Patent Application
20120111542
Generally known heat pipes may include a sealed pipe, or tube, made of a material with a high thermal conductivity such as copper or aluminum. The air may be partially removed from the sealed pipe. A working fluid, or coolant, such as water, may be introduced into the sealed pipe. The heat pipe may further contain a wick, which may serve to exert a capillary pressure on the liquid phase of the working fluid. Without wishing to be bound by the theory, Applicants believe that heat pipes include a heat transfer mechanism that combines the principles of both thermal conductivity and phase transition to efficiently manage the transfer of heat between two solid interfaces.
In one illustrative embodiment, the present disclosure provides a coiled heat pipe. The coiled heat pipe may include an exterior coil and a plurality of interior-perforated coils. The exterior coil and the plurality of interior-perforated coils may be formed from a single aluminum sheet, which may be a 5xxx series aluminum. The exterior coil may house, or otherwise contain, a partial vacuum and a working fluid.
In another illustrative embodiment, the present disclosure provides a method of producing a coiled heat pipe. The method may include providing an aluminum alloy sheet and optionally heat treating the aluminum alloy sheet. A first portion of the aluminum alloy sheet may be perforated to form a perforated end. The perforated end may be coiled about itself to form a plurality of interior-perforated coils, having interior-perforated coil perimeters. The non-perforated end of the aluminum alloy sheet may be coiled about the plurality of interior-perforated coils to form a lap, and an exterior coil having a distal edge and exterior coil perimeters. The aluminum alloy sheet may be optionally etched with a solvent.
For purposes of summarizing the present coiled heat pipe and methods thereof, certain aspects, advantages, and novel features of the present coiled heat pipe and methods thereof have been described herein. It is to be understood that not necessarily all such advantages may be achieved in accordance with any one particular embodiment of the coiled heat pipe and methods thereof. Thus, the invention may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other advantages as may be taught or suggested herein.
These and other embodiments of the present coiled heat pipe and methods thereof will also become readily apparent to those skilled in the art from the following detailed description of the embodiments having reference to the attached drawing figures, the coiled heat pipe and methods thereof not being limited to any particular embodiment(s) disclosed.
For a fuller understanding of the disclosure, reference is made to the following description taken in connection with the accompanying drawing figures, in which:
With reference to
In an embodiment, the single aluminum sheet 115 may have, at a first end, 120, a plurality of interior-perforated coils 110. While the coiled heat pipe 100 may include any number of interior-perforated coils 110 depending on a number of conditions, including without limitation: the size of the coiled heat pipe 100, the required volume of working fluid, and the necessary heat flux from the coiled heat pipe; typically, the coiled heat pipe 100 may include between 2 and 10, alternatively between 2 and 5, interior-perforated coils 110. In an embodiment, the plurality of interior-perforated coils 110 are concentrically coiled about themselves. In an embodiment, the plurality of interior-perforated coils 110 may be spaced apart such that first surfaces, 110a, and second surfaces, 110b, of the interior-perforated coils 110 may both function as wicking surfaces. Without limitation and in an embodiment, the spacing between first surfaces, 110a, and second surfaces 110b, may be a distance ranging from between about an eighth of a sheet thickness, alternatively from about 25 microns, to about a sheet thickness, typically about 250 microns. In a still further embodiment, a plurality of spacers (not shown) may be affixed to, disposed upon, or formed integral with, the first surfaces, 110a, and/or the second surfaces 110b, of the interior-perforated coils 110 to maintain the spacing between first surfaces, 110a, and second surfaces 110b. Without limitation, suitable spacers may include: protrusions, bumpers, or bumps; tabs; deliberate burrs; and the like.
The interior-perforated coils 110 may include a plurality of perforations 125. In an embodiment, the perforations 125 may be evenly distributed, or irregularly distributed, across a first end 120 of the coiled heat pipe 100. In an alternative embodiment, the perforations 125 may each have a diameter ranging from about three times the sheet thickness to about ten times the sheet thickness, alternatively from about 250 microns to about 2,500 microns. In a further embodiment, the perforations 125 have a total area fraction of 5 to 20 percent, based on the total area of the first end 120.
Continuing from, or otherwise extending in a first direction along an axis, X, away from, the first end 120 of the single aluminum sheet 115, may be a lap, or fin, 130. The lap, or fin, 130 may include a sealed lap portion 135 and an overlapped lap portion 140. In an embodiment, the sealed lap portion 135 may be adjacent to, extending from, or integral with, the first end 120, along the axis, X, in the first direction. In an embodiment, the overlapped lap portion 140 may be adjacent to, extending from, or integral with, the sealed lap portion 135, along the axis, X, in the first direction. In an embodiment, preferably at its distal end 145, the overlapped lap portion 140 may be doubled over, folded, overlapped, or otherwise re-directed over itself, and continues along the axis, X, in a second direction, which may be generally parallel to, and opposite of, the first direction.
Continuing from, or otherwise extending in the second direction along the axis, X, away from the overlapped lap portion 140, may be the exterior coil 105. The exterior coil 105 may continue to extend, preferably concentrically, about an outer-most interior-perforated coil 150. In this manner, the plurality of interior-perforated coils 110 may be housed within, disposed within, or otherwise contained by, the exterior coil 105. In an embodiment, outer perimeters of the exterior coil 155a and outer perimeters of the interior-perforated coils 155b may be co-planer, and generally aligned with each other, in a plane that overlays a Y axis, which is perpendicular to the X axis. The outer perimeters of the exterior coil 155a and the outer perimeters of the interior-perforated coils 155b may be sealed by hemming, seam welding, or fish tailing (e.g., squishing a portion of the perimeters 155a, 155b flat and folding the flatted portion over itself).
The exterior coil 105 may continue to extend until a distal end 160 of the exterior coil 105 extends adjacent to, and aligned with, the sealed lap portion 135. In an embodiment, the termination of the distal end 160 may define the termination of the sealed lap portion 135, and the initiation, or beginning, of the overlapped lap portion 140. In an embodiment, the sealed lap portion 135 may include a seal 165, preferably made by one or more welds, or as illustrated in
In an embodiment, the exterior coil 105 may be sealed and may house, or otherwise contain, a partial vacuum (not shown) and a working fluid (not shown). In an embodiment, the partial vacuum may have a pressure ranging from about 0.003 Torr to about 0.1 Torr. The working fluid (not shown) may be any fluid having a sufficient boiling point to readily undergo liquid to gas, and gas to liquid, phase transitions during the intended working conditions of the heat pipe 100. In a preferred embodiment, the working fluid (not shown) may have as high a heat capacity as possible such that the it absorbs as much heat as possible during each phase transition. Without limitation, suitable working fluids (not shown) may include: water, ethanol, acetone; butane, pentanone, sodium, mercury, other organic compounds, and combinations thereof.
The followings are the definitions of the terms used in this application:
As used herein, the term “thermomechanically processing” means the deformation, or heat treatment, of a metal with the intent to change the properties or microstructure of the metal.
As used herein, the term “grain size” means the size of an individual crystal within the metal.
As used herein, the term “grain shape” means the mean shape of an individual crystal within the metal.
As used herein, the term “wicking” means the transport of a fluid through capillary action.
As used herein, the term “grain boundaries” means those regions within the metal where two or more grains abut.
As used herein, the term “continuous etchable phase” means a phase which is susceptible to be etchable by a chemical agent and not into disjoint regions.
With reference to
In step 305, an aluminum alloy is provided. Suitable aluminum alloys may include without limitation: 1xxx series; 2xxx series; 3xxx series; 4xxx series; 5xxx series; 6xxx series; 7xxx series; or 8xxx series aluminum alloy, including aluminum-magnesium alloy having between about 2.5 wt. % to about 12 wt. % magnesium.
In optional step 310, the aluminum alloy may be heat treated to produce a continuous etchable phase on the grain boundaries. In an embodiment, the aluminum alloy may be heated from between about 10 hours to about 10 days, and at a temperature ranging between about 120° C. to about 180° C. The temperature of heating may be variable during the duration of heating or may remain substantially constant throughout the heating step.
In optional step 315, the aluminum alloy may be thermomechanically processed by either deformation, or heat treatment, of a metal with the intent to change the properties or microstructure of the metal to produce grain size and shape suitable for wicking. Suitable mechanical processing techniques may include, without limitation: hot rolling; cold rolling; extrusion; or forging. Suitable thermal processing may include, without limitation: annealing; recrystallization; or recovery. In an embodiment, the aluminum alloy may be heat treated form between about 10 seconds to about 3 hours, and at a temperature ranging between about 280° C. to about 480° C. The temperature of heating treating may be variable during the duration of heating or may remain substantially constant throughout the heating step. In another embodiment, the grain size of the aluminum alloy may range from about 10 microns to about 500 microns.
In step 320, at least a first portion of the aluminum alloy may be perforated to form a perforated end. The perforation may be prepared by any suitable means including, without limitation: precision puncture using a punch; chemical etching; and an embossing roll.
In step 325, the perforated end, formed in step 320, may be coiled about itself to form a plurality of interior-perforated coils, the interior-perforated coils may have interior-perforated coil outer perimeters. With reference to
In step 330, the non-perforated end of the aluminum alloy may be coiled about the plurality of interior-perforated coils in step 330 to form a lap, and an exterior coil having an distal end and exterior coil outer perimeters. With reference to
In an optional step 335, the aluminum alloy may be etched with a solvent that may dissolve the continuous etchable phase on the grain boundaries to produce the metal structure with a grooved wicking surface. In various embodiments, the solvent used may depend on the type of continuous etchable phase present on the aluminum alloy, and may include, without limitation: nitric acid, such as, without limitation nitric acid in a concentration of about 20% to about 70%; or caustic NaOH. In another embodiment, the duration of the etching step may be from about 5 minutes to about 90 minutes, and at a temperature ranging from about 30° C. to about 90° C., alternatively from about 70° C. to about 80° C. The temperature during etching may be variable during the duration of heating or may remain substantially constant throughout the etching step. Optionally, the continuous etchable phase on the grain boundaries may be strained to deform the grain boundaries in the direction of the strain before the etching step. In one embodiment, the straining may be done by rolling.
With reference again to
In step 340, a proximate end 185 of outer perimeters of the exterior coil 155a and outer perimeters of the interior-perforated coils 155b may be sealed. Then, a vacuum may be applied to a distal end 190 of outer perimeters of the exterior coil 155a and outer perimeters of the interior-perforated coils 155b. Then, a working fluid (not shown) may be introduced to the proximate end 185 by insertion through the seal. Following introduction of the working fluid (not shown), the proximate end 185 and the distal end 190 may be sealed. In an embodiment, the seals may be made by any suitable method including crimping, welding, folding, and the like.
In an alternative embodiment, in step 340 the proximate end 185 of outer perimeters of the exterior coil 155a and outer perimeters of the interior-perforated coils 155b may be sealed. A working fluid (not shown) may be introduced though the distal end 190. The working fluid (not shown) may be heated until its vapor pressure exceeds atmospheric pressure. After sufficient time, the vapor pressure of the heated working fluid may force a substantial amount of the air out, and the distal end 190 may be sealed.
While specific embodiments of the coiled heat pipe and methods thereof have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the coiled heat pipe and methods thereof which is to be given the full breadth of the claims to be appended and any and all equivalents thereof.
This non-provisional patent application claims the benefit and priority of U.S. Provisional Patent Application Ser. No. 61/411,687 filed on Nov. 9, 2010.
| Number | Date | Country | |
|---|---|---|---|
| 61411687 | Nov 2010 | US |
