BACKGROUND

[0001] A heat sink is a passive heat exchanger for cooling a device or a system by dissipating heat into the surrounding environment. The heat sink serves as a thermal conductor that carries away heat. In some configurations, a heat sink can be used in conjunction with a fan that will provide an active air flow to the heat sink.

BRIEF DESCRIPTION OF THE DRAWINGS

[0002] FIG. 1 illustrates an example system deployed with an example heat sink system having a stacked fin structure;

[0003] FIG. 2 illustrates an example of a single plate of the stacked fin structure;

[0004] FIG. 3 illustrates an isometric view of the example heat sink system; and

[0005] FIG. 4 illustrates a close-up isometric view of the example heat sink system.

DETAILED DESCRIPTION

[0006] The present disclosure broadly discloses an example heat sink system having a stacked fin structure. In one example, a stacked fin structure comprises a plurality of parallel heat sink walls or heat sink plates. Each heat sink plate can be made from a metal, e.g., aluminum, copper or any other type of sheet metal. In operation, a heat sink is configured to maximize its surface area in contact with a cooling medium surrounding the heat sink. The cooling medium may comprise the air surrounding the heat sink, or a cooling medium that is integrated into the heat sink, e.g., one or more heat pipes carrying a working fluid such as water, ammonia, methanol or acetone.

[0007] For example, if a fan is used in conjunction with a heat sink system having a stacked fine structure, an aeroacoustic effect may occur. Aeroacoutics involves a field of acoustics that focuses on noise generation via either turbulent fluid motion or aerodynamic forces interacting with a plurality of surfaces. One illustrative example of this phenomenon is the various sounds that can be generated when wind blows over fixed objects or surfaces. This sound production occurs typically at high speed flows. Furthermore, when the flow is confined, the acoustic energy can accumulate into resonant modes. It is noted that the acoustical particle displacement velocity may be in the same order of magnitude as the main flow velocity, such that the feedback from the acoustical field to the sound source can be very significant. This situation may lead to the occurrence of self-sustained oscillations which can be associated with a whistling sound. Namely, in the presence of walls or plates, the sound radiation by turbulence can be dramatically enhanced.

[0008] In certain systems where the application of cooling may enhance the operation of the systems, a fan may be deployed in conjunction with a heat sink system having a stacked fin structure. The fan is deployed to provide a high speed air flow directed at the heat sink system having the stacked fin structure. In other words, an active air flow that is generated by the fan is directed toward the parallel heat sink plates of the heat sink system. As the air flow passes through the parallel heat sink plates of the heat sink system, a significant amount of heat can be quickly dissipated away from the heat sink system.

[0009] In an example electronic system, the heat sink system can be attached to various electronic components that may generate a significant amount of heat, e.g., a microprocessor. For example, heat sinks can be deployed in computer systems because the higher a microprocessor's cooling rate, the faster the computer can operate without instability. Generally, faster operations may lead to higher performance. Since a microprocessor is designed to operate at an ever increasing clock speed, a microprocessor may generate a significant amount heat during normal operation. Such heat is often generated within the confine of an enclosure or housing of the electronic system, thereby exacerbating the temperature condition within the electronic system.

[0010] In an example heating or cooling system, the heat sink system can be attached to various heat pipes to draw heat away. For example, in a vehicle, a fan can be directed at a radiator having a stacked fin structure to draw heat away from the vehicle engine. Similarly, an example air conditioning system or a refrigerator may have a fan directed at a heat sink system with a stacked fin structure to draw heat away from a condensing unit and the like. Thus, there are many applications where a fan can be used in conjunction with a heat sink system having a stacked fin structure. However, due the aeroacoustic effect as discussed above, unwanted sound may be present when a fan is used in conjunction with a heat sink system having a stacked fin structure. Such unwanted sound may emanate from the housing of a computer system, the engine compartment of a car, or the housing of a refrigeration system or unit, e.g., a refrigerator or an air conditioning unit, and the like.

[0011 ] Sound waves are generated by variations in pressure. These variations in pressure may lead to the generation of longitudinal waves.

Longitudinal waves are waves in which the medium, e.g., air medium, oscillates in the direction of the transmission of the waves. These pressure variations can be detected by the human ears. Therefore, in one example, sound is a sensation created in the human brain in response to pressure fluctuations in the air medium. It should be noted that the longitudinal waves can have a large set of frequencies and wavelengths. However, the human brain may only be able to perceive a certain range of audible frequencies. The waves that correlate to audible frequencies are known as sound waves.

[0012] As air flow passes through various obstructions, e.g., parallel plates of a stacked fin structure, a disturbance is created in the air flow that leads to the generation of pressure variations. Such disturbances in the air medium would lead to pressure variations within the air medium. These variations lead to longitudinal waves if within the audible frequency range, would allow a human to hear the pressure variations as sound.

[0013] However, if two or more waves exist in the same air medium, then these waves may interfere with each other. The interference can be

constructive interference or destructive interference. When the peaks of the waves line up, there may be constructive interference. Often, this is described by stating that the waves are "in-phase." In contrast, when the peaks of one wave line up with the valleys of another wave, then there may be destructive interference. This is described by stating that the waves are "out-of-phase."

[0014] If such interference can be made to create destructive interference, then the unwanted sound can be reduced. The present disclosure illustrates various examples of stacked fin structures that will induce destructive

interference to bring about a reduction of an unwanted sound created by the aeroacoustic effect.

[0015] FIG. 1 illustrates an example system 100 deployed with an example heat sink system 150 having a stacked fin structure. For example, FIG. 1 illustrates an electronic system 100, e.g., a desktop computer, a laptop, a set- top box, an audio receiver system or any other electronic systems where a fan and a heat sink system comprising a stacked fine structure are used to dissipate heat away from the electronic systems.

[0016] The example system 100 may comprise a chassis or housing 1 10 that encloses various components 180 (only one component is shown in FIG.1 for clarity reasons) that may need to be cooled. For example, the component 180 may comprise a microprocessor. In another example, the component 180 may comprise heat pipes carrying a working fluid, where the heat pipes may in turn pass through a device that needs to be cooled, e.g., a condensing unit, a radiator, and the like. The example system 100 comprises a heat sink system 150 having a stacked fin structure having a plurality of parallel heat fin plates 155 (broadly plates or metal plates). The space defined by every two parallel plates 155 is referred to as a fin cell 157. The heat sink system 150 is in direct physical contact with the component 180 so that heat from the component 180 can be transferred to the heat sink system 150.

[0017] In one example, a fan 140 is also deployed within the housing 1 10, where the fan 140 is tasked with generating an air flow 130 directed at the heat sink system 150. In one example, the generated air flow passes through the stacked fin structure and carries heat away and through an opening 120 of the housing 1 10. Thus, heat generated by the component 180 is carried away and expelled from the system 100 through the opening 120. It should be noted that the placement of the fan 140 as illustrated in FIG. 1 can be selectively chosen to meet the requirement of a particular system. As such, the fan 140 can be deployed "in front" of the heat sink system 150 or the fan 140 can be deployed "behind" the heat system 150. As long as an air flow can be directed toward the heat sink system 150, the physical placement of the fan 140 can be arbitrarily chosen to meet the requirements of a particular system.

[0018] FIG. 2 illustrates an example of a single plate 155 of the stacked fin structure 150. In one example, the plate 155 comprises a plurality of "raised" fins or "punch outs" 160. For example, the raised fin can be formed by punching out a polygon shape out of the plate 155. However, one side or edge of the punched out polygon is still attached to the plate. In other words, one side or edge of the chosen polygon shape is left uncut so that the polygon shape is still attached to the plate 155. However, the polygon shape is raised or angled away from the plate at an angle (broadly a raised angle), thereby creating a "raised" or "angled" fin for each of the polygon shape. In one example, the angle of the raised fin relative to the plate 155 can be between 15 degrees to 45 degrees.

[0019] In one example, the polygon shape is a tetragon having four (4) sides, e.g., a square, a rectangle, a rhombus, a parallelogram, a trapezoid or a kite. In another example, the polygon shape comprises at least four sides, but is not limited to a tetragon, e.g., a pentagon, a hexagon, a heptagon, or an n-gon (where n is greater than 3) are within the scope of this example. In other words, the plurality of raised fins on each of the plurality of parallel plates may have different n-gon shapes, e.g., tetragons, pentagons, hexagons, heptagons, and so on. More generically, the plurality of raised fins on each of the plurality of parallel plates may have different n-gon shapes, where the different n-gon shapes may comprise a 4-gon shape and at least one other n-gon shape where n is greater than 4.

[0020] FIG. 2 illustrates the example plate 155 as having a plurality of raised fins 160 that are tetragons. In one example, the plurality of raised fins 160 on plate 155 has different shapes, e.g., some tetragons are squares, some tetragons are rectangles, some tetragons are rhombuses, some tetragons are parallelograms, some tetragons are trapezoids, and some tetragons are kites. Thus, each type of the tetragons or n-gons (where n is 4 or greater) that is deployed on the plate 155 can be different. In other words, if a plurality of tetragons or n-gons is deployed on plate 155, then the shapes of the plurality of tetragons or n-gons can be made different (e.g., the plate 155 may have one square, two trapezoids, three rectangles, four pentagons, five hexagons and so on). This non-uniformity in the shapes of the plurality of raised fins 160 creates a non-uniform turbulence within each fin cell 157.

[0021] Similarly, if a plurality of square raised fins is deployed on plate 155, then the size of the plurality of square raised fins can be made different (e.g., small square (e.g., one inch square) versus large square (e.g., two inch square)). Similarly, if a plurality of trapezoid raised fins is deployed on plate 155, then the size of the plurality of trapezoid raised fins can be made different (e.g., small trapezoid versus large trapezoid) and so on. This non-uniformity in the sizes of the plurality of raised fins 160 again creates a non-uniform turbulence within each fin cell 157.

[0022] Furthermore, in one example, the plurality of raised fins 160 is not uniformly spaced on each plate 155. In other words, the plurality of raised fins 160 is not uniformly spaced apart from each other. This non-uniformity in spacing (e.g., physical separation such as lateral separation) of the plurality of raised fins 160 again creates a non-uniform turbulence within each fin cell 157.

[0023] Furthermore, in one example, the plurality of raised fins 160 is not uniformly oriented on each plate 155. In other words, the plurality of raised fins 160 is not uniformly oriented relative to each other. For example, the two trapezoids as illustrated in FIG. 2 are not uniformly oriented relative to each other. These two trapezoids are offset by an angle of rotation. This non- uniformity in orientation of the plurality of raised fins 160 again creates a nonuniform turbulence within each fin cell 157.

[0024] Furthermore, in one example, the plurality of raised fins 160 is not uniformly raised on each plate 155. In other words, the plurality of raised fins 160 is not uniformly raised relative to each other. For example, one raised fin may have a raised angle of 15 degrees, whereas another raised fin may have a raised angle of 30 degrees, and whereas yet another raised fin may have a raised angle of 45 degrees, and so on. This non-uniformity in raised angle of the plurality of raised fins 160 again creates a non-uniform turbulence within each fin cell 157.

[0025] In one example, using the raised fins having the varying shapes, sizes, spacings, orientations and/or raised angles as illustrated in FIG. 2 allows a heat sink system 150 as shown in FIG. 1 to minimize unwanted sound due to the aeroacoustic effect. As discussed above, the human ear is able to perceive the pressure variations as the air flow created by the fan 140 passes through the heat sink system 150. To address the unwanted sound, the present disclosure provides examples of a plurality of raised fins on each of the plate of the stacked plate structure to induce destructive interference. For example, each "raised" side or edge of the raised fin will create turbulence on its respective edge. In other words, as the air flow passes between two plates 155 of the stacked fin structure, each "raised" side or edge of the raised fin 160 will create turbulence within the respective fin cell 157. These turbulences are nonuniform in nature, due to the varying shapes, sizes, spacings, orientations and/or raised angles of the plurality of raised fins 160. Systems that employ the heat sink system 150 of the present disclosure will likely see a reduction of unwanted sound due to the aeroacoustic effect.

[0026] FIG. 3 illustrates an isometric view of the example heat sink system 150. In one example, one or more heat pipes 310 are deployed with the heat sink system 150 having a plurality of parallel plates 155. A heat pipe is a sealed hollow heat transfer device, e.g., a tube that carries a working fluid, e.g., water. The heat pipe is constructed from a material that will be compatible with the corresponding working fluid, e.g., copper is appropriate for water, aluminum is appropriate for ammonia, and so on. In one example, the heat pipe carries both the vapor form and the liquid form of the working fluid. In operation, the heat pipe carries the saturated liquid of the working fluid and the working fluid's vapor (gas phase). For example, the saturated liquid of the working fluid vaporizes and travels to a condenser, where the working fluid is cooled and turned back to a saturated liquid state. The cause of the working fluid to vaporize is due to the physical contact of the heat pipe to a component that requires cooling, e.g., a microprocessor. In one example, the condensed liquid in the heat pipe is returned to an evaporator using a wicking structure that exerts a capillary force on the liquid phase of the working fluid.

[0027] For example, the one or more heat pipes 310 of FIG. 3 may carry heated vapor of a working fluid. As the vapor passes through a part or a portion of each of the heat pipes that is enveloped by the heat sink system 150, heat in the heat pipes is dissipated away from the heat pipes and onto the plates of the heat sink system 150. In turn, as the air flow is provided through the plates of the heat sink system 150, the heat is dissipated away from the heat sink system 150. The present disclosure is not limited to any particular type of heat pipes. For example, the heat pipes may comprise a vapor chamber heat pipe, a variable conductance heat pipe, a pressure controlled heat pipe, a diode heat pipe, a thermosyphon, and so on.

[0028] FIG. 4 illustrates a close-up isometric view of the example heat sink system 150 having a plurality of plates 155 and one or more heat pipes 310. As shown in FIG. 4, each plate 155 may comprise a plurality of raised fins 160. In one example, the plurality of raised fins 160 on each plate 155 can be raised on either side of the plate 155. For example, raised fin 160a is illustrated as being raised at an angle protruding "out" of the page of FIG. 4. In contrast, raised fin 160b is illustrated as being raised at an angle protruding "into" the page of FIG. 4. This illustrative configuration of the raised fins 160a and 160b allow turbulences to be created on either side of the plate 155. In other words, for each fin cell 157, the raised fins 160 may protrude from either or both parallel plates 155.

[0029] It should be noted that each fin cell 157 is defined by two parallel plates 155, where the two parallel plates 155 are in a stacked configuration. As such, there may be one or more connecting structures or members that connect the various parallel plates 155 together. In one example, a top plate 410 and a bottom plate 420 (broadly one or more connection members) can be used in conjunction with a plurality of parallel plates 155 to form the heat sink system 150. Although a top plate 410 and a bottom plate 420 are shown in FIG. 4, in one example a single joining plate or connection member can be used to connect the plurality of parallel plates 155.

[0030] In addition, it will be appreciated that variants of the above-disclosed and other features and functions, or alternatives thereof, may be combined into many other different systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.