US20180209745A1

US20180209745A1 - Loop heat pipe structure

Info

Publication number: US20180209745A1
Application number: US15/415,880
Authority: US
Inventors: Bor-bin Tsai
Original assignee: Asia Vital Components Co Ltd
Current assignee: Asia Vital Components Co Ltd
Priority date: 2017-01-26
Filing date: 2017-01-26
Publication date: 2018-07-26

Abstract

A loop heat pipe structure includes an evaporation chamber, a pipe and a condensing unit. The evaporation chamber has an outlet and an inlet and internally defines a receiving space. A wick structure, a compensation chamber and at least one vapor passage are provided in the receiving space, and the vapor passage has an end communicable with the outlet. The pipe has a first and a second end connected to the inlet and the outlet of the evaporation chamber, respectively, and the first end is located closely adjacent to the wick structure. The condensing unit is externally mounted on the pipe between the first and the second end. With the first end of the pipe being located closely adjacent to the wick structure, the working fluid can flow back to the wick structure more efficiently.

Description

FIELD OF THE INVENTION

The present invention relates to a loop heat pipe structure, and more particularly, to a loop heat pipe structure that enables upgraded vapor-liquid circulation efficiency in the loop heat pipe.

BACKGROUND OF THE INVENTION

The currently available electronic apparatus all have enhanced performance. As a result, electronic elements in the electronic apparatus for signal processing and computing also produce more heat than previous similar electronic elements. The most commonly used heat dissipation elements include heat pipe, heat sink, vapor chamber and so on. These heat dissipation elements are in direct contact with the heat-producing electronic elements to enable further enhanced heat dissipation performance of the electronic elements and prevent the same from burning out due to overheat.
Further, fans can be mounted in the electronic apparatus to enable forced heat dissipation to remove heat from the heat dissipation elements. While fans can indeed upgrade the heat dissipation performance of the electronic apparatus, they are not suitable for use in the electronic apparatus that have a very limited internal space. Therefore, space is also an important factor to be carefully considered when designing the heat dissipation elements.
Based on the concept of vapor-liquid circulation in a heat pipe, a loop heat pipe structure in the form of a loop module has been developed. The loop heat pipe is formed by combining an evaporation chamber with a condensing unit using a pipe connected to between them. The advantage of the loop heat pipe is having its own heat dissipation unit to provide better evaporation and condensation circulation effect. The evaporation chamber has a wick structure disposed therein for storing the liquid-phase working fluid that flows back into the evaporation chamber. The wick structure is provided with a plurality of grooves, in and along which the vapor-phase working fluid flows. The evaporation chamber has at least one surface in contact with a heat source to absorb and transfer heat produced by the heat source to the working fluid stored in the wick structure, the working fluid in the wick structure is therefore heated and evaporated. The vapor-phase working fluid flows through the grooves into the pipe connected to between the evaporation chamber and the condensing unit to finally spread in the condensing unit. The vapor-phase working fluid passing through the condensing unit is then condensed into liquid-phase working fluid again and flows back into the evaporation chamber to complete one cycle of vapor-liquid circulation in the loop heat pipe.
For the currently available flat-type evaporator used in the loop heat pipe, there are two ways for arranging the compensation chamber and the vapor core (i.e. the wick structure with vapor passages) in the evaporator. In the first way, the compensation chamber and the vapor core are vertically positioned to overlap with each other. In the second way, the compensation chamber and the vapor core are positioned at two horizontally spaced positions.
The flat-type evaporator with overlapped compensation chamber and vapor core has a large height or thickness, and is therefore not suitable for a compact electronic apparatus that has very limited internal space.
As to the flat-type evaporator with horizontally positioned compensation chamber and vapor core, since there is some distance between the working fluid in the compensation chamber and the vaporizing surface of the vapor core, there are times the working fluid could not be timely supplied to the vapor core to result in the problem of dry burning of the vapor core.
Therefore, it is desirable to work out a way to overcome the disadvantages of flat-type evaporator in the conventional loop heat pipes.

SUMMARY OF THE INVENTION

A primary object of the present invention is to provide an improved loop heat pipe structure, which overcomes the problem of dry-burning wick structure occurred in the conventional flat-type evaporator with horizontally spaced compensation chamber and wick structure.
To achieve the above and other objects, the loop heat pipe structure provided according to the present invention includes an evaporation chamber, a pipe and a condensing unit.
The evaporation chamber has an outlet and an inlet and internally defines a receiving space. A wick structure, a compensation chamber and at least one vapor passage are provided in the receiving space, and the vapor passage has an end communicable with the outlet. The pipe has a first and a second end connected to the inlet and the outlet of the evaporation chamber, respectively, and the first end is located closely adjacent to the wick structure.
The condensing unit includes a plurality of radiating fins externally mounted on the pipe between the first and the second end.
With the inlet of the evaporation chamber or the first end of the pipe being located closely adjacent to the wick structure, the condensed working fluid can flow back to the wick structure more efficiently to avoid the problem of dry-burning wick structure as found in the conventional evaporation chamber caused by late compensation of working fluid to the wick structure.

BRIEF DESCRIPTION OF THE DRAWINGS

The structure and the technical means adopted by the present invention to achieve the above and other objects can be best understood by referring to the following detailed description of the preferred embodiments and the accompanying drawings, wherein

FIG. 1 is a partially exploded perspective view of a loop heat pipe structure according to a first embodiment of the present invention;

FIG. 2 is an assembled sectional view of the loop heat pipe structure of FIG. 1;

FIG. 3 is an assembled sectional view of a loop heat pipe structure according to a second embodiment of the present invention; and

FIG. 4 is a sectional view showing the loop heat pipe structure according to the present invention in use.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will now be described with some preferred embodiments thereof and by referring to the accompanying drawings. For the purpose of easy to understand, elements that are the same in the preferred embodiments are denoted by the same reference numerals.
Please refer to FIGS. 1 and 2, which are partially exploded perspective view and assembled sectional view, respectively, of a loop heat pipe structure 1 according to a first embodiment of the present invention. As shown, the loop heat pipe structure 1 in the first embodiment includes an evaporation chamber 11, a pipe 12 and a condensing unit 13.
The evaporation chamber 11 is a flat-type evaporation chamber having an outlet 111 and an inlet 112 and internally defines a receiving space 113. In the receiving space 113, there are a wick structure 114, a compensation chamber 115 and at least one vapor passage 1141. The vapor passage 1141 has an end communicable with the outlet 111. According to the present invention, the inlet 112 and the outlet 111 are not necessarily located at the same side on the evaporation chamber 11, but can be located at two opposite sides of the evaporation chamber 11. The compensation chamber 115 is defined by between the receiving space 113 and the wick structure 114. The evaporation chamber 11 is assembled from an enclosure 11 a and a bottom plate 11 b, which are closed to each other to define the receiving space 113 between them. The compensation chamber 115 and the wick structure 114 are horizontally positioned in the receiving space 113 side by side.
The vapor passage 1141 can be selectively provided on a wall surface of the evaporation chamber 11 facing toward the wick structure 114, i.e. on an inner surface of the bottom plate 11 b, or be provided on one side of the wick structure 114 that faces toward a heat-absorbing side of the evaporation chamber 11 in contact with a heat source 3. In the illustrated first embodiment, the vapor passage 1141 is provided on one side of the wick structure 114 facing toward the heat-absorbing side of the evaporation chamber 11. However, it is understood the vapor passage 1141 can be otherwise provided on the inner surface of the bottom plate 11 b of the evaporation chamber 11.
The wick structure 114 is disposed in the receiving space 113 of the evaporation chamber 11, such that the compensation chamber 115 is defined by between the wick structure 114 and the receiving space 113. The inlet 112 and the outlet 111 are located in the vicinity of the wick structure 114. More specifically, the wick structure 114 is located between the inlet 112 and the outlet 111, while the inlet 112 is located above the outlet 111. When a working fluid 2 filled in the loop heat pipe structure 1 flows into the evaporation chamber 11 via the inlet 112, the working fluid 2 will quickly fall into the wick structure 114 due to the gravity, so that the work fluid can flow back to the wick structure 114 more efficiently. When the wick structure 114 is saturated with the working fluid 2, any surplus of the working fluid 2 will flow into the compensation chamber 115. In other operable embodiments, the outlet 111 and the inlet 112 can be provided on the evaporation chamber 11 at the same height, or the outlet 111 can be located higher than the inlet 112, so long as the inlet 112 can be in direct contact with the wick structure 114.
The evaporation chamber 11 further has a liquid passage 116 provided therein. The liquid passage 116 has an end communicable with the inlet 112, and is located at one side of the wick structure 114. More specifically, the liquid passage 116 and the vapor passage 1141 are located at an upper and a lower side of the wick structure 114, respectively.
The pipe 12 has a first end 121 and a second end 122, which are connected to the inlet 112 and the outlet 111 of the evaporation chamber 11, respectively. And, the first end 121 is located closely adjacent to the wick structure 114.
The condensing unit 13 includes a plurality of radiating fins 131, which are sequentially fixed on and spaced along the pipe 12 to be located between the first end 121 and the second end 122 of the pipe 12.
The working fluid 2 is filled in the evaporation chamber 11 or the pipe 12 and is changeable between a vapor phase and a liquid phase. The vapor-phase working fluid 21 in the evaporation chamber 11 flows through the vapor passage 1141 into the pipe 12 via the outlet 111. When the vapor-phase working fluid 21 spreads in the pipe 12 and flows through the section of the pipe 12 having the radiating fins 131 fitted thereon, the vapor-phase working fluid 21 is condensed into the liquid-phase working fluid 22. The vapor-phase working fluid 21 and the liquid-phase working fluid 22 circulate in the entire loop heat pipe structure 1.
The condensing unit 13 is provided on the pipe 12 between the first end 121 and the second end 122, and can include a plurality of radiating fins or a plurality of cooling pipes.
Please refer to FIG. 3, in which a loop heat pipe structure 1 according to a second embodiment of the present invention is shown. The second embodiment is generally structurally similar to the first embodiment, except that the outlet 111 and the inlet 112 in the second embodiment are provided at two opposite sides of the evaporation chamber 11. More specifically, in the second embodiment, the outlet 111 and the inlet 112 are located at a left and a right side of the evaporation chamber 11, respectively. Further, in the second embodiment, the first end 121 of the pipe 12 is extended into the evaporation chamber 11 via the inlet 112 to end at a position above the wick structure 114 and far away from the compensation chamber 115. Therefore, in the second embodiment, the liquid-phase working fluid 22 flowing into the evaporation chamber 11 is directly guided by the first end 121 of the pipe 12 to the wick structure 114. When the wick structure 114 is saturated with the liquid-phase working fluid 22, any surplus of the liquid-phase working fluid 22 will flow into the compensation chamber 115 and be stored therein. With these arrangements, the liquid-phase working fluid 22 can quickly flow back to the wick structure 114 and the problem of dry-burning wick structure due to insufficient water content can be improved.
FIG. 4 shows the loop heat pipe structure 1 of the present invention in use. As shown, in the loop heat pipe structure 1 of the present invention, the evaporation chamber 11 has one side in contact with the heat source 3 and the wick structure 114 is correspondingly provided in the evaporation chamber 11 on the side in contact with the heat source 3. When the evaporation chamber 11 absorbs the heat produced by the heat source 3, the wick structure 114 in the evaporation chamber 11 is heated and the liquid-phase working fluid 22 adsorbed to the wick structure 114 is also heated and finally evaporated to form the vapor-phase working fluid 21. Since the vapor passage 1141 has an end directly connected to the outlet 111 of the evaporation chamber 11, the vapor-phase working fluid 21 flows through the vapor passage 1141 on the wick structure 114 to spread into the pipe 12 via the outlet 111 of the evaporation chamber 11 and the second end 122 of the pipe 12. When the vapor-phase working fluid 21 flowing in the pipe 12 passes the section of the pipe 12 having the condensing unit 13 provided thereat, the vapor-phase working fluid 21 is condensed into the liquid-phase working fluid 22 again. Then, the liquid-phase working fluid 22 flows back into the evaporation chamber 11 via the first end 121 of the pipe 12 and the inlet 112 of the evaporation chamber 11. While the liquid-phase working fluid 22 is guided back to the wick structure 114 due to a capillary action and a pressure difference existed during the phase transition of the working fluid 2, the provision of the inlet 112 above the wick structure 114 also enables the liquid-phase working fluid 22 to more quickly fall into the wick structure 114 due to the gravity to advantageously continue the vapor-liquid circulation in the loop heat pipe structure 1.
Any other type of heat dissipation element (not shown) facilitating increased condensing effect can also be externally connected to the pipe 12 to enable further improved condensing efficiency.
The present invention changes the position of the outlet 111 and the inlet 112 of the evaporation chamber 11 relative to the wick structure 114, such that the liquid-phase working fluid 22 flowing back into the evaporation chamber 11 is first guided to the wick structure 114 instead of the compensation chamber 115. More specifically, since the wick structure 114 is located directly below the inlet 112, the liquid-phase working fluid 22 flowing back into the evaporation chamber 11 via the inlet 112 will first reach the wick structure 114 to be stored therein. When the wick structure 114 is saturated with the liquid-phase working fluid 22, only the surplus of the working fluid 22 will flow into the compensation chamber 115 and be stored therein. With these arrangements, it is able to solve the problem of dry-burning wick structure occurred in the conventional flat-type evaporator, which has horizontally spaced compensation chamber and wick structure, due to a long distance between the working fluid 2 stored in the compensation chamber and the surface of the evaporation chamber in contact with the heat source.
The present invention has been described with some preferred embodiments thereof and it is understood that many changes and modifications in the described embodiments can be carried out without departing from the scope and the spirit of the invention that is intended to be limited only by the appended claims.

Claims

What is claimed is:

1. A loop heat pipe structure, comprising:

an evaporation chamber having an outlet and an inlet and internally defining a receiving space; in the receiving space, there being a wick structure, a compensation chamber and at least one vapor passage; and the vapor passage having an end communicable with the outlet;

a pipe having a first end and a second end connected to the inlet and the outlet, respectively, of the evaporation chamber; and

a condensing unit being externally mounted on the pipe between the first and the second end.

2. The loop heat pipe structure as claimed in claim 1, wherein the vapor passage can be selectively provided on one of the following positions: a wall surface of the evaporation chamber facing toward the wick structure, and one side of the wick structure facing toward the evaporation chamber; and the vapor passage having an end communicable with the outlet.

3. The loop heat pipe structure as claimed in claim 1, further comprising a working fluid filled in one of the evaporation chamber and the pipe; the working fluid being changeable between a vapor-phase working fluid and a liquid-phase working fluid; and the vapor-phase working fluid and the liquid-phase working fluid circulating in an entire internal space of the loop heat pipe structure.

4. The loop heat pipe structure as claimed in claim 1, wherein the evaporation chamber is assembled from an enclosure and a bottom plate, which are closed to each other to define the receiving space between them.

5. The loop heat pipe structure as claimed in claim 1, wherein the outlet and the inlet of the evaporation chamber can be selectively provided on the same side of the evaporation chamber or on two different sides of the evaporation chamber.

6. The loop heat pipe structure as claimed in claim 1, wherein the outlet and the inlet of the evaporation chamber are provided on two different sides of the evaporation chamber, and the first end of the pipe being extended into the receiving space via the inlet of the evaporation chamber to end at one side of the receiving space distant from the compensation chamber.

7. The loop heat pipe structure as claimed in claim 4, wherein the evaporation chamber is in contact with a heat source to absorb heat produced by the heat source, such that the wick structure is heated by the absorbed heat and a liquid-phase working fluid stored in the wick structure is finally vaporized into a vapor-phase working fluid; the vapor-phase working fluid flowing through the vapor passage to leave the evaporation chamber and spread into the pipe via the outlet of the evaporation chamber and the second end of the pipe; the vapor-phase working fluid flowing through the pipe and being condensed by the condensing unit into the liquid-phase working fluid again, which flowing back into the evaporation chamber via the first end of the pipe and the inlet of the evaporation chamber; the first end of the pipe being extended into the evaporation chamber to end at a position above the wick structure for guiding the liquid-phase working fluid directly to the wick structure; whereby when the wick structure is saturated with the liquid-phase working fluid, any surplus of the liquid-phase working fluid flows to the compensation chamber to be stored therein.

8. The loop heat pipe structure as claimed in claim 1, wherein the evaporation chamber is a flat-type evaporation chamber with the compensation chamber and the wick structure being horizontally located in the receiving space side by side.

9. The loop heat pipe structure as claimed in claim 1, wherein the evaporation chamber further has a liquid passage provided therein; the liquid passage having an end communicable with the inlet of the evaporation chamber and being located at one side of the wick structure, such that the liquid passage and the vapor passage are located at an upper and a lower side of the wick structure, respectively.

10. The loop heat pipe structure as claimed in claim 1, wherein the condensing unit is selected from the group consisting of a plurality of radiating fins and a plurality of cooling pipes.