate 115 opposite to the top plate 114, and
two side plates 116, 117 interconnecting the top and bottom plates
114, 115. The top and bottom plates 114, 115 are flat and parallel
to each other. The side plates 116, 117 are arcuate and
respectively disposed at opposite lateral sides of the casing
11.
[0020] The first wick structures 12, 13 are elongated hollow tubes,
and extend longitudinally from the evaporator section 111 to the
condenser section 113. An inner space 140 is longitudinally defined
in each of the first wick structures 12, 13. The first wick
structures 12, 13 are monolayer-type structures, formed by weaving
a plurality of metal wires such as copper or stainless steel wires.
The first wick structures 12, 13 thus have a plurality of pores
therethrough. Alternatively, the first wick structures 12, 13 can
be multilayer-type structures layered along a radial direction
thereof by weaving a plurality of metal wires. Each first wick
structure 12, 13 has a flattened transverse cross section, similar
in principle to the flattened transverse cross section of the
casing 11. In particular, each first wick structure 12, 13 includes
a top wall 121, a bottom wall 122 opposite to the top wall 121, and
two sidewalls 123, 124 interconnecting the top and bottom walls
121, 122. The top and bottom walls 121, 122 are flat and parallel
to each other. The top and bottom walls 121, 122 contact the top
and bottom plates 114, 115 of the casing 11, respectively. The
sidewalls 123, 124 are arcuate and respectively disposed at
opposite lateral sides of each first wick structure 12, 13.
[0021] The first wick structures 12, 13 are spaced from each other,
and also from the side plates 116, 117 of the casing 11. The
sidewall 123 of the first wick structure 12 and the side plate 116
adjacent to the first wick structure 12 cooperatively define a
first vapor channel 141 therebetween. The sidewall 123 of the first
wick structure 13 and the side plate 117 adjacent to the first wick
structure 13 cooperatively define a second vapor channel 142
therebetween. The two first wick structures 12, 13 cooperatively
define a third vapor channel 143 therebetween. The third vapor
channel 143 is located at a center of the casing 11. The first,
second and third vapor channels 141, 142, 143, provide passages
through which the vapor flows from the evaporator section 111 to
the condenser section 113.
[0022] The second wick structure 14 is disposed along a center axis
of the evaporator section 111, and contacts the top and bottom
plates 114, 115 of the casing 11. The second wick structure 14
occupies a portion of the third vapor channel 143 at the evaporator
section 111 of the casing 11. The second wick structure 14 is a
solid wick structure made of sintered copper powder. The second
wick structure 14 is joined to the sidewalls 124 of the first wick
structures 12, 13 via sintering. The first and second wick
structures 12, 13, 14 cooperatively form a composite wick structure
17 in the casing 11. The first and second channels 141, 142 are
defined between opposite lateral sides of the composite wick
structure 17 and the side plates 116, 117 of the casing 11,
respectively.
[0023] The working medium is saturated in the first and second wick
structures 12, 13, 14. The working medium is usually selected from
a liquid such as water, methanol, or alcohol, which has a low
boiling point. The casing 11 of the heat pipe 10 is evacuated and
hermetically sealed after the working medium is injected into the
casing 11 and saturated in the first and second wick structures 12,
13, 14. Thus, the working medium can easily evaporate when it
receives heat at the evaporator section 111 of the heat pipe
10.
[0024] In operation, the evaporator section 111 of the heat pipe 10
is placed in thermal contact with a heat source (not shown) that
needs to be cooled. The heat source can, for example, be a central
processing unit (CPU) of a computer. The working medium contained
in the evaporator section 111 of the heat pipe 10 is vaporized when
receiving heat generated by the heat source. The generated vapor
moves from the evaporator section 111 via the vapor channels 141,
142 to the condenser section 113. After the vapor releases its heat
and condenses in the condenser section 113, the condensate is
returned by the first and second wick structures 12, 13, 14 to the
evaporator section 111 of the heat pipe 10, where the condensate is
again available for evaporation.
[0025] In the present heat pipe 10, the second wick structure 14 is
solid, and contacts the top and bottom plates 114, 115 of the
casing 11. Therefore, the second wick structure 14 provides support
for the casing 11 during flattening of the heat pipe 10. This
prevents blockage of the vapor channels 141, 142, 143, promoting
vapor flow through the heat pipe 10. In addition, the first wick
structures 12, 13 are not easily damaged during the flattening.
Furthermore, the first and second wick structures 12, 13, 14
cooperatively form the composite wick structure 17 at the
evaporator section 111 of the heat pipe 10. This increases
capillary force, and reduces flow resistance and heat resistance.
As a result, the condensate is returned to the evaporator section
111 of the heat pipe 10 rapidly, thus preventing potential drying
out at the evaporator section 111. Moreover, the second wick
structure 14 is not disposed in the condenser section 113 of the
heat pipe 10. This enlarges the vapor channels in the condenser
section 113, and further promotes the flow of the working medium in
the heat pipe 10.
[0026] In alternative embodiments, the quantity of first and second
wick structures in the heat pipe 10 can vary. The following
embodiments include examples of such variations.
[0027] Referring to FIG. 4, a heat pipe 20 in accordance with a
second embodiment of the disclosure is shown. The heat pipe 20 has
the same structure as the heat pipe 10 of the first embodiment,
except for the wick structures. In the heat pipe 20, there is only
one first wick structure 22. The first wick structure 22 is
disposed in the center of the casing 11. A second wick structure 24
has a generally rectangular cross section, with the first wick
structure 22 being embedded in the second wick structure 24. The
first and second wick structures 22, 24 cooperatively form a
composite wick structure 27 in an evaporator section 211 of the
heat pipe 20. In the evaporator section 211 of the heat pipe 20,
opposite lateral sides of the second wick structure 24 and the side
plates 116, 117 of the casing 11 cooperatively define a first vapor
channel 241 and a second vapor channel 242 therebetween,
respectively. In other words, the first and second channels 241,
242 are defined between opposite lateral sides of the composite
wick structure 27 and the side plates 116, 117 of the casing 11,
respectively.
[0028] Referring to FIG. 5, a heat pipe 30 in accordance with a
third embodiment of the disclosure is shown. The heat pipe 30 has
the same structure as the heat pipe 10 of the first embodiment,
except for the wick structures. In the heat pipe 30, there are
three first wick structures 12, 13, 35. The first wick structure 35
is disposed in the center of the casing 11, and is embedded in a
second wick structure 34.
[0029] FIG. 6 summarizes an exemplary method for manufacturing the
heat pipe 10. The method includes the following steps:
[0030] Referring also to FIGS. 7 and 8, firstly, a mandrel 15, two
first wick structures 16, 17, and a tube 18 are provided. The
mandrel 15 is elongated and generally cylindrical, and defines two
longitudinal slots 152, 153 in a circumferential surface 151
thereof. The slots 152, 153 are symmetrical relative to each other,
and span through both a front end surface and a rear end surface of
the mandrel 15. A cross section of each of the slots 152, 153
defines part of a circle, i.e., a large sector. A front end of the
mandrel 15 further defines a cutout 154 in a portion of the
circumferential surface 151 between the slots 152, 153. The cutout
154 is axially shorter than each slot 152, 153. The cutout 154
defines a generally rainbow-shaped cross section, and communicates
with the slots 152, 153. The tube 18 is hollow and cylindrical, and
is made of highly heat conductive metal, such as copper, and so on.
An inner diameter of the tube 18 is substantially equal to an outer
diameter of the mandrel 15. The first wick structures 16, 17 are
hollow and cylindrical, and each have an annular cross section.
Each of the first wick structures 16, 17 has an outer diameter
substantially equal to an inner diameter of Page of each of the
slots 152, 153 of the mandrel 15.
[0031] The first wick structures 16, 17 are horizontally inserted
into the slots 152, 153 of the mandrel 15, respectively. The
mandrel 15 with the first wick structures 12, 13 is inserted into
the tube 18. An amount of metal powder is filled into the cutout
154 of the mandrel 15 in the tube 18. The tube 18 with the mandrel
15, the metal powder and the first wick structures 16, 17 is heated
at high temperature until the metal powder sinters to form a second
wick structure 19. The second wick structure 19 is thereby attached
to an inner surface of the tube 18, and joins the first wick
structures 16, 17. The mandrel 18 is then drawn out of the tube 18.
Subsequent processes such as injecting a working medium into the
tube 18, and evacuating and sealing the tube 18, can be performed
using conventional methods. Thereby, a straight circular heat pipe
40 is attained. Finally, the circular heat pipe 40 is flattened
until the second wick structure 19 contacts the flattened tube 18
at opposite sides thereof, thus forming the flat heat pipe 10 as
illustrated in FIGS. 1-3. That is, the flattened tube 18 forms the
casing 11, the flattened first wick structures 16, 17 form the
first wick structures 12, 13, and the flattened second wick
structure 19 forms the second wick structure 14.
[0032] Advantages of the method include the following. The cutout
154 is defined in a portion of the circumferential surface of the
front end of the mandrel 15. As a result, the second wick structure
19 is attached to a portion of the inner surface of the tube 18
between the two first wick structures 16, 17. Thus, the second wick
structure 19 is not easily damaged during the flattening
operation.
[0033] It should be understood that the cutout 154 and the slots
152, 153 of the mandrel 15 are adapted for forming the first and
second wick structures 12, 13, 14. The configurations and
arrangements of the cutout 154 and the slots 152, 153 can be
changed according to the particular wick structures needed to for
another kind of desired flat heat pipe.
[0034] It is to be further understood that even though numerous
characteristics and advantages of the present embodiments have been
set forth in the foregoing description, together with details of
the structures and functions 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.
* * * * *