阅读说明：本技术 具有优化汽化界面的蒸发器 (Evaporator with optimized vaporization interface ) 是由 文森特·杜庞特 斯泰凡·维恩·奥斯特 文森特·德·特罗兹 米卡尔·莫豪普特 于 2018-04-12 设计创作，主要内容包括：本发明涉及适用于换热系统的毛细蒸发器,包括用于获取热能的元件(1)和初级毛细管(2),用于获取热能的元件(1)还包括基部(10)和多个突起部分(11),每个突起部分从基部延伸至尖端(12),且其尺寸随着与基部距离的增加而减小,初级毛细管(2)由多孔第一材料制成且其正面(20)与突起部分的尖端相邻,突起部分的侧壁与初级毛细管一起界定空隙(4),空隙(4)形成蒸汽通道,突起部分的侧壁由多孔材料薄层(3)覆盖,薄层的最厚部分(31)在邻近的每个突起的尖端附近与初级毛细管相接触,并且所述薄层的厚度(EC)随着与初级毛细管的距离增加而减小。(The invention relates to a capillary evaporator suitable for a heat exchange system, comprising an element (1) for extracting thermal energy and a primary capillary (2), the element (1) for extracting thermal energy further comprising a base (10) and a plurality of protruding portions (11), each protruding portion extending from the base to a tip (12) and decreasing in size with increasing distance from the base, the primary capillary (2) being made of a porous -th material and having a front face (20) adjacent to the tip of the protruding portion, the side walls of the protruding portion defining a void (4) with the primary capillary (), the void (4) forming a vapor channel, the side walls of the protruding portion being covered by a thin layer (3) of a porous material, the thickest portion (31) of the thin layer being in contact with the primary capillary near the tip of each adjacent protrusion, and the thickness (EC) of said thin layer decreasing with increasing distance from the primary capillary.)

1. A capillary evaporator suitable for use in a heat exchange system, wherein the evaporator comprises:

-a heated element (1) comprising a base (10) and a plurality of protruding portions (11), each protruding portion extending from the base to a tip (12) and having a smaller dimension the further away from the base, each protruding portion having a side wall (13),

-a primary capillary (2) made of a porous th material and having a front face (20) adjacent to the tip of the protruding portion, the side walls of the protruding portion defining a void (4) together with the primary capillary (), said void (4) forming a vapor channel,

characterized in that the side walls (13) of the protruding parts are covered by a thin layer (3) of a porous material, preferably a second material different from the th material.

2. An evaporator according to claim 1 wherein the thin layer (3) has a substantially uniform thickness.

3. An evaporator according to claim 1 wherein the thin layer (3) has a non-uniform thickness, the thickest part (31) of the thin layer is in contact with the primary capillary near the tip of each protruding portion, and the thickness (EC) of the thin layer becomes smaller as the distance from the primary capillary increases.

4. An evaporator according to any wherein the protruding portion is formed in a shape of a straight rib of a trapezoidal cross section.

5. An evaporator according to claim 4 wherein the raised portions are adjacent to each other, and each steam channel has a generally triangular cross-section with its tip directed toward the base of the heated element.

6. An evaporator according to claim 5 wherein the cross-section forms a symmetrical isosceles trapezoid with a base W and a minor side D3, and D3<0.2W, and a minor side D3 having a dimension <0.3 mm.

7. An evaporator according to wherein the half angle of the tip α is preferably between 5 ° and 30 °.

8. The evaporator according to , characterized in that the primary capillary (2) is obtained from a material with poor thermal conductivity, such as ceramic, stainless steel or polytetrafluoroethylene.

9. -evaporator according to any of claims 1 to 8, characterized in that the thin layer (3) is obtained from a second material that is a good thermal conductor, such as copper, aluminum or nickel.

10. An evaporator according to characterised in that the diameter of the pores of the lamella (3) is smaller than the diameter of the pores of the primary capillary (2).

11. A heat exchange system comprising an evaporator according to any of the preceding claims, a condenser, a fluid conduit with gravity pumping, i.e. a thermosiphon configuration, or a fluid conduit that is capillary pumping only or in combination with an ejector, or a mechanically pumped fluid conduit.

Technical Field

The present invention relates to evaporators, typically used in heat exchange systems with a two-phase working fluid.

More particularly, the present invention relates to a vaporization interface for liquids to be converted to a vapor by absorbing a large amount of thermal energy.

Background

This type of evaporator is commonly used to cool electronic devices such as processor (CPU, GPU) power modules (IGBT, SiC, GaN, etc.) or any other electronic components that generate heat or any other heat source.

Evaporators of this type are often used in systems that include a condenser and a liquid supply line and a return line for circulating fluid between the evaporator and the condenser.

Current trends have caused electronic products to dissipate large amounts of heat output over their small surfaces.

In the evaporator, at the interface between the capillary (entrained liquid) and the element or plate for heating/transferring heat energy (in contact with the primary heat source providing heat energy), an empty space is provided which forms a vapor release channel. These vapor passages are provided in the capillary or in the heated element. Most commonly, grooves of rectangular cross-section are provided to form such steam channels, as described, for example, in patent US5725049[ NASA ].

Some developers have attempted to increase capacity in terms of heat flux by designing differently shaped steam channels to increase heat capacity. In fact, the presence of the vapor channels leads to a concentration of the heat flux density in contact with the capillary, which has led developers to prefer "concave" grooves, for example, patent EP0987509[ Matra Marconi Space ].

Other developers have tried to minimize parasitic heat losses, such as patent US6330907[ Mitsubishi ], but have failed to avoid the formation of vapor bubbles in the contact area with the capillary, which may compromise the reliable liquid supply to the vaporization region.

However, it can be seen that the known vaporization interface does not allow to handle surface heat fluxes above 20 watts/cm 2, since the heat exchange coefficient decreases greatly with increasing heat flux density due to the indentation in the vaporization front inside the primary capillary. An increase in the number of vapour bubbles inside the capillary also leads to an increased risk of drying, in other words a risk of interruption of the liquid supply at this location should also be avoided.

However, the results show that the demand is now even higher, which is why the inventors sought to further optimize the evaporator vaporization interface in a heat transfer loop with a two-phase working fluid.

Disclosure of Invention

To this end, the object of the present invention is a capillary evaporator suitable for use in a heat exchange system, wherein the evaporator comprises:

-a heated element (1) comprising a base (10) and a plurality of protruding portions (11), each protruding portion extending from the base to a tip (12) and having a smaller dimension the further away from the base, each protruding portion having a side wall (13),

-a primary capillary (2) made of a porous th material and having a front face (20) adjacent to the tip of the protruding portion, the side walls of the protruding portion defining a void (4) forming a vapour channel together with the primary capillary (), characterized in that the side walls of the protruding portion are covered by a thin layer (3) of porous material, preferably a second material different from the th material.

The term "thin layer" is understood to mean a thin layer having a layer thickness of less than 1 mm. The inventors have found that a lower thickness limit in relation to the protruding portion advantageously contributes to obtaining good performance.

It should be noted that the thin layer of porous material is in contact with the primary capillary at the junction where liquid flows from the primary capillary to the location where the thin layer of porous material forms the secondary capillary.

The term "the size of which decreases with distance from the base" is to be understood as meaning that the decrease of at least sizes of the protruding part (11) is decreasing starting from the base (10) (i.e. the farther away from the base the smaller).

Advantageously, the liquid phase fluid is pumped by capillary action from the primary capillary to the thin layer covering the protrusions and is vaporized at this location; so that the heat exchange surface area is increased. By these arrangements, a device capable of handling more than 50 watts/cm is obtained²The evaporation interface of the heat flux, whose heat exchange coefficient W/(m2K) is much higher than that of the current art, depending on the various possible configurations, can even handle tens or even hundreds of watts/cm²。

It should also be noted that, in the region of the projection tips, the heat flux transmitted directly in correspondence with the primary capillaries is significantly reduced with respect to the total heat flux (evaporated mainly by the side walls) and therefore the boiling phenomenon is avoided in the region in contact with the primary capillaries, in other words, overheating of the primary capillaries is avoided. Thus, the transfer of parasitic flux is limited by significantly reducing the penetration of evaporation into the primary capillary and reducing the overheating of the heated element while facilitating the extraction of the evaporation generated in the dedicated channel.

In various embodiments of the invention, one or more of the following are used:

in this configuration, a relatively simple method of manufacture and assembly may be provided by using a wire mesh in intimate contact with the surface of the heated element.

According to options, the thin layer can have a non-uniform thickness, the thickest part (31) of the thin layer being in contact with the primary capillaries adjacent to the respective protruding tips, the thickness (EC) of the thin layer decreasing with increasing distance from the primary capillaries.

According to options, the thermal energy heating element may comprise a flat plate corresponding to a flat plate configuration for cooling the heat source.

According to another solutions, the heated element may have a conventional cylindrical shape, which may correspond to the cylindrical configuration used for the heat source to be cooled, which is common in planar configurations, when using high pressure fluids, such as ammonia for space applications, which is common in the case of a cylindrical evaporator, where a flat plate, typically of aluminum, may be assembled on the outer surface of the cylindrical evaporator.

According to solutions, the projecting portion can advantageously be formed with rectilinear ribs of trapezoidal (even triangular) cross-section, thus making it easy to manufacture the heated element by extrusion or simple machining (milling). moreover, this trapezoidal cross-section allows a secure transmission of mechanical forces, in particular those caused by the extrusion assembly of the power module on the evaporator by means of screwing (which does not allow traditional thin fins, in particular copper, with a substantially constant thickness on the side of their height).

According to solutions, the protrusions are located close to each other, and each steam channel (4) has a substantially triangular cross-section with its tip directed towards the base of the heated element, so that, for a given total available surface area, the density of the thin layer coverage is maximized, thus also maximizing the heat exchange.

According to the solutions, the cross-section of the protrusion forms a symmetrical isosceles trapezoid (i.e. "tooth"), with a length of the short side of at most 20% in relation to the length of the long side, in other words D3<0.2W, thereby forming a steam channel of sufficient size, in particular, its width between the protrusion tip, allowing a fast flow of steam without excessive pressure loss.

According to solutions, the minor side D3 (in other words, the width of the tip) is dimensioned less than <0.3mm the inventors noticed that, contrary to what is envisioned by the skilled person, the thickness of the tip is not problematic and is an advantage if combined with the presence of thin layers, since it avoids the appearance of vapour phases in the feed zone and limits the parasitic flux transport through the primary capillary.

According to solutions, the half angle at the tip α is less than 45 ° and preferably between 5 ° and 30 ° for the cross-sectional geometry of the protruding portion.

This corresponds to the fact that: the height of the protruding portion H2 is 1/2 greater than the upper expanded portion W of the base, which explains the improvement in heat exchange efficiency due to the increase in the effective surface area.

According to the version, the primary capillary is preferably made of a poor thermally conductive material, such as nickel, stainless steel, ceramic or polytetrafluoroethylene, which typically has a thermal conductivity of less than 100W/mK. so that heating of the liquid on the other side of the primary capillary is avoided and parasitic heat loss is greatly reduced.

According to the solutions, the thin layer is obtained from a good thermal conductor, for example copper or aluminium, typically with a coefficient greater than 100W/mK and preferably greater than 380W/mK.

This results in a good gas permeability of the sheet and a good distribution of vaporization sites.

According to , the pores of the sheet have a diameter less than the pores of the primary capillaries, thereby facilitating liquid supply from the primary capillaries to the sheet and liquid supply within the sheet to the thickest part.

According to solutions, the thickness EC of the thin layer is less than 0.5mm, preferably at the location where the thin layer is in contact with the heated plate 1. the inventors have found that it is advantageous that such a small thickness is sufficient to obtain good performance, furthermore, it will be noted that the heated plate is not flat (presence of the raised portions 11), unlike certain embodiments of the prior art.

According to solutions, the thickness H1 of the base is between 0.5 and 5mm, this thickness being adjusted in order to obtain sufficient assembly rigidity and strength, for example, by means of screw fixing of the components to be cooled.

According to solutions, the height H2 of the protruding part is between 0.5 and 3mm, the height being adjusted so that a sufficient flow area is obtained in the steam channel to avoid possible pressure loss problems.

According to , the protruding portion is formed in a shape of a circular rib, which can be used in the case where the evaporator is in the form of a magnetic disk.

According to , the protrusions are formed in the shape of conical bolts or pyramidal studs, which can further increase the surface efficiency and, depending on the manufacturing method used, can keep the cost price of coating the heated plate reasonable.

According to solutions, the thickness E2 of the primary capillary is constant and preferably between 1 and 8 mm.

According to , the tip of the protruding portion is in contact with the primary capillary and the surface area is less than 20% of the effective surface area of the primary capillary.

The invention also relates to heat exchange systems, wherein the heat exchange system comprises an evaporator, a condenser, fluid conduits with gravity pumping as described above, i.e. a thermosiphon configuration (including a "pool boiling" configuration), or fluid conduits for capillary pumping only or in combination with an ejector, or an evaporator provided by a mechanical pump.

Drawings

Other aspects, objects and advantages of the invention will become apparent from a reading of the following description of embodiments of the invention, given as non-limiting examples. The invention may be better understood by reference to the following drawings, in which:

figure 1 is a schematic general view of a heat exchange system comprising an evaporator according to the present invention;

FIG. 2 is a partial cross-sectional view of the evaporator according to embodiment , taken along section II-II shown in FIG. 1;

figure 3 is a schematic partial perspective view of the evaporator;

figure 4 shows in more detail a portion of the cross-section and shows the protruding portion and its porous coating;

figure 5 shows a second embodiment of the cylindrical evaporator type (not flat);

FIG. 6 shows the distribution of the vaporization flux along the wall of a projecting portion with a thin coating of porous material;

figure 7 shows the heat flux inside the protruding part and the liquid supply flow along the lamella;

figure 8 shows the arrangement of the steam channel in a horizontal section view along the section VIII-VIII as shown in figure 2;

FIG. 9 is a schematic horizontal cross-section showing another alternative embodiments of evaporators with studs;

fig. 10 shows two alternative embodiments regarding the configuration of the thin layer of porous material.

The same reference numbers in different drawings identify the same or similar elements. For clarity, the dimensions of the parts are not shown to scale.

Detailed Description

Fig. 1 shows a heat exchange system comprising an evaporator 7, said evaporator 7 comprising a heated element 1 which makes it possible to bring the heat Qin flux obtained by the evaporator 7 from a dissipating component ("heat source") to a condenser COND receiving this heat, which brings Qout to a "radiator" (ambient air, hot or cold water, radiator plate, etc.).

The steam pipe 8 transports the steam produced by the evaporator to the condenser the liquid pipe 9 makes it possible to bring the liquid condensed by the condenser back to the evaporator 7, given that the condenser and the pipe are well known on each side, and therefore not described in detail herein, the evaporator, the condenser and the pipe form a heat transfer circuit working by using gravity (thermosiphon) or by using a capillary pump, which is solutions that are feasible on land and also in a weightless condition, or solutions for the acceleration field (gravity, vehicle movement) or using a mechanical pump to assist pumping.

In the example shown in fig. 1, a reservoir RES is represented, which acts as a liquid expansion tank (thermal expansion of the liquid, variation of the vapour quantity outside the reservoir), in the case where it is a separate element we call it CPL (capillary suction circuit), in another configurations, the reservoir function is provided inside the evaporator, and in this case we call it LHP (circulation heating pipe), in the case of the "thermosiphon" configuration, there is no need to configure the reservoir.

The operation of each side of the circuit is generally known, in particular in circuits with steam tubes, liquid conduits and condensers, and will not be described in detail herein. Hereinafter, attention will be focused on the evaporator and its internal structure.

The evaporator 7 comprises a heated element, designated 1, which in the illustrated th example is a flat plate 1 (not shown) resting on the element to be cooled, which provides a heat energy flux, designated Qin, which plate is provided with a specific structure inside the evaporator, as will be explained in detail below.

The corresponding evaporator 7 is a capillary type evaporator, which means that it contains capillary tubes, in other words porous bodies, which absorb liquid by capillary action, the liquid being stored in a liquid tank 5 communicating with a liquid conduit 9 and an expansion reservoir RES.

It should be noted that the term "conversion element" 1 may be used instead of the term "heat receiving element" from a wider perspective than the evaporator. In the following, the term "heating plate" or "heated plate" may be used in some cases instead of the term "heated element".

Structurally, the evaporator 7 comprises the above-mentioned heating plate 1 with a capillary structure, described in detail below, the above-mentioned liquid tank 5, and a cover shell making it possible to assemble it and define a closed space of the evaporator in which the sealant contains the working fluid.

More specifically, the capillary structure comprises a primary capillary, designated 2, coated with a capillary coating structure forming a thin layer of porous material (designated 3), discussed in detail below.

According to the th embodiment shown particularly in fig. 2 to 4, the heating plate, in other words the heated element 1, comprises a base 10 extending in two directions Y, Z perpendicular to the depth axis marked X along a plane YZ, and a plurality of protruding parts 11 each extending from the base 10 to a tip 12 and having side walls marked 13.

Advantageously, the respective size (dimension) of said projecting portions 11 decreases with distance from the base, in other words, at least dimensions of the projecting portions 11 decrease with distance from the base 10, in other words, the side walls 13 are, in fact, not parallel to each other.

More specifically, as we consider the cross-section of the projection in the XY plane (fig. 2 and 4), which has the shape of a trapezoid with a wide base dimension designated W and a narrow tip dimension designated d3 the base and tip are parallel, i.e. parallel to the Y axis, the projection side wall 13 extends obliquely at an angle of β with respect to the base.

The protruding portion 11 may also be referred to as a "tooth" when viewed in cross section.

In the example shown, the shape of the trapezoid is symmetrical, more precisely a symmetrical isosceles trapezoid, where D3< 0.2W.

This shape can also be described as a truncated cone with half angle at the tip labeled α preferably, we choose α <45 °, otherwise, β >45 °.

Preferably, the half angle at the selected tip α is between 5 ° and 30 °.

According to specific embodiments, the dimension of the minor side D3 is <0.3 mm.

As shown in fig. 3, the protruding portion extends in the Z direction with a constant cross section. Thus, a space, shaped as a groove 4, also referred to herein as a "vaporization channel" 4 or a "steam channel" is formed between the protruding portions.

Advantageously, the protruding portions 11 are provided adjacent to each other, the adjacent protruding portions being separated by the steam channel 4; thus, we note that the pitch of the repeating pattern along the Y axis corresponds to the dimension W, which is exactly the width of the raised portion 11 on the base.

The height of the vaporization passage is labeled H2. In this example, the protruding portion is formed in a linear rib shape of a trapezoidal cross section, and W denotes a repetition pitch along the Y axis.

The primary capillary labeled 2 may be formed from a thick layer of porous material; in the example shown, the thickness E2 of this layer is constant over the entire surface of the evaporator, which allows the use of inexpensive standard products. For the thickness E2 of the primary capillary, a value between 1mm and 8mm, preferably between 2mm and 5mm, can be chosen.

The primary capillary 2 has a front side 20 facing the heated plate 1 and a back side 25 in contact with the liquid 5. Alternatively, the planar primary capillary tube may be supplemented with an inner wall 28 forming a rigid structure that enhances the mechanical strength of the evaporator. The inner wall may be porous or non-porous depending on the functional requirements of liquid distribution by capillary action.

Primary capillaries with non-constant thickness are not excluded, as shown below.

For the primary capillary 2, a material with poor thermal conductivity is preferably selected, such as nickel, stainless steel or polytetrafluoroethylene. In general, materials having a thermal conductivity of less than 70W/mK, preferably less than 20W/mK, are selected.

Advantageously, according to the invention, the walls 13 of the projecting portion are coated with a thin layer 3 of porous material.

A thin layer is generally understood to mean a layer less than 1mm thick.

The interface plane P is a plane parallel to YZ and adjacent to the projection tip 12, which plane coincides with the front face 20 of the primary capillary in the assembled state of the evaporator.

It will be noted that the wall 13 of the coated protruding portion defines the flow area of the steam channel 4 by the front face 20 of the primary capillary.

Returning to the lamina 3 of porous material, according to an exemplary embodiment , particularly shown in fig. 4, the thickness on the walls 13 of the projecting portions is not constant, preferably varying along the walls as one moves away from the primary capillaries, the thickest portion 31 is in contact with the primary capillaries at the interface 23 in the plane P near the tip of each projecting portion 12, and the thickness EC of said lamina decreases as one moves away from the primary capillaries, until near the groove bottom 41, the thickness of the end of the lamina, designated 32, is substantially zero.

Advantageously, the thickness EC of the thin layer is everywhere less than 0.5 mm.

According to another possibilities, it is possible to choose a value smaller than 0.2x W for the upper limit of the thickness EC.

In the preferred theoretical configurations, starting from the interface 23 in contact with the primary capillary 2, the axis L is defined along the wall 13 of the projecting portion, the thickness EC at the position of the abscissa L1 is EC1, and the thickness EC1 becomes smaller moving in the direction towards the groove bottom 41, wherein the thickness EC3 is substantially zero, or at least significantly smaller than the portion EC1 passing through the intermediate thickness EC 2.

Note that in the different figures, the bottom of the groove 41 is considered as "isolated". In fact, due to the machining constraints and/or to facilitate the creation of the lamina 3, there may be areas not covered by the lamina 3 of a size comparable to D3.

In the ideal case, compared with the material constituting the primary capillary 2, for example: copper, aluminum or nickel, the thin layer is obtained from a material having a better thermal conductivity, with a thermal conductivity greater than 180W/mK, preferably greater than 380W/mK.

Advantageously, the pore size of the thin layer is smaller than the pore size of the primary capillary; making it possible to feed liquid from the primary capillary and promote the release of vapour from the surface of the thin layer.

The base 10 of the heated element has a thickness H1, typically between 0.5mm and 5 mm.

It will be noted that the tips 12 of the projections are in contact with the primary capillary at a plane P having a surface area (D3xZ2) that is less than 20% of the effective surface area of the primary capillary.

As can be seen from fig. 3, the tip of the projecting portion 12 and the primary capillary are in continuous contact with the respective other portions in the direction Z2; in other words, the contact portion between the tip of the projecting portion and the lower surface of the primary capillary is not interrupted.

For the contact surface between the primary capillary and the lamella, on each side of the cross-section, we have a width marked D1:

D1＝EC1/cos(α).

thus, the total contact surface between the primary capillary and the coated heated plate can be represented by D2:

D2＝D1+D3+D1

note that D2 typically extends over 10% to 50% of the base width W. If the assembly of the primary capillary is completed at all the teeth by connecting rounded corners, it is not excluded to increase the above-mentioned amplitude to 80% (right side of fig. 10). This arrangement is very useful in situations where significant mechanical strength is required or where increased two-phase liquid drainage is desired.

Furthermore, D3<0.3 mm.

Furthermore, if the thin layer 3 between the tip and the primary capillary 2 has a thickness, it is possible to make D3 0, or there is no contact between the teeth and the primary capillary. Such an arrangement would make it possible to increase the insulating effect of the liquid transfer zone between the primary capillary and the lamella.

Figures 6 and 7 show the vaporization surface function of a thin layer 3 of porous material with a progressive cross-section, when the protruding portion 11 is very thick, its fin forming efficiency is close to 1 and its heat resistance is at least orders of magnitude lower than that caused by vaporization of the thin layer 3, as an approximation of , similar to considering only slight variations in the temperature of the protruding portion-trapezoidal fin.

The thermal resistance of a thin layer with liquid saturation or partial saturation is inversely proportional to its thickness, for example linearly varying between EC1 and EC3 (fig. 4). As a result, the local vaporization flow in layer 3 follows curve 61 shown in fig. 6.

Local flow (unit: W/cm) at the position of minimum thickness EC3²) Of great importance, in other words on the base of the trapezoidal toothing 11. Due to the proposed geometry, the heat flux density becomes smaller as the contact area 23 with the primary capillary is closer. In the example shown, corresponding to fig. 4, at the projection tip 12, the heat flux density is divided by 20 with respect to the flux on the wall, whereas in the prior art evaporators with straight projections or concave grooves, but without thin layers 3, the heat flux is multiplied by a factor greater than 1.

Thus, boiling at the interface between the projection tip 12 and the primary capillary 2 is avoided or greatly reduced. By these arrangements, it is achieved that a surface capable of handling more than an average of 50 watts/cm of the evaporator external surface is obtained²The heat flux of (a) evaporates the interface.

Advantageously, about 30,000W/(m) is obtained²K) Or the above heat exchange coefficient (reference: the contact surface of the heated plate).

The inventors were able to observe thermal energies in excess of 110W/cm2 per unit area (heated plate).

In fig. 7 it can be seen that the thin layer makes it possible to transfer a larger amount of liquid than the amount of liquid evaporated at the tooth tips 12. The liquid transmission rate in the lamina is as described in curve 62; curve 62 represents the ratio QLid (h)/QLiq (L1).

The abscissa of fig. 7 is the nominal height, in other words the ratio H/H2. H is a variable representing height relative to the base. H2 is the total height of the protruding portion.

The conduction flow qt (h) in the body of the tooth 11 follows, with respect to the nominal height, the curve marked 63; if the abscissa L2 is taken to correspond to the base of the projecting portion, the curve 63 represents the ratio QT (h)/QT (0) or QT (h)/QT (L2).

It will be noted that most of the heat output is transferred through the lower part of the teeth and through the thinnest part 32 of the lamella 3.

Variations in the proportions and properties of the thickness of the thin layer 3 and the presence of defects during the manufacturing process may result in variations in the profile. The permeability and distribution of the pores of the lamina (3) are therefore adapted to allow the vaporization close to the base (10) to define the vaporization in the primary capillary. Similarly, it is possible to vary the thickness of the thin layer non-linearly to improve hydraulic and/or thermal performance. The linear variation is merely an example and is a simplified case of the present invention.

It is noted that the lamina may have, intentionally or as a result of manufacturing defects, a double porosity, i.e. an th region of greater porosity compared to other regions of lesser porosity, without excluding, with the same spirit, the presence of discontinuities in the lamina 3, i.e. the absence of separate regions or grooves of the lamina 3 on the side walls 13 of the raised portion 11.

Furthermore, it will be noted that, for the assembly of the evaporator, the proposed trapezoidal cross section allows a secure transfer of mechanical forces, in particular compressive mechanical forces (assembly of the power supply module by screwing).

According to another embodiments shown in fig. 5, the of the evaporator is generally arranged as a cylinder, the base 10 is a cylinder which receives the flux Qin, however, a similar arrangement as described above and with appropriate modifications can be equally applied to the raised portion 11, the groove 4 and the lamella 3 the primary capillary tube 2 can be in the form of a tubular sleeve the tank 5 is formed by a central region of the cylindrical inner space.

Referring to fig. 8, each groove or each vaporization passage 4 is in fluid communication (vapor or liquid phase) with the collector passage 40, which itself is in communication with the evaporator outlet (labeled Vap _ Out) which is in communication with the external steam pipe 8.

According to another exemplary embodiments shown in fig. 9, the projecting part 11 is provided in the shape of a conical bolt or a pyramidal stud in a cross section similar to that of fig. 8 the steam channel 4 is formed by the spacing between the studs according to advantageous solutions, the reduced thickness from the top of the stud makes it advantageous in terms of the above-mentioned efficiency.

According to another embodiments not shown in the figures, if the evaporator is in the shape of a wafer or disk, the protruding portions may be formed in the shape of circular ribs.

FIG. 10 depicts two variations, on the left side of FIG. (10-L) and on the right side of FIG. (10-R).

On the right, according to another exemplary embodiments, the thickness EC of the lamellae is approximately constant. is the case, in this configuration, the thickness EC of the lamellae is chosen between 0.1mm and 0.8 mm.

In the contact portion with the primary capillary, a rounded corner area 39 shown with a dotted line area may be provided, which increases the area of contact with the primary capillary. In fact, it can be seen that the distance labeled D1' is significantly greater than the distance labeled D1.

At the left side 10L, according to another exemplary embodiments, the lamella thickness EC is constant, including the lower region 34 and the bottom of the depression 35 continuing to the left, a portion 36 covering the lower tooth wall and having the same thickness can be found.

possible solutions for forming a thin layer of constant thickness (fig. 10, "L" side) use a grid 38 in the form of a sheet of metal with a unidirectional frame, the grid being formed on the raised portion, including its sides, and in intimate contact with the heated element 1.

For this particular assembly process, the contact area with the lower region 34 may leave cavities with a generally triangular cross-section.

As far as the manufacturing method is concerned, the preparation of the primary capillaries 2 comprises, by non-exhaustive means, cutting of porous sheets of a chosen thickness to the appropriate dimensions (length and width). For the heated element 1 we first take a copper (or nickel, stainless steel or aluminium) plate of thickness H1+ H2 and then remove part of the material by means of electrical or conventional machining or pressing, stamping or punching to form the grooves and raised portions.

The two porous surfaces on the contact plane P are connected using diffusion bonding, for example by atmospheric plasma spraying or additive manufacturing (3D printing) or grid placement as described above to form a thin layer 3 of uneven thickness ( th example).

Assembly by press contact is another possibilities.

It should be noted that it is also possible for the lamella 3 to cover the tips 12 of the teeth before the assembly of the primary capillary 2.