EP0553340B1 - Plate-type heat exchanger - Google Patents

Abstract

The invention concerns the production of a plate-type heat exchanger in which a bundle (1) of heat exchange plates, between which two fluids circulate, consists of a stack of pairs (2) of plates (3, 3') provided with corrugations and welded together at their lateral edges (5, 5'). Closed conduits (6) are formed for a first heat exchange fluid, said conduits extending longitudinally from one end of the bundle (1) to the other, while gaps between two pairs (2) of adjacent plates (3, 3') contacting each other by means of the outer ridges (7) of the corrugations form open conduits (8) for a second heat exchange fluid.

Description

The present invention relates to the design of plate type heat exchangers. They are generally distinguished from tubular exchangers by the fact that the fluids in a heat exchange situation circulate longitudinally on either side of corrugated plates arranged parallel to one another so as to rest on each other. others by ridges of their respective undulations.

The present invention relates more particularly to a heat exchanger of the plate type, comprising a heat exchange bundle constituted by corrugated plates resting on each other by ridges of their respective corrugations, so that said plates provide between them first and second passage channels for respectively a first and a second heat exchange fluid.

As described, for example, in FR-A-2,471,569 or 2,638,226, exchangers of this type include a bundle of parallel flat plates which are made of thin sheets, most often made of stainless steel, provided with corrugations by which they are in contact with one another and by which they organize the circulation of fluids longitudinally from one end to the other of the exchanger (generally against the current one of the other), creating turbulence favorable to the heat exchanges which take place between the fluids through each plate. On their longitudinal edges, the plates are all welded together by means of tongues or frames forming spacers which hold the spacing between two successive joint plates. The stack of plates thus stiffened is framed by two relatively thick sheets, which transfer the weight of the beam onto a support.

According to the known technique, the tongues are placed continuously on the flat lateral edges of the plates on either side of each individual plate, so as to ensure its connection by welding with the two adjacent plates which surround it. Their thickness balances that of the corrugations by which the thin sheets constituting the plates bear on one another, while providing circulation channels for an exchange fluid between two successive plates, which are all closed all along the edges side plates.

Such an embodiment of the beam is particularly difficult to implement. In addition, since the welding operation involves substantially different thicknesses of material to be welded, between the tongues and the thin sheets, this leads to stresses and cracks due to differences in thermal inertia.

The present invention aims in particular to design an easier production beam which is lighter and which overcomes the above drawbacks. It is situated in a usual technological context, where this beam is placed in an enclosure suitable for receiving and containing that of the fluids with the highest pressure.

According to its main characteristic, the objective of the present invention is a plate-type heat exchanger, comprising a heat exchange bundle constituted by corrugated plates resting on each other by ridges of their respective corrugations and forming between them first and second passage channels for respectively a first and a second heat exchange fluid, characterized in that said bundle is formed of a stack of pairs each formed of two plates mutually in contact by their respective lateral edges and welded to each other by these edges from one end to the other end of said bundle, so that said channels are alternately closed and open along said lateral edges in a enclosure containing said bundle, in that said plates are also joined at the ends of the bundle by the intermediate tabs providing inlets and outlets for said fluids, and in that said exchanger comprises at least one connection box which is welded to said tabs at one end of the bundle to guide the circulation of one of the heat exchange fluids between said closed channels and an internal conduit guiding it through said enclosure.

The invention makes it possible to eliminate the intermediate tabs between plates on the lateral edges, at least once in two, whereby this leads not only to a noticeable reduction in the weight of the whole beam, but above all, the consequences of welding operations involving thicknesses of material to be welded substantially different, between the tongues and the thin sheets, where tensions and cracks due to the differences of thermal inertia.

In accordance with the invention, it is sought to hermetically close only one channel out of two. In practice, a first welding step consists in welding two by two the lateral edges of the plates, pressed against each other, preferably without filler metal. Each pair of two plates thus forms a fluid passage channel, longitudinally from one end to the other of the bundle.

The present invention also relates to the production of a plate-type heat exchanger comprising a pressure resistance enclosure in which the bundle of heat exchange plates is placed. The exchanger according to the invention then advantageously comprises means for supplying and evacuating the heat exchange fluids between the outside of the enclosure and the ends of the bundle, at the level of intermediate tabs which join the plates while sparing inputs and outputs for said fluids.

As will be seen later, these supply and evacuation means are preferably arranged so that the second fluid flowing in the open passage channels fills the enclosure. This second fluid will preferably be the fluid at higher pressure, so that it is not necessary to provide elements for taking up pressure forces on the bundle, the holding of the stack being ensured by the fluid at higher pressure filling the enclosure, preferably upstream of the pressure drop it undergoes when crossing the beam.

Such an embodiment, which does not require the welding operation of the entire beam on its lateral edges, also allows in a variant to embodiment, to ensure better filling in volume of the enclosure, generally cylindrical, by authorizing the production of a bundle of plates from pairs of plates of different widths. A better exchange capacity of the exchanger is therefore obtained for a given size.

In order, on the one hand, to facilitate the assembly of the exchanger and, on the other hand, to guide the second fluid longitudinally in the bundle, the latter is advantageously surrounded by a substantially parallelepipedal box open at its two longitudinal ends.

According to the invention, this box is of particularly simple constitution, insofar as it does not need to ensure a resumption of the pressure forces. Advantageously, the second higher pressure fluid circulating in the open channels and in the volume of the enclosure makes it possible to avoid elements for taking up these forces.

According to an alternative embodiment of the invention, the box is replaced by two plates constituting side panels of length identical to the length of the plates and of width somewhat greater than the height of the stack. These plays ensure the guiding of the second fluid in the open channels of the bundle, the maintenance of the stack, before its assembly with the supply and discharge means, its positioning in the enclosure can be ensured by means of fixing the played between them connecting them to each other at points on their lateral edges, for example by tie rods or any other means.

According to another alternative embodiment where the maintenance of the stack prior to its assembly with the supply and evacuation means is not necessary, which may be the case for example of a beam of variable width intended to occupy a larger volume in section in a cylindrical enclosure, the beam will be placed directly in the enclosure and the stack will be maintained once the pressurization has been carried out by the second higher fluid pressure.

In order to allow the organization of the circulation of fluids in the bundle from its ends, the latter advantageously comprises at its longitudinal ends, intermediate tabs which, to determine the access passages of the fluids at the inlet and at the beam exit, are placed so that the laterally closed passage channels are open at the ends in the central part and the open channels for the second fluid between two adjoining pairs of two laterally welded plates are on the contrary closed by tabs in the same central area. Conversely, in the two lateral zones on either side of the central zone, there are tabs closing the closed passage channels while the passage channels for the first fluid remain open. It will often be useful here for the tongues intended to close each closed passage channel in the lateral zones to be cut at a bevel at their end opposite the lateral edges of the plates, in order to allow their welding to be easily connected to the watertight welding of the corresponding channel. .

Looking at the beam at the end, we therefore see in succession, transversely to the stack, alternately a central tab and two lateral tabs, with however advantageously an overlap from one channel to the other on the edges of the central zone, there where, as will be seen later, an internal collector constituting the means for supplying or discharging the first fluid will be welded to the tongues by a connection box.

Note that welding at this level in no way poses the problems encountered in the prior art with the side tabs. In fact, the relatively thick tongues advantageously have a much shorter length along the thin sheets to be welded, and moreover, the welding involves the walls of the collector, which are also relatively thick compared to the thin sheets constituting the plates.

The means for supplying and evacuating the first fluid-between the outside of the enclosure and the ends of the bundle advantageously comprise according to the invention, at each longitudinal end of the bundle, an internal collector circuit consisting of a box of internal connection, welded by its longitudinal edges to the overlapping area of the lateral and central tabs and by its transverse edges to the external plates of the stack, and an internal conduit ensuring the connection between the connection box and the outside of the enclosure by crossing it.

The means for discharging the second exchange fluid advantageously comprise an external collector circuit, consisting of an external connection box, welded by its edges to the end of the box, and an external conduit coaxial with the internal conduit of the collector internal constituting the means for supplying the first fluid, ensuring the connection between the external box and the outside of the enclosure.

The connection boxes are preferably made in the form of half-cylinders, the inlet box for the first fluid being inside the outlet box for the second fluid.

The means for supplying the second fluid may be produced in a similar manner to its means of evacuation, but they advantageously consist of a simple orifice in the enclosure, the second higher pressure fluid thus freely entering the bundle at the same time as it fills the enclosure, designed to withstand high pressure.

• lors d'une première étape de soudage, à souder deux par deux les bords latéraux des plaques, pressés l'un contre l'autre, de préférence sans métal d'apport ;
• à empiler les couples de plaques ainsi réalisés les uns sur les autres, en contact par leurs ondulations respectives extérieures, l'ensemble étant de préférence maintenu dans un caisson parallélépipédique ouvert aux deux extrémités ;
• à mettre en place, à ces deux extrémités, les languettes intercalaires qui déterminent les passages de fluide aux deux extrémités du faisceau ;
• lors d'une deuxième étape de soudage, à souder les languettes d'extrémités et les bords transversaux des plaques, et simultanément les boîtes de raccordement internes sur la zone de recouvrement des languettes ;
• lors d'une troisième étape de soudage, à souder la ou les boîtes de raccordement externes sur les extrémités du caisson entourant le faisceau.

The invention also relates to a method for producing a plate type exchanger consisting of:

• during a first welding step, welding the side edges of the plates two by two, pressed against each other, preferably without filler metal;
• stacking the pairs of plates thus produced on top of each other, in contact with their respective external corrugations, the assembly preferably being held in a parallelepipedal box open at both ends;
• in placing, at these two ends, the intermediate tabs which determine the fluid passages at the two ends of the bundle;
• during a second welding step, welding the end tabs and the transverse edges of the plates, and simultaneously the internal connection boxes on the overlap zone of the tabs;
• during a third welding step, to weld the external connection box or boxes on the ends of the box surrounding the bundle.

• la figure 1 représente en coupe transversale, dans une région où les plaques présentent des ondulations, un faisceau de plaques d'échange thermique selon l'invention ;
• la figure 2 représente en coupe transversale un faisceau de plaques selon l'invention, la coupe étant réalisée dans la région d'une des extrémités longitudinales du faisceau ;
• la figure 3 représente une vue partielle en perspective éclatée d'un échangeur selon l'invention ;
• la figure 4 représente schématiquement une coupe transversale d'une variante de réalisation d'un échangeur selon l'invention ; et
• la figure 5 représente schématiquement et partiellement une vue en perspective d'un échangeur selon l'invention.

We will now describe in more detail particular embodiments of the invention which will better understand its essential characteristics and advantages, it being understood however that these embodiments are chosen by way of nonlimiting examples. Their description is illustrated by the appended drawings in which:

• Figure 1 shows in cross section, in a region where the plates have undulations, a bundle of heat exchange plates according to the invention;
• 2 shows in cross section a bundle of plates according to the invention, the section being made in the region of one of the longitudinal ends of the bundle;
• Figure 3 shows a partial exploded perspective view of an exchanger according to the invention;
• Figure 4 schematically shows a cross section of an alternative embodiment of an exchanger according to the invention; and
• Figure 5 shows schematically and partially a perspective view of an exchanger according to the invention.

In all these figures, and for reasons of clarity, the scales have not been respected and the representations are shown schematically. In addition, and always for reasons of clarity, the same elements will be designated by the same references in the different figures.

A bundle 1 of heat exchange plates according to the invention as shown in Figures 1 and 2 consists of a stack of pairs 2 of plates 3, 3 '. Each pair 2 of plates 3, 3 'is produced by superimposing two thin sheets constituting the plates 3, 3' bearing on each other by internal ridges 4 of corrugations which they comprise and which constitute their own means to organize the circulation of heat exchange fluids passing between two neighboring plates belonging to the same couple. The plates 3, 3 ′ furthermore comprise a frame with a smooth surface, devoid of undulations and allowing in particular that two plates 3, 3 'constituting a couple 2 are welded to each other by the respective lateral edges 5, 5' of the plates 3, 3 'pressed against each other, without metal of input.

The pairs 2 of plates 3, 3 ′ thus produced constitute closed passage channels 6, longitudinally from one end to the other of the bundle 1, for a first heat exchange fluid.

The pairs 2 of plates 3, 3 ′ are then stacked on each other and the intervals between two pairs of neighboring plates, in contact with external ridges 7 of the undulations of their plates, provide open passage channels 8 for a second heat exchange fluid.

The stack is then, in the example described, maintained in a simple rectangular box 9 open at both ends. The purpose of this box 9 is firstly to channel the second heat exchange fluid into the open channels 8, and secondly, secondarily, to keep the stack in place until it is pressurized in an enclosure 10 (Figure 5), designed to withstand the pressure of fluids.

In the exchanger, the fluid circulating in the closed channels 6 will preferably be the fluid at lower pressure, or at least that which does not fill the enclosure, generally with a cylindrical shell, containing the bundle of plates. Indeed, the higher pressure fluid thus circulating in the open channels 8 at the same time as it fills the enclosure 10 as will be seen later, this makes it possible to prevent the box 9 having to take up the efforts of pressure.

At the two ends of the stack constituting the bundle 1, tongues are put in place spacers 11, 12 (FIG. 2) which determine the passages of the fluid at the entry and exit of the bundle, where the passage channels 6, 8 connect to connection boxes 13, 14 (FIG. 3), so then carry out the welding of the end tongues 11, 12 and of the transverse edges 15, 15 'with smooth surface of the plates 3, 3' at the same time as that of internal connection boxes 13, 16 (FIG. 5) for the first fluid.

The exchanger as shown in Figure 5 is an exchanger where the entire bundle 1 is suspended from the enclosure 10 with a cylindrical shell by an external manifold 17 of the first low-pressure heat exchange fluid, passing to the festive end of the exchanger inside an internal collector 18 of the second high-pressure heat exchange fluid, while at the foot end, the second high-pressure fluid freely enters the bundle 1 at the same time that it fills the enclosure 10, designed to resist high pressure, and that the first low pressure fluid leaves the bundle 1 via an internal manifold 19.

These collectors 17, 18, 19 constitute means for supplying and evacuating the heat exchange fluids from the outside of the enclosure 10 towards the ends of the bundle.

The internal collector circuits 18 and 19 each consist of an internal connection box 13, 16 of generally semi-cylindrical shape, and an internal conduit 20, 21 ensuring the connection between the connection box 18 or 19 and the outside the enclosure 10.

The external collector circuit 17 consists of an external connection box 14 of generally semi-cylindrical shape and of an external conduit 22 ensuring the connection between the connection box 17 and outside the enclosure 10, the internal 20 and external 22 conduits being coaxial.

The channels 6 which were closed laterally during the plate 3 on plate 3 ′ welding step are open at the ends in a central zone 23 and are closed in the two lateral zones 24 and 25 on either side of the zone central 23 by the tongues 11, both at the head and at the bottom of the beam. The open channels 8 formed for the second fluid between two couples 2 joined to two plates 3, 3 'welded laterally are on the contrary closed by tongues 12 in the central zone 23 so as not to communicate with the internal collectors 18, 19. In the two lateral zones 24, 25 there are tabs 11 closing the channels 6 of the first fluid while the channels 8 of the second fluid remain open to communicate either with the external manifold 17 at the head end, or with guide means analogues, or directly with the internal volume of the enclosure 10 at the foot of the beam.

Once the tongues 11, 12 are in place, the welding of these tongues is therefore carried out on the transverse edges of the plates at the same time as the welding of the internal connection boxes 13, 16 on an overlap zone 30 of the tongues 11, 12 at the two edges of the central zone 23 and on the central zone of the transverse edges of the two external plates of the bundle 1.

Finally, a final welding step consists in welding the external connection box 17 on the end of the box 9 surrounding the bundle.

The variant embodiment shown in FIG. 4 shows the best filling by volume which can be obtained according to the invention in a cylindrical shell 26 constituting the enclosure of the exchanger. In this case, a beam 27 of plates 28 of different widths. A stepped section of the bundle as shown is made possible by the realization of the bundle in the form of pairs of stacked plates between which the passage channels for the second fluid can remain open.

Claims (13)

1. A plate-type heat exchanger comprising a heat-exchange bundle constituted by corrugated plates which rest on each other by means of crests of their respective corrugations thereby forming between them first and second flow passageways (6, 8) respectively for a first and a second heat-exchange fluids, characterized in that said bundle (1) is made up of a stack of pairs (2) each comprising two plates (3, 3') that are mutually in contact on their respective lateral edges (5, 5') and that are welded together along these edges from one end to the other end of said bundle (1), so that said passageways (6, 8) are alternately closed and open along said lateral edges within an outer enclosure (10) which contains said bundle (1), in that said plates are also joined to the ends of the bundle by means of intercalary strips (11, 12) forming inlets and oulets for said fluids, and in that said heat exchanger comprises at least one connecting box which is welded to said strips at an end of the bundle in order to guide the circulation of one of the heat-exchange fluids between said closed passageways (6) and an inner duct (20) which guides said fluid through said outer enclosure (10).
2. A plate-type heat exchanger in accordance with claim 1, characterized in that each closed flow passageway (6) is provided at its two longitudinal ends with two intercalary strips (11) which close-off each end on each side of a central zone (23) constituting the access to the closed flow passageway (6) and that each open flow passageway (8) is provided at its two longitudinal ends with an intercalary strip (12) which closes-off each end in said central zone (23).
3. A plate-type heat exchanger in accordance with claim 2, characterized in that the length of said intercalary strips (11, 12) is such that, when they have been placed in position, they have a zone of overlap from one passageway to another on the edges of said central zone (23).
4. A plate-type heat exchanger in accordance with any one of claims 1 to 3, characterized in that the lateral edges (5, 5') of two adjacent plates constituting a pair (2) of plates (3, 3') are welded through being pressed against each other, preferably without filler metal.
5. A plate-type heat exchanger in accordance with any one of claims 1 to 4, characterized in that it comprises a casing (9) which is open at both ends and surrounds the bundle (1) so as to laterally guide the second heat-exchange fluid within said open passageways (8).
6. A plate-type heat exchanger in accordance with any one of claims 1 to 5, characterized in that the stack (27) is made up of pairs of plates (28) having different widths which permit better filling of the volume of the outer enclosure (10), said enclosure being a cylindrical shell (26).
7. A plate-type heat exchanger in accordance with claim 4 or claim 6, characterized in that it comprises on each side of the bundle (1), opposite to the lateral edges of the plates, two sideplates having a length substantially equal to the length of the plates and a height substantially equal to the height of the stack so as to guide the second heat-exchange fluid longtudinally from one end of the bundle to the other.
8. A plate-type heat exchanger in accordance with any one of claims 3 to 7, characterized in that said connecting-box (13) for said first heat-exchange fluid which is intended to circulate within said closed passageways (6) has a generally semi-cylindrical shape and is welded to said strips (11, 12) in overlap zones in accordance with claim 3 as well as to the transverse edges of the external border plates of the stack (1).
9. A plate-type heat exchanger in accordance with any one of claims 1 to 8, characterized in that said connecting-box (13) forms with said duct (20) an inner header circuit (18) for admitting said first fluid into said closed passageways (6) of the heat-exchange bundle (1) and that a similar header circuit (19) is provided at the lower end of said bundle for the discharge of said first fluid out of said enclosure (10).
10. A plate-type heat exchanger in accordance with any one of claims 5 to 9, characterized in that, for the discharge of a second heat-transfer fluid which is intended to circulate within said open passageways (8), said heat exchanger is provided with an outer header circuit (17) comprising an outer connecting-box (14) preferably having a generally semi-cylindrical shape and welded to an open end of said casing (9), and an outer duct (22) providing a connection between said outer connecting-box (14) and the exterior of the enclosure (10).
11. A plate-type heat exchanger in accordance with claim 10, characterized in that said inner header (18) for the admission of the first fluid is contained within said outer header (17) for the discharge of the second fluid, said outer header being located at the upper end of the bundle (1).
12. A plate-type heat exchanger in accordance with any one of claims 9 to 11, characterized in that means for admitting the second fluid open through a simple orifice into the enclosure (10) and the second fluid thus passes freely into the bundle (1) while at the same time filling the enclosure (10).
13. A method of construction of a heat exchanger in accordance with claim 1 or claim 12 and having a bundle of plates in accordance with claim 4, characterized in that it consists :

    - in a first step, in welding in pairs the lateral edges (5, 5') of the plates (3, 3') pressed against each other, preferably without addition of filler metal ;

    - in stacking the pairs (2) of plates (3, 3') thus formed in superposed relation and in placing the stack within a parallelepipedal casing (9) which is pen at both ends ;

    - in positioning at the ends of the passageways (6, 8) formed by the stack intercalary strips (11, 12) designed to establish passages for the fluids at both ends of the bundle ;

    - in a second welding step, in welding the strips (11, 12) and the transverse edges (15, 15')of the plates and of the inner connecting-boxes (13, 16) to the zone of overlap of the strips (11, 12) ;

    - in a third welding step, in welding at least one outer connecting-box (14) to one end of the casing (9) which surrounds the bundle (1).

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