EP4323711A1

EP4323711A1 - Two-phase heat-transfer device with liquid overflow tank

Info

Publication number: EP4323711A1
Application number: EP22814485.3A
Authority: EP
Inventors: Matthieu MARTINELLI; Laura Fourgeaud; Typhaine COQUARD; Christophe Figus
Original assignee: Airbus Defence and Space SAS
Current assignee: Airbus Defence and Space SAS
Priority date: 2021-10-07
Filing date: 2022-10-07
Publication date: 2024-02-21
Anticipated expiration: 2042-10-07
Also published as: EP4323711B1; WO2023057730A1; EP4323711C0

Abstract

Disclosed is a two-phase heat-transfer device, said device comprising a closed cavity comprising at least one evaporation zone (20) subjected to heat exchange with at least one heat source and at least one condensation zone (30) subjected to heat exchange with at least one cold source, the closed cavity containing a two-phase fluid with a liquid-steam balance and comprising at least one channel (13) for circulating the two-phase fluid in the steam phase and at least one main capillary structure (14) suitable for allowing the two-phase fluid to circulate in the liquid phase between the cold source and the heat source, the two-phase device being characterised in that it further comprises at least one additional capillary medium (15) for storing and restoring excess liquid relative to a maximum capacity of liquid contained in the main capillary structure, the additional capillary structure and the main capillary structure being connected to each other so as to ensure capillary continuity for the two-phase fluid in the liquid phase.

Description

Title: Two-phase heat transfer device with excess liquid reservoir

Technical area

The present disclosure falls within the field of two-phase heat transfer devices, containing a saturated two-phase fluid circulating between a cold source and a hot source, and thus making it possible to evacuate the heat generated by the hot source. It finds a particular application in the space field, in particular for the thermal control of equipment of a spacecraft, such as for example a satellite.

Prior technique

A two-phase heat transfer device conventionally comprises a closed cavity containing a two-phase fluid at saturation, a portion of which is in the liquid phase and another in the gas phase. The heat transfer device is in a heat exchange relationship on the one hand with a so-called hot source, and on the other hand with a so-called cold source, relatively colder than the heat source.

[0003] In a two-phase heat transfer device, the volume of fluid in the liquid phase, present in the cavity, varies according to the operating temperature. Thus a surplus of liquid can disturb the operation of the two-phase heat transfer device. Patent application WO2016/058966 entitled flat heat pipe with reservoir function teaches a liquid reservoir arranged at one end of the condensation channels and under a capillary structure.

[0004] However, this type of solution imposes constraints on the design and use of the heat pipe. Part of the surface of the cold plate is in particular used to make thermal contact with the liquid reservoir, which therefore reduces the useful surface available for the condenser and therefore the performance of the heat pipe. Furthermore, the fact of placing the reservoir in thermal contact with the cold plate also represents an additional design constraint which it is desired to overcome.

Summary

The present invention thus aims to provide a two-phase structure, also referred to in English as "two phase heat transport equipment" or TPHTE, more efficient and of simpler design. [0006] A two-phase heat transfer device is thus proposed, comprising a closed cavity comprising at least one evaporation zone in a heat exchange situation with at least one hot source and at least one condensation zone in a heat exchange with at least one cold source, the closed cavity containing a two-phase fluid in the state of liquid-vapor equilibrium and comprising at least one circulation channel for the two-phase fluid in the vapor phase and at least one main capillary structure adapted to allow the circulation of the diphasic fluid in liquid phase between said cold source and said hot source, the diphasic device being characterized in that it also comprises at least one additional capillary medium allowing storage and restitution of an excess of liquid with respect to to a maximum capacity of liquid contained in the main capillary structure, said additional capillary medium and said main capillary structure being connected so as to ensure capillary continuity for the two-phase fluid in the liquid phase.

In some embodiments, said additional medium forming at least one capillary reservoir zone, while the main capillary structure comprises at least one capillary condensation zone and at least one capillary flow zone connected on the one hand to the capillary condensation zone and on the other hand to the evaporator.

[0008] In some embodiments, the reservoir capillary zone has a characteristic capillary dimension less than a characteristic capillary dimension of the condensation capillary zone but greater than or equal to a characteristic capillary dimension of the flow capillary zone to which the zone capillary reservoir is connected.

[0009] In some embodiments, the reservoir capillary zone has a characteristic capillary dimension less than a characteristic capillary dimension of the two-phase fluid circulation channel in the vapor phase but greater than a characteristic capillary dimension of the condensation capillary zone.

[0010] In some embodiments, said reservoir capillary zone is connected directly to the flow zone or respectively to the evaporation zone and has a characteristic capillary dimension greater than a characteristic capillary dimension of the flow zone or respectively the evaporation zone.

[0011] In some embodiments, the main capillary structure has a characteristic capillary dimension which decreases from the condensation zone towards the evaporation zone. [0012] In some embodiments, the additional capillary medium has a minimum characteristic capillary dimension at the level of the connection with the main capillary structure for the circulation of the two-phase fluid in the liquid phase.

[0013] In some embodiments, the additional capillary medium is sized so as to have a filling rate strictly between 0 and 100%, preferably strictly between 5 and 95%, when the diphasic heat transfer device is Operating.

[0014] In embodiments, the volume available for the liquid in the additional capillary medium is between 10 and 40% of the volume available for the liquid in the main capillary structure of the cavity.

[0015] In embodiments, the additional capillary medium is a mesh and/or is formed from a porous material.

The heat transfer device advantageously comprises a liquid reservoir having a capillary structure and which is connected to the main capillary structure for the circulation of liquid between the condenser and the evaporator, the liquid reservoir being connected to the structure main capillary so as to ensure capillary continuity between them allowing liquid continuity to be maintained. This avoids having a surplus of liquid which would disturb or even prevent the operation of the heat transfer device, for example if it were located in a place preventing the circulation of vapor to the cold source, or if it came partially or totally mask a heat exchange surface with the cold source.

[0017] Advantageously, an excess volume of liquid is lodged in the additional capillary medium, thus avoiding a useless and inactive excess volume, which would move according to local pressure variations induced by capillary forces, temperature gradients and hydrodynamic forces and which would disturb the operation of the heat transfer device. For this, the additional capillary medium does not need to be located in thermal contact with the cold source. More generally, constraints on design and use are reduced. The device is suitable for use in a space environment but use on Earth, in the presence of gravity, is also possible. The thermal performance of the heat transfer device relating to its transport capacity or to its heat exchange coefficient is advantageously optimized.

[0018] Also advantageously, thanks to the capillary continuity, in particular by controlling a hierarchy of capillary dimensions between the liquid reservoir and the main capillary structure, it is possible to ensure storage and restitution of diphasic fluid in liquid phase so as to maintain an optimum volume of two-phase fluid in the liquid phase in the main capillary structure.

Brief description of the drawings

[0019] Other characteristics, details and advantages will appear on reading the detailed description below, and on analyzing the appended drawings, in which:

Fig. 1a

[0020] [Fig. 1a] represents a block diagram of a two-phase heat transfer device.

Fig. 1b

[0021] [Fig. 1 b] represents a sectional view of an evaporator of a device of figure 1a.

Fig. 2

[0022] [Fig. 2] is a partial and schematic perspective view of a two-phase heat transfer device according to one embodiment.

Fig. 3

[0023] [Fig. 3] is a perspective sectional view of the device of Figure 2.

Fig. 4

[0024] [Fig. 4] is a front sectional view of a condenser of a two-phase heat transfer device according to one embodiment.

Fig. 5

[0025] [Fig. 5] schematically represents the circulation of the two-phase fluid in a heat transfer device according to one embodiment.

Fig. 6

[0026] [Fig. 6] shows an example of a capillary structure that can form the excess liquid reservoir.

Fig. 7

[0027] [Fig.7] schematically represents another example of a two-phase device in which the additional capillary medium is located in the extension of the condenser.

Fig. 8a [0028] [Fig. 8a] represents an example of a hierarchy of characteristic capillary dimensions of a device when in particular the device has no adiabatic zone and comprises an additional capillary medium forming an additional section of the device, adjacent to the condenser.

Fig. 8b

[0029] [Fig. 8b] represents an example of a hierarchy of capillary dimensions characteristic of a device when in particular the device comprises an adiabatic zone and an additional capillary medium forming an additional section of the device, adjacent to the condenser.

Fig. 8c

[0030] [Fig. 8c] represents an example of a hierarchy of characteristic capillary dimensions of a device when in particular the device comprises an adiabatic zone and an additional capillary medium connected to the condenser and to the adiabatic zone.

Fig. 8d

[0031] [Fig. 8d] represents an example of a hierarchy of capillary dimensions characteristic of a device when in particular the device does not include an adiabatic zone and includes an additional capillary medium connected to the condenser and to the evaporator.

Description of embodiments

With reference to Figures 1a to 5, two examples of a two-phase heat transfer device 1 have been shown. In FIGS. 1a and 1b, the device has a substantially cylindrical shape. In the example shown in Figures 2 to 4, the device has a substantially parallelepipedic shape. The shape of the device is however not limiting and can be adapted according to the constraints of use, in particular according to the relative positions of the hot and cold sources between which the transfer of heat must be implemented.

The two-phase heat transfer device 1 comprises a closed cavity 10 in a sealed manner and delimited by an envelope 11, in which circulates a two-phase fluid at saturation comprising a vapor phase and a liquid phase. The liquid part of the two-phase fluid evaporates in the vicinity of the heat source, and the vapor obtained moves towards the cold source where it liquefies, thus restoring the thermal energy, stored near the hot source, to the cold source. . To allow the circulation of the liquid phase within the cavity, two-phase heat transfer devices comprise for example a particular structure which is shaped to allow liquid flow by capillarity. These structures can take variable forms, such as for example a set of grooves, a porous structure or a lattice. The circulation of the vapor phase is permitted by one or more channels allowing a dissociated flow of the vapor and the liquid.

As shown schematically in Figure 1a, the cavity 10 of the two-phase heat transfer device comprises at least one evaporation zone or evaporator 20, this zone being in a heat exchange situation, typically in thermal contact, with a hot source 2, such as for example equipment to be cooled. At the level of the evaporator 20, the liquid phase of the fluid contained in the cavity evaporates by absorbing the heat provided by the hot source.

The evaporation zone notably comprises a capillary evaporation zone, for example in the form of a capillary structure. The evaporation zone notably comprises at least one capillary structure for the liquid and at least one vapor channel for the vapor.

[0036] In some embodiments, the heat transfer device 1 can be used in a space environment, to cool one or more equipment items of a spacecraft such as a satellite. This equipment can include optical equipment, such as for example a focal plane, telecommunications equipment or other equipment such as for example electrical actuator control equipment.

The heat transfer device 1 also comprises at least one condensation zone or condenser 30, this zone being in a heat exchange situation, typically in thermal contact, with a cold source 3. At the level of the condenser, the phase vapor of the fluid contained in the cavity condenses, thus restoring, to the cold source, the calories absorbed from the hot source. The condenser zone notably comprises a capillary condensation zone, for example in the form of a capillary structure. The condenser zone notably comprises at least one capillary structure for the liquid and at least one vapor channel for the vapor.

In the case where the heat transfer device is used in a space context, the cold source can for example comprise a radiator adapted to evacuate heat to space.

The heat transfer fluid contained in the cavity may for example be in the form of water, ammonia, methane, ethane, propylene, methanol or ethanol, in the state of equilibrium. liquid-gas. In order to allow heat exchange between the two-phase fluid and the hot source on the one hand, and between the two-phase fluid and the cold source on the other hand, the casing 11 is advantageously made, at least at the level of each evaporator and each condenser, in a thermally conductive material, such as for example a metal, or a metal alloy, for example based on aluminium.

In embodiments, and as shown for example in Figure 1a, the heat transfer device 1 may also include an adiabatic zone 12 located between an evaporator 20 and a condenser 30, that is to say a zone where heat transfers between the two-phase fluid present in the cavity and the environment of the heat transfer device are limited. Such a zone can for example be provided in the case where the cold source 3 and the hot source 2 are relatively distant from each other and it is then desired to circulate the diphasic fluid between the two while limiting the transfers. heat with the environment. In this respect, a thermally insulating material can be used to ensure thermal insulation between the two-phase fluid and the environment of the heat transfer device 1, for example directly during the constitution of the envelope of the cavity, at the level of said adiabatic zone or by adding an additional insulating envelope around the adiabatic zone. The adiabatic zone comprises in particular a capillary flow zone, for example in the form of a capillary structure. The adiabatic zone notably comprises at least one capillary structure for the liquid and at least one vapor channel for the vapor.

The closed cavity 10 is shaped to allow the circulation of the two-phase fluid between the evaporator 20 and the condenser 30. In this respect, the closed cavity comprises at least one channel 13 for the circulation of the two-phase fluid in the vapor phase which allows, as represented by the arrows FV in FIG. 1a, to circulate the vapor obtained at the level of the evaporator towards the condenser. The vapor circulation channel or channels 13, or a network formed by these channels, therefore extend over the entire length of the cavity, going from the evaporator to the condenser. In addition, the closed cavity also comprises a main capillary structure 14 adapted to allow the circulation of the liquid phase of the two-phase fluid, and in particular to allow the liquid condensed at the level of the condenser to reach the evaporator, as represented by the arrows FL in Figure 1a. The main capillary structure 14 also extends over the entire length of the cavity, going from the evaporator to the condenser, to allow this circulation of liquid.

[0043] A capillary structure is a structure whose geometry is such that it generates surface tension effects, thus making it possible to retain and circulate the liquid by capillary action. Surface tension effects may in particular predominate over gravity or inertia effects. The hair structure can be made in different ways. For example, and as can be seen in FIG. 1b, the capillary structure can be formed from a set of grooves 140 of small diameter, for example between 1 and 3 mm. In the example of FIG. 2, the capillary structure comprises a plurality of grooves which are distributed around a vapor circulation channel 13, extending parallel thereto. The grooves 140 each have a side opening 141 extending in the main direction of the groove, the side opening opening into the steam circulation channel 13 to allow steam contained in a groove 140 to join the channel. In FIG. 1b, the profile of the grooves has an open profile rounded in Q. This type of profile favors in particular the appearance of capillary pressure.

[0044] As a variant, one could have an open teardrop or œ profile with its wide curvatures arranged opposite the cold surface, opposite the opening. Such a profile for example closes slightly according to a ratio of less than 2 (that is to say that the width of the opening is greater than half of the greatest width) so as to avoid the formation of a bridge and avoid trapping steam in the grooves. Advantageously, with a teardrop or œ profile, vapor is not retained because of a liquid bridge which would form at the end, in particular in micro-gravity, which could make the two-phase structure unstable or even non-operational. Also advantageously, a teardrop or œ profile promotes drainage of the cold surface.

[0045] The choice of the profile will for example be made to best adapt to the case of use.

In another example, shown in Figure 4, the heat transfer device 1 may have a generally parallelepipedic shape, and include at least one vapor circulation channel 13 extending in the main direction of the transfer device 1 heat. Grooves 140 for the circulation of the liquid phase can also extend parallel along the main direction of the heat transfer device, and comprise a lateral opening 141 extending in the main direction of each groove and opening into the channel 13 of steam circulation. Alternatively, as shown in Figure 6, the main capillary structure 14 may be formed of a mesh, comprising a set of capillary fibers of small diameter, for example between 0.5 and 1 mm, interconnected to each other. According to yet another variant, the capillary structure can be a porous medium, for example by being formed of a material consisting of a porous micro-structure making said material permeable to the fluid in question.

In FIG. 1b, the circulation of the two-phase fluid at the level of an evaporator 20 is schematically represented. The liquid contained in the capillary structure and routed from the condenser 30 vaporizes under the effect of the heat transmitted by the hot source 2. The vapor obtained joins the vapor circulation channel 13 and as visible in figure 1a, progresses in the cavity 10 until it reaches the condenser 30, where it condenses and the condensed liquid joins the main capillary structure 14 .

The heat transfer device 1 further comprises a reservoir 15 for storing an excess of two-phase fluid liquid, this reservoir being formed by an additional capillary medium. The additional capillary medium 15 which stores and restores the fluid in the liquid phase is connected to the main capillary structure 14 so as to ensure capillary continuity for the fluid in the liquid phase. The additional medium comprises a reservoir capillary zone and may also comprise a vapor channel. Such a vapor channel can for example be useful in cases, as represented in FIGS. 8a and 8b, where the level of liquid filling in the tank varies between 0% and 100% or even between 5% and 95%, vapor being then also present in this reservoir zone. Thus the presence of a vapor channel nearby will allow the vapor to be evacuated more easily when the liquid will penetrate the tank.

In some embodiments, the additional capillary medium has no structural function for the heat transfer device 1, that is to say it does not contribute to its mechanical strength, unlike the cavity 10 and in particular to its envelope 11.

[0050] The vapor channels are for example all interconnected. The interconnected vapor channels thus form a single continuous space. In some embodiments, if the additional capillary medium 15 is adjacent to the vapor channel 13 of the cavity 10, it does not completely obstruct the section of this vapor channel.

The term “capillary continuity for the fluid in the liquid phase” or “capillary liquid continuity” means the fact that an exchange of fluid in the liquid phase can take place by capillarity, in one direction or the other, at each place where a capillary continuity is formed for the fluid in the liquid phase, in particular between the additional capillary medium and the main capillary structure. The additional capillary medium is thus attached to the main capillary structure. The fluid in the liquid phase can thus move towards the additional capillary medium or towards the capillary structure. In this respect, the main capillary structure 14 and the additional capillary medium 15 are preferably shaped so that there is no discontinuity between these two capillary media. The term “discontinuity” is understood to mean one or more cavities whose dimension would exceed the larger characteristic capillary dimension of the two media.

Thus, when the device 1 heats up, the volume of two-phase fluid in liquid form will tend to increase and the additional capillary storage medium will fill passively and thus prevent the formation of a liquid plug. Conversely, when the device 1 cools, the volume of two-phase fluid in liquid form will tend to decrease and the additional capillary storage medium will empty passively and thus prevent the main capillary structure from drying out.

In this way, the additional capillary medium 15 can store an excess of liquid which could not be contained in the main capillary structure 14 which is already full and which would disturb the operation of the heat transfer device by placing itself in the vapor channels. . This storage makes it possible to make the heat transfer device operational, with optimized performance, whatever the position or configuration of the heat transfer device.

In some embodiments, the additional capillary medium is sized, depending on the sizing of the heat transfer device 1 and the quantity of two-phase fluid, to present a filling rate strictly between 0 and 100%, of preferably strictly between 5 and 95% when the heat transfer device is in operation. The filling rate corresponds to the ratio between the volume of liquid contained in the additional capillary medium, constituting the reservoir or reservoirs, and the total volume that can be contained in this medium. In other words, the quantity of diphasic fluid in the cavity being constant but with a volume of liquid which can vary between a minimum volume and a maximum volume, the additional capillary medium can be advantageously dimensioned, as illustrated in FIGS. 8a and 8b, so that: when the volume of liquid is minimal, the main capillary structure 14 is always full of liquid, and the additional capillary medium is slightly filled, of the order of 0 to 5% filling rate, and when the volume of liquid is maximum, the main capillary structure 14 is full of liquid and the additional capillary medium is completely filled, without however, reach saturation to avoid disruption of the operation of the device, that is to say with a filling rate of the order of 95% to 100%.

The volume of liquid in the cavity can vary between Volume_min and Volume_max, so that at any time the total volume of liquid is equal to Volume_t = Volume_min + Delta_Volume_t

Furthermore, Volume_max=Volume_min+Delta_Volume_max.

The main capillary structure has, for example, a reception volume equal to Volume_min and all of the excess liquid, i.e. Delta_Volume_t> will be housed in the additional structure forming a reservoir. The additional structure forming a reservoir must then be able to contain a volume corresponding to Delta_Volume_max.

It is thus possible to provide a volume of the additional capillary structure forming a reservoir greater than or equal to Delta_Volume_max.

Thus for a minimum total volume, only the main structure 14 will be filled, while for a maximum total volume, the main structure 14 and the additional structure forming a reservoir 15 are full.

In practice, an operating safety margin can be provided with, for example:

- for a minimum volume, the main structure 14 full and the additional structure forming a reservoir 15 filled to 5% and

- for a maximum volume, the main structure 14 full and the additional structure forming a reservoir 15 filled to 95%.

In the cases of Figures 8a and 8b, the reservoir 15 is for example filled according to a filling rate varying between 0% and 100% or even between 5% and 95%, while the rest of the capillary structure is always full. 100%.

In the cases of FIGS. 8c and 8d, the condenser 143, which has the largest capillary structure, will fill last, while all the other capillary structures receiving liquid are always 100% filled. The degree of filling of the condenser varies for example between 0% and 100% or even between 5% and 95%. The capillary structure of the condenser (which forms part of the main structure 14) is preferably not 100% full since the additional capillary structure 15 has a smaller dimension than that of the condenser. The additional capillary structure 15 will therefore tend to suck the liquid from the condenser. We therefore have the evaporator structure which is full and the adiabatic structure which is full, while the capillary structure of the condenser is partially filled and varies for example between 5 and 95%. The additional liquid storage volume represented by the additional capillary medium is for example less than the volume of the main capillary structure 14 and preferably less than 50% of the volume of the main capillary structure.

In embodiments, the storage volume available for the liquid in the additional capillary medium is between 10 and 40% of the volume available for the liquid in the main capillary structure. The volume of the additional storage medium depends on the two-phase fluid considered as well as on the operational temperature range.

With reference to Figures 8a to 8d, we will now describe embodiments of the dimensioning of the different capillary structures.

In what follows, the term “characteristic capillary dimension” refers to the average dimension of the capillary cavities of the capillary structure considered. In the case where the capillary structure is porous, the characteristic capillary dimension may correspond to the average diameter of the pores. In the case where the capillary structure is formed of a mesh of solid fibers (fig 6), the characteristic capillary dimension may correspond to the diameter of the largest spherical particle which could pass through it. In the case where the capillary structure is formed of grooves, the characteristic capillary dimension may correspond to the hydraulic diameter of the opening 141 connecting a groove 140 to the vapor circulation channel 13.

The smaller the characteristic capillary dimension, the greater the capillarity phenomenon. Consequently, the various capillary structures of the device 1 advantageously have a characteristic capillary dimension hierarchy making it possible to ensure the flow of the liquid to the evaporator.

Thus, the main capillary structure 14 may have different characteristic capillary dimensions along the cavity. For example, the capillary structure 14 can comprise at least one capillary condensation zone 143 in the condenser 30, a capillary evaporation zone 142 in the evaporator 20 and optionally a capillary flow zone 144 connected on the one hand to the capillary condensation zone and on the other hand to the evaporator, and the different zones of the capillary structure 14 can have different characteristic capillary dimensions.

In one embodiment represented schematically in FIG. 8a, the capillary structure 14 has a larger characteristic capillary dimension sc at the level of the condenser 30, that is to say in the capillary condensation zone 143, than at the level of the condenser 30. evaporator level 20 (eev). In a variant shown in Figure 8b, the cavity 10 further comprises an adiabatic zone 12 and the main capillary structure 14 comprises an evaporation capillary zone 142 having a characteristic capillary dimension æv less than the characteristic dimension of the adiabatic zone sa, which is itself less than the characteristic capillary dimension EC of the capillary condensation zone 143.

In some embodiments, the additional capillary medium 15 may have a characteristic capillary dimension cr greater than or equal to the maximum characteristic capillary dimension of the main capillary structure 14. Thus, when the quantity of liquid decreases and the liquid in excess stored in the reservoir must be recovered to contribute to the operation of the device, this hierarchy of capillary dimensions ensures that the liquid returns to the main capillary structure and does not remain stored in the reservoir. This is the case shown schematically in Figures 8a and 8b.

As a variant represented schematically in FIGS. 8c and 8d, which represent a device respectively with and without an adiabatic zone, in the case where the main capillary structure 14 has zones of variable characteristic capillary dimensions, the additional capillary medium 15 may have a characteristic capillary dimension cr less than a characteristic capillary dimension EC of the capillary condensation zone 143, but greater than or equal to a characteristic capillary dimension £a of the capillary flow zone 144 and/or of that æv of the capillary zone d evaporation 142.

The additional capillary storage medium 15 may also have a variable characteristic capillary dimension and in this case, the minimum characteristic capillary dimension of the additional capillary storage medium is located at the level of the connection with the main capillary structure.

This minimum characteristic capillary dimension of the storage medium may for example be greater than or equal to the maximum characteristic capillary dimension of the main capillary structure.

As indicated previously, the cavity 10 may comprise one or more steam circulation channels 13. These channels 13 may also have different sections, the minimum section channels being located at the level of the evaporation zone.

In some embodiments, the maximum characteristic capillary dimension of the additional capillary storage medium 15 is less than or equal to the minimum characteristic dimension of the vapor circulation channels 14, which corresponds typically to their hydraulic diameter. The channels of the evaporation zone 20 alone can have a diameter less than a capillary dimension characteristic of the additional capillary medium.

In some embodiments, the additional capillary storage medium 15 can be connected to the main capillary structure 14 at the level of the condensation zone 30.

In some embodiments, the additional capillary storage medium can also be connected to the capillary structure at the level of an adiabatic zone 12, or even also at the level of the evaporation zone 20. However, the condensation zone 30 being the coldest and furthest from the heat source, it is advantageous to have at least one connection between the main capillary structure 14 and an additional capillary storage medium 15 at the level of this condensation zone 30.

One or more additional capillary media can be provided, each connected by a single connection with the main capillary medium, the main capillary medium ensuring circulation of the liquid between the cold source and the hot source.

FIG. 5 shows the circulation of the two-phase fluid between the evaporator 20 and the condenser 30, the dotted arrows representing the possible connections between an additional capillary storage medium and the main capillary structure, the main capillary medium ensuring circulation of the liquid between the cold source and the hot source. The evaporation at the level of the evaporator is represented by the arrow L->V and the condensation at the level of the condenser 30 is represented by the arrow

In some embodiments, the additional capillary storage medium 15 is manufactured by additive manufacturing (3D printing), also designated by ALM, to enable the capillary structuring of this medium to be precisely produced.

As a variant, the additional capillary storage medium can also be produced by extrusion or machining.

The additional capillary storage medium is for example made of metal, for example aluminum, titanium or invar.

Referring to Figures 2 to 4, there is shown an example of configuration of an additional capillary medium for storing excess liquid. In Figures 2 and 3, the envelope 11 of the device is not shown, unlike Figure 4. In these figures 2 to 4, the heat transfer device has a substantially extended parallelepipedal shape, the condensation zone 30 of which occupies an end section.

The heat transfer device may comprise an adiabatic zone 12, corresponding to another section of the device, this adiabatic zone, as shown in Figure 2, can be arranged in the extension of the condensation zone 30.

The example heat transfer device according to Figure 2 also includes an evaporation section. This evaporation section, not shown in Figure 2, is connected to the adiabatic section.

The heat transfer device may comprise a vapor circulation channel 13 of parallelepipedal section extending along the main direction of the heat transfer device 1. The vapor circulation channel 13 can be delimited, in the condenser, on one side, by the capillary structure of the condenser 30 and on other sides by the additional capillary medium 15. As represented in FIG. 4, the capillary structure of the condenser 30 comprises a set of grooves 140 extending parallel to the vapor circulation channel. The grooves 140 include a side opening 141 extending in the main direction of the grooves and opening into the vapor circulation channel. The additional capillary medium 15 is here shaped in a U to surround the vapor circulation channel 13, and to be connected, by the two free ends of the U, to the capillary structure of the condenser 30. The additional capillary medium 15 can thus delimit, on three sides, the steam circulation channel 13.

As shown in Figure 2, the vapor channel can extend into the adiabatic zone by passing through the center of an adiabatic capillary structure extending around the periphery of the adiabatic zone.

The capillary continuity between on the one hand the capillary structure of the condenser 30 and on the other hand the additional capillary medium and possibly the capillary structure of the adiabatic zone, is achieved, for example, at the level of the ends of the grooves 140 of the capillary structure of the condenser 30.

A capillary continuity can also be achieved on one face of the U, between the additional capillary medium 15 and the capillary structure of the adiabatic zone.

The additional capillary medium 15 may be formed, for example, of a lattice or of a porous structure. An example of a truss is shown in Figure 6. In an alternative embodiment, represented schematically in FIG. 7, the additional capillary medium 15 can form an additional section at one end of a two-phase device 1 successively comprising an evaporation zone 142, optionally an adiabatic zone 144 and an condensation zone 143. The additional section corresponding to the additional capillary medium 15 is preferably adjacent to the condensation zone 143 so that the additional capillary medium 15 is connected in liquid capillary continuity with the capillary condensation structure.

List of reference signs

[0095] 1: heat transfer device or heat pipe

[0096] 2: hot spring

[0097] 3: cold source

[0098] 10: cavity

[0099] 11: envelope

[0100] 12: adiabatic zone

[0101] 13: steam circulation channel

[0102] 14: main capillary structure

[0103] 140: groove

[0104] 141: lateral opening of a groove

[0105] 142: evaporation zone of the main capillary structure

[0106] 143: condensation zone of the main capillary structure

[0107] 144: flow zone of the main capillary structure

[0108] 15: additional capillary storage medium

[0109] 150: section of the additional capillary medium

[0110] 20: evaporation zone / evaporator

[0111] 30: condensation zone / condenser

[0112] FV: vapor circulation arrow

[0113] FL: liquid circulation arrow

[0114] cev: characteristic capillary dimension of the evaporation zone of the main capillary structure [0115] EC: characteristic capillary dimension of the condensation zone of the main capillary structure

[0116] Ea: characteristic capillary dimension of the flow zone of the main capillary structure [0117] Er: characteristic capillary dimension of the additional capillary medium.

Claims

[Claim 1] Two-phase heat transfer device (1), comprising a closed cavity (10) comprising at least one evaporation zone (20) in a heat exchange situation with at least one hot source (2) and at least a condensation zone (30) in a heat exchange situation with at least one cold source (3), the closed cavity (10) containing a two-phase fluid in the state of liquid-vapor equilibrium and comprising at least one channel ( 13) circulation of the two-phase fluid in the vapor phase and at least one main capillary structure (14) adapted to allow the circulation of the two-phase fluid in the liquid phase between said cold source and said hot source, the two-phase device (1) being characterized in that that it further comprises at least one additional capillary medium (15) allowing storage and restitution of excess liquid relative to a maximum capacity of liquid contained in the main capillary structure (14), said additional capillary medium ( 15) and said main capillary structure (14) being connected so as to ensure capillary continuity for the two-phase fluid in the liquid phase, said additional medium (15) comprising at least one reservoir capillary zone, the main capillary structure (14) comprising at least at least one capillary condensation zone (143) and one capillary evaporation zone (142), the evaporation (142) and condensation (143) zones of the main capillary structure, taken in order, have capillary dimensions increasing characteristics, said capillary dimensions being smaller than the diameter of the vapor circulation channel, and the additional capillary medium (15) has a characteristic capillary dimension greater than that of the evaporation zone and smaller than the diameter of the vapor circulation channel.

[Claim 2] Two-phase device (1) according to claim 1, in which the reservoir capillary zone is directly connected to the condensation capillary zone and has a characteristic capillary dimension (s _r ) greater than a characteristic capillary dimension (s _c ) of the capillary condensation zone (143).

[Claim s] Two-phase device (1) according to one of Claims 1 or 2, in which the main capillary structure (14) further comprises a capillary flow zone connected on the one hand to the capillary condensation zone (143 ) and on the other hand to the capillary evaporation zone (142), the zones, taken in order, of evaporation, flow, and condensation having increasing characteristic capillary dimensions, said characteristic capillary dimensions being smaller to the diameter of the steam circulation channel.

[Claim 4] Two-phase device (1) according to Claim 3, in which the said reservoir capillary zone is directly connected to the flow zone and has a characteristic capillary dimension greater than a characteristic capillary dimension of the flow zone.

[Claim s] Two-phase device (1) according to one of the preceding claims, in which the additional capillary medium (15) is in contact on the one hand with the vapor circulation channel (13) and on the other hand with the main capillary structure (14).

[Claim 6] Two-phase device (1) according to the preceding claim, in which the additional capillary medium (15) comprises the reservoir capillary zone and a vapor circulation channel.

[Claim 7] Two-phase device (1) according to one of the preceding claims, the volume of two-phase fluid in the liquid phase in the cavity is variable between a minimum volume Vmin and a maximum volume Vmax, the volume of the additional capillary medium (15) is greater than or equal to the difference in volume between the maximum volume and the minimum volume, and less than 50% of the volume of the main capillary structure (14).

[Claim s] Two-phase device (1) according to one of the preceding claims, in which the additional capillary medium (15) has a minimum characteristic capillary dimension at the level of the connection with the main capillary structure (14) for the circulation of the fluid diphasic in the liquid phase.

[Claim s] Two-phase device (1) according to one of the preceding claims, in which the additional capillary medium (15) is dimensioned so as to have a degree of filling comprised strictly between 0 and 100%, preferably comprised strictly between 5 and 95%, when the two-phase heat transfer device (1) is in operation.

[Claim 10] Two-phase device (1) according to one of the preceding claims, in which the volume available for the liquid in the additional capillary medium (15) is between 10 and 40% of the volume available for the liquid in the capillary structure main (14) of the cavity (10).

[Claim 11] Two-phase device (1) according to one of the preceding claims, in which the additional capillary medium (15) is a mesh and/or is formed from a porous material.