WO2016059597A1

WO2016059597A1 - Heat exchanger

Info

Publication number: WO2016059597A1
Application number: PCT/IB2015/057935
Authority: WO
Inventors: Stéphane Colasson; Mathieu Mariotto; Guillaume MONTZIEUX
Original assignee: Commissariat A L'energie Atomique Et Aux Energies Alternatives
Priority date: 2014-10-15
Filing date: 2015-10-15
Publication date: 2016-04-21
Also published as: FR3027382A1; FR3027382B1; EP3207326A1; EP3207326B1

Abstract

The invention relates to a heat exchanger through which a heat transfer fluid flows, said exchanger comprising at least one three-dimensional structure defining surfaces for exchange with the fluid and triangular shaped channels for the passage of the fluid. According to the invention, at least one of the aforementioned channels, extending in a first direction, has a non-constant cross-section in this direction and in the direction of the thickness of the exchanger, so as to create turbulence in the flow of the fluid.

Description

HEAT EXCHANGER

The invention belongs to the technical field of heat exchangers.

Many heat exchanger structures are known. One can cite in particular document CN202734640 which describes a heat exchanger comprising a plurality of parallel micro-channels.

Thus, all the channels created in this exchanger are straight channels, with constant section.

Mention may also be made of document US7686070 which describes a heat exchanger comprising a channel for the passage of a heat transfer fluid and in which there are provided means creating turbulence inside these channels.

The exchanger described in US7686070 therefore has the advantage of creating turbulence inside the fluid passage channel. Thus, such an exchanger makes it possible to obtain larger heat transfers than in an exchanger with all the channels being straight, like the one described in the document CN202734640.

However, the structure described in US7686070 is relatively complex to achieve, the means creating the turbulence comprising a plurality of convolutions whose definition and manufacture are delicate.

The invention aims to overcome these disadvantages by providing a heat exchanger whose structure can generate significant heat transfer by creating turbulence, while being a simple and economical.

This exchanger can have many applications, such as the cooling of electronic components or power electronics, including embedded components that can be used in the aeronautics or aerospace field. This exchanger can also perform the function of a regenerative exchanger, for example for a Stihing type motor or for a magnetocaloric machine, such as a heat pump. In the first case, the fluid will be a gas and in the second case, a liquid.

Due to its compactness, this exchanger can also be used in the fields of refrigeration or domestic air conditioning.

Thus, the invention relates to a heat exchanger in which circulates a heat transfer fluid, this exchanger comprising at least a three-dimensional structure defining exchange surfaces with said fluid and triangular channels for the passage of said fluid in which at least one of said channels, extending in a first direction, has a non-constant section in this direction and according to the thickness of the exchanger, to create turbulence in the flow of said fluid.

Preferably, said at least one three-dimensional structure comprises at least two three-dimensional elements, each of them defining adjacent projecting portions extending in a second determined direction and in a period P, each projecting part being defined by two plane portions. forming an angle γ non-zero and connected by an edge, said at least two elements being located in the same plane and offset relative to each other in said second direction.

When the projections of said at least two three-dimensional elements are distributed in the same period P, the offset between said at least two elements is less than P / 2.

Preferably, this offset is less than P / 4.

In an alternative embodiment, the exchanger comprises a three-dimensional structure and a flat surface, in contact with the edges of the projecting portions of said structure.

In another variant embodiment, the exchanger comprises two three-dimensional structures assembled so that the projecting portions of one structure are nested in the projecting portions of the other structure, to make contact between the edges of a structure and planar parts of the other structure and vice versa.

In this second embodiment, the two three-dimensional structures may be identical and they are then arranged head to tail.

Moreover, the projecting parts have a section advantageously having the shape of a right triangle.

Finally, the exchanger according to the invention also comprises means for supplying fluid to said at least one three-dimensional structure and means for collecting said fluid after passing through said at least one structure.

The invention will be better understood and other objects, advantages and characteristics thereof will appear more clearly on reading the description which follows and which is made with reference to the accompanying drawings, in which:

FIG. 1 is a view from above of the heat exchanger according to the invention schematically illustrating the principle of the flow of the thermal transfer fluid in the exchanger,

FIG. 2 is a cross-sectional view of an exemplary embodiment of the exchanger according to the invention,

FIG. 3 is a view similar to FIG. 2 which illustrates an alternative embodiment of the heat exchanger illustrated in FIG. 2.

FIG. 4 is also a view similar to FIG. 2, illustrating another alternative embodiment of the heat exchanger according to the invention,

FIG. 5 comprises FIGS. 5a and 5b which illustrate two exemplary shapes of the projecting portions of the exchanger according to the invention,

FIG. 6 is a three-dimensional view illustrating the heat exchanger according to FIG.

FIG. 7 comprises FIGS. 7a and 7b which schematically illustrate two variants of fluid inlet / outlet means associated with the exchanger. The elements common to the different figures will be designated by the same references. Moreover, it is specified on each figure a direct orthogonal reference (O; X, Y, Z), of origin O.

Firstly, reference is made to Figure 1.

The arrow F designates the overall direction of the fluid flow inside the exchanger, the fluid being supplied to the inlet face of the exchanger.

Furthermore, the circulation of the fluid inside the exchanger 1 is carried out by means of channels extending substantially perpendicular to the arrow F, that is to say substantially perpendicular to the direction of the overall circulation of the fluid in the exchanger.

The circulation of the fluid in the channels is shown schematically by the arrows f ₁ , f ₂ and f ₂ 'in each half of the exchanger.

It should be noted that the arrows f ₂ and f ₂ 'respectively are oriented in the opposite direction to that of the arrows f 1'. These arrows show schematically the direction of the local flow of the fluid, which is substantially perpendicular to the overall flow of the fluid represented by the arrow F.

Reference is now made to FIG. 2 which illustrates an exemplary embodiment of a heat exchanger according to the invention.

Figure 2 is a cross section along the line 11-11.

This exchanger is formed of two three-dimensional structures 2 and 3 which are arranged between two flat walls (not shown in Figure 2).

In practice, each of these planar walls is in contact with the base 20, 30 of a three-dimensional structure 2, 3.

In the example illustrated in FIG. 2, the two three-dimensional structures 2, 3 are identical.

However, the invention is not limited to this embodiment and the two structures could be of different shape.

Structure 2 will now be described with reference to FIGS. 2 and 6. Thus, the structure 2 itself comprises two three-dimensional elements 21 and 22. These two three-dimensional elements 21, 22 are therefore located in the same plane. Indeed, they each have a wall forming the base 20 of the three-dimensional structure 2.

The invention is however not timed to this embodiment and a structure could comprise more than two three-dimensional elements.

These elements have an identical thickness E and are in contact with each other. Thus, the thickness of the exchanger is here equal to 2E.

These two three-dimensional elements are here identical.

However, the invention is not limited to this embodiment and the two three-dimensional elements could be of different shape.

Thus, the element 21 has protruding portions 211 which extend from the base 20 of the structure 2 and in the direction D.

As is illustrated in greater detail in FIG. 5a, a projecting portion 211 is defined by two plane portions 211a and 211b connected by an edge 211d and forming a non-zero angle γ between them.

These two plane portions 211a and 211b are themselves connected by a plane portion 211c which substantially coincides with the base 20 of the structure 2.

The angle β is defined between the planar portions 211b and 211c and the angle a between the plane portions 21a and 211c.

As shown in FIGS. 2 and 6, these projecting portions extend in a determined direction D and are adjacent to each other so that a planar portion 211d of a protruding portion is extended by a portion 211 has adjacent projecting portion.

Thus, the three-dimensional element 21 forms a serrated structure, the protruding parts being distributed according to a period P corresponding to their width, that is to say to the length of the portion 21c.

In the example illustrated in FIGS. 2, 6 and 5a, the protruding portions 211 present, in a transverse plane, the shape of a triangle rectangle, the angle β between the two planar surfaces 211b and 211c being equal to 90 °.

However, the invention is not limited to this embodiment, as will be seen in particular with regard to FIGS. 3 and 4.

The three-dimensional element 22 is offset with respect to the element

21 in the direction D in which the projecting parts extend.

In other words, the protruding portions 211 and 221 of each three-dimensional element 21 and 22 extend in the same direction D. However, the projecting portions 211 and 221 of the elements 21 and 22 do not coincide or overlap. not. On the contrary, each projecting portion 221 of the element 22 is shifted by a distance p with respect to a projecting portion 211 of the element 21. This distance p is called "no serration" and corresponds to the decay of a three-dimensional element with respect to the other.

As indicated above, the three-dimensional structure 3 is identical to structure 2. It will therefore not be described in detail.

It therefore comprises two three-dimensional elements 31 and 32, offset relative to each other by a distance p, the offset between the two elements of the structure 3 being substantially identical to the decay between the two elements of the structure 2. Another offset could be considered but an identical offset at the level of the structures is preferred.

Each of these elements 31 and 32 is formed of projecting portions 311 and 321 adjacent and distributed according to the period P. They also have the shape of a right triangle.

As illustrated in Figures 2 and 6, the two structures 2 and 3 are arranged one on the other, their projecting parts being opposite.

Moreover, these two structures 2 and 3 are arranged head to tail, so that the contact between the two structures 2 and 3 is formed between the edges of a structure and the planar portions of the other structure and vice versa.

Thus, FIG. 2 shows that the edges 211d and 221d of the protruding parts 211 and 221 of the structure 2 are in contact with the parts 31 31 and 321 of the structure 3. Similarly, the edges 31 1 ci and 321d of the projecting portions 31 1 and 321 of the structure 3 are in contact with the planar portions 211a and 321 of the structure 3 are in contact with the plane portions 211a and 221 has projecting portions 21 1 and 221 of the elements 21 and 22 of the structure 2.

The assembly between the structures 2 and 3 can be achieved by welding, brazing or bonding, depending on the constituent material of these structures.

Figures 2 and 6 show that this nesting between the two structures 2 and 3 allows to define triangular shaped channels and having different passage sections.

These channels are continuous insofar as the three-dimensional elements of each structure are in contact.

All these channels allow the passage of the transfer fluid and they extend in a direction substantially perpendicular to the direction D in which extend the projecting portions of the structures.

Thus, Figure 2 shows channels C of triangular shape having a passage section S which extend in the exchanger thickness by two channels c of passage section s, the surface s being less than the surface S. two channels c are therefore located in the background of a channel C, depending on the thickness of the exchanger. One of these two channels c forms a fluid inlet for the channel C and the other of these two channels c forms a fluid outlet for the channel C.

In the example illustrated in FIG. 2, channels C of passage section S are formed between elements 31 and 21, while channels c of passage section s are formed between elements 22, 32, 21 and 31.

As illustrated in Figures 2 and 6, thanks to this design, each channel C is in relation with four channels c defined in the exchanger, these channels for the circulation of the fluid inside the exchanger. Indeed, it should be noted that for a channel C as shown in Figure 2, i! there are also, according to the thickness of the exchanger, two channels c situated in the foreground of FIG. 2 (these two channels c are not visible in FIG. 2, because this figure is a plane section of Figure 1). The also, υη of these two channels c forms a fluid inlet for the channel C and the other of these two channels c forms a fluid outlet for the channel C.

Thus, according to the given direction D and the total thickness of the exchanger (2E), the channel for the passage of the fluid does not have a constant section since it consists of a channel C and two channels c in its extension.

In addition, the outline of the passage sections of all these channels defines an isosceles triangle.

The heat exchanger described with reference to Figures 2 and 3 thus comprises projecting portions having the shape of a right triangle. This makes it possible to define channels C having all the same passage section S and output channels c all having the same passage section s.

However, the invention is not limited to this embodiment.

Thus, the projecting parts of the three-dimensional elements of the exchanger may have a different section, as illustrated in FIGS. 3 and 4.

El is now referred to Figure 3 which illustrates another embodiment of the exchanger according to the invention.

This exchanger is always composed of two three-dimensional structures 4 and 5, here identical.

Each of these structures is composed of two three-dimensional elements 41, 42; 51, 52 which are also identical and offset from one another by a serration step p.

These elements will not be described in detail. Indeed, they are identical to those described with reference to Figure 2, except for the shape of the projecting portions of each of the three-dimensional elements.

We will essentially focus on the protruding portions 41 1 of the three-dimensional element 41 of the structure 4. As shown in Figure 5b, the sail portion 411 is defined by two planar portions 411a and 411b connected by a ridge 411d, these two parts pianes forming an undue angle y.

Moreover, the two planar portions 411a and 41b are connected by a flat portion 411c which substantially coincides with the base 40 of the element 4.

The angle φ between the piano parts 411b and 411c here is less than 90 °.

As for the exchanger illustrated in Figure 2, the two structures 4 and 5 are arranged one on the other, their projecting parts being opposite.

They are also arranged upside down, so that the ridges 4 d of protruding portions 411 of the element 41 of the structure 4 are in contact with the planar portions 511a of the projecting portions 511 of the element 51 of the structure 5. Similarly, the ridges 51 d of projecting portions 511 of the element 51 are in contact with the planar portions 411a of the protruding portions 411 of the element 41.

Similar contacts are established between the ridges and the respective planar portions of the element 42 of the structure 4 and the element 52 of the structure 5.

The assembly between the two structures 4 and 5 can also be achieved by welding, brazing or gluing, depending on the material constituting these structures.

FIG. 3 shows that this nesting between the structures 4 and 5 makes it possible to define triangular-shaped channels.

These channels extend in a direction substantially perpendicular to the direction D in which the projecting portions of the structures extend.

FIG. 3 shows channels C defined between elements 41 and 51 of structures 4 and 5. Channels C have a passage section S whose contour defines a triangle. Unlike the channels defined in the exchanger illustrated in Figure 2, this contour is not an isosceles triangle.

Furthermore, between the elements 42 and 52 are defined channels c having sections of passage si, s ₂ different.

Indeed, Figure 3 shows passage sections if and s ₂ of different shape and surface.

It remains that in this design, each channel C is in relation with four channels c, inside the exchanger. Thus, in the direction D and the total thickness of the exchanger, the channel for the passage of the fluid does not have a constant section.

The exchanger illustrated in FIG. 3 thus allows an additional degree of freedom over the value of the passage section of the channels c defined between the elements 42 and 52 of each structure.

This is achieved without changing the total thickness of the exchanger.

It is thus possible to reduce the size of the hydraulic diameter of these channels c. This results in an increase in the velocity of the fluid in the channels, it is then possible to reduce the size of the structure.

However, the shape of these projecting parts can not be any. In particular, the planar portions 41 1a, 41b and 41c of a projecting portion 411 should not define an isosceles triangle.

Indeed, in such a case, when the two structures are identical, once assembled, the contact between the two structures would not be established between the planar portions of a structure and the edges of the other structure. On the contrary, contacts would exist between the plane parts of each structure, no channel for the passage of the fluid can then be created.

In other words, the angle defined between the plane portions 41 1 a and 41 1 c of the projecting portion 41 1 should be strictly less than the angle β between the planar portions 41 1 b and 41 1. vs. In the exemplary embodiments of the exchanger illustrated in FIGS. 2 and 3, the angle β between the plane portions 211c and 211b or 411c and 41b is less than or equal to 90 °.

The invention is not imitated under this condition and FIG. 4 illustrates an exemplary embodiment of an exchanger according to the invention in which this angle β is greater than 90 °.

Like the exchangers previously described, the exchanger illustrated in FIG. 4 comprises two three-dimensional structures 6 and 7 each composed of two three-dimensional elements 61, 62 and 71, 72.

As before, the contact between the structures 6 and 7 is made between the edges of a structure and planar parts of the other structure.

This exchanger may be of interest for defining channels whose angles are more marked, that is to say angles between 0 and 90 °. This makes it possible to increase the capillary forces.

However, such an exchanger is of a more delicate embodiment. It is also more fragile, content of the compression efforts that it can undergo.

It will be understood that in the various embodiments of the heat exchanger according to the invention, the projecting parts extend according to a determined period P, this period corresponding to the length of a protruding part.

With reference to FIG. 5, this period P corresponds to the length of the plane portion 211c (FIG. 5a) or the flat portion 41c (FIG. 5b).

Moreover, to allow the creation of channels, it is necessary that the serration step p is not zero.

In addition, to allow the interconnection of the different channels created inside the exchanger of the exchanger and an optimal operation for channels c having an identical surface, it is also necessary that the serration step p is less than or equal to P / 2. Preferably, for the exchanger illustrated in FIG. 2, the serration pitch is less than P / 4.

It is recalled here that for the embodiment illustrated in Figure 2, the angle is equal to 90 ° and the projecting portions have a section forming a right triangle.

With this particular value of the serration step, the passage sections of the channels c will all have an identical surface.

Moreover, with this particular value, the singular pressure losses associated with these inputs / outputs will be the lowest. Indeed, the channels c having an identical surface at the inlet and outlet of the fluid, the flow velocity of the fluid is theoretically identical. As a result, turbulence and pressure drops are limited.

The various examples of exchanger according to the invention can be made of a metallic material, such as steel, stainless steel, aluminum or copper.

They can also be made of a polymer material or an active material such as a magnetocaloric. In this respect, Gadolinium-type materials or a material belonging to the family of LaFeSi-type alloys may be mentioned.

Moreover, the three-dimensional elements can be made by different techniques.

They can be obtained by direct machining of a material, in particular milling.

They can also be obtained by electro-erosion, by molding (using sand, a lost wax or a shell) or by plastic injection molding.

The heat exchanger according to the invention has many advantages.

First, the flow of fluid within a channel in the exchanger undergoes many changes of direction. Indeed, the section of the channel is not constant throughout the thickness of the exchanger. This results from the fact that the channels created between two elements of two three-dimensional structures have a section different from the other channels created between the two other elements of the two three-dimensional structures.

These changes of direction are likely to create turbulence and therefore greater heat transfer.

Moreover, within an exchanger according to the invention, the fluid can be homogeneously distributed because of the interconnection of the channels between them. This optimizes the heat transfer inside the exchanger.

In addition, these passage sections of different diameters create obstacles within the same channel, which increases the exchanges with the three-dimensional elements of the exchanger.

These channels also include baffles, which generates turbulence and promotes heat exchange.

It should also be noted that in the exemplary embodiments described with reference to FIGS. 3 to 4, the exchanger comprises two three-dimensional structures arranged facing one another so as to create channels for the passage of the transfer fluid. .

However, the invention is not imitated to these embodiments.

Indeed, an exchanger according to the invention could comprise only one three-dimensional structure, this three-dimensional structure being disposed between two flat walls.

In this configuration, the channels for the passage of the fluid would be created between the projecting portions of the three-dimensional structure and the wall of the exchanger with which protruding portions of the projections would be in contact.

This embodiment makes it possible to reduce the total thickness of the exchanger and thus to make it more compact. This may be essential in some applications. The advantages conferred by channels having a triangular contour crossing section will now be described in greater detail.

In general, this advantage exists for diphasic heat exchangers of the liquid / vapor or liquid / gas type.

Indeed, this particular shape of the passage section of the channels allows, by capillarity, to maintain the liquid film in the corners of the passage section and the vapor phase or the gas in the center of the channel.

Maintaining the liquid film wall prevents premature drying of the evaporator.

Thus, the overall flow of the transfer fluid within the exchanger is insensitive to interference or gravitational effects.

In other words, the exchanger according to the invention can function effectively independently of its orientation and independently of the movements to which it may be subject, these movements may result from an acceleration or a change of direction.

Of course, in the latter case, it is appropriate that the capillary force remains greater than the acceleration force to which the exchanger is subjected.

It may further be noted that the shape of the channels defined in the exchanger can be adapted by modifying the geometry of the protruding parts and the value of the serration pitch p.

This makes it possible to adapt the internal structure of the flow to the specific operating conditions of the exchanger and in particular to the transfer fluids used.

In practice, by modifying the serration step p, the openings c between the channels C are more or less important.

reference is now made to FIG. 7 which illustrates two variants of fluid inlet / outlet means associated with the exchanger.

Thus, Figure 7 schematically illustrates a heat exchanger 1 according to the invention which has a substantially planar shape. The reference 10 designates a transfer fluid supply box and the reference 1 1 a transfer fluid collection box, after passing through the exchanger. As indicated above with reference to FIG. 1, the fluid supplied by box 0 is distributed over the entire inlet face of the exchanger. The fluid passes through the exchanger through the channels to exit into the box 1 1 by the exit face of the exchanger and be evacuated.

In the example illustrated in Figure 7a these boxes have a cylindrical shape. However, they could also have a parallelepipedal shape,

Moreover, in the illustrated example, this box extends according to the total width of the exchanger.

In the example illustrated in Figure 7a, the two boxes 10 and 11 open on the same side of the exchanger.

FIG. 7b illustrates an alternative embodiment, in which the boxes 10 and 1 1 open on opposite faces of the exchanger.

Due to a different configuration between the inputs and outputs of the boxes illustrated in Figures 7a and 7b, the flow in the exchanger 1 may be more or less homogeneous over its entire surface.

Finally, an exchanger according to the invention may have an area of a few cm ² and 1 m ² . Its thickness can be between 1 mm and 1 m.

Moreover, the three-dimensional structures of the exchanger have a thickness of the order of millimeters or even less than one millimeter.

By way of example, for a protruding part of the type illustrated in FIGS. 1 and 5a, with a height h (corresponding to the length of the plane portion 211 b) equal to 0.5 mm and a hypotenuse h '(corresponding to the Since the length of the plane portion 211 a) is 1.5 mm, the hydraulic diameter of the channel C is about 0.35 mm.

The reference signs inserted after the technical characteristics appearing in the claims are only intended to facilitate understanding of the latter and can not limit its scope.

Claims

1. Heat exchanger in which circulates a heat transfer fluid, this exchanger comprising at least a three-dimensional structure (2 to 7) defining exchange surfaces with said fluid and channels (C, c) of triangular shape for the passage of said fluid, wherein at least one of said channels, extending in a first direction, has a non-constant section in that direction and according to the thickness of the exchanger, to create turbulence in the flow of said fluid.

2. The exchanger according to claim 1, wherein said at least one three-dimensional structure (2 to 6) comprises at least two three-dimensional elements (21, 22, 31, 32, 41, 42, 51, 52, 61, 62; 72), each of which defines adjacent projecting portions (211, 221; 311, 321; 411, 421; 511, 521; 611, 621; 711, 721) extending in a second determined direction and according to a period P, each protruding portion being defined by two planar portions forming a non-bare angle y! and connected by an edge, said at least two elements being located in the same plane and offset relative to each other in said second direction.

3. Exchanger according to claim 2 wherein the projecting portions of said at least two three-dimensional elements are distributed in the same period P, the offset between said at least two elements being less than P / 2.

4. Exchanger according to claim 3, wherein this offset is less than P / 4.

5. Exchanger according to one of claims 2 to 4, comprising a three-dimensional structure and a flat surface, in contact with the edges of the projecting portions of said structure.

6. Exchanger according to one of claims 2 to 4, comprising two three-dimensional structures assembled so that the projecting portions of a structure are nested in the projecting portions of the other structure, to make a contact between the edges one structure and the flat parts of the other structure and vice versa.

7. Exchanger according to claim 6, wherein the two three-dimensional structures are identical and are arranged head to tail.

8. Exchanger according to one of claims 2 to 7, wherein the projecting portions (21 1, 221; 31 1, 321) have a section having the shape of a right triangle.

9. Exchanger according to one of claims 1 to 8 comprising means (10) for supplying fluid to said at least one three-dimensional structure and means (11) for collecting said fluid after passing through said at least one structure.

10. Exchanger according to one of claims 2 to 9, wherein said at least two three-dimensional elements (21, 22; 31, 32; 41, 42; 51, 52; 61, 62; 71, 72) each have a wall forming a base (20) of said at least one three-dimensional structure.

1 1. An exchanger according to one of claims 2 to 10, wherein said at least two three-dimensional elements (21,22; 31,32; 41,42; 51,52; 61,62; 71,72) are in contact with each other. other in the heat exchanger thickness.