Abstract
The invention refers to a distributor tube (400) for cooling metal or similar products, in particular steel strips, comprising along the longitudinal extension of said distributor tube (400), a plurality of outlet openings (406) through which a cooling fluid can be ejected; an inlet (402) and a closure (404) of said tube at its ends; a connection for connecting a source of cooling fluid and feeding said distributor tube (400) with said fluid. At least on the inlet side (402) there is a zone of change in the diameter of the tube, which varies from a sector with a smaller diameter, followed in the direction of flow by a sector with a larger diameter. Upstream of said plurality of outlet openings (406) there is an orifice (414) in the area of the flow section. Further described are a corresponding hot-rolling plant and a use of the distributor tube.
Claims
1. A distributor tube for cooling metal, leaving a hot-rolling mill comprising: a) along a longitudinal extension of said distributor tube, a plurality of outlet openings through which a cooling fluid can be ejected; (b) an inlet (402) located at one end of said distributor tube for said cooling fluid and a closure (404) of said distributor tube at the other end, (c) a connection for connecting a source of cooling fluid and feeding said distributor tube with said fluid; wherein at least on the inlet side of said distributor tube there is a zone of change in the diameter of the tube, which varies from a sector with a smaller diameter, followed in the direction of flow by a sector with a larger diameter, wherein upstream of said plurality of outlet openings there is an orifice in the area of the flow section.
2. The distributor tube according to claim 1, wherein said orifice is a plate.
3. The distributor tube according to claim 13, wherein said holes have a diameter in a range of 5 to 10 mm.
4. The distributor tube according to claim 3, wherein said holes are arranged in a triangular pitch.
5. The distributor tube according to claim 4, wherein the pitch between adjacent holes is between 7.5 and 15 mm.
6. The distributor tube according to claim 1, wherein the free surface or the sum of the surfaces of the individual holes of passage of the cooling fluid, compared to the internal surface of the distributor tube in the area of larger diameter, is in the range from 30 to 40%.
7. The distributor tube according to claim 1, wherein said openings are arranged on a straight line.
8. The distributor tube according to claim 1, wherein said orifice is located in said sector with larger diameter.
9. The distributor tube according claim 1, wherein the number of openings is in a range of from 22 and 32 for a tube length in a range of from 1.5 to 2 m.
10. The distributor tube according to claim 1, wherein the orifice is located at a distance of at least 10 cm from the nearest outlet opening.
11. A hot-rolling plant comprising in the cooling zone a roller conveyor for the transport of the products to be cooled wherein at least one distributor tube according to anyone of the preceding claims is placed between the rollers.
12. A method of using a distributor tube according claim 1 or a plant according to claim 11 for cooling strips having a width/thickness ratio ranging from 2000 to 75.
13. The distributor tube of claim 2, wherien the plate is circular and comprises a plurality of holes.
14. The distributor tube of claim 1, wherien the metal comprises a steel strip.
Description
DESCRIPTION OF A PREFERRED EMBODIMENT
[0024] FIG. 1 illustrates in parts a), b) and c) state-of-the-art distributor tubes and in part d) a distributor tube according to the invention.
[0025] FIG. 2 illustrates in two diagrams a comparison of the flow distribution for the various types of distributor tubes depicted in FIG. 1.
[0026] FIG. 3 illustrates a comparison of the flow distributions in the different types of distributor tubes of FIG. 1.
[0027] FIG. 4 illustrates a comparison of the static pressure distributions in the different types of distributor tubes of FIG. 1.
[0028] In FIGS. 3 and 4 the tubes indicated with a), b), c) and d) correspond to the relative tubes as defined with the relative letters a), b), c) and d) in FIG. 1.
[0029] FIG. 1 illustrates in parts a), b) and c) state-of-the-art distributor tubes 100, 200, 300 and in part d) a distributor tube 400 according to the invention. Each tube represented has an inlet 102, 202, 302, 402 and a closure 104, 204, 304, 404, respectively. Along the longitudinal extension of each distributor tube 100, 200, 300, 400 a plurality of nozzles 106, 206, 306, 406 are provided along a straight line. Different solutions are provided in the zones between the transition from a smaller diameter to a larger diameter on the inlet side of the tube. The state of the art provides for an acute edge 108, a gradual enlargement 210 or the creation of a double tube 312 which extends for the entire main manifold, whereby the fluid first travels through the inner tube 312, then rises inwards along the space between the outer tube 300 and the inner tube 312 and exits the nozzles 306. The solution according to the invention, on the other hand, provides for the insertion of an orifice 414 in the distribution tube in the zone with a larger diameter.
[0030] FIG. 2 illustrates in two diagrams a comparison of the flow distribution for the various types of distributor tubes depicted in FIG. 1. The x axis represents the number of nozzles along the distributor tube, the y axis the volumetric flow rate on the nozzle concerned in % with respect to the average volumetric flow rate (100% represents the total manifold flow rate divided by the total number of nozzles). The curves a, b and c of FIG. 2 a) indicate for a first type of manifold respectively the trend of the total flow rates along the tube for the state-of-the-art variants a) to c), while the curve d concerns the relative trend of the volumetric flow rates for the orifice solution according to the invention. The flow rates of the figure were attenuated by the least squares method. The profiles for the gradual enlargement and orifice tube are similar with a slight advantage of the tube according to the invention and offer a better volumetric flow rate distribution than the acute-edge tube and the double tube. In FIG. 2 b) there is a relative comparison between a double tube (curve c) and a distributor tube according to the invention (curve d) for another type of manifold, the orifice solution is similar and slightly better than the double tube. The double tube is more uniform for the first nozzles and the orifice tube for the last nozzles. In this case, the benefits with respect to the pressure drop are not so important, but the simpler design and better flow rate distribution make the orifice solution preferable. The different profile for the manifold of type c shown in FIG. 2 a) and 2 b) results from different end-of-line conditions. In the case of FIG. 2 a), the speed in the smaller tube is lower, resulting in a flow stop and return before reaching the blind end of the larger tube. In the case of FIG. 2 b), the speed in the smaller tube is higher, converging in a flow which hits the blind end of the wide tube. It can be assumed that the higher the speed in the smaller tube, the worse the flow distribution near the end of the closed tube and vice versa, the lower the speed the better the total distribution in the manifold (especially near the end of the closed tube). There is a pressure unevenness in the nozzles for the acute-edge tube, while in the other tubes it is quite uniform.
[0031] FIG. 3 illustrates a comparison of the flow distributions in the different types of distributor tubes of FIG. 1 for a geometry corresponding to that of FIG. 2 a). The flow distribution in the tube according to the invention is similar to that of the acute-edge tube and with gradual enlargement, while that of the double tube is different, forcing most of the cooling liquid to pass linearly through the inner tube. The flow speeds change with the grayscale: in particular, the high speeds are the lightest. In the case of acute-edge and gradual enlargement tubes, the speed decreases from the first to the last nozzle, while in the double tube it is lower in the space between the tubes than in the inner tube, but relatively uniform along the length of the inner tube. In the case of the acute edge, the recirculation zones near the edge are created, resulting in a very unfavourable flow distribution in the zone of the first nozzles. In the orifice tube, the speed is fairly uniform throughout the tube.
[0032] FIG. 4 illustrates a comparison between the static pressure distributions in the different types of distributor tubes of FIG. 1 with the same geometry which was the basis of the results of FIG. 2 a). The darker colours correspond to higher pressures. In the case of the acute-edge tube, the pressure inside the tube increases after the first nozzles to remain fairly constant for the remaining nozzles. In the case of the gradual enlargement tube, the pressure is lower with respect to the tube described above and falls in a manner divided by zones from the beginning to the end of the tube. In the case of the double tube, the pressure decreases slightly inside the inner tube and is lower, but uniform, in the zone between inner and outer tube. Finally, in the orifice tube, the pressure drops considerably immediately after the orifice to stabilize at a stable value after the first nozzles.
[0033] Compared to a gradual enlargement tube, an important advantage of the orifice tube is that the proposed solution is relatively independent of the input speed of the main distributor. With high input speeds, the gradual enlargement tube may lead to an unfavourable distribution, especially in the initial zone of the main distributor. The advantages of the orifice tube over a double tube also result from a comparison of the calculated inlet pressures and pressure losses, as shown in table 1 below.
TABLE-US-00001 solution relative pressure loss, % With reference to FIG. 2 a) gradual enlargement tube 100* acute-edge tube 104 double tube 144 orifice tube 142 With reference to FIG. 2 b) double tube 100* orifice tube 96 *Reference value.
[0034] The economical comparison of the double and orifice tube solutions favours the orifice tube. For manifolds with reference to FIG. 2 b), the use of the orifice results in estimated savings (compared to a double tube) of more than 2,000 kg of ASTM A312 TP304 steel. Assuming an indicative price of these tubes of €5/kg, the use of orifices would result in material savings of more than €10,000.00.
[0035] The invention has achieved the object of proposing a distributor tube with a uniform flow distribution, a simpler design, economic benefits and a sufficient but not excessive pressure drop.
[0036] During implementation, further embodiment modifications or variants of the distributor tube, hot-rolling plant and cooling process, object of the invention, not described herein, may be implemented. If such modifications or such variants should fall within the scope of the following claims, they should all be considered protected by the present patent.
