PLATE HEAT EXCHANGER

Abstract

The present invention relates to a pair of heat exchanger (AB) plates (A, B), comprising a first heat exchanger plate (A) and a second heat exchanger plate (B), which are disposed facing one another and are spaced apart from one another so as to define an internal volume that is able to form a channel for the flow of a first fluid (F.sub.1), and each comprising a central panel (A.sub.0, B.sub.0. Said central panels are quadrilateral or quadrilateral with optionally truncated, cut-off or rounded edges, and are flat and mutually parallel. Two opposite sides of the central panel (A.sub.0) of the first plate (A) are inclined with respect to said central panel (A.sub.0) in the direction of the second plate (B) and form first joining panels (P.sub.1, P.sub.2) that come into contact with the two corresponding flat opposite edges of the central panel (B.sub.0) of the second plate (B).

Claims

1. A pair of heat exchanger (AB) plates (A, B), comprising a first heat exchanger plate (A) and a second heat exchanger plate (B), which are disposed facing one another and are spaced apart from one another so as to define an internal volume that is able to form a channel for the flow of a first fluid (F.sub.1), and each comprising a central panel (A.sub.0, B.sub.0), said central panels being quadrilateral or quadrilateral with optionally truncated, cut-off or rounded edges, and being flat and mutually parallel, characterized in that two opposite sides of the central panel (A.sub.0) of the first plate (A) are inclined with respect to said central panel (A.sub.0) in the direction of the second plate (B) and form first joining panels (P.sub.1, P.sub.2) that come into contact with the two corresponding flat opposite edges of the central panel (B.sub.0) of the second plate (B).

2. The pair of plates (A, B) as claimed in claim 1, characterized in that said first joining panels (P.sub.1, P.sub.2) are mutually symmetric with respect to a first median axis (x) of the central panel (A.sub.0).

3. The pair of plates (A, B) as claimed in claim 1, characterized in that at least one, and in particular all, of the first joining panels (P.sub.1, P.sub.2) of the central panel (A.sub.0) of the first plate (A) comprise(s) a first part (P.sub.1A; P.sub.2A) extending from the central panel and a second part (P.sub.1B; P.sub.2B) extending from said first part, said first part forming an angle (α) with the central panel (A.sub.0) and said second part being parallel to said central panel (A.sub.0).

4. The pair of plates (A, B) as claimed in claim 3, characterized in that the angle (α) between the first part of the first joining panel (P.sub.1A; P.sub.2A) and the central panel (A.sub.0) is at least 45°, in particular between 80 and 110°.

5. The pair of plates (A, B) as claimed in claim 1, characterized in that the two other opposite sides of the central panel (A.sub.0) of the first plate (A) are inclined with respect to said central panel (A.sub.0) in the direction away from the first joining panels and form second joining panels (P.sub.3; P.sub.4), in particular in order to come into contact with the corresponding opposite edges of the central panel of a third plate.

6. The pair of plates (A, B) as claimed in claim 5, characterized in that one, and in particular all, of the second joining panels (P.sub.3; P.sub.4) of the central panel of the first plate (A) comprise(s) a first part (P.sub.3A; P.sub.4A) extending from the central panel (A.sub.0) and a second part (P.sub.3B; P.sub.4B) extending from said first part, said first part forming an angle (β) with the central panel (A.sub.0) and said second part being parallel to said central panel (A.sub.0).

7. The pair of plates (A, B) as claimed in claim 6, characterized in that the angle (β) between the first part of the second joining panels (P.sub.3A; P.sub.4A) and the central panel (A.sub.0) is at least 45°, in particular between 80 and 110°.

8. The pair of plates (A, B) as claimed in claim 1, characterized in that the two other opposite sides of the central panel (B.sub.0) of the second plate (B) are inclined with respect to said central panel (B.sub.0) in the same direction as the first joining panels (P.sub.1, P.sub.2) and form third joining panels (R.sub.3; R.sub.4), in particular in order to come into contact with the corresponding opposite edges of the central panel of a fourth plate.

9. The pair of plates (A, B) as claimed in claim 8, characterized in that one, and in particular all, of the third joining panels (R.sub.3; R.sub.4) of the central panel (B.sub.0) of the second plate (B) comprise(s) a first part (R.sub.3A; R.sub.4A) extending from the central panel (B.sub.0) and a second part (R.sub.3B; R.sub.4B) extending from said first part, said first part forming an angle (θ) with the central panel (B.sub.0) and said second part being parallel to said central panel (B.sub.0).

10. The pair of plates (A, B) as claimed in claim 6, characterized in that the second joining panels (P.sub.3; P.sub.4) and/or third joining panels (R.sub.3; R.sub.4) are different from the first joining panels (P.sub.1; P.sub.2), in particular in terms of width and/or of inclination with respect to their respective central panels.

11. The pair of plates (A, B) as claimed in claim 1, characterized in that the plates are joined together by welding between a flat edge of one of the plates (B) and a flat part of a joining panel (P.sub.1, P.sub.2) of the other plate (A).

12. The pair of plates (A, B) as claimed in claim 1, characterized in that the two plates are geometrically different than one another.

13. A stack of pairs of heat exchanger plates (A, B) comprising at least two successive pairs of spaced-apart plates as claimed in claim 1, denoted first pair of heat exchanger plates and the second pair of heat exchanger plates, wherein: said first pair and said second pair are disposed so as to be mutually parallel and to face one another, the space between the plates of each pair forming a channel for receiving a first flow of fluid (F.sub.1), the space between the first and the second pair of heat exchanger plates forms a channel for receiving a second flow of fluid (F.sub.2), said second pair being preferably identical to said first pair or being a mirror image of said first pair.

14. The stack of pairs of heat exchanger plates (A, B) as claimed in claim 13, characterized in that two successive spaced-apart pairs are connected laterally by closure means, said closure means comprising preferably an edge bar, a C-profile or U-profile cover plate, or a suitable flat cover plate.

15. A plate heat exchanger comprising pairs (A, B) of heat exchanger plates or stacks of pairs of heat exchanger plates as claimed in claim 1, said pairs or stacks of pairs being disposed in a frame.

16. A method for manufacturing a stack of at least two pairs (A, B) of heat exchanger plates as claimed in claim 1, said method comprising the following steps: preparing at least four plates, each having a four-sided central panel (A.sub.0, B.sub.0), on the one hand, for at least two of said central panels(A.sub.0), bending a first and a second opposite side so as to form first joining panels (P.sub.1; P.sub.2), said first joining panels each comprising a first part that is inclined with respect to the central panel, said first joining panels being preferably mutually symmetric with respect to a median axis (x) of the central panel (A.sub.0); on the other hand, optionally either bending said third and fourth sides of the at least two central panels in the direction away from the first and second joining panels so as to form second joining panels (P.sub.3; P.sub.4), said second joining panels comprising a first part, which is inclined with respect to the central panel, said joining panels being preferably mutually symmetric with respect to a median axis (y) of the central panel; or bending said first and second sides of at least two of the other central panels so as to form third joining panels (R.sub.3; R.sub.4), said third joining panels comprising a first part, which is inclined with respect to these two central panels, said second or third pairs of joining panels being preferably mutually symmetric with respect to the second median axis (y, y′) of the central panel in question; disposing the heat exchanger plates in two stacks, namely a first stack of mutually identical plates, and a second stack of mutually identical plates that are preferably different than the plates of the first stack, forming at least two pairs of plates, each pair being assembled from a plate from the first stack and another plate from the second stack, by fixing the first joining panels of one of the plates to the corresponding flat edges of the other plate, the space between the two plates of each pair forming a first fluid channel, joining together at least two pairs of plates thus formed, the space between the pairs of heat exchanger plates forming a second fluid channel, by fixing second joining panels (P.sub.3; P.sub.4) or third joining panels (R.sub.3; R.sub.4) of a plate of one pair to the flat edges of a plate of an adjacent pair or laterally via closure means.

Description

LIST OF FIGURES

[0053] FIG. 1a shows two heat exchanger plates A and B in an embodiment of a variant “having a pair of joining panels”.

[0054] FIG. 1b shows the corresponding pair of plates according to the invention when said plates A and B are assembled.

[0055] FIGS. 2a, 2b show two plates A and B in an embodiment of a variant “having two pairs of joining panels”.

[0056] FIG. 2b shows the pair of plates according to FIG. 2a when said plates A and B are assembled.

[0057] FIG. 2c shows two pairs of plates according to FIG. 2b that have been joined together.

[0058] FIG. 3a shows two plates A and B of a pair of heat exchanger plates according to the invention in another embodiment of the variant “having two pairs of joining panels”.

[0059] FIG. 3b shows the pair of plates in FIG. 3a when said plates A and B are assembled.

[0060] For the sake of clarity, the figures do not necessarily show the plates in the spatial position in which they can be assembled, and then in their use position. Specifically, throughout the figures, the plates are all shown on a vertical plane. The figures remain schematic depictions, the set of components shown is not necessarily to scale, and they have been simplified to make them easier to read.

DESCRIPTION OF THE EMBODIMENTS

[0061] Throughout the present text, the terms “supply” or “inlet” and “outlet” or “remove” and “into” or “out of” are used with reference to the direction in which the fluids flow.

[0062] Throughout the present text, the term “side” or “edge” of the central panel is used with reference to the periphery of the central panel, over a certain width, for example up to 5% or 10% of the width of the plate.

[0063] Throughout the present text, the term “mirror image” refers to symmetry with respect to a plane situated in the middle of the space separating the object from its image.

[0064] Throughout the present text, the “internal face” of a face means the face directed toward the other plate to which it is joined as a pair, and the “external face” of this plate is the face directed away from the other plate of the pair in question.

[0065] The invention can be used for example for plate heat exchangers operating on the cross-flow principle (known as “cross-flow exchangers), in which the fluids flowing over the two faces of each plate are directed substantially perpendicularly to one another. The invention can also be used for plate heat exchangers operating on a counter-current principle, in which the fluids flowing over the two faces of each plate are directed in substantially opposite directions (known as “counter-current exchangers”). The invention can also be used for plate heat exchangers operating on a co-current principle, in which the fluids flowing over the two faces of each plate are directed in substantially the same direction. The invention can also be used for heat exchangers of the plate type operating using other flow principles.

[0066] The direction of flow of the fluids is determined via the design of the plates and the manner in which they are connected by the joining panels. It may be modified by baffles disposed in certain flow channels for the fluid, in particular one channel in two. The baffles start downstream of the fluid inlet zones between the plates, and extend as far as the fluid outlet. For example, for a co-current exchanger, the baffles make it possible, downstream of the fluid inlet zone, to first modify the direction of flow of the fluid by substantially 90° in order that the fluid flows in the same direction as the fluid in the following channel, and then the baffles allow a second modification of the direction of flow of the fluid by 90° in order that the fluid flows in the direction of the outlet zone of the channel.

[0067] The invention is particularly suitable for heat exchange between two fluids, in particular two gases, but may also be used for exchanges of heat between two liquids or between a liquid and gas.

[0068] The invention is more particularly suitable for exchanges between two gases, in particular gas flows at the inlet and outlet of a single piece of equipment, for example the air that is to be carried to a furnace and the flue gases from the same furnace or, similarly, the hot stream coming from a NOx reduction system and the cold stream heading toward the same NOx reduction system.

[0069] A plate heat exchanger according to the invention can be used for fluids operating at a pressure ranging from the total vacuum pressure up to 1.5 MPa, preferably from 0.01 to 1.0 MPa, and more preferably from 0.01 to 0.6 MPa.

[0070] A plate heat exchanger according to the invention may be made up either of channels of uniform height or of channels with different heights on each circuit. Correspondingly, the height of the first joining panel and the heights of the second and of the third joining panel, where applicable, may be similar or different.

[0071] The height of the channels (the spacing between two consecutive plates) can be determined according to the service conditions. Typically, it may range from 5 to 30 mm, in particular 5 mm, 10 mm, 15 mm, 20 mm, 30 mm, or any appropriate height.

[0072] The width of the heat exchanger plate according to the invention may typically be between 1000 mm and 2000 mm, preferably between 1300 mm and 1700 mm. The length of the heat exchanger plate according to the invention may typically be between 1000 mm and 7500 mm, preferably between 1500 mm and 7000 mm.

[0073] The thickness of the plate may be between 0.6 mm and 6 mm, preferably between 1.5 mm and 2.0 mm.

[0074] The central panel of the heat exchanger plate according to the invention may have any appropriate shape, for example trapezoidal, hexagonal or quadrilateral. The central panel is more preferably quadrilateral, in particular rectangular or square, optionally with truncated corners.

[0075] The central panel comprises a first face (or lower face) and a second face (or upper face) opposite to the first face. The terms “lower” and “upper” therefore refer, by convention, to a panel disposed on a horizontal plane.

[0076] The first and the second face may be flat but may also locally have reliefs, grooves or protrusions.

[0077] Advantageously, protrusions (dimples) may be added to or pressed into the central panel of the plates. Dimples may be employed on one face of the plate or on both faces of the plate, with several arrangements depending on the characteristics of the plate and the use of said dimples. The dimples may be used as spacer elements and are intended to minimize the deformations of the plates when they are stacked on top of one another. Simple or double dimples are typically distributed over the surface of the central panel of the heat exchanger plates.

[0078] Fins shaped as a hairpin or as a pin (“pin fins”) may also possibly be welded to the central panel of the heat exchanger plate according to the invention, using resistance welding.

[0079] According to one preferred embodiment of the invention, the heat exchanger according to the invention comprises a first channel intended to receive a first fluid situated between the two heat exchanger plates of a single pair of plates according to the invention. Said two plates are mechanically connected by the two first joining panels of the first plate.

[0080] According to one preferred embodiment of the invention, the heat exchanger according to the invention comprises a second channel intended to receive a second fluid situated between two consecutive pairs of plates.

[0081] Advantageously, closure means may be used where applicable to close the lateral sides of the second canal and to seal the canal. Advantageously, said closure means may be mechanically connected to the plates by any means known to those skilled in the art, for example by welding, in particular by seam welding or by bolting.

[0082] In the embodiment in which each pair of plates comprises only one pair of joining panels, and therefore on only one of the plates of the pair, the second channel may advantageously be provided with means for closing its lateral side between two successive pairs of plates. These closure means may be edge bars or dedicated cover plates (cover parts) or any other equivalent means. The cover plates may be manufactured in one or more pieces, some in the shape of a C or of a U or of any arbitrary profile that allows the second plate of the first pair to be joined to the first plate of the second pair.

[0083] As regards the embodiment of the invention in which each pair of plates comprises two pairs of joining panels, that is to say in which one of the plates comprises one pair of joining panels, namely the first joining panels as described above, and in which the same plate or the other plate comprises another pair of joining panels, namely the second or third joining panels as described above: in this case, each pair is joined to the other by the second or third pairs of joining panels. In addition, closure means may advantageously be provided, disposed longitudinally in the direction of flow of the second fluid (the one circulating between two assembled pairs of plates) at the inlet and at the outlet of the second channel. These closure means may be a polygonal cover plate having a suitable shape.

[0084] Furthermore, the first and second channels intended to receive the fluid(s) either may be completely empty (“free” channel) or may comprise mechanical reinforcement means, such as connecting bars.

[0085] Advantageously, spacer elements (spacers) manufactured for example from strips, profiles, dimples or pin fins may be inserted into at least one/each channel in order to ensure the spacing between the plates. They may be loose or may be spot welded in place or be held in place by profiled U-shaped clamps at the supply and discharge points.

[0086] Advantageously, each of the joining panels comprises a part, in particular a single part, or comprises several parts extending successively from the central panel of the plate, and this or these parts are preferably all flat or substantially flat (with possible rounded portions in the transition/bend zones between the central panel and the part or the first part, and between two successive parts when the panel comprises several of them). In the latter case, the last part, farthest away from the central panel, is flat and parallel to the planes of the central panels, in order to maximize the surface areas in contact forming the join between two plates, and therefore to make them easier to fix together, the mechanical securing thereof.

[0087] The joining panels are preferably obtained through operations of bending the plates, but may be obtained in some other way, and even be attached to the central panels by different conventional fixing means.

[0088] According to one embodiment of the invention, each of the joining panels may be mechanically fixed to the central panel of the adjacent plate by any conventional technique, typically by welding.

[0089] Advantageously, the second part of each of the joining panels may be large enough to allow mechanical fixing of the second part to the central panel of the adjacent plate by a conventional means known to those skilled in the art.

[0090] According to a first variant, the second joining panels may be oriented with respect to the plane of the central panel, with an angle β of between 10° and 90°, preferably between 20° and 60°, and more preferably between 30° and 50°, or with an angle β of between 60° and 120°, preferably between 70° and 110°, and more preferably between 80° and 100°.

[0091] Preferably, the second part of each joining panel, when it comprises two parts, may extend from the first part of the joining panel parallel to the plane of the central panel, said second part either being oriented toward the interior of the space between two plates of a pair (which will act as flow channel for a fluid) of the channel or toward the outside, on the other side of this space.

[0092] Each of the joining panels may preferably be formed in a single step, by deformation/bending. The deformation may be obtained by press-forming and/or by bending. A series of steps of deforming the flat metal sheet may be required to form a series of lateral joining panels on a single plate (one or two pairs of panels).

[0093] In one embodiment of the invention, different zones of the central panel of the heat exchanger plates may be provided with a layer of insulation having a part made of metal plate parallel to the central panel, with air between the metal-plate part and the central panel. Said layer of insulation may allow the wall temperature of the heat exchanger plate to be locally modified and may typically be employed in the coldest zones of the cold channel. An example thereof is described in the patent application CZ298773.

[0094] According to another embodiment of the pair of two heat exchanger plates according to the invention, an end piece or “ferrule” may be mounted over the top of the edges of the two adjacent plates welded together, and act as a shield protecting the join. The ferrule is typically made from a piece of sheet metal bent in such a way as to be able to cover the welded join. The ferrule may be welded to each of the two plates.

[0095] The heat exchanger plate according to the invention may be formed of a single piece, usually by a single-step deformation of a flat metal sheet made of a weldable material, for example a plate made of steel, for example of stainless steel.

[0096] Note that the (one/plurality of/all of the) heat exchanger plate(s) according to the invention may also be manufactured by assembling several independent plate parts, using conventional assembly means.

DESCRIPTION OF THE FIGURES

[0097] The reference signs used in the figures are given below with reference to the components to which they refer:

[0098] A—Heat exchanger plate A

[0099] B—Heat exchanger plate B

[0100] A.sub.0—Central panel of plate A

[0101] B.sub.0—Central panel of plate B

[0102] A.sub.1, A.sub.2, A.sub.3, A.sub.4—sides of the central panel

[0103] A.sub.0, B.sub.1, B.sub.2, B.sub.3, B.sub.4—sides of the central panel B.sub.0

[0104] P.sub.1—first joining panel of A on the side A.sub.1

[0105] P.sub.2—second joining panel of A on the side A.sub.2

[0106] P.sub.3—third joining panel of A on the side A.sub.3

[0107] P.sub.4—fourth joining panel of A on the side A.sub.4

[0108] R.sub.3—third joining panel on B on the side B.sub.3

[0109] R.sub.4—fourth joining panel on B on the side B.sub.4

[0110] P.sub.1A—first part of the first joining panel P.sub.1

[0111] P.sub.1B—second part of the first joining panel P.sub.1

[0112] P.sub.2A—first part of the second joining panel P.sub.2

[0113] P.sub.2B—second part of the second joining panel P.sub.2

[0114] P.sub.4A—first part of the fourth joining panel P.sub.4

[0115] P.sub.4B—second part of the fourth joining panel P.sub.4

[0116] R.sub.3A—first part of the third joining panel R.sub.3

[0117] R.sub.3B—second part of the third joining panel R.sub.3

[0118] R.sub.4A—first part of the fourth joining panel R.sub.4

[0119] R.sub.4B—second part of the fourth joining panel R.sub.4

[0120] The reference signs are retained from one figure to another to denote the same components.

[0121] FIG. 1a shows two heat exchanger plates A and B according to an embodiment of a variant “having a pair of joining panels”, in which the plate B is flat, that is to say does not have a joining panel. It shows an exploded view of the two mutually facing plates that are oriented with respect to one another in the manner that they will adopt once assembled as shown in FIG. 1b.

[0122] The central panel A.sub.0 is rectangular in shape and has four sides numbered A.sub.1, A.sub.2, A.sub.3 and A.sub.4. A.sub.1 and A.sub.2 are two opposite sides. A.sub.3 and A.sub.4 are two other opposite sides. All the parts of the plate B are numbered in the same way, with B.sub.0 being the central panel and B.sub.1, B.sub.2, B.sub.3, B.sub.4 its four sides.

[0123] The central panel A.sub.0 is provided with a (first) pair of joining panels, namely two joining panels, respectively P.sub.1 on the side A.sub.1 and P.sub.2 on the opposite side A.sub.2, which are mutually symmetric with respect to a first median axis x of the central panel A.sub.0. In the embodiment illustrated in FIG. 1a, each of the joining panels P.sub.1 and P.sub.2 is formed of two parts, a first part, P.sub.1A and P.sub.2A, respectively, forming an angle α with the central panel A.sub.0 and a second part, P.sub.1B and P.sub.2B, respectively, which is parallel to the central panel A.sub.0. Each joining panel is connected by a bend line to the central panel A.sub.0, but could also have been supplied as a second component and have been fixed/attached to the central panel. Each two-part joining panel is preferably formed in a single pass, by deformation of the plate A. The first and the second joining panels P.sub.1 and P.sub.2 are oriented at an angle of around 75° with respect to the plane of the central panel A.sub.0.

[0124] The heat exchanger plate B does not have a joining panel and is substantially flat. The two central panels A.sub.0 and B.sub.0 face one another.

[0125] FIG. 1b illustrates a schematic perspective view of the two plates A and B of FIG. 1a as are disposed with respect to one another once assembled and mechanically connected at the first pair of joining panels P.sub.1 and P.sub.2 of the plate A in order to form a pair of heat exchanger plates according to one embodiment of the invention.

[0126] The two plates of FIG. 1a have been superposed so that they can be mechanically connected. The “internal face” of the plate A faces the “internal face” of the plate B. The first joining panel P.sub.1 of the plate A is welded at its second part P.sub.1B to the plate B on the flat edge of the side B.sub.1 of the central panel B.sub.0. Similarly, the second joining panel P.sub.2 of the plate A is welded at its second part P.sub.2B to the plate B on the flat edge of the opposite flat side B.sub.2 of the central panel B.sub.0.

[0127] The space thus formed between the plate A and the plate B constitutes a first channel of the heat exchanger made up of the pair of plates according to the invention, in which a first fluid F.sub.1 can flow. The first channel has a flow cross section that is trapezoidal, and said cross section is in this case the same along the entire length of the channel.

[0128] FIGS. 2a and 2b show a perspective view of two plates A and B, respectively separately and then assembled, according to a first embodiment of a variant “having two pairs of joining panels”, in which the exchanger plate A is provided with two pairs of joining panels, inclined in opposite directions, and in which the exchanger plate B does not have a joining panel.

[0129] In FIG. 2a, the central panel A.sub.0 of the plate A is provided with two pairs of joining panels:

[0130] on the one hand, the first joining panels P.sub.1 on the side A.sub.1 and P.sub.2 on the opposite side A.sub.2, which are mutually symmetric with respect to the median axis x of the central panel A.sub.0 and which are oriented toward the internal face of the plate A (analogously to the joining panels of FIGS. 1a, 1b);

[0131] on the other hand, the second joining panels P.sub.3 on the side A.sub.3 and P.sub.4 on the opposite side A.sub.4, which are mutually symmetric with respect to the second median axis y and which are oriented toward the external face of the plate A. The median axes x and y are perpendicular to one another.

[0132] The first joining panels P.sub.1 and P.sub.2 are made up of two parts, a first part, P.sub.1A and P.sub.2A, respectively, forming an angle α with the central panel A.sub.0, and a second part, P.sub.1B and P.sub.2B, respectively, which is parallel to the central panel and which extends toward the outside of the panel.

[0133] Similarly, the second joining panels P.sub.3 and P.sub.4 are made up of two parts, a first part, P.sub.3A and P.sub.4A, respectively, forming an angle β with the central panel and a second part, P.sub.3B and P.sub.4B, respectively, which is parallel to the central panel plate but which extends toward the inside of the panel. The first joining panels P.sub.1 and P.sub.2 are oriented toward the internal face of the plate B at an angle of around 75° with respect to the plane of the central panel A.sub.0. The second joining panels P.sub.3 and P.sub.4 are oriented toward the external face of the plate A at an angle β of around 90° with respect to the plane of the central panel A.sub.0. The joining panels are preferably formed in a single pass, by deformation. The deformation may be obtained by press-forming and/or by bending, after the corners have been cut.

[0134] The heat exchanger plate B does not have a joining panel and is substantially flat. The two central panels A.sub.0 and B.sub.0 face one another.

[0135] FIG. 2b illustrates a schematic perspective view of the two plates A and B of FIG. 2a once assembled and mechanically connected at the first joining panels P.sub.1 and P.sub.2 of the plate A in order to form a pair of heat exchanger plates.

[0136] The two plates have been superposed so that they can be mechanically connected. The “internal face” of the plate A faces the “internal face” of the plate B. The joining panel P.sub.1 of the plate A is welded at its second part P.sub.1B to the plate B on the flat side B.sub.1 of the central panel B.sub.0. Similarly, the joining panel P.sub.2 of the plate A is welded at its second part P.sub.2B to the plate B on the opposite flat side B.sub.2 of the central panel B.sub.0.

[0137] The channel formed between the plate A and the plate B constitutes a first channel of the heat exchanger made up of the pair of plates according to the invention, in which a first fluid F.sub.1 can flow. The first channel has a flow cross section that is trapezoidal, and said cross section is the same along the entire length of the channel.

[0138] As shown in FIG. 2c, the second joining panels P.sub.3 and P.sub.4 of the plate A make it possible to combine the plate A with a third exchanger plate, preferably identical to the plate B, which would be positioned next to the external face of the plate A, in order to create, between the third plate and the plate A, a second space defining a channel in which a second fluid F.sub.2 can flow. The second channel has, in this embodiment, a rectangular flow cross section. FIG. 2c shows plates that have, on their surface, above-mentioned “dimples”, and, by way of dashed lines, spacers intended to ensure a constant spacing between the two central panels, in this case in the form of profiles. These elements remain optional but may prove useful in particular with plates of large dimensions.

[0139] FIG. 3a shows two plates A and B of a pair of heat exchanger plates according to the invention in another embodiment of the variant “having two pairs of joining panels”, in which the exchanger plate A is provided with a (first) pair of joining panels, and in which the exchanger plate B is also provided with a (third) pair of joining panels. FIG. 3b shows the pair of plates when said plates A and B are assembled.

[0140] The central panel A.sub.0 of the plate A is provided with a first pair of joining panels: P.sub.1 on the side A.sub.1 and P.sub.2 on the opposite side A.sub.2, which are mutually symmetric with respect to the median axis x of the central panel A.sub.0 and which are oriented toward the internal face of the plate B, as in FIGS. 1a-1b above.

[0141] The central panel B.sub.0 of the plate B is provided with a third pair of joining panels: the joining panels R.sub.3 on the side B.sub.3 and R.sub.4 on the opposite side B.sub.4, which are mutually symmetric with respect to the median axis y′ of the central panel B.sub.0 and which are oriented toward the external face of the plate B. As in FIG. 2a above, the median axes x and y′ are perpendicular to one another, but in this case they are realized on two different, mutually parallel plates and not on one and the same plate. In this embodiment, the first joining panels P.sub.1 and P.sub.2 are made up of two parts, a first part, P.sub.1A and P.sub.2A, respectively, forming an angle α with the central panel, and a second part, P.sub.1B and P.sub.2B, respectively, which is parallel to the central panel plate A.sub.0, and extend toward the internal face of said panel.

[0142] Similarly, the third joining panels R.sub.3 and R.sub.4 are made up of two parts, a first part, R.sub.3A and R.sub.4A, respectively, forming an angle θ with the central panel B.sub.0, and a second part, R.sub.3B and R.sub.4B, respectively, which is parallel to the central panel plate B.sub.0, but which is oriented toward the external face of the plate B. The first joining panels P.sub.1 and P.sub.2 are oriented downward at an angle of around 90° with respect to the plane of the central panel A.sub.0. The third joining panels R.sub.3 and R.sub.4 are oriented at an angle θ of around 90° with respect to the plane of the central panel B.sub.0. The joining panels are preferably formed in a single pass, by deformation. The deformation may be obtained by press-forming and/or by bending, after the corners have been cut.

[0143] FIG. 3b illustrates a schematic perspective view of the manner in which the two plates A and B of FIG. 3a are assembled and mechanically connected at the first and second joining panels P.sub.1 and P.sub.2 of the plate A in order to form a pair of heat exchanger plates. The two plates have been combined and welded via the joining panels P.sub.1 and P.sub.2 on the sides B.sub.1 and B.sub.2 of the plate B in a similar manner to FIG. 2b. The channel formed between the plate A and the plate B constitutes a first channel of the heat exchanger, in which a first fluid F.sub.1 can flow. The first channel has a rectangular flow cross section.

[0144] The third joining panels R.sub.3 and R.sub.4 of the plate B make it possible, in this configuration, to combine the plate B with a fourth heat exchanger, preferably identical to the plate A, which would be positioned next to the external face of the plate B, in order to create, between the plate B and the fourth plate (not shown), a second channel in which a second fluid F.sub.2 can flow, in particular in a crossed manner. The height of the pairs of joining panels is chosen depending on the desired fluid flow rate.

[0145] FIG. 3b shows cross-current exchanger operation of the flows of the fluids F.sub.1 and F.sub.2, and therefore of mutually perpendicular flows, that are obtained with the aid of internal baffles (not shown) which change the direction of the fluid F.sub.2, once the inlet zone has been passed through.

[0146] The exchangers therefore have a plurality of pairs of plates according to the invention that are mounted in a frame, with alternations of plates of each of the two types, for example (ABAB) n times without excluding stacks of the type (ABBA) n times, with a join between two pairs that is made by joining panels incorporated in the plates according to the invention or by additional added components, as shown above.