EP1797386B1 - Heat exchanger with specific plates - Google Patents

Abstract

The invention concerns a plate heat exchanger, comprising a plurality of plates (2-5) assembled to define between them fluid circulating channels (6-8). Each plate comprises undulations (25) or corrugations defined between apex lines of corrugations (35) and base lines of corrugations (32). At least one part of the plates comprises recessed (30, 31)and bump (33) deformations located between the apex and base lines of corrugations. Said exchanger is characterized by the positioning of said bumps and recesses relative to contact points (51, 54) between adjacent plates (48, 25) delimiting the channel.

Description

Technical area

The invention relates to the field of heat exchangers, specifically plate heat exchangers. Such exchangers are constituted by the stack of corrugated plates, and assembled to define between them fluid circulation channels, in two interleaved circuits.

The invention is more specifically an improvement concerning the positioning of reliefs formed on these plates.

Previous techniques

In general, the plate exchangers comprise corrugations, defining corrugations, so that the channel defined with the adjacent plate has a variable section. Generally, these corrugations are inclined with respect to the fluid flow direction, and have the opposite inclination with respect to corrugations of the adjacent plate. These corrugations are frequently, but not necessarily, in the form of chevrons. These different geometrical variants have the objective of defining channels whose function is to disturb the flow, with a view to improving heat exchange.

The Claimants described in the document EP 0 737 296 an improvement to this type of exchanger, intended to improve on the one hand, the heat losses, and secondly, the risk of fouling of the exchanger in areas of lesser passage. This improvement consists in carrying out on the corrugations deformations which further disturb the circulation of the fluid. These deformations are obtained during the manufacture of the plate which is generally made by stamping. These deformations may be recessed or hump with respect to the main corrugation, it being understood that the deformations forming a recess on one face of the plate constitute a bump deformation on the opposite face of the same plate.

According to the teachings of this document, the deformations in the bump are preferably localized near the contact points between plates, which correspond to the zones where the velocity of the fluid is the lowest. These areas are therefore dead or stagnant zones in which the deposits are likely to appear. The positioning of the deformations in the bump near these contact points thus makes it possible to reduce the volume of these dead zones, and thus limit the risks of deposit formation, without, however, increasing too much the pressure drops.

After experimentation, it turns out that this positioning of the deformations in the bump near the contact points between plates is not really satisfactory, in particular because of an increase in pressure drops. In addition, the bump deformation present inside a channel, corresponds to a deformation on the adjacent channel, which limits the positive effect of the bumps in this adjacent channel.

The objective of the present invention is to optimize the performance of this type of exchanger on all the factors representative of the efficiency of the exchanger, that is to say the heat exchange coefficient, and that the pressure losses generated, and this being compatible with a rate of fouling as low as possible.

Presentation of the invention

The invention therefore relates to a heat exchanger which comprises a plurality of corrugated plates assembled to define between them fluid circulation channels.

In a known manner, each plate comprises corrugations defined between corrugation vertex lines and corrugation background lines. All or some of these plates include, as in the document EP 0 737 296 deformations hollow and hump, located between the top and bottom lines of corrugation.

The invention lies in a more precise positioning of the various deformations hollow and hump with respect to the lines of contact points between the adjacent plates. This location is defined on the side of the "place" of a plate, that is to say the face coming in front of a channel considered, and inside an elementary cell defined between four points of consecutive contact with the adjacent plate delimiting the channel.

• ■ D₁ est la distance mesurée dans un plan parallèle à surface principale de la plaque, et parallèlement à la ligne de sommet de corrugation, séparant :
  • le centre de la déformation en bosse la plus proche d'un des points de contact ;
  • un point de référence situé à égale distance de la ligne de sommet de corrugation et de la ligne de fond de corrugation, ledit point de référence étant aligné avec ledit point de contact selon la direction d'écoulement du fluide.
• ■ D est la distance mesurée dans un plan parallèle à la surface principale de la plaque et parallèlement à la ligne de sommet de corrugation séparant :
  • le centre de la déformation en bosse la plus proche d'un des points de contact ;
  • le centre de la déformation en creux la plus proche selon la direction de la ligne de sommet de corrugation.

Thus, the deformations in the bump and recess are localized so that the criterion N = D ₁ / D is between 0.35 and 0.8 in which:

• D ₁ is the distance measured in a parallel plane with a main surface of the plate, and parallel to the corrugation vertex line, separating:
  • the center of the bump deformation closest to one of the contact points;
  • a reference point equidistant from the corrugation vertex line and the corrugation bottom line, said reference point being aligned with said contact point in the direction of flow of the fluid.
• ■ D is the distance measured in a plane parallel to the main surface of the plate and parallel to the corrugation vertex line separating:
  • the center of the bump deformation closest to one of the contact points;
  • the center of the nearest hollow deformation in the direction of the corrugation vertex line.

In other words, the invention lies in the location of the bump deformations at an intermediate level between the contact points, and not near the contact points, corresponding to a substantially zero criterion N, as taught by the patent. EP 0737296 .

The location of these hump deformations according to the invention surprisingly results firstly by an improvement in the thermal exchange performance, and also by a reduction in the pressure losses measured in the exchangers incorporating such plates.

Thus, in practice, the efficiency of a plate heat exchanger has been evaluated by combining the power transmitted with the measured pressure drops. Measurements made in comparison with corrugated plates without hollow deformation and hump show an improvement in the overall efficiency of the exchanger, within the range of criteria considered. This improvement even reaches about ten percent for the optimum of the criterion evaluated at around 0.55, in chevron configurations described earlier in the description of a particular embodiment.

Similarly, the improvement in terms of pressure losses results in a decrease of several tens of percent in the vicinity of this optimum.

In practice, the deformations can take various different forms, which depend on the stamping process, and the elongation that can be subjected to the material used. Whatever the form of these deformations, the measurements necessary for the evaluation of the characteristic criterion are made by defining the volume of these deformations with respect to the general form of the undulation. This general shape can in particular be evaluated in a zone free of deformation in hollow and hump. This volume is then projected on the main plane of the plate, and the center of gravity of this projection is then considered as the center of the deformation.

In practice, multiple positional arrangements of deformations in hollow and hump can be adopted, but it will be preferred to maintain a repetitiveness of the repositioning patterns to avoid the formation of preferential paths, and the appearance of areas too strongly stagnant.

Among the various satisfactory geometries, those in which the hump deformations are alternately distributed are identified. offset on either side of the top line of a corrugation, by looking at the face of the plate, that is to say, that which is directly in contact with the fluid in the channel in question.

Of course, this arrangement corresponds to the formation of recessed areas near the corrugation bottom lines, with the same alternating distribution with respect to the opposite face of the plate. In this same preferred geometry at the face of the plate, the hollow deformations may advantageously be distributed symmetrically on either side of the corrugation bottom line. These hollow deformations of the face face correspond to hump deformations near the corrugation top lines for the opposite face.

Of course, the different deformations in bump and recess can be positioned at varying levels of the height of the corrugation, between the top line and the bottom line. However, care should be taken that the volume of the deformations hump does not exceed the main plane defined by the different lines of corrugation top, to allow easy stacking of different plates.

In practice, the characteristic criterion N can be substantially constant over most of the exchange surface of the plate, but it is also possible to form plates having different zones having distinct characteristic criteria.

Thus, in a particular case, the face of the plate may, in a first zone, have bump deformations which are alternately distributed and offset on either side of the corrugation top line, thus presenting a characteristic criterion in advantageous ranges. In a second zone, the hump deformations are instead distributed symmetrically on either side of the corrugation vertex line. This double configuration therefore makes it possible to generate different head losses in the two zones thus defined. There are thus preferred passage zones of the fluid, capable of compensating for the fact that the fluid can enter and leave the channel on the same side of a long edge of the plate.

In practice, the exchanger can be constituted by the association and the stack of identical plates, but also different plates depending on the desired exchange properties.

Similarly, the identical plates can be arranged in different ways depending on the orientation of the faces of the plates having a characteristic criterion in an advantageous range.

Thus, in a first variant, the plates may be assembled to define channels of a first type, which may be described as "symmetrical", defined by facing surfaces having a substantially identical characteristic criterion.

When the channels defined by the preferential faces have particularly advantageous properties in terms of exchange coefficient and pressure losses, it follows that the adjacent channels, formed with the faces of the plates, have their own intrinsic properties. lower. These exchangers formed with this type of stack are more particularly suitable for exchangers traversed by fluids having different types of flow, and in particular the exchangers of the evaporator or condenser type.

It can also be liquid / liquid exchangers in which the channels of lower pressure drops receive the higher flow rate.

In another variant embodiment, the plates may be assembled to delimit channels of a second type, which may be described as "asymmetrical", the arrangement being such that the faces of the plates having the same characteristic criteria N are all oriented in the same direction. In other words, the channels then have substantially similar properties, since they are delimited on one side by the face of a characteristic plate, and on the other side by a front side a priori, less efficient.

The exchanger thus produced has two very similar performance circuits, and can therefore be adapted to any type of liquid / liquid exchanger.

In the case of plates already mentioned, having areas of different natures on the same face, the latter are stacked to achieve, as mentioned, channels formed of substantially parallel sections of the first and second type already mentioned.

Although it is simpler to produce exchangers with identical plates by ensuring their rotation and reversal depending on the type of channel that is desired to achieve, the invention also covers variants in which the assembly is carried out. plates with different properties.

Similarly, the shape of the corrugations can be adapted according to the desired applications, and the invention is in no way limited to corrugations shaped chevrons as illustrated in the accompanying figures.

Brief description of the figures

• La figure 1 est une vue en perspective sommaire générale montrant l'agencement de différentes plaques intervenant dans un échangeur à plaques.
• Les figures 2 et 3 sont des vues en perspective sommaire schématiques d'une plaque montrée respectivement sur sa face endroit et envers.
• La figure 4 est une vue de détail en perspective sommaire illustrant le positionnement des creux et bosses caractéristiques.
• La figure 5 est une représentation schématique en plan de la figure 4.
• Les figures 6 et 7 sont des diagrammes illustrant l'évolution de différents paramètres représentatifs de l'échange en fonction du critère caractéristique N.
• Les figures 8, 9 et 10 sont des représentations d'assemblage de plaques conformes à l'invention, selon différentes variantes.

The manner of carrying out the invention, as well as the advantages which result therefrom, will emerge from the description of the embodiments which follow, in support of the appended figures in which:

• The figure 1 is a general summary perspective view showing the arrangement of different plates involved in a plate heat exchanger.
• The Figures 2 and 3 are schematic summary perspective views of a plate shown respectively on its front and back side.
• The figure 4 is a detail view in summary perspective illustrating the positioning of characteristic hollows and bumps.
• The figure 5 is a schematic representation in plan of the figure 4 .
• The Figures 6 and 7 are diagrams illustrating the evolution of different parameters representative of the exchange according to the characteristic criterion N.
• The Figures 8, 9 and 10 are representations of assembly of plates according to the invention, according to different variants.

Way of realizing the invention

As illustrated schematically in figure 1 , the exchanger (1) comprises different plates (2-5) assembled to define between them channels (6-8) of fluid circulation.

More specifically, each plate (2-5) has four holes (10-13) for connection with the inlet and outlet pipes of two fluid circuits (20, 21; 22, 23). On each plate, a peripheral seal (14) makes it possible to seal the channel created, including in said channel only two of the bores. In the illustrated form, the bores (10, 11; 12, 13) associated with the same channel are on the same large side of the plate (2), but the invention also covers variants in which the two bores associated with a channel lying on a diagonal of the plate.

As illustrated in figure 1 each plate (2-5) has corrugations (25) in the form of simple chevrons. In other variants not shown, the corrugations can also be in the form of multiple chevrons. The plates are alternately rotated 180 ° about their center, so that the herringbone corrugations are in opposition on both sides of the facing plates, at the same channel, to increase the level of disturbances of the circulating fluid. in the channel.

As illustrated in figure 4 when two plates defining the channel are facing each other, their respective corrugation vertex lines touch each other at contact points.

In accordance with the teachings of the patent EP 0 737 296 the plates have hollow and bump deformations which are distributed over the corrugations. In all the figures, only a portion of these hollows and bumps is shown to avoid overloading the drawings, and so as not to interfere with the understanding of the invention.

By convention, and as illustrated in Figures 2, 3 and 4 the hump deformations, corresponding to growths in relation to the viewed face of the plate, are represented by ovals. The hollow deformations are represented by rectangles, and therefore correspond to deformations sinking inside the plate, viewed on the face considered.

As illustrated in figure 2 the recessed deformations (30, 31) are arranged near a bottom line (32) of corrugations, while the hump deformations (33, 34) are located near a line (35) of the vertex corrugations. On the face (36) of the plate of the figure 2 the recessed deformations (30, 31) are located substantially opposite a corrugation bottom line (32). On the other hand, the bump deformations (33, 34) are arranged offset from their corrugation top line (35).

The reverse side (46) of the same plate is illustrated in FIG. figure 3 . It can be seen that the recessed deformations (30, 31) of the face face correspond to hump deformations (40, 41) on the reverse side, which are situated facing each other, on either side of the line of top (42) corrugations on the reverse side (46).

Similarly, the bump deformations (33, 34) of the locating face (36) correspond to recessed deformations (43, 44) seen from the reverse side (46). These recessed deformations (43, 44) are arranged offset and on either side of the corrugation bottom line (45), looking at the back face (46), the same corrugation bottom line (46). ) corresponding to a corrugation vertex line (35) on the location face (36).

As already mentioned, the invention lies in a particular positioning of the recessed and hump zones with respect to the contact points between plates. Thus, as illustrated in figure 4 the plate (25) contacts the facing plate (48) to define the channel (26) at a plurality of contact points. These contact points are located at the intersections of the corrugation vertex lines (35) of the plate (25) with the corrugation vertex lines (49) of the plate (48). The different points of contact (51-54) define elementary cells which have a general parallelogram shape, and more particularly a diamond shape when the chevrons of the two plates facing each other are of the same inclination. These rhombs can even be square when the rafters are perpendicular from one plate to another.

The location of the hollow and bump patterns is after projection in a plane P parallel to the main plane of the plate, also parallel to the plane defined by the set of contact points.

Deformations in hollow and hump are measured in this plane by projecting their center of gravity in the plane P. Thus, the boss (33) projects at the point (63) of the plane P, while the deformation in the hollow (30) is projected at the point (60) of the same plane. The position of these hollows and bumps is determined according to the invention, with respect to a reference point (65). This reference point is located on the plate (25), midway between a vertex line (35) and corrugation troughs (32).

This reference point is deduced from the point of contact (52) as being aligned with the latter with respect to the direction F corresponding to the flow direction of the fluid.

The projection (66) of this reference point (65) is shown on the plane P.

The invention resides in a positioning of bumps and depressions with respect to this reference point. This reference point is therefore located, from a point of the fluid flow, behind a contact zone between plates. The distances of hump and hollow are measured by projection on the line of corrugations (35). Thus, the distance D illustrated at figure 4 therefore corresponds to the difference, measured parallel to the corrugation vertex line, which separates the deformation into a hump (33) and the successive hollow deformations (30, 31).

The distance D ₁ corresponds to the difference, always measured parallel to the line of corrugations, which separates the projection (63) from the hump deformation (33) of the projection (66) of the reference point (65).

According to the invention, good results have been observed from a point of view of the operation of the heat exchanger when the ratio D ₁ / D is between 0.35 and 0.80, and more precisely close to 0, 55. These values are given for plates whose chevrons have an angle of the order of 60 °. More particularly, the optimum of this criterion N may be slightly different for chevron angles (10) which are also different.

The figure 6 illustrates the variation of a performance evaluation parameter of a heat exchanger. Thus, the efficiency parameter ζ is evaluated by comparing the performance of a plate used in a heat exchanger according to the invention with respect to the performance of a plate having no deformation hollow and hump. More precisely, this parameter ζ is calculated by measuring the ratio of the exchange powers, divided by the ratio of the pressure losses measured with these two types of plates, the ratio of the pressure drops being high to a power of the order of 0.33 to 0.37 depending on the type of exchanger.

Thus, the criterion ζ shown in figure 6 shows very clearly a substantial gain of the order of 10% in the range of the criterion N considered, with an optimal when the criterion N is around 0.55.

It is recalled in this respect that the patent of the prior art EP 0 737 296 taught the positioning of deformations in hump right behind the points of contact between plate, corresponding to a situation where the criterion N characteristic is close to 0.

Complementarily, the pressure losses measured with the plates used in a heat exchanger according to the invention surprisingly show a very clear improvement in the range of the characteristic criterion. These pressure drops are lower by about 30%. relative to the pressure losses measured in the situation corresponding to the teachings of the patent of the aforementioned prior art.

According to another aspect of the invention, the characteristic plates may be arranged relative to each other in different configurations, depending on the faces they have facing each other. To facilitate the understanding of Figures 8 to 10 only the hump zones have been represented (by dots) around the corrugation vertex lines. So, in the configuration illustrated in the figure 8 , the different plates are arranged so that they have on their faces in the figure faces on which the bump deformations (70) are arranged symmetrically with respect to lines (71) corrugation top. The visible faces of the plates of the figure 8 correspond to the visible side illustrated at figure 3 .

The set of plates (69) of the figure 8 have all their identical faces oriented in the same direction. These plates are stacked by making a plate to another pivoting around their central point.

It can be deduced that the hidden face of each of the plates (69) corresponds to the configuration illustrated in FIG. figure 2 in which the hollow deformations are each arranged symmetrically with respect to the corrugation bottom lines. Complementarily, the bump deformations on this hidden face, (corresponding to the recessed zones not shown on the visible faces of the figure 8 ) are arranged alternately and offset from the lines top of corrugations, coming in front of the visible faces of the plates of the figure 8 .

The channels (73) thus defined thus have very substantially identical properties for the two fluid circuits.

It is possible to use an opposite configuration as illustrated in figure 9 . In this case, the two end plates (80, 82) shown have a visible face which corresponds to the configuration illustrated in FIG. figure 2 wherein the hump deformations (83, 84) are alternately arranged and offset from the corrugation vertex lines (85).

In contrast, the intermediate plate (81) has a visible face on the figure 9 which corresponds to the configuration of the figure 3 wherein the hump deformations (86, 87) are located symmetrically with respect to the corrugation vertex lines (88). It follows that the channel (89), defined between the first (80) and the second (81) plates, has two substantially identical faces, corresponding to the visible face of the intermediate plate (81). At this channel (89), the bump deformations are therefore on each of the opposite faces arranged symmetrically with respect to the corrugation vertex lines.

Conversely, in the channel (90) defined between the intermediate plate (81) and the plate (82) located further back, the two facing faces have the same configuration corresponding to that of the figure 2 .

In this case, the hump deformations (84, 85) of the opposing faces are arranged alternately and offset from the corrugation vertex line. It is therefore conceivable that the overall thermal performances as well as the pressure losses of the two channels (89, 90) thus defined are different, and are more suitable for producing exchangers having a flow typology. different between the two circuits, such as for example evaporators or condensers.

Of course, the two configurations mentioned above can be combined within the same plate, as illustrated in FIG. figure 10 . Thus, the same plate can present on the same face the two configurations. More specifically, as illustrated in figure 10 the intermediate plate (94) has on one side hump deformations (95) arranged symmetrically with respect to the corrugation vertex lines (96).

Complementarily, on the opposite side, the bump deformations (97, 98) are arranged in an offset and alternating manner. It follows that the pressure losses thus generated are different in the two longitudinal portions (99, 100) parallel to the channel (101). This arrangement is optimized to reduce the pressure losses corresponding to the fraction (100) of the channel located farthest from the points (103, 104) of entry and exit of the fluid, so as to homogenize as much as possible the flow on the width of the canal.

The different plates of the exchanger are stacked by providing them pivoting in the same plane around their central point.

It follows from the foregoing that the plate heat exchangers according to the invention have significantly better performance than the plate heat exchangers of the prior art, both with regard to the heat exchange coefficient and the level of pressure drop.

The exchangers can be constructed by arranging characteristic plates in different ways, adapted to the type of fluid and flow to go through the exchangers.

Claims (10)

1. Heat exchanger, comprising a plurality of plates (2-5) assembled to define fluid circulation ducts (6-8) between them, each plate comprising undulations (25) or corrugations defined between corrugation peak lines (35) and corrugation trough lines (32), at least one portion of the plates comprising sunken deformations (30, 31) and raised deformations (33) situated between the corrugation peak and trough lines, characterized in that on at least one plate, on its front face facing a duct, and on the inside of an elementary cell defined between four consecutive points of contact (51, 54) with the adjacent plate (48) delimiting the said duct, the raised deformations (33) and sunken deformations (30, 31) are located such that the criterion N = D₁/D lies between 0.35 and 0.8 in which:

   • D1 is the distance measured in a plane (P) parallel to the main surface of the plate, and parallel to the corrugation peak line (35) separating:

   · the centre of the raised deformation (33) closest to one of the points of contact (52);

   · a reference point (65) situated at an equal distance from the corrugation peak line (35) and the corrugation trough line (32), the said reference point (66) being aligned with the said contact point (52) in the direction of flow of the fluid (F).

   • D is the distance measured in a plane parallel to the main surface of the plate and parallel to the corrugation peak line (35) separating:

   · the centre of the raised deformation (33) closest to one of the points of contact (52);

   · the centre of the closest sunken deformation (30) in the direction of the corrugation peak line (35).
2. Exchanger according to Claim 1, characterized in that, on at least one portion of the front face of a plate (25), the raised deformations (33, 34) are distributed alternately and offset either side of the corrugation peak line (35).
3. Exchanger according to Claim 1, characterized in that, on at least one portion of the front face of a plate, the sunken deformations (30, 31) are distributed symmetrically either side of the corrugation trough line (32).
4. Exchanger according to either one of Claims 2 or 3, characterized in that on the front face of a plate (94), in a first zone (100), the raised deformations (97, 98) are distributed alternately and offset either side of the corrugation peak line (96), and, in a second zone (99), the raised deformations (95) are distributed symmetrically either side of the corrugation peak line (96).
5. Exchanger according to Claim 1, characterized in that the plates (80-82) are assembled to delimit the ducts of a first type (73), defined by opposite surfaces having a substantially identical criterion N.
6. Exchanger according to Claims 2 and 3, characterized in that the plates (69) are assembled to delimit ducts (73) of a second type, the faces of the plates having substantially identical criteria N being oriented in the same direction.
7. Exchanger according to Claim 4, characterized in that the plates (94) are assembled to delimit ducts formed of substantially parallel sections of the first type and of the second type.
8. Exchanger according to Claim 1, characterized in that it is composed of identical plates.
9. Exchanger according to Claim 1, characterized in that the corrugations (25) are in the form of single or multiple chevrons.
10. Exchanger according to Claim 1, characterized in that the chevrons (25) have an angle of aperture of 60°.

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