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Publication numberUS3604504 A
Publication typeGrant
Publication dateSep 14, 1971
Filing dateMay 13, 1970
Priority dateMay 13, 1970
Also published asCA945541A1, DE2112054A1
Publication numberUS 3604504 A, US 3604504A, US-A-3604504, US3604504 A, US3604504A
InventorsHess James Lee, Kessler Sebastian William Jr
Original AssigneeRca Corp
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Flexible heat pipe
US 3604504 A
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Description  (OCR text may contain errors)

. United States Patent OTHER REFERENCES Seeley; J. I-I., Combination Cooling System, IBM Technical Disclosure Bulletin, Vol. II, No. 7, 12/1968 ,Primary ExaminerAlbert W. Davis, Jr. Attorney-Glenn I-l. Bruestle ABSTRACT: A heat pipe comprising a flexible sealed envelope and an internal wick structure comprising two sets of cross-members in transverse relation to each other, the crossmembers being transverse to the flexible axis of the envelope. The wick structure may be a cylindrical mesh screen consisting of orthogonal metal wires disposed within a cylindrical metal bellows such that each of the cross wires is at an angle with respect to the flexible axis of the bellows.

PATENTED SEP 1 4 I97! INVENIORS. Sebastian W Kessler, Jr. BYand James L. Hess.

4 q 0 a 4 1 d 440 0 0 0 0 0 0 0 0 0 0 a 0 00000000000000 0000000000 AGENT FLEXIBLE HEAT PIPE BACKGROUND OF THE INVENTION This invention relates to a novel heat pipe and particularly to a flexible heat pipe having increased flexibility.

A prior flexible heat pipe has a sealed envelope comprising a hollow cylindrical bellows which is flexible along its longitudinal axis. Such a heat pipe is disclosed by G. Y. Eastman in The Heat Pipe -A Progress Report, Proceedings of Fourth lmersociety Energy Conservation Engineering Conference, Sept. l969. Disposed within the envelope is a flexible wick structure, which is saturated by a suitable working fluid. Usually, the wick structure comprises a porous mesh screen consisting of two orthogonal sets of interwoven cross wires. The screen in wound into a cylinder and then inserted within the bellows such that one set of cross wires is parallel to the longitudinal axis of the bellows.

Wick structures made in this manner tend to be very stiff along the desired axis of heat pipe flexibility. This is because the wires which are parallel to the longitudinal axis of the bellows cannot readily change their lengths when the heat pipe is flexed or bent. Thus, prior heat pipes have had poor flexibility. Also, the bending of such heat pipes has often resulted in mechanical failure of the wick structures, e.g., broken cross wires.

SUMMARY OF THE INVENTION The novel heat pipe comprises a flexible sealed envelope having a longitudinal axis and an internal wick structure comprising a plurality of first crossmembers in transverse relation to a plurality of second crossmembers. Both the first and the second crossmembers are transverse to the flexible axis. The wick structure is saturated by a suitable working fluid.

By being transverse relative to one another and transverse to the flexible axis, the first and second crossmembers can readily change their effective lengths, in bending regions of the wick structure, when the heat pipe is bent. Thus, the novel heat pipe is more flexible than are prior heat pipes. Also, the problems of mechanical failure of the wick structures are greatly reduced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal view, partly in axial section, of an example of the novel heat pipe.

FIG. 2 is a sectional view, along the line 2-2, of the heat pipe of FIG. 1.

FIG. 3 is an enlarged perspective view of a portion of the wick structure of FIG. 1, and

FIG. 4 illustrates a method of shaping the wick structure of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the example shown in FIGS. 1 and 2, the novel heat pipe comprises an envelope 11 consisting of a long cylindrical stainless steel bellows 13 having flexibility along its longitudinal axis 14. The bellows 13 is sealed at each of its opposite ends to a cup-shaped end member 15 made of copper. Disposed within the envelope 11 and adjacent the inner walls thereof is a cylindrical wick structure 17 made of stainless steel wire mesh. The envelope 11 also contains a quantity of acetone working fluid sufficient to saturate the wick structure 17.

The wick structure 17, shown in detail in FIG. 3, comprises a plurality of first cross wires 19 orthogonal to and interwoven with a plurality of second cross wires 21. The cross wires 19 and 21 are not bonded at their cross over points, so that the wires are slidable with respect to each other. The wick structure 17 is disposed within the envelope 11 such that each of the cross wires 19 and 21 is at an angle of about 45 with respect to the longitudinal axis 14 of the bellows 13. Thus, when the heat pipe is flexed or bent along the flexible axis 14,

the cross wires 19 and 21 can slide with respect to each other and thereby change their effective lengths in the direction of the axis 14, in the bending regions of the wick structure 17.

FIG. 4 illustrates a method of shaping the wick structure 17. The starting structure is a square mesh screen comprising a plurality of first stainless steel cross wires 19' orthogonal to and interwoven with a plurality of second stainless steel cross wires 21'. The cross wires 19' are parallel to two parallel sides of the square, and the cross wires 21' are parallel to the other two parallel sides of the soyare. Each side of the square has a length equal to (a+b)/ /2, where a" is the length of the wick structure 17 and b is the rolled-out width of the wick structure 17. That is, b" is equal to n1rd," where (1" is the effective diameter of the wick structure 17 and n" is the number of wraps of the wire mesh constituting the wick structure 17. The square mesh screen is first shaped into a rectangular mesh screen having two parallel sides of length 11" and two parallel sides of length b, by suitable cutting or slicing the former at 45 angles as indicated in FIG. 4. The rectangular mesh screen is then rolled or wound about its longitudinal axis to effect the cylindrical wick structure 17. Thus, the cross wires 19' and 21 of the rectangular mesh screen become the cross wires 19 and 21, respectively, of the wick structure 17.

The heat pipe may be assembled by the following procedure. The wick structure 17 is inserted within the open bellows 13. One end of the bellows 13 is welded to the open end of one of the end members 15. The other end of the bellows 13 is welded to the open end of the other end member 15, which has an exhaust tabulation (not shown). The exhaust tubulation is connected to a suitable vacuum exhaust system and also to a source of acetone working fluid, by valve means (none of which is shown). The assembled heat pipe is evacuated and then filled with the acetone working fluid. The completed heat pipe is sealed by pinching off the exhaust tubulation.

A heat pipe as described above was constructed to conduct 20 watts at 40 C, over a distance of 18 inches. The wick structure had an effective diameter of about 0.5 inch and comprised 2 wraps of l20 l20 stainless steel wire mesh screen. The flexibility of the heat pipe along its longitudinal axis was grater than that previously obtainable, and the heat pipe operated successfully in a space environment for more than hours.

GENERAL CONSIDERATIONS There are various configurations embodying the invention. The bellows may be other than cylindrical in shape; for example, it may have a substantially square, rectangular, or oval cross section. Also, the cross section may be nonuniform over its length. Where acetone is employed as the working fluid, the bellows may be made of copper, copper alloy, or ferrous alloy, instead of stainless steel. Where another working fluid, such as water, is employed, the bellows may be made of any of various materials not corroded thereby.

The wick structure may also be other than cylindrical in shape; and it may be spaced from, rather than adjacent to, the inner walls of the heat pipe envelope. Depending upon the working fluid employed, the wick structure may be made of a material other than stainless steel, such as copper, copper alloy, or ferrous alloy. The crossmembers comprising the wick structure may be strips, rather than wires, made of the suitable material, and the sizes and spacings of the crossmembers may vary, instead of remaining constant. Also, the number of first crossmembers may be different from, rather than the same as, the number of second crossmembers.

The two sets of crossmembers may be other than orthogonal (90) to each other; in general, they may be in transverse relation. Experiments have shown that heat pipe flexibility is near maximum when the angle between the two sets of crossmembers is in the range from about 30 (9060) to about (90+60). Also, the wick structure need not be disposed such that the crossmembers are each at an angle of 45 with respect to the longitudinal axis of the bellows. Each of the crossmembers need merely be transverse to the flexible axis.

The crossmembers may be interconnected (e.g., interlinked), rather than interwoven, so as to be slidable with respect to one another. However, the crossmembers need not be slidable with respect to one another. If they are not too stiff, the crossmembers may be bonded (e.g., spot welded) at their crossover points. The transverse relationship of the two sets of crossmembers to each other and also to the flexible axis will permit the bonded crossmembers to change their effective axial lengths in the bending regions of the wick structure. For example, a square capillary pore defined by four bonded cross wires may be stretched or compressed into a diamond-shaped opening by suitably bending the wick structure.

While the wick structure may be guided by the walls of the bellows, it is not supported thereby as a coating would be. This self-supporting quality is necessary to leave the crossmembers free to adjust their effective lengths when the heat pipe is flexed or bent. However, the wick structure may be attached to one or both of the end members. Depending upon the heat conductivity and other requirements thereof, the end members may be other than cup-shaped and made of a material other than copper.

What is claimed is:

l. A heat pipe comprising:

a. a flexible sealed envelope having a longitudinal axis;

b. a wick structure within said envelope, comprising a plurality of first crossmembers in transverse relation to a plurality of second crossmembers, said first crossmembers and said second crossmembers each being transverse to said axis; and

c. a working fluid saturating said wick structure within said envelope.

2. The heat pipe of claim 1, wherein said first crossmembers are in slidable relation to said second crossmembers.

3. The heat pipe of claim 1, wherein said first crossmembers are bonded to said second crossmembers.

4. The heat pipe of claim 1, wherein the angle between each of said first crossmembers and each of said second crossmembers is in the range from about 30 to about 5. A heat pipe comprising:

a. a cylindrical flexible metal bellows;

b. means sealing said bellows at the opposite ends thereof;

c. a cylindrical wick structure within said bellows, comprising a plurality of first metal crossmembers in slidable transverse relation to a plurality of second metal crossmembers, said first crossmembers and said second crossmembers each being transverse to the longitudinal axis of said bellows; and

d. a working fluid saturating said wick structure within said bellows.

6. The heat pipe of claim 5, wherein said first crossmembers are interwoven with said second crossmembers.

7. The heat pipe of claim 5, wherein each of said first crossmembers is orthogonal to each of said second crossmembers.

8. The heat pipe of claim 5, wherein each of said first and second crossmembers is at an angle of about 45 with respect to said longitudinal axis.

9. The heat pipe of claim 5, wherein said first crossmembers are substantially equally spaced constant-sized wires and said second crossmembers are substantially equally spaced constant-sized wires.

10. The heat pipe of claim 9, wherein the spacing and size of said first cross wires are substantially equal to the spacing and size, respectively, of said second cross wires.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US3347309 *Jun 16, 1966Oct 17, 1967Webb James ESelf-adjusting, multisegment, deployable, natural circulation radiator
Non-Patent Citations
Reference
1 *Seeley; J. H., Combination Cooling System, IBM Technical Disclosure Bulletin, Vol. II, No. 7, 12/1968
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3797086 *Nov 12, 1972Mar 19, 1974Philips CorpMethod of closing off a heat pipe
US3854454 *Nov 1, 1973Dec 17, 1974Therma Electron CorpHeat pipe water heater
US4003427 *Oct 15, 1974Jan 18, 1977Grumman Aerospace CorporationHeat pipe fabrication
US4094357 *Apr 9, 1976Jun 13, 1978Kenneth C. McCordHeat transfer blanket
US4194559 *Nov 1, 1978Mar 25, 1980Thermacore, Inc.Freeze accommodating heat pipe
US4240500 *Aug 6, 1979Dec 23, 1980Kabel- Und Metallwerke Gutehoffnungshuette AgHeat exchange apparatus
US4279294 *Dec 22, 1978Jul 21, 1981United Technologies CorporationHeat pipe bag system
US4339929 *Apr 10, 1981Jul 20, 1982United Technologies CorporationHeat pipe bag system
US4565243 *Nov 24, 1982Jan 21, 1986Thermacore, Inc.Hybrid heat pipe
US4993481 *Sep 26, 1989Feb 19, 1991The Agency Of Industrial Science And TechnologyThermal storage unit
US5720338 *Mar 2, 1995Feb 24, 1998Aavid Laboratories, Inc.Two-phase thermal bag component cooler
US5944093 *Dec 30, 1997Aug 31, 1999Intel CorporationPickup chuck with an integral heat pipe
US6105662 *Mar 27, 1997Aug 22, 2000Fujitsu LimitedCooling system for electronic packages
US6152213 *Jan 6, 2000Nov 28, 2000Fujitsu LimitedCooling system for electronic packages
US6530419Jun 29, 2000Mar 11, 2003Fujitsu LimitedCooling system for electronic packages
US7631686 *Aug 25, 2005Dec 15, 2009Fu Zhun Precision Industry (Shen Zhen) Co., Ltd.Liquid cooling device
US7647961 *Oct 24, 2005Jan 19, 2010Thermal Corp.Heat pipe with axial and lateral flexibility
US7922463 *Oct 21, 2005Apr 12, 2011Lg Electronics Inc.Linear compressor
US8069907Sep 13, 2007Dec 6, 20113M Innovative Properties CompanyFlexible heat pipe
US8230907 *Jan 18, 2010Jul 31, 2012Thermal Corp.Heat pipe with axial and lateral flexibility
US8587944Apr 1, 2009Nov 19, 2013Harris CorporationMulti-layer mesh wicks for heat pipes
US20110088874 *Oct 20, 2009Apr 21, 2011Meyer Iv George AnthonyHeat pipe with a flexible structure
US20110220328 *Mar 9, 2010Sep 15, 2011Kunshan Jue-Chung Electronics Co., Ltd.Flexible heat pipe and manufacturing method thereof
US20120048518 *Sep 19, 2010Mar 1, 2012Foxconn Technology Co., Ltd.Flat heat pipe with internal supporting element
DE3240502A1 *Oct 30, 1982May 3, 1984Licentia GmbhBoiling/cooling container for power-electronics components
Classifications
U.S. Classification165/46, 165/104.26
International ClassificationF28D15/04
Cooperative ClassificationF28D15/046
European ClassificationF28D15/04B