Complex Dimple Geometry for Improved Plate-Fin Heat Exchanger

The present disclosure claims the benefit of Provisional Patent Application No. 63/637,526, filed on Apr. 23, 2024 and entitled “COMPLEX DIMPLE GEOMETRY FOR IMPROVED PLATE-FIN HEAT EXCHANGER HTC”, the contents of which are incorporated by reference in its entirety.

The present disclosure relates to a heat exchanger for improving heat transfer. In embodiments, the present disclosure relates to a heat sink with dimples.

The performance, lifespan, and safety of many electrical components are dependent on the temperature at which the electrical components operate and a build-up of heat can negatively affect these elements. The temperature of the electrical component may be affected by heat generated from the electrical component or its surrounding environment. Heat sinks are used to dissipate heat from electrical components or other heat-generating devices and prevent the negative effects from a build-up of heat. Some heat sinks use plate fins or pin fins that extend outward from a base that is in thermal communication with the electrical component. As fluids (e.g., air, water, or the like) flow along the heat sink through the fins, the fins transfer the heat from the electrical component to the fluid, cooling the electrical component.

Heat transfer from the heat sink to the fluid can be improved by increasing the surface area of the heat sink. Increasing the surface area of the heat sink typically improves the conductive and convective heat transfer of the heat sink. However, an increase in the surface area of the heat sink can also disrupt the flow of the fluid and result in a diminished convective heat transfer efficiency and a greater pressure drop.

Described herein is in an embodiment of a heat sink for improving heat transfer efficiency. A heat sink including a substrate having an upper surface. A plurality of fins extends outwardly from the upper surface. The plurality of fins extend from a base to a tip and a fin height is defined by a distance between the base and the tip. A plurality of dimples are round and 3D-printed. The plurality of dimples are located between the plurality of fins or on the plurality of fins.

Another embodiment of the heat sink includes a substrate with a first side and a second side opposite the first side. A plurality of fins extend outwardly from the upper surface along a longitudinal direction from adjacent the first side to adjacent the second side. A plurality of dimples include side surfaces that converge to a peak and have a parabolic shape. The plurality of dimples are located on the upper surface between the plurality of fins or on a surface of the plurality of fins. The plurality of dimples are 3D-printed dimples.

Another embodiment of the heat sink includes a substrate having an upper surface, a first side, and a second side opposite the first side. A plurality of fins extend outwardly from the upper surface along a longitudinal direction from adjacent the first side to adjacent the second side. The plurality of fins extend from a base to a tip and a fin height is defined by a distance between the base and the tip. The substrate defines a first set of dimples located on the upper surface between the plurality of fins. The first set of dimples have a dimple height less than 30% of the fin height. The plurality of fins define a second set of dimples on a surface of the plurality of fins that is less than 30% of the fin height or above 70% of the fin height.

Embodiments of the present disclosure are described herein. It is to be understood, however, that the disclosed embodiments are merely examples and other embodiments can take various and alternative forms. The figures are not necessarily to scale; some features could be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative bases for teaching one skilled in the art to variously employ the embodiments. As those of ordinary skill in the art will understand, various features illustrated and described with reference to any one of the figures can be combined with features illustrated in one or more other figures to produce embodiments that are not explicitly illustrated or described. The combinations of features illustrated provide representative embodiments for typical application. Various combinations and modifications of the features consistent with the teachings of this disclosure, however, could be desired for particular applications or implementations.

“A”, “an”, and “the” as used herein refers to both singular and plural referents unless the context clearly dictates otherwise. By way of example, “a processor” programmed to perform various functions refers to one processor programmed to perform each and every function, or more than one processor collectively programmed to perform each of the various functions.

As shown in, according to the prior art, a heat sinkfor dissipating heat from a device capable of generating heat (e.g., an electrical or computer component, an inverter card, or the like) includes a substratewith an upper surface. The heat sinkmay be attached to the device via the outer plate, a thermal paste, a connecting component between the heat sinkand the device, or the like. The heat sinkmay also be connected to a housing (e.g., via an outer plate surrounding the substrate) that encloses the heat sinkfor containing and exposing the substrateto a fluid, such as water, air, refrigerant, oil, dielectric fluid, or some other non-conductive thermal transfer fluid, or the like. The fluid is conveyed (by forced or natural convection) through the heat sinkfrom a first sideto a second sideopposite the first side, as indicated by the fluid flow F.

Finsextend outwardly from the upper surfaceof substratefrom a baseto a tipand along the substratefrom the first sideto the second side. The finsmay be plate fins, pin fins, or the like. In some embodiments, the finsare plate fins arranged in rowsalong a longitudinal direction and the fluid flows between the fins. The fluid flows between the finsand may recirculate in a space between the fins. In some embodiments, the finsare pin fins arranged in uninform or non-uniform rows, a staggered arrangement, or the like. The rowsof the plurality of finsdefine channels(e.g., a space for the fluid to flow between at least two rowsof the plurality of fins) for the fluid to flow from the first sideto the second side. The pin fins may have a shape including an elliptical, an airfoil, a tear-drop, a circular, a conical, a rectangular, a parabolic, or other known shapes, or the like, or a combination or sub-combination thereof.

Referring to, an embodiment of the heat sinkincludes a plurality of dimplesprotruding from the upper surfaceof the substrate(i.e., extending outwardly from the substrate). In some embodiments, the substratedefines the plurality of dimples. The plurality of dimplesmay include a variety of shapes or cross-sectional areas. In some embodiments, the substratedefines the plurality of dimpleshaving a convex shape relative to the upper surface. In other words, the plurality of dimplesmay have a shape that is spherical or round relative to the upper surface(e.g., hemispherical, semispherical, or the like). The plurality of dimplesare disposed in between or amongst the finsand/or in the rows. In some embodiments, the plurality of dimplesare disposed adjacent to or spaced apart from the baseof the fins. For example, the plurality of dimplesmay be in close proximity to the baseof the finsor may be positioned centrally in the rowsbetween the fins.

The plurality of dimplesincreases the surface area of the heat sinkalong the substratefor improving the overall heat transfer coefficient. The increase in surface area of the heat sinkreduces the thermal resistance for conduction. Because conduction through the heat sinkcan be a bottleneck for improvement to thermal performance, a reduction in the thermal resistance for conduction leads to a decrease in the total thermal resistance of the heat sink. Furthermore, the relative fluid flow velocity is at its lowest adjacent the substrateand/or baseof the finssuch that the increase in the surface area of the heat sinkdoes not result in a significant increase in pressure drop across the heat sink. In other words, while the plurality of dimplesmay disrupt the fluid flow velocity along the substrate, the disruption may increase the convective heat transfer coefficient without a significant increase in pressure drop. For example, the plurality of dimplesmay not result in a significant increase of flow separation and/or reversal of the fluid flow velocity.

Referring to, in an embodiment of the heat sinkthe plurality of dimplesmay be arranged in a uniform or non-uniform arrangement or pattern along the substrate. The arrangement of the plurality of dimplesmay be staggered or include at least one rowand/or column, or a plurality of rowsor columns, or the like. For example, at least one channelof the finsmay have a first patternincluding a first rowand a second rowof the plurality of dimplesthat are in a staggered arrangement. In another example, at least one channelof the finsmay have a second patternincluding a single rowof the plurality of dimplespositioned centrally within the at least one channel. In yet another example, at least one channelof the finsmay have a third patternincluding the first rowand the second rowof the plurality of dimplesthat are aligned relative to each other, resulting in columnsdefined by the first rowand the second row. The arrangement of the plurality of dimplesmay be chosen based on the criterion including heat transfer, fluid dynamics, pressure drop, manufacturability, or the like. In some embodiments, the plurality of dimplesincludes a first group of the plurality of dimplesand a second group of the plurality of dimples, wherein the first group of the plurality of dimplesare arranged in the first patternwithin a first channel, and the second group of the plurality of dimplesare arranged in the second patternwithin the second channel, wherein the second patternis different from the first pattern(the first patternand/or the second patterncould be substituted with the third patternor another pattern, or the like).

In an embodiment, the arrangement of the plurality of dimplesmay be uniform or discontinuous between at least two rowsof the finsand/or within at least one channel. In other words, at least one channelmay include a plurality of arrangements of the plurality of dimplesand/or a combination of the first arrangement, the second arrangement, and/or the third arrangement. For example, at least one channelmay include the first arrangementfrom adjacent the first sideto a point between the first sideand the second sideand the second arrangement from the point between the first sideand the second sideto adjacent the second side.

Referring to, in an embodiment of the heat sinkthe plurality of dimplesmay partially or fully extend from the finsadjacent the baseof the fins. In other words, the plurality of dimplesmay extend from the finsand not the substrateor may extend from both the finsand the substrateat approximately the baseof the fins. The plurality of dimplesmay extend from any point along an outer surface of the finsand/or a perimeter defined by the baseof the fins. For example, where the finsare pin fins with an elliptical shape the plurality of dimplesmay extend from the finsalong the perimeter from one vertices to another. In some embodiments, the heat sinkincludes finsthat are elliptical pin fins arranged in staggered rowsalong the substratesuch that a first end or verticesof a first finis adjacent a second endof second fin, wherein the at least one of the plurality of dimplesextends from the first finadjacent the first end. In some embodiments, the heat sinkincludes a plurality of dimplesextending from the outer surface of at least one of the fins.

In an embodiment, the plurality of dimplesextend from the upper surfaceof the substratein a gapdefined by the arrangement of the fins. The gapmay be an area for fluid to flow through, between, and/or amongst the fins. For example, where the finsinclude rowsof elliptical pin fins in a staggered arrangement in a longitudinal direction, the gapmay be a location or space between or adjacent to the ends of two adjacent finsin a common row, between two adjacent rowsof fins, or the like, or a combination or sub-combination thereof. In some embodiments, the channeland the gapmay refer to the same location on the upper surfaceof the substrate.

Referring to, in an embodiment of the heat sinkthe plurality of dimpleshave a parabolic shape, such as a concave or convex parabolic shape. For example, the plurality of dimplesinclude a central axis that extends upwards from the upper surfaceto a peak, and side surfaces. The side surfacehave a parabolic shape in which outer edges of the side surfacesare the vertices of the parabolic shapes and are tangent to the upper surface. In other words, the side surfacesthe plurality of dimplesare concaved or convex parabolas that merge at the peak. The parabolic shape is an efficient shape for improving the heat transfer efficiency of the heat sinkbecause of the increase surface area with a relatively small cross-sectional profile in the direction of the fluid flow F, the rowsof the fins, or from the first sideto the second side, or the like. Referring to, in an embodiment of the heat sinkthe plurality of dimpleshave an airfoil shape. The airfoil shape may be symmetrical, asymmetrical, flat bottom, cambered, or the like, or a combination or sub-combination thereof. In some embodiments, the plurality of dimplesmay have a shape or cross-sectional profile including a rectangular, prismatic, elliptical, tear-drop, circular, conical, or other known shapes, or the like, or a combination or sub-combination thereof.

In an embodiment, the heat sinkincludes a combination of the plurality of dimpleshaving different shapes and/or cross-sectional areas. In other words, the plurality of dimplesmay include a first shape and a second shape. For example, the plurality of dimpleshaving a hemispherical shape, a parabolic shape, and an airfoil shape may be located between at least two rowsof the fins, in at least one channel, and/or in at least one gap. The plurality of dimplesbetween the at least two rows, in the channel, and/or in at least one gapmay transition from the hemispherical shape adjacent the first side, to the parabolic shape at a point between the first sideand the second side, and then to the airfoil shape adjacent the second side, or the like. The plurality of dimplesbetween the at least two rows, in the channel, and/or in at least one gapmay be arranged in a pattern from the first sideto the second side, or a point between the first sideand the second side. For example, the plurality of dimplesmay have the first arrangement, wherein the first rowincludes the plurality of dimpleswith hemispherical shapes and the second rowincludes plurality of dimpleswith parabolic shapes. In another example, the first rowand the second rowmay both include the plurality of dimpleswith the symmetrical airfoil shape and the asymmetrical shape arranged in an alternating pattern within the first rowand the second row(e.g., the first rowmay include the alternating pattern of the plurality of dimpleswith the symmetrical shape and then the asymmetrical shape).

In some embodiments, the plurality of dimplesbetween the at least two rows, in the channel, and/or in at least one gapmay arranged to guide the fluid flow F within the at least one row. Between the at least two rows, in the channel, and/or in at least one gap, the plurality of dimplesmay include a combination of shapes for controlling the fluid velocity, flow rate, flow type, or other fluid dynamics, or the like. For example, the combination of airfoil shapes may be used increase convective heat transfer by guiding the fluid towards the fins, increasing fluid velocity or flow rate adjacent the fins, or preventing or reducing fluid velocity reversal and/or flow separation, or the like or a combination or sub-combination thereof. In other words, the plurality of dimpleswith the asymmetrical, flat bottom, or chambered shape may be disposed adjacent to or in close proximity to the finsto control the dynamics of the fluid. For example, referring to, the combination of plurality of dimplesmay control the dynamics of the fluid adjacent to the concave and convex portions of the finsand/or spaced apart from the fins(i.e., within the center of the channel). In yet a further example, referring to, the combination of the plurality of dimplesmay prevent or reduce fluid velocity reversal and/or flow separation between the endsof the fins.

Referring to, in an embodiment of the heat sinkthe plurality of dimpleshave a dimple heightand a dimple length. The dimple heightof the plurality of dimplesmay be defined as a percentage of a fin height(i.e., the distance between the baseand the tipof the fins). In some embodiments, the dimple heightis less than the fin height. In some embodiments, the dimple heightmay be greater than zero percent and less than five percent of the fin height, greater than or less than 5-10, 10-25, 25-50, or 50-75 percent of the fin height, or the like, or a combination or sub-combination thereof. In some embodiments, the dimple heightmay be defined by a percentage of a fin width. For example, the dimple heightmay be greater than zero percent and less than five percent of the fin width, 5-10, 10-25, 25-50, or 50-75 percent of the fin width, or the like, or a combination or sub-combination thereof.

Referring to, in an embodiment the plurality of dimplesmay extend from the finsspaced apart from the base. In other words, the plurality of dimplesmay extend from the finsat some point between the baseand the tip. The point between the baseand the tipmay be defined by a percentage of the fin height. For example, the plurality of dimplesmay extend from the finsat or between 0-10, 10-20, 20-30, 30-50, 50-75, or 75-100 percent of the fin height. For example, the plurality of dimplesmay extend from the finsat or below 30 percent of the fin height(i.e., adjacent the base) or at or above 70 percent of the fin height(i.e., adjacent the tip). Generally, the fluid flow velocity is lower in regions nears the baseor the tipof the fins. The inclusions of the plurality of dimplesin these low fluid velocity regions increases the surface area of the heat sinkwithout a significant increase in the pressure drop across the heat sink. Thus, the plurality of dimplesimproves the overall heat transfer coefficient of the heat sink. In some embodiments the plurality of dimplesextends from a side surfaceof the fins. In other words, the plurality of dimplesextends outwardly from the side surfaceof the finstoward the center of the respective channels.

In an embodiment, the plurality of dimplesmay include a common or the same shape with varying dimensions, such as dimple height, dimple length, or other dimensions (e.g., diameter, radius, chord, camber line), or the like. For example, the plurality of dimplesmay have a hemispherical shape with some of the plurality of dimpleshaving a first dimple heightand/or dimple lengththat is greater than a second dimple heightand/or dimple lengthof the other plurality of dimples. In some embodiments, the plurality of dimplesmay include a variety of different shapes with different cross-sectional areas, dimple heights, dimple lengths, or other dimensions. For example, the heat sinkmay include a plurality of first dimplesand a plurality of second dimples, wherein the plurality of first dimpleshave a symmetrical airfoil shape and the plurality of second dimpleshave a cambered airfoil shape.

Referring to, in an embodiment the plurality of dimpleshave a lead endand a tail end, wherein the lengthis defined by a distance between the lead endand the tail end. The lead endor the trail endcan be orientated to affect the flow of the fluid across the substrate. As discussed above, the plurality of dimplesmay have different shapes and/or cross-sectional areas. The cross-sectional area of the plurality of dimplestaken along the lengthaffects the flow of the fluid across or around the plurality of dimples. In some embodiments, the cross-sectional area of the plurality of dimplesmay vary (i.e., increase or decrease) from the lead endto the trail end. In some embodiments, the lead endapproximately faces the first sideand the trail endapproximately faces the second side. In other words, the lead endis orientated or directed upstream, or towards the fluid flow F, and the trail endis orientated or directed downstream, or is relatively aligned with the fluid flow F. Referring to, in some embodiments the lead endand/or the trail endof at least one of the plurality of dimplesmay be orientated or aligned relative to at least one gapsuch that flow separation or reversal of the fluid velocity is prevented or reduced by the shape and/or orientation of the at least one of the plurality of dimples.

Referring to, an embodiment of the heat sinkincludes finsthat are plate fins with a nonlinear shape (i.e., a shape that is wavy, curvy, sinusoidal, convex, concave, curvilinear, or the like, or defines a peak and/or valley). The nonlinear shape of the finsincreases the surface area of the finsand acts as a stiffener of the array of fins. As stated previously, the increase in the surface area of the heat sinkreduces thermal resistance for conduction and improves the conductive heat transfer of the heat sink. The convective heat transfer may also increase without a significant increase in the pressure drop. In some embodiments, the lead endof at least one of the plurality of dimplesmay be orientated relative to at least one of the plurality of finssuch that the trail endfaces the side surfaceof the at least one of the plurality of fins. In other words, the lead endof at least one of the plurality of dimplesmay be orientated tangentially to a curvature of at least one of the plurality of fins. For example, at least one of the plurality of dimplesmay be located between a peak and a valley (as defined by the wavy shape) of at least one of the plurality of finswith a nonlinear shape and the lead endof the at least one of the plurality of dimplesmay be orientated tangentially to the side surfaceso as to control the flow of the fluid into, out of, or away from the valley.

The plurality of dimplesmay be composed of any material capable of transferring heat from the device to the fluid (e.g., copper, aluminum, steel, a metal alloy, or the like). The plurality of dimplesmay be formed by precision forging, additive manufacturing, die casting, CNC manufacturing, extrusion, or the like. In some embodiments, the plurality of dimplesare 3D-printed and formed using additive manufacturing methods, such as with metal powders. In particular, using additive manufacturing allows for a precise, controlled, and repeatable method of manufacturing the plurality of dimplessuch that the shape, size, and arrangement of the plurality of dimplesand/or rowsof the plurality of dimplesare consistent with the desired heat transfer, fluid flow properties, and pressure drop, or the like.

While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms encompassed by the claims. The words used in the specification are words of description rather than limitation, and it is understood that various changes can be made without departing from the spirit and scope of the disclosure. As previously described, the features of various embodiments can be combined to form further embodiments of the invention that may not be explicitly described or illustrated. While various embodiments could have been described as providing advantages or being preferred over other embodiments or prior art implementations with respect to one or more desired characteristics, those of ordinary skill in the art recognize that one or more features or characteristics can be compromised to achieve desired overall system attributes, which depend on the specific application and implementation. These attributes can include, but are not limited to cost, strength, durability, life cycle cost, marketability, appearance, packaging, size, serviceability, weight, manufacturability, ease of assembly, etc. As such, to the extent any embodiments are described as less desirable than other embodiments or prior art implementations with respect to one or more characteristics, these embodiments are not outside the scope of the disclosure and can be desirable for particular applications.