Fin architecture 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 circulation of a heat transfer fluid (2) along the at least one cooling fin (12) in a first direction (D1), heat exchange being able to occur by convection between the at least one cooling fin (12) and the heat transfer fluid (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 in a plane substantially parallel to the first direction (D1) and substantially perpendicular to the heat exchange surface (10), A cavity (124) included between the first wall (120) and the second wall (122),The heat transfer fluid (2) circulating in the cavity (124), A heat exchanger (14) contained within the cavity (124) and connected to the heat exchange surface (10), the heat exchanger (14) having a fractal structure along a plane (P1) perpendicular to the first direction (D1) of the heat transfer fluid (2). Figure for the abbreviation: Fig. 1,

Description

Title of the invention: Fin architecture promoting heat exchange

[0001] The invention relates to the cooling of a heat-producing element. The invention finds an application in the field of electrical machines and power electronics. Indeed, it is known that electronic equipment, computers, and electronics in general generate losses which result in the production of heat which must be evacuated. The evacuation of this heat, ensuring proper operation of the elements mentioned above, therefore becomes a priority. The invention finds a particular application in the field of on-board electronics where the trend is to increase the number of electrical equipment and therefore the on-board 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, making it possible to evacuate heat from the elements dissipating thermal energy to a source of evacuation of this heat, in order to allow this electronics to operate in optimal conditions.

[0004] Heat exchangers are now known comprising a set of fins arranged in an axis of movement of a heat transfer flow for which heat exchange with a second fluid or the thermal element itself is desired, for example straight fins in the direction of an air flow passing through the heat exchanger using the fins to extract thermal energy towards 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 elements mentioned, namely the two heat-transfer fluids or the fluid and the solid element.

[0006] The use of a single heat transfer flow sweeping the heat exchanger is however preferred for reasons of compactness and weight. Indeed, the addition of a second heat transfer fluid and the entire circuit allowing the circulation of this second fluid often generates an excess of mass and volume which it becomes necessary to take into consideration, especially in the field of aeronautics in which the main problem is the management of the mass of the vehicle.

[0007] Consequently, the cooling of an electrical machine is today limited by mass and size constraints that the state of the art is not capable of overcoming.

[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 methods for producing such fins are stamping or folding, which limits the shapes, and therefore the performance of the heat exchanges.

[0011] Thus, it is currently difficult, or even impossible, for technical and manufacturing reasons, to improve this heat exchange at the level of the exchange surface of the fins of the heat exchanger.

[0012] The invention aims to overcome all or part of the problems mentioned above by proposing fin shapes making it possible to increase the exchange surface between the heat source, namely the solid element, and a heat transfer fluid sweeping the heat exchanger, allowing the transfer of thermal energy. This geometric development has the advantage of increasing the heat exchange surface, making it possible to improve the heat exchange, while limiting a possible pressure drop of the flow or heat transfer fluid passing through the heat exchanger, leading to a reduction in the 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 the at least one cooling fin in a first direction, a heat exchange being able to take place by convection between the at least one cooling fin and the heat transfer 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, the heat transfer fluid circulating in the cavity, - A heat exchanger included in 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 to the second wall.

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

[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 pattern comprises a largest dimension less than 12 millimeters.

[0018] According to one aspect of the invention, the heat exchanger comprises an additional exchange surface, the additional exchange surface representing at least a quarter of the surface 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 pattern comprises a broken vertex.

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

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

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

[0025] According to one aspect of the invention, the dimensions of the second elementary pattern are less than half the dimensions of the elementary pattern.

[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 of manufacturing a cooling fin of the heat exchanger comprising an additional heat exchange surface, the method comprising the following steps: - Selection of a unit section of the additional 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 a creation of an isosceles triangle of large base the unit section of the selected additional exchange surface, in the first direction of modification, the isosceles triangle comprising two subdivided sides and of 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 large base, - Selection of one subdivided side from the two subdivided sides, - Angular modification of the selected subdivided side in a second modification direction intersecting the first modification direction, - Selection of the other subdivided side from the two subdivided sides, - Angular modification of the other selected subdivided side in the second modification direction, - Repeat the previous steps.

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

[0029] The invention will be better understood and other advantages will appear on reading the detailed description of an embodiment given by way of example, a description illustrated by the attached drawings in which:

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

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

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

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

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

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

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

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

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

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

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

[0041] [Fig.l] represents 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 circulation of a heat transfer fluid 2 along the at least one cooling fin 12 in a first direction DI of flow of the heat transfer fluid 2. Thus, a heat exchange can take place by convection between the cooling fin 12 and the heat transfer flow 2. In a preferred configuration of the invention, as shown in [Fig.l], the first direction DI of flow of the heat transfer fluid 2 is parallel to the direction in which the cooling fin 12 develops. In other words, the heat transfer fluid 2, which moves parallel to the first direction Dl, passes perpendicularly through the cooling fin 12 in a plane PI perpendicular to the first direction Dl 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 while the heat exchange is less efficient, in comparison with the heat exchange by convection between the heat transfer fluid 2 located in direct proximity to 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 direction of development 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 comprises 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 making it possible to distribute the heat over the entire heat exchange surface by conduction in order to allow a heat exchange zone with the heat transfer fluid 2 along the entire length of the cooling fin 12. The heat exchange surface 10 is thus a hot body which needs to discharge a quantity of heat while the heat transfer fluid 2 is a cold body whose function is to exchange with the heat exchange surface 10 and to extract heat. The heat exchange surface 10 advantageously comprises a thermally conductive material.And, this heat is transmitted from the heat exchange surface 10 to the heat transfer fluid 2 which passes through the cooling fin 12 by convection so as to evacuate the heat from the cooling device 1, this heat exchange occurring mainly along the heat exchange surface 10 and in the vicinity of the heat exchange surface 10.

[0045] The cooling fin also comprises a first wall 120 and a second wall 122 extending substantially parallel to the first direction D1. and along a plane substantially parallel to the first direction DI and substantially perpendicular to the heat exchange surface 10. The first wall 120 and the second wall 122 are thus the supporting structure of the cooling fin 12.

[0046] In addition, the cooling fin comprises a cavity 124 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, passes through the cooling fin 2 between the first wall 120 and the second wall 122 in a manner substantially parallel to the first direction DI.

[0047] It may 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 [Fig.l]. Therefore, the first wall 120 is connected to the second wall 122 by means 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 by means of the heat exchange surface 10. Consequently, the upper connection 123 is no longer represented and the cavity communicates with a medium 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 heat transfer fluid 2, takes place efficiently along the heat exchange surface 10 and in the vicinity of the heat exchange surface 10. And, this efficiency of the heat exchange between the heat exchange surface 10 and the heat transfer fluid 2 decreases proportionally with respect to the distance between the heat transfer fluid 2 and the heat exchange surface 10.

[0050] Thus, advantageously, the cooling fin 12 comprises a heat exchanger 14 included in the cavity 124 and connected to the heat exchange surface 10. The heat exchanger 14 comprises a fractal structure represented in the plane PI 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 the heat exchange surface 10. In other words, the heat exchanger 14 is an additional heat exchange surface compared to the heat exchange surface 10 so as to also allow heat exchange by convection between the heat transfer fluid 2 and the heat exchanger 14. Indeed, the heat exchanger 14 also has a good conduction capacity so that the heat included in the heat exchange surface 10 can be conducted into the heat exchanger 14. Therefore, the exchange by convection no longer takes place 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 heat exchange by convection is thus improved.

[0052] Thus, the heat exchanger 14 comprises within its structure a repetition of a simple elementary pattern 140. In the configuration of [Fig.l], this elementary pattern 140 is a diamond 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 in the cavity 124. In other words, the fractal structure of the heat exchanger 14 is a structure fragmented by means of the elementary pattern 140.

[0054] Furthermore, the heat exchanger 14 also has the advantage, in addition to increasing the heat exchange surface with the heat transfer fluid 2 and improving the heat exchange with the heat transfer fluid 2, of not impacting the heat transfer fluid 2 passing through the cooling fin. Indeed, positioning an object so as to face the movement of the heat transfer fluid 2 in the first direction DI generally induces a deviation of the movement of the heat transfer fluid 2, a loss of the flow rate of the heat transfer fluid 2 in the cooling fin and overall a pressure drop. On a macroscopic scale, this reduction in the charge of the heat transfer fluid 2 passing through the cooling fin 12 and the heat exchanger 14 then results in a reduction in the flow rate of the heat transfer fluid 2 passing through the cavity 124 in particular.Therefore, 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 the heat exchange without impacting, or with a slight impact, on the load linked 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 weak 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 makes it possible, via the heat exchanger 14, to increase the overall heat exchange surface 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 means, for example, of the upper connection 123.

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

[0059] Furthermore, it may also be envisaged that the first wall 120 and / or the second wall 122 are heat conductors from the heat exchange surface 10. Therefore, the overall heat exchange surface in the cooling fin is composed 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 the 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 exchanger is. However, this is also the case for the conduction between the heat exchange surface 10 which is the hot body and, for example, the upper connection 123 or even an end of the first wall 120 or of 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 even 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 then not fully transmitted and the upper connection 123 or the end of the first wall 120 or of 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 makes it possible, by means of its fractal structure, to generate several thermal paths between different points of the heat exchange surface 10 and these same zones where the heat exchange is degraded, namely the upper connection 123 or the end of the first wall 120 or of the second wall 122 not directly connected to the heat exchange surface 10, so as to be able to conduct more heat and therefore to make it possible to improve the heat exchange between these zones and the heat transfer fluid 2 by convection.

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

[0065] According to a variant, it may 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 can also be envisaged that the elementary pattern 140 is an open polygonal pattern, that is to say that the polygon is open along one of its sides, as shown in [Fig. 3], where the elementary pattern 140 is a triangle of which one of its sides is not connected. This configuration has the advantage of making it possible to increase the density of elementary elements 140 in the cavity 124 and to increase 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 PI, the removal of the same side of the elementary pattern 140 of triangular shape has the advantage of making it possible to compress the elementary patterns 140 in a direction of the plane PI, namely a second direction D2 according to the configuration shown in [Fig.3].

[0068] Therefore, a greater number of elementary patterns 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 [Fig.4], it can also be envisaged that the elementary pattern 140 is hexagonal in shape. The hexagonal shape offers the smallest perimeter for filling space compared to the other known regular polygons. Indeed, of the three regular polygons mentioned above for paving a space, namely the cavity 124, the hexagon is the one which offers the smallest perimeter. And, this dimension of the hexagonal shape has the advantage of having a projected surface in the plane PI, linked to the same wall thickness between the different shapes, the smallest, which induces a lower pressure loss compared to the other types of paving.

[0070] Thus, the hexagonal shape has the advantage of optimizing the frontal surface, that is to say the surface of the heat exchanger 14 in the plane PI, of the cooling fin 12 seen from the heat transfer fluid 2 entering the cooling device 1 in the predefined flow direction, relative 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 quantity of material used for this implementation. artwork.

[0071] The choice of the hexagon is linked to its capacity to “paving” a predefined zone, namely the cavity 124 of the cooling fin 12. The zone is the front surface of the heat exchanger 14 along the plane PI relative 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 PI plane is the way of filling a predefined area using an identical elementary pattern 140 without this leaving "holes" or unused space between the shapes, or overflow of one shape or elementary pattern onto the other.

[0073] Furthermore, the elementary pattern 140 may also be defined by a dimension other than its perimeter. As an indicative example, the elementary pattern 140 may comprise a largest dimension L, as shown in [Fig. 4], which represents the largest length included in the elementary pattern 140 observable in the plane PI perpendicular to the first direction DI. In the case of [Fig. 4], for which the elementary pattern 140 is a hexagonal pattern, the largest length of the elementary pattern may be interpreted as the length connecting two opposite vertices of the hexagon passing through the center of the hexagon.

[0074] In the case of an elementary pattern 140 whose polygonal shape comprises four sides, as shown in [Fig.l], 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 pattern 140 is between one millimeter and twelve millimeters.

[0076] Thus, it can be envisaged, thanks to the small dimensions of the elementary patterns 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 PI perpendicular to the direction DI of the heat transfer flow 2.

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

[0078] Furthermore, concerning the shapes of elementary pattern 140 with more than four sides, and preferably in a configuration with a hexagonal elementary pattern, different thermal connection 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 [Fig.5A], it can be envisaged that one side 141 of the elementary pattern of polygonal shape, and in the case of [Fig.5A] of hexagonal shape, is connected to the heat exchange surface 10 so as to improve the thermal connection between the heat exchanger 14 and the heat exchange surface 10.

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

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

[0082] Nevertheless, it can also be envisaged, as shown in [Fig.6], that the elementary pattern 140 comprises, instead of the broken vertices 142', folded vertices 142”. A broken vertex 142' thus presents an acute angle or an obtuse angle in the elementary pattern 140. Conversely, a folded vertex 142” highlights a folding angle or a crease angle.

[0083] [Fig. 7] represents a preferred configuration of the cooling fin 12 comprising the heat exchanger 14 whose fractal structure has an elementary pattern of polygonal shape 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 of [Fig. 7] is based on a Von Koch-type 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 applied recursively. In addition, 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 comprises a Von Koch flake type fractal structure thus has the advantage of making it possible to increase the perimeter of the elementary pattern 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. By deterministic rule is understood a repeated modification on the structure of the exchanger thermal leading to the generation of an identical elementary pattern 140 throughout the entire heat exchanger 14.

[0087] Furthermore, in order to fill as best as possible the space available in the cavity 124, that is to say the surface between the first wall 120 and the second wall 122 in the plane PI, the heat exchanger 14 may comprise a second elementary pattern 144. The second elementary pattern 144 is then of a shape and dimensions complementary to the elementary pattern 140 included in the heat exchanger 14. Thus, as an indicative example, in the configuration shown in [Fig.7], the second elementary pattern 144 is a star pattern whose shape is complementary to the Von Koch flake elementary pattern 140, which advantageously makes it possible to position the second elementary pattern 144 in the form of a star between three elementary patterns 140 adjacent to each other.

[0088] Furthermore, the second elementary pattern 144 may be of smaller dimensions than the dimensions of the elementary pattern 140, as shown in [Fig.7]. Indeed, the perimeter of the elementary pattern 140 in the form of a Von Koch snowflake is of greater value than the perimeter of the second elementary pattern 144 in the form of a star.

[0089] Furthermore, it may be envisaged, as shown in [Fig.8], that the second elementary pattern 144 is a pattern identical to the elementary pattern 140. The heat exchanger 14 then comprises an elementary pattern 140 and 144 but reproduced according to two different dimensions. Therefore, it may also be envisaged that the dimensions of the second elementary pattern 144 are less than half compared to the dimensions of the elementary pattern 140. Thus, the perimeter of the second elementary pattern 144 represents half the perimeter of the elementary pattern 140. This configuration has the advantage of allowing an excellent distribution of the fractal structure in the heat exchanger 14 while facilitating the machining of the heat exchanger 14.

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

[0091] Further, [Fig.9] shows a manufacturing method 1000 of the cooling fin 12 of [Fig.7]. More specifically, the manufacturing method 1000 focuses on repetitively modifying a segment or side 141 by shape self-similarity.

[0092] The manufacturing method 1000 by self-similarity is a repetition of geometric modification following a predefined logic at the different scales of the model, this being repeated on each sub-model appearing by the implementation of the geometric modification logic, being repeated 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 layout of said heat exchanger 14.

[0094] The method 1000 comprises the following steps: - A selection 1002 of a unit section 146 of the additional exchange surface 142 of the heat exchanger 14. This unit section 146 is a length representing in the plane PI the projected additional heat exchange surface 142. It can be envisaged that this unit section 146 is a side 141 of an elementary pattern 140 serving as a basis for the manufacture of a more complex fractal structure. - An angular modification 1004 of the unit section 146 of the additional exchange surface 142 in a first modification direction D3'. The angular modification consists of creating an isosceles triangle 148 with a large base, the unit section 146 of the additional exchange surface 142 selected, 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 additional exchange surface 142 selected multiplied by a predefined factor k. From then on, the isosceles triangle 148 is open on the large base.

[0095] The factor k is a value defined as a function of the desired angle between the two subdivided sides 148' and 148”. Furthermore, the value of the factor k can be defined in a fixed manner or can be variable. - This is followed by a step 1006 of selecting a subdivided side 148' from among the two subdivided sides 148', 148”, 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 large base of this new isosceles triangle 149, namely the subdivided side 148', is then open.

[0096] And similarly to steps 1006 and 1008, a selection step 1010 of the other subdivided side 148” from among the two subdivided sides 148' and 148”, and an angular modification step 1012 of the other subdivided side 148” selected in the second modification direction D3”.

[0097] In addition, the method 1000 may also comprise a step of repeating the preceding steps following the angular modification step 1012.

[0098] In order to generate a Von Koch snowflake-type fractal structure, the first modification direction D3' and the second modification direction D3” are intersecting with each other. However, the geometric repetition of the elementary pattern and the related geometric modification can also be considered to obtain a Mandelbrot set, a Serpihski carpet structure or a three-dimensional Serpihski cube structure or even a Julia set.

[0099] Alternatively, it may also be envisaged that the first modification direction D3' and the second modification direction D3” are parallel to each other and that the second modification direction D3” is substantially opposite to the first modification direction D3'.

[0100] In other words, it may be envisaged, by means of the manufacturing method 1000, to generate from a straight line segment, namely the unit section 146, by recursively modifying each straight line segment in the following manner:

[0101] By first dividing the straight line segment, i.e. the unit section 146, into two segments of equal length, namely the two subdivided sides 148' and 148”, then by constructing any triangle having as its base the initial segment selected, then by deleting the straight line segment which was the base of the triangle when constructing the triangle.

[0102] It is thus possible to repeat these steps in the second modification direction D3”.

[0103] Furthermore, the number of geometric modifications of fractal type, that is to say the number of repetitions of steps 1002, 1004, 1006, 1008, 1010 and 1012, can be defined in advance, and for example between one and six. The limit of the number of repetitions or number of geometric modification applications is linked to the resolution fineness of the machine used. This resolution increasing with the evolution of the machines, a greater number of repetitions is possible in the future. The example presented is linked to the current capacities of the machines.

[0104] Furthermore, the angular modification consisting of the creation of the triangle can be replaced by an angular modification consisting of the creation of a square for example or even a rectangle or even a right triangle or even a triangular folding generating a fold angle as mentioned previously.

[0105] As an indicative example, it may be envisaged that the heat exchange surface 10, the first wall 120, the second wall 122, the upper connection 123 or the heat exchanger 14 are obtained from a metallic material. Alternatively, any material having good thermal conductivity may be envisaged. Alternatively, any material having good rigidity may be envisaged.

[0106] As an indicative example, it may be envisaged that the heat transfer fluid 2 is air. Alternatively, any fluid, liquid or gaseous, having a good thermal extraction capacity may be envisaged. Alternatively, any fluid may be envisaged.

[0107] The invention therefore relates to a cooling device 1 comprising a plurality of cooling fins 12 exchanging by convection with a heat transfer fluid 2 so as to allow heat extraction from the cooling device in the direction of the heat transfer fluid 2 and to a cooling fin shape comprising a heat exchanger 14 deduced from a geometric evolution of fractal type by self-similarity of shape. This fractal architecture has the advantage of to increase the heat exchange surface area of ​​the cooling fin and improve the heat exchange without impacting the load of the heat transfer fluid 2 which passes through the cooling fin 12. In other words, the invention solves the problem linked to the increase in the heat exchange surface area to optimize the heat exchange without significantly increasing the load losses linked to an increase in the frontal surface area.

[0108] The applications are related to the fields of heat exchange, typically between hot air coming from electronic equipment and a water network at a lower temperature.

[0109] Furthermore, operation from two fluids exchanging heat can also be envisaged.

[0110] The invention makes it possible to increase the efficiency of exchanges between these two fluids without constraining one or the other in terms of pressure losses.

[0111] It can also be used to allow the cooling of an electronic component, by the shape of the fins used for heat dissipation towards a fluid such as water or air.

[0112] As an indicative example, the means of producing such a cooling fin 12 and such a heat exchanger 14 comprising the fractal structure may be 3D printing, preferably metallic.

[0113] Extraction of these profiles by metal extrusion dies is also possible.

Claims

Claims

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 (Dl), a heat exchange being able to take place by convection between the at least one cooling fin (12) and the heat transfer fluid (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 in a plane substantially parallel to the first direction (Dl) 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 (PI) to the first direction (Dl) of the heat transfer fluid (2), the heat exchanger (14) comprising a repetition of an elementary pattern (140), the heat exchanger (14) further comprising a second elementary pattern (144) having a shape and dimensions complementary to the shape and dimensions of the elementary pattern (140).,

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

3. Cooling device (1) according to claim 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, wherein the elementary pattern (140) comprises a largest dimension less than 12 millimeters.

5. Cooling device (1) according to one of claims 1 to 4, in which the elementary pattern (140) comprises a broken vertex (142').

6. Cooling device (1) according to claim 1 to 4, wherein the elementary pattern (140) comprises a folded top (142”).

7. Cooling device (1) according to one of claims 1 to 6, in which the second elementary pattern (144) is 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 (PI) perpendicular to the direction (Dl) 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. A 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. A method of 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: 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') among 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”) among 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. A method of manufacturing (1000) a cooling fin (12) according to the preceding claim, wherein the second modification direction (D3”) is substantially opposite to the first modification direction (D3').

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