Fin architecture for promoting heat exchange

Abstract

The invention relates to a cooling device (1) comprising at least one cooling fin (12), the device (1) being configured to allow a heat transfer fluid (2) to flow along the at least one cooling fin (12) in a first direction (D1), the heat being exchanged by convection between the at least one cooling fin (12) and the heat transfer stream (2), the cooling fin (12) comprising: - a heat exchange surface (10) configured to allow heat to be exchanged to the heat transfer fluid (2), - a first wall (120) and a second wall (122), the first wall (120) and the second wall (122) extending along a plane substantially parallel to the first direction (D1) and substantially perpendicular to the heat exchange surface (10), - a cavity (124) between the first wall (120) and the second wall (122), the heat transfer fluid (2) flowing through the cavity (124), - a heat exchanger (14) contained in the cavity (124) and connected to the heat exchange surface (10), the heat exchanger (14) having a fractal structure on a plane (P1) perpendicular to the first direction (D1) of the heat transfer fluid (2).

Description

DESCRIPTION Fin architecture promoting heat exchange

[0001] The invention relates to the cooling of a heat-producing component. The invention finds application in the field of electrical machines and power electronics. Indeed, it is known that electronic equipment, computers, and electronics in general generate losses that result in heat production, which must be dissipated. Dissipating this heat, ensuring the proper functioning of the aforementioned components, thus becomes a priority. The invention finds particular application in the field of embedded electronics, where the trend is to increase the number of electrical devices and therefore the amount of onboard electrical power.

[0002] The invention relates more particularly to a cooling fin architecture for such a heat exchanger.

[0003] Currently, a large number of electronic systems are equipped with heat exchangers, allowing heat to be removed from the elements dissipating thermal energy to a source of heat removal, in order to allow this electronic system to operate under optimal conditions.

[0004] Today, heat exchangers are known to include a set of fins arranged along the direction of movement of a heat transfer fluid, for which heat exchange with a second fluid or the thermal element itself is desired, for example, straight fins in the direction of an airflow passing through the heat exchanger using the fins to extract thermal energy to a fluid at a lower temperature, or a fluid using the fins to extract thermal energy generated by an electronic component.

[0005] The function of the fins is to allow heat exchange between two fluids, or a fluid and a heat-conducting solid element, these two elements being at different temperatures. More precisely, the fins are then... interfaces used to improve the efficiency of exchanges between the aforementioned elements, namely the two heat transfer fluids or the fluid and the solid element.

[0006] The use of a single heat transfer fluid circulating through the heat exchanger is preferred for reasons of compactness and weight. Indeed, adding a second heat transfer fluid and the entire circuit for its circulation often generates excess mass and volume that must be taken into account, especially in the aeronautical field where the main challenge is managing vehicle mass.

[0007] Therefore, the cooling of an electrical machine is currently limited by mass and size constraints that the state of the art is not able to overcome.

[0008] Thus, in a cooling configuration between a heat transfer fluid operating a direct extraction of heat from the fins of the heat exchanger, an exchange surface in contact with the heat exchanger and with the heat transfer fluid, at the level of the cooling fins, can be identified to allow this thermal extraction.

[0009] In order to improve this exchange, research is currently being carried out concerning the contact surface of these fins between the heat transfer fluid on which the heat exchange is desired and the solid element used for this exchange.

[0010] Furthermore, the main processes for manufacturing such fins are stamping or bending, which limits the shapes, and therefore the performance of heat exchange.

[0011] Thus, it is currently difficult, if not impossible, for technical and manufacturing reasons, to improve this heat exchange at the level of the heat exchanger fin surface.

[0012] The invention aims to overcome all or part of the problems mentioned above by proposing fin shapes that increase the exchange surface area between the heat source, namely the solid element, and a heat transfer fluid flowing through the heat exchanger, thus enabling the transfer of thermal energy. This geometric evolution has the advantage of increasing the heat exchange surface area, thereby improving heat exchange, while limiting any potential loss of charge of the flow or heat transfer fluid passing through the heat exchanger, leading to a decrease in heat exchange.

[0013] To this end, the invention relates to a cooling device comprising at least one cooling fin, the device being configured to allow circulation of a heat transfer fluid along at least one cooling fin in a first direction, heat exchange being able to occur by convection between the at least one cooling fin and the heat transfer fluid flow, the cooling fin comprising: - A heat exchange surface configured to allow heat exchange with the heat transfer fluid, - A first wall and a second wall, the first wall and the second wall extending along a plane substantially parallel to the first direction and substantially perpendicular to the heat exchange surface, - A cavity between the first wall and the second wall, with the heat transfer fluid circulating within the cavity, - A heat exchanger contained within the cavity and connected to the heat exchange surface, the heat exchanger having a fractal structure along a plane perpendicular to the first direction of the heat transfer fluid.

[0014] According to one aspect of the invention, the heat exchanger is connected to the first wall and the second wall.

[0015] According to one aspect of the invention, the heat exchanger is defined so as to maximize the heat exchange surface area.

[0016] According to one aspect of the invention, the heat exchanger comprises a repetition of an elementary pattern.

[0017] According to one aspect of the invention, the elementary motif comprises a larger dimension less than 12 millimeters.

[0018] According to one aspect of the invention, the heat exchanger includes an additional exchange surface, the additional exchange surface representing at least one quarter of the surface area included in the cavity of the cooling fin along the plane perpendicular to the direction of the heat transfer flow.

[0019] According to one aspect of the invention, the elementary pattern is a polygonal pattern.

[0020] According to one aspect of the invention, the polygonal pattern is open along at least one side of the polygonal pattern.

[0021] According to one aspect of the invention, the elementary motif comprises a broken vertex.

[0022] According to one aspect of the invention, the elementary motif comprises a folded vertex.

[0023] According to one aspect of the invention, the heat exchanger comprises a second elementary motif, the second elementary motif being of smaller dimensions than the dimensions of the elementary motif.

[0024] According to one aspect of the invention, the second elementary motif is a motif identical to the elementary motif.

[0025] According to one aspect of the invention, the dimensions of the second elementary motif are half the size of the dimensions of the elementary motif.

[0026] According to one aspect of the invention, the heat exchanger comprises a self-similar fractal structure.

[0027] The invention also relates to a method for manufacturing a cooling fin for the heat exchanger comprising an additional heat exchange surface, the method comprising the following steps: - Selection of a unit section of the additional heat exchange surface of the heat exchanger, - Angular modification of the unit section of the additional exchange surface in a first direction of modification, the angular modification consisting of the creation of an isosceles triangle with a major base the unit section of the selected additional exchange surface, in the first direction of modification, the isosceles triangle comprising two subdivided sides and a height equal to the length of the unit section of the selected additional exchange surface multiplied by a predefined factor k, the isosceles triangle being open on the major base, - Selection of one subdivided side from among the two subdivided sides, - Angular modification of the selected subdivided side in a second modification direction secant to the first modification direction, - Selection of the other subdivided side from among the two subdivided sides, - Angular modification of the other subdivided side selected in the second direction of modification, - Repeat the previous steps.

[0028] According to one aspect of the invention, the second direction of modification is substantially opposite to the first direction of modification.

[0029] The invention will be better understood and other advantages will become apparent upon reading the detailed description of an exemplary embodiment, illustrated by the accompanying drawings in which:

[0030] [Fig.1] Figure 1 represents a schematic cross-sectional view of a cooling fin of a cooling device according to the invention;

[0031] [Fig.2] Figure 2 represents a schematic cross-sectional view of the cooling fin according to a second configuration;

[0032] [Fig.3] Figure 3 represents a schematic cross-sectional view of the cooling fin according to a third configuration;

[0033] [Fig.4] Figure 4 represents a schematic cross-sectional view of the cooling fin according to a fourth configuration;

[0034] [Fig.5A] Figure 5A represents a schematic view of the cooling fin of Figure 4 according to a first variant;

[0035] [Fig.5B] Figure 5B represents a schematic view of the cooling fin of Figure 4 according to a second variant;

[0036] [Fig.6] Figure 6 represents a schematic cross-sectional view of the cooling fin according to a fifth configuration;

[0037] [Fig.7] Figure 7 represents a schematic cross-sectional view of the cooling fin according to a sixth configuration;

[0038] [Fig.8] Figure 8 represents a schematic cross-sectional view of the cooling fin according to a seventh configuration;

[0039] [Fig.9] Figure 9 represents a method for making a heat exchanger for a cooling fin of a cooling device according to the invention.

[0040] For the sake of clarity, the same elements will carry the same markers in the different figures.

[0041] Figure 1 shows a schematic view of a cooling fin 12 of a cooling device 1 comprising at least one cooling fin 12 as shown. The cooling device 1 is configured to allow the circulation of a heat transfer fluid 2 along at least one cooling fin 12 in a first flow direction D1 of the heat transfer fluid 2. Thus, heat exchange can occur by convection between the cooling fin 12 and the heat transfer fluid 2. In a preferred configuration of the invention, as shown in Figure 1, the first flow direction D1 of the heat transfer fluid 2 is parallel to the direction in which the cooling fin 12 extends.In other words, the heat transfer fluid 2, which moves parallel to the first direction D1, passes perpendicularly through the cooling fin 12 along a plane P1 perpendicular to the first direction D1 so as to exchange by convection with the cooling fin 12.

[0042] And, this heat exchange is very efficient for the heat transfer fluid located near the cooling fin 12, whereas the heat exchange is less efficient, in comparison to the heat exchange by convection between the heat transfer fluid 2 located in the direct vicinity of the cooling fin 12 and the cooling fin 12 itself.

[0043] Alternatively, it may be envisaged that the first direction D1 is secant to the development direction of the cooling fin 12. It may also be envisaged that the heat transfer fluid 2 passes through the cooling fin 12 in the first direction D1 before exchanging heat with a second fluid of lower temperature.

[0044] Furthermore, the cooling fin 12 includes a heat exchange surface 10 configured to allow heat exchange with the heat transfer fluid 2. The heat exchange surface 10 is thus a heat-conducting surface that distributes heat over the entire heat exchange surface by conduction, thereby enabling a heat exchange zone with the heat transfer fluid 2 along the entire length of the cooling fin 12. The exchange surface The heat exchanger 10 is thus a hot body that needs to release a quantity of heat, while the heat transfer fluid 2 is a cold body whose function is to exchange heat with the heat exchanger surface 10 and extract heat. The heat exchanger surface 10 advantageously comprises a thermally conductive material. This heat is transferred from the heat exchanger surface 10 to the heat transfer fluid 2, which flows through the cooling fin 12 by convection, thereby removing heat from the cooling device 1. This heat exchange occurs primarily along and near the heat exchanger surface 10.

[0045] The cooling fin also includes a first wall 120 and a second wall 122 extending substantially parallel to the first direction D1 and in a plane substantially parallel to the first direction D1 and substantially perpendicular to the heat exchange surface 10. The first wall 120 and the second wall 122 thus form the load-bearing structure of the cooling fin 12.

[0046] Furthermore, the cooling fin includes a cavity 124 situated between the first wall 120 and the second wall 122 in which the heat transfer fluid 2 circulates. In other words, the heat transfer fluid 2, which exchanges heat with the heat exchange surface 10, flows through the cooling fin 2 between the first wall 120 and the second wall 122 substantially parallel to the first direction D1.

[0047] It can be envisaged to connect the first wall 120 and the second wall 122 so as to define a closed cavity 124 between the first wall 120 and the second wall 122 as shown in figure 1. From then on, the first wall 120 is connected to the second wall 122 by way of the heat exchange surface 10 but also by another upper connection 123.

[0048] Alternatively, the first wall 120 is connected to the second wall 122 only through the heat exchange surface 10. Therefore, the upper connection 123 is no longer shown and the cavity communicates with an environment external to the cooling fin 12.

[0049] However, as observed previously, the heat exchange between the hot body, namely the heat exchange surface 10, and the cold body, namely the fluid heat transfer fluid 2 is carried out efficiently along the heat transfer surface 10 and in the vicinity of the heat transfer surface 10. And, this efficiency of heat exchange between the heat transfer surface 10 and the heat transfer fluid 2 decreases proportionally with respect to the distance between the heat transfer fluid 2 and the heat transfer surface 10.

[0050] Thus, advantageously, the cooling fin 12 includes a heat exchanger 14 contained within the cavity 124 and connected to the heat exchange surface 10. The heat exchanger 14 includes a fractal structure represented in the plane P1 perpendicular to the first direction D1 of the heat transfer fluid 2.

[0051] Thus, the heat exchanger 14 is defined as a structure capable of increasing the heat exchange surface 10, or even maximizing it. In other words, the heat exchanger 14 provides an additional heat exchange surface compared to the heat exchange surface 10, thereby also enabling heat exchange by convection between the heat transfer fluid 2 and the heat exchanger 14. Indeed, the heat exchanger 14 also exhibits good conductivity, so that the heat contained within the heat exchange surface 10 can be conducted into the heat exchanger 14. Consequently, the convective exchange no longer occurs solely between the heat transfer fluid 2 and the heat exchange surface 10, but also between the heat transfer fluid 2 and the heat exchanger 14. The convective heat exchange is thus improved.

[0052] Thus, the heat exchanger 14 includes within its structure a repetition of a simple elementary motif 140. In the configuration of Figure 1, this elementary motif 140 is a rhombus connected to the heat exchange surface 10.

[0053] The term "fractal" is therefore to be understood as a structure comprising only a repetition of a simple elementary pattern 140 extending into the cavity 124. In other words, the fractal structure of the heat exchanger 14 is a fragmented structure through the elementary pattern 140.

[0054] Furthermore, the heat exchanger 14 also has the advantage, in addition to increasing the heat exchange surface area with the heat transfer fluid 2 and improving heat exchange with the heat transfer fluid 2, of not impacting the Heat transfer fluid 2 flows through the cooling fin. Indeed, positioning an object to face the movement of heat transfer fluid 2 along the first direction D1 generally induces a deflection in the movement of heat transfer fluid 2, a loss of flow velocity of heat transfer fluid 2 in the cooling fin, and overall a pressure drop. On a macroscopic scale, this decrease in the pressure of heat transfer fluid 2 flowing through the cooling fin 12 and the heat exchanger 14 then translates into a decrease in the flow rate of heat transfer fluid 2 passing through cavity 124 in particular. Consequently, the heat exchange between the heat exchange surface 10 or the heat exchanger 14 and the heat transfer fluid 2 is negatively impacted.However, the fractal structure of the heat exchanger 14 has the advantage of improving heat exchange without impacting, or only slightly impacting, the load related to the heat transfer fluid 2 passing through the cooling fin.

[0055] Indeed, the wall forming the fractal structure of the heat exchanger 14 is relatively small so as not to deflect the movement of the heat transfer fluid 2 in the cavity 124. And, this fractal structure ensures good rigidity of the heat exchanger, in addition to its multiple fixing with the heat exchange surface 10.

[0056] Thus, the cooling fin according to the invention allows, via the heat exchanger 14, to increase the overall heat exchange surface area by limiting the pressure drop of the heat transfer fluid 2 passing through the cooling device 1.

[0057] Alternatively, and in order to improve the rigidity of the heat exchanger 14, it may be envisaged to connect the heat exchanger 14 to the first wall 120 and to the second wall 122 by way of, for example, the upper connection 123.

[0058] According to a second example of configuration, shown in Figure 2, the heat exchanger 14 can also be directly connected to the first wall 120 and the second wall 122. This configuration distributes the fixings of the heat exchanger 14 more evenly in the cavity 124 of the cooling fin 12 and improves the rigidity of the heat exchanger 14.

[0059] Furthermore, it can also be envisaged that the first wall 120 and / or the second wall 122 conduct heat from the exchange surface thermal 10. Therefore, the overall heat exchange surface in the cooling fin consists of the heat exchange surface 10, the first wall 120, the second wall 122 and the heat exchanger 14. And, the heat exchanger 14 then allows a better distribution of heat in the heat exchange surface 10, the first wall 120, the second wall 122 and the heat exchanger 14 and particularly in the first wall 120 and in the second wall 122 or even in the upper connection 123.

[0060] Indeed, as stated previously, the greater the distance between two bodies, the more difficult the heat exchange becomes. This is also the case for conduction between the heat exchange surface 10, which is the hot body, and, for example, the upper connection 123 or an end of the first wall 120 or the second wall 122 not directly connected to the heat exchange surface 10.

[0061] Therefore, in the absence of the heat exchanger 14, the only thermal path allowing heat to be conducted from the heat exchange surface 10 to the upper connection 123 or to an end of the first wall 120 or of the second wall 122 not directly connected to the heat exchange surface 10 is the thermal path passing through the end 120' of the first wall 120 and the end 122' of the second wall 122 connected directly to the heat exchange surface 10 and then passing through the entirety of the first wall 120 or of the second wall 122.

[0062] However, the heat is not then fully transmitted and the upper connection 123 or the end of the first wall 120 or the second wall 122 not directly connected to the heat exchange surface 10 is relatively colder than the heat exchange surface 10, which degrades the heat exchange by convection with the heat transfer fluid 2 since the temperature differential is reduced.

[0063] The heat exchanger 14, through its fractal structure, allows the generation of several thermal paths between different points of the heat exchange surface 10 and those same areas where heat exchange is degraded, namely the upper connection 123 or the end of the first wall 120 or the second wall 122 not directly connected to the heat exchange surface 10, so as to be able to conduct more heat and thus allow to improve the exchange of heat between these areas and the heat transfer fluid 2 by convection.

[0064] Furthermore, as shown in Figure 1 and Figure 2, the elementary motif 140 is a rhombus-shaped polygon. This rhombus shape has the advantage of being the most easily reproducible polygonal shape while increasing the total heat exchange surface area in the cooling fin 12 within the available volume defined by the cavity 124.

[0065] According to one variant, it can be envisaged that the heat exchanger 14 is connected only to the first wall 120 or only to the second wall 122.

[0066] Furthermore, it is also possible to consider that the elementary motif 140 is an open polygonal motif, that is, the polygon is open along one of its sides, as shown in Figure 3, where the elementary motif 140 is a triangle with one of its sides unconnected. This configuration has the advantage of allowing an increase in the density of elementary elements 140 in the cavity 124 and an increase in the additional heat exchange surface 142 generated by the presence of the heat exchanger 14. The additional heat exchange surface 142 is thus the heat exchange surface with the heat transfer fluid 2 of the heat exchanger 14 only.

[0067] Indeed, in the plane P1, the removal of one side of the triangular elementary motif 140 has the advantage of allowing the elementary motifs 140 to be compressed along a direction of the plane P1, namely a second direction D2 according to the configuration shown in figure 3.

[0068] Therefore, a larger number of elementary motifs 140 can be envisaged in the structure of the heat exchanger 14 and the additional heat exchange surface 142 is increased, improving the heat exchange by convection with the heat transfer fluid 2.

[0069] As shown in Figure 4, it is also possible that the elementary motif 140 is hexagonal. The hexagonal shape offers the smallest perimeter for tiling space compared to other known regular polygons. Indeed, of the three regular polygons mentioned previously that can tile a space, namely cavity 124, the hexagon has the smallest perimeter. And this dimension of the hexagonal shape has the advantage of having a surface projected in the P1 plane, linked to the same wall thickness between the different shapes, the smallest, which induces a lower pressure loss compared to other types of paving.

[0070] Thus, the hexagonal shape has the advantage of optimizing the frontal surface, i.e. the surface of the heat exchanger 14 in the plane P1, of the cooling fin 12 seen from the heat transfer fluid 2 entering the cooling device 1 in the predefined flow direction, compared to the contact surface of this same heat transfer fluid 2 along its path through the cavity 124 and the cooling device 1, by optimizing the amount of material used for this implementation.

[0071] The choice of the hexagon is linked to its ability to "tile" a predefined area, namely the cavity 124 of the cooling fin 12. The area is the front surface of the heat exchanger 14 according to the plane P1 with respect to the direction of flow of the heat transfer fluid passing through the cavity 124 and the cooling fin 12.

[0072] The tiling of the cavity in the plane P1 is the way of filling a predefined area using an identical elementary pattern 140 without leaving any "holes" or unused space between the shapes, or one shape or elementary pattern overflowing into another.

[0073] Furthermore, the elementary motif 140 can also be defined by a dimension other than its perimeter. As an illustrative example, the elementary motif 140 can include a larger dimension L, as shown in Figure 4, which represents the largest length contained within the elementary motif 140 observable in the plane P1 perpendicular to the first direction D1. In the case of Figure 4, where the elementary motif 140 is a hexagonal motif, the largest length of the elementary motif can be interpreted as the length connecting two opposite vertices of the hexagon through its center.

[0074] In the case of an elementary pattern 140 whose polygonal shape includes four sides, as shown in Figure 1, the greatest length of the elementary pattern 140 is its diagonal.

[0075] And, this largest dimension L is a length less than twelve millimeters. As an indicative example, the largest length of the elementary motif 140 is between one millimeter and twelve millimeters.

[0076] Thus, it can be envisaged, thanks to the small dimensions of the elementary motifs 140, that the additional exchange surface 142 of the heat exchanger 14 represents at least a quarter of the projected surface included in the cavity 124 of the cooling fin 12 in the plane P1 perpendicular to the direction D1 of the heat transfer flow 2.

[0077] As stated previously, the elementary pattern 140 can be a simple polygonal pattern like the patterns mentioned previously or be part of a non-exhaustive list including a heptagon, an octagon or a decagon and other regular polygons.

[0078] Furthermore, with regard to elementary pattern shapes 140 with more than four sides, and preferably in a configuration with a hexagonal elementary pattern, different thermal bonding configurations can be envisaged between the heat exchange surface 10 and the additional heat exchange surface 142 of the heat exchanger 14.

[0079] Indeed, as shown in Figure 5A, it can be envisaged that one side 141 of the elementary motif of polygonal shape, and in the case of Figure 5A of hexagonal shape, is connected to the heat exchange surface 10 so as to improve the thermal bond between the heat exchanger 14 and the heat exchange surface 10.

[0080] According to a variant shown in Figure 5B, it can also be envisaged that the thermal connection between the heat exchanger 14 and the heat exchange surface 10 is made via a vertex 142'. Therefore, each elementary motif 140 connected to each other parallel to the heat exchange surface 10 is thermally connected via a side 141 improving the heat exchange between two adjacent elementary motifs 140 and thus improving the thermal conductivity of the heat exchanger 14.

[0081] As stated previously, the elementary pattern 140 can therefore be a polygonal pattern which thus includes broken sides 141 and vertices 142'.

[0082] However, it can also be envisaged, as represented in figure 6, that the elementary motif 140 includes, instead of broken vertices 142', folded vertices 142”. A broken vertex 142' thus presents an acute angle or an obtuse angle in the elementary motif 140. Conversely, a folded vertex 142” highlights a folding angle or a bending angle.

[0083] Figure 7 represents a preferred configuration of the cooling fin 12, including the heat exchanger 14, whose fractal structure exhibits an elementary polygonal pattern comprising a plurality of broken sides 141 and vertices 142'. Furthermore, the elementary pattern 140 can be likened to a snowflake-type fractal pattern. More precisely, the elementary pattern 140 of the heat exchanger 14 in Figure 7 is based on a Von Koch fractal geometry.

[0084] In other words, the elementary pattern 140 is obtained from a segment, for example a side 141, on which an elementary modification is recursively applied. Furthermore, each time the elementary modification is applied to each straight line segment, namely a side 141, the total perimeter of the elementary pattern 140 is multiplied by a predefined value. As an indicative example, this value is four-thirds.

[0085] The fact that the heat exchanger 14 includes a Von Koch snowflake fractal structure thus has the advantage of allowing the perimeter of the elementary pattern to be increased at each elementary modification step so as to increase the additional exchange surface 142 of the heat exchanger 14 and therefore to improve the heat exchange capacity between the heat exchanger 14 and the heat transfer fluid 2.

[0086] Alternatively, any other form of elementary pattern of fractal type respecting a deterministic rule can be envisaged in the heat exchanger 14. A deterministic rule is understood to mean a repeated modification on the structure of the heat exchanger leading to the generation of an identical elementary pattern 140 throughout the heat exchanger 14.

[0087] Furthermore, in order to fill the available space in cavity 124 as efficiently as possible, i.e., the surface between the first wall 120 and the second wall 122 in plane P1, the heat exchanger 14 may include a second motif elementary 144. The second elementary motif 144 is then of complementary shape and dimensions to the elementary motif 140 included in the heat exchanger 14. Thus, as an indicative example, in the configuration shown in Figure 7, the second elementary motif 144 is a star motif whose shape is complementary to the elementary motif 140 of Von Koch snowflake, which advantageously allows the second elementary motif 144 in the shape of a star between three elementary motifs 140 adjacent to each other.

[0088] Furthermore, the second elementary motif 144 can be smaller than the dimensions of the elementary motif 140, as shown in Figure 7. Indeed, the perimeter of the Von Koch snowflake-shaped elementary motif 140 is greater than the perimeter of the second star-shaped elementary motif 144.

[0089] Furthermore, as shown in Figure 8, it is possible to consider that the second elementary motif 144 is identical to the elementary motif 140. The heat exchanger 14 then comprises an elementary motif 140 and 144, but reproduced in two different dimensions. Therefore, it is also possible to consider that the dimensions of the second elementary motif 144 are half the size of the dimensions of the elementary motif 140. Thus, the perimeter of the second elementary motif 144 represents half the perimeter of the elementary motif 140. This configuration has the advantage of allowing excellent distribution of the fractal structure within the heat exchanger 14 while also facilitating its machining.

[0090] Other proportions between the elementary motif 140 and the second elementary motif 144 can also be considered.

[0091] In addition, Figure 9 represents a manufacturing process 1000 of the cooling fin 12 of Figure 7. More specifically, manufacturing process 1000 focuses on the repetitive modification of a segment or side 141 by self-similarity of shape.

[0092] The 1000 self-similarity manufacturing process is a repetition of geometric modifications following a predefined logic at different scales of the model, which is repeated on each sub-model appearing through the implementation of place of the logic of geometric modification, repeating itself on the subdivisions created by the previous step, and so on.

[0093] The general shape of the additional heat exchange surface 142 of the heat exchanger 14 is defined by a succession of mathematical and / or geometric operations applied to an original design of said heat exchanger 14.

[0094] Process 1000 includes the following steps: - A selection 1002 of a unit section 146 of the additional heat exchange surface 142 of the heat exchanger 14. This unit section 146 is a length representing, in plane P1, the projected additional heat exchange surface 142. It can be considered that this unit section 146 is a side 141 of an elementary motif 140 serving as the basis for the fabrication of a more complex fractal structure. - An angular modification 1004 of the unit section 146 of the additional heat exchange surface 142 in a first modification direction D3'. The angular modification consists of creating an isosceles triangle 148 with its major base being the unit section 146 of the selected additional heat exchange surface 142, in the first modification direction D3'. The isosceles triangle 148 then comprises two subdivided sides 148' and 148" and a height equal to the length of the unit section 146 of the selected additional heat exchange surface 142 multiplied by a predefined factor k. Therefore, the isosceles triangle 148 is open at its major base. The k factor is a value defined according to the desired angle between the two subdivided sides 148' and 148”. In addition, the value of the k factor can be fixed or can be variable. - This is followed by a selection step 1006 of one subdivided side 148' from among the two subdivided sides 148', 148”, and then an angular modification 1008 of the selected subdivided side 148' in a second modification direction D3”. According to one aspect of the invention, the second modification direction D3” may be secant or parallel to the first modification direction D3'. The major base of this new isosceles triangle 149, namely the subdivided side 148', is then opened. And similarly to steps 1006 and 1008, a selection step 1010 of the other subdivided side 148” between the two subdivided sides 148’ and 148”, and an angular modification step 1012 on the other side subdivided 148” selected in the second modification direction D3”.

[0095] Furthermore, process 1000 may also include a step of repeating the previous steps following the angular modification step 1012.

[0096] To generate a Von Koch snowflake fractal structure, the first modification direction D3' and the second modification direction D3” must intersect. However, the geometric repetition of the elementary pattern and its associated geometric modification can also be considered to obtain a Mandelbrot set, a Serpihski carpet structure, a three-dimensional Serpihski cube structure, or even a Julia set.

[0097] Alternatively, it can also be envisaged that the first direction of modification D3' and the second direction of modification D3” are parallel to each other and that the second direction of modification D3” is substantially opposite to the first direction of modification D3'.

[0098] In other words, it may be possible, through manufacturing process 1000, to generate from a straight line segment, namely unit section 146, by recursively modifying each straight line segment as follows:

[0099] By first dividing the straight segment, that is to say the unit section 146, into two segments of equal lengths, namely the two subdivided sides 148' and 148”, then constructing any triangle with the initial selected segment as its base, then removing the straight segment which was the base of the triangle when the triangle was constructed.

[0100] It is therefore possible to repeat these steps in the second modification direction D3”.

[0101] Furthermore, the number of fractal-type geometric modifications—that is, the number of repetitions of steps 1002, 1004, 1006, 1008, 1010, and 1012—can be defined in advance, for example, between one and six. The limit on the number of repetitions, or the number of applications of the geometric modification, is related to the resolution of the machine used. As this resolution increases with machine development, a greater number of repetitions will be possible in the future. The example presented is based on the current capabilities of the machines.

[0102] Furthermore, the angular modification consisting of creating the triangle can be replaced by an angular modification consisting of creating a square, for example, or a rectangle, or a right triangle, or a triangular fold generating a fold angle as previously mentioned.

[0103] As an indicative example, the heat exchange surface 10, the first wall 120, the second wall 122, the upper connection 123, or the heat exchanger 14 could be made of a metallic material. Alternatively, any material with good thermal conductivity could be considered. Alternatively, any material with good rigidity could be considered.

[0104] As an indicative example, air could be considered as the heat transfer fluid 2. Alternatively, any fluid, liquid or gaseous, with good heat extraction capacity could be considered.

[0105] The invention relates to a cooling device 1 comprising a plurality of cooling fins 12 exchanging heat by convection with a heat transfer fluid 2, thereby allowing heat extraction from the cooling device to the heat transfer fluid 2, and to a cooling fin shape comprising a heat exchanger 14 derived from a fractal-type geometric evolution through self-similarity of shape. This fractal architecture has the advantage of increasing the heat exchange surface area of ​​the cooling fin and improving heat exchange without impacting the pressure of the heat transfer fluid 2 flowing through the cooling fin 12. In other words, the invention solves the problem of increasing the heat exchange surface area to optimize heat exchange without significantly increasing the pressure losses associated with an increase in the frontal area.

[0106] The applications are related to the fields of heat exchange, typically between hot air from electronic equipment and a lower temperature water network.

[0107] In addition, operation using two heat-exchanging fluids can also be considered.

[0108] The invention makes it possible to increase the efficiency of exchanges between these two fluids without constraining either one in terms of pressure losses.

[0109] It can also be used to cool an electronic component, through the shape of the fins used for heat dissipation to a fluid such as water or air.

[0110] As an indicative example, the means of producing such a cooling fin 12 and such a heat exchanger 14 including the fractal structure can be 3D printing, preferably metallic.

[0111] Extracting these profiles using metal extrusion dies is also a possibility.

Claims

AMENDED CLAIMS received by the International Bureau on April 4, 2024 (04.04.2024) 1. Cooling device (1) comprising at least one cooling fin (12), the device being configured to allow circulation of a heat transfer fluid (2) along the at least one cooling fin in a first direction (D1), a heat exchange being able to take place by convection between the at least one cooling fin (12) and the heat transfer flow (2), the cooling fin (12) comprising: A heat exchange surface (10) configured to allow heat exchange with the heat transfer fluid (2), A first wall (120) and a second wall (122), the first wall (120) and the second wall (122) extending along a plane substantially parallel to the first direction (D1) and substantially perpendicular to the heat exchange surface (10), A cavity (124) between the first wall (120) and the second wall (122), the heat transfer fluid (2) circulating in the cavity (124), A heat exchanger (14) included in the cavity (126) and connected to the heat exchange surface (10), the heat exchanger (14) having a fractal structure along a plane perpendicular (P1) to the first direction (D1) of the heat transfer fluid (2), the heat exchanger (14) comprising a repetition of an elementary pattern (140).

2. Cooling device (1) according to claim 1, wherein the heat exchanger (14) is connected to the first wall (120) and to the second wall (122).

3. Cooling device (1) according to claims 1 or 2, wherein the heat exchanger (14) is configured to maximize the heat exchange surface (10).

4. Cooling device (1) according to one of claims 1 to 3, in which the elementary pattern (140) comprises a broken vertex (142'). 23 AMENDED SHEET (ARTICLE 19) 5. Cooling device (1) according to one of claims 1 to 4, in which the elementary pattern (140) comprises a largest dimension less than 12 millimeters.

6. Cooling device (1) according to one of claims 1 to 4, in which the elementary pattern (140) comprises a folded top (142”).

7. Cooling device (1) according to one of claims 1 to 6, wherein the heat exchanger (14) comprises a second elementary pattern (144), the second elementary pattern (144) being of dimensions smaller than the dimensions of the elementary pattern (140).

8. Cooling device (1) according to one of claims 1 to 7, in which the heat exchanger (14) comprises an additional exchange surface (142), the additional exchange surface (142) representing at least a quarter of the surface area included in the cavity (124) of the cooling fin (12) along the plane (P1) perpendicular to the direction (D1) of the heat transfer fluid (2).

9. Cooling device (1) according to one of claims 1 to 8, in which the elementary pattern (140) is a polygonal pattern.

10. Cooling device (1) according to claim 9, wherein the polygonal pattern is open along at least one side of the polygonal pattern.

11. Cooling device (1) according to one of claims 1 to 10, in which the second elementary pattern (144) is a pattern identical to the elementary pattern (140).

12. Cooling device (1) according to claim 11, wherein the dimensions of the second elementary pattern (144) are half the dimensions of the elementary pattern (140).

13. Cooling device (1) according to one of claims 1 to 12, wherein the heat exchanger (14) comprises a self-similar fractal structure.

14. Method for manufacturing (1000) a cooling fin (12) of a cooling device (1) according to one of the preceding claims, the heat exchanger (14) comprising an additional heat exchange surface (142), the method comprising the following steps: 24 AMENDED SHEET (ARTICLE 19) Selection (1002) of a unit section (146) of the additional exchange surface (142) of the heat exchanger (14), Angular modification (1004) of the unit section (146) of the additional exchange surface (142) in a first modification direction (D3'), the angular modification consisting of a creation of an isosceles triangle (148) of large base the unit section (146) of the additional exchange surface (142) selected, in the first modification direction (D3'), the isosceles triangle (148) comprising two subdivided sides (148', 148”) and of height equal to the length of the unit section (146) of the additional exchange surface (142) selected multiplied by a predefined factor k, the isosceles triangle (148) being open on the large base, Selection (1006) of a subdivided side (148') from the two subdivided sides (148', 148”), Angular modification (1008) of the subdivided side (148') selected in a second modification direction (D3”) secant to the first modification direction (D3'), Selection (1010) of the other subdivided side (148”) from the two subdivided sides (148', 148”), Angular modification (1012) of the other subdivided side (148”) selected in the second modification direction (D3”), Repeat the previous steps.

15. Method of manufacturing (1000) a cooling fin (12) according to the preceding claim, in which the second modification direction (D3”) is substantially opposite to the first modification direction (D3'). 25 AMENDED SHEET (ARTICLE 19)

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