Methods for forming a wick
A method of forming an annular wick for a heat pipe is disclosed. The method includes forming a plurality of layers of wick material around an elongate rod; placing the elongate rod and the layers of wick material into a central die opening of an annular die assembly; placing the rod, the layers of wick material, and the annular die assembly into a central clamp opening of a clamp, where the clamp is configured to hold the rod, the layers of wick material, and the annular die assembly together; and heating the rod, the layers of wick material, the annular die assembly, and the clamp to a temperature sufficient to thermally expand the rod toward the central die opening of the annular die assembly to compress the layers of wick material between the rod and the central die opening of the annular die assembly.
1 . A method of forming an annular wick for a heat pipe, the method comprising:
forming a plurality of layers of wick material around an elongate rod;
placing the elongate rod and the plurality of layers of wick material into a central die opening of an annular die assembly;
placing the elongate rod, the plurality of layers of wick material, and the annular die assembly into a central clamp opening of a clamp, wherein the clamp is configured to hold the elongate rod, the plurality of layers of wick material, and the annular die assembly together; and
heating the elongate rod, the plurality of layers of wick material, the annular die assembly, and the clamp to a temperature sufficient to thermally expand the elongate rod toward the central die opening of the annular die assembly to compress the plurality of layers of wick material between the elongate rod and the central die opening of the annular die assembly.
2 . The method of claim 1 , wherein the elongate rod comprises a first material having a first coefficient of thermal expansion, wherein the annular die assembly comprises a second material having a second coefficient of thermal expansion that is less than the first coefficient of thermal expansion.
3 . The method of claim 2 , wherein the clamp comprises a third material having a third coefficient of thermal expansion that is less than the first coefficient of thermal expansion.
4 . The method of claim 1 , wherein the plurality of layers of wick material are compressed between a minimum amount wherein no voids are defined between layers of the plurality of layers of wick material and a maximum amount permitted by the clamp.
5 . The method of claim 1 , wherein the clamp comprises a first clamp portion and a second clamp portion that define the central clamp opening for receiving the elongate rod, the plurality of layers of wick material, and the annular die assembly, the method comprising attaching the first clamp portion and the second clamp portion together to hold the elongate rod, the plurality of layers of wick material, and the annular die assembly together.
6 . The method of claim 5 , wherein attaching the first clamp portion to the second clamp portion comprises mechanically fastening one of the first clamp portion and the second clamp portion to the other of the first clamp portion and the second clamp portion.
7 . The method of claim 1 , wherein the clamp comprises a clamp body and a threaded stud, a first end of the clamp body capturing a first end of the threaded stud, the second end of the threaded stud being threaded to securely hold a second of the clamp body, wherein the clamp securely surrounds the die as the threaded stud draws the first end and the second end of the clamp body together.
8 . The method of claim 1 , wherein the annular die assembly comprises a first die portion defining a first arcuate opening and a second die portion defining a second arcuate opening, wherein the first arcuate opening and the second arcuate opening form the central die opening between the first die portion and the second die portion for receiving the elongate rod and the plurality of layers of wick material.
9 . The method of claim 1 , wherein forming the plurality of layers of wick material around the elongate rod comprises wrapping a sheet of wick material around an outside diameter of the elongate rod.
10 . The method of claim 1 , further comprising wrapping a layer of film around the elongate rod prior to forming the plurality of layers of wick material around the elongate rod.
11 . The method of claim 1 , further comprising coating the elongate rod with a fourth material prior to forming the plurality of layers of wick material around the elongate rod, wherein the fourth material comprises at least one of a ceramic, a refractory alloy, or a metallic.
12 . The method of claim 1 , further comprising coating the central die opening of the annular die assembly with a fifth material comprising at least one of a ceramic, a refractory alloy, or a low thermal expansion alloy.
13 . The method of claim 1 , further comprising:
aligning a plurality of elongate rods to form an extended rod; and
aligning a plurality of annular die assemblies to form an extended annular die assembly,
wherein each end of each of the elongate rods is offset from each end of each of the annular die assemblies to create a stagger.
14 . The method of claim 1 , wherein the plurality of layers of wick material that have been compressed form a first wick, the method further comprising:
joining pairwise the first wick with a second wick by:
inserting a slug into the inside diameters of the first wick and the second wick;
positioning adjacent ends of the first wick and the second wick within the central die opening of the annular die assembly; and
heating the adjacent ends to join the first wick and the second wick.
15 . The method of claim 14 , further comprising:
cutting, before joining, each of the adjacent ends to create an interlocking geometry.
16 . The method of claim 15 , wherein the interlocking geometry comprises a lap joint or a butt joint.
17 . A method of forming an annular wick for a heat pipe, the method comprising:
forming a plurality of layers of wick material around an elongate rod, the elongate rod defining an outside diameter;
placing the elongate rod and the plurality of layers of wick material into a central die opening of an annular die assembly, the central die opening defining an inside diameter;
placing the elongate rod, the plurality of layers of wick material, and the annular die assembly into a central clamp opening of a clamp, wherein the clamp is configured to hold the elongate rod, the plurality of layers of wick material, and the annular die assembly together, wherein an annular gap is defined between the inside diameter of the annular die assembly and the outside diameter of the elongate rod based on the elongate rod and the plurality of layers of wick material being positioned in the central die opening; and
heating the elongate rod, the plurality of layers of wick material, the annular die assembly, and the clamp to thermally expand the elongate rod toward the central die opening of the annular die assembly such that the annular gap shrinks a predetermined amount to compress the plurality of layers of wick material between the elongate rod and the central die opening of the annular die assembly.
18 . The method of claim 17 , wherein the elongate rod comprises a first material having a first coefficient of thermal expansion, wherein the annular die assembly comprises a second material having a second coefficient of thermal expansion that is less than the first coefficient of thermal expansion.
19 . The method of claim 18 , wherein the clamp comprises a third material having a third coefficient of thermal expansion that is less than the first coefficient of thermal expansion.
20 . The method of claim 19 , wherein the annular gap is greater than or equal to a radial thickness of the plurality of layers of wick material formed around the elongate rod prior to heating.
21 . The method of claim 20 , wherein the predetermined amount is between zero and the radial thickness of the plurality of layers of wick material.