WO2019122676A1

WO2019122676A1 - Heat exchanger having superposed spacer inserts

Info

Publication number: WO2019122676A1
Application number: PCT/FR2018/053360
Authority: WO
Inventors: Frédéric Crayssac; Raphaël FAURE; Nicolas Richet; Marc Wagner
Original assignee: L'air Liquide, Societe Anonyme Pour L'etude Et L'exploitation Des Procedes Georges Claude
Priority date: 2017-12-19
Filing date: 2018-12-18
Publication date: 2019-06-27
Also published as: EP3728978A1; FR3075335B1; EP3728978B1; FR3075335A1

Abstract

The invention relates to a heat exchanger of the type with brazed plates and fins comprising a plurality of plates arranged parallel to one another so as to define a series of passages (33) for the flow of a first fluid to be brought into heat exchange relationship with at least one second fluid, at least one passage (33) being formed between a successive first plate (6) and second plate (7) and comprising at least one first spacer element (221) extending opposite the first plate (6) and defining, within the passage (33), a first set of channels (26) for the flow of the first fluid, at least one second spacer element (222) extending opposite the second plate (7) and defining, within the passage (33), a second set of channels (27) for the flow of the first fluid, said first and second spacer elements (221, 222) being superposed in the height (H) of the passage (33), measured perpendicularly to the plates (6, 7). According to the invention, the channels (26) of the first set extend generally parallel to a first direction (z1) parallel to the first and second plates (6, 7) and the channels (27) of the second set extend generally parallel to a second direction (z2) parallel to the first and second plates (6, 7), the first direction (z1) forming, in cross section in a plane parallel to the first and second plates (6, 7), an acute angle (A) with the second direction (z2).

Description

Heat exchanger with stacked interlayers

The present invention relates to a heat exchanger of the plate and fin type and an intermediate element adapted to such an exchanger.

The present invention finds particular application in the field of gas separation by cryogenics, in particular the separation of air by cryogenics (known by the acronym "ASU" for air separation unit) exploited for the production of oxygen gas under pressure. In particular, the present invention can be applied to a heat exchanger which vaporizes a liquid flow, for example liquid oxygen, nitrogen and / or argon by heat exchange with a caloric gas, by example air or nitrogen.

If the heat exchanger is in the tank of a distillation column, it can constitute a vaporizer operating as a thermosiphon for which the exchanger is immersed in a bath of liquid descending the column or a vaporizer operating in vaporization with a film fed directly by the liquid falling from the column and / or by a recirculation pump.

The present invention can also be applied to a heat exchanger which vaporises at least one liquid-gas mixture flow rate, in particular a multi-component mixing flow rate, for example a mixture of hydrocarbons, by heat exchange with at least one another fluid, for example natural gas.

The technology commonly used for a heat exchanger is that of plate and finned aluminum exchangers or brazed waves, which allow to obtain very compact devices with a large exchange surface.

These exchangers comprise separating plates between which are inserted heat exchange structures, generally corrugated structures or waves, formed of a succession of fins or wave legs, thus constituting a stack of passages for the different fluids to be put in heat exchange relationship.

The performance of an exchanger is related to the heat exchange coefficient of the heat exchange structures in contact with the fluids. The heat exchange coefficient of a structure depends in particular on the nature of the material constituting it, the porosity of this material, its roughness and the flow regime of the fluids.

For example, documents US Pat. No. 2,782,009 A, EP 0 338 704 A1, FR 2 308 892 A1 or EP 1 172 625 A2 are known from different configurations of heat exchange structures. Exchanger passages including a superposition of exchange structures are also known. These structures form within the passages fluid flow channels that extend parallel to each other.

It is possible to modify the heat exchange coefficient of an exchange structure by modifying the geometry or physicochemical properties of its surface. This makes it possible to increase the effective surface of exchange and / or to modify the interactions between the fluid and the surface, by changing the properties of the surface considered as its wettability or its capacity to intensify the boiling of a fluid. We then speak of intensified surfaces.

For example, surface deposits of porous or relief-forming coatings may be made on the surface of structures, or else such surface conditions may be created by mechanical treatments or chemical etching.

Document WO-A-2005/075920 discloses various techniques for depositing porous coatings or reliefs on the surface of a wave for a heat exchanger.

WO-A-2004/109211 discloses a method of depositing a porous coating on the surface of a separator plate of a heat exchanger.

A problem that arises with the use of intensified surfaces by texturing in brazed aluminum exchangers concerns the assembly of elements comprising such surfaces during the manufacture of the exchanger.

Indeed, the connection of the constituent elements of the exchanger is carried out by brazing with use of a filler metal, called solder or brazing agent, the assembly being obtained by melting and diffusion of the brazing agent within parts to be brazed, without melting them. However, the presence of a porous coating or reliefs at the connection zone between the parts to be assembled is problematic, since the clearance between the parts to be assembled, is added the open porosity of the coating or cavities on textured surfaces. When it melts, the filler metal fills these pores or cavities before the clearance between the parts, which can cause defects in the brazed joint, such as porosity, lack of solder, or lack of joint. This affects the mechanical and / or thermal properties of the seal, and therefore those of the exchanger which are directly related to the quality of the brazed joint.

In an attempt to overcome these disadvantages, one solution is to effect the texturing of the heat exchange structures after soldering of these structures in the exchanger has been achieved.

However, it is difficult to access the channels formed by the exchange structures in the passages of the exchanger. It then becomes impossible to use mechanical texturing techniques or thermal spray coating techniques. Other surface treatment techniques are difficult to implement. For example, for the techniques involving prior stages of heat treatment or deposition of an impregnating layer to ensure the adhesion of the coating, it is the entire exchanger that must be treated. There is a risk of clogging the channels, debrushing parts of the exchanger or creating weak metallurgical phases and damaging the brazed matrix.

Moreover, it has been proposed to carry out surface texturations on the separating plates before brazing. But in this case, there is no heat exchange structure brazed to the plates and it is necessary to anneal the plates. However, the exchange structures also have a role of spacers. They contribute to the rigidity of the exchanger passages and to their compressive strength during vacuum brazing of the exchanger. In addition, the annealed plates lose their mechanical strength. It is then necessary to arrange additional reinforcing bars in the passages and to double the thickness of the plates.

Another solution is not to perform texturing on the element on the surface portions at which the brazed joint must be formed. However, this involves locally modifying the surface condition of the parts, which complicates the manufacturing process. For example, it is possible to hide the areas where soldering is to take place or to remove the coating from these areas. But these additional steps lead to complexification and difficulties of implementation.

A more general problem relates to the mechanical strength of the exchanger during its manufacture. Indeed, the passages of the exchanger are subjected to significant compressive forces during the vacuum brazing operation. In certain configurations, especially when using structures with low density of fins, the rigidity of the heat exchange structures arranged in the passages may be insufficient to ensure their compressive strength.

The present invention aims to solve all or part of the problems mentioned above, in particular to improve the mechanical strength of a heat exchanger type brazed plates and fins and improve the manufacture of such a heat exchanger when it presents exchange structures with improved thermal properties.

The solution according to the invention is then a heat exchanger of the type with brazed plates and fins comprising a plurality of plates arranged parallel to each other so as to define a series of passages for the flow of a first fluid to be connected to heat exchange with at least one second fluid, at least one passage being formed between a first plate and a second plate and comprising:

at least one first intermediate element extending facing the first plate and defining, within the passage, a first set of channels for the flow of the first fluid,

at least one second intermediate element extending facing the second plate and defining, within the passage, a second set of channels for the flow of the first fluid,

said first and second intermediate elements being superimposed in the height H of the passage, measured perpendicularly to the plates, characterized in that the channels of the first set extend generally parallel to a first direction z1 parallel to the first and second plates and the channels of the second set extend generally parallel to a second direction z2 parallel to the first and second plates, the first direction z1 forming, in section in a plane parallel to the first and second plates, an acute angle A with the second direction z2.

Depending on the case, the exchanger according to the invention may comprise one or more of the following technical characteristics:

the acute angle A is less than or equal to 30 °, preferably less than or equal to 20 °.

the passages extend over a length L, measured in a longitudinal direction z, preferably vertical during operation of the exchanger, the first direction z1 forming a first angle b with the longitudinal direction z and / or the second direction z2 forming a second angle α with the longitudinal direction z, the first and second angles b, a being less than or equal to 15 °, preferably between 1 and 10 °.

the first intermediate element comprises a first set of fins or legs of wave delimiting the first set of channels and the second intermediate element comprises a second set of fins or legs of wave delimiting the second set of channels, the fins or wavelength legs of the first set succeeding in a first lateral direction x1 parallel to the first and second plates and orthogonal to the first direction z1 and the fins or legs of the second wave succeeding in a second lateral direction parallel to the first and second plates and orthogonal to the second direction.

- The channels of the first set and the channels of the second intermediate elements respectively have a first height h1 and a second height h2, measured in a stacking direction y which is perpendicular to the plates, such that h1 + h2 = H.

each channel of the first set intersects at least one channel of the second set at a point of intersection.

the passage comprises several superimpositions of first and second intermediate elements succeeding one another along the longitudinal direction. the first and second intermediate elements comprising at least one surface texturization in the form of a porous structure or of reliefs formed on surfaces of the first and second intermediate elements,

the first intermediate element comprises at least one first assembly portion positioned against the first plate and comprising a first pair of opposite surfaces, one of the surfaces of the first pair being oriented towards the first plate and the other one of the surfaces of the first pair being oriented towards the first plate; surfaces of the first pair being oriented on the side of the second plate, and the second intermediate element comprising at least a second assembly portion positioned against the second plate and comprising a second pair of opposite surfaces, one of the surfaces of the second pair being oriented on the side of the first plate and the other of the surfaces of the second pair being oriented on the side of the second plate.

the first assembly portion is free of surface texturing on at least that of the surfaces of the first pair oriented on the side of the first plate,

the second assembly portion being free of surface texturing on at least the other of the surfaces of the second pair oriented on the side of the second plate.

the first assembly portion has the surface texturing on the surface of the first pair oriented on the side of the second plate.

the second assembly portion has the surface texturing on the surface of the second pair oriented on the side of the first plate.

the surface texturing is in the form of a porous structure having an open porosity of between 15 and 60% by volume, preferably an open porosity of between 20 and 45% by volume or in the form of reliefs defining, in section transverse, cavities open on the surface of the first and second intermediate elements.

the first and second intermediate elements are in the form of a first and a second corrugated product, each comprising a succession of wave legs alternately connected by wave-points and wave-bases, the first product being waveform comprising a first set of wave legs delimiting the first set of channels and the second corrugated product comprising a second set of wave legs defining the second set of channels.

the waves of the first corrugated product are positioned against the first plate.

the wavelets of the second corrugated product are positioned against the second plate.

- At least one wave base of the first corrugated product has at least one contact zone or quasi-contact with at least one wave base of the second corrugated product.

at least one wave vertex of the first and second corrugated products has two ends connected to respective wave legs separated by a first width L1, measured along the lateral direction x, and each wavefront of the first and second products corrugated material has a second width, measured in the lateral direction x, the ratio L2 / L1 between the second width and the first width being less than 1, preferably between 0.1 and 0.4, more preferably between 0, 1 and 0.35.

at least one wave base of the first corrugated product comprises a third pair of opposed surfaces, one of which is oriented on the side of the first plate, is free of surface texturing and the other oriented on the side of the second plate has texturing. of surface.

at least one wave base of the second corrugated product comprises a fourth pair of opposite surfaces, one of which is oriented on the side of the first plate has surface texturing and the other oriented on the side of the second plate is free of texturing. of surface.

The present invention will now be better understood from the description which follows, given solely by way of nonlimiting example and with reference to the attached drawings, among which:

Figure 1 illustrates an example of a heat exchanger according to the invention;

Figure 2 is a partial schematic view of an exemplary solder configuration in an exchanger according to the invention; Figure 3 shows two cross-sectional views of an assembly of spacers in a passage of an exchanger according to one embodiment of the invention;

Figure 4 shows a longitudinal sectional view of intermediate elements according to one embodiment of the invention;

Figures 5 and 6 illustrate further embodiments of the invention;

Figures 7 and 8 illustrate spacers elements according to one embodiment of the invention,

Figure 9 illustrates spacers according to one embodiment of the invention.

In a manner known per se, a heat exchanger comprises a stack of plates arranged parallel to one above the other with spacing and thus forming several series of parallelepipedal and flat shaped passages for the flow of a first fluid. and at least one second fluid to be in indirect heat exchange relationship via the plates. Preferably, the first fluid comprises a refrigerant to be vaporized at least partially.

Figure 1 schematically illustrates an example of passage 33 of a exchanger 1 of the evaporator-condenser type fed with liquid oxygen. This vaporizer-condenser vaporizes the liquid oxygen OL under low pressure (typically slightly higher than the atmospheric pressure) collected at the bottom of a column, by medium pressure nitrogen condensation (typically from 5 to 6 bars absolute) circulating in passages adjacent passages 33 (not shown) dedicated to the circulation of oxygen. The medium pressure nitrogen is most often taken in the gaseous state at the head of a medium pressure air distillation column to which the low pressure column mentioned above is connected. After passing and at least partial condensation in the vaporizer-condenser, this nitrogen is returned to the medium pressure column.

It is more specifically in the context of this application that the invention will be described later, it being understood that its application can be envisaged in other contexts, in particular with fluids of another nature. Thus, the exchanger 1 can vaporize at least one liquid-gas mixture flow rate, in particular a multi-component mixing flow rate, for example a hydrocarbon mixture, by heat exchange with at least one other fluid, for example natural gas.

In particular, the invention may relate to a method of heat exchange between a first fluid and at least a second fluid in a heat exchanger according to the invention, said first fluid flowing in the passage 33 at a lower pressure or equal to 5 bar, preferably a pressure of between 1 and 2 bar.

All or part of the vaporization passages 33 of the exchanger 1 are provided with intermediate elements 221 defining, within the passages 33, channels 26 for the circulation of liquid oxygen and can take different forms.

The intermediate elements 221 may have corrugated shapes, as shown in FIG. 7, and comprise wave legs 123 alternatively connected by wave-peaks 121 and wave bases 122. In this case, the term "fins The wave legs that connect the vertices and the successive bases of the wave.

The spacer elements 221 may take on other particular shapes defined according to the desired fluid flow characteristics. More generally, the term "fins" covers blades or other secondary surfaces of heat exchange, which extend between the primary surfaces of heat exchange, that is to say the plates of the heat exchanger, in the passages of the exchanger.

The spacer elements 221 are soldered to the separator plates of the exchanger. Advantageously, the bonding is carried out by vacuum brazing using a filler metal 30, referred to as solder or brazing agent, the assembly being obtained by melting and diffusion of brazing agent 30 in the parts to be soldered, that is to say in the base metal, without melting them.

FIG. 2 is a partial view of a first intermediate element 221 assembled to a first plate 6 adapted to define, in association with a another second parallel plate 7 (not shown), a passage 33 of the exchanger 1.

The first intermediate element 221 and the plate 6 respectively comprise assembly portions 121, 60 intended to be brazed with each other. The assembly portions 121, 60 are positioned against each other, preferably with a small gap between them in order to interpose the brazing agent 30. Typically the assembly portions 121, 60 may be those where the clearance between the parts 221, 6 is the smallest, typically the portions at which the parts 221, 6 are in contact with each other or in quasi-contact, that is to say with a very weak game existing between all or part of said portions, one with the other. Preferably, a small clearance is between 0 and 0.1 mm, more preferably between 0 and 0.05 mm.

Preferably, the plates 6, 7 of the exchanger are rolled plates comprising a central sheet 40, each face of which is coated with a layer 30. According to another embodiment, the brazing agent 30 may take the form of The coating layer 30 may be deposited by spraying or by brushing the brazing agent 30 in the form of a powder suspension containing the powder, a dispersing agent or a coating agent. , a binder, additives to control the viscosity.

Preferably, the brazing agent 30 has a thickness e of between 50 and 300 miti, preferably between 100 and 250 pm.

The brazing agent 30 is preferably formed of a metallic material having a lower melting temperature than the constituent materials of the parts 6, 221. The parts 6, 221 and 30 are preferably formed of aluminum alloy. The plates and the intercalary elements of the exchanger are advantageously formed of a first aluminum alloy of the 3XXX family, preferably of the 3003 type (ASME SB-2019 SECTION 2-B). The brazing agent 30 is formed of a second aluminum alloy, preferably an alloy of the 4XXX type (ASME SB-2019 SECTION 2-B), in particular of the 4004 type. As seen in cross section in FIG. 3, the exchanger according to the invention comprises a first intermediate element 221 and a second intermediate element 222 superimposed in the height H of a passage 33 for the first fluid. The first intermediate element 221 extends facing the first plate 6 and the second intermediate element 222 extends opposite the second plate 7. Preferably, the superposition of the first and second spacer elements forms a set of generally parallelepipedic shape .

According to the invention, the first intermediate element 221 defines a first set of channels 26 extending parallel to a first direction z1 and the second intermediate element 222 defines a second set of channels 27 extending parallel to a second direction z2. The first and second directions z1, z2 are parallel to the plates 6, 7 and form between them, in section in a plane parallel to the first and second plates 6, 7, an acute angle A with the second direction z2.

FIG. 3 thus shows an exemplary arrangement according to the invention according to two cross-sectional planes P1 and P2 arranged at different positions along the longitudinal direction z, that is to say in the length L of the passage 33. This The arrangement is also shown schematically in longitudinal section in a plane parallel to the plates 6, 7 in FIG. 4.

The arrangement of intermediate elements according to the invention promotes the compressive strength of the passages during vacuum brazing of the exchanger. In addition, it allows the use of spacers of reduced heights, which is interesting when it is desired to work with higher fin densities. In addition, channels of reduced height are more accessible, which facilitates the realization of surface textures when desirable.

In addition, having two spacers 221, 222 separate in the passage 33 of the exchanger, one extending opposite the first plate 6, and the other extending opposite the second plate 7, is particularly interesting when it is desired to use surface texturizing insert elements. There is indeed a greater degree of freedom as to the surfaces of the elements that can present texturing In particular, the surfaces of each element which are located opposite the plate to which this element is to be assembled may, in all or part, have surface texturing.

This makes it possible to maximize the internal surface portion of the channels 26, 27 formed within the passage 33 which may have surface texturing, while continuing to use the traditional methods of manufacturing soldered plate and fin heat exchangers since the joints brazing can be performed at surfaces without texturing.

Note that in the context of the invention, the acute angle A is non-impaired.

Preferably, the acute angle A is less than or equal to 30 °, more preferably less than or equal to 20 °. More preferably, the acute angle A is greater than or equal to 5 °, preferably greater than or equal to 10 °.

According to an embodiment illustrated in FIG. 4, the flow of the first fluid takes place generally along the longitudinal direction z, which is preferably vertical during the operation of the exchanger. The first direction z1 forms a first angle b with the longitudinal direction z and / or the second direction z2 forming a second angle α with the longitudinal direction z, the first and second angles b, a being less than or equal to 15 °, preferably between 1 and 10 °. Being specified that the first and second angles are not necessarily equal.

By using relatively low angles of inclination, the mechanical strength of the passage 33 is improved while limiting, or even avoiding, the risk of disturbing the flow of the first fluid or creating dead zones within the passage; that is, areas of fluid stagnation.

According to a variant illustrated in FIG. 5, one of the intermediate elements, the first one 221 in FIG. 5, comprises channels 26 which extend parallel to a first direction z1 which is parallel to the longitudinal direction z. In this case, the first angle a is equal to 0 °.

As illustrated in FIG. 4, the first intermediate element 221 may comprise a first set of fins or wave legs 123 delimiting the first set of channels 26 and the second intermediate element 222 may comprise a second set of fins or legs. wave 223 delimiting the second set of channels 27. The fins or wave legs 123, 223 form the side walls of the channels 26, 27 and extend generally along the first and second directions z1, z2. The fins or wave legs 223 of the first set succeeding one another in a first lateral direction x1 parallel to the plates 6, 7 and orthogonal to the first direction z1 and the fins or legs 223 wave of the second set succeeding in a second direction lateral x2 parallel to the plates 6, 7 and orthogonal to the second direction z2.

Preferably, the channels 26 of the first set and the channels 27 of the second set are arranged so that each channel 26 of the first set intersects at least one channel 27 of the second set at a point of intersection i, as illustrated in FIG. .

As can be seen in FIG. 3, the channels 26, 27 of the first and second assemblies may respectively have a first height h1 and a second height h2, measured in the stacking direction y perpendicular to the plates 6, 7, such as h1 + h2 = FI. Thus, the exchange structure formed by the superposition of the first and second intermediate elements 221, 222 extends globally from the first plate 6 to the second plate 7, the first and second intermediate elements coming at least partly to bear the pressure. one on the other, so as to stiffen the passage 33. Preferably, the first and second elements have the same height h1 = h2 = H / 2.

According to an embodiment illustrated in FIG. 6, the passage 33 comprises several superimpositions of first and second intermediate elements 221, 222 succeeding one another, preferably in juxtaposition, in the longitudinal direction z. By arranging several blocks of first and second intermediate elements in the length of the passage, it homogenizes its compressive strength.

The first and second directions z1, z2 may possibly vary according to the superposition 221, 222 considered. Figure 6 illustrates the case where the first and second directions z1, z2 are the same for each superposition. Advantageously, the first intermediate element 221 is intended to be assembled by soldering to the first plate 6 and the second intermediate element 222 is intended to be assembled by brazing to the second plate 7.

As seen in Figure 7, the first member 221 preferably includes at least a first assembly portion 121 positioned against the first plate 6 (not shown in Figure 4). The first assembly portion 121 comprises a first pair of opposed surfaces 121a, 121b, one 121 oriented towards the first plate 6 and the other 121b oriented towards the second plate 7.

FIG. 8 shows a second intermediate element 222 comprising at least a second assembly portion 321 positioned against the second plate 7. The second portion 321 comprises a second pair of opposed surfaces 321a, 321b, one 321a being oriented on the side of the first plate 6 and the other 321 b being oriented on the side of the second plate 7.

Note that the terms "positioned against" means an assembly portion juxtaposed to a plate, with or without clearance existing between all or part of the portion and the plate.

Optionally, the first and second intermediate members 221, 222 comprise at least one surface texturing 23 in the form of a porous structure or reliefs formed on surfaces of the first and second intermediate members 221, 222.

It should be noted that the intermediate elements may have one or more predetermined forms of surface texturization distributed over different zones of its surface, it being understood that surface texturing may as well be carried out in the surfaces of the constituent material of the interleaved elements. to be deposited there, that is to say to result from a contribution of additional material on the surfaces of the intermediate elements.

Preferably, the spacer elements 221, 222 each comprise a solid substrate, in particular a non-porous substrate, on which the texturing 23 is formed. Depending on the structures of the intermediate elements, the substrates may comprise one or more first and / or second assembly portions, the fins or wave legs. Note that each intermediate element is preferably monobloc, that is to say formed of a single piece.

In the context of the invention, the surface texturing 23 may result from a surface coating deposited on the element or a modification of the surface state of said element parts.

In particular, the surface texturing 23 may result from a surface coating deposited on the substrates of the spacer elements, in particular a coating deposited by a liquid route, in particular by dipping, spraying or electrolytically, by the dry route, in particular by deposition. Chemical Vapor Deposition (CVD) or Physical Vapor Deposition (CVD) or by thermal spraying, in particular by flame or plasma.

The modification of the surface state of said parts may be obtained by a chemical treatment or by a mechanical treatment, for example by sandblasting, grooving ....

Preferably, the surface texturing is formed from aluminum or an aluminum alloy comprising, for 100% of its mass, at least 80% by weight of aluminum, preferably at least 90%, more preferably at least 80% by weight. less than 99% aluminum.

According to a preferred embodiment, the surface texturing 23 is in the form of a porous structure, preferably a porous layer. The porous structure may for example be formed of a deposition of slightly sintered aluminum particles, entangled aluminum filaments, semi-fused aluminum particles bonded to each other, such as aluminum particles which are obtained after projection that is obtained by flame thermal projection.

Preferably, the surface texturing 23 has before brazing an open porosity of between 15 and 60%, preferably between 20 and 45%, more preferably an initial open porosity of between 25 and 35% (% by volume). It should be noted that the open porosity is defined as the ratio between the volume of the open pores, that is to say the pores communicating fluidly with the external environment in which the intermediate element in question is situated, and the total volume of the porous structure. The pores of the porous structure 23 preferably have a diameter between 1 and 200 miti, preferably between 5 and 100 pm. Noting that the pores are not necessarily circular in section but may have irregular shapes. The term "diameter" therefore also covers an equivalent hydraulic diameter which can be calculated from the measurement of the pressure drop experienced by a gas flow through the porous structure and by assuming that the pores have a regular shape, in particular a spherical shape, cylindrical, ...

We can also characterize the size of the pores by their volume. Preferably, the pores of the porous structure 23 have a volume of between 1000 and 1000 000 pm ³ . The pore volume may for example be determined by tomography or image analysis of polished sections of samples taken in a multitude of directions in space.

Alternatively, the surface texturing 23 may be in the form of reliefs, or patterns, printed or made in or on the material constituting the substrate of a spacer element. Preferably, these reliefs define, in cross section, cavities open on the surface of the element. For example, micro-reliefs or different size or morphology, such as grooves, discrete or uninterrupted, streaks, protuberances, ... may be formed or deposited on the surface of the element. In particular, the reliefs forming the surface texturing 23 may be made by laser or mechanical and / or chemical machining.

Advantageously, it will be possible to arrange interlayers 221, 222 with surface texturing in a zone 3 of a passage 33 of the exchanger into which the ascending oxygen penetrates, the elements thus having on the surface porosities or reliefs multiplying the priming for the formation of the oxygen gas bubble OG.

Preferably, at least one fin or wave leg 123 of the first assembly and at least one fin or wave leg 223 of the second assembly having said surface texturing 23, the first assembly portion 121 being free of texturing 23 at less on its surface 121 has oriented the side of the first plate 6 and said second assembly portion 321 being texturizing-free 23 at least on its surface 321 b oriented towards the second plate 7.

Thus, it preserves the wettability and good solderability of the surfaces of the first and second intermediate elements intended to be positioned against the adjacent plates to be assembled by soldering. During brazing, the distribution of solder at the joint can be controlled, resulting in a seal having good mechanical and thermal properties.

Preferably, the surfaces 6a, 6b, and 7a, 7b of the plates 6, 7 are free of surface texturing. This preserves the quality of solder joints formed with the plates.

Advantageously, the first assembly portion 121 has the surface texturing 23 on its surface 121b oriented towards the second plate 7, preferably all or substantially all of said surface 121b, and the second portion assembly 221 has the surface texturing 23 on its surface 321a oriented towards the first plate 6, preferably all or substantially all of said surface 321a.

Preferably, the first assembly portion 121 of the first intermediate element 221 is arranged between two successive fins or legs 123 of the first assembly, the surface 121 b oriented on the side of the second plate 7 having two ends each connected to a connecting surface 123a of each of the two wings or legs 123. The surface 121b of the first pair and said connecting surfaces 123a, 123a having the surface texturing 23, preferably all or almost all.

Thus, the fins or wave legs 123 delimit between them a channel 26 whose bottom, formed by the first assembly portion, and the side walls, formed by the two fins 123, has internal surfaces with an exchange coefficient improved thermal.

Similarly, the second assembly portion 321 of the second spacer element 222 may be arranged between two fins or legs 223 of the second assembly, the surface 321a of the second pair facing the first plate 6 having two ends each connected to a connecting surface 223a, 223b of each of the two wings or legs 223, said surface 321a of the second pair and said bonding surfaces 223a having surface texturing 23, preferably all or substantially all of them.

Thus, the fins or legs 223 delimit between them a channel 27 whose bottom, formed by the first assembly portion 121, and the side walls, formed by the two fins 223, has internal surfaces with a coefficient of improved heat exchange.

Preferably, the surfaces 123b, 223b opposite to said connecting surfaces 123a, 223a are free of surface texturing 23.

Note that in the context of the present invention, almost all of a surface, a face or an element means a portion representing at least 90%, preferably at least 95%, of preferably at least 98% of the area of this surface or face or the total area of this element.

According to a particular embodiment, the first and second intermediate elements 221, 222 are corrugated products each comprising a succession of wave legs 123, 223 alternatively connected by wave peaks 121, 321 and wave bases 122 , 322.

The following explanations are made with reference to Figures 7 and 8, it being understood that the intermediate elements 221, 222 may take any other suitable form and do not necessarily include all the features detailed below.

Figures 7 and 8 show cross-sectional views of corrugated products 221, 222. Each of the corrugated products 221, 222 comprise a plurality of elongate wave-shaped legs 123, 223 that extend parallel to each other and generally in a longitudinal direction. z. The wave legs follow one another in a lateral direction x, which is perpendicular to the longitudinal direction z, and are alternately connected by wave vertices 121, 321 and wave bases 122, 322.

According to the example illustrated in Figures 7 and 8, the vertices and the wave bases of the first and second corrugated products are of planar shape and extend parallel to each other and perpendicular to the wave legs 123, 223. The channels 26, 27 for the first fluid, which are formed between two successive wave legs and a top or a base arranged between said successive wave legs of each corrugated product, thus have cross sections of generally rectangular shape.

Figures 7 and 8 illustrate straight waves having wavelength legs 123, 223 with flat surfaces. Other configurations of intermediate elements 221, 222 are of course conceivable, including configurations of the type perforated straight wave, partial offset wave, wave wave or herringbone ("herringbone" in English).

The first and second corrugated products 221, 222 according to Figures 7 and 8 are visible in Figure 3 in the assembled state, that is to say mounted between a first and a second plate 6, 7 directly adjacent forming a passage 33 exchanger. The passage 33 is of generally parallelepipedal shape and configured to channel the first fluid parallel to the longitudinal direction z.

In operation, the first fluid flows over the width of the passage 33, measured along the lateral direction x, between an inlet and an outlet of the passage 33 situated at two opposite ends along the length of the passage 33, measured along the longitudinal direction z . The wave legs 123, 223 delimit, within the passage 33, a plurality of channels 26, 27 which extend parallel to the longitudinal direction z.

Preferably, the corrugated products 221, 222 are arranged in so-called "easyway" configuration in the passage 33, that is to say that the wave legs 123, 223 extend generally in the direction of flow of the first In operation, the direction of flow of the first fluid is preferably vertical, the direction of flow being ascending or descending.

The first corrugated product 221 extends generally parallel to the first plate 6 and has wave peaks 121 positioned against the first plate 6 to be assembled. The second corrugated product 222 extends generally parallel to the second plate 7 and has wave peaks 321 positioned against the second plate 7 to be assembled. For each corrugated product 221, 222, several pairs of wave legs 123, 223 extend from two adjacent wave vertices 121, 321 and are interconnected by wave bases 122, 322.

In the examples of Figures 7 and 8, the first and second corrugated products 221, 222 are free of surface texturing.

Advantageously, the first and second corrugated products 221, 222 may have at least one surface texturing 23 on all or part of their surfaces.

In the case illustrated in FIG. 3, the wave peaks 121 of the first corrugated product 221 are free of surface texturing 23 on their surface 121 oriented towards the first plate 6, which makes it possible to braze them solidly to a surface. reciprocal assembly portion on the first plate 6 during the manufacture of the exchanger, but have the surface texturing 23 on their surface 121 b oriented towards the second plate 7, which promotes the thermal performance of the exchanger .

The wave peaks 321 of the second corrugated product 222 are free of surface texturing 23 on their surface 321b oriented on the side of the second plate 7, which allows them to be soldered firmly to a reciprocal assembly portion on the second plate 7 during the manufacture of the exchanger, but have surface texturing 23 on the surface 321 a of the second pair oriented on the side of the first plate 6, which promotes the thermal performance of the exchanger.

As seen more clearly in Figures 4 and 5, the corrugated products 221, 222 include wave bases 122, 322 each having opposed surfaces 122a, 122b, 322a, 322b.

According to the embodiment illustrated in FIG. 3, each corrugated product 221, 222 is assembled only to one of the first and second plates 6, 7 by its respective wave peaks 121, 122.

Thus, the wave bases 122, 322 of the first and second corrugated products 221, 222 are not intended to be brazed with the plates 6, 7 and may advantageously have a surface texturing 23 on their surfaces 122b oriented on the side of the surface. second plate 7 with respect to the first corrugated product 221, and on their oriented oriented surfaces 322a on the side of the first plate 6 with respect to the second corrugated product 222. This makes it possible to maximize the surface area of the surface texturizing surfaces 23 present in the passage 23 and therefore to maximize the heat transfer efficiency within said passage 33 .

According to an embodiment illustrated in FIG. 9, the first and second corrugated products 221, 222 can each be formed from a flat product. Before shaping, the flat product comprises two opposite faces 221a, 221b or 222a, 222b. The surface texturing 23 is first formed on the flat product, and then the flat product is shaped, usually by stamping. Preferably the flat product, for example a sheet or strip, has a thickness of at least 0.15 mm, preferably between 0.2 and 0.5 mm.

Advantageously, at least one surface texturing 23 is formed on only one of said opposite faces 221a, 221b or 222a, 222b. Preferably, the opposite faces 221b, 222a on which the surface texturing 23 is formed have said texturing, in whole or almost all. The face 221b on which the texturing is formed gives rise, after shaping, to the surfaces 123a, 121b, 122b of the first corrugated product identified above. The face 222a on which the texturing is formed gives rise, after shaping, to the surfaces 123a, 321a, 322a of the second corrugated product identified above.

According to this embodiment, all the surfaces of the first product

221 located, in the mounted state, on the side of the second plate 7 thus have a surface texturing 23 and all the surfaces of the first product 221 located, in the mounted state, on the side of the first plate 6 are free of texturing 23. Similarly, all the surfaces of the second corrugated product 222 located, in the mounted state, on the side of the first plate 6 have surface texturing 23 and all the surfaces of the second corrugated product.

222 located, in the mounted state, on the side of the second plate 7 are free of surface texturing 23.

Thus, the manufacturing process is simplified since surface texturing can be formed or deposited on an entire face of the corrugated products without the need for an additional step of masking or post-processing. aiming at eliminating the surface texturing of the portions to be assembled since this face is not intended to form assembly portions with a plate. No texturing is performed on the other side of the corrugated products so as to preserve the quality of the solder joints of the corrugated products with the plates.

It is not necessary to perform surface texturing after mounting the intermediate elements 221, 222 in the exchanger since they already have texturing on the desired areas of the fins. It is thus possible to incorporate an intensified surface heat exchange structure in the exchanger while preserving the structural integrity of the matrix of the exchanger and of its internal channels.

Preferably, the first and second corrugated products 221, 222 have densities, defined as the number of wave legs per unit length measured along the lateral direction x, less than 18 legs per 2.54 centimeters, preferably less than 10 legs per 2.54 cm, more preferably less than or equal to 5 legs per 2.54 cm. Advantageously, the density can be between 1 and 5 legs per 2.54 centimeters. It should be noted that these density values are applicable to intermediate elements which are not necessarily corrugated products, the fins succeeding one another in the lateral direction x and the density then being defined as the number of fins per unit length, measured according to the lateral direction x.

The use of a relatively low density facilitates the deposition phase of the surface texturing on the fins or legs of wave, their surface being more accessible. In addition, the use of lower density spacer elements facilitates the removal of bubbles created in the surface texturing.

Preferably, each wave base 122 of the first corrugated product 221 has at least one zone of contact or quasi-contact with at least one wave base 322 of the second corrugated product 222. This improves the rigidity of the passage 33, while with the possibility of using corrugated products of relatively low density. Such contact areas or quasi-contact are visible in Figure 3 in the cross-sectional plane P1. By "quasi-contact" is meant that there is a very small clearance between all or part of said wave bases, preferably a gap of between 0 and 0.1 mm, more preferably between 0 and 0.05. mm.

Being noted that the bases can only be brought into contact without requiring brazing between them. This is possible especially when in operation, the channels 26, 27 channel a first fluid whose pressure is relatively low, typically less than or equal to 5 bar, preferably a pressure of between 1 and 2 bar, as is the case. in the oxygen passages of the vaporizer-condenser previously described.

According to one embodiment, for each of the first and second corrugated products 221, 222, at least one wave vertex 121, 321, preferably each wave vertex 121, 321, has two ends connected to wave legs. 123, 223 respectively separated by a first width L1, measured along the lateral direction x. At least one wave base 122, 322, preferably each wave base 122, 322, has two ends connected to respective wave legs 123, 223 separated by a second width L2, measured along the lateral direction x. It being noted that the widths L1, L2 correspond to the spacing between two successive wave legs, measured in the lateral direction x, typically in section in a median plane of the wave which is parallel to the plates

Preferably, the first and second corrugated products are configured so that the ratio L 2 / L 1 is strictly less than 1, preferably between 0.1 and 0.4, more preferably between 0.1 and 0.35.

It is also possible that the widths L1, L2 are equal to each other.

Thus, the first set of wave legs 123 and the second set of wave legs 223 each comprise a periodic arrangement of pairs of legs of wave, the period of this arrangement corresponding to the distance L1 + L2.

Preferably, the first width L1 is between 3 and 20 mm, preferably between 5 and 15 mm, and the second width L2 is between 1, 2 and 7 mm, preferably between 2 and 5 mm. It being specified that the first corrugated product may have widths and / or heights identical to those of the second corrugated product, but not necessarily.

Claims

1. Brazed plate and fin type heat exchanger comprising a plurality of plates arranged parallel to each other so as to define a series of passages (33) for the flow of a first fluid to be in heat exchange relationship with at least one a second fluid, at least one passage (33) being formed between a first plate (6) and a second plate (7) and comprising:

at least one first intermediate element (221) extending facing the first plate (6) and defining, within the passage (33), a first set of channels (26) for the flow of the first fluid,

at least one second intermediate element (222) extending opposite the second plate (7) and defining, within the passage (33), a second set of channels (27) for the flow of the first fluid,

said first and second spacers (221, 222) being superimposed in the height (H) of the passage (33), measured perpendicular to the plates (6, 7),

characterized in that the channels (26) of the first set extend generally parallel to a first direction (z1) parallel to the first and second plates (6, 7) and the channels (27) of the second set extend generally parallel to a second direction (z2) parallel to the first and second plates (6, 7), the first direction (z1) forming, in section in a plane parallel to the first and second plates (6, 7), an acute angle (A) with the second direction (z2).

2. Exchanger according to claim 1, characterized in that the acute angle (A) is less than or equal to 30 °, preferably less than or equal to 20 °.

3. Exchanger according to one of claims 1 or 2, characterized in that the passages (33) extend over a length (L), measured in a longitudinal direction (z), preferably vertical during operation of the exchanger, the first direction (z1) forming a first angle (b) with the longitudinal direction (z) and / or the second direction (z2) forming a second angle (a) with the longitudinal direction (z), the first and second angles (b, a) being less than or equal to 15 °, preferably between 1 and 10 °.

4. Exchanger according to one of the preceding claims, characterized in that the first intermediate element (221) comprises a first set of fins or wave legs (123) defining the first set of channels (26) and the second element insert (222) comprises a second set of fins or legs (223) delimiting the second set of channels (27), the fins or legs of wave (223) of the first set succeeding one another in a first lateral direction ( x1) parallel to the first and second plates (6, 7) and orthogonal to the first direction (z1) and the fins or legs of wave (223) of the second set succeeding one another in a second lateral direction (x2) parallel to the first and second plates (6, 7) and orthogonal to the second direction (z2).

5. Exchanger according to one of the preceding claims, characterized in that the channels (26) of the first set and the channels (27) of the second intermediate elements (221, 222) respectively have a first height (h1) and a second height. (h2), measured in a stacking direction (y) which is perpendicular to the plates (6, 7), such that (h1 + h2 = H).

6. Exchanger according to one of the preceding claims, characterized in that each channel (26) of the first set crosses at least one channel (27) of the second set at a point of intersection (i).

7. Exchanger according to one of the preceding claims, characterized in that the passage (33) comprises several superpositions of first and second intermediate elements (221, 222) succeeding in the longitudinal direction (z).

8. Exchanger according to one of the preceding claims, characterized in that the first and second intermediate elements (221, 222) comprising at least one surface texturing (23) in the form of a porous structure or reliefs formed on surfaces of the first and second intermediate members (221, 222),

9. Exchanger according to claim 8, characterized in that the first intermediate element (221) comprises at least a first assembly portion positioned against the first plate (6) and comprising a first pair of surfaces (121 a, 121 b). opposed, one (121a) of the surfaces of the first pair being oriented on the side of the first plate (6) and the other (121b) of the surfaces of the first pair being oriented on the side of the second plate (7). ), and the second intermediate element (222) comprising at least a second assembly portion (321) positioned against the second plate (7) and comprising a second pair of opposing surfaces (321a, 321b), one ( 321 a) the surfaces of the second pair being oriented on the side of the first plate (6) and the other (321 b) of the surfaces of the second pair being oriented on the side of the second plate (7), the first portion of assembly (121) being free of textura surface (23) on at least that (121a) of the surfaces of the first pair oriented on the side of the first plate (6) and the second assembly portion (321) being free of surface texturing (23) on at least the other (321 b) of the surfaces of the second pair facing the side of the second plate (7).

10. Exchanger according to one of claims 8 or 9, characterized in that the first assembly portion (121) has the surface texturing (23) on the surface (121 b) of the first pair oriented on the side of the second plate (7) and the second assembly portion (221) has the surface texturing (23) on the surface (321 a) of the second pair oriented on the side of the first plate (6).

1 1. Exchanger according to one of Claims 8 to 10, characterized in that the surface texturing (23) is in the form of a porous structure having an open porosity of between 15 and 60%, preferably an open porosity of between 20 and 60%. and 45% (% by volume) or in the form relief device defining, in cross-section, cavities open on the surface of the first and second spacer elements (221, 222).

12. Exchanger according to one of the preceding claims, characterized in that the first and second intermediate elements are in the form respectively of a first and a second corrugated products (221, 222) each comprising a succession of legs of wave (123, 223) alternately connected by wave peaks (121, 321) and wave bases (122, 322), the first wave product comprising a first set of wave legs (123) delimiting the first channel assembly (26) and the second corrugated product comprising a second set of wave legs (223) delimiting the second set of channels (27).

Exchanger according to Claim 12, characterized in that the wave peaks (121) of the first corrugated product (221) are positioned against the first plate (6) and the wave peaks (321) of the second corrugated product ( 222) are positioned against the second plate (7).

14. Exchanger according to one of claims 12 or 13, characterized in that at least one wave base (122) of the first corrugated product (221) has at least one contact zone or quasi-contact with at least one wave base (322) of the second corrugated product (222).

15. Exchanger according to one of claims 12 to 14, characterized in that at least one wave vertex (121, 321) of the first and second corrugated products (221, 222) has two ends connected to legs of respective waves (123, 223) separated by a first width (L1), measured in the lateral direction (x), and at least one wave base (122, 322) of the first and second wave products (221, 222) a second width (L2), measured in the lateral direction (x), the ratio (L2 / L1) between the second width and the first width being less than 1, preferably between 0.1 and 0.4, preferably still between 0.1 and 0.35.