EP3553445B1 - Improved heat pipe with capillar structures having reentering slots - Google Patents

Description

TECHNICAL FIELD AND STATE OF THE PRIOR ART

The present invention relates to an improved functioning reentrant groove capillary pumped heat pipe. In particular, the invention relates to a capillary pumped heat pipe as defined by the preamble of claim 1, and as disclosed by FR 2 776 763 .

The invention belongs to the field of heat exchange devices, in particular heat pipes, more particularly capillary pumped heat pipes.

A heat pipe comprises a hermetically sealed enclosure, a working fluid and a capillary network. During manufacture, all the air present in the heat pipe is evacuated and a quantity of liquid is introduced which makes it possible to saturate the capillary network. An equilibrium is then established between the liquid phase and the vapor phase.

Under the effect of a hot source applied to one of the ends, designated the evaporator, the liquid vaporizes by inducing a slight overpressure which causes the movement of the vapor towards the second end, designated the condenser. In the condenser, the vapor condenses and returns to the liquid phase. The condensed fluid circulates in the capillary network and returns to the evaporator under the effect of capillary forces. The return of the liquid fluid from the condenser zone to the evaporator zone is obtained by capillary pumping.

Grooved heat pipes work on the principle of capillary pumping. They have a tube, in which the inner surface has longitudinal or slightly spiral-shaped grooves. Grooved heat pipes have a vapor core and a capillary network in which the liquid circulates. Due to a variation in curvature of the vapor-liquid interface between the condenser zone and the evaporator zone, a pressure gradient appears in the liquid, which leads to a variation in capillary pressure. The smaller the width of the grooves, the greater the capillary pumping effect.

Furthermore, deep grooves make it possible to obtain a large passage section for the liquid return, and therefore to minimize the pressure loss.

The maximum power that can be transported by grooved heat pipes is generally fixed by the capillary limit, the driving term of which is the capillary pressure, and the term essentially limiting the loss of liquid pressure in the grooves.

Heat pipes with reentrant grooves are particular examples of heat pipes with grooves, in which the grooves have a narrow window with respect to the rest of the groove, which makes it possible to increase the capillary pumping effect while limiting the pressure drops. These heat pipes are used mainly in the space field, for example for thermal regulation in satellites and / or spacecraft.

The known production techniques for heat pipes with grooves, and in particular heat pipes with reentrant grooves, do not make it possible to obtain grooves having a depth substantially greater than their width.

These heat pipes are produced essentially by extrusion. With such a technique, the depth to width ratio of rectangular grooves is of the order of 1.

In the case of reentrant grooves, the manufacturing constraints are even more drastic, limiting the width, the length of the constriction and the section of the reentrant part.

Another technique uses mechanical machining, with this technique also the depth to width ratio is not appreciably greater than 1. In addition, this technique has a relatively high cost price and is not suitable for manufacturing on average and large series.

Another technique uses chemical etching. But it does not make it possible to have a significant depth to width ratio either.

The document US 7 051 793 describes a heat pipe comprising one or more zones of circulation of the fluid in vapor form and on either side of these zones of the porous zones of circulation of the liquid, these capillary zones extending over the entire heat pipe.

The heat pipe is made by stacking plates. The capillary zones are obtained by stacking plates comprising windows, the windows having orthogonal directions from one plate to another.

The pumping effect is not optimal. In addition, there is a significant pressure drop. This heat pipe spreads the heat flow across the width of the heat pipe and is not optimized for transporting the heat flow along its length.

DISCLOSURE OF THE INVENTION

It is therefore an object of the present invention to provide a reentrant groove capillary pumped heat pipe with improved operation and simplified construction.

It is an additional object of the present invention to provide a heat pipe whose structure is compatible with medium and large series production.

The object stated above is achieved by a heat pipe with reentrant grooves comprising a stack of plates secured together in a hermetic manner. The end plates form closure plates and the spacer plates are structured such that the stack of spacer plates defines reentrant grooves extending the entire length of the heat pipe channel.

For this, in an exemplary embodiment, the heat pipe comprises at least three intermediate plates, two first plates each having a central window delimiting the steam channel and two side windows, on either side of the central window, and delimiting the grooves. , and a second plate disposed between the two first plates and forming a spacer. Thus the lateral edges of two central windows delimit the entry end of reduced section of the reentrant grooves. The thickness of the spacer is used to define the width of the entry end. The depth of the grooves is fixed by the transverse dimension of the side windows and the width of the grooves is fixed by the thickness of the first two plates and the thickness of the second plate. It is thus easy to fix the dimensions of the grooves reentrants and to make such grooves. It is then possible to choose, on the one hand, the dimensions of the exchange zone to optimize the pumping effect, and on the other hand the dimensions of the grooves to limit the pressure drops.

Thanks to the invention, it is possible to produce a heat pipe with reentrant grooves, the operation of which is improved while offering simplified manufacture.

In other words, the grooves are delimited by stacked plates. Thus the depth and the width of the grooves are obtained separately, so the limitations on the depth to width ratio do not arise, which arise for example in the case of production by extrusion or chemical etching.

Very advantageously, the heat pipe according to the invention can comprise grooves of variable section between the vaporizer zone and the condenser zone.

The present invention therefore relates to a capillary pumped heat pipe with reentrant grooves extending at least along a first longitudinal direction, comprising a first longitudinal end intended to be heated and a second longitudinal end intended to be cooled, an enclosure sealed extending between the first end and the second end, the enclosure comprising a stack of plates along a second direction, said stack comprising two closure plates, at least one module of at least two intermediate plates between the closure plates. The intermediate plates comprise at least a first intermediate plate comprising at least one central window, the edges of which partly define a vapor channel extending along the first direction, in which the vapor is intended to circulate, and on each side of the central window (in a third direction orthogonal to the first and second directions, a structure whose edges partially define a liquid channel, at least one other intermediate plate comprising at least one window whose edges partially define the vapor channel. The heat pipe comprising also at least two exchange zones delimited between the first intermediate plate and the other intermediate plate, connecting the vapor channel and the liquid channel.

In an exemplary embodiment, the other intermediate plate is a first intermediate plate, the structures are recesses made in at least one of the faces of said first intermediate plates, in the stack, the recesses are placed opposite each other, and the areas of 'exchange are delimited by two edges of two recesses of the first two intermediate plates facing.

The first intermediate plates may have recesses in their two faces.

For example, a second intermediate plate is interposed between two first intermediate plates at the level of the outer edges of the first intermediate plates, the thickness of which defines the dimension in the direction of the stacking of the exchange zones.

The recesses can advantageously comprise a bottom and at least one edge connecting the bottom to the exchange zone, said edge being inclined away from the steam channel or said edge connecting to said bottom by a connection fillet.

In another exemplary embodiment, the other plate is a third intermediate plate, the window of which has the same section as the central window of the first intermediate plate, so that two of its side edges in the third direction delimit with the first plate interlayer of the exchange zones.

A second intermediate plate may be interposed between the first intermediate plate and the third intermediate plate at the level of the outer edges of said first and third intermediate plates, the thickness of which defines the dimension in the direction of the stacking of the exchange zones.

In another exemplary embodiment, the other intermediate plate is a first intermediate plate, the structures are windows. The heat pipe comprises a second intermediate plate interposed between the two first intermediate plates at the level of the outer edges of the first intermediate plates, the thickness of which defines the dimension in the direction of the stacking of the exchange zones, and the heat pipe comprises a third intermediate plate, the window of which has the same section as the central windows of the first intermediate plates, in contact with one of the first intermediate plates and closing the side windows on either side of the central window in the second direction.

The reentrant-groove capillary pumped heat pipe may have n modules on top of each other, n being an integer> 1, defining a single vapor channel and n liquid channels on each side of the liquid channel and n exchange zones, each connecting the vapor channel with a liquid channel.

The structures can advantageously have a trapezoidal shape in a plane orthogonal to the second direction.

According to an additional characteristic, the central windows of the intermediate plates may include an upright extending in the first direction so that the vapor channel has a wall extending over the entire height of the stack and in the first direction.

When a third spacer plate is implemented, the window it comprises may include at least one transverse post extending in the third direction.

According to an additional characteristic, the reentrant-grooved capillary pumped heat pipe may include several vapor channels, each connected to liquid channels by exchange zones.

At least one of the end plates may have a surface greater than that of the intermediate plates in a direction transverse to the stack so as to form thermal diffusers.

In an advantageous example, the heat pipe comprises heat exchange means at the first end and / or second end.

The heat exchange means at the second end may comprise one or more fins in thermal contact with at least one of the closure plates and / or a fluidic circuit in thermal contact with at least one of the closure plates, said circuit being formed by a plate structured so as to delimit the channels, said channels being closed by said closure plate and an additional closure plate, the heat exchange means also comprising means for supplying said fluidic circuit with heat transfer fluid.

The present invention also relates to a heat exchange system comprising several heat pipes according to the invention, in which the heat pipes are arranged in several planes, the heat pipes of two successive planes crossing each other and in which the heat pipes of two successive planes share a same end plate.

At least one heat pipe of one layer is advantageously connected hydraulically to at least one heat pipe of the same layer.

The heat exchange system can advantageously include a single-phase or two-phase heat exchange circuit.

• Réalisation d'au moins une fenêtre centrale dans au moins deux plaques,
• Structuration de chaque côté de la fenêtre centrale dans au moins l'une desdites plaques, pour former des fenêtres latérales ou des évidements latéraux,
• Empilement desdites plaques de sorte que les fenêtres centrales délimitent un canal vapeur, que les fenêtres ou évidements latéraux forment des canaux liquides de part et d'autre du canal vapeur, et de sorte que des zones d'échange connectent le canal vapeur et les canaux liquides ;
• Mise en place aux extrémités de l'empilement dans la direction de l'empilement de plaques de fermeture.
• Solidarisation desdites plaques de sorte à délimiter une enceinte étanche,
• Remplissage partiel du canal avec un fluide sous forme liquide et fermeture étanche du canal.

A subject of the present invention is also a method for manufacturing a capillary pumped heat pipe comprising, from at least two plates of given external dimensions:

• Creation of at least one central window in at least two plates,
• Structuring of each side of the central window in at least one of said plates, to form side windows or side recesses,
• Stacking of said plates so that the central windows delimit a steam channel, that the side windows or recesses form liquid channels on either side of the steam channel, and so that exchange zones connect the steam channel and the channels liquids;
• Positioning at the ends of the stack in the direction of the stack of closure plates.
• Joining of said plates so as to define a sealed enclosure,
• Partial filling of the channel with a fluid in liquid form and sealing of the channel.

For example, the plates have an aluminum alloy at the core and on its outer faces an eutectic aluminum alloy with a lower melting point than that of the core aluminum alloy and the connection is obtained by eutectic brazing.

BRIEF DESCRIPTION OF THE DRAWINGS

• la figure 1A est une vue de côté d'un exemple de de caloduc à rainures réentrantes selon l'invention,
• la figure 1B est une vue en coupe le long du plan de coupe A-A d'un exemple du caloduc de la figure 1A représenté en perspective,
• la figure 2 est une vue de face partielle de la coupe de la figure 1B,
• la figure 3 est une vue en éclaté partielle du caloduc de la figure 1,
• la figure 4A est une représentation schématique des ménisques dans le caloduc des figures 1A -3 au niveau de l'évaporateur,
• la figure 4B est une représentation schématique des ménisques dans le caloduc des figures 1A-3 au niveau du condenseur,
• la figure 4C est une vue partiellement arrachée du caloduc de la figure 1A schématisant la reculée du ménisque dans la zone d'échange,
• la figure 5 est une vue en coupe d'un exemple d'un caloduc multicanaux représenté en perspective,
• la figure 6 est une vue en coupe transversale d'une variante de réalisation d'un caloduc selon l'invention représentée en perspective,
• la figure 7A est une vue en coupe d'un autre exemple du caloduc représenté en perspective,
• la figure 7B est une vue en coupe de face d'une première plaque intercalaire mise en œuvre dans le caloduc de la figure 7A,
• la figure 8A est une vue en coupe d'un autre exemple du caloduc représenté en perspective,
• la figure 8B est une vue de dessus de la première plaque intercalaire mise en œuvre dans le caloduc de la figure 8A,
• la figure 8C est une vue en coupe de face de la première plaque intercalaire mise en œuvre dans le caloduc de la figure 8A,
• la figure 9 est une vue en coupe d'un autre exemple du caloduc représenté en perspective,
• la figure 10 est une vue en coupe d'un autre exemple du caloduc représenté en perspective,
• les figures 11A et 11B sont des vues en coupe transversales de premières plaques intercalaires munies d'évidement selon d'autres exemples de réalisation,
• la figure 12 est une vue de dessus de la première plaque intercalaire définissant un canal liquide de section variable entre l'évaporateur et le condenseur,
• les figures 13 et 14 sont des vues en coupe transversale du caloduc de la figure 12 au niveau de la zone condenseur et au niveau de la zone évaporateur respectivement,
• la figure 15 est une vue de dessus d'une variante de la plaque de la figure 12
• la figure 16 est une vue en coupe d'un autre exemple du caloduc représenté en perspective muni de diffuseurs thermiques,
• la figure 17 est une vue en coupe d'un autre exemple du caloduc représenté en perspective,
• la figure 18 est une vue en coupe d'un autre exemple du caloduc représenté en perspective,
• la figure 19 est une vue en coupe d'un autre exemple du caloduc représenté en perspective,
• la figure 20 est une vue de dessus de la troisième plaque intercalaire mise en œuvre dans le caloduc de la figure 19,
• les figures 21 et 22 sont des vues en perspectives d'autres exemples de premières plaques intercalaires au niveau de la fenêtre centrale,
• la figure 23 est une vue éclatée d'un caloduc multicanaux selon l'invention permettant un remplissage facilité,
• la figure 24 est une vue en perspective d'un autre exemple de réalisation d'un caloduc selon l'invention réparti dans plusieurs plans,
• les figures 25A à 25F sont des vues en perspective d'exemples d'ailettes applicables à un caloduc selon l'invention,
• la figure 26 est une vue éclatée d'un caloduc selon un exemple de réalisation comportant un échangeur thermique au niveau du condenseur,
• la figure 27 est une vue en coupe transversale d'un caloduc de l'état de la technique,
• la figure 28 est un graphique représentant les variations de limite capillaire Lc en Watt en fonction de la température en °Cdu caloduc dans le cas du caloduc de la figure 1 (I) et du caloduc de la figure 27 (II) utilisant l'ammoniac comme fluide de travail et à inclinaison nulle
• la figure 29 est une vue en perspective d'un système d'échange thermique mettant en œuvre plusieurs caloducs selon l'invention,
• la figure 30 est une vue en coupe transversale du système de la figure 29,
• la figure 31 est une vue en perspective d'une variante du système de la figure 29,
• la figure 32 est une vue en perspective d'une variante du système de la figure 29 mettant en œuvre un échangeur thermique,
• la figure 33 est une vue en coupe d'une variante du caloduc de la figure 16.

The present invention will be better understood on the basis of the description which follows and the appended drawings in which:

• the figure 1A is a side view of an example of a heat pipe with reentrant grooves according to the invention,
• the figure 1B is a sectional view along section plane AA of an example of the heat pipe of the figure 1A shown in perspective,
• the figure 2 is a partial front view of the section of the figure 1B ,
• the figure 3 is a partial exploded view of the heat pipe of the figure 1 ,
• the figure 4A is a schematic representation of the menisci in the heat pipe of figures 1A -3 at the evaporator,
• the figure 4B is a schematic representation of the menisci in the heat pipe of figures 1A-3 at the condenser,
• the figure 4C is a partially cutaway view of the heat pipe of the figure 1A schematizing the retreat of the meniscus in the exchange zone,
• the figure 5 is a sectional view of an example of a multichannel heat pipe shown in perspective,
• the figure 6 is a cross-sectional view of an alternative embodiment of a heat pipe according to the invention shown in perspective,
• the figure 7A is a sectional view of another example of the heat pipe shown in perspective,
• the figure 7B is a front sectional view of a first spacer plate implemented in the heat pipe of the figure 7A ,
• the figure 8A is a sectional view of another example of the heat pipe shown in perspective,
• the figure 8B is a top view of the first spacer plate implemented in the heat pipe of the figure 8A ,
• the figure 8C is a front sectional view of the first spacer plate implemented in the heat pipe of the figure 8A ,
• the figure 9 is a sectional view of another example of the heat pipe shown in perspective,
• the figure 10 is a sectional view of another example of the heat pipe shown in perspective,
• the figures 11A and 11B are cross-sectional views of first insert plates provided with a recess according to other exemplary embodiments,
• the figure 12 is a top view of the first intermediate plate defining a liquid channel of variable section between the evaporator and the condenser,
• the figures 13 and 14 are cross-sectional views of the heat pipe of the figure 12 at the level of the condenser zone and at the level of the evaporator zone respectively,
• the figure 15 is a top view of a variant of the plate from the figure 12
• the figure 16 is a sectional view of another example of the heat pipe shown in perspective fitted with thermal diffusers,
• the figure 17 is a sectional view of another example of the heat pipe shown in perspective,
• the figure 18 is a sectional view of another example of the heat pipe shown in perspective,
• the figure 19 is a sectional view of another example of the heat pipe shown in perspective,
• the figure 20 is a top view of the third intermediate plate implemented in the heat pipe of the figure 19 ,
• the figures 21 and 22 are perspective views of other examples of first spacer plates at the central window,
• the figure 23 is an exploded view of a multichannel heat pipe according to the invention allowing easy filling,
• the figure 24 is a perspective view of another embodiment of a heat pipe according to the invention distributed in several planes,
• the figures 25A to 25F are perspective views of examples of fins applicable to a heat pipe according to the invention,
• the figure 26 is an exploded view of a heat pipe according to an exemplary embodiment comprising a heat exchanger at the level of the condenser,
• the figure 27 is a cross-sectional view of a heat pipe of the state of the art,
• the figure 28 is a graph showing the variations of the capillary limit Lc in Watt as a function of the temperature in ° C of the heat pipe in the case of the heat pipe of the figure 1 (I) and the heat pipe of the figure 27 (II) using ammonia as the working fluid and at zero tilt
• the figure 29 is a perspective view of a heat exchange system implementing several heat pipes according to the invention,
• the figure 30 is a cross-sectional view of the system of the figure 29 ,
• the figure 31 is a perspective view of a variant of the system of the figure 29 ,
• the figure 32 is a perspective view of a variant of the system of the figure 29 implementing a heat exchanger,
• the figure 33 is a sectional view of a variant of the heat pipe of the figure 16 .

DETAILED PRESENTATION OF PARTICULAR EMBODIMENTS

On the figures 1A to 3 , one can see an example of a capillary pumped heat pipe C1 with reentrant grooves according to the invention.

For the sake of simplicity, the “reentrant grooves” will be designated in the remainder of the description by “grooves”.

On the figure 1A , we can see a capillary pumped heat pipe C1 seen from the outside extending along a longitudinal axis X.

In the present application, the longitudinal direction is that given by the X axis.

The heat pipe C1 comprises a hermetic enclosure 2 extending along the longitudinal axis X and comprising a first longitudinal end 4 and a second longitudinal end 6. The first end 4 is for example intended to be placed at a hot source SC . The first end 4 is designated the evaporator, and the second end 6 is for example intended to be placed at a cold source SF. The second end is called the condenser.

The hot source is for example an electrical or electronic component, a heat storage, an exothermic chemical reactor. The cold source is for example a radiative surface, fins in forced convection, cold plates in mono or two-phase flow, cold storage, an endothermic chemical reaction, etc.

The heat pipe advantageously has a shape such that it extends in the XY plane, so as to have faces 7.1, 7.2, parallel to the XY plane, having a large surface area promoting heat exchanges with the hot source and the cold source .

The heat pipe is in contact with the hot source and the cold source on one or both sides 7.1, 7.2 of large area. The faces 7.1, 7.2 of larger area are in the example shown orthogonal to the Z direction.

The heat pipe C1 comprises a channel 8 extending along the longitudinal axis X and grooves 10 extending along the longitudinal axis X on either side of the channel 8. The channel 8 is used for circulation. of the vapor phase from the evaporator zone to the condenser zone, and will be designated by “vapor channel” and the grooves are used for the circulation of the liquid phase from the condenser zone to the evaporator zone.

The grooves 10 include an exchange zone 10.1 and a liquid channel 10.2 connected to the vapor channel 8 by the exchange zone 10.1. The liquid channel is intended for the circulation of the liquid from the condenser zone to the evaporator zone. The exchange zone has a section in the XZ plane that is smaller than that of the liquid channel 10.2.

The grooves are formed in the side walls 8.1, 8.2 of the channel 8. The side walls are viewed with respect to the longitudinal direction X.

The heat pipe enclosure comprises a stack of plates delimiting the vapor channel 8 and the grooves 10.

The stack comprises two end plates 12 located at the ends of the stack in a Z direction orthogonal to the X and Y directions. The end plates 12 are intended to close the channel 8 and are also referred to as “closure plates”. .

The stack also comprises intermediate plates 14, 16, 17 arranged between the end plates 12. The intermediate plates comprise a set of first intermediate plates 14, a set of second intermediate plates 16, and a set of third intermediate plates 17 , the plates of the different sets being superimposed so as to delimit the channel 8 and the grooves 10.

In this example, all the plates 12, 14, 16, 17 have the same external dimensions, the stack is then of rectangular parallelepiped shape.

According to another example, the surface of the plates can vary. It is conceivable that the surface of the plates decreases in the Z direction. It is also conceivable that the width of the intermediate plates is variable along the X direction, for example to provide a condenser with a larger area than the evaporator. The windows are shaped so as to cover the entire surface, they are not parallel.

As can be seen on the figure 2 , the stack comprises sub-groups G1, G2 ... of intermediate plates comprising, in this order, a first plate 14, a second plate 16 and a first plate 14. Two sub-groups are separated by a third plate 17. At the ends of the stack, the third plates 17 are replaced by the closure plates 12.

A sub-group and two third plates define two grooves 10 with their exchange zone and the liquid channel.

On the figure 3 , you can see the intermediate plates.

The first intermediate plates have a central window 18 extending along the longitudinal axis X, and two side windows 19, located on either side of the central window 18 and extending along the longitudinal axis. X. The central window 18 is separated from each side window 19 by an upright 21.

The first intermediate plates 14 have a thickness e1.

The window 18 is designated “central window” because it is located between the two side windows, but it will be understood that it is not necessarily located in the center of the first plate. In this example shown, the windows 18 and 19 have a rectangular shape having the same dimension in the X direction.

The central window 18 has a dimension L1 in the Y direction and the side windows 19 have a dimension L1 'in the Y direction.

Each second spacer plate 16 has a thickness e2 and has a window 20 extending in the X direction and in the Y direction. In this example, the window 20 has a rectangular shape having a dimension I2 in the X direction and a dimension L2. in the Y direction.

The dimensions of the windows 18 and 20 in the X direction are preferably equal or close and correspond to the length of the channel 8.

Preferably, the dimension L2 is close to or equal to the distance between the two outer lateral edges of the windows 19, so that by placing a second intermediate plate 16 between two first intermediate plates 14, and by superimposing the windows, the lateral edges exterior windows 19 are aligned with the side edges of window 20. This alignment defines a flat bottom for grooves 10.

The third intermediate plates 17 close the grooves in the Z direction.

Two uprights 19 of two successive first intermediate plates 14 form the transverse edges of the exchange zone 10.1 of a groove, and the thickness e2 of the second intermediate plate defines the dimension of the exchange zone in the Z direction.

The third plates advantageously participate in delimiting two superimposed grooves 10 in the Z direction. As a variant, each group has its own two third plates.

Advantageously, each group G1, G2 ... defines two facing grooves. As a variant, only one groove could be defined, in this case the first plates 14 would have only one side window.

The vapor channel 8 has a dimension along the Y direction equal to L1 ′ and a dimension along the Z direction equal to the sum of the thicknesses of all the first, second and third intermediate plates.

The grooves 10 extend in the longitudinal direction and have a length I1 = I2, as does the channel 8. The exchange zone 10.1 of each groove has a dimension in the Z direction equal to e2. The liquid channel 10.2 has a dimension in the Z direction equal to 2e1 + e2 and a dimension in the Y direction equal to L1 '.

Thus, it is easy to produce grooves having both a small width exchange zone favorable to the pumping effect and a large section liquid channel limiting the pressure drops.

In addition, the invention has the advantage of being able to separately fix the width of the exchange zone 10.1 and the section of the liquid channel 10.2. The width is defined along the Z direction.

In fact, it is possible to use second intermediate plates of very small thickness e2 to have a small width of the exchange zone 10.2, and to use first intermediate plates 14 of large thickness e1 and of large dimensions L1 '. to produce a liquid channel of large section.

In addition, it is possible to achieve a small, or even very small, width to section ratio of the liquid channel. Indeed, the cross section of the liquid channel and the width of the exchange zone being fixed separately during different stages, there is no limitation due to the manufacturing process unlike extrusion or etching.

By way of comparison, in the case of a heat pipe with an extruded aluminum profile with reentrant grooves of the state of the art, for a heat pipe size of about 13 mm in external diameter in extrusion, the width of the reentrant grooves n 'is not less than 0.5mm and the size of the liquid channel in extruded cylindrical heat pipes is typically 1.5mm in diameter, then it provides a channel section of 1.76mm ² . The width / section ratio of the liquid channel is approximately 0.28.

Thanks to the invention, the width of the exchange zone can reach approximately 0.05 mm, and the liquid channel which is for example of rectangular section can have a dimension in the Z direction of 1.2 mm and a dimension in the Y direction of 2 mm, i.e. a section of 2.4 mm ² .

Thanks to the invention, a width / section ratio of the liquid channel of 0.05 / 2.4 = 0.021 is obtained.

Thanks to the invention, it is possible to obtain a width / section ratio of the liquid channel 10 times lower than with heat pipes with reentrant grooves obtained by extrusion.

Capillary pressure is the pressure difference between the vapor phase and the liquid phase near the meniscus.

On the figure 4A , we can see the menisci M shown at the exchange zone 10.1 of the grooves 10 at the evaporator, and on the figure 4B at the condenser. At the condenser zone, the wetting angle is close to 90 °, and at the evaporator zone, the wetting angle is at its minimum value. Depending on the materials used, the surface treatments and the fluid, this minimum angle may be equal to 0. The capillary pressure is inversely proportional to the radius of curvature of the meniscus. This radius of curvature is very large at the condenser, and is appreciably smaller at the evaporator. On the figure 4C , we can see the retreat of the meniscus in the exchange zone between the evaporator and the condenser.

The heat pipe has several liquid channels along the Z direction separated by the third spacer plates. The third intermediate plates conduct the heat from the plate 12 to the menisci of each liquid channel where evaporation occurs.

By way of example, the first plates have a thickness between 0.05 mm and 6 mm, preferably equal to 0.5 mm.

The second plates which fix the width of the exchange zones have a thickness of between 0.05 mm and 1 mm, preferably equal to 0.2 mm.

The liquid channels have, for example, a dimension in the Y direction which can vary between 1 mm and 4mm, and preferably be equal to 2 mm.

The vapor channels have a width of between 2 mm and 8 mm, and preferably equal to 4 mm.

• les premières plaques ont une épaisseur égale à 0,5 mm,
• les deuxièmes ont une épaisseur comprise égale à 0,2 mm,
• les canaux liquides ont une dimension dans la direction Y qui est égale à 2 mm,
• le canal vapeur a une largeur égale à 4 mm.

In the example of an aluminum alloy heat pipe using ammonia as the working fluid. Preferably:

• the first plates have a thickness equal to 0.5 mm,
• the second have a thickness equal to 0.2 mm,
• the liquid channels have a dimension in the Y direction which is equal to 2 mm,
• the steam channel has a width equal to 4 mm.

The external dimensions of the heat pipes are between a few centimeters and a few meters. The maximum size of heat pipes is generally limited by the tools available. Indeed, the assembly of sheets by vacuum brazing requires large vacuum furnaces, a few meters in length. For cutting and machining of sheet metal, large machines are also required. In addition, the mechanical strength of sheets with small width and great length cuts must be taken into account.

For example, the windows are produced by punching, cutting, for example with a laser or with a water jet.

The heat pipe is filled with a two-phase fluid, it may be a fluid well known to those skilled in the art. This is chosen for example according to the operating and storage temperature range of the device, according to the constraints due to the pressure, the flammability, the toxicity of the fluid and the chemical compatibility between the fluid and the material. forming the heat pipe.

By way of example, for a heat pipe made of an aluminum alloy assembled by eutectic brazing, it is possible to use ammonia, acetone, methanol, n-heptane, R134a or other fluorinated refrigerants as fluid.

As a variant, it is possible to envisage producing the second intermediate plates 16 by assembling strips of metal, which would make it possible to simplify the problem of mechanical strength of thin sheets and small cutting widths.

On the figure 5 one can see an example of a multichannel C2 heat pipe according to the invention.

The heat pipe C2 has vapor channels 108.1 to 108.6 arranged parallel to each other in the longitudinal direction X, each vapor channel being connected to grooves 110.1 to 110.6 arranged laterally on either side of each vapor channel 108.1 to 108.6 .

Heat pipe C1 is a pattern repeated several times in heat pipe C2. The pattern is delimited by the dotted lines.

The heat pipe C2 is produced by superimposing plates extending in one piece in the Y direction. Thus all the channels and all the grooves are produced by stacking the same plates. The production is then simplified, because a large heat pipe is produced in one piece, without the problem of the arrangement of the channels and of the grooves relative to one another during assembly.

In this example, the intermediate plates are structured so that the bottoms of two grooves opening into two neighboring channels are formed by the same elements of the intermediate plates. Thus, the time for producing the plates is reduced and the density of channels and grooves is optimized. In the example of figure 5 , the heat pipes are fluidly isolated from each other. In another example, the heat pipes fluidly communicate with each other. The dimensions and the pitch between the heat pipes are chosen according to the application.

On the figure 6 , one can see an alternative embodiment of a C3 heat pipe according to the invention.

This heat pipe C3 differs from heat pipe C1 in that each groove 210 is delimited between two third plates 217 by a first plate 214 and a second plate 216. The first plate 214 has a structure similar to that of the plate 14.

The exchange zone 210.1 is delimited in the Z direction, on one side by the upright 221 of the first intermediate plate 214 and on the other side by the third intermediate plate 217. The width of the exchange zone 210.1 is equal to the thickness of the second intermediate plate 216. The dimension of the liquid channel 210.2 in the Z direction is equal to the sum of the thicknesses of the first intermediate plate 214 and of the second intermediate plate 216.

The number of plates used to make the C3 heat pipe is reduced.

On the figures 7A to 10 , one can see other embodiments of heat pipes according to the invention in which some of the plates used have a window and recesses.

On the figure 7A , the heat pipe C4 comprises between two closure plates 312, a stack of groups of plates H1, H2 ... Each group comprising two first intermediate plates 314 and a second intermediate plate 316 disposed between the two first intermediate plates 314.

The second intermediate plate 316 is similar in shape to the second intermediate plate 16.

The first intermediate plates 314 ( figure 7B ) have a central window 318 and two side recesses 319 made in one of the faces of the first plates 314.

In the Z direction, the first intermediate plates 314 have a thickness e1 and the recesses 319 have a depth p1 less than the thickness e1.

The recesses 319 are bordered by a frame 319 '. The dimension along the Y direction of the window 320 of the second intermediate plate 316 is equal to the distance between the outer edge of a recess 319 and the outer edge of the other recess 319.

During assembly, in each group the first intermediate plates 314 are arranged on either side of the second intermediate plate 316 with the recesses 319 facing each other. Thus the liquid channels 310.2 of the grooves 310 are delimited by the recesses 319.

The width in the Z direction of the exchange zone 310.1 is equal to the thickness e2 of the second intermediate plate and the width of the liquid channel 310.2 in the Z direction is equal to 2e1 + e2.

This example of a heat pipe offers better mechanical strength of the grooves, in fact the first plates have greater strength. In addition, this exemplary embodiment has the advantage of not requiring the implementation of third intermediate plates, and sealing is simpler to achieve because of the reduced number of interplate interfaces.

The windows 318 of the first intermediate plates 314 are for example made by punching and the recesses 319 are made by machining.

On the figure 8 , we can see another embodiment of a C5 heat pipe.

As for the heat pipe C4, the first intermediate plates comprise a central window 418 and two lateral recesses 419 on either side of the central window.

Unlike the C4 heat pipe, the C5 heat pipe does not have a second intermediate plate between the two first intermediate plates 414. These are the first intermediate plates which define both the exchange zone 410.1 and the liquid channel 410.2.

On the figure 8B , we can see a top view of a first intermediate plate 414, and on the figure 8C a sectional view can be seen along the Y direction of the first spacer plate 414. It includes the central window 418 and the recesses 419.

The recesses 419 have three contiguous outer edges 419.1 located on the contiguous outer edges of the plate 414, and an inner edge 419.2 on the side of the window 418.

The outer edges 419.1 have a thickness in the Z direction equal to the thickness e1 of the plate 419, and the inner edge 419.2 has a thickness h1 less than the thickness e1. Thus when two first intermediate plates 414 are brought into contact with each other with their recesses 419 facing each other, the inner edges 419.2 of the two facing recesses are not in contact and leave a space forming the exchange zone 410.1 . The exchange zone then has a width in the Z direction equal to 2x (e1-h1).

This exemplary embodiment has the advantage of offering improved mechanical strength of the grooves, of further reducing the number of different parts required to produce the heat pipe and of further simplifying the production of the seals.

On the figure 9 , we can see another embodiment of a C6 heat pipe.

In this example, the first intermediate plates 514 have recesses in their two faces and thus participate in each delimiting two grooves 510 in the Z direction. A second intermediate plate 516 is disposed between two first intermediate plates and defines the width in the Z direction. of the exchange zone 510.1. In this example, the edges of the recesses all have the same thickness.

Alternatively, the inner edge of the recesses is thinned.

On the figure 10 , one can see another example of a C7 heat pipe comprising two closure plates 612 and first intermediate plates 614 comprising recesses on their two faces, the recesses comprising an inner edge 619.2 thinned with respect to the outer edges 619.1. The exchange zone is delimited by the thinned inner edges 619.2.

The number of plates is reduced, which simplifies assembly and further reduces the number of interfaces, and therefore the risk of leakage.

As a variant, the stack comprises first plates provided with recesses and a third plate which defines, with the first plate, the exchange zones.

The first intermediate plates of the examples of figures 9 and 10 can be made by extrusion. In this case, the plates do not come from clad sheets, and they are advantageously welded to each other with a laser by transparency layer by layer.

In the examples of figures 7A to 10 , the cut of the recesses along the Y axis has a rectangular shape.

On the figures 11A and 11B , one can see other examples of first intermediate plates 714 and 814, seen in section, provided with recesses 719, 819 on either side of the central window 718, 818.

On the figure 11A , the inner face 719.21 of the inner edge 719.2 of the recess 719 is inclined towards the open face of the recess.

On the figure 11B , the inner face 819.21 and the bottom 819.3 of the recess 819 are connected by a connection fillet.

These forms of recess advantageously ensure an increase in the progressive section between the exchange zone and the liquid channel, which has the advantage, in the case of retraction of the meniscus beyond the exchange zone, of making more gradual decrease in capillary pressure.

On the figure 12 , we can see a partial view of another example of a C8 heat pipe having variable section liquid channels.

In this example, the side windows 919 of the first spacer plate 914 have a trapezoidal shape in the XY plane, the large base 919.1 being located on the side of the condenser zone and the smaller base 919.2 being located on the evaporator side.

The section of the liquid channel is smaller at the evaporator, where the liquid flow rate is less, and the exchange zone is larger in order to be able to accept a greater meniscus retreat.

On the figure 13 , we can see a sectional view along the YZ plane of the groove at the level of the condenser zone and on the figure 14 , a sectional view along the YZ plane at the level of the evaporator zone. The exchange zone 910.1 has a larger dimension in the Y direction at the level of the evaporator zone than at the level of the condenser zone. This longer exchange zone allows the meniscus of the liquid to move back more in the evaporator zone, which reduces the risk of the meniscus entering the liquid channel, and therefore reduces the risk of a sudden decrease in capillary pressure. Such a decrease can cause the heat pipe to defuse. The arrows symbolize the circulation of the fluid between the condenser zone and the evaporator zone, in the vapor channel and in the reentrant grooves.

In this example, the lengthening of the exchange zone at the level of the evaporator zone has the effect of reducing the section of the liquid channel 910.2 at the level of the evaporator zone. However, since the liquid flow rate is lower in the evaporator zone, the liquid pressure drop is little increased, and the capillary limit is little reduced.

On the figure 15 , one can see an alternative embodiment of the first intermediate plate 1014 in which the side windows 1019 have a trapezoidal shape, the large base being located on the side of the condenser zone and the smaller base being located on the evaporator side; and the central window 1018 also has a trapezoidal shape, the larger base being on the evaporator zone side and the smaller base being on the condenser zone side. This variant makes it possible to optimize the losses of liquid and vapor pressure.

On the figure 16 , we can see another example of a C9 heat pipe according to the invention incorporating a thermal diffuser in order to homogenize the flow.

The closure plates 12 'have a larger area than those of the stack in the YX plane so that they protrude on either side of the stack. The heat flow then spreads over a larger area, which ensures homogenization of the flow.

The heat pipe may have closure plates with a larger surface only in the useful zone or zones, i.e. in the condenser zone and / or in the evaporator zone. The surface of the plates is advantageously reduced in the non-useful zone, for example cut before or after assembly, which makes it possible to reduce the mass of the heat pipe.

The implementation of such closure plates also applies to multichannel heat pipes.

On the figure 17 , we can see an example of a C10 heat pipe suitable for high pressure operation, by reinforcing the internal structure of the heat pipe.

In this example, the heat pipe C10 has two steam channels each surrounded by two reentrant channels, instead of a steam channel if we consider the Y direction as the heat pipe C1.

This arrangement makes it possible to obtain improved pressure resistance compared to the heat pipe C1. On the other hand, if each reentrant channel heat pipe is filled individually, the failure of a heat pipe makes it possible to keep 50% of the entire transport capacity. The thickness of the wall between two vapor channels can be thinner than the outer walls which have to maintain a higher pressure difference. The heat pipe C10 has a lower limit power than that of the heat pipe C1, but the thermal resistance, which is linked to the surface of the exchange zones, is lower.

On the figure 18 , the heat pipe C11 comprises a partition 24 in the vapor channel mechanically connected to the two closure plates and providing reinforcement of the heat pipe in the Z direction.

The partition 24 is formed by stacking the plates. The partition 24 may be such that it provides fluid communication between the two parts of the steam channel, which simplifies filling. As a variant, the partition 24 so separates the steam channel and two steam half-channels, which allows in the event of failure of one of the half-heat pipes to retain 50% of the transport capacity.

On the figure 19 , the stack comprises reinforcing strands 26 extending in the Y direction and which pass through the channel. In this example, the strands are formed by the third intermediate plate 17 which is visible on the figure 20 . The strands 26 connect the two uprights 28 of the third intermediate plate and define a plurality of windows.

The reinforcement of the internal structure of the heat pipe can also be obtained by increasing the thickness of the walls formed by the stacking of the plates.

In the examples described above, the edges of the openings defining the grooves are straight and parallel to each other.

On the figure 21 , one can see the first insert plates 1114 comprising windows 1118 comprising side edges 1118.1 corrugated.

This shape makes it possible to increase the length of the triple line (connection zone between liquid / vapor and wall), in particular in the evaporator zone, which makes it possible to increase the heat exchange coefficient in evaporation.

At the level of the condenser, the corrugated shape makes it possible to obtain walls not wetted by the condensation film at the tops of the corrugations. This also makes it possible to increase the condensation exchange coefficient by minimizing the interface resistance of the condensation film. In addition, at the condenser level, the meniscus is flush with the vapor zone, which increases the condensation surface.

The corrugations can be provided at the level of the condenser zone, and / or at the level of the evaporator zone. Advantageously, the corrugations are formed over the entire length of the heat pipe, which simplifies the production and makes it possible to adapt to different lengths of the condensation zone or of the evaporation zone.

In this example, the bottom of the grooves is planted.

On the figure 22 , we can see a variant, in which the edges 1218.1 of the central windows 1218 are sawtooth. The exchange coefficients in condensation and evaporation are also increased.

It will be understood that any other form is possible. In view of the embodiment of the openings, great freedom in the shape of the edges exists.

It can even be envisaged to produce straight edges in one lateral face of the channel and wavy edges in the other facing face.

On the figure 23 , one can see an embodiment of a multichannel heat pipe offering a simplified filling.

The filling of a single-channel heat pipe can be done by means of a filling plug inserted on the edge of the stack or by means of a plug fixed on an orifice made in one of the closure plates, for example perpendicularly. to these.

In the case of a multichannel heat pipe, which in fact comprises a plurality of heat pipes, provision can be made to fill each heat pipe separately.

According to a very advantageous variant, provision is made to put all the channels in communication so as to be able to fill all the channels by a single queusot. In the example of figure 23 , one channel connects all the channels. This channel is for example formed by a transverse slot 30 formed on an edge of one of the third intermediate plates 1317. Furthermore, the side windows 1319 of the first plate 1317 are extended along the X axis so that, when stacking in the Z direction, the longitudinal ends of the side windows 1319 are in line with the light 30.

Thus by making an opening in one of the closure plates opening into the lumen 30, it is possible to fill all the channels. Those are the side windows which communicate with the light 30 because it is they which form the zones of circulation of the liquid.

On the figure 24 , one can see another exemplary embodiment in which the heat pipe C12 does not have a straight shape, it comprises two straight portions D1 and D2 oriented at right angles to one another. In addition, the portions D1 and D2 extend in orthogonal planes. The portion D1 extends in the XY plane and the portion D2 extends in the XZ plane. The orientation of the portions D1 and D2 with respect to each other is for example obtained by folding after stacking of the plates and their securing. P1 designates the fold.

The C12 heat pipe can be conformed to the application. The heat pipe may have several folds.

In this example, the portion D1 forms the evaporator and the portion D2 forms the condenser and, on its outer surfaces, is provided with fins A1 forming a radiator making it possible to evacuate the heat. The radiator works for example in natural convection or in forced convection. In this example, the fins A1 are provided on the two large surface faces of the condenser. As a variant, fins could be envisaged on a single face.

In this example, the fins have flat plates perpendicular to the faces of the condenser. Any other form is possible.

On the figures 25A to 25F shown are pleated fins according to other exemplary embodiments applicable to the present invention.

According to other examples, the fins are extruded fins, skived fins, pin fins, molded fins, fins fixed by knurling, fins produced by 3D printing, or any other fin obtained by a technique for producing extension of surface well known to those skilled in the art.

One or more finned radiators as described above can be implemented in a single-channel or multi-channel heat pipe straight or having any other shape.

As a variant, a cooling circuit is integrated directly into the heat pipe C13 as shown in the figure. figure 26 .

The heat pipe comprises a cooling circuit 32 in which a heat transfer fluid is intended to circulate. The cooling circuit is in direct contact with the condenser. In the example shown, the cooling circuit 32 is formed by an additional plate 36, in which are formed grooves 38 defining the side walls of the circuit, and the closure plate 12 and an additional closure plate 40 form the walls d end of the cooling circuit. The closure plate 12 has two orifices 42 each opening at one end of the circuit and allowing the circulation of the heat transfer fluid.

The heat transfer fluid can be a liquid or a gas.

According to another example, it is a two-phase circuit.

Such a circuit can also be used to form the hot source at the level of the evaporator.

We will now compare the performance of a heat pipe according to the invention as shown in figure 16 , and a heat pipe with capillary pumping reentrant grooves of the state of the art.

We consider a heat pipe of the prior art cylindrical obtained by extrusion and comprising reentrant grooves 1310, as shown in Figure figure 27 .

Each heat pipe has an evaporator length of 200 mm, an adiabatic zone length of 600 mm, a condenser length of 200 mm (total length 1m).

Each heat pipe is made of aluminum alloy. The working temperature in the adiabatic zone of the heat pipe is 60 ° C; i.e. the mean vapor temperature of the heat pipe. The working fluid is ammonia.

The heat pipe according to the invention has the following characteristics:
The heat pipe has a section of 13.2mm x 13.2mm and wings formed by the closure plates of 30mm in the Y direction.

• Largeur des rainures liquides ré entrantes 1, 8 mm
• Hauteur des rainures liquides réentrantes 1,2 mm
• Largeur des rainures dans la zone d'échange 0,2 mm
• Longueur des rainures dans la zone d'échange 1 mm
• Nombre de rainures : 14.
• Masse à vide : 367g

It therefore has the same size as the heat pipe of the state of the art.

• Width of re-entering liquid grooves 1, 8 mm
• Height of reentrant liquid grooves 1.2 mm
• Width of the grooves in the exchange zone 0.2 mm
• Length of the grooves in the exchange zone 1 mm
• Number of grooves: 14.
• Empty weight: 367g

The heat pipe section is shown in Figure 16 .

The heat pipe of the state of the art has an external size close to that of the heat pipe according to the invention above and has a mass of 300 g.

On the figure 28 , we can see the evolution of the capillary limit Lc in Watt as a function of the temperature T in ° C, for a weightless operation (zero inclination). Curve I corresponds to the invention and curve II to the heat pipe according to the state of the art.

It can be seen that the heat pipe according to the invention has, with identical dimensions, a limit power of 4 to 6 times greater than that of a heat pipe of the state of the art, for a slightly greater mass.

Furthermore, it is noted that to obtain the same powers as a heat pipe of the state of the art, the heat pipe according to the invention only requires two levels of grooves, i.e. four grooves.

This heat pipe will for example be of identical width less thick, it is shown in figure 33 .

For example for a maximum power of 220 W:
The heat pipe of the figure 33 has a section of 13.2 mm x 4.9 mm and wings formed by the closure plates of 30 mm in the Y direction, and a mass of 210 g.

The cylindrical heat pipe of the state of the art has a section of 13.2 mm × 13.2 mm and wings formed by the closure plates of 30 mm, and a mass of 300 g.

A gain in empty weight of 30% and a gain of 68% in the thickness of the heat pipe can be obtained by virtue of the invention compared with the cylindrical heat pipes with reentrant grooves of the state of the art. In addition, the thermal resistances of the fluxes between the hot and / or cold sources are more advantageous in the heat pipes depending on that in the cylindrical heat pipes with reentrant grooves. In fact, the cylindrical heat pipes with reentrant grooves of the state of the art have a more marked reduction in the transmission cross section of the flux by conduction (constriction of the heat flux by conduction) which is unfavorable to thermal resistances. In addition, the thermal path is more complex and longer with the heat pipes of the state of the art.

We will now describe a cooling system comprising a plurality of heat pipes which can develop in two or three dimensions and thus be mounted on devices whose thermal behavior is to be controlled.

On the figure 29 , one can see heat pipes according to the invention, such as that of the figure 1 , arranged in the form of a lattice, the heat pipes C1 and C1 'crossing at right angles in the example shown. In addition, in this example, the heat pipes C1 are bent so as to deploy in two perpendicular planes. The heat pipes C1 extend along the axis a1 and the heat pipes extend along the axis a2.

The heat pipes may or may not be fluidly connected.

In the case of a fluidic connection, the heat pipes in the same plane can communicate with each other thanks to openings made in the intermediate plates, as shown on the figure. figure 23 .

The example in which the heat pipes are not fluidly connected to one another has the advantage of offering redundancy in the event that one of the heat pipes is faulty.

On the figure 30 , we can see a cross-sectional view at a node of a heat pipe C1 and a heat pipe C1 ', in the case of a heat pipe not fluidly connected.

Very advantageously, a closing plate of a heat pipe C1 also forms the closing plate of a heat pipe C1 ′.

• une première plaque de fermeture pour les caloducs C1 s'étendant le long de l'axe a1,
• un assemblage de tôles d'espacement et comportant des ouvertures ou des évidements pour former les caloducs C1 selon la présente invention,
• une deuxième plaque de fermeture pour les caloducs C1 et servant aussi de plaque de fermeture pour les caloducs C1' s'étendant suivant l'axe a2,
• un assemblage de tôles d'espacement et comportant des ouvertures ou des évidements pour former les caloducs C1' selon l'invention,
• une troisième plaque de fermeture pour les caloducs C1'.

For example, for this we carry out a stack of sheets with:

• a first closure plate for the heat pipes C1 extending along the axis a1,
• an assembly of spacers and comprising openings or recesses to form the heat pipes C1 according to the present invention,
• a second closing plate for the heat pipes C1 and also serving as a closing plate for the heat pipes C1 'extending along the axis a2,
• an assembly of spacing sheets and comprising openings or recesses to form the heat pipes C1 ′ according to the invention,
• a third closure plate for the heat pipes C1 '.

The tooling for maintaining pressure during brazing is preferably flat and will rest on the outside of the two closure plates. The sheets cover the entire surface before brazing. It is nevertheless possible to open the sheets before assembly in order to lighten the assembly.

Then, the stack is brazed flat in a vacuum oven

After brazing, it is possible to eliminate by machining, trimming, cutting out the unnecessary zones in order to obtain the desired geometry and to lighten the structure as much as possible.

In the example of figure 29 , the sheets of the heat pipes C1 'above the heat pipes C1 are removed by machining.

In the example shown, the inter-heat pipe spaces are perforated.

You can then make the folds
It may be advantageous to standardize the heat pipe trusses with a given spacing.

Depending on the application, this trellis is hollowed out.

On the figure 31 , we can see a variant of the figure 29 comprising mechanical reinforcements formed by a metal veil 44. As a variant, several sails can be implemented, for example one on each side of the heat pipe mesh. A metal veil is a very thin metal sheet, typically of the order of 0.2 mm, which is for example glued to the heat pipes.

On the figure 32 , we can see a variant of the figure 29 comprising a heat exchange circuit 46 for removing heat from a single-phase circuit, or the condenser of a two-phase cooling circuit. The heat is then removed by radiation through the network of heat pipes C1 and C1 '.

Thanks to the invention, a crossed heat pipe system can be made in one piece, ie the interfaces between the intersecting heat pipes are formed by a plate common to the intersecting heat pipes, and not by two plates in contact with one another. with the other. Thus the thermal interface resistances at the node of the trellis are appreciably reduced. In addition, the trellis can be self-supporting, which can make it possible not to have to implement an additional support structure.

It will be understood that any other assembly geometry can be envisaged, for example the heat pipes can form a lattice in which the heat pipes cross at a non-right angle. The angle may vary over the entire surface of the trellis. In addition, the spacing between the heat pipes can be variable. In addition, the mesh can include heat pipes of different sizes.

It will be understood that the different examples and variant embodiments are not mutually exclusive and can be combined in whole or in part. Thus, the embodiment of the figure 6 can be combined with that of the figure 8 , the exchange zones being delimited between a first plate and a third plate, the interior uprights of the side windows being thinned.

The heat pipe according to the invention can be made of different materials such as, for example, an aluminum alloy, copper or stainless steel.

The technique of joining the sheets depends on the material.

For example, in the case of aluminum alloy plates, vacuum brazing with clad plates, salt bath brazing, inert gas brazing, ultrasonic welding, laser welding, laser welding, or welding can be used. friction-kneading (Friction Stir Welding), gluing ...

In the case of a copper, stainless steel or superalloy plate, diffusion welding, laser welding, diffusion brazing, bonding ... the material (s) used for the manufacture of the heat pipe are chosen according to the constraints of mass, assembly, required robustness ...

In the case of plates in stainless steels, super alloys, diffusion welding, laser welding, diffusion brazing, bonding ...

By way of example, the assembly of aluminum alloy plates is obtained by eutectic brazing. Aluminum alloy plates are used in known manner, one or both faces of which is or are coated with an aluminum alloy with a lower melting point.

For example, an alloy sheet of the AA3xxxx series with the core is used, with a coating with a eutectic alloy of the AA4xxxx series comprising silicon with a lower melting point.

Coating is typically done by a roll-bond technique.

The total thickness of the plates is typically 0.05mm to 5mm, with a coating typically of 5% to 10% of the total thickness on one or both sides.

By hot pressing two aluminum plates thus coated at a temperature above the melting point of the eutectic, but below the temperature of the core alloy, the eutectic alloy on the surface melts and forms a brazing alloy. tight assembly between the two plates.

The brazing is preferably carried out under pressure by means of a mechanical holding system, which maintains the stack under pressure during the brazing in a vacuum furnace.

Cutouts and / or folds are required in the manufacturing process to lighten and / or shape the structure. They are preferably made after assembly. It should be noted that the cutting of the windows in the plates, for example the central windows, is carried out before assembly.

An example of a method for producing a C1 heat pipe according to figure 2 will now be described.

Plates of a given material are cut to the desired outer shape for the heat pipe.

In a following step, the first, second and third intermediate plates are structured, for example by punching, machining, cutting laser, by water jet cutting or through chemical etching ... in order to create specific windows in the different plates, so that once assembled a reentrant grooved heat pipe is formed.

The plates are then stacked in a given order, for example by alternating a second intermediate plate and a third intermediate plate between two first intermediate plates; closure plates are arranged at the ends of the stack to close the channel or channels. Optionally, cooling channels are provided on one or both sides of the stack.

The plates are assembled, the assembly technique being chosen as a function of the material (s) of the plates, for example welding, brazing, gluing, etc., the assembly of the plates is sealed. The material or materials of the plates is or are chosen according to the working fluid, which is itself chosen according to the thermalization specifications of the system to be produced.

The heat pipe is then filled. A filling orifice was made in one of the opening plates during the manufacture of the plates. The fluid is chosen according to the operating conditions of the heat pipe (operating temperature, etc.) and the compatibility with the material or materials of the heat pipe.

Thanks to the invention, the thermal performance in terms of maximum transportable power of heat pipes with reentrant grooves is improved compared to heat pipes with reentrant grooves of the state of the art, i.e. cylindrical heat pipes with reentrant grooves. Thus, it is possible to produce heat pipes having the same size and capable of transporting more power or having a reduced size and mass while transporting the same power.

• d'obtenir une forme et une surface différente entre la partie évaporateur et la partie condenseur des caloducs,
• d'obtenir une largeur de zone d'échange plus étroite pour avoir une pression capillaire importante,
• d'obtenir une longueur transverse de zone d'échange plus longue afin d'accommoder une reculée du ménisque dans la zone évaporateur plus importante sans risque de désamorçage large du caloduc,
• d'obtenir des rapports d'aspect entre section du canal liquide et largeur de la zone d'échange (interface liquide/vapeur) plus favorables, i.e. offrant une meilleure capacité de transport linéique pour un encombrement donné, ou masse réduite pour une capacité de transport linéique fixée,
• de réduire les résistances thermiques de flux entre les sources chaude et froide et les parties évaporateur et condenseur du caloduc.

In addition, by comparison with heat pipes obtained by extrusion, the invention allows:

• to obtain a different shape and surface between the evaporator part and the condenser part of the heat pipes,
• to obtain a narrower exchange zone width in order to have a high capillary pressure,
• to obtain a longer transverse length of the exchange zone in order to accommodate a retreat of the meniscus in the greater evaporator zone without the risk of wide defusing of the heat pipe,
• to obtain more favorable aspect ratios between section of the liquid channel and width of the exchange zone (liquid / vapor interface), ie offering a better linear transport capacity for a given size, or reduced mass for a capacity of fixed linear transport,
• to reduce the thermal resistance of the flow between the hot and cold sources and the evaporator and condenser parts of the heat pipe.

In addition, the fact of using several stacked plates makes it possible to use cut plates forming the channels communicating with each other while maintaining mechanical cohesion of each plate.

In the case of plates structured by punching, the cost price of the heat pipes is reduced for medium and large series, while optimizing the heat transfer along the length of the heat pipe.

In the case of sheet metal machined to make recesses (example of realization of figures 7A to 10 ), the second intermediate plates can be omitted, which reduces the number of parts used. In addition, the plates have increased strength.

Claims (15)

1. Capillary pumped heat pipe with reentering grooves extending at least along a first longitudinal direction (X), comprising a first longitudinal end (4) intended to be heated and a second longitudinal end (6) intended to be cooled, a sealed enclosure (2) extending between the first end (4) and the second end (6), the enclosure comprising a stack of plates along a second direction (Z), said stack comprising two closure plates (12), at least one module with at least two intermediate plates (14, 16, 17, 214, 216, 217, 314, 316, 317) between the closure plates (12), the heat pipe being characterised in that said intermediate plates include at least one first intermediate plate (14, 214, 314) including at least one central window (18, 118, 318) the edges of which partially define a vapour channel (8) extending along the first direction (X), in which the vapour is intended to circulate, and on each side of the at least one central window (18, 118, 318) in a third direction (Y) orthogonal to the first (X) and the second (Z) directions, a structure, the edges of which partially define a liquid channel, at least one other intermediate plate having at least one window, the edges of which partially define the vapour channel (8), and wherein the heat pipe includes at least two exchange zones (10.1, 110.1, 310.1) defined between the at least one intermediate plate and the at least one other intermediate plate, linking the vapour channel and the liquid channel.
2. Capillary pumped heat pipe with reentering grooves according to claim 1, wherein the at least one other intermediate plate is the at least first intermediate plate (314), and wherein the structures are recesses (319) produced in at least one of the faces of said first intermediate plates (314), wherein, in the stack, the recesses (319) are placed opposite, and wherein the exchange zones (310.1) are defined by two edges of two recesses (319) of the two facing intermediate plates (314), the first intermediate plates advantageously including recesses in their two faces.
3. Capillary pumped heat pipe with reentering grooves according to claim 2, wherein a second intermediate plate (316) is interposed between two first intermediate plates (314) at the outer edges of the first intermediate plates (316), the thickness of which defines the dimension in the direction of the stack of exchange zones (310.1), and/or wherein the recesses have a bottom and at least one edge linking the bottom to the exchange zone, said edge being inclined away from the vapour channel or said edge connecting to said bottom via a fillet.
4. Capillary pumped heat pipe with reentering grooves according to claim 1, wherein the other plate is a third intermediate plate (217) the window of which has the same cross-section as the central window of the first intermediate plate (214) so that two of its side edges in the third direction (Y) define, with the first intermediate plate (214), exchange zones (210.1), a second intermediate plate (216) being advantageously interposed between the first intermediate plate (214) and the third intermediate plate (217) at the outer edges of said first and third intermediate plates, the thickness of which defines the dimension in the stacking direction of the exchange zones.
5. Capillary pumped heat pipe with reentering grooves according to claim 1, wherein the other intermediate plate is a first intermediate plate (14), wherein the structures are windows (19), wherein the heat pipe includes a second intermediate plate (16) interposed between the two first intermediate plates (14) at the outer edges of the first intermediate plates (14), the thickness of which defines the dimension in the stacking direction of the exchange zones (10.1), and wherein the heat pipe includes a third intermediate plate (17) the window of which has the same cross-section as the central windows (18) of the first intermediate plates (14), in contact with one of the first intermediate plates (14) and closing off the side windows (19) on either side of the central window (18) in the second direction (Z).
6. Capillary pumped heat pipe with reentering grooves according to one of claims 1 to 5, including n modules one on top of the other, n being an integer > 1, defining a single vapour channel and n liquid channels on each side of the liquid channel and n exchange zones, each connecting the vapour channel to a liquid channel.
7. Capillary pumped heat pipe with reentering grooves according to one of claims 1 to 6, wherein the structures have a trapezoidal shape in a plane orthogonal to the second direction, and/or wherein the central windows of the intermediate plates include a post extending in the first direction so that the vapour channel includes a wall extending over the entire height of the stack and in the first direction.
8. Capillary pumped heat pipe with reentering grooves according to claim 4 or 5, wherein the window of at least one third intermediate plate includes at least one transverse post extending in the third direction.
9. Capillary pumped heat pipe with reentering grooves according to one of claims 1 to 8, including a plurality of vapour channels, each connected to liquid channels by exchange zones.
10. Capillary pumped heat pipe according to one of claims 1 to 9, wherein at least one of the end plates has a surface area greater than that of the intermediate plates in a direction transverse to the stack so as to form heat spreaders.
11. Capillary pumped heat pipe with reentering grooves according to one of claims 1 to 10, including heat exchange means at the first end and/or second end, the heat exchange means at the second end advantageously including one or more fins in thermal contact with at least one of the closure plates.
12. Capillary pumped heat pipe, according to claim 11, wherein the heat exchange means include a fluid circuit (32) in thermal contact with at least one of the closure plates (12), said circuit being formed by a plate (36) structured so as to define channels (38), said channels (38) being closed by said closure plate (12) and an additional closure plate (40), the heat exchanger means also including means for supplying said fluid circuit with heat transfer fluid.
13. Heat exchange system having a plurality of heat pipes according to one of claims 1 to 11, wherein the heat pipes are disposed in a plurality of planes, the heat pipes of two successive planes crossing each other and wherein the heat pipes of two successive planes share a same end plate, at least one heat pipe of one layer being advantageously hydraulically connected to at least one heat pipe of the same layer.
14. Heat exchange system according to claim 13, including a single phase or two-phase heat exchange circuit.
15. Method for manufacturing a capillary pumped heat pipe according to claim 1, including, starting from two outer plates of given outer dimensions:

    - producing at least one central window in at least two plates,

    - structuring, on each side, the at least one central window in at least one of said plates, in order to form side windows or side recesses,

    - stacking said plates so that the central windows define a vapour channel, so that the side windows or recesses form liquid channels on either side of the vapour channel, and so that the exchange zones connect the vapour channel to the liquid channels,

    - placing closure plates at the ends of the stack in the stacking direction,

    - joining said plates so as to define a sealed enclosure, said plate advantageously including an aluminium alloy at the core and, on their outer faces, a eutectic aluminium alloy with melting point less than that of the core aluminium alloy and the joining being obtained by eutectic brazing;

    - partially filling the channel with a fluid in liquid form and sealed closure of the channel.

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