US20120175084A1

US20120175084A1 - Heat pipe with a radial flow shunt design

Info

Publication number: US20120175084A1
Application number: US12/987,158
Authority: US
Inventors: Chin-Hsing Horng
Original assignee: Individual
Current assignee: Individual
Priority date: 2011-01-09
Filing date: 2011-01-09
Publication date: 2012-07-12

Abstract

A heat pipe includes a pipe body filled up with a working fluid and having opposing evaporation segment and condensing segment, a first wick structure having ribs axially extending through the evaporation segment and the condensing segment, a channel defined between each two adjacent ribs and grooves transversely cut through the ribs, and a second wick structure sintered and joined to a predetermined part of the first wick structure in the evaporation segment to fill in the channels and the spiral grooves and to cover the ribs.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to heat pipes for transfer of heat between two solid interfaces and more particularly, to a heat pipe with a composite wick structure having a radial shunt design.
2. Description of the Related Art
For the advantages of small size, light weight, long lifespan, high thermal conductivity, long distance heat transfer and pressure-free heat transfer, heat pipe is intensively used in different fields for heat transfer and dissipation. A heat pipe combines the principles of both thermal conductivity and phase transition to efficiently manage the transfer of heat between two a hot side and a cold side. At the hot side of the heat pipe, a liquid in contact turns into a vapor by absorbing the heat of the surface of the hot side. The vapor condenses back into a liquid at the cold side, releasing the latent heat. The liquid then returns to the hot side through the wick structure where it evaporates once more and repeats the cycle.
In the heat pipe industry, manufacturers commonly use a composite wick structure to substitute for a simple wick structure, avoiding the drawbacks of a simple wick structure. However, regular composite wick structures are not designed for multi-heat-source application. Regular composite wick structures includes multiple wicks arranged in one same evaporation segment or different axial segments of the pipe body to gradually increase the capillary force, avoiding pressure loss when the working fluid is flowing back. As the channels of the composite wick structure extend in axial direction and have approximately the same diameter, the control of the flow resistance is easy. However, because the channels extend axially in a parallel manner, the working fluid cannot flow from one channel to another. Thus, the working fluid in the channels opposite to the heat source or at each lateral side relative to the heat source cannot efficiently transfer heat subject to phase change. Further, when using a fiber-type screen or sintered metallic wick structure to increase the capillary force, the flow resistance will be relatively increased.

SUMMARY OF THE INVENTION

The present invention has been accomplished under the circumstances in view. It is the main object of the present invention to provide a heat sink, which has a second wick structure sintered at a first wick structure to increase the working fluid storage capacity and to enhance the working fluid flowing speed and phase cycling, avoiding dry burning and improving the fluid evaporation speed.
To achieve this and other objects of the present invention, a heat pipe includes a pipe body filled up with a working fluid and having opposing evaporation segment and condensing segment, a first wick structure having ribs axially extending through the evaporation segment and the condensing segment, a channel defined between each two adjacent ribs and grooves transversely cut through the ribs, and a second wick structure sintered and joined to a predetermined part of the first wick structure in the evaporation segment to fill in the channels and the spiral grooves and to cover the ribs.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 2 is a cross-sectional view of a heat pipe in accordance with a first embodiment of the present invention.

FIG. 2 is a front view in section of the heat pipe in accordance with the first embodiment of the present invention.

FIG. 3 is an enlarged view of a part of FIG. 2.

FIG. 4 is a schematic sectional side view of the first embodiment of the present invention, illustrating an operation status of the heat pipe.

FIG. 5 is a cross-sectional view of a heat pipe in accordance with a first embodiment of the present invention.

FIG. 6 is a front view in section of the heat pipe in accordance with the second embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIGS. 1 and 2, a heat pipe in accordance with a first embodiment of the present invention is shown comprising a pipe body 1, a first wick structure 2 located on the surface of the inside wall of the pipe body 1, and a second wick structure 3 formed on a part of the surface of the first wick structure 2 by a sintering technique.
The pipe body 1 comprises opposing evaporation segment 11 and condensing segment 12, and has a working fluid filled therein.
The first wick structure 2 comprises a plurality of ribs 23 axially extending through the evaporation segment 11 and the condensing segment 12, a channel 21 defined between each two adjacent ribs 23, and a plurality of spiral grooves 22 arranged in the evaporation segment 11 and transversely cut through the ribs 23 to keep the channels 21 in communication with one another. Thus, the channels 21 are intersected with the spiral grooves 22, forming a lattice pattern. The spiral grooves 22 can be formed by means of milling, embossing, or gorging. Further, the spiral grooves 22 can have different capillary radiuses greater or smaller than the capillary radiuses of the channels 21. Alternatively, some spiral grooves 22 can have relatively greater capillary radiuses than the capillary radiuses of the channels 21, and some other spiral grooves 22 can have relatively smaller capillary radiuses than the capillary radiuses of the channels 21.
The second wick structure 3 is sintered and joined to a predetermined part of the surface of the first wick structure 2. The second wick structure 3 fills in the channels 21 and the spiral grooves 22 and covers the surface of the ribs 23. Further, the second wick structure 3 is divided into multiple structural parts that extend axially in a parallel relationship subject to a predetermined pitch. Further, the second wick structure 3 can be a wick structure of high water content fiber-type screen, sintered metallic wick structure, polymer wick structure, composite wick structure, or their combination.
Referring to FIGS. 3 and 4 and FIGS. 1 and 2 again, during application, attach the thermal device(s) 4 to the bottom surface of the evaporation segment 11 of the pipe body 1 corresponding to the second wick structure 3. During working of the thermal device(s) 4, the working fluid in the evaporation segment 11 of the pipe body 1 evaporates to vapor absorbing thermal energy from the thermal device(s) 4, thereafter vapor migrates to the condensing segment 12 of the pipe body 1 where vapor condenses back to fluid and is absorbed by the capillary force of the first wick structure 2 releasing thermal energy, and thereafter the working fluid flows back to the evaporation segment 11 of the pipe body 1.
Further, as the channels 21 of the first wick structure 2 are respectively defined between each two adjacent ribs 23, the working fluid is prohibited from flowing among the channels 21. Therefore, the channels 21 that are disposed adjacent to the thermal device(s) 4 direct absorb heat from the thermal device(s) 4 to cause the working fluid to evaporate. The other channels 21 that are disposed far from the thermal device(s) 4 can simply absorb heat transferred by the pipe body 1 for heating the working fluid being carried therein into vapor. Subject to the design of the spiral grooves 22, the working fluid, after the condensing stage, is guided back from the condensing segment 12 to the evaporation segment 11 of the pipe body 1. Thus, the channels 21 and spiral grooves 22 of the first wick structure 2 are fully utilized. Further, the total flow path cross section of the second wick structure 3 is relatively greater, and the flowing of the working fluid is free from the effect of gravity, enhancing fluid evaporation.
Referring to FIGS. 5 and 6, as an alternate form of the present invention, the second wick structure 3 can be sintered at the surface of the evaporation segment 11, achieving rapid evaporation of the working fluid.
In conclusion, the invention provides a heat pipe that has the advantages and features as follows:
1. By means of the spiral grooves 22 to connect the channels 21, the second wick structure 2 rapidly guides the working fluid back from the condensing segment 12 to the evaporation segment 11 of the pipe body 1 around the thermal device(s) 4 for absorbing heat from the thermal device(s) 4 for quick dissipation. Further, the design of the channels 21 and the spiral grooves 22 greatly increases the working fluid storage capacity, avoiding dry burning and enhancing the evaporation speed.
2. The first wick structure 2 has low flow resistance, high flowing speed, limited total flow path cross section area, small working fluid storage capacity and gravity constrained characteristics. On the contrary, the second wick structure 3 has high flow resistance, low flowing speed, large total flow path cross section area, high working fluid storage capacity characteristics and allows free flowing of the working fluid without being subject to the effects of gravity. By means of the spiral grooves 22 to connect the channels 21 in the evaporation segment 11 and utilizing the second wick structure 3 to increase the evaporation area, the invention combines the advantages of the first wick structure 2 and the second wick structure 3 and eliminates their drawbacks, allowing adjustment of the flowing speed locally. Subject to divisional arrangement of the first wick structure 2 and the second wick structure 3 and the characteristic that the first wick structure 2 is in communication with the second wick structure 3, the working fluid is shunted for transferring heat from different thermal devices.
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.

Claims

1. A heat pipe, comprising:

a pipe body filled up with a working fluid, said pipe body comprising opposing evaporation segment and condensing segment;

a first wick structure comprising a plurality of ribs axially extending through said evaporation segment and said condensing segment, a channel defined between each two adjacent ribs of said ribs, and a plurality of grooves arranged in said evaporation segment and cut through said ribs to keep said channels in communication with one another; and

a second wick structure sintered and joined to a predetermined part of said first wick structure, said second wick structure filled in said channels and said spiral grooves and covering said ribs.

2. The heat pipe as claimed in claim 1, wherein said grooves are spirally cut through said ribs such that said channels and said grooves are intersected, forming a lattice pattern.

3. The heat pipe as claimed in claim 1, wherein said second wick structure filled in said channels and said spiral grooves and covering said ribs in said evaporation segment of said pipe body.