EP1029933B1 - Device for heat exchanging with a flat product - Google Patents

Abstract

Uses caisson (11) incorporating on a leading face several thin plates (12) forming a conduit for the ejection of gas in the direction of one surface of the flat product. A device for exchanging heat with a flat product defiling in front of this device comprises device for putting at least one caisson (11) under gaseous pressure. The caisson (11) incorporating on a leading face several thin plates (12) forming a conduit for the ejection of gas in the direction of one surface of the flat product. These thin plates (12) are superimposed on each other following the direction of defilement of the flat product and make up an orifice for the exit of the gas extending across the width of the flat product. The caisson (11) has a width within the width of the flat product that is sufficient to allow the evacuation of gas from both sides of the caisson (11).

Description

The present invention relates to a heat exchange device with a flat product.

It applies more particularly to any flat product, in particular strip or in sheets, or even formed of a sheet of parallel threads.

It relates more specifically to the field of processing thermal of rolled products, such as rolled metal, which pass on rollers and pass successively through treatment chambers. We use such continuous annealing or galvanizing lines for example in the manufacture of steel sheets for car bodywork. Steel can be brought to temperatures up to 600-900 ° C. Rapid cooling and uniform of these products is then necessary in order to bring the temperature down of the product at a temperature below 500 ° C depending on the desired quality.

We know a heat exchange device as described in the French patent FR 2 738 577 in the name of the Applicant, which allows continuously cooling a rolled product moving past a series of blades which form conduits for ejecting a cooling gas.

This device includes gas pressurization means at least one plenum chamber, the caisson comprising on a front face several blades forming a conduit for the ejection of the gas direction of a surface of the rolled product, the blades being superimposed to others according to the direction of travel of the rolled product and constituting a gas outlet opening extending across the width of the rolled product.

Each space separating two superimposed blades has a depth in a direction perpendicular to the surface of the rolled product and a width in the longitudinal direction of the rolled product sufficient to allow gas evacuation without disturbing the gas outlet of the adjacent blades.

Thus, the space provided between the blades facilitates the evacuation of gas at level of the surface of the rolled product and does not interfere with the emission of gas in outlet of the blade opening.

Indeed, if no precaution is taken to evacuate the gases hot after their impact on the product, as we increase the gas flow, the heat transfer coefficient, therefore the speed of cooling, stops growing and there is a "saturation" effect. This phenomenon is described for example in the article by C. Brugnera and AL., Revue de Métallurgie, December 1992, page 1098, fig. 8, where we see that beyond 500 mm water column (CE) pressure at the orifice, the speed of cooling no longer increases, even increasing pressure to 800 mm THIS.

In the case of French patent FR2738577, to completely avoid the formation of a hot gas blanket on the surface of the rolled product, the space between the blades must be dimensioned so that the return speed gas is less than 20 m / s, which means that if the gas is taken up laterally by only one side, that the ratio of the sum of the half-flows of two blades superimposed (i.e. the flow rate of a blade) on the passage section between two blades is less than 20. If the product to be treated is wide and the blade of a single piece across the width of the product, and in addition the coefficient of transfer required is high, excessive blade depths and difficult to install must be provided.

The present invention aims to improve such a device for exchanging heat, and in particular to facilitate the evacuation of gas from the device after its impact on a flat product.

The invention thus relates to a heat exchange device with a flat product as defined in claim 1.

Thanks to the reduced width of the pressurization box gas, the evacuation of gases after impact on the surface of the flat product, can be made on both sides of the box, opposite the blades forming gas pipe on the front of the box.

The outgoing gas flow is therefore directed towards the rear of the flat product, without interfering with the emission of gas through the orifices of the blades. All risk of gas stagnation on the surface of the treated product is thus carefully avoided, as well as any gas flow parallel to the surface to treat both in the width direction and in that of the scrolling of the product.

Preferably, each blade flares towards the flat product of so that the gas, after impact on the flat product, can return to the back of the device, on each side of the box.

According to a preferred characteristic of the invention, the device heat exchange comprises gas outlet openings after ejection, located in a plane defined by a rear face opposite to said front face of the caisson.

The evacuation from the back of the box avoids any movement of gas along the surface of the flat product as happens in conventional devices in which the boxes are continuous or arranged side by side and prevent the return of the cooling gases to the rear. Unlike previous devices in which the evacuation of gases is carried out on the sides of the device, the gas can be evacuated from the device heat exchange according to the invention without generating cooling preferential from the edges of the flat product.

According to a preferred characteristic of the evacuation, the device heat exchanger comprises at least two boxes arranged in the width of the flat product, the spacing between said boxes being such that the gas is evacuated between said boxes at a lower speed or equal to 20 m / s.

This ensures regular evacuation of the gas towards the rear of the device, without the risk of turbulence forming which could harm the homogeneity of heat exchanges.

According to an advantageous and practical characteristic of the invention, the ratio of half the gas flow rate in m ³ / s at the outlet of two adjacent strips along the width of the product over the section in m ² of the space separating said boxes comprising said blades is less than 20, said section extending in a plane parallel to the flat product and to the running direction of the flat product.

According to another preferred characteristic of the invention, the ratio of the speed of the gas in a box over the speed of the gas leaving the blades integral with said box is less than 0.2.

Thanks to this significant difference in gas velocities in the box and at the outlet of the blades, the box forms a gas tank under pressure almost without circulation, ensuring a uniform speed for ejection of gases.

According to another preferred characteristic of the invention, the means gas pressurization systems have several fans adapted to supply gas to one or more boxes.

The pressure of each box can thus be regulated independently or by sub-group of boxes, allowing to adjust, in the width of the flat product, the cooling rate depending on the profile desired thermal.

Other features and advantages of the invention will become apparent again in the description below.

• la figure 1 est une vue schématique d'une installation de refroidissement comprenant des dispositifs de refroidissement conformes à l'invention ;
• la figure 2 est une vue schématique de coté de deux lames superposées d'un dispositif d'échange de chaleur conforme à l'invention ;
• les figures 3A et 3B sont des coupes schématiques d'exemples de lames, selon la ligne III-III à la figure 2 ;
• la figure 4 est une vue de derrière d'un dispositif d'échange de chaleur conforme à un mode de réalisation de l'invention;
• la figure 5 est une vue analogue à la figure 4 d'un dispositif échange de chaleur placé dans une enceinte étanche aux gaz ;
• la figure 6 est une vue en coupe suivant la ligne VI-VI à la figure 5 ; et
• la figure 7 est une vue en coupe suivant la ligne VII-VII à la figure 5.

In the appended drawings, given by way of nonlimiting examples:

• Figure 1 is a schematic view of a cooling installation comprising cooling devices according to the invention;
• Figure 2 is a schematic side view of two superimposed blades of a heat exchange device according to the invention;
• Figures 3A and 3B are schematic sections of example blades, along the line III-III in Figure 2;
• Figure 4 is a rear view of a heat exchange device according to an embodiment of the invention;
• Figure 5 is a view similar to Figure 4 of a heat exchange device placed in a gas-tight enclosure;
• Figure 6 is a sectional view along line VI-VI in Figure 5; and
• Figure 7 is a sectional view along line VII-VII in Figure 5.

We will describe below by way of example a device for cooling of a flat product which is formed by a device for exchanging heat according to the invention.

Of course, the invention may also apply to a device for heating a flat product.

Referring first to Figure 1, an installation of continuous cooling of a flat product such as a rolled product 1 can include several cooling devices 10, here four in number, distributed over the path of the rolled product moving between rolls of transport 2. In a nonlimiting manner, the laminated product scrolls vertically between the cooling devices 10 generally arranged two by two, on each side of the rolled product in order to simultaneously cool the product by its two faces.

The transport rollers 2 stabilize the rolled product 1. They can cause a slight deflection to the rolled product 1, lower or equal to 15 ° in order to limit the vibration of the rolled product 1.

Such a cooling installation can be used by example in a continuous annealing line for strip processing steel, in which the rolled product passes by vertical passes in different treatment chambers.

These steel strips have a thickness of between 0.15 and 2.3 mm and their width can reach up to 2 m.

It is important during the heat treatment of steel to cool very quickly, homogeneously the bands to avoid any deformation Of the band.

For this, the cooling device 10 includes boxes 11 which are adapted to contain a pressurized gas.

Each box 11 comprises several blades 12 which form conduits for the ejection of gas towards the rolled product 1 to be cooled.

These blades 12 are superimposed on each other as illustrated in FIG. 1, in the direction of travel of the rolled product 1, so as to cool the surface of the product as it travels through the exchange device heat 10.

The height of the stack of blades 12 over the height of a box It is preferably less than or equal to 6 m.

These blades 12 have at least one outlet 13 as shown in Figure 2, which extends across the width of the rolled product 1. This outlet orifice 13 thus opens at the end of the conduit formed by the blade 12 which extends from the box 11 in the direction of the rolled product 1.

Preferably, the cross section of the blades 12, in a plane perpendicular to the rolled product 1, decreases from the box 11.

The outlet orifices 13 may be circular holes, rectangular, oblong, etc., or small slits made at the end of each blade 12. The blade 12 could also have only one orifice for outlet 13 forming a slit opposite the rolled product 1.

Each space separating two superimposed strips 12 (hatched on Figure 2) has a depth in a direction perpendicular to the product laminate 1 and a width in the longitudinal direction of the laminate product 1 sufficient to prevent the accumulation of cooling gas near the surface of the rolled product 1.

Thus, the depth of the separation spaces of the blades 12 is greater than 200 mm, and preferably greater than 300 mm.

The arrangement of these blades 12 and their orifices 13 is described in particular in French patent FR 2738577.

In general, the number of blades 12 of the device 10 and the number of openings 13 are such that the total section formed by the openings 13 is between 1% and 5% of the surface covered by all of the blades 12, and preferably between 2 and 4% of this area.

In addition, the blades 12 of a box 11 are dimensioned such that so that the evacuation of the gas in the section S between these blades 12 is carried out at a speed less than or equal to 20 m / s at any point.

The section corresponds to the section of space taken in the plane of Figure 2, perpendicular to the rolled product 1 and parallel to the direction of scrolling of the rolled product 1.

The speed of the gas after its impact on the product is thus maintained, in the spaces between the blades 12, under a critical value of 20 m / s in order to limit the phenomena of turbulence in these spaces which would interfere with the evacuation of the gas.

More specifically, the passage section between two superimposed blades 12 is equal to the product of the depth P of this space between two blades 12 by the average free height W between two blades 12: W = (a + b) / 2 where a is equal to the distance separating the blades 12 at the front face of the box 11, and
b is equal to the distance separating the blades 12 at the outlet orifices 13.

The depth P can be constant in the width of the blade 12, or variable, as illustrated in FIGS. 3A and 3B, if we want to give the gas flow back a speed more directed towards the rear of the device.

A partition 12a thus extends between the superimposed blades 12, at from the casing 11, so that the depth P at the center of the blade 12 is weaker than at its ends.

In general, depth is a continuous function P (x) which varies along the distance x from the axis of symmetry of the blade 12 (in the case of FIG. 3A where a symmetrical return of the gas is produced by the two sides) or from one end of the blade 12 (in the case of FIG. 3B where gas return is only carried out on one side of the blade).

In the case of FIG. 3A, the flow between two blades 12 at a distance x from the axis of symmetry is equal to qx / l where q is the flow per blade (m3 / s) and I the width of the end of the blade 12 parallel to the width of the product with x≤I / 2. The cross-section for the return gas at the same distance x is equal to wP (x). Limiting the return speed to 20 m / s therefore implies that, for any value of x between 0 and I / 2, we have: P (x) ≥qx / 20.Iw, x, I and w being expressed in meters.

Similarly, in the case of FIG. 3B, the condition is also: P (x) ≥qx / 20.Iw, x varying this time between 0 and I.

In this way, the gas escaping between the blades can be evacuated to the two ends of these in the case of Figure 3A, so that the extraction speed limit is only reached when the flow q / 2 of half a width of blade divided by the section S of passage between two blades is equal to 20, i.e. q / S = 40.

Compared to French patent FR 2738577, extracting the gas by the two sides of the blade therefore makes it possible to reduce the section to S = q / 40 at place of S = q / 20.

As illustrated in FIG. 4, and in accordance with the invention, the cooling device comprises at least one box 11, here in number of five. These boxes 11 are distributed across the width of the rolled product 1 and extend in the longitudinal direction of the moving laminated product, parallel to each other.

The width of each box 11 and the distance between the boxes 11 allow the evacuation of gas between boxes 11 without disturb the gas outlet of the blades 12.

This distance, denoted D _1-2 or D _2-3 in FIG. 4, may have a different value from one pair of boxes 11 to another pair.

In this example, the boxes 11 have a cross section which is substantially parallelepiped, the distance between the boxes 11 corresponding to the distance separating their flanks placed opposite.

Gas outlet openings 14 after ejection are thus located between the boxes 11, in a plane defined by the rear faces opposite to the front panels 11.

The gas can thus be recovered on a rear face of the device heat exchange 10, opposite the rolled product 1, which avoids gas circulation along the surface of the rolled product 1 and a greater cooling of the edges of the rolled product 1 than at its center.

Preferably, the ratio of half the gas flow rate in m ³ / s at the outlet of two adjacent strips 12 along the width of the product over the section in m ² of the space separating the boxes 11 comprising these strips 12 is less than 20.

This section, taken in the plane of Figure 3, extends in a plane parallel to the rolled product 1 and to the direction of travel of the rolled product 1.

It corresponds, in the plane of the front faces of the boxes 11, to the product of the distance L (pitch, or center distance) separating two superimposed blades 12 by the distance D _1-2 or D _2-3 separating two neighboring boxes 11.

Thus, in the example of Figure 6 (q _1/2 + q _2/2) / _1-2 LD ≤ 20 and (q _2/2 + q _3/2) / _2-3 ≤ LD 20.

When the device comprises, as here, several boxes 11 arranged parallel in the width of the rolled product 1, the section of the space separating the boxes 11 is equal to the sum of the sections of the spaces separating the boxes 11 two by two.

Here, by way of nonlimiting example, this section would be equal to the sum of the sections, taken from left to right in FIG. 4, L x (D _3-4 + D _2-3 + D _1-2 + D _{1 -2} + D _2-3 + D _3-4 ).

For example, the distance L is less than or equal to 300 mm, and preferably less than or equal to 150 mm.

In the case where the blades are symmetrical in their plane (Fig. 3A), the relationship of the type (q _1/2 + q _2/2) / D ≤ 20 or _1-2 .L (q ₁ + q ₂₎ / D _1-2 .L ≤ 40 is respected, which allows the spaces between the boxes to be fixed: D _ij ≥ (q _i + q _j ) / 40 L where q _i and q _j represent the flow rates respectively (m ³ / s ) of a blade of the adjacent box i and of the box j, and D _ij the width (m) of the free space between the boxes i and j.

The blades 12 of each box 11 are further distributed regularly on a front face of the box 11 in the direction of scrolling of the laminated product, each blade 12 of a first box 11 being adjacent to a blade 12 of a second box 11 in the plane defined by the gas outlet ports 13 (see in particular Figure 6).

Thus, although the boxes 11 are spaced from each other to facilitate the evacuation of the cooling gases, the blades 12 have a profile substantially divergent in the transverse plane of the rolled product so as to constitute at their ends, all adjacent in this transverse plane, a uniform gas outlet orifice 13 over the entire width of the rolled product 1. This port 13 may be formed of a single slot or a series of small ports evenly distributed over the entire width of the device.

The width of the gas outlet 13 in the width of the product laminated, is thus greater than the width of the box 11.

Furthermore, it is preferable that the ratio of the speed of the gas in a box 11 on the speed of the gas leaving the blades 12 secured to the box 11 remains less than 0.2.

Thus, the speed of the gas in each box 11 can be of the order 10 m / s while the speed at the output of the blades 12 can reach and exceed 150 m / s.

The boxes 11 thus form reservoirs of pressurized gas practically without circulation, which allows a regular flow gas leaving the blades 12.

Each box 11 has a gas supply opening 15 under pressure which can be connected to pressurizing means gas such as a fan 16 (see Figure 1) or a compressor.

The fan 16 is intended to introduce a large flow of gas pressure cooling in each box 11.

These feed openings 15 are arranged in this example in staggered in the rear faces of the boxes 11.

The gas pressurizing means include in this example several fans 16 (see FIG. 1) adapted to supply gas to a or more boxes 11.

Preferably, when the cooling device comprises like here an odd number of boxes 11, the means of putting under gas pressure include a fan 16 adapted to supply the casing central 11 and at least one other fan 16 adapted to supply boxes 11 arranged symmetrically on either side of the central box 11.

Here, the cooling device can include three fans, a first fan being connected to the central box, a second fan being connected to the intermediate boxes and a third fan being connected to the banks of the banks.

Preferably, these fans are driven by motors variable speed.

We can thus independently regulate the pressure in the boxes so as to ensure transverse homogeneity of the cooling. We can further adjust the cooling intensity to the width of the rolled product 1 depending on the desired thermal profile.

Similarly, if the width of the product to be treated is for example less or equal to the total width of the central box and the two boxes intermediate, the fan supplying the banks of the banks can be stopped or idle to save energy.

As further illustrated in Figure 6, the cooling device 10 is incorporated in a gas-tight enclosure 17, a discharge orifice gases 18 being provided in a rear wall 17a of the enclosure 17, opposite to the front face of the boxes 11.

The gas outlet 18 is preferably located in the center of the rear wall 17a of the enclosure 17, halfway up the cooling 10 and has substantially the same width as this (fig. 5).

This sealed enclosure 17 can be used in cases where, for avoid oxidizing the rolled product 1 during its cooling, it is necessary to cool under a protective atmosphere. For example, a cooling gas is used instead of air. mixture of nitrogen and hydrogen, low in hydrogen content in order to use a reducing but not explosive gas. The proportion of hydrogen is preferably less than or equal to 5%. This gas could also be pure nitrogen.

The gas can possibly be recovered at the outlet of the orifice evacuation 18 to be continuously recycled in the means of placing under gas pressure. Conventionally, recycling includes a step of gas recovery, a step of cooling it and a step of reinjection through the feed openings 15 into the boxes 11.

As shown in Figures 5, 6 and 7, the cooling 10 preferably comprises adjustment means 19 adapted moving the device 10 in a direction perpendicular to the rolled product 1.

Thus, the device as a whole can be brought together, in a working position illustrated in Figure 7, or away from the rolled product 1 as illustrated in figure 6.

This remote position makes it possible in particular to separate the device from cooling of the moving product 1 in the event of an incident, for example when the rolled product is deformed and forms extra thicknesses which could damage the blades 12 of the cooling device 10.

It is thus possible to modify the distance separating the outlet orifices 13 blades 12 from the surface of the rolled product in order to regulate the conditions of cooling.

The adjustment means 19 may comprise axes 20 integral of the frame 21 of the device on which the boxes are mounted.

Here, by way of example, the cooling device 10 comprises four axes 20, arranged in pairs at the top and bottom of the device 10, each side of this device.

Actuating means (not shown) allow conventionally to move these axes back and forth, in a direction perpendicular to these axes, between the two positions defined above. These actuating means can be, for example, motors for preferably step by step, provided with coders allowing to know with precision the distance from the orifices to the rolled product and actuating screw jacks.

When the cooling device 10 is incorporated in a waterproof enclosure 17 as illustrated in FIGS. 5 to 7, flexible bellows watertight 22, 23 are further provided around the axes 20 emerging from the enclosure 17 to be connected to the actuating means and around the supply openings 15 of the boxes 11 which are connected to the means of gas pressure 16.

In operation, a steel strip 1 passes between the cooling 10 arranged in pairs on each side of the steel strip.

Thanks to the high gas exit speed of the blades, close to 150 m / s, made possible by the recovery towards the rear of the device, between the boxes 11, gas after impact on the strip, we can cool effectively a steel strip.

For example, a 1300 mm wide steel sheet was cooled from 650 to 400 ° C, with a gas formed from a mixture of 95% nitrogen and 5% hydrogen, 45 ° C.

The device in this test includes blades 12 pierced with holes of diameter equal to 9.2 mm forming outlet orifices 13 spaced 50 mm apart in-width of the blade 12.

The pitch of the blades 12 or distance L is equal to 50 mm and the distance orifices - strip to be cooled is set to 50 mm.

A central box has blades with a width of 750 mm at level of the orifices, each blade having 15 holes.

The side boxes have blades with a width of 300 mm and having 6 holes.

The depth P of the blades is uniform and equal to 0.35 m, the section S of passage between the blades being equal to 7.3510 ^-3 m ² .

The passage width between the central box and the D _1-2 side boxes is 150 mm.

The gas flow rate per m ² of exchange surface on the sheet to be cooled reaches 250 m ³ / m ² .min. x face.

This gives a gas escape speed between the blades equal to 10.63 m / s, and between the boxes, central and lateral, equal to 14.6 m / s.

This achieves an average transfer coefficient equal to 623 Kcal / m ² .h. ° C with an average cooling rate between 650 and 400 ° C of 120 ° C / s for 1 mm of thickness.

It can therefore be seen that the device according to the invention allows achieve significantly higher flow rates per unit area than in conventional devices, without observing saturation and with higher yields high.

It should be noted that, in the above, the gas flow rates return are considered equal to the gas flow rates injected, whereas, the gas, which heats up on contact with the product to be cooled, expands.

However, the flow rates are high and the heating is weak. so we can overlook the increase in speed due to heating.

The velocities can therefore be calculated by dividing the flow rates in m ³ / s on the return, which are equal to the flow rates injected in m ³ / s, by the section in m ² .

Of course, the invention is not limited to the exemplary embodiment described above, and many modifications can be made to this without departing from the scope of the invention.

Thus, the number of boxes, equal to five, can be different while preferably remaining odd.

Furthermore, the heat exchange device could be a device heating instead of a cooling device.

Claims (15)

1. Device for exchanging heat with a flat product (1), moving in front of the said device (10), comprising means of placing under gaseous pressure (16) at least one plenum chamber (11), the said plenum chamber (11) comprising on a front face several blades (12) forming a duct for the ejection of the gas towards a surface of the flat product (1), the blades (12) being superimposed upon one another in the direction of movement of the flat product (1) and constituting an outlet orifice (13) for the gas extending in the direction of the width of the flat product (1), characterised in that the width of the said plenum chamber (11) in the direction of the width of the flat product (1) is less than the width of the outlet orifice (13) of the gas extending in the width of the flat product (1), the reduced width of the plenum chamber (11) allowing the evacuation of the gas towards the rear on both sides of the said plenum chamber (11).
2. Heat exchange device according to claim 1, characterised in that each blade (12) opens out from the plenum chamber (11) to the gas outlet orifice (13).
3. Heat exchange device according to one of claims 1 or 2, characterised in that it comprises openings (14) for the outlet of the gas after ejection, situated in a plane defined by a rear face opposite the said front face of the plenum chamber (11).
4. Heat exchange device according to one of claims 1 to 3, characterised in that it comprises at least two plenum chambers (11) disposed in the width of the flat product (1), the spacing between the said plenum chambers (11) being such that the evacuation of the gas between the said plenum chambers (11) is carried out at a speed of less than or equal to 20 m/s.
5. Heat exchange device according to claim 4, characterised in that the ratio between half of the gas flow in m³/s at the outlet of two adjacent blades (12) along the width of the product and the section in m² of the space separating the said plenum chambers (11) comprising the said blades (12) is less than 20, the said section extending in a plane parallel with the flat product (1) and in the direction of movement of the flat product (1).
6. Heat exchange device according to claim 5, characterised in that it comprises several plenum chambers (11) disposed parallel with one another in the width of the rolled product (1), the said section of the space separating the plenum chambers (11) being equal to the sum of the sections of the spaces separating the said plenum chambers (11) in pairs.
7. Heat exchange device according to one of claims 4 to 6, characterised in that the blades (12) of the said plenum chambers (11) are distributed regularly over a front face of the plenum chamber (11) in the direction of movement of the flat product, each blade (12) of a first plenum chamber (11) being adjacent to a blade (12) of a second plenum chamber (11) in the plane defined by the gas outlet orifices (13).
8. Heat exchange device according to one of claims 1 to 7, characterised in that the blades (12) of a plenum chamber (11) are dimensioned such that the evacuation of the gas in the section (S) between the said blades (12) is carried out at a speed of less than or equal to 20 m/s at all points.
9. Heat exchange device according to claim 8, characterised in that P(x) ≥ q.x/20.l.w, where P(x) is the depth of the blade at a distance x from an axis of symmetry or from a blade end, w is the mean free height between two blades, q is the flow per blade and I is the width of the end of the blade and where x ≤ l/2 in the case in which the return of the gas is carried out on both sides, and x ≤ I in the case in which the return of the gas is carried out on only one side.
10. Heat exchange device according to one of claims 1 to 9, characterised in that the ratio between the speed of the gas in a plenum chamber (11) and the speed of the gas at the outlet of the blades (12) integral with the said plenum chamber (11) is less than 0.2.
11. Heat exchange device according to one of claims 1 to 10, characterised in that the gaseous pressurising means comprise several fans (16) adapted to supply gas to one or more plenum chambers (11).
12. Heat exchange device according to claim 11, characterised in that it comprises an odd number of plenum chambers (11), the gaseous pressurising means comprise one fan (16) adapted to supply a central chamber (11) and at least one other fan (16) adapted to supply plenum chambers (11) disposed symmetrically on either side of the said central plenum chamber (11).
13. Heat exchange device according to one of claims 1 to 12, characterised in that it is incorporated in a gas-tight enclosure (17), an evacuation orifice (18) being provided in a rear wall (17a) of the enclosure (17), opposite the front face of the said plenum chambers (11).
14. Heat exchange device according to one of claims 1 to 13, characterised in that it comprises adjustment means (19) adapted to displace the said device (10) in a direction perpendicular to the flat product (1).
15. Cooling device for a flat product, such as a rolled steel product, characterised in that it is formed from a heat exchange device according to one of claims 1 to 14.

Images