U.S. patent application number 10/201877 was filed with the patent office on 2003-10-16 for heat pipe with inner layer.
Invention is credited to Lai, Cheng-Tien, Lee, Tsung Lung, Tien, Yun-Chu, Zhang, Zili.
Application Number | 20030192671 10/201877 |
Document ID | / |
Family ID | 4772958 |
Filed Date | 2003-10-16 |
United States Patent
Application |
20030192671 |
Kind Code |
A1 |
Lee, Tsung Lung ; et
al. |
October 16, 2003 |
Heat pipe with inner layer
Abstract
A heat pipe (10) includes a main body (12), an inner layer (16),
a chamber (13) and working material (18). The main body is made of
metallic material having a high heat-transfer coefficient. The
chamber is surrounded by the inner layer, and is substantially a
vacuum. The working material is sealed in the chamber. The inner
layer is fixed to an inner surface of the main body. The inner
layer is inert to the working material, and isolates the working
material from the main body. Furthermore, the working material
readily globularizes when it is in contact with the inner
layer.
Inventors: |
Lee, Tsung Lung; (Tu-Chen,
TW) ; Lai, Cheng-Tien; (Tu-Chen, TW) ; Zhang,
Zili; (Shenzhen, CN) ; Tien, Yun-Chu;
(Tu-Chen, TW) |
Correspondence
Address: |
WEI TE CHUNG
FOXCONN INTERNATIONAL, INC.
1650 MEMOREX DRIVE
SANTA CLARA
CA
95050
US
|
Family ID: |
4772958 |
Appl. No.: |
10/201877 |
Filed: |
July 23, 2002 |
Current U.S.
Class: |
165/80.3 ;
165/104.26; 165/104.33 |
Current CPC
Class: |
F28D 15/0275 20130101;
F28D 15/046 20130101; F28F 2245/00 20130101 |
Class at
Publication: |
165/80.3 ;
165/104.26; 165/104.33 |
International
Class: |
F28F 007/00; F28D
015/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 16, 2002 |
CN |
0 2226932.0 |
Claims
What is claimed is:
1. A heat pipe comprising: a main body made of metallic material
having great heat transfer capability; an inner layer fixed to an
inner surface of the main body and defining a sealed chamber
therein; and working material sealed in the chamber; wherein the
inner layer is inert to the working material and isolates the
working material from the main body, and wherein the working
material readily globularizes when it is in contact with the inner
layer.
2. The heat pipe as claimed in claim 1, wherein the chamber is
substantially a vacuum.
3. The heat pipe as claimed in claim 2, wherein the working
material has low viscosity and is chemically stable.
4. The heat pipe as claimed in claim 3, wherein the working
material has great heat absorption characteristics, and a low
phase-change threshold temperature.
5. The heat pipe as claimed in claim 4, wherein the working
material is water.
6. The heat pipe as claimed in claim 1, wherein the main body has
low weight, and is resistant to deterioration.
7. The heat pipe as claimed in claim 6, wherein the main body is
made of aluminum.
8. The heat pipe as claimed in claim 6, where the main body is made
of high carbon steel.
9. The heat pipe as claimed in claim 1, wherein the inner layer is
fixed to the inner surface of the main body by electroplating.
10. The heat pipe as claimed in claim 1, wherein the inner layer is
fixed to the inner surface of the main body by displacement.
11. The heat pipe as claimed in claim 1, wherein the inner layer is
made of copper or nickel.
12. The heat pipe as claimed in claim 1, wherein the inner layer
comprises a plurality of protrusions that cooperatively form a
wicking structure.
13. A heat pipe assembly comprising: a chassis adapted to abut
against a heat generating device; a plurality of heat pipes
arranged in a matrix manner, each of said heat pipes including: a
tube-like main body made of metallic material having great heat
transfer capability; an inner layer applied to an inner surface of
the main body and defining a chamber therein; and working material
circulated in the chamber; wherein one end of the main body is in
contact with the chassis.
14. The assembly as claimed in claim 13, wherein said end is
embedded within the chassis.
15. The assembly as claimed in claim 13, wherein said main body is
perpendicular to the chassis.
16. The assembly as claimed in claim 13, further including a
plurality of fins spaced from one another with said heat pipes
engageably extending therethrough.
17. the assembly as claimed in claim 13, wherein said fins are
perpendicular to said heat pipes.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to heat pipes, and more
particularly to a heat pipe which has an inner layer fixed to an
inner surface of the heat pipe.
[0003] 2. Description of Related Art
[0004] Most natural substances exist in one of three states: solid,
liquid, and gaseous. These three states are also called three
phases: solid phase, liquid phase, and gaseous phase. Many
substances can change phases repeatedly with an accompanying
transfer of heat.
[0005] A heat pipe is a device utilizing phase change of working
material to transfer heat from a vaporizing end of the pipe to a
condensing end of the pipe. Commonly, a heat pipe connects between
a heat-generating electronic device and a heat dissipation
apparatus. An inner chamber of the heat pipe is substantially a
vacuum, with liquid working material accommodated therein. In
operation, the working material absorbs heat, becomes vaporized,
and moves away from the vaporizing end. When the vaporized working
material arrives at the condensing end, it condenses back to liquid
form and releases heat. The condensed working material is then
pumped back to the vaporizing end. This continuous cycle transfers
large quantities of heat from the heat-generating electronic
device.
[0006] However, a heat pipe is generally not inert to the working
material. Chemical reaction occurs therebetween, particularly after
prolonged use. The heat pipe is prone to dissolve and become
completely damaged. In addition, gaseous by-products of such
chemical reaction are generally uncondensable during normal
operation of the heat pipe. The uncondensable gaseous by-products
increase a pressure in the chamber of the heat pipe. This retards
vaporization of the working material. Furthermore, the
uncondensable gases are pushed to the condensing end of the heat
pipe by vapor produced at the vaporizing end of the heat pipe. This
decreases an available condensing surface area and adversely
affects the heat transfer capability of the heat pipe. Over time,
the uncondensable gases build up the pressure inside the chamber to
a point where such pressure is equivalent to a maximum pressure at
which the working material can be vaporized. At such point, the
heat pipe can no longer function and must be discarded.
[0007] A further problem is that the working material tends to be
partly absorbed by an inner surface of the heat pipe when it is in
contact with such surface. This retards flow of the working
material along such surface from the condensing end to the
vaporizing end.
[0008] A still further problem is that a conventional heat pipe is
made of copper. This makes the heat pipe unduly heavy, and
increases manufacturing costs. Moreover, a layer of oxide is liable
to be formed on an outer surface of the heat pipe. This adversely
affects the heat transfer capability of the heat pipe.
[0009] It is strongly desired to provide an improved heat pipe
which overcomes the above-mentioned numerous problems.
SUMMARY OF THE INVENTION
[0010] Accordingly, an object of the present invention is to
provide a heat pipe which has an inner layer fixed to an inner
surface of the heat pipe in order to attain optimal heat transfer
capability and durability.
[0011] In order to achieve the object set out above, a heat pipe of
the present invention comprises a main body, an inner layer, a
chamber and working material. The main body is made of a metallic
material having a high heat-transfer coefficient. The chamber is
surrounded by the inner layer, and is substantially a vacuum. The
working material is sealed in the chamber. The inner layer is fixed
to an inner surface of the main body. The inner layer is inert to
the working material, and isolates the working material from the
main body. Furthermore, the working material readily globularizes
when it is in contact with the inner layer.
[0012] Other objects, advantages and novel features of the present
invention will become more apparent from the following detailed
description when taken in conjunction with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a cross-sectional side view of a heat pipe in
accordance with the present invention;
[0014] FIG. 2 is a perspective view of a plurality of the heat
pipes of FIG. 1 engaged with fins and a chassis to form a heat-pipe
heat sink; and
[0015] FIG. 3 is a cross-sectional side view of the heat-pipe heat
sink of FIG. 2, taken along line III-III thereof and showing
movement of working material in the heat pipes.
DETAILED DESCRIPTION OF THE INVENTION
[0016] Reference will now be made to the drawing figures to
describe the present invention in detail.
[0017] FIG. 1 shows a heat pipe 10 of the present invention. FIG. 2
shows a plurality of the heat pipes 10 engaged with fins 20 and a
chassis 30 to form a heat-pipe heat sink. The chassis 30 is
attachable to a heat-generating electronic device (not shown) such
as a central processing unit (CPU), for cooling the heat-generating
electronic device.
[0018] The heat pipe 10 comprises a main body 12, an inner layer
16, a chamber 13, and working material 18. The chamber 13 is
surrounded by the inner layer 16, and is substantially a vacuum.
The working material 18 is sealed in the chamber 13. The working
material 18 is a liquid at room temperature and pressure, has low
viscosity, and is chemically stable. The working material 18 in
liquid form has great heat absorption characteristics, and a low
phase-change threshold temperature. Water is suitable working
material 18. The main body 12 is made of metallic material having a
high heat-transfer coefficient, such as aluminum or high carbon
steel. The main body 12 has a low weight, and is resistant to
physical and chemical deterioration. The inner layer 16 is a thin
layer fixed to an inner surface of the main body 12 by
electroplating, displacement, or other suitable means. The inner
layer 16 has a high heat-transfer coefficient for quickly
conducting heat to the main body 12. Accordingly, the inner layer
16 is made of copper, nickel or other suitable material. The inner
layer 16 is inert to the working material 18. That is, no chemical
reaction occurs between the inner layer 16 and the working material
18, even during operation of the heat pipe 10. Furthermore, the
working material 18 readily globularizes when it is in contact with
the inner layer 16. That is, the working material 18 is not
absorbed by the inner layer 16 when it is in contact with the inner
layer 16. This allows the working material 18 to readily flow along
a surface of the inner layer 16. The inner layer 16 comprises a
plurality of protrusions (not shown) that cooperatively form a
wicking structure in the heat pipe 10, for facilitating
recirculation of condensed working material 18.
[0019] Referring also to FIG. 3, vaporizing ends of the heat pipes
10 are fixed in the chassis 30 such that the heat pipes 10 are
oriented perpendicular to the chassis 30. A plurality of the fins
20 is stacked at uniform intervals on the chassis 30. The fins 20
are parallel to each other and to the chassis 30, and abuttingly
surround the heat pipes 10. The fins 20 provide ample surface area
for dissipation of heat into surrounding air. The working material
18 is located at the condensing ends of the heat pipes 10.
[0020] During operation of each heat pipe 10, heat is transferred
from the heat-generating electronic device to the chassis 30. The
working material 18 absorbs heat from the chassis 30, and is
vaporized. Therefore, a temperature of the chassis 30 is decreased.
The vaporized working material 18 then travels to a distal
condensing end of the heat pipe 10, whereat a slightly lower
temperature causes the vaporized working material 18 to condense
back to liquid form and release its latent heat of vaporization to
the fins 20. The vaporized working material 18 is then pumped back
to the vaporizing end by capillary forces of the wicking structure,
and by the force of gravity. This continuous cycle of the working
material 18 in the chamber 13 transfers large quantities of heat
from the chassis 30 to the fins 20. Thus, reliable heat transfer
from the heat-generating electronic device is achieved.
[0021] In the present invention, the inner layer 16 is fixed to the
inner surface of the main body 12 to isolate the working material
18 from the main body 12. The inner layer 16 is inert to the
working material 18. No chemical reaction can occur between the
working material 18 and the main body 12. This protects the main
body 12 from deterioration, even after prolonged operation of the
heat pipe 10. Because no chemical reaction occurs, no uncondensable
gaseous by-products are produced. Vaporized working material 18 can
freely condense back to liquid form. A maximum condensing surface
is utilized in the chamber 13, and pressure in the chamber 13 is
maintained at a low level substantially that of a vacuum.
Vaporization of the liquid working material 18 can readily take
place. In addition, because the working material 18 readily
globularizes when it is in contact with the inner layer 16,
condensed working material readily flows along the surface of the
inner layer 16 from the condensing end of the heat pipe 10 to the
vaporizing end thereof. Accordingly, the heat pipe 10 can maintain
great heat transfer capability even after prolonged use.
Furthermore, the main body 12 has low weight, and is resistant to
physical and chemical deterioration. The main body 12 provides more
advantage compared with typical heat pipes made of copper.
[0022] 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.
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