EP1172625A2 - Heat exchange fin for heat exchanger with brazed plates, and heat exchanger using same - Google Patents

Abstract

The heat exchanger fin system, made from corrugated and perforated or slitted metal sheet, has the main direction (F1) of its corrugations (14) lying at an oblique angle to its two lateral edges (13). The general direction (F2) with least resistance to the fluid flow forms a substantial angle with the main direction of corrugation and lies parallel to the lateral edges, while the sides of the corrugations have ridges to promote a transverse fluid movement relative to the general direction of least resistance and to create turbulence.

Description

The present invention relates to a fin heat exchanger for plate heat exchanger brazed, of the type comprising a corrugated perforated product and / or flat which has a main direction of undulation and which is bounded by two side edges.

The invention applies for example to lines main heat exchange systems air distillation, which put in exchange relation indirect thermal incoming air and cold products from the air distillation column.

Brazed plate heat exchangers are commonly used because they offer a large area heat exchange in a particularly compact volume, and, moreover, they are relatively easy to manufacture.

These exchangers, often made of aluminum or aluminum alloy, consist of a plurality of parallel plates, usually rectangular, between which are arranged on the one hand of the spacer waves or fins of various geometries, and on the other hand bars for closing shaped fluid flow passages flat delimited by the plates. The flows can be against the current, co-current or cross-currents.

The fins have the function of increasing the heat exchange surface and therefore performance overall heat transfer. They transfer into effect of heat fluxes by conduction to the plates adjacent, which they are secured by brazing.

The fins are produced very economically from a folded, perforated, punctured and / or flat product stamped. The basic wave may have a cross section substantially square, rectangular or triangular. We basically know the fins called "waves straight lines ", which are a simple corrugated sheet," waves perforated "," herringbone waves ", with generatrices wavy, "louvered waves", whose wave legs have punctures, and "serrated waves", or "offset partial ", in which, at regular intervals along generators, we produce a transverse shift of the wave, generally half a wave step.

In all these known fins, the direction main ripple, which is the middle direction of ripple in the case of herringbone waves, defines the direction of least resistance to fluid flow.

In each passage of the exchanger, a part main of the passage length constitutes the part heat exchange proper, which is furnished with a fin called heat exchanger fin. In some case, this part is bordered by distribution parts fluid inlet and outlet lined with fins distribution.

The heat exchange part is delimited by two parallel side bars on two sides opposite plates, and the main direction of ripple of the heat exchange fin is parallel to these bars of closure, with the exception sometimes of limited regions where this main direction is perpendicular to the bars of side closures (so-called “hard-way” arrangement) for create a local pressure drop. In what follows, we will abstraction of fins in hard way.

In the distribution parts, the fins have a general ripple direction very inclined by compared to that of the heat exchange fins.

The invention aims to increase the compactness of brazed plate heat exchangers by improving their thermal performance.

To this end, the invention relates to a fin heat exchange of the aforementioned type, characterized in that the main ripple direction is oblique to the at the two side edges, and in that the fin has a general direction of least resistance to the flow of a fluid which is substantially parallel to the two edges side.

The invention also relates to a heat exchanger brazed plate heat, of the type comprising a plurality of parallel rectangular plates that define between passages of generally flat shape, and, in each passage, a heat exchange fin, each fin forming a spacer between two plates, as well as bars side closure, and in which an exchange fin thermal is as defined above.

• la Figure 1 représente en perspective, avec arrachements partiels, un échangeur de chaleur à plaques brasées suivant l'invention ;
• la Figure 2 représente un passage de cet échangeur de chaleur ;
• la Figure 3 représente en perspective une partie d'une ailette suivant l'invention ;
• la Figure 4 représente la même ailette, prise en coupe suivant le plan médian IV de la Figure 3 ;
• les Figures 5 et 7 représentent en perspective deux autres modes de réalisation de l'ailette de l'invention ; et
• les Figures 6 et 8 représentent respectivement les ailettes des Figures 5 et 7 en coupe suivant les plans médians VI de la Figure 5 et VIII de la Figure 7.

Examples of embodiments of the invention will now be described with reference to the appended drawings, in which:

• Figure 1 shows in perspective, with partial cutaway, a brazed plate heat exchanger according to the invention;
• Figure 2 shows a passage of this heat exchanger;
• Figure 3 shows in perspective part of a fin according to the invention;
• Figure 4 shows the same fin, taken in section along the median plane IV of Figure 3;
• Figures 5 and 7 show in perspective two other embodiments of the fin of the invention; and
• FIGS. 6 and 8 respectively represent the fins of FIGS. 5 and 7 in section along the median planes VI of FIG. 5 and VIII of FIG. 7.

The heat exchanger 1 shown in Figure 1 is for example a cryogenic heat exchanger. It is consisting of a stack of rectangular plates parallel 2 all identical, which define them a plurality of passages for fluids to be introduced indirect heat exchange relationship. In the example shown, these passages are successively and cyclically passages 3 for a first fluid, 4 for a second fluid and 5 for a third fluid.

Each passage 3 to 5 is bordered by bars of lateral closure 6 and end closure 7 which delimit it in leaving free windows 8 for inlet / outlet of the fluid corresponding. In each passage are arranged spacer waves or wavy fins serving both thermal fins, spacers between the plates, especially during soldering and to avoid any deformation plates when using fluids under pressure, and for guiding the flow of fluids. These fins are, over most of the length of the passage, fins 9 heat exchange. In their regions adjacent to the windows, these fins 9 are extended by distribution fins 10. These distribute the fluid entering from an inlet window to the entire width of the fin 9, or collect the fluid leaving all this width up to an exit window.

The stacking of plates, closing bars and spacer waves are generally made of aluminum or aluminum alloy and is assembled in one oven brazing operation.

Fluid inlet / outlet boxes 11 general semi-cylindrical, are then welded to the body exchanger thus produced so as to cover the rows of corresponding input / output windows 8, and they are connected to pipes 12 supply and evacuation of fluids.

We have shown schematically in Figure 2, one of the passages of the same exchanger, namely a passage 3. The heat exchange fin 9 has a main direction ripple F1 which forms a positive acute angle α, typically between 1 ° and 30 °, and preferably between 2 ° and 10 °, with the longitudinal direction F2 passage, which is that of the closing side bars 6.

However, the arrangement of the fin 9 is such that the general direction of least resistance to flow in the passage remains substantially the direction F2.

We also recognize in Figure 2 the two distribution fins 10, adjacent to windows entry / exit 8 of the passage. The angle β made by the ripples of these distribution fins with the direction F2 is much greater than the angle α, and typically close to 75 °, and their general direction of least flow resistance is their main direction of ripple, so that they can fulfill their function vending.

The fin 9 is made from a material made of folded sheet whose longitudinal direction is perpendicular to F1. This material is, after folding, cut to length along two lines 13 parallel to the direction F2, which leads to several wave mat 14, the number of three in Figure 2, in the form of a parallelogram (for the or intermediate mats) or rectangular trapezoid or right triangle (for both end mats).

Figures 3 to 8 show three modes of different construction of the fin 9.

In the embodiment of Figures 3 and 4, the fin has a corrugation with a rectangular section, with wave bases 15 and wave vertices 16 connected by wave legs 17.

Each leg 17 is provided at intervals regular, hearing 18 pushed back on the side of the leg which receives the fluid flow (the left side in Figures 3 and 4) and which are open upstream of this flow. So, as shown by arrows in Figure 4, a vein fluid guided in the direction F1 between two legs 17 is partially deviated transversely to this direction by hearing 18.

So, overall, the direction of least resistance to flow of the fin 9 is substantially the direction F2, when one chooses appropriately the shape and dimensions of the gills 18. In addition, the inclination F1 and the vents 18 give the flow a two-dimensional and turbulent configuration which favors the efficiency of heat exchange.

In the embodiment of Figures 5 and 6, the fin 9 is of the "serrated" type. It thus comprises, at a regular interval along the direction F1 called "tightening length" l , a lateral offset d , alternately on one side and the other, which is generally equal to half the distance between two legs 17, called "no tightening" p . The fin thus comprises parallel offset planes P which, in top view (FIG. 4), are parallel offset lines 19.

Each elementary leg 17 has its leading edge folded at right angles over its entire height, which defines a deflection plate 20. All the plates 20 are oriented on the same side, namely on the side of the legs 17 which receives the fluid flow.

The platelets 20 have the effect of reducing the fluid passage section on the side where they are provided and to increase this passage section on the opposite side. Thus, as seen in Figure 6, each vein of fluid guided between two legs 17 sees its flow favored in a direction close to F2, even oblique in the opposite direction to F1 with respect to F2.

Given the turbulence generated in the fluid, the fin 9 generally has, as previously, a direction of less resistance to the flow close to F2, with an appropriate choice of fin parameters and the size of the pads 20.

• sur une rangée sur deux de jambes 17, celles-ci comportent alternativement une échancrure à la fois sur leur bord d'attaque et sur leur bord de fuite, et aucune échancrure ;
• sur les autres rangées, les jambes 17 comportent alternativement une échancrure 21 sur leur bord d'attaque et une échancrure sur leur bord de fuite.

The embodiment of Figures 7 and 8 differs from the previous one by the elimination of the pads 20 and by the presence of notches 21 over the entire height of certain leading edges and certain trailing edges of the legs 17. More precisely:

• on a row on two of legs 17, these alternately comprise a notch both on their leading edge and on their trailing edge, and no notch;
• on the other rows, the legs 17 alternately have a notch 21 on their leading edge and a notch on their trailing edge.

The resulting effect is much the same as that described above with reference to Figures 5 and 6.

Claims (11)

Heat exchange fin for heat exchanger with brazed plates, of the type comprising a corrugated perforated and / or punctured product which has a main direction of undulation (F1) and which is delimited by two lateral edges (13), characterized in that that the main direction of undulation (F1) is oblique with respect to the two lateral edges (13). A fin according to claim 1, characterized in that it has a general direction (F2) of least resistance to the flow of a fluid which forms a substantial angle with the main direction of undulation (F1). A fin according to claim 2, characterized in that the general direction (F2) of least resistance to the flow of a fluid is substantially parallel to the two lateral edges (13). Fin according to one of claims 2 to 3, characterized in that it has on its wave legs (17) conformations (18; 20; 21) which promote a displacement of the fluid transversely to the general direction of least resistance to the flow (F2). Fin according to one of claims 1 to 4, characterized in that it has on its wave legs (17) conformations (18; 20; 21) creating turbulence in the fluid. Fin according to claim 4 or 5, characterized in that the conformations (18) consist of vents provided on the side of the wave legs (17) which receives the flow of the fluid and open upstream of this flow . A fin according to claim 4 or 5, of the serrated type, characterized in that the conformations consist of plates (20) projecting from the side of the wave legs (17) which receives the flow of the fluid. Fin according to claim 7, characterized in that the plates (20) are provided on the leading edge of the wave legs (15). Fin according to claim 4 or 5, of the serrated type, characterized in that the conformations consist of notches (21) of the leading edges and / or trailing edges of the wave legs (15) arranged on the lines offset (19) of the fin (9) so as to increase the cross-section of the fluid in a direction which, relative to the main direction of undulation (F1), 'approaches the direction (F2) of said side edges (13). Brazed plate heat exchanger, of the type comprising a plurality of parallel rectangular plates (2) which define between them passages (3, 4.5) of generally flat shape, and, in each passage, a heat exchange fin ( 9), each fin forming a spacer between two plates, as well as lateral closing bars (6), characterized in that at least one heat exchange fin (9) conforms to any one of claims 1 to 9 . Heat exchanger according to claim 10, characterized in that it constitutes a main heat exchange line of an air distillation installation.

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