Cooling device for blowing gas onto a surface of a traveling strip

Abstract

A gas blower device for blowing gas onto a surface of a traveling strip includes a plenum in the form of a hollow box for containing gas and comprising two side surfaces, a back surface and a front surface opposite to the back surface. The front surface having a profile of convex type symmetry with respect to a mid-plane perpendicular to the plane of the strip, so that a middle ridge of the front surface is located at the smallest distance from the plane of the strip. The front surface further presenting multiple tubular nozzles protruding at the front surface and having a gas outlet orifice facing in use the traveling strip. All the outlet orifices are essentially in a plane parallel to the strip plane. The gas blower device further includes a gas intake tube for feeding the plenum with gas.

Claims

1. A gas blower device for blowing gas onto a surface of a traveling strip, comprising: a plenum in the form of a hollow box for containing gas and comprising two side surfaces, a back surface and a front surface opposite the back surface, the front surface having a convex type profile, symmetric with respect to a mid-plane perpendicular to a plane of the strip, so that a middle ridge of the front surface is located at a smallest distance from the plane of the strip, the front surface further presenting a plurality of tubular nozzles protruding at the front surface and having a gas outlet orifice facing the traveling strip, all the outlet orifices being essentially in a plane parallel to the strip plane; a gas intake tube for feeding the plenum with gas; wherein all the tubular nozzles have the same length, the length being defined as a distance between the gas intake tube and the gas outlet orifice of each one of the plurality of tubular nozzles, so that a root or an inlet of each one of the plurality of tubular nozzles is located inside the plenum, each of the plurality of tubular nozzles passing without connection through an orifice inside the front surface, and having the root directly connected at a right angle to an internal connection plate within the plenum.

2. The device according to claim 1, wherein the profile of convex type is a dihedral profile or a profile with lateral rounded flanks.

3. The device according to claim 1, wherein the middle ridge of the front surface is parallel or tilted with respect to the traveling direction of the strip.

4. The device according to claim 2, wherein a slope of each face of the dihedral profile of the front surface has an angle tending asymptotically to 0° and 30° with respect to the plane of the strip.

5. The device according to claim 2, wherein a minimal slope of each face of the dihedral profile of the front surface is 5 millimeters per meter (mm/meter).

6. The device according to claim 1, wherein the nozzles protruding from the front surface have their longitudinal axes inclined towards an exterior of the device.

7. The device according to claim 2, wherein the nozzles have their longitudinal axes parallel among themselves on a same side of the dihedral profile.

8. The device according to claim 7, wherein the nozzles have their longitudinal axes perpendicular to a same side of the dihedral profile.

9. The device according to claim 7, wherein the nozzles have their longitudinal axes inclined about the normal of a same side of the dihedral profile.

10. The device according to claim 1, wherein the spacing between adjacent nozzles is between 50 millimeters (mm) and 200 mm.

11. The device according to claim 1, wherein the diameter of the nozzles is between 10 millimeters (mm) and 25 mm.

12. The device according to claim 1, wherein the length of the nozzles is between 150 millimeters (mm) and 600 mm.

13. The device according to claim 1, wherein a spacing between intersections of adjacent nozzles with the plenum is variable, in order to have a constant pitch of gas impingement points on the strip.

14. The device according to claim 1, wherein the nozzles are tubular and that the inlet orifices of the nozzles present a free end with a conically flaring bore.

15. The device according to claim 1, wherein the longitudinal axes of the nozzles are orthogonal relative to the convex front surface.

16. The device according to claim 1, wherein the longitudinal axes of the nozzles are orthogonal relative to the plane of the traveling strip.

17. The device according to claim 1, wherein the plenum is divided along its width into different sections, using separating plates, in order to allow adjustment of a gas flow rate in each of the sections.

18. A cooling installation comprising two gas blower devices according to claim 1, such that when in use, the strip travels between two plenums of two gas blower devices which blow simultaneously against both faces of the traveling strip.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Subject matter of the present disclosure will be described in even greater detail below based on the exemplary figures. All features described and/or illustrated herein can be used alone or combined in different combinations. The features and advantages of various embodiments will become apparent by reading the following detailed description with reference to the attached drawings, which illustrate the following:

(2) FIG. 1 schematically represents a common gas blowing device of prior art (such as BLOWSTAB® 2); and

(3) FIGS. 2 and 3 schematically represent particular embodiments for a cooling device intended to blow gas on a traveling strip according to the present invention.

DETAILED DESCRIPTION

(4) In some embodiments, the present invention provides a gas blower device that does not present the drawbacks of the above-mentioned prior art systems, and that optimizes both the thermal and air-flow aspects of blowing, while minimizing the vibration of the strip during traveling.

(5) In some embodiments, the present invention provides a gas blower device suitable to annealing lines in the case of manufacturing of recent very high strength steels, requiring very high cooling rates.

(6) In some embodiments, the present invention obtains an improved temperature uniformity of the traveling strip in the passage through the cooling device. In some embodiments, the present invention provides a cooling device allowing to obtain an improved thermal gradient along the width of the strip, while keeping a good disposal of the blown gas to minimize the vibrations of the strip in order to obtain a better finished product and a limited electrical consumption.

(7) The present invention firstly relates to a gas blower device for blowing gas onto a surface of a traveling strip, comprising:

(8) a plenum in the form of a hollow box for containing gas and comprising two side surfaces, a back surface and a front surface opposite to the back surface, the front surface having a profile of convex type, symmetric with respect to a mid-plane perpendicular to the plane of the strip, so that a middle ridge of said front surface is located at the smallest distance from the plane of the strip, the front surface further presenting a plurality of tubular nozzles protruding at the front surface and having a gas outlet orifice facing in use the traveling strip, all the outlet orifices being preferably in a plane parallel to the strip plane;

(9) a gas intake tube for feeding the plenum with gas;

(10) characterised in that all the tubular nozzles have the same length, said length being defined as the length between the gas inlet and the gas outlet of a nozzle, so that the root or the inlet of the tubular nozzles is inevitably located inside the plenum.

(11) According to preferred embodiments of the invention, the device further includes one of the following features or by a suitable combination thereof:

(12) the profile of convex type is a dihedral profile or a profile with lateral rounded flank;

(13) the middle ridge of said front surface is parallel or tilted with respect to the traveling direction of the strip;

(14) the slope of each face of the dihedral profile of the front surface has an angle comprised between a value tending asymptotically to 0° and 30° with respect to the plane of the strip, preferably between 5° and 30°, and more preferably between 5° and 15°;

(15) a minimal slope of each face of the dihedral profile of the front surface is 5 mm/meter;

(16) the nozzles pass without connection through an orifice inside the front surface and have a root connected to an internal connection plate within the plenum;

(17) the nozzles protruding at the front surface have their longitudinal axes inclined towards the exterior of the device;

(18) the nozzles have their longitudinal axes parallel among themselves on a same side of the dihedral profile;

(19) the nozzles have their longitudinal axes perpendicular to a same side of the dihedral profile;

(20) the nozzles have their longitudinal axes inclined about the normal of a same side of the dihedral profile;

(21) the spacing between adjacent nozzles is comprised between 50 mm and 200 mm, preferably between 50 mm and 140 mm;

(22) the diameter of the nozzles is comprised between 10 mm and 25 mm, preferably between 10 mm and 16 mm;

(23) the length of the nozzles is comprised between 150 mm and 600 mm, preferably between 250 mm and 450 mm, according to the width of the plenum;

(24) the spacing between the intersections of adjacent nozzles with the plenum is variable, in order to have a constant pitch of the gas impingement points on the strip;

(25) the nozzles are tubular and the inlet orifices of said nozzles present a free end with a conically flaring bore;

(26) the longitudinal axes of the nozzles are orthogonal relative to the convex front surface;

(27) the longitudinal axes of the nozzles are orthogonal relative to the plane of the traveling strip;

(28) the plenum is divided along its width into different sections, using separating plates, in order to allow adjustment of the gas flow rate in each of said sections;

(29) the plenum comprises reinforcement or stiffening parts to limit variation of the plenum geometry due to internal pressure of the blowing gas.

(30) In some embodiments, the present invention also relates to a cooling installation comprising two gas blower devices as disclosed above, characterised in that, in use, the strip is traveling between the plenums of the two gas blower devices, so that gas is blown simultaneously against both faces of the traveling strip.

(31) In the drawings, the traveling direction of the metal strip is perpendicular to the plane of the figure.

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

(32) After detailed simulations and analyses, the present invention solves the problem of non-uniform strip temperature at the exit of the cooling section of the BLOWSTAB® 2 design was due to the variation in the length of the nozzles. For a defined pressure in the plenum, the mass flow decreases with the tube length. This means that, for a same plenum pressure, the central nozzles have a higher Reynolds number than those located at the edges. Therefore, the cooling efficiency is worse at the edges of the strip than in the centre.

(33) The present invention permits to avoid a non-uniformity of the strip temperature at the exit of the cooling section. To this end, and as illustrated by FIGS. 2 and 3, the cooling device 1 of the present invention comprises a plurality of nozzles 4, provided in a plenum 3 supplied with gas, having the same length, said plenum being designed as in BLOWSTAB® 2.

(34) According to a preferred embodiment, the plenum 3 of the present invention is in the form of a hollow box comprising two side surfaces 31, a back surface 32 and a front surface 33. The back surface 32 is connected to a blowing gas intake tube 5 and the front surface 33, opposite to the back surface 32, is provided with the plurality of nozzles 4.

(35) The front surface 33 is considered as the active surface because it is facing the traveling strip 2. Generally any convex surface will be taken in consideration under the scope of the invention, in order to provide a more uniform transverse speed to the blown gas. Usually this surface 33 can present a simple dihedral profile, said profile being preferably considered according to a transverse direction with respect to the direction of movement of the strip (the profile could also be considered with respect of the direction of movement of the strip). The dihedral profile is symmetric and of convex type so that the middle or median ridge 34 of this surface 33 corresponds to the smallest distance to the plane of the strip 2. This specific geometry allows to reduce the strip vibrations due to an improved disposal of the high flow of gas, as the gas can escape laterally without constraint thanks to the high cross section available. The median (or middle) ridge 34 can be parallel to the traveling direction of the strip. However, according to some embodiments, the median ridge 34 can be tilted by 2-3 degrees about the traveling direction of the stip. This allows to prevent any alignment of the nozzles with the traveling direction.

(36) According to the invention, the plurality of nozzles 4, being provided in the front surface 33, have a same length, as illustrated in FIGS. 2 and 3. In this way, a same tube length is used across the whole width of the plenum which allows a cooling efficiency essentially identical in the middle and at the edges of the strip. This design leads to a uniform strip temperature at the exit of the cooling section because the mass flow is constant and the Reynolds number is identical in all parts of the device, when the gas hits the strip.

(37) Preferably, the distance provided between the outlet orifices of nozzles 4 and the traveling strip 2 has to be identical across the entire width of the strip. That is to say that all the outlet orifices of nozzles 4 can lie in a common plane that is substantially parallel to the plane of the strip 2. It could also not be the case if any compensating effect is to be sought. This is then advantageous for good stabilization while said strip 2 is traveling, and also for temperature uniformity in said strip 2. The equal distances between all the nozzle orifices and the plane of the strip 2 maintain the uniformity of the pressure exerted by the gas blown onto the strip 2. In order to obtain this specific feature, in combination with the dihedral profile of the front surface 33 and in combination with the same length of the nozzles 4, the nozzles 4 may have to pass through the front surface 33, as illustrated by FIGS. 2 and 3. This is not the case in the BLOWSTAB® 2, and in the installations of prior art, where each tubular nozzle is fastened, in particular welded, via its root to the external surface of the plenum.

(38) In some embodiments, at least part of the longitudinal axes of the nozzles 4 are parallel between them, this part corresponding for example to all the nozzles 4 located on a same side of the dihedral profile. Note that the longitudinal axis of the nozzle is the cylinder axis in case of a tubular nozzle. In the embodiment represented in FIG. 2, the longitudinal axes of the nozzles 4 are orthogonal relative to the front surface 33 (and thus to the dihedral profile). In another embodiment, represented in FIG. 3, the longitudinal axes of each nozzle 4 are orthogonal relative to the plane of the traveling strip 2 but not to the sides of the dihedral profile.

(39) In the embodiments of the present invention, the nozzles are preferably not welded to the external surface of the plenum 3. In this case the nozzles are passing through the front surface 33 and are for example fastened to an internal plate 7 at right angle. Avoiding welding to the dihedral profile makes manufacturing easier, because welding tubes with a wall thickness typically of about 2 mm on a sheet of thickness typically of about 4 mm is very complicated.

(40) Preferably, the slope of each face of the dihedral profile of the front surface 33 has an angle comprised between a value possibly tending asymptotically to 0° and 30° to the plane of the strip 2, preferably between 5° and 30°, and more preferably between 5° and 15°.

(41) Advantageously, two plenums 3 are provided in a cooling installation, between which the strip 2 can travel, so that gas can be blown simultaneously against both faces of the traveling strip 2. Preferably, the two plenums 3 have their respective front surfaces 33 in a convex dihedral shape and are symmetric about the plane of the strip 2.

(42) According to one embodiment, the spacing or pitch between adjacent nozzles 4 can vary between 50 mm and 200 mm, preferably between 50 mm and 140 mm. However, the spacing between the intersections of adjacent nozzles 4 within the plenum 4 can be variable, in order to guarantee a uniform pitch of the gas impingement points on the strip.

(43) It is also advantageous to provide nozzles 4 which are tubular. Preferably, the nozzle diameter is comprised between 10 mm and 25 mm, and more preferably between 10 mm and 16 mm. Preferably, the tube length of the tubular nozzles is comprised between 50 mm and 600 mm, more preferably between 250 mm and 450 mm, according to the width of the plenum. A range of length values is required to compensate for the tilted shape of the plenum.

(44) Preferably, the inlet orifice of each tubular nozzle 4 presents a free end with a conically flaring bore. These features provide substantial advantages given the reduction of head loss.

(45) The width of the plenum 3 can also be divided into different sections, using separating plates 6 (see FIG. 2). The flow rate in each of the sections can then be adjusted either by a separate fan or by registers in the case of a single fan supply. The separating plates 6 are also advantageous in order to stiffen the structure.

(46) The plenum 3 can also comprises an internal plate 7 as illustrated by FIG. 2, able to maintain and rigidify the two faces of the dihedral profile (front face 33), in addition to a role of attaching the nozzles (see above).

(47) FIG. 3 is an example of design which allows to reach a heat transfer coefficient of 650 W/m.sup.2/° K, when using a gas comprising 15% H.sub.2 and a nozzle to strip distance of 60 mm. The outside tube length is 100 mm in the centre of the front surface 33 and 350 mm on the edges of the front surface 33 while all the tube lengths are equal.

(48) While subject matter of the present disclosure has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive. Any statement made herein characterizing the invention is also to be considered illustrative or exemplary and not restrictive as the invention is defined by the claims. It will be understood that changes and modifications may be made, by those of ordinary skill in the art, within the scope of the following claims, which may include any combination of features from different embodiments described above.

(49) The terms used in the claims should be construed to have the broadest reasonable interpretation consistent with the foregoing description. For example, the use of the article “a” or “the” in introducing an element should not be interpreted as being exclusive of a plurality of elements. Likewise, the recitation of “or” should be interpreted as being inclusive, such that the recitation of “A or B” is not exclusive of “A and B,” unless it is clear from the context or the foregoing description that only one of A and B is intended. Further, the recitation of “at least one of A, B and C” should be interpreted as one or more of a group of elements consisting of A, B and C, and should not be interpreted as requiring at least one of each of the listed elements A, B and C, regardless of whether A, B and C are related as categories or otherwise. Moreover, the recitation of “A, B and/or C” or “at least one of A, B or C” should be interpreted as including any singular entity from the listed elements, e.g., A, any subset from the listed elements, e.g., A and B, or the entire list of elements A, B and C.

REFERENCE SYMBOLS

(50) 1 Cooling device (gas blowing device) 2 Strip 3 Plenum (or cooling header, hollow box) 31 Side surface of the plenum 32 Back surface of the plenum 33 Front surface of the plenum 34 Middle ridge of the front surface 4 Nozzle 5 Blowing gas intake tube 6 Separating plate 7 Internal connection plate