U.S. patent application number 11/184813 was filed with the patent office on 2006-12-21 for heat pipe.
This patent application is currently assigned to Yuh-Cheng Chemical Ltd.. Invention is credited to Jeng-Ming Pai.
Application Number | 20060283575 11/184813 |
Document ID | / |
Family ID | 37572205 |
Filed Date | 2006-12-21 |
United States Patent
Application |
20060283575 |
Kind Code |
A1 |
Pai; Jeng-Ming |
December 21, 2006 |
Heat pipe
Abstract
A heat pipe includes a hollow elongated casing, which defines
therein an enclosed chamber, a working fluid filled in the enclosed
chamber; and a wick, which is formed on the inside wall of the
casing around the enclosed fluid chamber and has two parts that
have different porosities.
Inventors: |
Pai; Jeng-Ming; (Taipei
City, TW) |
Correspondence
Address: |
BROWDY AND NEIMARK, P.L.L.C.;624 NINTH STREET, NW
SUITE 300
WASHINGTON
DC
20001-5303
US
|
Assignee: |
Yuh-Cheng Chemical Ltd.
Taipei City
TW
|
Family ID: |
37572205 |
Appl. No.: |
11/184813 |
Filed: |
July 20, 2005 |
Current U.S.
Class: |
165/104.26 |
Current CPC
Class: |
F28D 15/046
20130101 |
Class at
Publication: |
165/104.26 |
International
Class: |
F28D 15/00 20060101
F28D015/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 16, 2005 |
TW |
94120074 |
Claims
1. A heat pipe comprising: a hollow elongated casing, said casing
defining therein an enclosed chamber; a working fluid disposed in
said enclosed chamber; and a wick formed on an inside wall of said
casing; wherein said wick has a first part and a second part, said
first part and said second part have different porosities.
2. The heat pipe as claimed in claim 1, wherein said first part of
the wick has a porosity within 55%-60%; said second part of the
wick has a porosity within 65%-80%.
3. The heat pipe as claimed in claim 2, wherein said casing has a
heating end and a cooling end opposite said heating end; said first
part of the wick is located at said heating end, and said second
part is located at said cooling end.
4. The heat pipe as claimed in claim 2, wherein said casing has a
heating end and a cooling end opposite to said heating end; said
wick further has a third part, said third part having a porosity
within about 55%-60%, said first part of the wick being disposed at
said heating end, said third part of the wick being disposed at
said cooling end, said second part of the wick being located
between said first part and said third part of the wick.
5. The heat pipe as claimed in claim 1, wherein said wick is
sintered from copper powder or alloy powder of copper and
silver.
6. The heat pipe as claimed in claim 1, wherein said first part and
said second part of the wick are axially arranged in a line.
7. The heat pipe as claimed in claim 1, wherein said first part of
the wick is bonded to the inside wall of said casing, and said
second part of the wick is bonded to said first part of the wick.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates generally to heat transferring
devices and more particularly, to a high-performance heat pipe of
which the wick has different porosities at different parts for
different functions.
[0003] 2. Description of the Related Art
[0004] A conventional heat pipe generally comprises a hollow metal
tube, which has the both ends closed, a working fluid, for example,
pure water filled in the metal tube, and a wick formed of copper
powder on the inside wall of the metal tube by sintering. The wick
has pores for absorbing the working fluid.
[0005] When one end of the heat pipe touched a heat source, the
pure water at the heating end is vaporized, and produced steam is
quickly dissipated to the other end, namely, the cold end where
steam is condensed into water to release latent heat. At this time,
condensed water flows back to the heating end through the pores in
the wick, completing one thermal cycle. By means of the alternation
of the working fluid between the liquid phase and the gas phase,
the heat pipe transfers a big amount of heat energy.
[0006] To facilitate fabrication, the wick of a heat pipe is made
having a uniform porosity. However, the porosity has a great
concern with the performance of the heat pipe. A wick having a
relatively lower porosity provides a relatively better capillary
effect, however its flow path function for carrying the working
fluid is relatively poorer. On the contrary, a wick having a
relatively higher porosity provides a relatively better flow patch
function for carrying the working fluid, however its capillary
effect is relatively weaker. Therefore, it is an important work how
to maintain the capillary effect of the wick while improving the
flow path function for carrying the working fluid.
SUMMARY OF THE INVENTION
[0007] The present invention has been accomplished under the
circumstances in view. It is the main object of the present
invention to a high-performance heat pipe, which uses a wick that
provides a satisfactory capillary effect and flow path function for
carrying the working fluid.
[0008] To achieve this and other objects of the present invention,
the wick of the heat pipe has at least two different porosities to
provide a satisfactory capillary effect and flow path function for
carrying the working fluid, thereby improving the thermal transfer
performance of the heat pipe.
[0009] In one embodiment of the present invention, the wick has
axially divided multiple parts that have different porosities. In
another embodiment of the present invention, the wick has radially
divided multiple parts that have different porosities. Preferably,
the wick has two parts, namely, the first part that has a porosity
within about 55%-60%, and the second part that has a porosity
within about 65%-80%.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. I is a schematic sectional view of a heat pipe
according to the present invention.
[0011] FIG. 2 is a schematic sectional view of an alternate form of
the heat pipe according to the present invention.
[0012] FIG. 3 is a schematic sectional view of another alternate
form of the heat pipe according to the present invention.
[0013] FIG. 4 is a sectional view taken along line 4-4 of FIG.
3.
DETAILED DESCRIPTION OF THE INVENTION
[0014] Referring to FIG. 1, a heat pipe in accordance with the
present invention is shown comprising a casing 10, a working fluid
20, and a wick 30.
[0015] The casing 10 is a metal tube having the both ends closed
and defining therein an enclosed chamber 11. The working fluid 20
is disposed in the enclosed chamber 11. According to this
embodiment, the working fluid 20 is pure water. Other fluids may be
selectively used as a substitute. Further, the casing 10 has a
heating end 12 and a cooling end 14.
[0016] The wick 20 is formed of copper powder on the inside wall of
the casing 10 by sintering, having axially divided three parts,
namely, the first part 32, the second part 34, and the third part
36. These three parts 32, 34 and 36 have different porosities. The
porosity of the first part 32 of the wick is 55%. The porosity of
the second part 34 of the wick is 80%. The porosity of the third
part 36 of the wick is 60%.
[0017] When the heating end 12 of the casing 10 touched a heat
source, the working fluid 20 is vaporized, and produced steam flows
along the chamber 11 to the cooling end 14 where steam is condensed
into liquid. At this time, the third part 36 provides a better
capillary effect to absorb the working fluid 20 around the cooling
end. When the working fluid 20 is returning to the heating end 12,
and the second part 34 provides a better flow path function to
reduce the resistance to the reverse flowing of the working fluid
20. Further, the first part 36 also provides a better capillary
effect to absorb the working fluid 20 from the second part 34 to
the heating end 12.
[0018] Because the first, second and third parts 32, 34 and 36 of
the wick 30 have different porosities, the wick 30 provides a
better flowing path function and a satisfactory capillary effect,
achieving a high performance in heat transfer.
[0019] Further, alloy powder of copper and silver or other suitable
materials may be selectively used for sintering into the desired
wick 30 instead of copper powder. A porosity ranging from 55%-60%
provides a better capillary effect. A porosity ranging from 65%-80%
provides a better flow path function. In actual fabrication, the
porosity of each part of the wick 30 may be changed subject to
actual requirements, and each part may be made having different
porosities gradually increased from one end to the other.
[0020] FIG. 2 shows an alternate form of the heat pipe according to
the present invention. According to this embodiment, the heat pipe
comprises a casing 10, a working fluid 20, and a wick 30. The wick
30 is axially divided into a first part 32 and a second part 34.
The porosity of the first part 32 is 75%. The porosity of the
second part 34 is 55%. By means of this design, the second part 34
provides a better capillary effect, and the first part 32 provides
a better flow path function.
[0021] FIGS. 3 and 4 show another alternate form of the heat pipe
according to the present invention. According to this embodiment,
the heat pipe comprises a casing 10, a working fluid 20, and a wick
30. The wick 30 is radially divided into a first part 32 and a
second part 34. The first part 32 is disposed at an outer side and
bonded to the inside wall of the casing 10. The porosity of the
first part 32 is 70%. The second part 34 is disposed at an inner
side and bonded to the first part 32. The porosity of the second
part 34 is 58%. The second part 34 provides a better capillary
effect to absorb the working fluid 20. The first part 32 provides a
better flow path function to reduce the resistance to the reverse
flowing of the working fluid 20. Therefore, the heat pipe provides
a better flowing path function and a satisfactory capillary effect,
achieving a high performance in heat transfer.
[0022] Although particular embodiments of the invention have been
described in detail for purposes of illustration, various
modifications and enhancements may be made without departing from
the spirit and scope of the invention. Accordingly, the invention
is not to be limited except as by the appended claims.
* * * * *