HEAT PIPE WITH IMPROVED PERFORMANCE UNDER VARIOUS HEAT LOAD DISTRIBUTIONS

Description

technical field

[0001] The invention relates to heat pipes, heat transfer devices, particularly for cooling a heating element. Context

[0002] A heat pipe typically comprises a central axial channel in which working fluid moves in the form of vapor, and longitudinal grooves extending axially and around the central axial channel, designed to advance the working fluid in the form of liquid in a direction opposite to that of the vapor.

[0003] In the case of an unevenly distributed heat load around the heat pipe, the grooves operate very differently, and the most heavily stressed grooves can dry out while the others experience only minimal activity. This phenomenon can also result from an uneven and fluctuating distribution of hot and cold sources along the heat pipe, as is frequently the case in many heat pipe applications (heat pipe networks, heat distribution on radiators, temperature uniformity over a relatively large surface, etc.).

[0004] This observation leads in practice to oversizing the heat pipe to avoid groove drying in the case of a thermal load that is not regularly distributed, or which may even change over time.

[0005] US documents 2007 / 240855, DE 20 2005 021911 U1 and US 2020 / 248970 each relate to heat pipes.

[0006] The inventors sought to improve this situation. Description of the invention

[0007] For this purpose, a heat pipe (1) is proposed, configured for use under low or zero gravity, comprising a profiled body (10) generally obtained by extrusion, said profiled body extending along a longitudinal path (PX), said profiled body forming a hollow body closed at at least two ends by closing elements, thus forming an internal space hermetically isolated from the external environment, and filled with a predefined volume of two-phase working fluid, said profiled body comprising a plurality of longitudinal channels (3) (realized in practice as longitudinal grooves), each of said channels having a section delimited by a bottom (76) formed by a peripheral tubular wall (75) of the profiled body, and laterally by two longitudinal walls (2) which extend radially inwards from the peripheral tubular wall, the longitudinal channels surrounding an axial channel (15) (conveying steam), the longitudinal channels being open in the direction of the axial channel, characterized in that it is provided, at at least a first position (P1) along the longitudinal path (PX), a circumferential transfer channel (6), arranged transversely to the local axial direction (X), and making fluid communication all or part of the plurality of longitudinal channels between them, and in that the longitudinal walls are interrupted, partially or totally, at the place of the circumferential channel.

[0008] Thanks to these features, the circumferential transfer channel allows neighboring grooves to contribute to the liquid fluid supply function, alongside the most stressed groove(s). Liquid flows through the circumferential transfer channel from a less stressed groove to a more stressed one. This helps to overcome the thermal load limits that could lead to partial or total drying of one or more of the most stressed grooves. The areas most subjected to thermal stress are those where the vaporization flow rate is highest.

[0009] It should be noted that the longitudinal path (PX) can be rectilinear or non-rectilinear. If the path is not rectilinear, the axial direction is therefore local and not an absolute direction.

[0010] It should be noted that the circumferential transfer channel (6) generally presents as an annular passage. In practice, it often presents as an annular groove.

[0011] It should be noted that the longitudinal channels are made like longitudinal grooves, generally obtained by extrusion and material coming into contact with the main profiled body.

[0012] It should be noted that the circumferential transfer channel can seamlessly connect all the longitudinal channels, as the annular passage makes a complete turn. However, it is possible that in specific configurations with predetermined thermal loads, the circumferential transfer channel could seamlessly connect the longitudinal channels over half the circumference (only half a turn) or over one or more arbitrary angular ranges.

[0013] It should be noted that the cross-section of longitudinal canals can take various forms, as the bottom is not necessarily flat, and the walls are not necessarily straight. In one particular example, the cross-section of the longitudinal canals has a general concavity. In another particular example, the cross-section of the longitudinal canals may generally be an arc of a circle or an oval. In yet another particular example, the cross-section of the longitudinal canals may be trapezoidal.

[0014] In various embodiments of the invention relating to the process, one may optionally also use one and / or the other of the following provisions, taken separately or in combination.

[0015] In one option, the circumferential transfer channel runs all the way around, seamlessly connecting all the longitudinal channels. This ensures consistent and predictable behavior regardless of the load distribution around the heat pipe. Wherever the circumference is most thermally loaded, the most thermally stressed groove(s) receive additional coolant from the other grooves via the circumferential transfer channel.

[0016] One option involves using several circumferential transfer channels arranged end-to-end longitudinally. This multiplies the fluid redistribution effect and increases capillary pressure over an entire area.

[0017] Depending on one option, depending on particular groove dimensions, especially fine circumferential grooves for example, it is possible to do without the cover ring which is discussed just after here.

[0018] According to one option, the circumferential transfer channel can be radially delimited inwardly by a cover ring, the cover ring being interposed between the circumferential transfer channel and the axial channel. Advantageously, the presence of the cover ring promotes the formation of liquid meniscus on its wall and the walls of adjacent walls. The presence of the cover ring increases the capillary pressure at this axial position of the heat pipe. Advantageously, the ring design is optimized to limit local pressure losses in the longitudinal flow, whether in the liquid or vapor phase.

[0019] According to one option, the circumferential channel can be arranged at an intermediate position, with the walls (2) interrupted at a predefined length (L6) at that point. Thus, for a circumferential channel in an intermediate position, it can be made as an annular passage by means of a material removal operation with a rotary tool such as a centrifugal cutter, or by electrical discharge machining or other general machining technique.

[0020] According to one option, at the location of the circumferential channel, the material of the walls (2) is preferably removed to a height (H6) between 50% and 100% of the height (H2) of the walls.

[0021] According to one option, at the location of the circumferential channel, a retaining wall footing remains at a residual height (H7) between 0% and 50% of the normal height (H2) of the walls. Maintaining this retaining wall footing allows for the preservation of longitudinal contact lines to channel the liquid by capillary action, despite the presence of the circumferential transfer channel.

[0022] According to one option, the walls may include a first bearing area (B1) to receive a first longitudinal end of the cover ring (4) and a second bearing area (B2) to receive a second longitudinal end of the cover ring. The ring is thus held securely in place on the bearing areas relative to the walls, on either side of the circumferential transfer channel.

[0023] According to one option, the cover ring (4) may include a central overhang (45) forming a radially external shoulder received between the walls at the location of the first and second bearing zones (B1, B2). This is a simple and robust solution, since machining the annular groove is relatively straightforward and such a ring with an overhang can be obtained by standard turning / machinery.

[0024] According to one option, the cover ring (4) can have a constant thickness, and the first and second bearing areas are then formed as flats (14) set back from the top of the walls. By using a suitable milling cutter or two machining passes to form the circumferential channel, the ring is then a simple cylinder obtained by sawing a tube, a very inexpensive component.

[0025] According to one option, the cover ring (4) can be made of a deformable material, either in the elastic or plastic range, so that the cover ring can be inserted from one end of the profiled body to the first and second bearing zones, so that in the target position the cover ring closes the circumferential transfer channel radially inwards. At the target position, the elastic force is released or a plastic force (deformation) is applied outwards to achieve the final positioning.

[0026] According to one option, the first position (P1) is chosen in the vicinity of an evaporation portion (71) of the heat pipe coupled to a hot source (81). This optimizes the effect of pressure equalization of the liquid phase in the longitudinal channels as close as possible to the area where drying under high thermal load must be avoided.

[0027] According to one option, the first position (P1) is an intermediate position on the longitudinal path. Since this intermediate position can be arbitrary on the longitudinal path, there is complete freedom to position the circumferential transfer channel (or channels) as close as possible to the point of need.

[0028] According to one option, the first position (P1) is an end position on the longitudinal path. In this configuration, it is easier to remove material from the walls to form the annular groove that constitutes the transfer channel.

[0029] In one option, the circumferential channel is formed in an end cap (5) attached to one end of the profiled body. In this configuration, no further processing is performed on the extruded profiled body. The complexity of the shapes and the attachment is borne by the end cap.

[0030] Depending on the option, one or more additional circumferential channels are provided along the path, at distinct axial positions different from the first position. These multiple positions can be advantageously determined according to the application or distributed regularly along the longitudinal direction, over all or part of the heat pipe.

[0031] Depending on the design, the heat pipe can include a combination of circumferential channels, some arranged in an intermediate longitudinal position and some arranged at the ends. In other words, there is no incompatibility in having several circumferential channels of different types coexisting.

[0032] Depending on the design, the heat pipe can include a combination of different types of circumferential channels. For example, it can have annular channels (360°) on the condenser side and partially annular channels (<360°) on the evaporator side. If the heat load is known, the circumferential channels can be adapted to optimize thermo-hydraulic performance.

[0033] Depending on the option, a plurality of circumferential channels can be provided along the path, at regularly spaced axial positions (P2, P3, P4), with a predetermined pitch, for example every 300 mm. This allows the liquid phase pressures to be equalized in all grooves at regular intervals along the heat pipe.

[0034] Depending on the option chosen, one or more intersections can be planned along the heat pipeline route, with two circumferential channels arranged on either side of each intersection. This minimizes the potentially negative effect of the intersection on the hydraulic continuity between the channels.

[0035] Depending on the option chosen, the heat pipe can be designed as a three-dimensional object. It then extends in space in three Cartesian dimensions, and not just in a plane. This advantageously provides complete freedom in design and configuration to perfectly suit all possible applications.

[0036] Advantageously, the proposed solutions do not contain any porous layers, porous masses, or porous coatings in the heat pipes, either locally or along their entire length. In other words, the proposed heat pipes are free of any capillary porous material intended to ensure capillary pumping. Description of figures

[0037] Other aspects, objects, and advantages of the invention will become apparent from the following description of an embodiment of the invention, given by way of non-limiting example. The invention will also be better understood with reference to the accompanying drawings, in which: There figure 1 schematically represents a heat pipe coupled to a hot source on one side and a cold source on the opposite side. figure 2 This schematically represents a heat pipe coupled to a hot source in an intermediate position on one side and coupled to two cold sources at the ends. figure 3This schematically represents a heat pipe coupled to a continuous cold source along its length, in the upper part of the heat pipe, and coupled to hot sources in the lower part of the heat pipe, in a configuration known as a 'Heat Spreader'. figure 4 represents a general cross-section of the profiled body according to an embodiment, along the section line IV illustrated in the figure 7 . There Figure 5 represents a longitudinal section of the profiled body. figure 6 shows a cross-section of the heat pipe in the vicinity of the circumferential transfer channel, along section line VI illustrated in the figure 7 . There figure 7 represents a longitudinal section of the heat pipe at the location of the circumferential transfer channel. figure 8 shows a cross-section of the heat pipe at the location of the circumferential transfer channel, along section line VIII illustrated in the figure 7 . There figure 9represents a longitudinal half-section of the heat pipe at the location of the circumferential transfer channel. figure 10 is analogous to the figure 7 and represents, in one embodiment, a longitudinal section of the heat pipe at the location of the circumferential transfer channel. figure 11 shows a cross-section of the heat pipe, along section line XI illustrated in the figure 12 . There figure 12 represents a longitudinal section of the heat pipe near one end with an attached plug, along section line XII illustrated in the figure 11 . There figure 13 declined according to the figures 13A, 13B, 13C represents various shapes of the meniscus of the liquid phase of the working fluid inside a longitudinal channel. figure 14 declined according to the figures 14A,14B represents various shapes of the meniscus of the liquid phase of the working fluid inside the circumferential transfer channel. figure 15In one embodiment, it represents a longitudinal section of the heat pipe near one end, with an attached plug. figure 16 represents a cross-section of the profiled body according to a second embodiment. figure 17 illustrates in more detail an example of the geometry of the longitudinal canal and the low walls that border it. figure 18 illustrates the general path of a heat pipe in which the invention can be implemented. figure 19 represents a longitudinal half-section of the heat pipe near a right-angle connection with two circumferential transfer channels. figure 20 represents a longitudinal half-section of the heat pipe in the vicinity of a cross-connection with 4 circumferential transfer channels. Detailed description

[0038] In the various figures, the same references designate identical or similar elements. For reasons of clarity of the presentation, certain elements are not necessarily represented to scale.

[0039] On the figure 1 , a heat pipe is shown 1 which extracts calories from a hot source 81 and rejects them towards a cold source 82. The hot spring 81 is in contact with the heat pipe at a portion of the evaporation line 71. The cold spring 82 is in contact with the heat pipe at a condensation section 72.

[0040] The heat pipe 1 presents itself as an elongated device closed at one end 11 by a closing element 50, and at a second extremity 12 by a second closing element 50.

[0041] On the figure 2 ,Another example is illustrated where the heat pipe receives calories in an intermediate portion and releases calories in two end portions.

[0042] On the figure 3 , Another example is shown where the heat pipe receives heat from one side of the heat pipe axis (from below in the example shown) and rejects heat from the other side of the heat pipe axis (from above in the example shown). This is a configuration known in the industry as a "Heat Spreader".

[0043] The heat pipe 1 is generally understood to be a central axial canal 15 in which working fluid moves in the form of vapor, and longitudinal grooves extending axially and around the central axial channel. As illustrated in Figures 4 and 5 , the longitudinal grooves, also called longitudinal channels 3are designed to advance the working fluid in liquid form in a direction opposite to that of the steam.

[0044] The heat pipe 1 This type of heat pipe is configured for use in low or zero gravity. For example, this type of heat pipe is used in spacecraft and equipment sent into space. In particular, this type of heat pipe is used in communication satellites, surveillance satellites, and satellites with all kinds of other functions. Heat pipe 1 can be used in total weightlessness or in a low gravity environment, for example, on the surface of a celestial body like the Moon or Mars. Heat pipe 1 can be used with zero or very low external pressure. Basic profile

[0045] The heat pipe 1 includes a streamlined body 10obtained by extrusion. Additional operations can be carried out, as will be seen later. However, the extrusion operation is the main manufacturing operation. Using a press, an aluminum alloy is pushed through a die with the desired shapes to obtain the profiled body at the die's exit.

[0046] In the example illustrated in figures 4 to 11 , The profiled body forms a hollow body which delimits an interior space hermetically isolated from the external environment, and which will be used to contain working fluid.

[0047] The profiled body has a cross-section which, after extrusion, extends identically along the longitudinal axis noted X. The profiled body can then be bent, so that the finished heat pipe is not necessarily straight.

[0048] Generally speaking, the streamlined body 10extends along a longitudinal path PX. The longitudinal path PX can be straight or curved.

[0049] The length of the route PX can be between 0.5 meters and 10 meters.

[0050] The streamlined body 10 includes a peripheral tubular wall 75, from which two feet extend radially outwards 16,17 diametrically opposed. These feet each end in a support surface adapted to exchange heat with the cold or hot source. 82, 81.

[0051] In another configuration, there could be only one foot and one support plane for thermal coupling, a foot designed to integrate integration or mechanical functions, or no foot at all.

[0052] In another configuration, it could have four interface planes, and in a particular case the outer boundary of the body could be substantially square or totally cylindrical.

[0053] In yet another configuration, the thermal coupling elements could be separate and added, as illustrated in the figure 16 . In this case, the profile is generally of revolution around the X axis, with inside a repetition of the pattern [groove + wall] in the circumferential direction.

[0054] The streamlined body comprises a plurality of longitudinal channels 3. In practice, longitudinal channels are made like longitudinal grooves.

[0055] Each of these longitudinal channels has a section delimited by a bottom 76 formed by a peripheral tubular wall 75 of the streamlined body, and laterally by two longitudinal walls 2which extend radially inwards from the peripheral tubular wall.

[0056] The longitudinal canals surround the central axial canal 15 conveying steam. The longitudinal channels 3 They are generally open towards the axial canal.

[0057] In the illustrated example, we have sixteen longitudinal walls 2 and sixteen longitudinal canals 3. Generally speaking, the number of longitudinal channels is between 6 and 48.

[0058] The longitudinal canals 3 are arranged annularly around the axis. However, non-circular arrangements are also possible.

[0059] The peripheral tubular wall 75 presents a primitive outer diameter D0. D0 can be between 3 millimeters and 50 millimeters.

[0060] The diameter D1represents the internal dimension of the peripheral tubular wall 75, In other words, the diameter measured at the bottom of the grooves.

[0061] The diameter D2 represents the internal dimension of the axial channel, in other words the diameter of the circumscribed circle passing through the top 77 of the walls.

[0062] We note that all along the profiled body, the interior space is perfectly hermetically sealed from the external environment, because the profile is monobloc and made of extruded material, it surrounds the interior space with continuous material, without any openings.

[0063] Therefore, the sealing issue must be addressed solely at the longitudinal ends. 11, 12. We will see later the case of butt joints between profiles.

[0064] The working fluid can be ammonia, propylene, methanol, or any other medium exhibiting a liquid-vapor equilibrium under saturation conditions at the operating pressures defined by the temperature. A predetermined quantity of working fluid is introduced through one of the end elements equipped with a sealable filling port. The pressure within the heat pipe can range from 0.1 bar to several tens of bars.

[0065] The predetermined quantity of working fluid is defined to preferably have a limited excess of liquid on the cold / condenser side, i.e. the grooves are totally filled and, if necessary, fill the end of the axial channel, cold side.

[0066] It should be noted that the section of the longitudinal canals 3 can take any suitable form, the background 76Since the walls are not necessarily flat, they are not necessarily straight. In a preferred example, the cross-section of the longitudinal channels has a general concavity. In a particular example, the cross-section of the longitudinal channels may generally be an arc of a circle or an oval arc, or even a teardrop shape open towards the axial channel. 15. In the example illustrated in the figures, the section appears as a trapezoidal section. Circumferential passage / channel

[0067] Advantageously, at least one circumferential transfer channel is provided 6, arranged transversely to the local axial direction. The circumferential transfer channel 6 is in first position P1 along the longitudinal route PX.

[0068] We will look at several possibilities for this position below. P1 along the longitudinal route PX.

[0069] The circumferential transfer channel6 It provides fluid communication between all the longitudinal channels. More generally, the circumferential transfer channel 6 connects all or part of the plurality of longitudinal channels.

[0070] The circumferential transfer channel 6 It generally presents itself as an annular passage. In practice, it often presents itself as an annular groove, which forms a complete ring (360°) without excluding a smaller angular opening.

[0071] By referring to figures 7 , 10 And 17 We notice that the longitudinal walls 2 are interrupted at the point of the circumferential canal 6. The material from the low walls was removed to a depth H6. Along the X-axis, the circumferential transfer channel 6 presents an axial length L6 .

[0072] Axial length L6the circumferential canal can be, as in the illustrated example, greater than the height H2 grooves.

[0073] In other configurations, the axial length L6 the circumferential canal may be less than the height H2 grooves.

[0074] In the example shown, part of the low wall has not been removed (this corresponds to the remaining height). H7 = H2 - H6).

[0075] For example, H6 can be between 50% and 100% of the height H2. For example, H6 can be between 70% and 100% of the height H2.

[0076] In other configurations, we could remove the entire height of the low wall (so H7=0).

[0077] In practice, a retaining wall footing remains at a residual height H7, ranging from 0% to 50% of the wall height H2. Maintaining this footing allows for the preservation of longitudinal contact lines to channel the liquid by capillary action, despite the presence of the circumferential transfer channel.

[0078] It is noted that several circumferential transfer channels can be provided, arranged one after the other in the longitudinal direction. X. One could envision creating such a closely spaced succession of small longitudinal transverse channels (L6 little).

[0079] It is noted that there is no porous layer, porous mass, or porous coating in the circumferential transfer channel(s), either locally or generally along the length of the heat pipe. The proposed heat pipes are free of capillary porous material intended to ensure capillary pumping and are therefore easy to manufacture. Cover ring

[0080] According to an advantageous option, the circumferential transfer channel 6 is delimited radially inwards by a cover ring 4. The cover ring 4 is interposed between the circumferential transfer channel and the axial channel. The cover ring 4 closes the circumferential transfer channel 6 radially towards the axis X.

[0081] The cover ring 4 generally appears as a tubular body 40, also known as a sleeve.

[0082] The cover ring 4 presents an axial length L5 The axial length L5 In practice, the cover ring is chosen to be slightly larger than the axial length. L6 of the circumferential canal.

[0083] Radial thickness E5 of the cover ring, at the level of the circumferential transfer channel is between 0.1 millimeter and 1 millimeter.

[0084] In the operating position, the internal diameter of the ring is noted D4.

[0085] The external diameter of the ring at the circumferential channel is noted D5.

[0086] The cover ring 4 can be made of a deformable material, either in the elastic or plastic range, so that it can be positioned to radially cover and close the circumferential channel 6.

[0087] Depending on the elastic deformation option, the ring is constrained radially inwards and then inserted by threading into the axial channel and once it reaches the correct axial position (target position), the elastic constraint is released, which leads to expansion and final positioning.

[0088] Depending on the plastic deformation option, an initial ring diameter slightly smaller than D2, Then the ring is inserted by threading it into the axial channel, and once it reaches the correct axial position (target position), radial expansion is induced by introducing a deformable tool. The cover ring then presses against the walls or the supports / flat surfaces designed for this purpose.

[0089] To receive the cover ring in the circumferential channel area, a first bearing area is prepared B1 to receive a first longitudinal end 41of the cover ring 4 and a second range zone B2 to receive a second longitudinal end 42 of the cover ring.

[0090] According to a first solution, illustrated with figures 7 And 9 , the cover ring 4 may include a central thickness 45 forming a radially external shoulder 47. The central thickness 45 is received between the low walls on stopping faces 44 at the location of the first and second range zones.

[0091] In this configuration, we observe that D4 < D2 < D5.

[0092] According to a second solution, illustrated in the figure 10 , the cover ring has a constant thickness E4 and the first and second span zones B1, B2 are formed as flat surfaces 14set back from the top of the low walls.

[0093] We note that in this case, the diameter D4 is greater than D2, i.e., the ring is radially recessed from the apex 77 low walls.

[0094] The flat surfaces 14 are obtained by removing material.

[0095] The cover ring forms an additional contact line which increases capillary pressure at the circumferential canal 6. Thus, the capillary pressure at the level of the circumferential canal 6 is greater than the capillary pressure along the longitudinal channels 3. The ring allows total recovery of the hydraulic section at the level of the circumferential channel to ensure continuity of liquid flow. Cork

[0096] In the case of a standard heat pipe end, there are closure elements. 50which simply close the profiled body. The present invention, however, provides for the clever use of the closing elements.

[0097] According to one embodiment, the circumferential channel is formed in an end plug 5 fixed to one end of the profiled body.

[0098] According to a first solution for the plug, illustrated in the figure 12 , the cap includes an inner sleeve 51 and a closing disc 52. The disc is then welded / sealed onto the end of the profiled body. 10 at the level of a joint 53 Airtight and securely fixed. The sealing disc 52 is thick enough to withstand internal pressure. However, the inner sleeve 51 does not support any substantial stress, and it is sufficient that the axial length L65 the sleeve length must be greater than the axial length L6of the circumferential canal, to emerge at the summits 77 2 low walls.

[0099] The circumferential canal 6 is obtained by removing material from the end portions of the walls. This machining is relatively standard; it simply requires inserting a milling cutter of the prescribed diameter axially into the end portion of the body 10.

[0100] According to a second solution for the plug illustrated at the figure 15 , the cap includes an inner sleeve 51. The inner sleeve 51 may be distinct from the closing disc 52 or manufactured according to a one-piece design. When it is separate, the inner sleeve 51 is received in a circular housing 57 from the bottom of the closing disc, and comes in the form of an easy-to-obtain part: a simple tubular sleeve.

[0101] Here too, a watertight seal is planned. 53which connects the outer ferrule 54 the cork 5 to the streamlined body 10.

[0102] Note that here too the low walls 2 Longitudinal sections are interrupted at the circumferential canal. The outer limit of the circumferential canal is formed by a thickness 56 of the plug protruding radially inwards. Functioning and other features

[0103] In a weightless situation, the forces of gravity are negligible compared to the forces generated by capillary action. Thus, the physical phenomenon of capillary action is predominant with regard to the forces and pressures applied to the different parts of the liquid present in the heat pipe.

[0104] The first position P1 for the circumferential transfer channel is chosen in the vicinity of an evaporation portion 71of the heat pipe coupled to a hot source. The circumferential transfer channel is filled with liquid and the pressure differences of the different grooves are equalized at this point.

[0105] Menisci M form in the longitudinal channels; they are more deeply hollowed as the pressure difference is greater along the length of the groove, particularly in the longitudinal direction, between the cold sources corresponding to the lowest pressures and the hot sources corresponding to the highest pressures.

[0106] Thus at the figure 13A , The meniscus is almost flat. At the figure 13B , The meniscus is more deeply torn. At the figure 13C the meniscus is even more torn.

[0107] A meniscus forms in the circumferential transfer channel, allowing fluid to move in a circumferential direction and to pass from one longitudinal channel to another.

[0108] At the time of priming, as illustrated in the figure 14A , The ring, as well as the bottom of the longitudinal canal, initiates a meniscus. figure 14B illustrates the established regime where the entire volume of the circumferential transfer channel is filled with fluid.

[0109] In other words, the meniscus forms in the circumferential channel only in transient conditions, and in steady state, it is the menisci of the longitudinal channels, deeper downstream than upstream, that generate the flow in the circumferential groove.

[0110] Thus, the recirculation groove is designed to have a higher capillary pumping than the longitudinal groove to prime itself with liquid correctly.

[0111] In reference to the figure 16 , the canal C1The channel most subjected to heat receives the most heat via a short conductive path, and it is here that the vaporization rate is highest. The neighboring channels C2 and CG also participate in vaporization, but slightly less. The more distant channels C2, CG, and subsequent channels contribute even less to vaporization, depending on the intensity of the heat flux, until the furthest channels cease to participate at all once all the incoming heat flux has been vaporized. Advantageously, the presence of a circumferential transfer channel near the heat source allows liquid that did not reach C1 along its length to flow to channel C1. In other words, the neighboring channels supply liquid to the first channel, C1.

[0112] Not only direct or indirect neighbors, but all other channels can participate in the supply of liquid to avoid local drying up at the most stressed point.

[0113] Thus, in a case of top loading as illustrated in the figure 16 the canals CG,C1,C2 will be fed by all other channels, i.e. C3, C4, C5, C6, C7, C8, C9, CA, CB, CC, CD, CE, CF.

[0114] Put another way, the circumferential transfer channel has a pooling and sharing function for the liquid supply. It supplies the most demanding longitudinal channel 3 with liquid from the other channels. Various other points

[0115] The closing ring promotes the supply of liquid to the circumferential transfer channel.

[0116] But the ring also promotes straight passage in a particular longitudinal channel.

[0117] If the closing ring is slightly recessed from the top of the walls, it has a favorable effect on the straight passage of liquid in a longitudinal channel.

[0118] In addition, one or more other circumferential channels are planned along the path, at distinct axial positions (P2,P3,P4) different from the first position.

[0119] As illustrated the figure 18 , the PX path may include one or more curves 18, and where appropriate may even include one or more right angles 19.

[0120] There figure 19This represents a longitudinal half-section of the heat pipe near a right-angle connection with two circumferential transfer channels. In the illustrated case, two profiled bodies cut at 45° have been joined to form a right angle at this point; there is an imbalance in meniscus formation between the well-irrigated outer grooves and the rather dry inner grooves. The presence of one or two circumferential transfer channels near the angle helps to equalize the pressures between the different longitudinal channels.

[0121] There figure 20 This represents a longitudinal half-section of the heat pipe near a cross-connect with four circumferential transfer channels. This configuration is an extrapolation of the previous case illustrated in the diagram. figure 19with four profiles joined at a cross intersection. The presence of the four circumferential channels near the intersection allows the pressures to be equalized between the different longitudinal channels.

[0122] At the intersections, external fixing sleeves are provided, ensuring mechanical cohesion and sealing, generally obtained by welding.

[0123] Regarding dimensional aspects, one can choose L6 being between 0.1 D0 and 0.5 D0. We also observe D0 > D1 > D2. Regarding the height of the walls, we can choose for H2 a value between 0.05 D1 and 0.2 D1.

Claims

1. A heat pipe (1) configured for being used in low or zero gravity comprising a profiled body (10) generally obtained by extrusion, where said profiled body extends along a longitudinal path (PX), and where said profiled body forms a hollow body closed at at least two ends by closing elements, thereby forming an interior space hermetically isolated from the outside environment, and filled with a predefined volume of diphasic working fluid, said profiled body comprising a plurality of longitudinal channels (3), where each longitudinal channel has a section delimited by a bottom (76) formed by one tubular peripheral wall (75) of the profiled body, and laterally by two longitudinal dividers (2) which extend radially inwards from the peripheral tubular wall, where the longitudinal channels surround an axial channel (15), and where the longitudinal channels are open towards the axial channel, characterized in that there is provided, at at least one first position (P1) along the longitudinal path, a circumferential transfer channel (6), arranged transversely to the local axial direction (X) and providing mutual fluid connection between all or part of the plurality of longitudinal channels, and in that the longitudinal dividers are interrupted, partially or completely, in the area of the circumferential channel.

2. The heat pipe according to claim 1, wherein the circumferential transfer channel is radially delimited on the inside by a covering ring (4), where the covering ring is interposed between the circumferential transfer channel and the axial channel (15).

3. The heat pipe according to claim 2, wherein the circumferential channel may be arranged at an intermediate position, where the dividers (2) are interrupted over a predefined length (L6) in that area, with preferably the material of the dividers (2) being removed over a height (H6) comprised between 50% and 100% of the height (H2) of the dividers.

4. The heat pipe according to claim 3, wherein the dividers comprise a first bearing zone (B1) for receiving a first longitudinal end (41) of the covering ring (4) and a second-bearing zone (B2) for receiving a second longitudinal end (42) of the covering ring.

5. The heat pipe according to claim 4, wherein the covering ring comprises a central excess thickness (45) forming a radially outward shoulder received between the dividers in the area of the first and second bearing zones (B1, B2).

6. The heat pipe according to claim 4, wherein the covering ring (4) has a constant thickness and the first and second bearing zones are formed as flat areas (14) recessed from the summit of the dividers.

7. The heat pipe according to claim 1, wherein the first position (P1) is selected near an evaporation portion (71) of the heat pipe coupled to a heat source (81).

8. The heat pipe according to claim 1, wherein the first position (P1) is an intermediate position along the longitudinal path (PX).

9. The heat pipe according to claim 1, wherein the first position is an end position (P1) on the longitudinal path.

10. The heat pipe according to claim 1, wherein the circumferential channel is formed in an end cap (5) fixed to an end of the profiled body.

11. The heat pipe according to claim 1, wherein one or more other circumferential channels are provided on the path at distinct axial positions (P2, P3, P4) different from the first position.

12. The heat pipe according to claim 1, wherein a plurality of circumferential channels are provided along the length, at uniformly spaced axial positions (P2, P3, P4), with a predetermined step, for example every 300 mm.

13. The heat pipe according to claim 1, comprising one or more intersections with two circumferential channels arranged on either side of each intersection.

14. The heat pipe according to claim 1 formed like a three-dimensional object.