SIMPLIFIED HEAT TUBE AND PULSE TUBE

Description

TECHNICAL FIELD AND PRIOR TECHNOLOGY

[0001] The present invention relates to a two-phase heat transfer device that can be a thermosiphon or a pulsed heat pipe of simplified manufacture. A thermosiphon of conventional construction in the prior art is known from US 2016 / 381 / 839, and a pulsed heat pipe of standard construction is known from US 2007 / 144 / 574.

[0002] A two-phase thermosiphon is a heat transfer device that operates by the evaporation and condensation of a liquid introduced at its vapor pressure into a sealed chamber. It has one end called the "evaporator zone," which is in contact with a heat source, and the other end called the "condenser zone," which is in contact with a cold source. The fluid in the evaporator zone is heated and evaporates, extracting heat from the heat source. The vapor then travels to the condenser zone, where it condenses and releases heat to the cold source. The liquid then returns to the evaporator zone. The evaporator zone is located lower than the condenser zone, so the condensate returns to the evaporator zone by gravity.

[0003] A pulsed heat pipe is a heat transfer system that operates by the oscillation of vapor and liquid plugs in a fluid circuit that circulates successively between one or more hot zones and one or more cold zones. The cross-section of the fluid circuit is small to achieve a plug-like flow configuration. Heat transfer occurs through latent heat, but also through sensible heat thanks to the liquid plugs oscillating between the hot and cold zones.

[0004] Such heat transfer devices can be used in the field of electronics, for example power electronics to cool electronic components.

[0005] Such devices have the advantage of being able to operate efficiently against gravity, i.e. when the evaporator is positioned above the condenser.

[0006] US patent 8,919,426 describes a pulsed heat pipe comprising an upper and a lower plate, each plate having an impression of a coiled microchannel. When the two plates are joined, they form a sealed coiled microchannel. The impressions are made by chemical etching. Firstly, etching two plates can be time-consuming. Secondly, the depth of the etches must be carefully monitored. Finally, this etching method has a relatively high cost and is not well-suited to medium and large production runs. DESCRIPTION OF THE INVENTION

[0007] It is therefore an aim of the present invention to provide a heat transfer device such as a thermosiphon or a pulsed heat pipe of simplified realization.

[0008] The previously stated goal is achieved by a heat transfer device forming a thermosiphon or a pulsed heat pipe conforming to icacations 1 or 5 respectively.

[0009] The heat transfer device is therefore simple to manufacture. Indeed, since the grooves and cutouts in the intermediate plates are through-holes, their fabrication is simplified, unlike the creation of non-through-holes. They can be advantageously produced by punching, which is particularly well-suited to medium or large production runs.

[0010] In the case of aluminum alloy plates, they can be advantageously joined by brazing. The use of aluminum alloys allows for industrial brazing using eutectic alloys.

[0011] Thanks to this plate arrangement and the creation of through grooves to form the channels, the junction between the grooved intermediate plate and the other intermediate plate or one of the end plates forms angles rather than rounded shapes. These angles promote capillary action.

[0012] In other words, the functions are distributed per plate, which simplifies the structure of each plate and therefore simplifies their manufacture.

[0013] Indeed, the plate with the grooves delimits the side walls of the channels, the plate with the cutouts forms an end wall and ensures either the balancing of the load between the different channels in the case of a thermosiphon, or the series connection of the channels, and the end plates, one forming the other end wall of the channel and the other closing the cutouts.

[0014] In addition, this distribution of functions per plate makes it easier to change the manufactured device in the case of a single production line for thermosiphons and pulsed heat pipes, it is very easy to change the manufactured heat transfer device, in fact it is only necessary to modify the intermediate plate containing the collectors to make a pulsed heat pipe instead of a thermosiphon.

[0015] Advantageously, the channels are delimited by flat faces that define angles favorable to heat exchange. Even more advantageously, the grooves are structured so that all or part of the angles are acute, further promoting heat transfer.

[0016] The present invention relates to a thermosiphon comprising a stack of plates joined together to define a fluidic circuit, said fluidic circuit comprising at least two channels partially filled with a fluid, said stack comprising: two end plates, at least one first intermediate plate disposed between the two end plates, said first intermediate plate having at least two grooves passing through the first intermediate plate through its entire thickness, each groove having a first end and a second end, said first ends being located in an area called the "evaporator zone" and said second ends being located in an area called the "condenser zone", the evaporator zone being distinct from the condenser zone, at least one first collector at the evaporator zone and connecting fluidic at least two grooves only at the first ends, at least one second collector at the condenser zone and connecting fluidic at least two grooves only at the second ends, said first and second collectors being such that they connect the grooves in parallel, at least one second intermediate plate in direct contact with the first intermediate plate and comprising at least one of the first and second collectors.

[0017] The present invention also relates to a pulsed heat pipe comprising a stack of plates joined together so as to define a fluidic circuit comprising at least one channel, and filled with a fluid, said fluidic circuit comprising at least one zone called the evaporator zone and at least one zone called the condenser zone, said stack comprising: two end plates, at least one first intermediate plate disposed between the two end plates, said first end plate having a plurality of grooves going all the way through the first intermediate plate over its entire thickness, each groove having a first end and a second end, at least one first connector at said first ends and making fluidic communication between the grooves two by two only at the first ends, at least one second connector at second ends and making fluidic communication between the grooves two by two only at the second ends, said first and second connectors being such that they connect the grooves in series, at least one second intermediate plate in direct contact with the first intermediate plate and having at least one of the first and second connectors.

[0018] Advantageously, the channel(s) is / are delimited by four planes.

[0019] The section of a channel or channels preferably includes at least two vertices whose angle is between 70° and 85°.

[0020] For example, collectors or connectors are formed by grooves.

[0021] The thermosiphon or pulsed heat pipe may include at least one other first intermediate plate with grooves.

[0022] In one example, the thermosiphon or pulsed heat pipe includes at least one other second intermediate plate with cutouts to connect all or part of the grooves together.

[0023] Advantageously, the thermosiphon or pulsed heat pipe includes at least one heat exchanger in the evaporator zone and / or the condenser zone. The heat exchanger can be a radiator attached to at least one of the end plates.

[0024] Advantageously, the heat exchanger is formed directly in one of the stack plates. The heat exchanger can be a radiator formed directly in at least one of the end plates.

[0025] The heat exchanger may include a fluidic circuit formed in the intermediate plate, in which a liquid or two-phase fluid circulates.

[0026] In one example, the pulsed heat pipe has at least two grooves of different widths connected directly.

[0027] The grooves can form a channel with the connectors, forming a closed loop.

[0028] In one example, the heat pipe is shaped to have a serpentine form or to be wound around itself having straight portions connected by bends, the first ends of the grooves being located at one free end of the heat pipe and the second ends of the grooves being located at another free end.

[0029] In another example, the heat pipe is shaped to present a serpentine form or to be wound upon itself having straight portions connected by bends, the first ends of the grooves being located at one free end of the heat pipe and the second ends of the grooves being located at another free end, and the collector and the grooves are formed in the same intermediate plate.

[0030] The present invention also relates to a heat extraction system comprising a pulsed heat pipe according to the invention, in which the pulsed heat pipe has two lateral edges formed by stacking the end plates and at least the first intermediate plate and at least the second intermediate plate, and comprising a thermal conduction plate in thermal and mechanical contact by one face with only a part of one of the lateral edges, the other face being configured to receive a device from which heat is to be extracted.

[0031] The thermal conduction plate can be in contact with all straight portions.

[0032] The present invention also relates to a method for implementing a pulsed heat pipe according to the invention, comprising: the supply of at least three plates, structuring one plate so as to form parallel grooves through the entire thickness of the plate, stacking the plates so that the structured plate is in contact with and arranged between the other two plates, assembling the plates, partially filling the grooves with a fluid.

[0033] The present invention also relates to a method for manufacturing a pulsed thermosiphon or heat pipe according to the invention, comprising: a') the supply of at least four plates, b') structuring one plate so as to form parallel grooves through the entire thickness of the plate, c') structuring a second plate so as to form at least one cutout, d') stacking the plates so that the first plate and the second plate are in contact and arranged between the other two plates, e') assembling the plates, f') partially filling the grooves with a fluid.

[0034] Steps b) or steps b') and c') can be carried out by punching

[0035] Step d) or e') can be carried out by welding, brazing, gluing.

[0036] For example, at least part of the plates are made of a first aluminum alloy, are coated with a second aluminum alloy having a melting point lower than that of the first aluminum alloy, and the assembly is carried out by eutectic brazing. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The present invention will be better understood on the basis of the following description and the accompanying drawings, in which: there figure 1 is a perspective view of an example of an embodiment of a thermosiphon according to the invention, the figure 2 is an exploded view of the thermosiphon of the figure 1 , THE figures 3A to 3C are cross-sectional views of thermosiphon channels according to different embodiments, the Figures 4A and 4Bare perspective views of thermosiphon integration of the figure 1 in thermally regulated systems, the figure 5 is an exploded view of an example of a pulsed heat pipe according to the invention, the figure 6A represents a detail of the plates used in the pulsed heat pipe of the figure 5 , there figure 6B is a cross-sectional view of the figure 5 along the PC plan, the figure 7 , is a schematic representation of the pulsed heat pipe's fluidic circuit, the figure 8 is a top view of a plate according to another embodiment that can be implemented in a pulsed heat pipe according to the invention, the figure 9A is a perspective view of another example of an embodiment of a thermosiphon according to the invention, the figure 9B is an exploded view of the thermosiphon of the figure 9A , there Figure 10is an exploded view of a thermosiphon according to another embodiment including a liquid cooling circuit at the condenser figure 11 is a thermosiphon according to the invention having undergone a folding step, the figure 12 is a perspective view of another example of an embodiment of a pulsed heat pipe according to the invention, the figure 13 is an exploded view of the pulsed heat pipe of the figure 12 before folding into a serpentine shape. DETAILED DESCRIPTION OF SPECIFIC METHODS OF IMPLEMENTATION

[0038] In the following description, the terms "groove" and "channel" will be used interchangeably. Indeed, grooves made in a plate form channels in cooperation with other plates.

[0039] On the Figures 1 And 2 , we can see a T1 thermosiphon according to an example of its implementation.

[0040] The thermosiphon T1 includes a fluidic circuit C filled with a fluid, a first zone 2 intended to exchange heat with a heat source, to achieve thermal control, heat transfer, component cooling.

[0041] The heat source at the evaporator is, for example, an electrical component, an electronic circuit, an electronic component, such as a thyristor-type power electronic component or an insulated-gate bipolar transistor, a lighting device including light-emitting diodes, a photovoltaic device, a heat-releasing chemical reactor, a hot storage, a battery, a fuel cell, or any other power system.

[0042] Heat sinks at the condenser include, for example, forced convection fins, cold plates in single or two-phase flow, and cold storage.

[0043] Hot and cold storage devices, for example, are storage devices that utilize one or more phase-change materials, allowing for the smoothing of heat inputs or sinks from electrical / electronic components through thermal storage.

[0044] The thermosiphon includes a second zone 4 designed to exchange heat with a cold source, designated as the condenser zone.

[0045] The cold source can, for example, include a natural or forced convection radiator or a system where an endothermic reaction takes place.

[0046] The radiator can be chosen from, for example, pleated fin radiators, extruded fin radiators, studded fin radiators, molded fin radiators, knurled fin radiators, 3D-printed fin radiators, or any other heat exchange device. Alternatively, the fins can be skived fins, which are produced using a method called "skiving" that involves scraping the surface of soft metal with a tool and pushing away the shavings to create fins with a high aspect ratio. This method offers a reduced production cost.

[0047] The condenser zone and the evaporator zone are located at a distance from each other and are connected by the fluidic circuit, the fluid evaporating in the evaporator zone and condensing in the condenser zone.

[0048] The thermosiphon consists of a stack of plates or sheets assembled together, delimiting the fluidic circuit C between them.

[0049] In the example shown, the stack consists of four plates: two end plates P1 and P2, a first intermediate plate P3, a second intermediate plate P4 in direct contact with the first intermediate plate P3.

[0050] The two end plates are the plates located furthest from the stack. In the example shown, they are solid.

[0051] The intermediate plates P3 and P4 are located between the end plates.

[0052] The first intermediate plate P3 has a plurality of grooves 6 through the entire thickness of the plate P3. In the example shown, and advantageously, the grooves are parallel to each other, but such an arrangement is not limiting.

[0053] Each groove has a first end 6.1 located in the evaporator zone 2 and a first end 6.2 located in the condenser zone 4.

[0054] The second intermediate plate P4 includes balancing means suitable for balancing the load between the channels at their first 6.1 and second 6.2 ends.

[0055] The balancing means include a first groove 8 oriented transversely to the grooves 6, such that it is located at the first ends 6.1 of the channels 6 and extends over all the grooves. The balancing means also include a second groove or cutout 10 oriented transversely to the grooves 6, such that it is located at the second ends 6.2 of the channels 6 and extends over all the grooves. The first transverse groove 8 ensures fluid communication between all the channels in the evaporator zone, and the second transverse groove 10 ensures fluid communication between all the channels in the condenser zone.

[0056] In the example shown, finned radiators 12 are provided on the end plates P2 and P3, opposite the condenser area 4 so as to promote heat dissipation.

[0057] Grooves 6 and transverse grooves 8 and 10 are advantageously produced by punching, a technique particularly suited to medium and large production runs. In other examples, they can be produced by laser cutting, waterjet cutting, or through-etching.

[0058] The operation of the thermosiphon Figures 1 And 2 will now be described.

[0059] The heat emitted by the heat source is transferred to the fluid in the evaporator zone. The fluid evaporates and travels through the channels to the condenser zone, where it condenses and releases its heat to the cold source. The liquid then returns to the evaporator zone via the radiator fins. Vapor flows from the evaporator zone to the condenser zone, roughly in the center of the channels, while liquid flows from the condenser zone to the evaporator zone along the channel walls. The pressure between the channels is balanced by transverse grooves in the condenser and evaporator zones.

[0060] The plates, for example, have a thickness ranging from 0.05 mm to 6 mm, preferably equal to 3 mm.

[0061] Channels 6, for example, have a width between 0.5 mm and 10 mm, advantageously equal to 3 mm.

[0062] Channels 8 and 10 for example have a width between 0.5 mm and 10 mm, advantageously equal to 3 mm.

[0063] The dimensions of the plates can range, for example, from a few centimeters to a few meters.

[0064] The plates or sheets are made of a material with good thermal conductivity so as to conduct heat from the heat source to the evaporator zone and from the condenser zone to the cold source. They are made, for example, of aluminum alloy, copper, or stainless steel.

[0065] The sheet metal assembly process used depends on the material of the plates.

[0066] For example, in the case of aluminum alloy plates, by salt bath brazing, inert gas brazing, ultrasonic welding, friction welding, bonding... In the case of clad aluminum sheets, i.e. aluminum alloy sheets with one or both faces coated with a lower melting point aluminum alloy, these can be assembled by vacuum brazing.

[0067] In the case of copper, stainless steel, or superalloy plates, diffusion welding, diffusion brazing, and bonding can be used.

[0068] The channels are filled with fluid, for example, using a filling nozzle 15 inserted into the edge of the intermediate plate P3, as shown schematically on the figure 2Alternatively, a small plug can be used, fixed to an opening in the end plates and perpendicular to them. The plug is then pinched or sealed. Since all the channels communicate with each other via the transverse grooves, filling can be carried out through only one channel.

[0069] The filling fluid can be chosen from fluids commonly used in thermosiphons, and is chosen according to the operating temperature range of the device to be cooled, and also the temperatures at which the thermosiphons are likely to be stored, for example to withstand freezing phases.

[0070] The filling fluids that can be used are those commonly used in this type of application.

[0071] As an example, for an aluminum alloy thermosiphon assembled by eutectic brazing, ammonia, acetone, methanol, n-heptane, R134a or another fluorinated refrigerant can be used as a fluid.

[0072] In the example shown, and advantageously, the means for balancing the load between the channels in the evaporator and condenser zones are implemented in the same intermediate plate P4, thus reducing the number of plates required. However, it would be possible to implement another intermediate plate positioned between the end plate P1 and the intermediate plate P3, and to create the transverse groove 8 in a plate P4 and the transverse groove 10 in the additional intermediate plate.

[0073] Furthermore, the grooves can have different widths and / or a width that varies.

[0074] Furthermore, in the example shown, the thermosiphon has an inverted L shape; this design is by no means limiting, it could be a straight or curved bar. The shape of the thermosiphon is adapted to the environment in which it will be integrated.

[0075] On the figure 11 We can see a thermosiphon in three dimensions. The thermosiphon has been folded to present a shape extending in several planes; in this example, the two planes are orthogonal. This configuration is particularly well-suited for cooling an electrical circuit breaker.

[0076] It is then possible to adapt the shape of the thermosiphon even further to the environment to be thermalized.

[0077] The thermosiphon can be folded multiple times along one or more planes. Furthermore, the folding angle(s) can be arbitrary. This folding can advantageously be performed after the stack of plates has been manufactured. It should be noted that the folding angle is chosen according to the thickness of the device to prevent crushing of the channels and / or delamination of the plates.

[0078] This folding step can be carried out before assembling the plates to avoid the risk of delamination, however the tooling for assembly is considerably more complex.

[0079] On the figure 3A , we can see a cross-sectional view of an example of a channel formed by a groove 6, the intermediate plate P4 and the end plate P1.

[0080] The vertices of the channel section are defined by substantially flat faces. The vertices therefore present an angle, a right angle in this example, and not a rounded shape as in the case of a partial engraving of the plate.

[0081] The presence of these angles promotes capillary action. Heat transfer is improved and the entrainment limit is pushed back.

[0082] On the figure 3BAn advantageous example of a channel cross-section shape can be seen in which the lateral edges 24 of the grooves 6 are inclined to form two acute angles α at vertices A with one of the plates P1 and P4. The acute angles promote fluid adhesion and are therefore even more favorable for heat transfer. In this example, the two edges have opposite inclinations. According to another example, the two edges could have the same inclination; in this case, the acute angles at the vertices would not be delimited by the same plate P1 or P4. The inclined lateral edges of the grooves can be obtained by punching.

[0083] On the figure 3C We can see another example of the realization of a channel having four angles with four acute vertices A. Each edge 24 of the grooves has two opposite inclinations 24.1, 24.2.

[0084] Such grooves are made, for example, by using two plates, and by making grooves with inclined lateral edges in each of the two plates, such as those of the figure 3B , for example by punching, then turning one plate over and pressing it against the other so that the grooves overlap.

[0085] The angle α is at least equal to 70°, preferably greater than 80° and very advantageously equal to 85°.

[0086] The two or four vertices A can have different angle values.

[0087] Alternatively, the grooves are created using a laser.

[0088] Depending on the material of the plates, a surface treatment of the channel walls is advantageous to make them wettable to the fluid. For example, in the case of a copper thermosiphon, chemical oxidation can be applied to make it wettable to water. In the case of a refrigerant, no treatment is required, as copper is inherently wettable. In the case of aluminum alloys, due to the presence of native aluminum oxide, they offer good wettability to fluids compatible with aluminum alloys.

[0089] On the figure 4A , we can see the T1 thermosiphon of the figure 1The thermosiphon is attached to a busbar 14 of a circuit breaker that is to be cooled. It is fixed to the busbar at the evaporator zone, for example by means of screws 18, so that an outer face of the end face P1 is in flat contact with the busbar 14 to provide excellent thermal contact and ensure efficient heat transfer between the busbar and the evaporator zone. The thermosiphon is oriented so that the evaporator zone is below the condenser zone, with the return of the liquid to the evaporator zone occurring by gravity.

[0090] On the figure 4BAnother example of integration can be seen in which the thermosiphon is used to cool a circuit board 20 carrying one or more power components 22. The thermosiphon is fixed to the board so that the outer face of the end plate P1 at the evaporator area is in planar contact with a power component 22. In this example, the thermosiphon consists of only a heat sink fixed to the end plate P2 at the condenser area, and the end plate P1 is in contact with the board. The board is, for example, vertical, facilitating the return of the liquid to the evaporator area.

[0091] Advantageously, the card and the thermosiphon can be immersed in a bath of dielectric oil or other suitable heat transfer fluid to further improve heat dissipation.

[0092] On the figure 5 , we can see an example of pulsed heat pipe CP1 according to the invention.

[0093] The pulsed heat pipe CP1 comprises a fluidic circuit C' filled with a fluid, an evaporator zone intended to exchange heat with a heat source, and a condenser zone intended to exchange heat with a cold source.

[0094] The pulsed heat pipe comprises a stack of plates or sheets assembled together, delimiting between them a fluidic circuit C'.

[0095] In the example shown, the stack consists of four plates: two end plates P101 and P102, a first intermediate plate P103, a second intermediate plate P104 in direct contact with the first intermediate plate P103.

[0096] The two end plates are the plates located furthest from the stack. In the example shown, they are solid.

[0097] The intermediate plates P103 and P104 are located between the end plates.

[0098] The first intermediate plate P103 has a plurality of grooves 106 through the entire thickness of the plate P103. In the example shown, and advantageously, the grooves are parallel, but such an arrangement is not limiting.

[0099] Each groove has a first end 106.1 located in the evaporator zone and a first end 106.2 located in the condenser zone.

[0100] The second intermediate plate P104 includes means for connecting the grooves so as to form a single channel.

[0101] On the figure 6A , we can see a detail of plate P103 at the ends 106.1 and a detail of plate P104 including part of the connection means.

[0102] The connection means include cutouts 108 dimensioned and arranged so that a cutout covers only two ends 106.1 of two successive grooves. Thus, one groove is connected to the adjacent groove. The figure 6B represents a cross-sectional view of the stacking of the four plates along the PP plane, we can see the ends 106.1 and the cutouts 108.

[0103] Similar means of connection are provided at the ends 106.2 of the grooves, however the cutouts are arranged so that they connect two successive grooves, these being different from those connected by the cutouts 108. The grooves thus connected form a single serpentine channel which flows alternately between the evaporator zone and the condenser zone.

[0104] On the figure 7 , we can see schematically the fluidic circuit thus formed in the pulsed heat pipe.

[0105] The connection means ensure that all grooves are connected in series.

[0106] In one example of implementation, the two ends of the channel thus formed remain separate.

[0107] In another particularly advantageous embodiment, the two ends of the channel are connected, preferably at the condenser, to form a closed-loop channel; the pulsed heat pipe is then a looped pulsed heat pipe. For example, an additional cutout is made in the second intermediate plate, which is shaped to connect the two ends of the serpentine channel. A looped pulsed heat pipe is more efficient because, in addition to the oscillations, there is overall fluid circulation in one direction.

[0108] As with the thermosiphon, it could be envisaged to make the connection means of the ends 106.1 in a plate 104 and the connection means of the ends 106.2 in another plate disposed between the plate P101 and the plate P103, or to make part of the cuts 108 in one plate and the other part in the other plate, similarly for the cuts connecting the ends 106.2.

[0109] In the example shown on the figure 6A all the grooves have the same width.

[0110] In a favorable example shown on the figure 8 The grooves 106 have different widths; for example, adjacent grooves have different widths. This asymmetry promotes oscillations that are advantageous for starting the pulsed heat pipe. For example, one groove has a width of 2 mm and the adjacent groove has a width of 3 mm; this pattern is repeated for all the grooves.

[0111] As with the thermosiphon, the invention advantageously allows for the creation of a channel with angles that promote capillary action.

[0112] Some or all of the angles can be acute, which improves heat exchange through capillary action. This is because the length of the triple contact lines between the liquid, vapor, and solid is increased, thus intensifying heat transfer, which is particularly high in this area. figures 3A to 3C apply to the pulsed heat pipe according to the invention.

[0113] The materials and dimension ranges given for the thermosiphon also apply to the pulsed heat pipe.

[0114] The operation of the pulsed heat pipe will now be described.

[0115] The heat emitted by the heat source is transferred to the fluid in the evaporator zone, causing it to evaporate. Vapor plugs form and alternate with liquid plugs. The oscillating movement of these plugs between the evaporator and condenser is achieved by the expansion of the vapor plugs in the evaporator and their contraction in the condenser. The fluid exchanges its heat in the condenser zone. As it moves, the fluid alternately enters the evaporator and condenser zones. Heat transfer occurs through latent heat due to evaporation and sensible heat due to the oscillating liquid plugs between the evaporator and condenser zones.

[0116] The integration of a pulsed heat pipe into a system to be cooled is similar to that of the thermosiphon described in the... Figures 4A and 4B .

[0117] As with the thermosiphon, the L-shape is only one example of a possible implementation. Furthermore, the pulsed heat pipe can also be bent and, for example, have the following configuration: figure 11 .

[0118] On the Figures 9A And 9B , we can see a thermosiphon according to another example of embodiment, in which the thermosiphon comprises several plates containing grooves forming superimposed channels.

[0119] The T2 thermosiphon has three first intermediate plates P3.1, P3.2 and P3.3 and two second intermediate plates P4.1 and P4.2.

[0120] Plate P4.1 is located between plates P3.1 and P3.2 and plate P4.2 is located between plates P3.2 and P3.3.

[0121] In this example, plates P4.1 and P4.2 have transverse grooves 8 and 10 connecting all the channels delimited in the three plates P3.1 to P3.3, and ensuring a balancing of the load between all the channels of the thermosiphon.

[0122] In another example, the balancing means are such that they ensure balancing between the channels of the same plate only or between the channels of a part of first intermediate plates.

[0123] With such a device, the transmitted thermal power is increased and the thermal resistance is reduced.

[0124] It will be understood that the heat transfer fluid can include any number of first intermediate layers and therefore of channel layers.

[0125] In the case of an even number of first intermediate layers, it is possible to consider using a second intermediate plate for two first intermediate layers.

[0126] Filling the thermosiphon of Figures 9A And 9B can be done like the thermosiphon of the figure 1 This can be achieved by using a single filler plug inserted into the edge of one of the first intermediate plates, provided that all the grooves communicate smoothly with each other. Alternatively, a plug fixed to an opening in one of the end plates can be used, for example, perpendicular to it.

[0127] In another embodiment example, after filling, for example the channel layers are fluidically isolated from each other by pinching a communication channel between the layers.

[0128] In another example of implementation, a filler tail can be provided for each first intermediate plate, or group of first intermediate plates.

[0129] The description of Figures 9A And 9BThis applies to a pulsed heat pipe, except with regard to the second intermediate plates. The intermediate plates are such that they ensure a connection between some or all of the grooves.

[0130] In one embodiment, the grooves are all connected in series; in this case, a single channel winds through the different plates. In another embodiment, groups of grooves are connected in series to form several separate channels. For example, the connection means could be such that they form a single channel through each first intermediate plate.

[0131] On the Figure 10 , we can see another example of a thermosiphon according to the invention.

[0132] The T3 thermosiphon differs from the T1 thermosiphon of the figure 1 in that it includes a heat exchanger 26 integrated at the condenser zone, which forms the cold source.

[0133] The thermosiphon includes an additional intermediate plate P5 which has a groove 28 arranged so as to be in line with the condenser area, and is intended to allow the circulation of a heat transfer fluid extracting the heat transported by the fluid circulating in the channels of the thermosiphon.

[0134] Plate P5 is interposed between the second intermediate plate P4 and the end plate P2, which, together with groove 28, defines a cooling circuit. Groove 28 is positioned so that it is not aligned with the transverse groove 10, ensuring load balancing at the ends 6.2 of the grooves.

[0135] In the example shown, the cooling circuit has an inlet 30 and an outlet 32 ​​of heat transfer fluid.

[0136] The heat transfer fluid can remain liquid or change phase during heat exchange in the condenser area.

[0137] In another embodiment, the heat exchanger can be of the air-to-air type. For example, the end plate P2 can directly integrate the radiator, for instance, by creating a perforated and / or pleated area. A large perforated area is possible because the end plate P2 is not used to seal the grooves 6. The perforated area is positioned so as not to be directly opposite the transverse groove 10. Using the end plate P2 to create a heat exchanger has the advantage of not requiring the addition of a separate plate.

[0138] Such a heat exchanger forming a heat source can also be implemented at the evaporator zone.

[0139] A thermosiphon can incorporate a heat exchanger that acts as a cold source and / or a heat exchanger that acts as a heat source. Furthermore, the heat exchangers can be of different types; one can be a liquid heat exchanger and the other an air or two-phase heat exchanger.

[0140] Such heat exchangers can also be implemented within the stack, particularly in cases where the thermosiphon or pulsed heat pipe has one or more channels in multiple layers, as shown in the diagrams. Figures 9A And 9B , in order to bring or extract heat to the core of the stack.

[0141] On the figure 12 , we can see an example of a pulsed heat pipe CP2 according to the invention applied to the cooling of a light-emitting diode lighting device 34.

[0142] The heat pipe CP2 is folded to form a coil. The coil comprises straight sections parallel to each other D1 to D8 connected in series by bends CD1 to CD7. The sections have faces of larger surfaces parallel to each other and connected by lateral edges B1, B2.

[0143] The lateral edges B1, B2 also have a serpentine shape, and the lighting device is arranged on the pulsed heat pipe so as to be in contact with the lateral edge B1 which, due to its serpentine conformation, forms a support.

[0144] A thermal conduction plate 36 is interposed between the lighting device and the lateral edge B1 and conducts heat from the lighting device to the heat pipe.

[0145] The conduction plate is positioned relative to the heat pipe so that, together with the lighting device, it forms a heat source for only a portion of the heat pipe, while the remaining portions of the heat pipe are in contact with a cold source. The conduction plate covers only a portion of the lateral edge, thus creating a localized heat source. In the example shown, the conduction plate 36 is positioned on a mid-section of the coil, leaving areas of the straight sections D1 to D8 and the bends CD1 to CD7 free from contact with the heat source, forming cold sources. Alternatively, the conduction plate is positioned on the bends CD1, CD3, CD5, CD7 or on the bends CD2, CD4, CD6. As a further alternative, the device comprises two conduction plates, one positioned on the bends CD1, CD3, CD5, CD7, and the other on the bends CD2, CD4, CD6.Alternatively, the conduction plate can be placed in the middle section of the coil, at one end, or at both ends of the coil. Furthermore, multiple conduction plates can be used for hot zones.

[0146] This device is particularly suitable for cooling electronic and / or electrical components.

[0147] On the figure 13 We can see an exploded view of an example of a pulsed heat pipe implementation, before coiling, which can be used in the system of the figure 12 .

[0148] It comprises two end plates P201 and P202, a first intermediate plate P203 and a second intermediate plate P204 in direct contact with the first intermediate plate P203.

[0149] The first intermediate plate has two parallel grooves 206 extending along the length of plate P203, and the second intermediate plate P204 has two transverse grooves 208 such that the two grooves 206 are connected at their longitudinal ends, forming a single channel in a closed loop. The transverse grooves 208 are similar to the grooves 108 of the figure 5 .

[0150] The plates are assembled according to the assembly methods described above.

[0151] The heat pipe is then bent to form a coil and the thermal conduction plate is fixed to the lateral edge B1 for example by welding or gluing, preferably the welding material or glue ensures good heat conduction.

[0152] The heat pipe may include heat exchange fins arranged between the straight sections D1 to D8 and in thermal contact with them.

[0153] The operation of this system will now be described.

[0154] The lighting device and the conduction plate form the heat source. Each portion D1 to D8 is therefore in contact with the heat source.

[0155] The areas of portions D1 to D8 free from contact with the conduction plate and the bends CD1 to CD7 are in contact with a cold source, which is the air, with which they exchange heat by natural convection. Forced convection methods may be implemented.

[0156] The channel alternately passes through a cold source and the heat source.

[0157] The fluid in the channel formed by the grooves opposite the conduction plate 36 evaporates. It is assumed that the heat diffuses over at least part of the height of the heat pipe, from the lateral edge B1 to the lateral edge B2. The loop through the groove 206 on the side of edge B2 allows the temperature of the heat pipe to be homogenized along its length.

[0158] The fluid in the channel at the cold springs condenses. This results in the formation of vapor plugs that alternate with liquid plugs. The oscillating movement of these plugs between the evaporator and condenser is achieved by the expansion of the vapor plugs at the evaporator and their contraction at the condenser. The fluid exchanges heat in the condenser zone. As it moves, the fluid alternately enters the evaporator and condenser zones. Heat transfer occurs through latent heat due to evaporation and sensible heat due to the oscillating liquid plugs between the evaporator and condenser zones.

[0159] This example of implementation is very advantageous because the number of straight zones is significant, which is favorable for the start-up and operation of the heat pipe; preferably, it is desirable to have at least 16 straight zones to obtain a good start-up and operation of the pulsed heat pipe.

[0160] In the example shown, each section D1 to D8 has two straight zones. The heat pipe therefore has 16 straight zones.

[0161] Alternatively, more than two grooves 206 can be provided in the height of the heat pipe.

[0162] For example, the plates have a width of 10 mm, which corresponds approximately to the length of the grooves 206.

[0163] Alternatively, the heat pipe can be shaped into a rectangular or cylindrical spiral. The slightly curved shape of the "straight sections" does not interfere with the operation of the pulsed heat pipe.

[0164] Alternatively, a single intermediate plate is used, featuring two parallel grooves and a single transverse groove; the resulting channel is then not looped. This simplifies the construction.

[0165] Alternatively, the pulsed heat pipe of the figure 1 may include several first intermediate plates defining several layers of superimposed channels, these being connected to each other or not.

[0166] It will be understood that any other device to be cooled can be placed on the conduction plate.

[0167] An example of a method for constructing a thermosiphon of the figure 1 will now be described. This description applies to the manufacture of a pulsed heat pipe, with the cutouts made in the second intermediate plate being adapted.

[0168] Four plates are cut to the same dimensions, two will serve as end plates and two as intermediate plates.

[0169] One of the intermediate plates is structured, for example punched to form grooves 6.

[0170] The other intermediate plate is structured to form cutouts 8 and 10.

[0171] The plates are stacked one on top of the other, with the two intermediate plates placed against each other between the two end plates.

[0172] The plates are then assembled, for example by brazing.

[0173] The channels are partially filled with fluid.

[0174] As an example only, an example of manufacturing a thermosiphon using aluminum plates by eutectic brazing of clad sheets will be described.

[0175] To achieve this, one side of the aluminum alloy sheets is coated with an aluminum alloy with a lower melting point.

[0176] For example, a core sheet made of an AA3xxxx series alloy will be used, coated with a eutectic alloy from the AA4xxxx series containing lower-melting-point silicon. The coating is applied using a known roll-bond technique, i.e., by rolling the sheets together.

[0177] Sheets are chosen with a thickness between 0.05 mm and 5 mm, with a coating typically of 5 to 10% of the total thickness.

[0178] The coated sheets are hot-pressed at a temperature above the eutectic melting point, but below the core alloy temperature; the eutectic alloy is then melted, forming a leak-proof brazing alloy between the two sheets.

[0179] The channels are then partially filled with fluid.

[0180] The thermosiphon and pulsed heat pipe according to the invention are simplified in construction compared to those of the prior art.

Claims

1. Thermosiphon including a stack of plates secured to each other so as to delimit a fluidic circuit, said fluidic circuit including at least two channels partially filled with a fluid, said stack comprising: - two end plates (P1, P2), - at least one first intermediate plate (P3) disposed between the two end plates (P1, P2), said first intermediate plate (P3) comprising at least two grooves (6) passing right through the first intermediate plate (P3) over its entire thickness, each groove (6) comprising a first end (6.1) and a second end (6.2), said first ends (6.1) being located in a so-called "evaporator zone" (2) and said second ends (6.2) being located in a so-called "condenser zone" (4), the evaporator zone (2) being separate from the condenser zone (4), - at least one first manifold in the evaporator zone (2) and putting in fluidic communication at least two grooves (6) only at the first ends (6.1), - at least one second manifold in the condenser zone (4) and putting in fluidic communication at least two grooves (6) only at the second ends (6.2), - said first and second manifolds being such that they connect the grooves (6) in parallel, - at least one second intermediate plate (P4) in direct contact with the first intermediate plate (P3) and comprising at least one of the first and second manifolds, said first and second manifolds advantageously being formed by grooves.

2. Thermosiphon according to claim 1, wherein the channel(s) are delimited by four planes, the cross-section of a channel or channels advantageously comprising at least two vertices (A) the angle of which is between 70° and 85°.

3. Thermosiphon according to one of claims 1 or 2, comprising at least one other first intermediate plate provided with grooves and advantageously comprising at least one other second intermediate plate provided with cutouts so as to connect all or some of the grooves together.

4. Thermosiphon according to one of claims 1, 2 or 3, comprising at least one heat exchanger at the evaporator zone and / or the condenser zone, said heat exchanger advantageously being either a heat exchanger comprising a fluidic circuit formed in the intermediate plate, and in which a liquid or two-phase fluid flows, or a radiator attached to at least one of the end plates or formed directly in at least one of the end plates.

5. Pulsating heat pipe comprising a stack of plates secured to each other so as to delimit a fluidic circuit comprising at least one channel, and filled with a fluid, said fluidic circuit comprises at least one zone called evaporator zone and at least one zone called condenser zone, said stack comprising: - two end plates (P101, P102), - at least one first intermediate plate (P103) disposed between the two end plates (P101, P102), said first end plate (P103) comprising a plurality of grooves (106) passing right through the first intermediate plate (P103) over its entire thickness, each groove (106) comprising a first end (106.1) and a second end (106.2), - at least one first connector at said first ends (106.1) and fluidly communicating the grooves (106) two by two only at the first ends (106.1), said first connector being formed by a plurality of through cutouts (108), - at least one second connector at the second ends (106.2) and fluidically putting the grooves (106) in communication two by two only at the second ends (106.2), said second connector being formed by a plurality of through cutouts (108), - said first and second connectors being such that they connect the grooves (106) in series, - at least one second intermediate plate (P104) in direct contact with the first intermediate plate and comprising at least one of the first and second connectors, said first and second connectors advantageously being formed by grooves.

6. Pulsating heat pipe according to claim 5, wherein the channel(s) are delimited by four planes, the cross-section of a channel or channels advantageously comprising at least two vertices (A) the angle of which is between 70° and 85°.

7. Pulsating heat pipe according to claim 5 or 6, comprising at least one other first intermediate plate provided with grooves and, advantageously comprising at least one other second intermediate plate provided with cutouts so as to connect all or some of the grooves together.

8. Pulsating heat pipe according to one of claims 5, 6 and 7, comprising at least one heat exchanger in the evaporator zone and / or the condenser zone, said heat exchanger being either a heat exchanger comprising a fluidic circuit formed in the intermediate plate, and in which a liquid or two-phase fluid flows, or a radiator attached to at least one of the end plates or formed directly in at least one of the end plates.

9. Pulsating heat pipe according to one of claims 5 to 8, comprising at least two grooves with different widths connected directly.

10. Pulsating heat pipe according to one of claims 5 to 8, wherein the grooves form with the connectors a channel forming a closed loop, the heat pipe advantageously being shaped to have a coil shape or to be wound on itself comprising straight portions connected (D1, D8) by elbows (CD1, CD7), the first ends of the grooves being located at a free end of the heat pipe and the second ends of the grooves of the grooves being located at another free end.

11. Pulsating heat pipe according to any one of claims 5 to 9, wherein the heat pipe is shaped to have a coil shape or to be wound on itself comprising straight portions connected (D1, D8) by elbows (CD1, CD7), the first ends of the grooves being located at a free end of the heat pipe and the second ends of the grooves of the grooves being located at another free end, and wherein the heat pipe comprises a single intermediate plate in which the connector and the grooves are formed.

12. Heat extraction system comprising a pulsating heat pipe according to claim 10 or 11, wherein the pulsating heat pipe comprises two lateral edges (B1, B2) formed by the stack of the end plates (P202) and at least the first intermediate plate (P203) and at least the second intermediate plate (P204), and comprising a thermal conduction plate (36) in thermal and mechanical contact by one face with only a part of one (B1) of the lateral edges, the other face being configured to receive a device from which heat is desired to be extracted, the thermal conduction plate (36) advantageously being in contact with all the straight portions (D1, D8).

13. Method for manufacturing a pulsating heat pipe according to claim 11, comprising: a) supplying at least three plates, b) structuring a plate so as to form parallel grooves passing through the entire thickness of the plate, c) stacking the plates so that the structured plate is in contact and disposed between the other two plates, d) assembling the plates, e) partially filling the grooves with a fluid.

14. Method for manufacturing a thermosiphon or a pulsating heat pipe according to one of claims 1 to 12, comprising: a') supplying at least four plates, b') structuring a plate so as to form parallel grooves passing through the entire thickness of the plate, c') structuring a second plate so as to form at least one cutout, d) stacking the plates so that the first plate and the second plate are in contact and disposed between the other two plates, e') assembling the plates, f') partially filling the grooves with a fluid.

15. Manufacturing method according to claim 13 or 14, wherein the steps b) or the steps b') and c') are performed by punching, and / or wherein the step d) or e') is performed by welding, soldering, gluing.

16. Manufacturing method according to one of claims 13 to 15, wherein at least a part of the plates is made of a first aluminum alloy is coated with a second aluminum alloy having a lower melting point than that of the first aluminum alloy, and wherein the assembly is carried out by eutectic brazing.