EP2283295A1

EP2283295A1 - Cooling fins for a heat pipe

Info

Publication number: EP2283295A1
Application number: EP09724163A
Authority: EP
Inventors: Richard M. Weber
Original assignee: Raytheon Co
Current assignee: Raytheon Co
Priority date: 2008-03-28
Filing date: 2009-03-20
Publication date: 2011-02-16
Also published as: WO2009120589A1; US20090242170A1

Abstract

According to one embodiment, a cooling apparatus has a number of cooling fins that are coupled to a heat pipe. The heat pipe has a hollow cavity that is at least partially filled with a refrigerant. Each of the cooling fins has a hollow cavity that is fluidly coupled to the hollow cavity of heat pipe such that the refrigerant may flow between the hollow cavity of the heat pipe and hollow cavities of the cooling fins.

Description

COOLING FINS FOR A HEAT PIPE

TECHNICAL FIELD OF THE DISCLOSURE

This disclosure generally relates to cooling devices, and more particularly, to cooling fins for a heat pipe .

BACKGROUND OF THE DISCLOSURE

Thermal control of various components may be an important aspect of their design. For example, computing systems, such as personal computers may have a number of electrical components that generate varying amounts of heat. The temperature of each of these components, however, should be maintained within specified limits to ensure their proper operation.

SUMMARY OF THE DISCLOSURE

Certain embodiments of the disclosure may provide numerous technical advantages. For example, a technical advantage of one embodiment may include the capability to provide efficient thermal energy transfer from the heat pipe to the surroundings . Other technical advantages of other embodiments may include the capability to efficiently move heat within the fin to all parts of the fin and reduce the temperature drop along the length of the fins . Yet other technical advantages of some embodiments may include the capability to improve fin efficiency.

Although specific advantages have been enumerated above, various embodiments may include all, some, or none of the enumerated advantages. Additionally, other technical advantages may become readily apparent to one of ordinary skill in the art after review of the following figures and description.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of embodiments of the disclosure will be apparent from the detailed description taken in conjunction with the accompanying drawings in which:

FIGURE 1 is a top view of one embodiment of cooling fins for a heat pipe according to the teachings of the present disclosure;

FIGURE 2 is a cut-away, side elevational view of the cooling fins and heat pipe that is taken along line 2 of FIGURE 1;

FIGURE 3 is a cut-away, side elevational view of another embodiment of cooling fins for a heat pipe according to the teachings of the present disclosure; and FIGURE 4 is a perspective view showing the cooling fins and heat pipe of FIGURE 1 thermally coupled to a computing rack. DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

It should be understood at the outset that, although example implementations of embodiments of the invention are illustrated below, the present invention may be implemented using any number of techniques, whether currently known or not. The present invention should in no way be limited to the example implementations, drawings, and techniques illustrated below. Additionally, the drawings are not necessarily drawn to scale. Computing devices may have numerous components that generate varying amounts of heat during operation. Computing devices, such as personal computers, may have central processor chips and/or video driver chips that may generate a relatively large amount of heat compared to other components. To cool these components, one or more heat pipes may be used to convey heat away from these components. Dissipation of heat from the heat pipe may be provided by a number of cooling fins thermally coupled to the heat pipe. During operation, air may be blown over the surface of the cooling fins for removal of heat. This configuration may provide adequate heat removal for relatively small heat generating components, such as central processing chips; however, heat removal from devices generating larger amounts of heat may be relatively inefficient.

Removal of heat using cooling fins may be mathematically modeled as a ratio of the cooling fin' s surface area relative to the amount of heat to be removed. That is, the cooling fin's heat removal efficiency may be directly proportional to its surface area. This ratio, however, may not be as efficient at relatively higher levels of heat removal. This loss of efficiency may be due to a thermal conductivity of the fin's material along its elongated extent. For example, a significant portion of heat movement in relatively larger cooling fins may occur along its extent rather than with the surrounding ambient air. This heat movement within the cooling fin may, therefore, limit its ability remove heat from the heat pipe in a relatively efficient manner.

Accordingly, teachings of certain embodiments recognize the use of cooling fins with hollow cavities. Certain embodiments recognize that cooling fins with hollow cavities may efficiently move heat within the fin to all parts of the fin and reduce the temperature drop along the length of the fins. In addition, certain embodiments recognize that cooling fins with hollow cavities may improve fin efficiency. For example, teachings of certain embodiments recognize that cooling fins with hollow cavities may encourage more thermal energy transfer than a solid cooling fin or require less ambient airflow to achieve the same thermal energy transfer as a solid fin.

Furthermore, certain embodiments recognize that the hollow cavity may improve thermal conductivity between the cooling fin and the heat pipe. Teachings of certain embodiments recognize that the connection point between a solid cooling fin and the heat pipe may not be sufficiently conductive; for example, welding joints may provide poor thermal conductivity.

FIGURES 1 and 2 show a cooling apparatus 10 according to one embodiment. Cooling apparatus 10 includes one or more cooling fins 12 coupled to a heat pipe 14. Heat pipe 14 has a hollow cavity 16 that is at least partially filled with a refrigerant. The cooling fins 12 each have a hollow cavity 18 in fluid communication with the hollow cavity 16 of heat pipe 14. During operation, refrigerant may flow through cooling fins 12 for condensation along its extent. In this manner, heat movement through the extent of cooling fins 12 may be reduced.

Teachings of certain embodiments recognize that cooling fins with a hollow cavity may be larger than cooling fins without a hollow cavity. Teachings of certain embodiments recognize that the hollow cavity may improve heat conduction along the length of the cooling fins and thus allow for much longer cooling fins. For example, in some embodiments, cooling fins with a hollow cavity may be in the range of two to five feet in radius. However, embodiments of the cooling fins may be of any length or size.

Heat pipe 14 and cooling fins 12 may be made of any suitable material. In one embodiment, heat pipe 14 and/or cooling fins 12 are constructed of a thermally conducting material such as metal. One example of a thermally conducting material may include copper. In another embodiment, cooling fins 12 may be formed from a sheet of metal having two ends 20. The metal sheet may be bent along an edge 22 and the two ends 20 attached to heat pipe 14 by any suitable approach, such as welding, soldering, brazing, or using an adhesive, such as epoxy.

Heat pipe 14 may be any suitable structure that is configured to move heat from a lower end 24a to an upper end 24b. In one embodiment, heat pipe 14 may be coupled to cooling fins at its upper end 24b in which upper end 24b is maintained at a higher elevation than its lower end 24a. In this manner, refrigerant in its liquid phase may migrate toward lower end 24a during operation. In some embodiments, the cooling fins 12 may be shaped such that the refrigerant in its liquid phase may migrate toward the lower end 24a during operation. For example, in the embodiment illustrated in FIGURE 2, the lower edge of the cooling fin 12 is tapered, providing a drainage mechanism for the refrigerant.

Evaporation of the refrigerant at the lower end 24a may soak up heat according to the thermodynamic principle of latent heat of vaporization. Upon evaporation, the refrigerant may migrate towards upper end 24b for dissipation of heat by cooling fins 12. Teachings of certain embodiments recognize that refrigerant may also flow into cavities 18 of cooling fins 12 for condensing and thus removal of absorbed heat through the fin surface to the ambient air. By moving up into the cavities 18 of the cooling fins 12, a so-called "fin efficiency" is increased, for example, because the thermal energy is not inhibited by a solid fin. In other words, with a conventional solid fin design, thermal energy would collect in the solid material of the fin, decreasing efficiency of the fin. Accordingly, by allowing the fin to be hollow, the thermal transfer barrier of the metal or other structure of which the fin is made is kept to a minimum and transfer of thermal energy can more readily occur.

In the embodiment illustrated in FIGURES 1 and 2, each cooling fin 12 has a tapered body, thicker near the heat pipe 14 and thinner near the tip of the fin 12. Teachings of certain embodiments recognize that a tapered fin design may provide additional energy savings over constant-crossection fins. However, embodiments of the cooling fins 12 may be of any shape or geometry. For example, teachings of certain embodiments recognize that constant-crossection fins may be cheaper to manufacture. In the embodiment illustrated in FIGURES 1 and 2, each cooling fin 12 has a generally planar shape that is parallel to an axis 26 of heat pipe 14. Using this configuration, air movement across cooling fins 12 may be directed in a direction parallel to the axis 26 of heat pipe 14. However, other embodiments may include cooling fins 12 of any shape and oriented in any direction. For example, the cooling fins 12 may be oriented in any direction to match the direction of air movement.

In the embodiment illustrated in FIGURE 3, cooling fins 12' have a generally planar shape that is perpendicular to an axis 26' of a heat pipe 14 ' . In this manner, air may be directed across cooling fins 12' in a direction perpendicular to the axis 26' of heat pipe 14' . In this particular embodiment, the heat pipe 14' is coupled to a number of cooling fins 12' having a hollow cavity 18' in fluid communication with hollow cavity 16' of heat pipe 14' in a manner similar to the embodiment of FIGURES 1 and 2.

Modifications, additions, or omissions may be made to cooling apparatus 10 or 10' without departing from the scope of the disclosure. For example, another embodiment of the cooling apparatus may have cooling fins that are neither parallel or perpendicular to the axis of its associated heat pipe. That is, cooling fins may be configured at an oblique angle to the axis of its heat pipe. FIGURE 4 shows one particular application of cooling apparatus 10 that is coupled to a computing rack 30. In one embodiment, computing rack 30 may be a standardized 19-inch rack, such as a 19-inch rack conforming to the Electronics Industries Alliance 310-D (EIA 310D) specification. Computing rack 30 may include a number of electrical components 32, such as routers, network switches, cable interconnect boxes, power supplies, or rack-mount personal computers. The lower end 24a of heat pip^e 14 may be thermally coupled to one or more components 32 for removal of heat generated by these components 32 during operation.

In the embodiment illustrated in FIGURE 4, the upper end 24b and the cooling fins 12 are surrounded by cowlings 46. The cowlings 46 guide airflow towards the cooling fins 12. In addition, the upper end 24b is separated from the computing rack 30 by a barrier 40. The barrier 40 separates airflow from the components 32. The barrier 40 may also further guide airflow towards the cooling fins 12.

Although FIGURE 4 illustrates the cooling apparatus 10 in connection with the computing rack 30, embodiments of the cooling apparatus 10 are not limited to computer- related applications. Rather, the cooling apparatus 10 may be used in any suitable environment.

Modifications, additions, or omissions may be made to the systems and apparatuses described herein without departing from the scope of the invention. The components of the systems and apparatuses may be integrated or separated. Moreover, the operations of the systems and apparatuses may be performed by more, fewer, or other components. The methods may include more, fewer, or other steps. Additionally, steps may be performed in any suitable order. As used in this document, "each" refers to each member of a set or each member of a subset of a set . Although the present invention has been described with several embodiments, a myriad of changes, variations, alterations, transformations, and modifications may be suggested to one skilled in the art, and it is intended that the present invention encompass such changes, variations, alterations, transformation, and modifications as they fall within the scope of the appended claims.

To aid the Patent Office, and any readers of any patent issued on this application in interpreting the claims appended hereto, applicants wish to note that they do not intend any of the appended claims to invoke 6 of 35 U. S. C. § 112 as it exists on the date of filing hereof unless the words "means for" or "step for" are explicitly used in the particular claim.

Claims

What is claimed is :

1. A cooling apparatus comprising: a heat pipe having a first hollow cavity that is at least partially filled with a refrigerant; and a plurality of cooling fins coupled to the heat pipe, each of the plurality of cooling fins having a second hollow cavity that is in fluid communication with the first hollow cavity such that the refrigerant may flow between the first hollow cavity and the second hollow cavity.

2. The cooling apparatus of Claim 1, wherein the each of the plurality of cooling fins has a generally planar shape that is parallel to an axis of the heat pipe.

3. The cooling apparatus of Claim 1, wherein the each of the plurality of cooling fins has a generally planar shape that is perpendicular to an axis of the heat pipe.

4. The cooling apparatus of Claim 1, wherein the each of the plurality of cooling fins has a generally planar shape that is parallel to a flow of a fluid stream.

5. The cooling apparatus of Claim 4, further comprising one or more cowlings, the one or more cowlings guiding the flow of the fluid stream towards the plurality of cooling fins.

6. The cooling apparatus of Claim 1, wherein: the heat pipe has a top end and a bottom end; the each of the plurality of cooling fins has a top surface and a bottom surface, the top surface being oriented in the direction of the top end, and the bottom surface being oriented in the direction of the bottom end; and the bottom surface is sloped towards the heat pipe such that refrigerant in a liquid form drains towards the bottom end.

7. The cooling apparatus of Claim 1, wherein the refrigerant : vaporizes in the first hollow cavity, travels as a vapor to the second hollow cavity, condensates in the second hollow cavity, and travels as a liquid back to the first hollow cavity.

8. The cooling apparatus of Claim 1, the heat pipe having a first end and a second end opposite the first end, the plurality of cooling fins being located at the first end.

9. The cooling apparatus of Claim 1, wherein the each of the plurality of cooling fins have a radial distance of two feet or greater, as measured from an axis of the heat pipe.

10. The cooling apparatus of Claim 1, wherein: the each of the plurality of cooling fins have a first end and a second end opposite the first end. the each of the plurality of cooling fins are attached to the heat pipe and the first end, the first end has a first thickness corresponding to the thickness of the cooling fin at the first end, the second end has a second thickness corresponding to the thickness of the cooling fin at the second end, and the second thickness is smaller than the first thickness .

11. The cooling apparatus of Claim 1, wherein the each of the plurality of the cooling fins have a tapered fin body with a fin thickness that decreases from the first end to the second end.

12. The cooling apparatus of Claim 1, further comprising a computing rack coupled to one end of the heat pipe and the plurality of cooling fins coupled an opposing end of the heat pipe, the computing rack comprising one or more components of a computing system, the heat pipe operable to move heat from the one or more components to the plurality of cooling fins.

13. A method for cooling an apparatus, comprising: attaching a heat pipe to an apparatus, the heat pipe having a first hollow cavity that is at least partially filled with a refrigerant; and coupling a plurality of cooling fins to the heat pipe, each of the plurality of cooling fins having a second hollow cavity that is in fluid communication with the first hollow cavity such that the refrigerant may flow between the first hollow cavity and the second hollow cavity.

14. The method of Claim 13, wherein the each of the plurality of cooling fins has a generally planar shape that is parallel to an axis of the heat pipe.

15. The method of Claim 13, wherein the each of the plurality of cooling fins has a generally planar shape that is perpendicular to an axis of the heat pipe.

16. The method of Claim 13, wherein the each of the plurality of cooling fins has a generally planar shape that is parallel to a flow of a fluid stream.

17. The method of Claim 16, further comprising providing one or more cowlings, the one or more cowlings guiding the flow of the fluid stream towards the plurality of cooling fins.

18. The method of Claim 13, wherein: the heat pipe has a top end and a bottom end; the each of the plurality of cooling fins has a top surface and a bottom surface, the top surface being oriented in the direction of the top end, and the bottom surface being oriented in the direction of the bottom end; and the bottom surface is sloped towards the heat pipe such that refrigerant in a liquid form drains towards the bottom end.

19. The method of Claim 13, wherein the refrigerant : vaporizes in the first hollow cavity, travels as a vapor to the second hollow cavity, condensates in the second hollow cavity, and travels as a liquid back to the first hollow cavity.

20. The method of Claim 13, the heat pipe having a first end and a second end opposite the first end, the plurality of cooling fins being located at the first end.

21. The method of Claim 13, wherein the each of the plurality of cooling fins have a radial distance of two feet or greater, as measured from an axis of the heat pipe.

22. The method of Claim 13, wherein: the each of the plurality of cooling fins have a first end and a second end opposite the first end, the each of the plurality of cooling fins are attached to the heat pipe and the first end, the first end has a first thickness corresponding to the thickness of the cooling fin at the first end, the second end has a second thickness corresponding to the thickness of the cooling fin at the second end, and the second thickness is smaller than the first thickness .

23. The method of Claim 13, wherein the each of the plurality of the cooling fins have a tapered fin body with a fin thickness that decreases from the first end to the second end.

24. The method of Claim 13 , wherein the apparatus is a computing rack, the computing rack being coupled to one end of the heat pipe and the plurality of cooling fins coupled an opposing end of the heat pipe, the computing rack comprising one or more components of a computing system, the heat pipe operable to move heat from the one or more components to the plurality of cooling fins.