WO2024012963A1

WO2024012963A1 - Heatsink for electrical equipment

Info

Publication number: WO2024012963A1
Application number: PCT/EP2023/068624
Authority: WO
Inventors: Michel Fakes; Cédric DE-VAULX; Erwan ETIENNE; Kamel Azzouz
Original assignee: Valeo Equipements Electriques Moteur
Priority date: 2022-07-13
Filing date: 2023-07-05
Publication date: 2024-01-18
Also published as: FR3138021A1

Abstract

The invention relates to a heatsink comprising: - an inlet and an outlet for heat-transport fluid, - an exchange surface extending between the inlet and the outlet and intended to exchange heat with the heat-transport fluid, comprising an inlet zone, an outlet zone and at least one intermediate zone, all the zones of the exchange surface having the same surface area, - a plurality of fins projecting from said exchange surface in each of the zones and having a leading edge, a trailing edge, and an angle of incidence measured between the shortest distance segment that connects the leading edge to the trailing edge and the main direction of the fluid, wherein the fins in the inlet, intermediate and outlet zone respectively have a mean inlet, intermediate and outlet angle of incidence, the mean inlet angle of incidence being smaller than the mean intermediate angle of incidence, which is smaller than the mean outlet angle of incidence.

Description

Title of the invention: HEAT SINK FOR ELECTRICAL EQUIPMENT

Technical field of the invention

The present invention relates to the field of electrical equipment, in particular electrical machines and power electronics such as power converters, for electric or hybrid vehicles and which must be cooled by a heat transfer fluid.

The present invention relates more particularly to heat sinks used to cool said electrical equipment and involving heat transfer, such as heat elimination, absorption and/or dissipation.

Technology background

It is known from the prior art that the temperature of electrical equipment rises during its operation. The increase in temperature will then cause significant damage to the electrical equipment.

For example, in a rotating electrical machine, electrical energy is converted into kinetic energy or vice versa. The losses that occur lead to heating of the components of the electrical machine during operation. In order to avoid excessive heating of its components, such as the stator and the rotor, a heat sink, which can also be called a cooling device, must be provided in the electrical machine. The heat generated by the circulation of current through the stator winding can be evacuated by a heat sink, such as a cooling chamber provided in the bearing and in which a heat transfer fluid circulates. It is known from document US8629587 that the cooling chamber extends in the circumferential direction of the stator and that fins protrude from a surface of the cooling chamber inside said chamber so as to allow more efficient cooling.

In the case of power electronics, for example for an inverter, power modules will rise in temperature during their operation. The increase in temperature will cause significant damage to the module itself and to the other elements of the electrical assembly. To limit these thermal effects, it is known to use a power electronics cooling circuit. The cooling circuit is arranged under or on the power modules as disclosed in document EP3902382. In this document, tubular shaped reliefs project from the exchange surface.

The addition of reliefs makes it possible to increase the exchange surface in order to obtain higher heat transfer and therefore improved cooling. It should be noted, however, that the cooling requirements are not the same between the input and output of a heat sink. Indeed, in the documents cited, as the arrangement of the reliefs is the same throughout the exchange surface of the heat sink, the heat transfer coefficient is constant. Due to the natural heating of the heat transfer fluid between the inlet and outlet of the heat sink, the heat exchange capacity decreases and generates an inhomogeneous temperature pattern.

The invention aims to remedy the problems mentioned above by proposing a heat sink which generates a homogeneous temperature model.

Summary of the invention

The present invention thus aims to provide a heat sink, in particular for electrical equipment, comprising:

- an inlet and an outlet for heat transfer fluid,

- an exchange surface extending between the inlet and the outlet and intended to exchange thermally with the heat transfer fluid, said surface comprising an inlet zone communicating with the fluid inlet, an outlet zone communicating with the outlet of fluid and at least one intermediate zone arranged between the inlet zone and the outlet zone, all zones of the exchange surface having an identical area,

- a plurality of fins projecting from said exchange surface in each of the zones, each fin has a leading edge, a trailing edge and an angle of incidence measured between the segment of smallest distance which connects the edge leading edge at the trailing edge and the main direction of the heat transfer fluid between the inlet and the outlet, in which the fins of the inlet, intermediate and outlet zone respectively have an average inlet, intermediate angle of incidence and exit, said average entry angle of incidence being less than the intermediate average angle of incidence which is less than the average exit angle of incidence. By thus modifying the geometric design parameters between the fluid inlet and outlet, the turbulence generated will be greater as will the heat exchange coefficient. The invention thus makes it possible, via this arrangement, to adapt the heat exchange coefficient along the exchange surface of the heat sink (the heat exchange coefficient being greater in the outlet zone than in the exit zone). inlet) with the heat transfer fluid so as to obtain a uniform temperature between the inlet and outlet.

In the present invention, the term “electrical equipment” is intended to mean electrical machines and power electronics.

In a manner known per se, electrical machines, in particular rotating electrical machines, comprise a stator and a rotor secured to a shaft. The rotor may be integral with a driving and/or driven shaft and may belong to a rotating electric machine in the form of an alternator, an electric motor, or a reversible machine capable of operating in both modes.

In certain types of motor vehicle powertrains, a high-power reversible rotating electric machine is coupled to the gearbox of the vehicle or to a train of the motor vehicle. The electric machine is then able to operate in an alternator mode to supply energy in particular to the battery and/or to the vehicle's on-board network, and in an engine mode, not only to ensure the starting of the thermal engine, but also to participate in the traction of the vehicle alone or in combination with the thermal engine.

Power electronics refers, for example, to power converters (on-board chargers, DC/DC converters, inverters) comprising power modules making it possible to receive or provide an electrical power signal to the electrical phases of the winding of an electrical machine. In the case for example of an inverter, the power module forms a voltage rectifier bridge to transform the alternating voltage generated by the phases of the stator into a direct voltage and/or, conversely, to transform a direct voltage into an alternating voltage to power the phases of the stator. The inverter also includes a control part comprising a control module making it possible in particular to regulate the voltage injected into the rotor and to interface with an external computer of the vehicle.

The heat sink is therefore configured to dissipate the heat emitted by the electrical equipment. The principal direction of the fluid should be seen as the direction of the shortest path traveled by the fluid between the fluid inlet and fluid outlet.

By “average angle of incidence of a zone”, we mean the sum of the angles of incidence of the fins of a zone divided by the number of fins of this zone.

Advantageously, the leading edge and the trailing edge of each fin are in contact with the heat exchange surface.

Advantageously, the angle of incidence is included in a plane parallel to the exchange surface.

In the context of the present invention, in each zone, a plurality of fins protrude.

Advantageously, all the fins in the same zone have the same angle of incidence.

Advantageously, the fins are of parallelepiped, ellipsoidal or substantially ellipsoidal shape. By “substantially ellipsoidal” is meant a fin comprising at least one ellipsoidal part.

Advantageously, the fins of the inlet zone have a maximum angle of incidence which is less than the smallest angle of incidence of the fins of the intermediate zone and the fins of the intermediate zone have a maximum angle of incidence which is lower at the smallest angle of incidence of the fins of the fins of the exit zone.

Advantageously, the fins extend respectively over an average inlet, intermediate and outlet height in the inlet, intermediate and outlet zone and the average inlet height of the fins is less than the average intermediate height of the fins which is lower than the average fin outlet height.

This thus makes it possible, via an increasing average height of the fins between the inlet zone and the outlet zone, to adapt the heat exchange coefficient along the exchange surface of the heat sink with the heat transfer fluid so as to obtain a uniform temperature between the inlet and outlet. By increasing the average height of the fins, the contact surface between the heat transfer fluid and the heat sink increases as well as the heat exchange coefficient.

Each fin extends over a height between a base arranged on the exchange surface from which the fin projects and a peak. By “average height of the fins of a zone”, we mean the sum of the heights of the fins of a zone divided by the number of fins of this zone.

Advantageously, all the fins in the same zone extend to the same height. Thus the average height of the fins of a zone corresponds to the height of any fin of this same zone.

Advantageously, the fins of the inlet zone have a maximum height which is less than the smallest height of the fins of the intermediate zone and the fins of the intermediate zone have a maximum height which is less than the smallest height of the fins of the exit area.

Advantageously, the number of fins in the inlet zone is less than the number of fins in the intermediate zone which is less than the number of fins in the outlet zone. This arrangement makes it possible to adapt the heat exchange coefficient along the exchange surface of the heat sink (the heat exchange coefficient being greater in the outlet zone than in the inlet zone) with the fluid heat carrier so as to obtain a uniform temperature between the inlet and outlet. By increasing the number of fins, the contact surface between the heat transfer fluid and the heat sink increases as well as the heat exchange coefficient. Additionally, the fins increase heat transfer efficiency by transforming laminar flow into turbulent flow.

A fin has both the hydraulic resistance function and the thermal device function. Hydraulic resistance corresponds to the pressure loss experienced by the heat transfer fluid inside the heat sink. The greater the number of fins on the exchange surface of the heat sink, the greater the pressure loss and therefore the hydraulic resistance. The thermal device aims to increase the contact surface with the heat transfer fluid to increase convective exchanges, and therefore heat transfer. The fin is advantageously thermally conductive.

Advantageously, all the fins in the same zone have an identical shape.

Advantageously, the shape of the fins varies from one area to another.

Advantageously, the fins project radially from the exchange surface.

Advantageously, the fins are made in one piece with the exchange surface from which they project. Advantageously, the exchange surface has a flat surface, preferably rectangular in shape. Alternatively, the exchange surface may have a circumferential shape.

Advantageously, the exchange surface is formed from a solid thermally conductive material, for example steel, aluminum or copper.

Advantageously, the heat sink comprises an additional exchange surface, preferably arranged opposite the exchange surface, and which extends between the inlet and the outlet and intended to exchange thermally with the heat transfer fluid, said additional surface comprising an inlet zone communicating with the fluid inlet, an outlet zone communicating with the fluid outlet and at least one intermediate zone arranged between the inlet zone and the outlet zone, all zones of the surface d additional exchange having an identical area.

Advantageously, a plurality of additional fins project from said additional exchange surface in each of the zones, and

- in each of the zones said additional fins extend respectively over an average entry, intermediate and exit height in the entry, intermediate and exit zone, the average entry height of the additional fins being less than the height intermediate average which is less than the average exit height and/or

- the number of additional fins in the entry zone is less than the number of additional fins in the intermediate zone which is less than the number of additional fins in the exit zone and/or

- each additional fin has a leading edge, a trailing edge and an angle of incidence measured between the segment of smallest distance which connects the leading edge to the trailing edge and the main direction of the heat transfer fluid between the entry and exit, the additional fins of the entry, intermediate and exit zone respectively have an average entry, intermediate and exit angle of incidence, said average entry angle of incidence being less than the intermediate mean angle of incidence which is less than the mean exit angle of incidence.

The two surfaces thus form, at least in part, a cooling chamber in which the heat transfer fluid flows. One of the surfaces being an interior surface and the other, the outer surface relative to the electrical equipment that the heat sink cools.

The fins project from one of the exchange surface or the additional exchange surface towards the other exchange surface without reaching the latter.

Advantageously, the heat transfer fluid can be liquid or gaseous. Preferably, the heat transfer fluid is water, for example brine, oil or air.

The invention also relates to a machine assembly comprising electrical equipment and a heat sink according to the invention. Preferably, the electrical equipment is chosen from electrical machines and power electronics. Power electronics refers, for example, to power converters such as on-board chargers, DC/DC converters, inverters.

The invention also relates to the use of the machine assembly according to the invention in a motor vehicle.

Brief description of the figures

The invention will be better understood on reading the following description and examining the accompanying figures. These figures are given for illustrative purposes only but in no way limit the invention.

[Fig. 1] is a perspective view of a machine assembly (heat sink + power electronics) according to the invention.

[Fig. 2] is a top view of a part of the heat sink according to a first embodiment.

[Fig. 3] is a top view of a part of the heat sink according to a second embodiment.

[Fig. 4] is an enlargement of a first form of cooling fin of the heatsink of Figure 2 or 3.

[Fig. 5] represents a second form of fin that can be used in the present invention.

[Fig. 6] is a perspective view of part of the heat sink showing varying fin height. [Fig. 7] is a view in a longitudinal section of the exchange surface and the fins of Figure 6.

[Fig. 8] is a view similar to Figure 7 according to another embodiment.

[Fig. 9] is a view identical to Figure 8 with a different division of zones.

[Fig. 10] is a view similar to Figure 6 according to another embodiment representing a variable fin density.

Identical, similar or analogous elements retain the same reference from one figure to another.

Detailed description of the invention

Figure 1 represents a machine assembly 110 comprising electrical equipment 100 and a heat sink 1.

In the example considered, the electrical equipment 100 designates the power electronics, in particular three power modules 101 of an inverter making it possible to receive or provide an electrical power signal to the electrical phases of the winding of an electrical machine . A thermal interface material which makes it possible to evacuate the heat generated by the power modules 101 towards the heat sink 1 can be provided at the interface between the two elements. The thermal interface material is for example a paste, grease or thermal glue.

The heat sink 1 comprises an inlet 31 and an outlet 32 of heat transfer fluid as well as an exchange surface 5 extending between the inlet 31 and the outlet 32 and intended to exchange thermally with the heat transfer fluid. The dotted arrow represents in all figures the main direction of the fluid between inlet 31 and outlet 32 of heat sink 1.

As can be seen in Figure 2 or 3, the surface 5 comprises an inlet zone 51 communicating with the fluid inlet 31, an outlet zone 53 communicating with the fluid outlet 32 and an intermediate zone 52 arranged between the inlet zone 51 and the outlet zone 53. Thus, the heat transfer fluid follows the following path: inlet 31 of the heat sink 1, inlet zone 51, intermediate zone 52, outlet zone 53 then outlet 32 of the heat sink . The intermediate zone 52 separates the inlet zone 51 from the outlet zone 53. Thus, to pass from the inlet zone 51 to the outlet zone 53, the fluid passes through the intermediate zone 52.

In the context of the present invention, all zones 51, 52, 53 of the exchange surface 5 have an identical respective area ai, a ₂ , a ₃ . In other words the area ai of the input zone 51 = the area a ₂ of the intermediate zone 52 = the area a ₃ of the exit zone 53.

In the examples considered, the surfaces 51, 52, 53 are also identical in shape, but they may not have the same shape as long as the surfaces have equal areas.

A plurality of fins 20 project from said exchange surface 5. Preferably, the fins 20 project radially from the exchange surface 5, that is to say perpendicular to the exchange surface 5 .

The fins 20 are arranged in a plurality of longitudinal rows and a plurality of transverse rows. In the example considered in Figure 2, the fins 20 are arranged in six longitudinal rows and fifteen transverse rows. The number of these rows is adapted to the heat sink and in particular to the size of the exchange surface 5.

As can be seen in more detail in Figures 4 and 5, each fin 20 has a leading edge 25 and a trailing edge 26. The edges are defined relative to the main direction of the heat transfer fluid. An angle of incidence a is measured between the segment of smallest distance 27 which connects the leading edge 25 to the trailing edge 26 and the main direction of the heat transfer fluid between the inlet 31 and the outlet 32 represented by the arrow in dotted. The angle a can also be seen as the angle between the longitudinal axis of the fin 20 (that is to say an axis along the length of the fin 20) and the main direction of the fluid.

In Figures 2 and 3, the fins 20 are of parallelepiped shape as shown in Figure 4. Alternatively, the fins 20 can be of ellipsoidal shape as shown in Figure 5.

The fins 20 of the inlet 51, intermediate 52 and outlet 53 zones respectively have an average inlet angle of incidence a _m i, intermediate a _m2 and outlet a _m3 . The average angle of incidence a _m of a zone therefore corresponds to the sum of the angles of incidence a of the fins 20 of a zone divided by the number of fins 20 of this zone. In the context of the present invention, the average entry angle of incidence a _mi is less than the intermediate average angle of incidence a _m2 which is less than the average exit angle of incidence a _m3 . In other words, a _mi < a _m2 < a _m3 .

In these examples, the fins 20 of the inlet zone 51 have a maximum angle of incidence a which is less than the smallest angle of incidence of the intermediate zone 52 and the fins 20 of the intermediate zone 52 have an angle d maximum incidence which is less than the smallest height of the fins 20 of the exit zone 53.

The progression of the angle of incidence of the fins 20 between the inlet 31 and the outlet 32 can be staged as is the case in Figure 2. In this example, all the fins 20 of the same zone having the same angle of incidence a, the average angle of incidence a _mi , a _m2 , a _m3 respective of each zone 51, 52, 53 will be equal to the angle of incidence ode any fin 20 of this same area.

Alternatively, as can be seen in Figure 3, the progression of the angle of incidence of the fins 20 between the inlet 31 and the outlet 32 can be linear. In fact, each fin 20 of the same longitudinal row has an angle of incidence a less than the angle of incidence a of the next fin 20, according to the main direction of the fluid between the inlet 31 and the outlet 32. Here, the respective average angle of incidence a _m i, a _m2 , a _m3 of each zone 51, 52, 53 will therefore be equal to the sum of the angles of incidence a of the fins 20 of each zone 51, 52, 53 divided by the number of fins 20 of each zone.

Each fin 20 extends over a height h between a base placed on the exchange surface 5 from which the fin 20 projects and a peak. The height h is therefore commonly understood here as being the distance separating the base from the summit along an axis perpendicular to the exchange surface 5.

As can be seen in Figures 6 to 10, the average height of the fins 20 of a zone is not identical from one zone to another. Here we consider the average height of the fins per zone. Thus, in the inlet zone 51, the fins 20 extend according to an average inlet height h _m5 i, in the intermediate zone 52 according to an intermediate average height h _m52 and in the exit zone 53 according to an average height output h _m53 .

The average height of the fins 20 of a zone is calculated by taking the sum of all the fins 20 of this zone then dividing it by the number of fins 20 of this same zone. In the examples considered, the average inlet height h _m5i of the fins 20 is less than the average intermediate height h _m5 2 which is less than the average outlet height h _m5 3. In other words, h _m5i < h _m5 2 < h _m5 3.

Here, the fins 20 are arranged in seven longitudinal rows and fifteen transverse rows.

The fins 20 of the inlet zone 51 have a maximum height which is less than the smallest height of the fins 20 of the intermediate zone 52 and the fins 20 of the intermediate zone 52 have a maximum height which is less than the smallest height of the fins 20 of the outlet zone 53.

In Figure 6, certain fins 20 of the same zone have different heights (the fins 20 of a longitudinal row) and others have identical heights (the fins 20 of a transverse row). The progression of the height of the fins between the inlet 31 and the outlet 32 can be linear as is the case in Figures 6 and 7. In fact each fin 20 of the same longitudinal row has a height less than the height of the next fin 20, according to the direction of the fluid between inlet 31 and outlet 32.

Alternatively, as can be seen in Figure 8 or 9, the progression of the height of the fins between inlet 31 and outlet 32 can be stepped. In this example, all the fins 20 of the same zone 51, 52, 53 extend over the same height.

In the examples of Figures 6 to 8, each zone 51, 52, 53 comprises 5 transverse rows of fins 20. It is entirely possible to consider that the exchange surface 5 comprises an inlet zone 51, a zone exit zone 53 and n intermediate zones 52 (n being an integer between 1 and 13 in the present case) arranged between the entrance zone 51 and the exit zone 53. The average height will always comply with the following rule: h _m5i

< hm52n < hm52 (n+1) < h m3.

An example of an exchange surface 5 divided into an entry zone 51, a first intermediate zone 52i, a second intermediate zone 52 ₂ , a third intermediate zone 52 ₃ and an exit zone 53 is presented in Figure 9. In this case, we find the following relationship between the average heights of each zone, h _m5i < h _m 52.i < h _m 52.2< h _m 52.3

< hm3.

In all the examples so far, the inlet zone 51, the intermediate zone 52 and the outlet zone 53 have an identical number of fins 20. In other words, the density, namely the number of fins 20 per zone, is identical between the different zones. Each zone has a number of fins 20 identical to the number of fins 20 of another zone. In this case, each zone 51, 52, 53 comprises thirty-five fins. Alternatively and as shown in Figure 10, the number of fins 20 of the inlet zone 51 may be less than the number of fins 20 of the intermediate zone 52 which may be less than the number of fins 20 of the exit zone 53. In this case, the number of fins 20 of the entry zone 51 is fourteen, that of the intermediate zone 52 is twenty-eight and that of the exit zone 53 is thirty -five.

In all the examples so far, all the fins 20 which project from the exchange surface 5 of the heat sink 1 have an identical shape, here parallelepiped. Preferably, all the fins 20 of the same zone 51, 52, 53 have an identical shape.

Alternatively, the shape of the fins 20 varies from one zone 51, 52, 53 to another. According to another variant, the shape of the fins 20 can vary even within a zone.

Advantageously, the heatsink also includes an additional exchange surface 50, here arranged opposite the exchange surface 5. This additional surface 50 extends between the inlet 31 and the outlet 32 and is intended to exchange thermally with the coolant. Advantageously, the additional surface has the characteristics of the exchange surface 5, namely:

- an entry zone communicating with the fluid inlet,

- an outlet zone communicating with the fluid outlet and

- at least one intermediate zone arranged between the entry zone and the exit zone,

- all zones of the additional exchange surface have an identical area, and

- a plurality of additional fins project from said additional exchange surface 50.

Furthermore :

- in each of the zones said additional fins extend respectively over an average entry, intermediate and exit height in the entry, intermediate and exit zone, the average entry height of the additional fins being less than the height intermediate average which is less than the average outlet height and/or the number of additional fins of the inlet zone is less than the number of additional fins of the intermediate zone which is less than the number of additional fins of the zone output and/or - each additional fin has a leading edge, a trailing edge and an angle of incidence measured between the segment of smallest distance which connects the leading edge to the trailing edge and the main direction of the heat transfer fluid between the entry and exit, the additional fins of the entry, intermediate and exit zone respectively have an average entry, intermediate and exit angle of incidence, said average entry angle of incidence being less than the intermediate mean angle of incidence which is less than the mean exit angle of incidence.

The exchange surface 5 and the additional exchange surface 50 are thus arranged so as to form at least in part a cooling chamber in which the heat transfer fluid flows. The chamber is delimited by surface 5 which is the interior surface and additional surface 50 which is the exterior surface.

In all the examples considered so far, we have presented a heat sink suitable for cooling power electronics. In this case, the exchange surface 5 has a flat surface, preferably rectangular in shape. The additional surface 50 also has a flat surface, preferably rectangular in shape.

Preferably, the distance between the exchange surface 5 and the additional surface 50 is constant. In other words, the height of the cooling chamber is constant.

In a variant not shown, the exchange surface can have a circular shape so as to cool, for example, a rotating electrical machine.

A rotating electric machine has a polyphase stator with a stator body surrounding an X-axis rotor mounted on a shaft. The stator of the machine surrounds the rotor with the presence of an air gap on the internal periphery of the stator and the external periphery of the rotor. The stator and rotor form the active parts of the electrical machine and will be surrounded by the heat sink.

The power of the machine can be between 4kW and 50kW. Alternatively, the electric machine could be installed on an axle of the motor vehicle, in particular a rear axle. In the example considered, the electrical machine advantageously has an operating voltage of less than 60 Volts, and preferably worth 48 Volts. Typically, the torque provided by the electric machine is between 30N.m and 150N.m. Alternatively, the electric machine may have an operating voltage of more than 60V, or even more than 80V or more than 100V, in particular 300V. or more. In this case, the power of the machine could be between 60kw and 300kW

Of course, the preceding description has been given by way of example only and does not limit the field of the invention from which one would not escape by replacing the different elements with any other equivalents.

Furthermore, the different features, variants, and/or embodiments of the present invention can be associated with each other in various combinations, as long as they are not incompatible or exclusive of each other.

Claims

CLAIMS Heat sink (1), in particular for electrical equipment, comprising:

- an inlet (31) and an outlet (32) of heat transfer fluid,

- an exchange surface (5) extending between the inlet (31) and the outlet (32) and intended to exchange heat with the heat transfer fluid, said surface (5) comprising an inlet zone (51) communicating with the fluid inlet, an outlet zone (53) communicating with the fluid outlet and at least one intermediate zone (52) arranged between the inlet zone (51) and the outlet zone (53), all zones of the exchange surface (5) having an identical area (ai, a ₂ , a ₃ ),

- a plurality of fins (20) projecting from said exchange surface (5) in each of the zones (51, 52, 53), each fin (20) has a leading edge (25), an edge of leak (26) and an angle of incidence (a) measured between the segment of smallest distance (27) which connects the leading edge to the trailing edge and the main direction of the heat transfer fluid between the inlet (31) and the outlet (32), characterized in that the fins (20) of the inlet (51), intermediate (52) and outlet (53) zones respectively have an average inlet angle of incidence (a _m i ), intermediate (a _m2 ) and exit (a _m3 ), said average entry angle of incidence (a _m i) being less than the intermediate average angle of incidence (a _m2 ) which is less than the mean exit angle of incidence (a _m3 ). Heat sink (1) according to claim 1, characterized in that all the fins (20) of the same zone have the same angle of incidence (a). Heat sink (1) according to any one of the preceding claims, characterized in that said fins (20) are of parallelepiped, ellipsoidal or substantially ellipsoidal shape. Heat sink (1) according to any one of the preceding claims, characterized in that the fins (20) of the inlet zone (51) have a maximum angle of incidence (a) which is less than the smallest angle d The incidence of the fins of the intermediate zone (52) and the fins of the intermediate zone have a maximum angle of incidence which is less than the smallest angle of incidence of the fins of the fins of the outlet zone (53). Heat sink (1) according to any one of the preceding claims, characterized in that said fins (20) extend respectively over an average inlet (h _m5 i), intermediate (h _m5 2) and outlet height ( h _m5 3) in the inlet (51), intermediate (52) and outlet (53) zone, and in that the average inlet height (h _m5 i) of the fins (20) is less than the height intermediate average (h _m5 2) which is less than the average exit height (h _m53 ). Heat sink (1) according to any one of the preceding claims, characterized in that all the fins (20) of the same zone (51, 52, 53) extend over the same height. Heat sink (1) according to any one of the preceding claims, characterized in that the fins (20) of the inlet zone (51) have a maximum height which is less than the smallest height of the fins of the intermediate zone (52) and the fins of the intermediate zone have a maximum height which is less than the smallest height of the fins of the outlet zone (53). Heat sink (1) according to any one of the preceding claims, characterized in that the number of fins (20) of the inlet zone (51) is less than the number of fins of the intermediate zone (52) which is less than the number of fins in the outlet zone (53). Heat sink (1) according to any one of the preceding claims, characterized in that all the fins (20) of the same zone (51, 52, 53) have an identical shape. Heat sink (1) according to any one of the preceding claims, characterized in that the exchange surface (5) has a flat surface, preferably rectangular in shape.