Patent Grant
12038243
The invention relates to the field of plate heat exchangers used in particular for the exchange of heat between two gases, but also between two liquids or between a liquid and gas.
The heat exchangers of particular interest to the invention are gas-gas exchangers operating with large or small volumetric flow rates at relatively low pressures, for example from 0.1 to 1.5 MPa. These may be used for example in the form of air pre-heaters for furnaces or may form part of NOx reduction installations (DeNOx devices).
The purpose of the heat exchangers is to perform an exchange of heat between a fluid at high temperature and a fluid at low temperature without mixing these. Plate heat exchangers have good thermal performance because of their large heat exchange area, whilst still being compact.
Plate heat exchangers recover the heat by arranging a plurality of plates which are stacked parallel to one another at predetermined intervals. Said plates are spaced apart in such a way that the space between two adjacent plates forms a canal through which a fluid can flow. A high-temperature fluid and a low-temperature fluid are supplied to the successive canals alternately so as to perform a transfer of heat between the high-temperature fluid and the low-temperature fluid via each plate.
Patent EP165179B1 describes a plate heat exchanger characterized in that the canals are defined by the space included between press-formed quadrilateral plates. Said press-formed plates comprise two pairs of opposite edges bent over at 90° in opposite directions: one pair upward and one pair downward if considering the plates in a horizontal plane. The press-formed plates are mounted symmetrically and are combined with one another by welding along their vertical edges. In such a heat exchanger, the inlet and the outlet of each canal are identical. Each press-formed plate requires at least four bending operations in order to manufacture it.
Patent application US2010/0006274A1 describes the plate heat exchanger made up of quadrilateral plates having at least two opposite edges that are bent over with respect to the heat transfer surface. The fluid canals are defined by the space between a pair of identical plates which are positioned as a mirror image of one another. As a result, the two bent-over edges of one plate are in contact with the two bent-over edges of the symmetrical plate. Thus, the plates are bent over on at least two opposite edges.
It is an object of the invention to provide a plate heat exchanger that is improved, notably that has a plate design that guarantees a reduced number of manufacturing operations and/or a reduced manufacturing cycle time, preferably without adversely affecting the heat-transfer performance and corrosion resistance, notably the resistance to corrosion by cracking.
The heat exchanger plate according to the invention, comprising a central panel with at least four sides, said central panel preferably being quadrilateral, or quadrilateral with truncated corners, can be defined as follows:
It will be emphasised that a side that is “flat” within the meaning of the invention is to be understood in its usually accepted manner, namely that the side is entirely flat, from one end of the edge in question to the other, and therefore does not comprise any portion that might not be so and that might, for example, be inclined.
By comparison with the heat exchanger plates already known, the plate according to the invention is produced with a reduced number of operations, insofar as only one bending operation is required in order to manufacture the plate. The heat exchanger plate has a heat transfer performance similar to that of the conventional heat exchanger plates.
By comparison with the heat exchanger plates already known, a single joining panel on two successive heat exchanger plates is potentially enough to mechanically connect them.
By comparison with the heat exchanger plates already known, the corrosion resistance of the heat exchanger plate according to the invention is improved. The plate according to the invention makes it possible to maintain the wall temperature of the plate above the dew point of the fluid, while a hot gas flows at the inlet and the outlet of the canal of the heat exchanger, thereby reducing the risk of corrosion under the effect of condensed acids. In addition, the design of the inlet and of the outlet of the canal offers a geometry that exhibits a lower risk of corrosion by cracking insofar as the number of bent-over edges is reduced.
By comparison with the heat exchanger plates already known, the plate according to the invention can be welded in such a way that there is no need to compensate for the expansion of the corners of the plate and that there is no need to use a dedicated expansion device in the casing of the heat exchanger.
Advantageously, the first joining panel of the heat exchanger plate according to the invention comprises a first part, notably a single part, said first part forming an angle α with said central panel. In this way, the plate is very easy to manufacture.
Advantageously, the first joining panel of the heat exchanger plate according to the invention is made from a first part and from a second part extending from said first part, said first part forming an angle α with the central panel and said second part being parallel to the central panel. The first joining panel can be manufactured with the two parts in a single bending operation. The second part may advantageously be used to weld the first joining panel to another heat exchanger plate. Thus, the plate with a single joining panel can be manufactured in a single bending operation. As a result, the plate is very easy to manufacture and can very easily be assembled with another plate.
In both the latter instances, the angle α between the first part of the first joining panel and the central panel is preferably comprised between 10° and 90°, preferably between 20° and 60°, and more preferably between 30° and 50°.
According to a first embodiment of the invention, a second side of the central panel of the heat exchanger plate according to the invention may be inclined with respect to the central panel, said second side being adjacent to the first side and said second side forming a second joining panel that is inclined in the opposite direction with respect to the first joining panel. Furthermore, the opposite side to said second side may be either flat or inclined in such a way as to form a third joining panel, said third joining panel being a mirror image of said second joining panel.
In this first embodiment, the second joining panel can be used to mechanically connect the central panel of said heat exchanger plate to another heat exchanger plate.
In this first embodiment, either the opposite side to said second side is flat and the two joining panels of the heat exchanger plate according to this embodiment can be mechanically connected to two heat exchanger plates comprising two joining panels, each of the joining panels being connected to one of the two plates. Or, as an alternative, the opposite side to said second side is inclined in such a way as to form a third joining panel which is a mirror image of said second joining panel, which means to say that the opposite side to the second joining panel is inclined in the same direction as the second joining panel. The heat exchanger plate with three joining panels can be mechanically connected to two other heat exchanger plates having just a first joining panel, the first joining panel being connected to one plate and the second and third joining panels being connected to the other plate.
Advantageously, in this first embodiment of the invention, the second joining panel of the heat exchanger plate according to the invention comprises a first part, notably a single part, said first part forming an angle β with the central panel. In this way, the plate is very easy to manufacture.
Advantageously, in this first embodiment of the invention, the second joining panel of the heat exchanger plate according to the invention is made from a first part and from a second part extending from said first part, said first part forming an angle β with the central panel and said second part being parallel to the central panel. The second joining panel may be manufactured with the two parts in a single bending operation so that the plate with two joining panels can be manufactured in two bending operations. The second part of the joining panel may advantageously be used to weld the second joining panel to another heat exchanger plate. As a result, the plate is very easy to manufacture and very easy to assemble with two other plates comprising two joining panels. The third joining panel, where applicable, is a mirror image of the second joining panel and requires a third bending operation. However, the plate with three joining panels can be assembled with two plates having just a first joining panel so that overall, the manufacture of a pair of plates requires only four bending operations.
Advantageously, in the latter two instances of the first embodiment, said angle β between the first part of the second joining panel and the central panel is comprised between 10° and 120°, preferably between 20° and 110°, and more preferably between 30° and 100° or, in particular, is 45° or 90°.
Another subject of the present invention is a pair of heat exchanger plates comprising two spaced-apart heat exchanger plates as described hereinabove, namely a first and a second heat exchanger plate of which the central panels are parallel to one another, wherein
The two plates of the pair of plates according to the invention are assembled via their first joining panels. The space between the two heat exchanger plates forms the first canal to receive a first fluid. The first canal has a trapezoidal cross section that remains identical along its entire length. The velocity of the fluid is substantially constant along the entire length of the canal, and this is something that may be advantageous according to the nature of the fluids.
Because the manufacturing time for each heat exchanger plate is reduced in comparison with that of conventional heat exchanger plates, the manufacturing time for the pair of plates is also reduced.
Another subject of the present invention is a stack of pairs of heat exchanger plates, comprising two spaced-apart successive pairs of plates as described hereinabove, a first pair of heat exchanger plates and a second pair of heat exchanger plates, wherein:
The stack of two spaced-apart successive pairs of plates according to the invention makes it possible to form the second canal to receive a second fluid. The second canal has a cross section that varies along the length of the second canal. The velocity of the fluid varies along the length of the canal, and this is something that may be advantageous according to the nature of the fluids. The manufacturing time for each pair of heat exchanger plates is reduced in comparison with that of conventional pairs of heat exchanger plates, and so the manufacturing time for the stack of pairs of plates is also reduced.
Advantageously, the two successive pairs of the stack of pairs of plates according to the invention are connected at the sides by closure means, said closure means preferably comprising an edge bar, a C-profile or U-profile cover plate, or a flat cover plate of hexagonal or pentagonal shape.
According to a first embodiment of the invention, referred to throughout the present text as the “single joining panel” variant, the heat exchanger plates according to the invention have no second joining panel.
According to another embodiment of the invention, referred to throughout the present text as the “two joining panels” variant, the stack of pairs of heat exchanger plates as described hereinabove, said second pair preferably being identical to said first pair, comprises heat exchanger plates which are such that a second side of the central panel is inclined with respect to the central panel, said second side being adjacent to the first side, and said second side forming a second joining panel inclined in the opposite direction with respect to the first joining panel, and the opposite side to said second side is flat. The stack according to the invention is then such that:
The stack of two spaced-apart successive pairs of plates according to this embodiment of the invention allows the first and the second joining panel to be used to mechanically connect the heat exchanger plates. The manufacturing time for each pair of heat exchanger plates is reduced in comparison with that of conventional pairs of heat exchanger plates, and the manufacturing time for the stack of pairs of plates is also reduced.
When the corner zone at the level of the intersection of the first and second joining panel is formed in such a way as to mechanically connect the two pairs of plates, there may be no need to use cover plates.
In the “two adjoining panels” embodiment, the stack of pairs of heat exchanger plates may advantageously comprise heat exchanger plates wherein said second joining panel of each plate of the stack comprises a first part, notably a single part, said first part forming an angle β with the central panel, or wherein said second joining panel of each plate of the stack is made up of a first part and of a second part extending from said first part, said first part making an angle β with the central panel and said second part being parallel to the central panel.
Another subject of the invention is a plate heat exchanger comprising the heat exchanger plates and/or pairs of heat exchanger plates and/or a stack of pairs of heat exchanger plates as described hereinabove, arranged inside a suitable casing.
The present invention also relates to a method for manufacturing a pair of heat exchanger plates as described hereinabove, said method comprising the following steps:
Assembling the pair of heat exchanger plates is easy and involves a reduced number of bending operations, thereby reducing the manufacturing costs and time.
The present invention also relates to a method for manufacturing a stack of pairs of heat exchanger plates as described hereinabove, said method comprising:
In the “single joining panel” variant of the invention, the plates of the heat exchanger may be substantially identical, and preferably are identical, making assembly easier and reducing manufacturing costs: to form a stack of pairs, all that is required, for example, is to prepare a first pile of plates and a second pile of plates in which the plates, which are notably all identical, have been rotated through 180° and turned over. Thereafter, plates are taken from the two piles alternately in order to gradually make up the stack. The process may be automated.
In the “two adjoining panels” embodiment of the invention, the plates of the heat exchanger may be substantially similar: the second joining panel being situated alternately to one side and to the other of the first joining panel, for two plates which succeed one another in the stack of plates. Specifically, the second joining panels may thus face one another when two successive pairs have been assembled. That makes assembly easy and reduces manufacturing costs: to form a stack of pairs, all that is required, for example, is to prepare a first pile of plates of the first type and a second pile of in order to make up the stack. The process may be automated.
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.
Throughout the present text, the term “side” of the central panel is used with reference to the periphery of the central panel, over a certain width, for example up to 5% of the width of the plate.
Throughout the present text, the term “mirror image” refers to symmetry about a plane situated in the middle of the space separating the object from its likeness.
The invention can be used for example for plate heat exchangers operating on the cross-flow principle, in which the fluids flowing over the two faces of each plate are directed substantially perpendicular 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. 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.
The invention is particularly well suited to exchanges between two fluids, notably two gases, but may also be used for exchanges of heat between two liquids or between a liquid and gas.
The invention is more particularly suitable for exchanges between two gases, notably gas flows at the inlet and outlet of a single item of equipment, such as, for example, the air that is to be carried to a furnace and the flue gases from that same furnace or, similarly, the hot stream coming from a NOx reduction system and the cold stream heading toward the same NOx reduction system.
A plate heat exchanger according to the invention can be used for fluids operating at a pressure ranging from total vacuum pressure up to 1.5 MPa, preferably from 0.1 to 1.0 MPa, and more preferably, from 0.1 to 0.6 MPa.
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.
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, notably being 5 mm, 10 mm, 15 mm, 20 mm, 30 mm, or any appropriate height.
The width of the heat exchanger plate according to the invention may typically be comprised 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 comprised between 1000 mm and 7500 mm, preferably between 1500 mm and 7000 mm. The thickness of the plate may be comprised between 0.6 mm and 6 mm, preferably between 1.5 mm and 2.0 mm.
The central panel of the heat exchanger plate according to the invention may have any suitable shape, for example trapezoidal, hexagonal or quadrilateral. The central panel is more preferably quadrilateral, notably rectangular or square, possibly with truncated corners.
The central panel comprises a first face (or lower face) and a second face (or upper face) opposite to the first face. The first and second faces may be planar but may also locally comprise reliefs, ribs or protrusions.
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 a number of arrangements according to the characteristics of the plate and the purpose of said dimples. The dimples may be used by way of spacer elements and are intended to minimize the deformations of the plates when 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.
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.
According to one preferred embodiment of the invention, the heat exchanger according to the invention is such that:
In the remainder of the present text, the first canal with the “direct” or “bluff” inlet and outlet is referred to as the “bluff canal” and the second canal with the “sharp” inlet and outlet is referred to as the “sharp canal”.
According to a first mode of operation of the invention, the hot fluid that is to be processed in the heat plate heat exchanger on the hot side may be sent into the “bluff canals” and the cold fluid that is to be processed on the cold side may be sent into the “sharp canals”.
According to a second mode of operation of the invention, the cold fluid that is to be processed in the heat plate heat exchanger on the cold side may be sent into the “bluff canals” and the hot fluid that is to be processed on the hot side may be sent into the “sharp canals”.
When the hot fluid is flowing in the “bluff canal”, the profile of the heat exchanger plate encourages vapor of the hot fluid to condense. By contrast, when the hot fluid is flowing in the “sharp canal”, the profile of the heat exchanger plate encourages the hot fluid not to condense.
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, notably by seam welding or by bolting.
In a stack of pairs of plates according to the “single joining panel” variant, in which the heat exchanger plates have no second joining panel, the second canal is advantageously provided with means for closing its lateral side between two successive pairs of plates. Said closure means may be edge bars or cover plates (cover parts) or any equivalent means. The cover plates may be manufactured in a single or in several 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 assembled with the first plate of the second pair. The shape of the cover plate may also be octagonal so that it conforms in a single piece to the cross section of the second canal. Closure means may be provided longitudinally in the direction of flow of the second fluid at the level of the inlet and of the outlet of the second canal.
In a stack of pairs of plates according to the “two joining panels” variant, in which heat exchanger plates have two joining panels, the successive pairs are assembled via the second joining panel of the second plate of the first pair on one side and via the second joining panel of the first plate of the second pair on the other side.
In that case, either closure means may advantageously be provided, running longitudinally in the direction of flow of the second fluid at the level of the inlet and at the level of the outlet of the second canal. Said closure means may preferably be a polygonal cover plate of quadrilateral or pentagonal shape.
Or, the corner zone at the level of the intersection between the first and second joining panels may advantageously be press-formed or formed in some other way so that said corner zone is used for mechanically connecting the second plate of the first pair and the first plate of the second pair so that there is no need to use closure means. Typically, said corner zone may be stamped, embossed, pressed, hammered and enlarged enough that it can be welded to the panels of adjacent plates.
The first and second canals, notably the second canal, may be either completely empty (free canal) or may comprise any type of reinforcing element such as connecting bars.
Advantageously, spacer elements (spacers) manufactured for example from strips, profiles, dimples or pin fins may be inserted into the canal to ensure the spacing between the plates. They may be loose or may be spot welded in place or may be held in place by profiled U-shaped clamps at the supply and discharge points.
Advantageously, the first and second joining panels, which comprise a part, notably a single part, or which are manufactured from two parts, are made of plates that are flat or substantially flat.
According to one preferred embodiment of the invention, the first joining panel or the second joining panel may be mechanically fixed to the central panel of the adjacent plate by any possible technique, typically by welding.
Advantageously, the second part of the first and/or of the second joining panel may be large enough to allow mechanical fixing of the second part to the central panel of the adjacent plate by any means known to those skilled in the art.
In a first variant, the second joining panel may be oriented downward with respect to the plane of the central panel at an angle β comprised between 10° and 90°, preferably between 20° and 60°, and more preferably between 30° and 50°.
In a second variant, the second joining panel may be oriented downward with respect to the plane of the central panel at an angle β comprised between 60° and 120°, preferably between 70° and 110°, and more preferably between 80° and 100°.
As a variant, the second part of the second joining panel may extend from the first part of the second joining panel parallel to the plane of the central panel, said second part being either oriented toward the inside of the canal or toward the outside of the canal.
Each of the first, second or third joining panel may preferably be formed in a single step, by deformation. The deformation may be obtained by press-forming and/or by bending.
In another embodiment of the invention, different zones of the heat exchanger central panel may be provided with a layer of insulation made of 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. Said layer of insulation may typically be employed in the coldest zones of the cold canal and is described for example in patent CZ298773B6.
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.
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 steel plate or stainless steel plate. The first and, where applicable, the second and third joining panel may form part of the central panel or may also be fixed thereto. In the “two joining panels” variant, a second step in the deforming of the flat metal sheet may be required in order to form the second lateral joining panel. The deformations may be obtained by press-forming and/or by bending. The heat exchanger plate according to the invention may also be manufactured by assembling several independent plate parts.
Further features and advantages will become apparent from reading the following description provided purely by way of nonlimiting illustration, which is to be read with reference to the attached figures, in which:
The sake of clarity, the figures do not necessarily depict the plates in the spatial position in which they can be assembled or used.
The reference symbols used in the figures are given hereinbelow with reference to the components to which they refer:
A first side A1 of the central panel is inclined with respect to the central panel and forms a first joining panel JA. The side A3 of the central panel situated opposite to the first joining panel JA is a flat edge. In the embodiment illustrated in
The heat exchanger plate B is identical to A and is positioned symmetrically with respect to A with respect to the point situated at the center of the space between plate A and plate B. That means that plate B has been set down after having been turned over and turned through 180°, the first joining panels of plates A and B facing one another.
The two plates of
The canal formed between plate A and plate B constitutes the first canal of the heat exchanger made up of the plates according to the invention, in which a first fluid F1 can flow. The first canal has a flow cross section that is trapezoidal, and said cross section is the same along the entire length of the canal.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1859077 | Oct 2018 | FR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2019/075267 | 9/20/2019 | WO |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2020/069880 | 4/9/2020 | WO | A |
| Number | Name | Date | Kind |
|---|---|---|---|
| 20060131002 | Mochizuki | Jun 2006 | A1 |
| 20110017436 | Cho | Jan 2011 | A1 |
| 20130319069 | Abker et al. | Dec 2013 | A1 |
| Number | Date | Country |
|---|---|---|
| 2669027 | Dec 2013 | EP |
| 2669027 | Dec 2013 | EP |
| 361780 | Nov 1931 | GB |
| 2014178472 | Nov 2014 | WO |
| Entry |
|---|
| International Search Report dated Nov. 21, 2019 issued in corresponding PCT/EP2019/075267 application (2 pages). |
| Number | Date | Country | |
|---|---|---|---|
| 20210389060 A1 | Dec 2021 | US |
