EP2344827B1 - Thermal control device with network of interconnected capillary heat pipes - Google Patents

Description

The present invention relates to a thermal control device of the type based on capillary heat transfer fluid flow heat exchangers, used for cooling, respectively heating, hot springs, respectively cold, and interconnected in at least one network. The document US 5,216,580 discloses a corresponding preamble device of claim 1.

The object of this claim differs from this device in its characterizing part. While a capillary tube is a simple hollow tube whose internal wall is smooth, a heat transfer capillary heat pipe 1 is formed, in a most common and economical variant of the state of the art, and as shown schematically in longitudinal and transverse sections on the Figures 1a and 1b respectively, a hollow tube 2 having longitudinal internal grooves 3 extruded in the mass from its inner face and surrounding a central channel 4.

In other variants, as shown schematically on the cross-section of the figure 1c , the central channel 4 is surrounded by a substantially annular structure of a porous material such as, for example, porous copper, or any other porous structure 5, lining the inner wall of the tube 2. These particular structures (grooves 3, structure or porous material 5) are hereinafter referred to as "capillary structures", and are generally disposed at the inner surface of the tube 2 of the capillary heat pipe 1 to retain the liquid phase of a heat transfer fluid at this level, and separate it from the vapor phase, which circulates in the central channel 4. The heat pipe 1 thus has two different capillary dimensions (for example the diameter of the central channel 4 and the thickness or radial dimension of the capillary structure 3, 5), which allows a dissociated flow (co-current or countercurrent) of the liquid phase and the vapor phase of the fluid used to transport the heat.

A capillary heat pipe 1 according to the state of the art generally comprises a linear tube 2, or having at least one section, closed at its two ends, and filled with a two-phase heat transfer fluid at a suitable pressure, allowing the transport of heat by vaporization, flow of the vapor, then condensation of the fluid.

The capillary heat pipe 1 is generally in the form of a bar, possibly bent in some places, whose dimensions are adapted as needed. The cross section of the tube 2 may for example be circular or quadrangular. The tube 2 may be in direct thermal contact with at least one hot source such as 6 in FIG. 1a and at least one cold source such as 7 on the figure 1a or in thermal contact with at least one sole, itself in thermal contact with at least one hot source or at least one cold source.

The capillary heat pipe 1 connects one or more hot springs 6 (for example heat-dissipating electronic equipment or heaters), at an evaporation zone 8, to one or more cold sources 7 (for example radiators, or equipment or structures to be heated), at a condensation zone 9. The liquid phase of the fluid flows from the condensation zone 9, in heat exchange relation with the cold source or sources 7, towards the evaporation zone 8, in heat exchange relation with the hot source (s) 6, through the capillary structure 3, 5 lining the wall of the tube 2. In the evaporation zone 8, in contact with the hot source (s) 6, the liquid vaporizes, and the vapor thus formed is evacuated through the central channel 4 of the tube 2 to the condensing zone 9, where the vapor condenses in the liquid phase by releasing heat towards the cold source or sources 7.

In contrast to a capillary heat pipe 1 as described above with reference to Figures 1a-1c, there are so-called oscillating heat pipes, constituted by simple capillary tubes (hollow tubes of small internal diameter, for example 2 to 5 mm) connected and interconnected end to end to form one or more loops. This closed capillary duct, whose opposite ends of the loop or loops are in heat exchange relation with, on one side, an evaporator, and, on the other side, a condenser, is filled with a heat transfer fluid present. in its two phases (liquid and vapor). The flow of The phases are exclusively co-current, with segments or "plugs" of liquid being pushed by steam bubbles formed by heat absorption at the evaporative zone thermally coupled to one or more hot sources. Thus, the closed capillary duct, partially filled with liquid placed by the evaporation zone in thermal contact with the hot source or sources, promotes the successive expansion of vapor bubbles of a length of up to several millimeters (typically 5 to 10 mm). The expansion of these vapor bubbles pushes "corks" of liquid at their ends and steam bubbles between successive "plugs" of liquid, so that the movement of these plugs and bubbles puts liquid and steam in thermal contact, through the condensing zone, with one or more cold sources, which condenses vapor into liquid. Thus the flow of the liquid fluid in this closed circuit promotes the return of liquid to the evaporation zone, and the generation of a new bubble at the latter. As a result, the liquid segments and gas bubbles move globally and alternately to the evaporation zone and to the condensation zone.

Oscillating heat pipes of this type are described for example in US 4,921,041 and US 5,219,020 which will be referred to for more details about them.

The operation of a capillary heat pipe is therefore different from, and much more efficient than, that of a simple capillary tube used in oscillating heat pipes or in co-current heat pipes according to US6,269,865 and as described below with reference to the figure 2 (which corresponds to the figure 3 of US6,269,865 ). Indeed, a capillary tube whose internal wall is smooth, is limited in pumping capacity to a value inversely proportional to the diameter of the tube, less than 100 Pa. A capillary heat pipe, given the small capillary dimension of the structure porous or grooves in the inner wall, allows to achieve pumping capacities greater than 500 Pa. Unlike a capillary tube, a capillary heat pipe allows, moreover, to homogenize the temperature along the tube of the heat pipe, the phases liquid and vapor fluid flowing independently of each other in both directions of the tube according to different hot spots and cold spots along the heat pipe.

As shown on the figure 2 , US6,269,865 discloses a network heat pipe 11 of simple capillary tubes 12 interconnected forming closed loops 13, substantially square or rectangular, in communication with each other and with two capillary tubes 12a and 12b respectively, which close at opposite ends of the a heat exchanger. This exchanger can operate as an evaporator 18, if it is in thermal contact with at least one hot source 16 and if the network 11 operates in heat dissipation unit, in thermal contact with at least one source cold or heat sink. This exchanger can also operate in condenser 19, if it is in thermal contact with at least one cold source and if the network 11 operates in a heat capture unit, in thermal contact with at least one hot source.

In the network 11, we clearly see the succession of liquid plugs 14 and vapor bubbles 15. This type of network 11 is used to dissipate heat produced in a hot source such as 16. The performance limitations of such a system with respect to capillary heat pipes have been explained above. In addition, this network 11 operates only if it is connected to a heat absorption unit 18, in heat exchange relation with at least one hot source 16, this unit 18 being dissociated from the network 11 used for dissipation thermal. The absorption unit 18 must vaporize the fluid at the inlet 12a of the network 11 of capillary tubes. The steam 15 thus created is condensed at the level of the network 11 in contact with at least one cold source, forming as the liquid plugs 14 are pushed by vapor bubbles 15. The fluid in the liquid state 14 is evacuated at the outlet 12b of the network 11 and returned to the absorption unit 18. In this type of network 11, the liquid 14 and the steam 15 necessarily circulate in the same direction (co-current flows). The liquid 14 and the vapor 15 can not be distributed independently of one another within the network 11, thereby preventing the establishment of a diphasic regime anywhere in the network 11. The liquid 14, moreover no longer present as and as a result of the condensation of the fluid, has a much lower heat absorption capacity than that created by the vapor condensation 15. The accumulation of liquid 14 at certain locations of the network 11, in particular at the nodes 20 of the network 11 , that is to say the interconnections of at least two loops 13 of the network 11, slows the flow of steam 15. Overall, the flow of heat absorbable by the network 11 is limited, and the thermal load can not allocate effectively within the network 11.

US 5,506,032 , US 5,806,803 and US 6,776,220 describe networks of intersecting and non-interconnected capillary heat pipes (particularly at their intersections), used for the thermal regulation of walls (walls) carrying equipment. This type of two-dimensional networks, as schematically represented on the figure 3 attached, is formed of capillary heat pipes 21 (here represented as each formed of a tube 22 having a capillary structure with internal grooves 23 around a central channel) intersecting, extending in at least two different directions and coplanar, and in general substantially perpendicular, but without any interconnection between heat pipes 21, in the sense that the fluid contained in the heat pipes 21 can not flow from any heat pipe to at least one other. At the place where two heat pipes 21 intersect, the heat exchanges between the two heat pipes 21 can only be done by conductive exchanges, either by direct contact between the tubes 22 of the two heat pipes 21, or possibly at using at least one massive intermediate piece, a good heat-conducting material, coating the two heat pipes 21, at their intersection, and sometimes called sole, forming a thermal interface or a thermal bridge between these two heat pipes 21.

Thus, an important limitation of this type of passive thermal regulation device with intersecting capillary heat pipe network comes from the unavoidable thermal transfer losses at the crossings, and therefore constitutes a limitation in terms of power transported, as well as a limitation related to the maximum thermal flux density that a heat pipe 21 can withstand at a crossing. A quantity of heat collected by one of the heat pipes 21 of the network flows efficiently along this heat pipe 21, but can not flow efficiently in the other direction of the network, along the heat pipes 21 that it crosses and which extend in this other direction, for example advantageously to a cold source located in this other direction.

In the case where a hot source is arranged at a cross between two heat pipes 21, only these two heat pipes 21 can efficiently transport the heat in their respective direction, and cold sources must be disposed in at least one of these directions. Thus, to efficiently collect and evacuate the heat through such a network, it is necessary either to have a sufficient number of cold sources located in all directions of the network, which imposes development constraints, either to increase the thermal conductivity at the crossings of the heat pipes 21, which substantially increases the mass of the device. In addition, the entanglement of the heat pipes 21 increases the size of the device and does not allow for networks of small thickness. Finally, the low modularity of this type of network does not make it possible to simply and efficiently carry out heat evacuation in complex structural shapes, surface or volume. In particular, no three-dimensional generalization of this type of network is known. Such a generalization would encounter an even greater complexity, a low efficiency of heat exchange within the network, and a need for many cold sources in thermal contact with the heat pipes of the network.

The object of the invention is to provide a thermal regulation device with a capillary heat pipe network which overcomes all the aforementioned limitations of the state of the art and provides other advantages which are presented in the description which follows.

For this purpose, the subject of the invention is a thermal regulation device, comprising at least one capillary heat pipe network, each heat pipe comprising a tube enclosing a substantially annular longitudinal capillary structure, for the circulation of a two-phase heat transfer fluid in phase. liquid, and surrounding a central channel for the circulation of said two-phase fluid in the vapor phase, and characterized in that the tubes of at least two heat pipes of the network intertwine and are interconnected so that at each intersection of heat pipes forming a node of the network, a liquid phase fluid exchange can be performed by capillarity between the capillary structures of said at least two heat pipes, and simultaneously a fluid exchange in vapor phase can be effected by free circulation between the central channels of said at least two heat pipes.

In a first embodiment, there may be ends of heat pipes not connected to nodes of the network. These ends are then closed, for example, by welding, in order to retain the fluid in the network. In another variant, each end of each heat pipe is connected to a node of the network, except for one or more inputs / outputs of the network, in particular able to ensure the communication of the network with at least one extension of this network of heat pipes and / or with at least one other heat pipe network of said device.

In these variants, one or more heat pipes of the network can extend distances distant from the network, up to a few meters, to seek thermal contact with hot springs or cold sources remote from said network.

Advantageously, a fluid reservoir is connected to the network, for example at an input or an outlet of the network, in order to adapt the quantity of fluid present in the network to the variations in temperature of the network, particular to accommodate fluid expansion and condensed fluid level.

If, in what follows, a heat pipe part arriving at a node of the network is called branch, then, in order to allow an efficient transfer of heat through the entire network, the device of the invention is advantageously such that at each node of the network, the capillary structures of all the heat pipe branches leading to said node provide a capillary continuity for the fluid in the liquid phase, so that the fluid in the liquid phase arriving at said node in any heat pipe branch resulting in said node may flow by capillarity in all other heat pipe branches leading to said node. There is therefore capillary continuity for the liquid in all directions between the different branches leading to the nodes and through the nodes.

For the same purpose of enabling the most efficient heat transfer possible through the entire network, the device is advantageously such that at each node of the network, the central channels of all the heat pipe branches leading to said node ensure, simultaneously with the continuity of fluid flow in the liquid phase, a flow continuity of the fluid in the vapor phase, so that the vapor phase fluid arriving at said node by any heat pipe branch leading to said node, can flow into all other heat pipe branches leading to said node. There is continuity a steam flow conduit in all directions between the various branches leading to the nodes and through the nodes.

The capillary continuity provided to the different nodes must allow fluid in the liquid phase to flow by capillarity, in an area where the surface tension effects are predominant on the effects of gravity or inertia. It is not necessary to have perfect continuity of said capillary structures, but it must at least be ensured that there is not a discontinuity of the capillary effect at this level. Advantageously, for this purpose, at each node of the network, the capillary structures of the heat pipe branches leading to said node do not have any size discontinuity between them greater than the typical dimension of a pore or a groove of the capillary structure of the heat pipes, depending on whether this structure comprises respectively a porous material or grooves internal to the corresponding tube.

Similarly, the continuity of the fluid flow conduit in the vapor phase, provided at different nodes of the network, must allow the steam to flow by inertia. Thus, it is not necessary to have perfect continuity of the geometry of said duct, but it must at least be ensured that there is no significant loss of load at this level. Advantageously, for this purpose, and at each node of the network, the flow continuity of the fluid in the vapor phase is ensured, between the central channels of the heat pipe branches leading to said node, by a flow conduit of which at least a typical dimension or the passage section is substantially equal to at least one typical dimension or the passage section of the central channels of said heat pipe branches leading to said node.

However, in order to support higher flux densities, or for example to integrate in specific volumes or geometries, for reasons of network congestion, the presence of bends on certain heat pipes, or operation against gravity, at least one heat pipe of the network may comprise at least one branch which differs from the branches of at least one other heat pipe of the network, at the level of the capillary structure and / or at least one dimension typical of said heat pipe branch.

The device according to the invention is advantageously such that said at least one heat pipe network that it comprises is a two-dimensional network comprising two pluralities of heat pipes such that the heat pipes of each plurality are oriented over at least part of their length. substantially in one of two directions respectively inclined relative to each other, and preferably perpendicular to each other, so that the heat pipes of the two pluralities intercross and are interconnected at their crossing according to the characteristics described above. .

The device according to the invention can be generalized in that at least one network that it comprises is a three-dimensional heat pipe network comprising, at least one node of the network, at least three heat pipe branches oriented in at least one part of their length according to one respectively of three directions, inclined, two by two, with respect to each other, and preferably perpendicular to each other, two by two, said at least three branches of intersecting heat pipe and being interconnected according to the characteristics described above.

In a first embodiment of the device, at least one node of the network, the at least two heat pipes that intersect and are interconnected to said node have their respective tube and capillary structure cut into complementary shape cuts such as heat pipes. 'nest at the cutouts by reconstructing a wall continuity of the tubes, secured together along the cutouts, a capillary continuity along the capillary structures and a continuity of flow along the channels of said heat pipes. This embodiment is more particularly suitable for heat pipes of quadrangular section (rectangular or square) or circular forming a two-dimensional network. It is understood that, to prevent fluid leakage at a node thus formed, the continuity of the walls of the tubes of the two heat pipes, at their crossing, must be ensured, for example by an external welding of these tubes along cuts, the same continuity between the capillary structures disposed within the two tubes is more easily ensured if this capillary structure is made of a porous structure (of a porous material) rather than grooves.

It is understood that it is more difficult to generalize this embodiment to grooved heat pipes and / or three-dimensional networks, and that this embodiment is more suitable for two-dimensional networks and / or heat pipes. with porous materials.

Because of these limitations, in a second particularly advantageous embodiment of the device of the invention, the interconnection of the heat pipes at the level of at least one node, and preferably of all the nodes where at least two branches of heat pipe are connected together, is made in a modular manner, via a hollow junction piece, having in particular the appearance of a cross for a two-dimensional network node where four heat pipe branches are interconnected, and that, by generalization, it is called brace thereafter.

More specifically, in this second embodiment, the device is such that at least one node of the network comprises a hollow junction piece, said cross, ensuring the interconnection between them of all heat pipe branches leading to said node, said piece junction having tubular connecting branches, in number equal to the heat pipe branches interconnecting said node, each with an internal and substantially annular capillary structure surrounding a central channel, each connecting leg connecting to the other connecting branches by a longitudinal end, said internal end, and a branch of respective heat pipe by its opposite longitudinal end, said outer end, so that the capillary structure of each junction branch is in capillary continuity, at its outer end, with the capillary structure of said corresponding heat pipe, and is in capillary continuity, at its inner end, with the capillary structure of each of the other junction branches, and so that its central channel is in communication, at its outer end, with the central channel of the corresponding heat pipe branch, and at its inner end , with the central channel of each of the other junction branches.

In addition, in this case and when the capillary structure of the heat pipes consists of grooves, it is advantageous for this capillary structure of the heat pipes to be arranged in capillary continuity with the capillary structure of the junction branches of the braces consisting of a porous structure or a porous material, which has a high permeability, with a pore diameter of the porous structure or material which is not more than twice the opening of said grooves, to facilitate the flow of the liquid. This value can change depending on the fluid wettability characteristics of the different materials used.

In the same way, in the case of heat pipes whose capillary structure is constituted by a porous structure or a porous material, it is advantageous for this capillary structure of the heat pipes to be arranged in capillary continuity with the capillary structure of the connecting branches. braces, also consisting of a porous structure or a porous material, which has a high permeability with a pore diameter which is not greater than the pore diameter of the porous structure or the porous material of the heat pipes. This value can also change depending on the wettability characteristics of the fluid on the different materials used.

An appreciable advantage of this particular embodiment of the bridging device is that the heat pipe network may consist of standard heat pipe already commercially available, either grooved profile or porous capillary structure.

In a standard embodiment, the pipes of the heat pipes of the network are simply welded to the tubes of the cross or braces.

Another advantage is that any spider may be arranged to connect any number of heat pipe branches, generally 2 to 8 heat pipe branches, in a two or three dimensional array.

One of the advantages provided by any embodiment of the device according to the invention, when one or more hot sources is or are in thermal contact with the network, is that a heat exchange can be between each hot source and one or more elements. network (branches or nodes of the network). The network then makes it possible to efficiently collect all the heat produced by the hot source or sources and to homogenize the temperature of the assembly.

In exemplary devices according to the invention, the heat pipe network collects the heat generated by at least one hot source in thermal contact with at least a part of the network, and discharges said heat through at least one cold source in thermal contact with at least one other part of the network.

The hot springs may be either "point", dissipative element type or heater, or continuous type structure heated by at least one external source. Similarly, the cold sources may be punctual, cold finger type of refrigerant element, or continuous type radiative structure cooled by at least one external source.

Thus, the device makes it possible, by heat exchanges due to the changes in states of the two-phase fluid, to efficiently collect heat released by one or more hot sources by evaporation of the fluid, and the transfer through the network to one or more cold sources where the fluid condenses to return by capillarity to the hot source or sources.

Such a device can be used indifferently to cool one or more hot springs, and / or to heat one or more cold sources. The fluid used will be adapted to the operating temperatures of the system. For example, ammonia can be used for operating temperatures between -40 ° C and + 100 ° C.

Advantageously, said at least one heat pipe network of the device can be integrated at least partly in the mass of a structure, whose temperature is to be controlled.

According to another advantageous embodiment of the device, a part of said at least one heat pipe network is in thermal contact with at least one hot source, respectively cold, and another part of said network is in thermal contact with at least one cold source, respectively hot .

In a preferred embodiment, the device, in any of the embodiments presented above, further comprises at least one fluid loop, preferably two-phase, with capillary pumping, for transporting heat of said at least one heat pipe network to at least one remote heat sink, the evaporation zone of the fluid loop being in thermal contact with at least a part of the heat pipe network. In this case, at least one condensation zone of said fluid loop is in thermal contact with said at least one cold source.

In an inverted embodiment, the device comprises at least one fluid loop, preferably two-phase with capillary pumping, for transporting heat from at least one hot source remote to said at least one heat pipe network, the condensation zone of the fluid loop being in thermal contact with at least a portion of said heat pipe network. In this case, at least one evaporation zone of said loop is in thermal contact with said at least one hot source.

These two achievements benefit from the performance of fluid loops, which are known to be much more efficient than heat pipes of equal mass, for transporting a large heat flux from one point to another.

The device of the invention may also be such that said at least one heat pipe network is an integral part of a supporting structure to which is attached at least one hot source and / or at least one cold source.

In this case, said carrier structure may be advantageously constituted by said at least one heat pipe network itself, capable of supporting dissipative equipment, which limits the mass of the assembly. The function of the network of heat pipes is then double: thermal, with the transport, the homogenization of the heat, and mechanical, with the support / maintenance of dissipative equipments.

The device of the invention can be applied to a thermal control system making it possible to control the temperature of said at least one network, or at least one element in thermal contact with said network. This is achieved by arranging the device so that it further comprises at least one temperature sensor disposed on said at least one heat pipe network or in the vicinity of at least one element in thermal contact with said at least one network, and at least one heating member, respectively cooling, in thermal contact with said at least one network, so that the temperature of said at least one network or of said at least one element is controlled by applying a thermal power setpoint to be produced by said at least one a heating member, respectively cooling, as a function of differences noted between the temperature measurements provided by said at least one temperature sensor and a temperature setpoint.

The element or elements in thermal contact with the network may or may be one or more point sources such as equipment, or a carrier structure of equipment in which the network is integrated, or a mechanical part in which the network is integrated. In all these cases of application, the advantage of the heat pipe network according to the invention is to effectively homogenize the temperature although the one or more heating or cooling organs act punctually on the network, the diffusion of heat to the whole elements, the supporting structure or the mechanical part being done very efficiently via the network.

To prevent the consequences of a failure of said at least one network of interconnected heat pipes, for example a leak in this network, it is possible to ensure a redundancy of this network by superimposing at least two networks, possibly identical, or by subdividing said network into several non-interconnected sub-networks, but advantageously keeping thermal contact between said sub-networks.

The device of the invention can be the subject of many advantageous applications, a first relates to the cooling of an active antenna comprising radio-frequency (RF) tiles, whose dimensional characteristics are similar and the power dissipation characteristics possibly different, and which are arranged, preferably regularly, on a carrier structure in the form of grid, characterized in that at least one heat pipe network of said device is integrated in said carrier structure of the active antenna, and the heat collected by said network is discharged to at least one radiator by at least one extension of said network of heat pipes and / or at least one other heat pipe network and / or at least one fluid loop of said device.

A second advantageous application relates to the cooling of a carrier wall of electronic equipment, and is characterized in that at least one heat pipe network of said device is fixed on at least one thermally conductive skin of the wall, and preferably between two heat-conducting skins of said wall, and the heat collected by said at least one heat pipe network is discharged to at least one cold source, such as a radiator, by at least one extension of said heat pipe network and / or at least one other network of heat pipes and / or at least one fluid loop of said device.

A third particularly advantageous application relates to the thermal control of a mechanical part and is characterized in that at least one heat pipe network of said device is in heat exchange relationship with said mechanical part or integrated into said part, which we want to control the temperature, at least one heating element and at least one heat sink connected to at least one cooling element being placed in thermal contact with said heat pipe network for supplying or withdrawing heat from said network, and at least one temperature sensor measuring a variable physical quantity, representative of the temperature of said part, and whose measurement is compared to at least one reference value for controlling a change in the amount of heat to be supplied to or withdrawing from said workpiece so as to reduce the difference resulting from said comparison.

Depending on the shape and dimensions of the mechanical part, it will be advantageous to use a two-dimensional or three-dimensional heat pipe network. The two-dimensional network may be completely planar, or have curvatures in certain places in order to marry the shape of the room.

This latter application can advantageously be used to provide thermal control of a large optical instrument focal plane.

• La figure la est une vue en coupe longitudinale ou diamétrale d'un caloduc capillaire à rainures de l'état de la technique.
• La figure 1b est une coupe transversale du caloduc capillaire de la figure 1a,
• La figure 1c est une coupe transversale, analogue à la figure 1b, d'un caloduc capillaire à structure poreuse ou matériau poreux de l'état de la technique,
• La figure 2 est une vue schématique en coupe par un plan médian, d'un caloduc à co-courant en réseau de simples tubes capillaires interconnectés et en boucles fermées, selon l'état de la technique connu par US 6, 269, 865 ,
• La figure 3 est une vue partielle en perspective d'un réseau à deux dimensions de caloducs capillaires à rainures entrecroisées de l'état de la technique, ces figures 1a à 3 étant déjà décrites ci-dessus,
• La figure 4a est une vue schématique d'un réseau bidimensionnel de caloducs capillaires entrecroisés et interconnectés selon l'invention, en coupe par un plan axial des caloducs,
• La figure 4b est une vue, à plus grande échelle et également en coupe par un plan axial des caloducs, d'un noeud du réseau de la figure 4a auquel se raccordent quatre branches de caloducs,
• La figure 5 est une vue partielle en perspective éclatée de deux tronçons de caloducs capillaires à découpes complémentaires s'imbriquant l'un dans l'autre pour constituer une première variante de noeud d'un réseau bidimensionnel analogue à celui de la figure 4a,
• La figure 6a est une vue schématique, en coupe par un plan axial des caloducs, d'une deuxième variante de noeud d'un réseau bidimensionnel tel que celui de la figure 4a, avec une pièce de jonction en croisillon à quatre branches pour raccorder quatre branches de caloducs entre elles,
• La figure 6b est une vue en perspective du croisillon à quatre branches du noeud de la figure 6a,
• La figure 6c est une vue en perspective d'un croisillon à 6 branches constituant la pièce de jonction au niveau d'un noeud d'un réseau tridimensionnel, pour raccorder 6 branches de caloducs de ce réseau,
• La figure 7 est une vue schématique en perspective d'une application d'un dispositif selon l'invention, dont un réseau de caloducs capillaires interconnectés coopère avec une boucle fluide diphasique à pompage capillaire pour transférer de la chaleur de sources chaudes à un radiateur, et
• La figure 8 est une vue schématique partielle en coupe transversale d'une autre application d'un dispositif selon l'invention, dont un réseau de caloducs est mis en oeuvre dans une structure porteuse d'une antenne active, comportant des tuiles radiofréquence (RF) à refroidir.

Other characteristics and advantages of the invention will emerge from the description given below, by way of non-limiting example, of embodiments described with reference to the appended drawings, in which:

• Figure la is a longitudinal or diametral sectional view of a grooved capillary heat pipe of the state of the art.
• The figure 1b is a cross-section of the capillary heat pipe of the figure 1a ,
• The figure 1c is a cross-section, similar to the figure 1b , a capillary heat pipe with porous structure or porous material of the state of the art,
• The figure 2 is a diagrammatic sectional view through a median plane of a co-current heat pipe network of simple interconnected capillary tubes and closed loops, according to the state of the art known by US 6, 269, 865 ,
• The figure 3 is a partial perspective view of a two-dimensional network of capillary heat pipes with intersecting grooves of the state of the art, these Figures 1a to 3 already being described above,
• The figure 4a is a diagrammatic view of a two-dimensional network of intersecting and interconnected capillary heat pipes according to the invention, in section through an axial plane of the heat pipes,
• The figure 4b is a view, on a larger scale and also in section through an axial plane of the heat pipes, of a node of the network of the figure 4a to which are connected four branches of heat pipes,
• The figure 5 is a fragmentary perspective exploded view of two sections of capillary heat pipes with complementary cuts interlocking into one another to form a first node variant of a two-dimensional network similar to that of the figure 4a ,
• The figure 6a is a diagrammatic view, in section through an axial plane of the heat pipes, of a second variant of a node of a two-dimensional network such as that of the figure 4a , with a four-branched cross-brace joining four heat pipe branches together,
• The figure 6b is a perspective view of the four-branched cross of the node of the figure 6a ,
• The Figure 6c is a perspective view of a 6-branch brace constituting the joining piece at a node of a three-dimensional network, for connecting 6 branches of heat pipes of this network,
• The figure 7 is a schematic perspective view of an application of a device according to the invention, a network of interconnected capillary heat pipes cooperating with a capillary pump two-phase fluid loop for transferring heat from hot sources to a radiator, and
• The figure 8 is a partial schematic cross-sectional view of another application of a device according to the invention, a heat pipe network of which is used in a structure carrying an active antenna, comprising radiofrequency (RF) tiles to be cooled. .

The network 30, two-dimensional and generally flat, of the figure 4a comprises two groups of straight, parallel, regularly spaced capillary heat pipes, oriented for each group in one of two directions which are perpendicular to each other respectively. More specifically in this example, the first group comprises four heat pipes 31a, 31b, 31c and 31d, called "horizontal" on the figure 4a , crossed with the five heat pipes 31e, 31f, 31g, 31h and 31i called "vertical" of the second group, so that the heat pipes of each group are interconnected with the heat pipes of the other group at all the points of their intersections or connections, inside and on the edges of a rectangle delimited by the heat pipes horizontal upper 31a and lower 31d of the first group, and the vertical and lateral heat pipes 31e and 31i of the second group.

These connection points constitute as many nodes of the network 30. The number of heat pipe branches connecting to a node of the network can vary. For example, the network 30 considered here comprises four nodes of heat pipe such that the node 36 shown in enlarged view on the figure 4b , where are connected two successive branches 31b1 and 31b2 of a horizontal heat pipe such as 31b and the two successive branches 31f1 and 31f2 of a vertical heat pipe such as 31f.

The network 30 also comprises nodes with 3 branches such as the node 37, where are connected an end branch (the first or the last) such as 31b1 of a horizontal heat pipe such as 31b or vertical, inside the rectangle of the network 30, and two successive branches such as 31e1 and 31e2 of a vertical or horizontal heat pipe of an edge of the network, such as 31e '.

The network 30 further comprises two-branched nodes such as the node 38 situated at a "corner" of the rectangular network 30, where an end branch 31a1 of a heat pipe of a horizontal edge 31a, with an end branch such as 31e1 of a vertical edge such as 31e of the network.

The heat pipes and / or branches of capillary heat pipes are of a type known from the state of the art and as described above with reference to Figures 1a to 1c , that is to say comprise a tube 32 enveloping a capillary structure for the circulation of the liquid phase two-phase heat transfer fluid, which surrounds a central channel 34 for the circulation of this fluid in the vapor phase, the capillary structure being constituted by grooves longitudinally formed in the inner face of the wall of the tube 32 or a porous annular structure 35, optionally of a porous material, as shown in FIG. figure 4a , and, on a larger scale, on the four-branched node 36 of the figure 4b .

At each of the nodes 36, 37 and 38 of the network 30, all the branches which are interconnected at this node are connected to each other so as to ensure continuity of flow of the central channel 34 of any one of these branches. channel 34 of each of the other branches of this node, in such a way that fluid in the vapor phase flowing to the node through the channel 34 of any heat pipe branch leading to this node can flow into the central channels 34 of all the other branches of heat pipes connected to this node, as shown schematically by the six double arrows F on the figure 4b .

For a heat transfer is favorably effected by free circulation of the two-phase vapor phase heat transfer fluid between the central channels 34 of all the heat pipe branches connected to the same node, these central channels 34, have a passage section, or at least a typical dimension of the channel 34, for example its diameter, which remains substantially constant and equal from one channel 34 to the other, and, where appropriate, in any conduit flow connecting the channels 34 of all heat pipe branches at the same node. Thus, the continuity of flow of steam in all directions between the different heat pipe branches leading to the same node and through this node allows this steam to flow by inertia, without the need for have perfect continuity between the central channels 34, but ensuring only the absence of significant loss of load at each node.

Simultaneously, a capillary continuity for the fluid in the liquid phase is ensured between the capillary structures such as all the branches of heat pipes connected to the same node 36 or 37 or 38, so that a liquid phase fluid exchange can occur. by capillary action between these capillary structures 35, in such a way that fluid in the liquid phase flowing to a node in the capillary structure 35 of any one of the heat pipe branches connected to this node can flow by capillarity in the capillary structures 35 of all other heat pipe branches connected to this node. For this purpose, the capillary structure 35 of each heat pipe branch leading to a knot is, as far as possible, abutted by its inner end (turned towards the center of the knot) against internal ends of the capillary structures 35 of adjacent heat pipe branches connected to the same node. If these capillary structures are porous structures or porous material such as on the figure 4b a satisfactory capillary continuity is ensured if there is no discontinuity between the porous structures 35 which exceeds the typical dimension of a pore of this structure 35 or of the porous material which constitutes it. In the case where the capillary structure of the heat pipe branches consists of grooves, as presented above, the discontinuity between the capillary structures of the heat pipe branches resulting in the same node should not exceed the typical dimension of a groove. of these structures, at the center of the node, where the inner ends of these structures are as much as possible in contact with each other, and so that grooves of a capillary structure are in at least partial communication with grooves capillary structures of adjacent heat pipe branches at this node.

Thus, irrespective of the nature (grooves or porous structure or porous material) of the capillary structure of the heat pipe branches, the fluid in the liquid phase can flow by capillarity in the zone situated in the center of the node, whose geometry is such that that the effects of surface tension are predominant on the effects of gravity or inertia. The capillary continuity for the fluid in the liquid phase is thus ensured in all directions between the different heat pipe branches. leading to the nodes and through the nodes 36, 37 and 38.

In order to accommodate the expansion-contractions of the fluid, by adapting the amount of fluid in the liquid phase present in the network 30 to the temperature variations of this network 30, a reservoir 39 of fluid is connected to the network 30. On the figure 4a , the reservoir 39 is connected to the network 30 by a branch 31g4 of the heat pipe 31g, which extends the latter towards the outside of the network 30. This reservoir 39 has its internal face lined with a capillary coating 40, which is in capillary continuity with the capillary structure of the connecting branch 31g4 of the reservoir 39 to the network 30. This capillary continuity between the internal capillary lining 40 of the reservoir 39 and the capillary structure of the branch 31g4 is ensured in the same manner as described above at the level of nodes of the network, and therefore also between the capillary structure of the link branch 31g4 and the branches of the heat pipes 31d and 31g to which the link branch 31g4 is connected to a node of the network 30, as shown in FIG. figure 4a . Thus, fluid in the liquid phase can circulate, in both directions, between the reservoir 39 and the network 30, by capillary flow in the capillary seal 40 of the reservoir 39 and the capillary structures 35 of the branch 31g4 and the other heat pipe branches of the network 30, and simultaneously fluid in the vapor phase can also flow, in both directions, between the central volume of the reservoir 39 and the central channels 34 of the branch 31g4 and other branches of In this example, the diameter or the passage section of the central channel 34 of the connecting branch 31g4 is smaller than the diameter or the passage section of the central channels 34 of the other heat pipe branches of the network 30, and / or the radial thickness of the capillary structure 35 of the connecting branch 31g4 is less than the thickness of the capillary structure 35 of the other heat pipe branches of the network 30.

Preferably, the grooved nature (in the direction of the longitudinal axis of the branch 31g4) or the porous nature of the internal capillary lining 40 of the reservoir 39 is the same as that of the capillary structure of the connecting branch 31g4, itself of the same nature as that of the capillary structures of the other heat pipe branches of the network 30, but this is not an absolute necessity. Advantageously, this capillary seal 40 is made in the form of a porous structure or a porous material.

If necessary, to support higher or lower flux densities, or to integrate the network 30, or portions or extensions thereof in specific volumes and / or having specific geometries, including congestion, or in the case where at least a part of the network must operate under specific conditions, for example against gravity, one or more of the heat pipes 31 of the network 30 may each comprise one or more branches which is different from the other branches of the heat pipes 31 from the network 30 to the plane dimensionally at the level of the central channel 34 and / or the capillary structure 35, and / or in terms of the nature of the capillary structure 35, for example a porous structure made of different porous materials in different heat pipe branches of the network.

The figure 5 represents an embodiment of a 4-branch node, made by interconnecting two capillary heat pipes of rectangular cross-section of a network (not shown elsewhere) at their crisscrossing. The two heat pipes 41 are identical to each other and each consists of a tube 42, metal or plastic, whose inner wall is lined with a tubular capillary structure 43, in this example a porous structure or a porous material of substantially constant thickness, surrounding a central channel 44, the tube 42, the capillary structure 43 and the channel 44 having a rectangular cross section.

To form an interconnection node of the two heat pipes 41, a cutout 45 is made in each of them, so as to form a recessed area 46 of intersection and interconnection. This cutout 45 extends through the tube 42 and the capillary structure 43, over an axial length (along the axis of the heat pipe 41) equal to the width of the large faces of the heat pipes 41, and between two straight sections of the heat pipe 41 ( perpendicular to the axis of the heat pipe 41) in each of which the cutout 45 extends over a half-perimeter of the heat pipe 41, through a large face (for example the large horizontal face and upper) of the heat pipe 41, and on the half height of the two vertical sides of the heat pipe 41.

Then a heat pipe 41a, belonging to a first group of heat pipes (not shown) parallel and spaced apart, is returned, so that its intersection zone 46 is turned down, and nested by this zone 46 in the zone d recessed intersection 46 of the other heat pipe 41b, whose longitudinal axis is oriented perpendicular to that of the heat pipe 41a, and which belongs to a second group of heat pipes (also not shown) parallel and spaced apart.

Thus, the central channels 44 of the two heat pipes 41a and 41b are reconstituted by being interconnected, as well as the capillary structures 43, brought into contact along the cuts 45 so as to reconstitute a capillary continuity. The two tubes 42 nested one inside the other at the cutouts 45 of complementary shapes are then welded to each other along the cutouts 45, in order to restore the tightness of the tubes 42 and to secure them together. along the cutouts 45. Thus, at the same time, continuity of flow of the fluid in the vapor phase along the central channels 44 and continuity of the capillary flow of the fluid in the liquid phase along the capillary structures 43 of the heat pipes 41 are ensured.

The same type of intersection and interconnection can be achieved with tube heat pipes, capillary structure and cylindrical central channel of circular section, or of square section, to achieve a two-dimensional network. The external connection of the tubes of two heat pipes at their intersection and interconnection must be ensured so that the fluid can not escape at this point, which is why the two tubes must be secured to each other. sealing way along the cuts, which can be obtained not only by welding, as already described above, but also by gluing, for example. It is also understood that the capillary continuity which must be ensured between the capillary structures of two interconnected heat pipes may be more easily obtained if this capillary structure is a porous structure, for example formed of a porous material, rather than consisting of grooves.

It is clear that the embodiment of a network node according to the figure 5 It is more difficult to use a heat pipe with a grooved capillary structure and / or arranged in a three-dimensional network.

A second embodiment of a four branch heat pipe node is now described with reference to the figure 6a , for an application to the realization of a two-dimensional network similar to that of the figure 4a .

This second embodiment is much more advantageous than that described above with reference to the figure 5 because it makes it possible to overcome the aforementioned limitations of the latter, and therefore, in particular, to easily make networks not only two-dimensional but also three-dimensional, and / or to use heat pipes of the state of the technical, whose capillary structure can be both grooved and porous. In addition, the heat pipes used may have cross sections whose shapes are not necessarily limited to circular, rectangular or square shapes.

According to this second embodiment, the interconnection of all the different branches of heat pipes 51 leading to the same node of the network is made in a modular manner, via a connecting piece 55 or connector, also called cross in the example of figure 6a a node where are connected four heat pipe branches 51, two of which are horizontal on the figure 6a , belong to a first group of heat pipes, and the other two, vertical on the figure 6a , and perpendicular to the first two, belong to a second group of heat pipes crisscrossed and interconnected with the heat pipes of the first group in a network similar to that of the figure 4a , and not further described or represented.

The joining piece 55 is hollow and has as many tubular junction branches 56 as the number of heat pipe branches 51 interconnected by this piece 55 at the corresponding node of the network.

Each junction branch 56 has the same general structure as the heat pipe branches 51, each of which comprises, as known, a rigid outer tube 52 enveloping an annular capillary structure 53 (for the circulation by capillarity of the fluid in the liquid phase) constituted preferably longitudinal grooves formed in the inner face of the tube 52 in the example of the figure 6a but may also be a porous structure or a porous material covering the inner wall of the tube 52, this capillary structure 53 itself surrounding a central channel 54 (for inertial circulation of the fluid in the vapor phase essentially).

More specifically, each connecting branch 56 comprises a rigid outer tube 57, by which this branch 56 is secured to the other branches 56 and in one piece with them forming the joining piece 55, this tube 57 having its inner wall covered an annular capillary structure 58 (for the capillary circulation of the fluid in the liquid phase) advantageously produced by a porous structure or a porous material, and itself surrounding a central channel 59 (essentially for circulation of the vapor phase fluid) .

As shown on the figure 6a each of the heat pipe branches 51 interconnected with each other at the corresponding node is held, by its end facing the junction piece or spider 55, against the so-called outer end, because turned on the opposite side to the center of the spider 55, of a junction branch 56 corresponding, so that the two branches 51 and 56 are maintained aligned and end to end, while the central channel 59 of each junction branch 56 is in communication, at the so-called internal end of the junction branch 56, c ' that is, its end facing the center of the spider 55, with the central channels 59 of all the other connecting branches 56 of the spider 55. Moreover, as at the outer end of each connecting branch 56 of the spider 55 , the central channel 59 of this junction branch 56 is in communication with the central channel 54 of the corresponding heat pipe branch 51, the flow continuity of the fluid in substantially vapor phase is ensured in all directions of the branches of heat pipes 51 and through the node by the permanent communication of the central channels 59 junction branches 56 between them and with the central channels 54 of the heat pipe branches 51. Simultaneously, the cross 55 provides a capillary continuity between the capillary structure 58 of each junction branch 56, at the outer end of the latter, with the capillary structure 53 of the corresponding heat pipe branch 51, while at the inner end of said junction branch 56, its capillary structure 58 is in capillary continuity with the similar capillary structure 58 of each of the other junction branches 56 of the spider 55.

The branches 56 of the spider 55 are dimensionally and geometrically adapted to the heat pipe branches 51 to which they are connected, in particular the branches 51 and 56 have substantially the same shape and cross-sectional area, and in particular substantially the same external diameter, thickness of the capillary structures 53 and 58, and diameter of the central channels 54 and 59.

In practice, the tubes 57 of the spider 55 may consist of the same material as the tubes 52 of the heat pipe branches 51, the latter being welded to the branches 56 of the spider 55, after possibly interlocking the ends of the heat pipe branches 51 in sleeves formed by extensions to the outside of the tube 57 of the branches 56 of the spider 55.

In the example of the figure 6a as the capillary structure 53 of the heat pipe branches 51 is constituted by grooves, while the capillary structure 58 of the connecting branches 56 of the spider 55 is a porous structure or of a porous material, so that this capillary structure 58 has a high permeability the porous structure or the porous material which constitutes it preferably has a pore diameter less than or equal to about twice the opening of the grooves of the capillary structure 53, in order to facilitate the flow of the fluid in the liquid phase. However, this value can change depending on the wettability characteristics of the coolant used on the different materials used.

On the other hand, in the case of heat pipe branches 51 whose capillary structure consists of a porous structure or of a porous material, it is then advantageous for the capillary structure 58 of the branches 56 of the spider 55 to have a high permeability having a pore diameter substantially less than or equal to the pore diameter of the porous structure or of the porous material constituting the capillary structure of the heat pipe branches 51, this value also being able to vary as a function of the wettability characteristics of the fluid on the various materials used.

The embodiment of the capillary structure 58 of the branches 56 of the spider 55 with the aid of a porous structure or of a porous material is advantageous in view of the complex shape of the spider 55, whereas, for simplicity of embodiment, the capillary structure 53 of the heat pipe branches 51 is often made by internal grooves extruded into the mass of the tubes 52. To produce this type of braces 55, several processes can be implemented, among which can be mentioned the methods based on the simple sintering, laser sintering or stereo-lithography.

The production of heat pipes 51 compatible with connecting pieces such as braces 55, or T-shaped or L-shaped fittings, the two or three connecting branches respectively have the same structure and cooperate in the same way with each other and with branches of heat pipes 51 that the branches 56 of the spider 55, when respectively three or two branches of heat pipes 51 are connected to the same node, does not pose any particular problem since the heat pipe 51 of the network may consist of standard heat pipes already marketed, whose capillary structure is either grooved profile or porous.

The figure 6b represents in perspective the cross 55 of the figure 6a in an embodiment in which the connecting legs 56 and their tube 57, capillary structure 58 and central channel 59 are cylindrical with a circular cross section.

The Figure 6c represents, in exploded perspective, a node with six branches of a three-dimensional network, made on the same principle of intersecting and interconnecting the heat pipes of three groups of straight, parallel and spaced apart heat pipes, oriented for each group according to the one respectively of three directions perpendicular two by two, the interconnection being ensured, at each node, by a hollow joining piece with tubular connecting branches which, on the Figure 6c , is a spider 65 with six junction branches 66. Compared to the braces 55 of the figure 6a , the 65 spider of the Figure 6c has the particularity of having two additional junction branches 66, symmetrical to each other with respect to the center of the spider 65, and coaxial about an axis perpendicular to the plane of the two perpendicular axes between them and around each of which two of the other four junction branches 66 are coaxial.

As in the example of Figures 6a and 6b each junction branch 66 is cylindrical tubular of circular section and consists of an outer tube 67 whose inner wall is covered with a porous capillary structure 58 itself surrounding a central channel 69, and the ends facing the six limbs of heat pipes 61 which are connected to the braces 65 are also, as in the example of the Figures 6a and 6b , consisting of a rigid outer tube 62, whose inner wall is axially grooved to form its capillary structure 63 around a central channel 64.

Another advantage of this type of device is that a spider can be adapted to connect any number of heat pipe branches, typically from two to eight, in two- or three-dimensional networks.

As shown on the left side only of the figure 7 in a thermal control device according to the invention, a network, bi or three-dimensional, as described above, for example, the two-dimensional network 70 of interconnected heat pipes 71 of the figure 7 , similar to the network 30 of the figure 4a , can be put directly in heat exchange relation with one or more hot sources such as 72a, 72b and 72c, so that a heat exchange is established between each hot source 72a, 72b, 72c, and one or more elements of the network 70, such as branches of heat pipes 71, nodes or even meshes of the network 70, each mesh consisting of four branches of heat pipes 71 connected in pairs by four nodes so as to form a closed loop in the network 70 (on the figure 7 each hot source 72a to 72c is schematically shown as covering a mesh respectively of the network 70, and is therefore in thermal contact with the four branches of heat pipes 71 and the four nodes of this mesh). The network 70 can thus efficiently collect the heat produced by one, several, or all the hot sources 72a to 72c and homogenize the temperature of the assembly.

One or more of the hot springs 72a to 72c may or may be of a so-called "point" nature, in particular heat dissipating elements such as equipment, components or electronic circuits fixed directly on the heat pipe network or possibly on a load-bearing wall, the sources each being in thermal contact with a portion of the network 70, at different points of this network, either directly or via an intermediate piece providing thermal conduction between the network and the hot springs.

As a variant, one or more of the hot springs 72a to 72c may or may be of a "continuous" nature, and consist for example of structure (s) it (s) itself (s) heated by external sources and in thermal contact with part of the network 70.

According to another variant, in the two preceding cases and assuming that only the sources 72a and 72b are hot springs, another part of the network 70 is in direct heat exchange relation with a cold source, such as 72c, which can -being of a "one-off" nature, such as a cold finger of a refrigerating element for example, or of a "continuous" nature, such as a radiator cooled by an external source, to which the radiator transmits heat that he receives from the network 70.

In a general way, this other variant consists in putting the whole network 70 of heat pipes 71 in thermal contact with one or hot springs, respectively cold, except at least one branch of heat pipes 71 and / or at least one node of the network, which is or is in thermal contact with at least one cold source, respectively hot.

Thus, the device makes it possible, by the liquid / vapor phase and vapor / liquid phase changes of the two-phase heat transfer fluid circulating in the network 70, to efficiently collect heat diffused by one or more hot sources (s) such ( s) that 72a and 72b, by evaporation of the fluid, and transfer it through the network 70 to a source (s) cold (s), such (s) 72c, where the fluid condenses to return by capillarity to the hot source (s).

Such a thermal regulation device can therefore be used, passively and indifferently, to cool one or more hot source (s) (such as 72a e 72b) and / or to heat one or more source (s) cold (s) (such that 72c), the coolant used being adapted to the operating temperatures of the device, for example ammonia for operating temperatures between -40 ° C and + 100 ° C.

However, in a preferred embodiment, the device further comprises at least one fluid loop, for example, a capillary pumping loop of a two-phase heat transfer fluid, which is advantageously the same as that of the network 70 of heat pipes 71, for transporting the heat of the network 71 to at least one cold source, or conversely of at least one hot source to the network 70, because such fluid loops are known to be much more efficient than the heat pipes (with equal mass), to transport a significant heat flow from one point to another.

As represented by the whole of the figure 7 in the case of cooling at least one of hot springs 72a, 72b and 72c, placed in contact with the network 72 of heat pipes 71, the evaporation zone 74 of a fluid loop 73 is placed in thermal contact with the network 70, in this example at a node where three branches of heat pipes 71 are interconnected on an edge of the network 70, and the condensation zone 74 of the fluid loop 73 is placed in thermal contact with at least one cold source 76 in this example, an external radiator, the hot sources may be heat dissipating equipment, possibly attached to a load-bearing wall, the cold source 76 (the radiator) being optionally remote and remote network 70 and hot springs 72a to 72c . Thus, the heat transmitted by the hot springs 72a to 72c to the network 70 is transferred to the evaporation zone 74 to the fluid of the fluid loop 73, which is vaporized at this point and flows in the vapor phase to the zone of condensation 75, where this heat is transferred by condensation of the fluid of the loop 73 to the radiator 76 which dissipates it in the heat sink constituted by the surrounding space.

Such a device can be used in an inverted mode for heating at least one cold source 72a to 72c in thermal contact with the network 70. In this case, the evaporation zone 75 of the fluid loop 73 is brought into contact thermal with a hot source 76, external to the network 70, and the condensation zone 74 of the fluid loop 73 is placed in thermal contact with the network 70.

In the application of the thermal regulation device of the figure 7 , without or with at least one fluid loop 73, to the cooling of the electronic equipment of an equipment bearing wall, as already mentioned above, the The network 70 of heat pipes 71 of the device can be fixed on a thermally conductive skin (not shown), for example metal or composite material, and preferably between two skins of this type. The heat collected by the network 70 is evacuated either by an extension of the network 70, or via at least one fluid loop such as 73, to one or more cold source (s) such (s) one or radiator (s) 76.

In other applications of the thermal control device according to the invention, at least a part of a two or three-dimensional network of heat pipes, depending on the application can be advantageously integrated into the mass of a structure, whose temperature must eventually to be actively controlled. This structure may be a carrier structure on which at least one hot source and / or at least one cold source is or are fixed (s).

Such an application for cooling an active radiofrequency tile antenna is described with reference to the figure 8 . On this figure 8 , the network 80 of heat pipes 81 is represented only by two heat pipes 81 parallel and oriented in one of the two directions of this two-dimensional network 80. Each heat pipe 81 comprises a flat sole, made of a good heat-conducting material, in one piece with a hemicylindrical central portion through which the tube 82 of the heat pipe 81 passes, the internal wall of which presents the grooves of its capillary structure 83 around the central channel 84 corresponding. By the sides of this sole, each heat pipe 81 is suspended in a channel 86 formed in a rib 87, oriented in the same direction as the heat pipes 81, a carrier structure 88 in the form of grid, which has ribs similar to the ribs 87 but perpendicular to the latter, and also provided with gutters such as 86, for housing the heat pipe network 80 which are perpendicular to the heat pipes 81. The carrying structure 88 supports radiofrequency tiles (RF) 85 thinned edges to rest on the ribs such as 87, being arranged next to each other to define a surface of the active antenna. These RF tiles 85 have similar dimensional characteristics and are arranged in a matrix, but the thermal powers they dissipate are possibly different from each other. The tiles 85 thus arranged regularly on the carrying structure 88 transmit heat to the soles of the heat pipes 81 on which the tiles 85 rest, and this heat is then transmitted from the heat pipes 81 of the network 80 to an evaporator 89, integrated into the base. at least one rib 87, and therefore in the carrier structure 88, and belonging to a fluid loop whose condenser is in thermal contact with at least one cold source such as an external radiator remote from the active antenna.

In a variant, the heat collected by the network 80 of heat pipes 81 integrated in the carrying structure 88 is effectively evacuated to one or more radiators by an extension of this network 80.

In some applications, the structure carrying at least one hot source and / or at least one cold source may advantageously be constituted by a network of heat pipes itself of the device. The mass of the entire device is thus limited, in which the function of said heat pipe network is twofold and comprises a thermal transport / homogenization function of the heat, and a mechanical function for supporting / maintaining the dissipative equipment constituting the one or more hot or cold source (s).

The thermal regulation device of the invention can also be applied to the production of a device for controlling the temperature of at least one heat pipe network of the device and / or at least one hot source and / or at least one cold source and / or at least one part and / or at least one set with respectively which and / or which at least one heat pipe network of the device is in heat exchange relation, or even in which and / or which said at least one heat pipe network of the device is integrated at least partially. In this case, at least one temperature sensor and / or at least one cooling element and / or at least one heating element are placed in heat exchange relation with said network, at different locations of the latter, and at least one setpoint of thermal power to be transferred by said at least one cooling element and / or said at least one heating element is applied to this or these cooler (s) or heating element (s) as a function of at least one temperature difference observed between at least one temperature setpoint and at least one temperature measurement provided by at least said one temperature sensor. In this application framework, mention is made, by way of example, of the thermal control of a mechanical part, the temperature of which is to be controlled, and with which a two or three-dimensional heat pipe network of a device according to the invention is in intimate thermal contact, or of which said heat pipe network is part. As a result, the thermal properties of the heat pipe network enable the latter to quickly uniformize the temperature within the mechanical part. In addition, at least one heating element and / or at least one heat sink connected to at least one cooling element, and placed in thermal contact with said network can or can respectively bring or remove heat to said network, by increasing or thus lowering the temperature of the mechanical part respectively. In addition, at least one temperature sensor is implanted in the device so as to measure a variable representative of the temperature of the room, and can therefore be used to actively control the temperature of this mechanical part, by comparing the measurement of said at least one a temperature sensor to at least one reference value, and varying the amount of heat supplied to or removed from the part, as a function of the difference resulting from the comparison between said measurement and said reference value in order to reduce said difference.

As an example of application, this type of temperature control device and temperature control of a mechanical part can be advantageously used to provide thermal control of a large focal plane optical instrument.

In the different embodiments and applications of the device of the invention, the damaging consequences of a failure of an interconnected heat pipe network, for example a heat transfer fluid leak out of said network, may be limited, or even completely compensated, if the device is arranged to be redundant, for example by having at least two non-interconnected networks, preferably identical but not necessarily, or by subdividing the network into several non-interconnected subnetworks, but advantageously maintaining said at least two networks or subnets in heat exchange relationship with each other.

Claims (22)

1. A thermal control device, comprising at least one network (30) of capillary heat pipes (31), in which each heat pipe (31) comprises a tube (32) enclosing a longitudinal and substantially annular capillary structure (35), for the circulation of a two-phase heat transfer fluid in the liquid phase, and surrounding a central channel (34) for the circulation of said two-phase fluid in the vapor phase, characterized in that the tubes (32) of at least two heat pipes (31) of the network (30) intersect and are interconnected in such a way that at each intersection of heat pipes (31) forming a node (36, 37, 38) of the network (30), an exchange of fluid in the liquid phase can take place by capillary action between the capillary structures (35) of said at least two heat pipes (31), and such that, simultaneously, an exchange of fluid in the vapor phase can take place by free circulation between the central channels (34) of said at least two heat pipes (31).
2. A device according to claim 1, characterized in that, at each node (36, 37, 38) of the network (30), the capillary structures (35) of all heat pipe (31) branches ending at said node (36, 37, 38) provide capillary continuity for the fluid in the liquid phase, such that the fluid in the liquid phase arriving at said node (36, 37, 38) in any heat pipe (31) branch ending at said node can flow by capillary action into all the other heat pipe (31) branches ending at said node (36, 37, 38).
3. A device according to claim 2, characterized in that, at each node (36, 37, 38) of the network (30), the capillary structures (35) of the heat pipe (31) branches ending at said node (36, 37, 38) have no discontinuity between them of a size greater than the typical dimension of a pore or groove of the capillary structure (35) of the heat pipes (31), depending on whether said structure (35) respectively consists of porous material or of internal grooves in the corresponding tube (32).
4. A device according to any one of claims 1 to 3, characterized in that, at each node (36, 37, 38) of the network (30), the central channels (34) of all the heat pipe (31) branches ending at said node (36, 37, 38) assure simultaneously with flow continuity for the fluid in the liquid phase, the flow continuity for the fluid in the vapor phase, such that the fluid arriving at said node (36, 37, 38) in the vapor phase via any heat pipe (31) branch ending at said node (36, 37, 38) can flow into all the other heat pipe (31) branches ending at said node (36, 37, 38).
5. A device according to claim 4, characterized in that, at each node (36, 37, 38) of the network (30), the flow continuity of the fluid in the vapor phase is assured between the central channels (34) of the heat pipe (31) branches ending at said node (36, 37, 38), by a flow conduit having a flow area or at least one typical dimension that is substantially equal to the flow area or to at least one typical dimension of the central channels (34) of said heat pipe (31) branches ending at said node (36, 37, 38).
6. A device according to any one of claims 1 to 4, characterized in that at least one heat pipe (31 g) of the network (30) comprises at least one branch (31 g4) which differs from the branches of at least one other heat pipe (31) of the network (30), in its capillary structure (35) and/or in at least one typical dimension of said heat pipe (31 g) branch (31 g4).
7. A device according to any one of claims 1 to 6, characterized in that said at least one network (30) of heat pipes (31) is a two-dimensional network, comprising two pluralities of heat pipes (31 a - 31 d; 31 e - 31 i) such that the heat pipes of each plurality are substantially oriented, along at least a portion of their length, in one of two respective directions sloped relative to one another and preferably perpendicular to each other, such that the heat pipes (31a - 31 d; 31e - 31i) of the two pluralities intersect and are interconnected at their intersection.
8. A device according to any one of claims 1 to 6, characterized in that said at least one network of heat pipes (61) is a three-dimensional network, comprising, in at least one node (65) of the network, at least three heat pipe (61) branches oriented for at least a portion of their length in one of three respective directions, each direction sloped relative to any one of the other two directions and preferably perpendicular to each other, with said at least three heat pipe (61) branches intersecting with each other and being interconnected.
9. A device according to any one of claims 1 to 7, characterized in that, in at least one node of the network, the at least two heat pipes (41) which intersect and are interconnected at said node have cutouts (45) of complementary shapes cut into their respective tube (42) and capillary structure (43) such that the heat pipes (41) fit together at the cutouts (45) and reestablish the continuity of the tube (42) walls, integrally attached all along the cutouts (45), the capillary continuity in the capillary structures (43), and the flow continuity along the channels (44) of said heat pipes (41).
10. A device according to any one of claims 1 to 9, characterized in that at least one node of the network comprises a hollow connecting piece (55, 65), referred to as a cross-piece, interconnecting all the heat pipe (51, 61) branches ending at said node, said connecting piece (55, 65) comprising tubular connecting arms (56, 66) of an equal number as the heat pipe (51, 61) branches which interconnect at said node, each with an internal and substantially annular capillary structure (58, 68) surrounding a central channel (59, 69), each connecting arm (56, 66) connecting to the other connecting arms (56, 66) by a longitudinal end, referred to as the inside end, and to a respective heat pipe (51, 61) branch by its longitudinally opposite end, referred to as the outside end, such that the capillary structure (58, 68) of each connecting arm (56, 66) has capillary continuity at its outside end with the capillary structure (53, 63) of said corresponding heat pipe (51, 61) branch, and has capillary continuity (58, 68) at its inside end with the capillary structure of each of the other connecting arms (56, 66), and such that its central channel (59, 69) communicates at its outside end with the central channel (54, 64) of said corresponding heat pipe (51, 61) branch, and at its inside end with the central channel (59, 69) of each of the other connecting arms (56, 66).
11. A device according to claim 10, characterized in that the capillary structure (53, 63) of the heat pipes (51, 61) is formed by grooves and has capillary continuity with the capillary structure (58, 68) of the connecting arms (56, 66) of the cross-pieces (55, 65), which consists of a porous structure or porous material, having a high permeability, with a pore diameter of the porous structure or material no greater than twice the aperture of said grooves.
12. A device according to claim 10, characterized in that the capillary structure of the heat pipes comprises a porous structure or a porous material and has capillary continuity with the capillary structure (58, 68) of the connecting arms (56, 66) of the cross-pieces (55, 65), also comprising a porous structure or a porous material, having a high permeability with a pore diameter no greater than the pore diameter of the porous structure or porous material of the heat pipes.
13. A device according to any one of claims 10 to 12, characterized in that a cross-piece (55, 65) is arranged to connect from two to eight heat pipe (51, 61) branches, in a two- or three-dimensional network.
14. A device according to any one of claims 1 to 13, characterized in that said at least one network (80) of heat pipes (81) is at least partially integrated into the mass of a structure (88) having a temperature that is to be controlled.
15. A device according to any one of claims 1 to 13, characterized in that a portion of said at least one network (70) of heat pipes (71) is in thermal contact with at least one heat source (72a, 72b) or cold source (72c), and another portion of said network (70) is in thermal contact with at least one respective cold source (72c) or heat source (72a, 72b).
16. A device according to any one of claims 1 to 15, characterized in that it additionally comprises at least one fluid loop (73), preferably two-phase and capillary pumped, for transporting heat from said at least one network (70) of heat pipes (71) to at least one distant cold source (76), the evaporation zone (74) of the fluid loop (73) being in thermal contact with at least a portion of the network (70) of heat pipes (71).
17. A device according to any one of claims 1 to 15, characterized in that it additionally comprises at least one fluid loop (73), preferably two-phase and capillary pumped, for transporting heat from at least one distant heat source to said at least one network (70) of heat pipes (71), the condensation zone (75) of the fluid loop (73) being in thermal contact with at least a portion of said network (70) of heat pipes (71).
18. A device according to any one of claims 1 to 17, characterized in that said at least one network (80) of heat pipes (81) is an integral part of a supporting structure (88) onto which at least one heat source (85) and/or at least one cold source is mounted.
19. A device according to claim 18, characterized in that said supporting structure is comprised of said at least one network of heat pipes, suitable for supporting heat dissipating equipment.
20. A device according to any one of claims 1 to 19, characterized in that it additionally comprises at least one temperature sensor placed on said at least one network of heat pipes or in the vicinity of at least one element in thermal contact with said at least one network, and at least one heating or cooling means in thermal contact with said at least one network, such that the temperature of said at least one network or said at least one element is controlled by applying a thermal power setpoint for the heating or cooling to be produced by said at least one respective heating or cooling means, based on the observed differences between the temperature measurements obtained by said at least one temperature sensor and a temperature setpoint.
21. The application of a thermal control device according to any one of claims 1 to 20, to cooling an active antenna comprising radiofrequency (RF) tiles (85), having similar dimensional characteristics and possibly different power dissipation characteristics, and which are arranged, preferably at regular intervals, on a supporting structure (88) in the form of a grid, characterized in that at least one network (80) of heat pipes (81) of said device is integrated into said supporting structure (88) of the active antenna, and the heat collected by said network (80) is drawn off to at least one radiator by at least one extension from said network (80) of heat pipes (81) and/or at least one other network of heat pipes and/or at least one fluid loop (89) of said device.
22. The application of a thermal control device according to any one of claims 1 to 20, to cooling a supporting wall for mounting electronic equipment (72a, 72b, 72c), characterized in that at least one network (70) of heat pipes (71) of said device is attached to at least one thermally conductive facesheet of the wall, and preferably between two thermally conductive facesheets of said wall, and the heat collected by said at least one network (70) of heat pipes (71) is drawn off to at least one cold source (76), such as a radiator, by at least one extension from said network of heat pipes and/or at least one other network (70) of heat pipes (71) and/or at least one fluid loop (73) of said device.

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