Patent Application
20150096719
The present invention relates to an apparatus for dissipating heat, and more particularly to cold plates and cooling tubes.
Miniaturization, increased complexity and/or increased functional capacity of various devices, such as electronic assemblies and individual components, often results in more heat being generated which must be dissipated to maintain performance and avoid damage. Conventional methods for dissipating heat may fail to satisfy cooling requirements and design constraints relating to physical size, weight, power consumption, cost, or other parameters. Accordingly, there is a continuing need for an efficient means for dissipating heat from a variety of heat sources.
Briefly and in general terms, the present invention is directed to an apparatus for dissipating heat.
In aspects of the present invention, an apparatus comprises a plate made of a planar thermal conductive material. The plate includes a top layer and a bottom layer. Each of the top and bottom layers is oriented in an x-direction and a y-direction coplanar with the x-direction. There is at least one fluid passageway formed through the plate and disposed between the top layer and the bottom layer. The at least one fluid passageway is configured to transport a fluid.
Any one or a combination of two or more of the following features can be appended to the aspect above to form additional aspects of the invention.
The top layer is made of the planar thermal conductive material.
The bottom layer is made of the planar thermal conductive material.
The plate includes an intermediate layer between the top layer and the bottom layer, the intermediate layer is made of the planar thermal conductive material, and the at least one fluid passageway extends through the intermediate layer.
The planar thermal conductive material is pyrolytic graphite.
The apparatus further comprises fins on the plate.
The at least one fluid passageway is oriented in the y-direction, the plate has a first thermal conductivity in the x-direction and the y-direction, the plate has a second thermal conductivity in a z-direction perpendicular to the x direction and the y direction, and the first thermal conductivity is at least 100 times the second thermal conductivity.
The at least one fluid passageway is oriented in the y-direction, the plate has a first thermal conductivity in the y-direction and a z-direction perpendicular to the x direction and the y direction, the plate has a second thermal conductivity in the x-direction, and the first thermal conductivity is at least 100 times the second thermal conductivity.
The at least one fluid passageway is oriented in the y-direction, the plate has a first thermal conductivity in the x-direction and a z-direction perpendicular to the x direction and the y direction, the plate has a second thermal conductivity in the y-direction, and the first thermal conductivity is at least 100 times the second thermal conductivity.
The apparatus further comprises a heat source thermally coupled to the top layer of the plate or the bottom layer of the plate.
The apparatus further comprises a thermal bridge between the plate and the heat source, the thermal bridge being any combination of one or more of a heat sink, a heat spreader, a printed circuit board, a standoff, and a rail.
The heat source is an electronic component capable of generating heat.
The apparatus further comprises a pump attached to the plate and configured to pump fluid through the least one fluid passageway.
In aspects of the present invention, an apparatus comprises a pipe configured to transport a fluid and made of pyrolytic graphite, and a plurality of fins on the pipe, each fin configured to dissipate heat from the pipe.
Any one or a combination of two or more of the following features can be appended to the aspect above to form additional aspects of the invention.
Each fin is made of aluminum, copper, other metal, or material other than pyrolitic graphite.
The pipe has a central axis, each fin has a first thermal conductivity in a radial direction perpendicular to the central axis and a second thermal conductivity in an axial direction parallel to the central axis, and the first thermal conductivity is at least 100 times the second thermal conductivity.
The apparatus further comprises a heat source thermally coupled to the pipe.
The apparatus further comprises a thermal bridge between the pipe and the heat source, the thermal bridge being any combination of one or more of a heat sink, a heat spreader, a printed circuit board, a standoff, and a rail.
The heat source is an electronic component capable of generating heat.
The apparatus further comprises a pump attached to the pipe and configured to pump fluid through the pipe.
The features and advantages of the invention will be more readily understood from the following detailed description which should be read in conjunction with the accompanying drawings.
All drawings are schematic illustrations and the structures rendered therein are not intended to be in scale. It should be understood that the invention is not limited to the precise arrangements and instrumentalities shown, but is limited only by the scope of the claims.
As used herein, the phrase “thermally coupled” refers to a physical heat conduction path from a first structure to a second structure. The first and second structures can optionally be separated from each other by an intervening structure which provides a physical thermal bridge between the first and second structures.
As used herein, a “planar thermal conductive material” is a material having a greater thermal conductivity in directions that lie on a particular plane or are parallel to that plane, as compared to other directions which do not lie on the plane and are not parallel to the plane.
As used herein, the phrase “oblique angle” refers to an angle between zero and ninety degrees.
As used herein, the phrase “consisting essentially of” limits the structure being modified by the phrase to the specified material(s) and other materials that do not materially affect the basic characteristics of the structure. For example, a structure that consists essentially of planar thermal conductive material may include small amounts of other elements or impurities which still allow the structure to have greater thermal conductivity in directions on or parallel to a-b planes as compared to c-directions.
As used herein, “standard room temperature” is a temperature from 20° C. to 25° C.
Referring now in more detail to the exemplary drawings for purposes of illustrating embodiments of the invention, wherein like reference numerals designate corresponding or like elements among the several views, there is shown in
Plate 100 can be fabricated from a monolithic piece of the planar thermal conductive material so that plate 100 consists of or consists essentially of an expanse of uninterrupted planar layers of hexagonally arranged carbon atoms. Having uninterrupted planar layers is believed to improve heat dissipation. Alternatively, plate 100 consisting of or consisting essentially of planar thermal conductive material can be fabricated by fastening multiple pieces of the planar thermal conductive material directly to each other.
An example of a suitable planar thermal conductive material is pyrolytic graphite, which provides plate 100 with enhanced thermal conductivity in a particular direction dependent upon the orientation of planar layers of ordered carbon atoms. The carbon atoms of pyrolytic graphite are arranged hexagonally in planes (referred to as a-b planes), which facilitate heat transfer and greater thermal conductivity in directions on the a-b planes. The carbon atoms have an irregular arrangement in directions which do not lie on the a-b plane, which results in diminished heat transfer and lower thermal conductivity in those directions. Thermal conductivity of pyrolytic graphite in directions on a-b planes can be more than four times the thermal conductivity of copper and natural graphite, and more than five times the thermal conductivity of beryllium oxide. Thermal conductivity of pyrolytic graphite for use in any of the embodiments described herein can be in the range of 304 W/m-K to 1700 W/m-K in directions on a-b planes, and 1.7 W/m-K and 7 W/m-K in directions (referred to as c-directions) perpendicular to the a-b planes. The thermal conductivity values are those at standard room temperature. Pyrolytic graphite having these characteristics can be obtained from Pyrogenics Group of Minteq International Inc. of Easton, Pa., USA.
The compositional purity of the planar thermal conductive material will affect thermal conductivity. In some embodiments, plate 100 is constructed such that its thermal conductivity in a first direction corresponding to a-b planes of pyrolytic graphite is at least 100 times or at least 200 times that in a second direction corresponding to a c-direction.
Fluid passageways 104 are through-holes formed through plate 100 and are configured to convey a fluid through the center of plate 100. The fluid can absorb and remove heat from plate 100 as the fluid moves through plate 100. Examples of fluid that can be used include without limitation air, other gases, water, and other liquids. Fluid passageways 104 are disposed between top layer 106A and bottom layer 106C of plate 100. Top layer 106A and bottom layer 106C are made of a planar thermal conductive material such as pyrolytic graphite. Fluid passageways 104 extend through intermediate layer 106B between the top and bottom layers 106A, 106C. Intermediate layer 106B is made of a planar thermal conductive material such as pyrolytic graphite.
Fluid passageways 104 can be formed by drilling a hole into the planar thermal conductive material or joining multiple pieces of the planar thermal conductive material so as to form an empty channel between the pieces. The empty channel which forms the fluid passageway can be straight or have bends. Fluid passageways 104 may optionally include a pipe made of metal or other material which is inserted into the hole or channel in the planar thermal conductive material. Plate 100 is illustrated with two fluid passageways which extend through the entire length of plate 100. Alternatively, only one or a greater number of fluid passageways can be present in plate 100.
In the various figures herein, orthogonal axes 102 indicate the x-, y-, and z-directions relative to plate 100. The x-direction is coplanar with and perpendicular to the y-direction. The z-direction is perpendicular to the x- and y-directions. The x- and y-directions define the x-y plane, the x- and z-directions define the x-z plane, and the y- and z-directions define the y-z plane. Top layer 106A, intermediate layer 106B, and bottom layer 106C are oriented in the x- and y-directions and have thicknesses in the z-direction.
In
The a-b planes of pyrolytic graphite can be oriented parallel to the x-y plane, x-z plane, or the y-z plane. The a-b planes of pyrolytic graphite can also be oriented at any oblique angle to any one or more of the x-y plane, the x-z plane, and the y-z plane.
In
In some embodiments, plate 100 has a first thermal conductivity in the x- and y-directions, and a second thermal conductivity in the z-direction. The first thermal conductivity is at least 100 times or at least 200 times the second thermal conductivity.
In
In some embodiments, plate 100 has a first thermal conductivity in the x- and z-directions, and a second thermal conductivity in the y-direction. The first thermal conductivity is at least 100 times or at least 200 times the second thermal conductivity.
In
In some embodiments, plate 100 has a first thermal conductivity in the y- and z-directions, and a second thermal conductivity in the x-direction. The first thermal conductivity is at least 100 times or at least 200 times the second thermal conductivity.
Apparatus 120 optionally comprises one or more thin, protruding ribs or fins 124 attached to plate 100. Fins 124 are made of aluminum, copper, other metal, planar thermal conductive material, such as pyrolytic graphite. Fins 124 can be made of a material other than pyrolytic graphite. Fins 124 provide additional surface area for dissipating heat. One or more fluid passageways 104 are optionally formed through the center of plate 100. Fins 124 can be added to plate 100 and fastened in place by bonding or by a mechanical fastener. The a-b planes in fins 124 can be oriented in the same or different direction as the a-b planes in plate 100.
Alternatively, fins 124 can be an integral part of plate 100 and are formed by removing material from a single piece of planar thermal conductive material. Having fins 124 which are integral to plate 100 allows for a region of hexagonally arranged carbon atoms of pyrolytic graphite to extend uninterrupted from plate 100 to fins 124 and thereby improve heat dissipation.
It is to be understood that heat sources 122 can be thermally coupled to plate 100 without any fastening. For example, heat sources 122 can rest on plate 100 without being fastened to plate 100. Also, heat sources 122 can rest on top of intervening structure 126 without being fastened to intervening structure 126. Furthermore, intervening structure 126 can rest on top of plate 100 without being fastened to plate 100.
Pipe 142 and fins 144 consisting of or consisting essentially of pyrolytic graphite can be fabricated from a monolithic piece of pyrolytic graphite, which would allow for regions of hexagonally arranged carbon atoms to extend uninterrupted from pipe 142 to fins 144 and thereby improve heat dissipation. Alternatively, pipe 142 and fins 144 consisting of or consisting essentially of pyrolytic graphite can be fabricated by joining multiple pieces of the planar thermal conductive material directly to each other. By joining pieces together, the a-b planes in fins 144 can be oriented in the same or different direction as the a-b planes in pipe 142.
For fins 144 and/or pipe 142, the a-b planes of pyrolytic graphite can be oriented parallel to the x-y plane, x-z plane, or the y-z plane. The a-b planes of pyrolytic graphite can also be oriented at any oblique angle to any one or more of the x-y plane, the x-z plane, the y-z plane.
In some embodiments, the a-b planes are perpendicular to the direction of fluid flow indicated by arrow 107 on the central axis of fluid passageway 104. Fin has a first thermal conductivity in one or more radial directions 110 perpendicular to the central axis and a second thermal conductivity in axial direction 112 parallel to the central axis. Optionally, the first thermal conductivity is at least 100 times or at least 200 times the second thermal conductivity.
Heat sources 122 are thermally coupled to pipe 142 and/or fins 144. Pipe 142 is configured to absorb and remove of heat from heat sources 122. Fluid flowing through pipe 142 will absorb and carry away heat from pipe 142. Fins 144 are thermally coupled to pipe 142. When pipe 142 is disposed between heat source 122 and portions 144A (
Heat sources 122 are optionally fastened directly to pipe 142 and/or fins 144. Fastening of heat sources 122 can be accomplished by bonding and/or a mechanical fastener, such as disclosed for
Intervening structures 126 can provide an indirect connection and thermal bridge between heat sources 122 and pipe 142 and/or between heat source 122 and fins 144. Intervening structures 126 are conceptually illustrated as a single rectangular block. It is to be understood that the shape and size of intervening structures 126 can differ from the illustrated block, and the illustrated block may include one or more discrete components that form a thermal bridge that thermally couples one or more heat sources 122 to pipe 142 and/or to fins 144. Examples of discrete components include without limitation those described for
Intervening structure 126 is optionally fastened to pipe 142 and/or fins 144. Heat sources 122 are optionally fastened to intervening structure 126. Fastening can be accomplished by bonding and/or a mechanical fastener, such as disclosed for
As shown in
While several particular forms of the invention have been illustrated and described, it will also be apparent that various modifications can be made without departing from the scope of the invention. It is also contemplated that various combinations or subcombinations of the specific features and aspects of the disclosed embodiments can be combined with or substituted for one another in order to form varying modes of the invention. All variations of the features of the invention described above are considered to be within the scope of the appended claims. It is not intended that the invention be limited, except as by the appended claims.
