US20190033007A1 - Carbon nanotube and graphene aerogel heat pipe wick - Google Patents
Carbon nanotube and graphene aerogel heat pipe wick Download PDFInfo
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- US20190033007A1 US20190033007A1 US16/067,768 US201616067768A US2019033007A1 US 20190033007 A1 US20190033007 A1 US 20190033007A1 US 201616067768 A US201616067768 A US 201616067768A US 2019033007 A1 US2019033007 A1 US 2019033007A1
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- heat pipe
- aerogel
- wick
- graphene
- heat
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F28—HEAT EXCHANGE IN GENERAL
- F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
- F28D15/00—Heat-exchange apparatus with the intermediate heat-transfer medium in closed tubes passing into or through the conduit walls ; Heat-exchange apparatus employing intermediate heat-transfer medium or bodies
- F28D15/02—Heat-exchange apparatus with the intermediate heat-transfer medium in closed tubes passing into or through the conduit walls ; Heat-exchange apparatus employing intermediate heat-transfer medium or bodies in which the medium condenses and evaporates, e.g. heat pipes
- F28D15/04—Heat-exchange apparatus with the intermediate heat-transfer medium in closed tubes passing into or through the conduit walls ; Heat-exchange apparatus employing intermediate heat-transfer medium or bodies in which the medium condenses and evaporates, e.g. heat pipes with tubes having a capillary structure
- F28D15/046—Heat-exchange apparatus with the intermediate heat-transfer medium in closed tubes passing into or through the conduit walls ; Heat-exchange apparatus employing intermediate heat-transfer medium or bodies in which the medium condenses and evaporates, e.g. heat pipes with tubes having a capillary structure characterised by the material or the construction of the capillary structure
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F28—HEAT EXCHANGE IN GENERAL
- F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
- F28D15/00—Heat-exchange apparatus with the intermediate heat-transfer medium in closed tubes passing into or through the conduit walls ; Heat-exchange apparatus employing intermediate heat-transfer medium or bodies
- F28D15/02—Heat-exchange apparatus with the intermediate heat-transfer medium in closed tubes passing into or through the conduit walls ; Heat-exchange apparatus employing intermediate heat-transfer medium or bodies in which the medium condenses and evaporates, e.g. heat pipes
- F28D15/0283—Means for filling or sealing heat pipes
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F28—HEAT EXCHANGE IN GENERAL
- F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
- F28F21/00—Constructions of heat-exchange apparatus characterised by the selection of particular materials
- F28F21/02—Constructions of heat-exchange apparatus characterised by the selection of particular materials of carbon, e.g. graphite
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L23/00—Details of semiconductor or other solid state devices
- H01L23/34—Arrangements for cooling, heating, ventilating or temperature compensation ; Temperature sensing arrangements
- H01L23/36—Selection of materials, or shaping, to facilitate cooling or heating, e.g. heatsinks
- H01L23/373—Cooling facilitated by selection of materials for the device or materials for thermal expansion adaptation, e.g. carbon
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L23/00—Details of semiconductor or other solid state devices
- H01L23/34—Arrangements for cooling, heating, ventilating or temperature compensation ; Temperature sensing arrangements
- H01L23/46—Arrangements for cooling, heating, ventilating or temperature compensation ; Temperature sensing arrangements involving the transfer of heat by flowing fluids
- H01L23/473—Arrangements for cooling, heating, ventilating or temperature compensation ; Temperature sensing arrangements involving the transfer of heat by flowing fluids by flowing liquids
Definitions
- FIG. 3A is a schematic representation of a portion of the wick of FIG. 2 that includes a first combination of carbon nanotube aerogel and graphene in accordance with an example of the present disclosure.
- FIG. 3C is a schematic representation of a portion of the wick of FIG. 2 that includes a third combination of carbon nanotube aerogel and graphene in accordance with an example of the present disclosure.
- FIG. 4 is a flowchart in accordance with an example of the present disclosure of a method of making a heat pipe.
- the heat pipe has a wick that is formed, at least in part, of carbon nanotubes (CNTs) and graphene in aerogel form.
- CNTs carbon nanotubes
- a heat pipe 100 includes a sealed casing 110 , a wick 120 disposed on the interior walls of the casing 110 , and a cavity 130 within the heat pipe 100 which is at least partially filled with a working fluid 140 .
- the working fluid 140 is disposed at least partly within the cavity 130 .
- the working fluid 140 is a saturated fluid.
- the working fluid 140 exists in both a liquid form and a vapor form over the range of operating temperatures of the heat pipe 100 .
- the vapor form of the working fluid 140 is in the cavity 130 , while the liquid form of the working fluid is in the wick 120 .
- the working fluid 140 may be water, alcohol, ammonia, a solvent, or another fluid. Some other suitable fluids include methoxy-nonafluorobutane (C 4 F 9 OCH 3 ), acetone, alcohol, heptane, and pentane.
- the working fluid 140 may also include CNT aerogel in suspension. The type of working fluid 140 may be chosen based on the operating temperature range intended for the heat pipe 100 .
- the wick 120 is a porous structure disposed on the interior walls of the casing 110 .
- the interior surface of the wick 120 defines the cavity 130 .
- the wick 120 exerts a capillary force on the liquid form of the working fluid 140 which comes into contact with the wick 120 . This capillary force tends to draw the liquid working fluid 140 from the cavity 130 into the wick 120 , within which it is absorbed.
- the wick 120 includes carbon nanotubes and graphene in aerogel form. The structure and composition of the wick 120 is discussed subsequently in greater detail with reference to FIGS. 2 and 3A-3C .
- the condensed liquid is drawn by capillary action from the cavity 130 into the wick 120 through pores therein. Capillary action within the wick 120 further causes the liquid to migrate from the cool end 104 back to the hot end 102 , where it fills the voids in the wick 120 left by evaporation at the hot end 102 .
- the cycle of evaporation and condensation continuously repeats while a temperature difference exists between the first end 102 and second end 104 of the heat pipe 100 .
- a tube of a heat pipe has a tubular cross-section 200 .
- a wick 220 is disposed on the interior walls of a casing 210 having a diameter 212 .
- the casing 210 is the casing 110 ( FIG. 1 )
- the wick 220 is the wick 120 ( FIG. 1 ).
- the interior of the casing has a diameter 212 .
- the diameter 212 is in the range of 0.3 to 3 millimeters.
- the wick 220 has a minimum dimension 222 in the range of 0.2 to 0.3 millimeters, and a maximum dimension 224 in the range of 0.4 to 1.1 millimeters.
- a wick aerogel that includes both CNT and graphene provides improved heat transfer over a wick aerogel of CNT alone.
- the aerogel does not include graphene, there can be a suboptimal number of contact points between and among the various carbon nanotubes, reducing heat transfer effectiveness.
- an aerogel using CNT alone can have a maximum thermal conductivity of about 2,000 W/mK at room temperature.
- the maximum thermal conductivity of the aerogel can be increased to about 3,000 W/mK at room temperature.
- This higher thermal conductivity provides increased heat transfer capability for a heat pipe having a wick using CNT plus graphene aerogel. This increased heat transfer capability can reduce the temperature at the hot end of the heat pipe by 10% to 15% as compared to heat pipes having other wick types.
- the proportion of graphene to CNT in the aerogel 350 has been increased by increasing the amount of graphene
- the proportion of graphene to CNT in the aerogel can be increased by decreasing the amount of carbon nanotubes in the aerogel.
- the amount of CNT, graphene, or both in the aerogel can be adjusted so as to produce an aerogel having a thermal conductivity in the range of about 1 to about 3,000 W/mK at room temperature.
- a method 400 begins at 410 by applying a carbon nanotube and graphene aerogel coating to interior walls of a heat pipe tube.
- the applying 410 includes stretching, cutting, and cleaning 412 the tube.
- the tube (casing) material may be stretched so as to form a tube with the desired tube diameter and casing thickness. After the stretching, the tube may be cut to the desired length of the heat pipe.
- the tube is then cleaned. In one example, the tube is given an acid wash, washed in ionized water, washed in a weak alkaline solution, again washed in ionized water, and dried.
- one end of the tube is then sealed. In some examples, the sealing is performed by squeezing the tube end and welding it closed. Other methods of stretching, cutting, cleaning, and sealing may be employed.
- the applying 410 further includes applying 416 carbon nanotube and graphene aerogel in sol-gel form to the interior walls of the heat pipe tube.
- the applying 416 further includes spraying 418 the sol-gel through a nozzle arrangement which corresponds to the cross-sectional shape of the wick structure.
- the nozzle arrangement may include a set of orifices through which the sol-gel is ejected into the tube. The orifices may define the grooves or fluting of the wick cross-section.
- the applied coating is sintered to form the heat pipe wick.
- the sintering is performed at 500 to 650 degrees C. The sintering removes the solvent from the sol-gel solution and solidifies the aerogel on the interior walls of the tube. The sintering forms a good chemical bond of the carbon nanostructures within the aerogel to form a ceramic-like structure which can exert high capillary force on working fluid which contacts it.
- the heat pipe is at least partially filled with the working fluid.
- an end of the tube through which the working fluid was injected is sealed.
- the heat pipe, wick, aerogel, and methods provided by the present disclosure represent a significant advance in the art.
- the lifetime of components such as LCD panels, LEDs, CPUs and similar processors, and batteries can be extended, and the throughput and power efficiency of devices employing them can be increased.
- the risk of battery explosion in such devices can also be reduced.
- the disclosed heat pipes can find wide applicability in electronic devices such as for example, notebook computers, tablet computers, smart phones, televisions, and more.
- blocks in diagrams or numbers should not be construed as operations that proceed in a particular order. Additional blocks/operations may be added, some blocks/operations removed, or the order of the blocks/operations altered and still be within the scope of the disclosed examples. Further, methods or operations discussed within different figures can be added to or exchanged with methods or operations in other figures. Further yet, specific numerical data values (such as specific quantities, numbers, categories, etc.) or other specific information should be interpreted as illustrative for discussing the examples. Such specific information is not provided to limit examples. The disclosure is not limited to the above-described implementations, but instead is defined by the appended claims in light of their full scope of equivalents.
Abstract
Description
- Devices and systems often generate heat during their operation. Such devices and systems include, among many others, computer systems and other electrical devices. Removing excess heat can improve performance and/or minimize or eliminate physical damage. One device that can remove such heat is a heat pipe. The heat pipe is connected at one end to a thermally-conductive heat source, and at the other end to a lower-temperature thermally-conducted element such as, for example, a heat sink. In operation, the heat pipe transports the heat from the higher-temperature end to the lower-temperature element, thus reducing the temperature at the heat source. As systems and devices which generate more heat are developed and employed, it is advantageous to likewise improve the heat transfer capability of heat pipes so as to keep the temperature within the systems and devices and/or at their “hot spots” to a safe operational level.
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FIG. 1 is a schematic representation of a heat pipe in accordance with an example of the present disclosure. -
FIG. 2 is a schematic representation of a wick in accordance with an example of the present disclosure usable with the heat pipe ofFIG. 1 . -
FIG. 3A is a schematic representation of a portion of the wick ofFIG. 2 that includes a first combination of carbon nanotube aerogel and graphene in accordance with an example of the present disclosure. -
FIG. 3B is a schematic representation of a portion of the wick ofFIG. 2 that includes a second combination of carbon nanotube aerogel and graphene in accordance with an example of the present disclosure. -
FIG. 3C is a schematic representation of a portion of the wick ofFIG. 2 that includes a third combination of carbon nanotube aerogel and graphene in accordance with an example of the present disclosure. -
FIG. 4 is a flowchart in accordance with an example of the present disclosure of a method of making a heat pipe. - Referring now to the drawings, there is illustrated an example of a heat pipe which provides improved thermal conductivity, and improved heat transfer (heat dissipation, or latent heat exchange) performance. The heat pipe has a wick that is formed, at least in part, of carbon nanotubes (CNTs) and graphene in aerogel form.
- Considering now a heat pipe, and with reference to
FIG. 1 , aheat pipe 100 includes a sealedcasing 110, awick 120 disposed on the interior walls of thecasing 110, and acavity 130 within theheat pipe 100 which is at least partially filled with a workingfluid 140. - The
casing 110 is a thermally conductive material. In various examples, thecasing 110 is copper, aluminum, stainless steel, or another metal. Thecasing 110 is of a material which is compatible with the workingfluid 140, in order to prevent or inhibit corrosion, generation of non-condensable gases, and other effects which could reduce the useful lifetime of theheat pipe 100 if the casing material were incompatible with the workingfluid 140. In some examples, thecasing 110 is tubular with a cylindrical or elliptical cross-section, but thecasing 110 may alternatively be of a different shape. Thecasing 110 encloses thewick 120,cavity 130, and workingfluid 140, and defines the size of theheat pipe 100. In one example, thecasing 110 has alength 112 in the range of 80 to 450 millimeters, and amaximum diameter 114 in the range of 0.3 to 3 millimeters. - The working
fluid 140 is disposed at least partly within thecavity 130. In examples, the workingfluid 140 is a saturated fluid. In examples, the workingfluid 140 exists in both a liquid form and a vapor form over the range of operating temperatures of theheat pipe 100. In some examples, the vapor form of theworking fluid 140 is in thecavity 130, while the liquid form of the working fluid is in thewick 120. The workingfluid 140 may be water, alcohol, ammonia, a solvent, or another fluid. Some other suitable fluids include methoxy-nonafluorobutane (C4F9OCH3), acetone, alcohol, heptane, and pentane. The workingfluid 140 may also include CNT aerogel in suspension. The type of workingfluid 140 may be chosen based on the operating temperature range intended for theheat pipe 100. - The
wick 120 is a porous structure disposed on the interior walls of thecasing 110. The interior surface of thewick 120 defines thecavity 130. Thewick 120 exerts a capillary force on the liquid form of the workingfluid 140 which comes into contact with thewick 120. This capillary force tends to draw the liquid workingfluid 140 from thecavity 130 into thewick 120, within which it is absorbed. Thewick 120 includes carbon nanotubes and graphene in aerogel form. The structure and composition of thewick 120 is discussed subsequently in greater detail with reference toFIGS. 2 and 3A-3C . - In operation, a
first end 102 of thecasing 110 of theheat pipe 100 is thermally coupled to a heat source (not shown). In some examples, the heat source is an electronic component such as a CPU which generates a significant amount of heat during operation, and thefirst end 102 of thecasing 110 of theheat pipe 100 contacts a thermally conductive surface of the component. The heat source is hotter than the temperature at an oppositesecond end 104 of theheat pipe 100. Thecasing 110 may be connected at thesecond end 104 to a thermally conductive element such as a heat sink (not shown) that can conduct heat away from thesecond end 104 and dissipate it into the environment. - The
heat pipe 100 transfers heat from the higher temperature firstend 102 to the lower temperaturesecond end 104 via evaporative cooling. This involves a two-phase transition of the workingfluid 140. As heat is conducted from the heat source into thefirst end 102, the workingfluid 140 at the first end evaporates from its liquid form (indicated inFIG. 1 by solid arrows) into its vapor form (indicated inFIG. 1 by outlined arrows). The latent heat (thermal energy) absorbed at thefirst end 102 during evaporation of the workingfluid 104 lowers the temperature at thehot end 102. As a result of the evaporation, a pressure gradient occurs in thecavity 130—the vapor pressure at thehot end 102 is higher than the vapor pressure at thecool end 104. This vapor pressure gradient causes the vapor to rapidly migrate from thehot end 102 to thecool end 104. At thecool end 104, the vapor condenses into liquid form, releasing the latent heat (thermal energy). This thermal energy released during condensation is conducted away from thecool end 104 by the heat sink in contact with thecool end 104. - At the
cool end 104, the condensed liquid is drawn by capillary action from thecavity 130 into thewick 120 through pores therein. Capillary action within thewick 120 further causes the liquid to migrate from thecool end 104 back to thehot end 102, where it fills the voids in thewick 120 left by evaporation at thehot end 102. The cycle of evaporation and condensation continuously repeats while a temperature difference exists between thefirst end 102 andsecond end 104 of theheat pipe 100. - In one example, the working
fluid 140 fills thecavity 130 and saturates thewick 120. In other examples, lesser amounts of the workingfluid 140 are used, and thecavity 130 may not be completely filled. In some examples, the quantity of workingfluid 140 is determined by various design parameters of theheat pipe 100, such as for example the thickness of thewick 120 and the heat dissipation requirements of the environment in which theheat pipe 100 is expected to be deployed. - Considering now a heat pipe wick in greater detail, and with reference to
FIG. 2 , in one example a tube of a heat pipe has atubular cross-section 200. Awick 220 is disposed on the interior walls of acasing 210 having adiameter 212. In some examples, thecasing 210 is the casing 110 (FIG. 1 ), and thewick 220 is the wick 120 (FIG. 1 ). - In some examples, the
wick 220 has a grooved orfluted profile 225 along its length on the interior walls of thecasing 210. Such a profile increases the surface area of thewick 220 which is exposed to thecavity 230. This increases the efficiency of working fluid transfer between thecavity 230 andwick 210, and thus increases the heat transfer capability of the heat pipe. However, in another example thewick 220 is not grooved or fluted. - The interior of the casing has a
diameter 212. In one example, thediameter 212 is in the range of 0.3 to 3 millimeters. Thewick 220 has aminimum dimension 222 in the range of 0.2 to 0.3 millimeters, and amaximum dimension 224 in the range of 0.4 to 1.1 millimeters. - The
wick 220 includes CNTs and graphene, in aerogel form. A carbon nanotube is an arrangement of carbon molecules which has a cylindrical three-dimensional nanostructure. A carbon nanotube may be a single-walled nanotube 240. The walls are single-atom sheets of carbon rolled into cylinders around an axis. Another carbon nanotube may be a multiple-walled nanotube (not shown), with the various walls disposed concentrically around the axis. In one example, thecarbon nanotube 240 has alength 242 in the range of about 1 to 3 micrometers, and awidest diameter 244 in the range of about 8 to 12 nanometers. In one example, the aspect ratio (diameter to thickness) is between 50 and 5000. Carbon nanotubes have high thermal conductivity along their length, in one example about 3500 W/mK (watts per meter-degree Kelvin) at room temperature. In some examples, the carbon nanotube is curved into the shape of an arc, rather than being straight. - Graphene is a layered arrangement of carbon molecules having a two-dimensional hexagonal lattice nanostructure one atom thick. Graphene may have a single such layer, or multiple layers stacked together. In one example, the thickness of a stack of
graphene 250 is between about 5 and 100 nanometers, and thelength 252 andwidth 254 is between 0.1 to 5 micrometers. In one example, the aspect ratio (length to thickness, or width to thickness) is between 100 and 4500. Graphene has high thermal conductivity, in one example between about 4,840 and 5,300 W/mK at room temperature. While thegraphene sheet 250 is illustrated as rectangular, in other examples it can have an arbitrary shape. Also, while thegraphene sheet 250 is illustrated as flat, in other examples the sheet can be bent or curved such that the graphene sheet has a three-dimensional shape. - Aerogel is a low density, lightweight, high porosity, and high surface area material. In some examples, it is formed using a sol-gel process, by removing a liquid component of a gel and replacing it by a gas, in a manner which prevents the solid matrix from collapsing as the liquid is removed. The resulting aerogel is a solid which has extremely low density. An aerogel formed at least in part of CNT and graphene includes nanometer-scale particles of the CNT and graphene which are bonded together. The aerogel has a random arrangement of the various CNT and graphene nanostructures. Individual ones of CNT nanostructures, and individual ones of the graphene nanostructures, may be of different sizes and shapes from others.
- In various examples, the aerogel includes 0.1% to 30% graphene, by weight. In various examples, the density of the CNT and graphene aerogel is between 0.03 and 0.5 g/cm3 (grams per cubic centimeter). In various examples, the porosity of CNT and graphene aerogel, defined as the ratio of void to material, is between 5% and 90%. In various examples, the pore diameter of the aerogel is between 3 and 50 nanometers. In various examples, the surface area of the aerogel is between 250 and 300 m2/g (square meters per gram). For a
wick 220 or wick 120 (FIG. 1 ) formed of CNT and graphene aerogel, these characteristics collectively determine, at least in part, the capillary force that the wick exerts on the working fluid 140 (FIG. 1 ), which in turn determines, at least in part, the heat transfer performance of the heat pipe 100 (FIG. 1 ). The higher the porosity and/or the greater the surface area of the aerogel in the wick, the higher the capillary force exerted on the working fluid to draw liquid into the wick at the cool end 104 (FIG. 1 ) of the heat pipe, and transport it through the wick along the length of the heat pipe to the hot end 102 (FIG. 1 ); and the more rapidly this liquid transport occurs. Thus the high capillary force exerted by a CNT and graphene aerogel wick increases the vapor conversion cycle rate performance of the heat pipe. - The capillary force exerted by the wick is one factor that influences the heat transfer performance of the heat pipe. Another factor is the thermal conductivity of the wick. A wick formed of CNT and graphene aerogel advantageously improves the heat transfer performance of the heat pipe. Considering now in greater detail the aerogel of a heat pipe wick, and with reference to
FIGS. 3A-30 , the percentage by weight of the graphene in the aerogel determines, at least in part, the thermal conductivity of the wick, and in turn the heat transfer performance of the heat pipe.FIGS. 3A-30 each schematically illustrate a portion (310, 330, 350 respectively) of the aerogel of a heat pipe wick, magnified to depict the CNT and graphene nanostructures in the aerogel.Carbon nanotubes 302 and/orgraphene sheets 304 are depicted in theaerogel portions individual carbon nanotube 302 is depicted as a linear rod, and eachindividual graphene sheet 304 as a planar sheet. In addition, and also for clarity of illustration, representative ones of thecarbon nanotubes 302 andgraphene sheets 304 are labeled with a reference designator. - Each
aerogel portion FIG. 3A ) has a low proportion of graphene to CNT. For example, the aerogel may have about 0.1% graphene by weight and, as a consequence, nographene sheets 304 appear in theportion 310. Theindividual CNTs 302 are dispersed in the aerogel. Theaerogel 310 has CNT-to-CNT contact points 315 between some pairs of theCNTs 302. Each CNT-to-CNT contact point 315 is indicated by a dashed circle; for clarity of illustration, however, representative ones of the dashed circles are labeled with a reference designator. Becausecarbon nanotubes 302 are highly thermally conductive, heat is easily transferred between the contactingCNTs 302 at the contact points 315. - Aerogel portion 330 (
FIG. 3B ) has a moderate proportion of graphene to CNT. For example, the aerogel may have about 15% graphene by weight.Graphene sheets 304 are dispersed in the aerogel. Twographene sheets 304 are illustrated in theportion 330, which has substantially the same number and arrangement ofCNTs 302, and CNT-to-CNT contact points 315, as the aerogel 310 (however, for clarity of illustration, the contact points 315 are not identified inFIG. 3B ). Various ones of theCNTs 302 contact at least onegraphene sheet 304 at CNT-to-graphene contact points 335. Each CNT-to-graphene contact point 335 is indicated by a dashed circle; however, for clarity of illustration, representative ones of the dashed circle are labeled with a reference designator. Becausegraphene 304 is highly thermally conductive, heat is easily transferred between aCNT 302 and agraphene sheet 304 at contact points 335. Theaerogel portion 330 has higher thermal conductivity than theaerogel portion 310, due to the CNT-to-graphene contact points 335 present in theaerogel 330, but not in theaerogel 310. Theseadditional contact points 335 allow heat to be more readily transferred from the hot end to the cool end of a heat pipe having a wick of theaerogel 330 than with a wick of theaerogel 310. - Aerogel portion 350 (
FIG. 3C ) has a high proportion of graphene to CNT. For example, the aerogel may have about 30% graphene by weight. Fourgraphene sheets 304 are illustrated in theportion 350, which has substantially the same number and arrangement ofCNTs 302, and CNT-to-CNT contact points 315, as theaerogel aerogel 350 also has substantially the same number and arrangement of CNT-to-graphene contact points 335 as the aerogel 330 (however, thesecontact points 335 are not identified inFIG. 3C for clarity of illustration). In addition, various ones of theCNTs 302 contact at least onegraphene sheet 304 at additional CNT-to-graphene contact points 355. Eachcontact point 355 is indicated by a dashed circle; however, for clarity of illustration, representative ones of the dashed circle are labeled with a reference designator. Theaerogel portion 350 has higher thermal conductivity than theaerogel portion 330, because of the additional CNT-to-graphene contact points 355 between theCNTs 302 andgraphene 304 present in theaerogel 350 but not in theaerogel 330. These additional CNT-to-graphene contact points 355 allow heat to be more readily transferred from the hot end to the cool end of a heat pipe having a wick of theaerogel 350 than with a wick of theaerogel 330. - A wick aerogel that includes both CNT and graphene provides improved heat transfer over a wick aerogel of CNT alone. When the aerogel does not include graphene, there can be a suboptimal number of contact points between and among the various carbon nanotubes, reducing heat transfer effectiveness. For example, an aerogel using CNT alone can have a maximum thermal conductivity of about 2,000 W/mK at room temperature. By adding graphene to the aerogel, the maximum thermal conductivity of the aerogel can be increased to about 3,000 W/mK at room temperature. This higher thermal conductivity provides increased heat transfer capability for a heat pipe having a wick using CNT plus graphene aerogel. This increased heat transfer capability can reduce the temperature at the hot end of the heat pipe by 10% to 15% as compared to heat pipes having other wick types.
- While the proportion of graphene to CNT in the
aerogel 350 has been increased by increasing the amount of graphene, in other examples the proportion of graphene to CNT in the aerogel can be increased by decreasing the amount of carbon nanotubes in the aerogel. In some examples, the amount of CNT, graphene, or both in the aerogel can be adjusted so as to produce an aerogel having a thermal conductivity in the range of about 1 to about 3,000 W/mK at room temperature. By varying the composition of the aerogel of the wick in this manner, a heat pipe can be tailored to provide an optimal amount of heat transfer capability for a particular application. - Considering now a method of making a heat pipe having a wick of CNT plus graphene aerogel, and with reference to
FIG. 4 , amethod 400 begins at 410 by applying a carbon nanotube and graphene aerogel coating to interior walls of a heat pipe tube. In some examples, the applying 410 includes stretching, cutting, and cleaning 412 the tube. The tube (casing) material may be stretched so as to form a tube with the desired tube diameter and casing thickness. After the stretching, the tube may be cut to the desired length of the heat pipe. The tube is then cleaned. In one example, the tube is given an acid wash, washed in ionized water, washed in a weak alkaline solution, again washed in ionized water, and dried. At 414, one end of the tube is then sealed. In some examples, the sealing is performed by squeezing the tube end and welding it closed. Other methods of stretching, cutting, cleaning, and sealing may be employed. - In some examples, the applying 410 further includes applying 416 carbon nanotube and graphene aerogel in sol-gel form to the interior walls of the heat pipe tube. In some examples, the applying 416 further includes spraying 418 the sol-gel through a nozzle arrangement which corresponds to the cross-sectional shape of the wick structure. The nozzle arrangement may include a set of orifices through which the sol-gel is ejected into the tube. The orifices may define the grooves or fluting of the wick cross-section.
- At 430, the applied coating is sintered to form the heat pipe wick. In one example, the sintering is performed at 500 to 650 degrees C. The sintering removes the solvent from the sol-gel solution and solidifies the aerogel on the interior walls of the tube. The sintering forms a good chemical bond of the carbon nanostructures within the aerogel to form a ceramic-like structure which can exert high capillary force on working fluid which contacts it.
- At 440, the heat pipe is at least partially filled with the working fluid. In some examples, at 442, after the working fluid has been injected, an end of the tube through which the working fluid was injected is sealed.
- From the foregoing it will be appreciated that the heat pipe, wick, aerogel, and methods provided by the present disclosure represent a significant advance in the art. By more effectively conducting heat away from electronic components in contact with the hot end of heat pipes having wicks according to the present disclosure, the lifetime of components such as LCD panels, LEDs, CPUs and similar processors, and batteries can be extended, and the throughput and power efficiency of devices employing them can be increased. The risk of battery explosion in such devices can also be reduced. As such, the disclosed heat pipes can find wide applicability in electronic devices such as for example, notebook computers, tablet computers, smart phones, televisions, and more.
- Although several specific examples have been described and illustrated, the disclosure is not limited to the specific methods, forms, or arrangements of parts so described and illustrated. Terms of orientation and relative position (such as “top,” “bottom,” “side,” and the like) are not intended to indicate a particular orientation of any element or assembly, and are used for convenience of illustration and description. This description should be understood to include all combinations of elements described herein, and claims may be presented in this or a later application to any combination of these elements. The foregoing examples are illustrative, and different features or elements may be included in various combinations that may be claimed in this or a later application. Unless otherwise specified, operations of a method claim need not be performed in the order specified. Similarly, blocks in diagrams or numbers (such as (1), (2), etc.) should not be construed as operations that proceed in a particular order. Additional blocks/operations may be added, some blocks/operations removed, or the order of the blocks/operations altered and still be within the scope of the disclosed examples. Further, methods or operations discussed within different figures can be added to or exchanged with methods or operations in other figures. Further yet, specific numerical data values (such as specific quantities, numbers, categories, etc.) or other specific information should be interpreted as illustrative for discussing the examples. Such specific information is not provided to limit examples. The disclosure is not limited to the above-described implementations, but instead is defined by the appended claims in light of their full scope of equivalents. Where the claims recite “a” or “a first” element of the equivalent thereof, such claims should be understood to include incorporation of at least one such element, neither requiring nor excluding two or more such elements. Where the claims recite “having”, the term should be understood to mean “comprising”.
Claims (15)
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PCT/US2016/028650 WO2017184148A1 (en) | 2016-04-21 | 2016-04-21 | Carbon nanotube and graphene aerogel heat pipe wick |
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Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
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CN113260216A (en) * | 2020-02-10 | 2021-08-13 | 优材科技有限公司 | Heat conduction device and electronic device |
US11246238B2 (en) * | 2020-02-10 | 2022-02-08 | Sulfurscience Technology Co., Ltd. | Heat conductive device and electronic device |
CN114593625A (en) * | 2022-02-22 | 2022-06-07 | 武汉大学 | Evaporation phase change heat transfer component based on gel decoupling drive and application thereof |
Families Citing this family (2)
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WO2019112611A1 (en) * | 2017-12-08 | 2019-06-13 | Hewlett-Packard Development Company, L.P. | Devices for heat transfer |
EP4251939A1 (en) * | 2020-11-24 | 2023-10-04 | Aselsan Elektronik Sanayi ve Ticaret Anonim Sirketi | Performance enhancement in thermal system with porous surfaces |
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US7027304B2 (en) * | 2001-02-15 | 2006-04-11 | Integral Technologies, Inc. | Low cost thermal management device or heat sink manufactured from conductive loaded resin-based materials |
JP2004116871A (en) * | 2002-09-25 | 2004-04-15 | Sony Corp | Heat transport body and electronic apparatus having the same |
JP2005178151A (en) * | 2003-12-18 | 2005-07-07 | Seiko Epson Corp | Sintered body and its manufacturing method |
CN102760709B (en) * | 2011-04-29 | 2015-05-13 | 北京奇宏科技研发中心有限公司 | Loop heat pipe structure |
KR101248931B1 (en) * | 2011-05-24 | 2013-04-01 | 성균관대학교산학협력단 | Micro channel and heat conductor using the same |
-
2016
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Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN113260216A (en) * | 2020-02-10 | 2021-08-13 | 优材科技有限公司 | Heat conduction device and electronic device |
US11246238B2 (en) * | 2020-02-10 | 2022-02-08 | Sulfurscience Technology Co., Ltd. | Heat conductive device and electronic device |
CN114593625A (en) * | 2022-02-22 | 2022-06-07 | 武汉大学 | Evaporation phase change heat transfer component based on gel decoupling drive and application thereof |
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