Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
  • F28D15/00—Heat-exchange apparatus with the intermediate heat-transfer medium in closed tubes passing into or through the conduit walls ; Heat-exchange apparatus employing intermediate heat-transfer medium or bodies
  • F28D15/02—Heat-exchange apparatus with the intermediate heat-transfer medium in closed tubes passing into or through the conduit walls ; Heat-exchange apparatus employing intermediate heat-transfer medium or bodies in which the medium condenses and evaporates, e.g. heat pipes
  • F28D15/0233—Heat-exchange apparatus with the intermediate heat-transfer medium in closed tubes passing into or through the conduit walls ; Heat-exchange apparatus employing intermediate heat-transfer medium or bodies in which the medium condenses and evaporates, e.g. heat pipes the conduits having a particular shape, e.g. non-circular cross-section, annular

Definitions

• the present invention relates to the general technical field of heat exchangers, in particular for the purpose of removing heat from an element to be cooled, such as an electronic component.
• the present invention relates to the technical field of two-phase thermal diffusers heat pipe type.
• thermal diffusers can be used for many applications such as applications in aeronautics, railways, aerospace, power electronics, etc.
• Heat exchangers are systems that collect heat from one environment and redistribute it to another. There are different categories of heat exchangers for transporting heat from a hot source (electronic component, for example) to a cold source (water condenser, for example). When the surface of the cold source is significantly larger than the surface of the hot source, the heat transfer includes a heat diffusion component, and the heat exchanger is called a "heat diffuser".
• the flat solid diffuser which generally consists of a block of material with a high thermal conductivity such as a metal; such a diffuser operates by simple conduction of heat in the block of material,
• the capillary heat pipe which generally consists of a housing containing a liquid and a capillary structure in thermal contact with the inner walls of the housing, the liquid being located mainly in the capillary structure and flowing from the cold source to the hot source, the steam produced at the hot source occupying the entire vapor space and condensing at the cold source,
• thermosiphon which consists of a housing including a two-phase fluid flowing under the effect of gravity forces, the gravity being the engine of the return of the condensed liquid in the evaporation zone.
• the flat solid diffuser is heavy and inefficient with high flux density
• the capillary heat pipe is complex, expensive, and sensitive to freezing (the capillary structure may degrade when the liquid it contains solidifies), and its thermal performance degrades at high flux densities,
• thermosiphon - by the use of gravity forces for the circulation of the fluid - is sensitive to inclinations and very strongly constrained vis-à-vis the positioning of hot and cold sources.
• WO 201 1/149216 describes an oscillating heat pipe composed of several loops interconnected to each other. The loops are of capillary dimensions. They are filled with a heat transfer fluid in the form of a succession of vapor bubbles and liquid plugs. When the oscillating heat pipe is heated at one end and cooled at the other, the resulting temperature differences generate both temporal and spatial pressure fluctuations, which are themselves associated with the generation and growth of vapor bubbles in the water. evaporator and their implosion in the condenser.
• JP H10 185468, US 6,679,316 and US 5,642,776 disclose other examples of oscillating heat pipes having the same disadvantages.
• An object of the present invention is to provide a thermal diffuser to meet the aforementioned constraints, and more specifically a thermal diffuser:
• the hot springs can be positioned in different zones, - not very sensitive to inclination
• the invention proposes a thermal diffusion device with heat pipe effect comprising a coolant and a housing, the housing having a bottom wall forming a bottom, an upper wall opposite the bottom wall and four side walls between the lower walls and upper side walls consisting of:
• a first longitudinal lateral wall being intended to receive a hot source
• the walls of the housing (2) being interconnected so as to constitute a sealed reservoir for the coolant
• the distance between the longitudinal side walls is between 1 ⁇ 2 and 2 times the capillary length of the coolant
• the distance between the transverse lateral walls is greater than 10 times the capillary length of the coolant
• the amount of heat transfer fluid contained in the device is between 25 and 80% of the total volume of the housing.
• the distance between the longitudinal side walls is between 1 ⁇ 2 and 2 times the capillary length of the coolant
• the distance between the lateral transverse walls is greater than 10 times the capillary length of the coolant
• the fact of constraining the fluid to a single dimension makes it possible to establish a flow of the two-dimensional two-phase fluid in the enclosure, which forms two convection cells. around the hot source (s) (upward movement of the bubbles above the hot source and return of the descending fluid around the hot source, and in particular along the two transverse lateral walls).
• Preferred but non-limiting aspects of the device according to the invention are the following:
• the device may be devoid of capillary structure
• the first longitudinal side wall comprises an evaporation zone intended to receive at least one hot source, the area of the evaporation zone being less than 40% of the total area of the first longitudinal lateral wall;
• the evaporation zone intended to receive the hot source can be positioned on the first wall at a non-zero distance from the side walls to allow a two-dimensional circulation of the coolant around the hot source,
• the position of the evaporation zone on the first longitudinal lateral wall may be such that:
• the distance between the evaporation zone and each transverse lateral wall is greater than or equal to one fifth of the length of the first longitudinal lateral wall
• the distance between the evaporation zone and the upper wall is greater than or equal to one third of the height of the first longitudinal side wall
• the outer face of the first longitudinal lateral wall may comprise a positioning mark for defining the position of the evaporation zone
• the device may comprise spacers between the inner faces of the longitudinal side walls of the housing, each spacer being intended to cooperate with respective fastening means;
• the internal faces of the longitudinal lateral walls may comprise surface texturing
• the surface texturing may consist of splines formed on the inner faces of the longitudinal side walls, the grooves extending between the lower and upper walls of the housing;
• the heat transfer fluid may be water.
• FIGS. 1 and 2 illustrate an embodiment of a thermal diffuser according to the invention
• the device comprises a heat transfer fluid 1 and a housing 2 for containing the coolant 1.
• the heat transfer fluid 1 makes it possible to transport the heat produced by the element to be cooled (not shown).
• the heat transfer fluid 1 is contained in the housing 2, the internal volume of which constitutes a sealed enclosure for the coolant.
• the vacuum is carried out in the housing 2 prior to the introduction of the coolant 1.
• the heat transfer fluid is then in a liquid-vapor equilibrium state in the absence of heat transfer.
• the amount of heat transfer fluid 1 contained in the housing 2 may be between 25% and 80% of the total volume of the housing 2. It depends on the intended application and the compromise adopted between the thermal performance of the system and the other constraints to be taken such as the desired inclination or degree of freedom on the placement of the hot springs. For example for certain applications, the amount of fluid can be between 30% and 70%, or between 40% and 60%, or between 45% and 55%, or even substantially equal to 50% of the total volume of the housing. As will become more clearly apparent in the rest of the text, the combination of this characteristic with specificities relating to the dimensioning of the housing 2 enables the thermal diffusion device to respond to the aforementioned constraints concerning the efficiency of the device with a high flux density, its sensitivity to the inclination, its simplicity, etc.
• the material constituting the coolant 1 may vary depending on the desired operating temperature level.
• the heat transfer fluid 1 can be, for example, an oil, an alcohol (such as methanol, ethanol or glycol), a compound organic (such as acetone, ammonia), a mixture, a nanofluid, a liquid metal, or any type of coolant known to those skilled in the art.
• the coolant 1 is deionized water.
• the use of water as heat transfer fluid 1 has many advantages, and in particular:
• the housing 2 comprises walls consisting for example of sheets of thermally conductive material such as metal (for example copper or aluminum).
• thermally conductive material such as metal (for example copper or aluminum).
• the choice of material used to make the walls of the housing 2 depends in particular on the constraints of manufacture and use, as well as the type of heat transfer fluid chosen, the fluid / material pair of the housing to be chemically compatible.
• Accommodation 2 comprises:
• the walls 21-26 of the housing 2 are connected to each other so as to constitute a sealed reservoir containing the coolant 1.
• the heat transfer fluid is naturally distributed in the volume constituted by the walls of the housing. This limits the risk of local overheating when using the device, unlike existing heat pipes comprising a serpentine tube (or channels) for containing the heat transfer fluid.
• side wall “top wall” and “bottom wall” will be used with reference to a rectangular parallelepiped.
• ⁇ 'Lower wall' means a horizontal wall of a rectangular parallelepiped nearest the ground
• upper wall means a horizontal wall of a rectangular parallelepiped opposite to the lower wall
• face / side wall means a face / vertical wall of a rectangular parallelepiped extending in a plane perpendicular to the bottom wall
• faces / longitudinal walls means the vertical faces / walls of a rectangular parallelepiped of which at least one dimension is greater than the dimensions of the other faces / side walls,
• faces / transverse walls means vertical faces / walls extending perpendicular to the longitudinal faces / walls.
• the housing 2 is devoid of capillary structure. This reduces the risk of degradation of the thermal diffusion device in case of freezing of the heat transfer fluid 1, for example during a prolonged deactivation of the device in a cold environment.
• the absence of a capillary structure also makes it possible to improve the thermal performance and to reduce the cost and the manufacturing constraints compared with the usual heat pipe.
• the longitudinal side walls 25, 26 constitute the walls of larger dimensions of the thermal diffusion device. More specifically, the area of a longitudinal side wall is greater than the area of each of the other walls of the housing 2.
• Accommodation 2 comprises:
• a first longitudinal lateral wall 25 A second longitudinal lateral wall extending parallel to the first longitudinal lateral wall.
• the outer face of the first longitudinal side wall 25 is intended to be in thermal contact with one (or more) source (s) hot (s).
• the outer face of the second longitudinal side wall 26 is in turn intended to be in thermal contact with one (or more) source (s) cold (s).
• the hot and cold sources may be disposed on the same longitudinal sidewall, as long as certain rules, described below, are respected.
• the distance “e” between the longitudinal side walls (25, 26) is advantageously between 1 ⁇ 2 and 2 times the capillary length of the coolant (1).
• “Capillary length” is a length scale characteristic of an interface (between two fluids) subjected to capillary forces and gravitational forces: for example, when gravitational effects dominate, a bubble or a drop is flattened by the gravity and its radius is large in front of the capillary length. This characteristic length is an intrinsic property and therefore depends on the coolant chosen for the thermal diffusion device as well as the operating temperature; in the case of water at 20 ° C, the capillary length is 2.7 millimeters.
• the distance e between the longitudinal side walls 25, 26 is between 1 ⁇ 2 and 2 times the capillary length of the coolant 1 makes it possible to take advantage of the confined boiling phenomena.
• the main difference between a boil in a confined environment and in an unconfined environment is that for low thermal flows, the wall overheating is less important in a confined environment than in an unconfined environment. This reflects the fact that a better heat transfer coefficient is obtained. The more the space is confined, the greater the exchange coefficient becomes greater than that reached during boiling in an unconfined environment.
• a quantity (Qf) of heat transfer fluid comprised between 25% and 80% of the total volume (Vtot) of the housing
• the distance L between the transverse lateral walls is in turn chosen to be much greater than the capillary length of the coolant (in particular 10, 100, 1000 times greater). This makes it possible not to confine the coolant between the transverse lateral walls.
• the confinement of the coolant is made in one dimension, unlike the heat pipes of the oscillating type in which the heat transfer fluid is confined in two dimensions.
• the device comprises spacers 36 between the first and second longitudinal side walls 25, 26. These spacers 36 are fixed in different positions of the respective surfaces of the first and second longitudinal side walls 25, 26.
• the spacers 36 may be attached to the first and second longitudinal side walls 25, 26 by welding, brazing or gluing.
• spacers 36 stiffens the housing 2 so as to maintain constant the distance between the first and second longitudinal side walls 25, 26.
• the device may also comprise fastening means 35 - such as bolts or screws - to allow the attachment of one (or more) system (s) outside (s) on the diffuser, such as fins or a electronic card.
• fastening means 35 - such as bolts or screws - to allow the attachment of one (or more) system (s) outside (s) on the diffuser, such as fins or a electronic card.
• One (or more) spacer (s) 36 may (advantageously) be arranged (s) so as to cooperate with a respective fastening means.
• spacers 36 may (advantageously) be arranged (s) so as to cooperate with a respective fastening means.
• blind holes are formed in the spacers 36 through the first longitudinal side wall to form threaded barrels - four in number.
• Each was intended to receive the thread of a respective fastening means to allow the attachment of a hot or cold source.
• the spacers and fastening means 35, 36 of the first and second longitudinal side walls 25, 26 constitute thermal bridges which make it possible to heat up the coolant 1 more quickly, for example in the event of the latter being freezing (when the device thermal diffusion is deactivated and that the outside temperature is lower than the solidification temperature of the coolant).
• the presence of fixing means and spacers 35, 36 between the longitudinal side walls 25, 26 reduces the priming time of the device.
• primeing duration is meant the time interval between the moment when the heat dissipated by the element to be cooled is applied to the thermal diffusion device, and the moment when the coolant 1 reaches a regime steady flow.
• one of the two inner faces or the two inner faces of the longitudinal side walls 25, 26 are textured.
• the internal face of the second longitudinal sidewall 26 makes it possible to promote the condensation phenomenon of the coolant 1
• the inner face of the first longitudinal lateral wall makes it possible to promote the phenomenon of evaporation of the coolant 1 by promoting nucleation effects.
• the surface texturing of the internal faces of the longitudinal lateral walls 25, 26 consists of a vertical grooving made on said inner faces, said grooves extending between the lower and upper walls 21, 22 of the device.
• the outer face of the first longitudinal side wall 25 is intended to be in thermal contact with one (or more) source (s) hot (s).
• the coolant 1 is intended to be vaporized (i.e., from the liquid state to the vapor state) to allow the hot springs to cool.
• the area of the evaporation zone is less than 40% of the total area of the first longitudinal lateral wall 25.
• the evaporation zone 32 and each transverse lateral wall 23, 24 is equal to one fifth of the length (L) of the first longitudinal lateral wall ( L / 5), the distance between
• the evaporation zone 32 and the upper wall 22 is equal to one third of the height (H) of the first longitudinal lateral wall ( H ), and the distance between
• the evaporation zone 32 and the bottom wall 21 are zero.
• the distance between the evaporation zone 32 and each transverse side wall 23, 24 and the distance between the evaporation zone 32 and the upper wall 22 depend on the intended application: they are a function of the quantity of heat transfer fluid 1 chosen as well as surfaces necessary for condensation and recirculation of the fluid.
• At least one hot source is in thermal contact with a region of the outer face of the first longitudinal side wall 25 for which the opposite inner face is covered with heat transfer fluid 1 (advantageously so that the distance between the lower part of the corresponding region on the outer face of the first longitudinal side wall 25 and the bottom wall 21 is zero).
• the outer face of the first longitudinal side wall 25 may comprise a positioning mark to indicate the location of (and delimit) the evaporation zone. This facilitates the positioning of hot springs by the user.
• the positioning mark may consist, for example, of an imprint drawn or engraved on the external face of the first longitudinal lateral wall 25. 1.2.1.4. Cold source positioning zone
• the outer face of the second longitudinal side wall 26 is intended to be in thermal contact with one (or more) source (s) cold (s).
• the condensation zone In the cold source positioning zone - the so-called “condensing zone” - the coolant is intended to be condensed (i.e. passage from the vapor state to the liquid state).
• the condensation zone may cover all or part of the surface of the external face of the second longitudinal lateral wall 26.
• the condensation zone and the evaporation zone may extend on the same longitudinal sidewall.
• the condensation zone extends above the evaporation zone. More specifically, the condensation zone can be arranged so that the distance between:
• the zone of condensation and each transverse lateral wall 23, 24 is zero, the distance between The condensation zone and the upper wall 22 are zero, and the distance between
• the transverse side walls 23, 24 extend perpendicular to the longitudinal side walls 25, 26.
• the length of each of these transverse lateral walls 23, 24 is equal to the height of the thermal diffusion device (which depends on the intended application) .
• the width of each of the transverse side walls is equal to the sum of the thicknesses of the longitudinal side walls added to the distance "e" between the longitudinal side walls 25, 26.
• each transverse lateral wall 23, 24 is between:
• the housing comprises a quantity of heat transfer fluid substantially equal to 50% of its total volume, so that the lower half of the inner faces of the longitudinal and transverse side walls are immersed under the heat transfer fluid.
• the hot springs are disposed in the evaporation zone 32 of the first longitudinal lateral wall 25, at least one of the hot springs being in thermal contact with a region of the external face of the first longitudinal lateral wall for which the opposite internal face is covered with heat transfer fluid 1,
• the cold source is in thermal contact with the external face of the second longitudinal lateral wall 26 in the condensation zone. 2.2.
• the heat generated at the hot springs is transmitted to the heat transfer fluid 1 via the first longitudinal side wall 25.
• the texturing of the internal face of the first side wall 25 promotes the evaporation of the coolant 1 by promoting nucleation phenomena.
• vapor bubbles 4 are formed in the coolant (boiling) and back to the surface of said fluid (see Figure 5).
• the evaporation of the coolant 1 in the liquid state absorbs heat. This induces a cooling of the hot source.
• the ascension of the vapor bubbles 4 confined (in one direction) towards the surface of the coolant 1 makes it possible to raise the heat transfer fluid in the liquid state ("pushed" by the bubbles below) so as to wet the zone of evaporation 32 over its entire surface.
• the coolant vapor occupies the upper part of the housing 2. Once in the condensation zone, the heat transfer fluid in vapor form is transformed in liquid (condensation phenomenon), then falls via recirculation zones (corresponding to zones in the housing extending opposite regions of the outer face of the first longitudinal side wall 25 devoid of hot springs) to the lower wall 21 of housing 2 under the effect of gravity.
• Convection cells are formed around the hot source (s): the heat transfer fluid moves over the hot source (s) during its evaporation and then falls around the (or) hot source (s) during condensation.
• the proposed thermal diffusion device is capable of transferring heat from one or more flat heat sources - such as a card or electronic component - to a cold source - such as a radiator.
• Typical dimensions for electronic component cooling applications can be:
• the thermal diffusion device comprises:
• the evaporation and condensation zones may be placed on opposite walls (in particular the longitudinal side walls) or on the same wall.
• the device can be used in a vertical or inclined position (even strongly). Great flexibility is allowed in the positioning of the sources. At least one of the hot springs is located below the filling level of the housing 2 in heat transfer fluid 1 to promote the evaporation thereof. Moreover, the hot springs are preferentially positioned so that:
• the distance between the hot springs and the upper wall 22 of the housing 2 is greater than or equal to one third of the height of the side walls 23-26 of the housing 2, and so that
• the distance between the hot springs and the transverse lateral walls 23, 24 of the housing 2 is greater than or equal to one fifth of the length of the longitudinal side walls 23, 24.

Landscapes

• Engineering & Computer Science (AREA)
• Life Sciences & Earth Sciences (AREA)
• Sustainable Development (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Cooling Or The Like Of Electrical Apparatus (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=58547646

Family Applications (1)

Country Status (3)

Family Cites Families (6)

• 2017
  • 2017-01-06 FR FR1750129A patent/FR3061745A1/fr active Pending
• 2018
  • 2018-01-05 EP EP18700184.7A patent/EP3566014A1/de not_active Withdrawn
  • 2018-01-05 WO PCT/EP2018/050232 patent/WO2018127548A1/fr unknown

Also Published As

Similar Documents

Legal Events