JPH06238320A - Spray cooling method - Google Patents

Abstract

PURPOSE:To magnify a heat transfer coefficient to improve cooling capacity and to uniformly cool the whole body of a cooling surface by managing collision force of cooling water, water film pattern, water film breadth in cooling a high temperature steel plate, a wide flange shape steel, etc. CONSTITUTION:The collision pressure of cooling water to a cooled surface is set to an area of 0.05-0.5g/mm<2>, the dispersion of collision force of cooling water does not exceed + or -20% of the set value, the water film pattern of the cooling water is rectangular or square or elliptical, the breadth of a spray water film is cooled at >=20mm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spray cooling method using water or a mixture of steam and water as a cooling medium. Such cooling can be used in all fields such as roll cooling, steel plate cooling, and H-section steel cooling.

[0002]

2. Description of the Related Art In the conventional design, planning and control of a cooling method using a spray nozzle that uses water as a cooling medium, the distribution of the cooling water amount is important, and the cooling control is based on the adjustment of the cooling water amount. . That is, conventionally, the cooling efficiency of the cooling nozzle has not been discussed so far, and an attempt has been made exclusively for uniform cooling by combining nozzles, controlling the amount of water, and the like. In such a conventional technique, for example, it was difficult to uniformly cool the entire surface of the H-shaped steel flange or the like.

[0003]

Conventionally, in cooling using a spray nozzle, a cooling nozzle has been made so that when cooling water sprayed from the nozzle collides with a surface to be cooled, a uniform cooling water distribution is obtained. Even if the hot steel sheet is cooled using such a cooling nozzle having a uniform cooling water distribution, uniform cooling cannot be obtained.

As a result of investigating and studying factors other than the cooling water amount that contribute to cooling, the present inventors have found that the collision pressure of the cooling water on the cooling surface and the water film pattern are important factors that determine the cooling capacity together with the cooling water amount. It turned out to be. An object of the present invention is to provide a spray cooling method based on such new knowledge.

[0005]

SUMMARY OF THE INVENTION The present invention is a high temperature steel plate,
When spray-cooling the flat surface such as the flange of H-section steel or the roll surface, (a) check the collision pressure of the cooling water on the cooling surface.
Set within the range of 0.05 to 0.5 g / mm ² , and (b) make the variation of the collision pressure of the cooling water within ± 20% of the set value,
(C) The water film pattern of the cooling water has a rectangular shape, a square shape, or an oval shape, and (d) the spray water film has a lateral width of 20 mm or more at the portion that collides with the surface to be cooled of the cooling water for cooling. It is a spray cooling method.

[0006]

The present inventors will explain the results of research and development experiments conducted by investigating and investigating factors contributing to cooling in spray cooling with reference to the drawings. (1) Effective water density When investigating the case of cooling a moving object,
As shown in FIG. 1, it has been found that the cooling efficiency is significantly changed by changing the nozzle pitch and the cooling water lateral width (cooling width in the traveling direction). That is, in the case of spray cooling, not only the cooling water amount needs to be increased, but the amount of water effectively involved in cooling, that is, the effective water amount density contributes to the cooling effect. FIG. 1 shows the relationship between the water amount density of all jetted water and the effective water amount density involved in effective cooling.
Curves 1, 2 and 3 each have a nozzle pitch of 100 m.
m, 200 mm, 400 mm, and the material (cooling target) passing speed is 2.0 m / sec. Curve 1
And the curve 2, the total water density is about 2 × 10
^There is a significant difference in the effective water density with respect to ³ liters / m ² · min. Total water density of curves 2 and 3 about 1 x 10
^The same applies to ³ liters / m ² · min.

That is, since the effective water amount density increases when the nozzle pitch is made dense, in the spray cooling of the present invention, it was aimed to increase the lateral width of the cooling water for a single nozzle. (2) Horizontal width b of spray water film and height h in the flange width direction As described above, in order to obtain high cooling efficiency, it is important to increase the lateral width of the cooling water film within a range where the collision pressure of the cooling water does not decrease. is there. The test was conducted under the conditions shown in Table 1, and the results are shown in FIG. When the water film width of the spray is thin, the effective water amount density We hardly changes even if the jet water amount density Wn increases, and the water film width of the spray is 10 mm and 15
There is no significant change in mm, but it significantly increases at 25 mm. Therefore, it is recommended to set it to 20 mm or more.

The inventors of the present invention also conducted an experiment using a nozzle in which the pattern of the spray water film was a square of 50 mm on each side, and it was found that high cooling efficiency can be obtained even in this case. .

[0009]

[Table 1]

That is, since the pattern of the spray water film sprayed from the nozzle is conventionally circular or elliptical as shown in FIG. 7 (a) or (b), respectively, the effective water amount density of the surface to be cooled is reduced. Was low. Therefore, in the present invention, in order to increase the effective water amount density of the surface to be cooled, as shown in (c), (d) and (e) of FIG. Alternatively, an oval shape (a rectangular corner having a rounded shape) is used to minimize deviation in the water film pattern.

When spraying on the surface to be cooled by using the nozzle for forming the water film pattern of the present invention shown in FIGS. 7C, 7D and 7E, FIGS. As shown in (b) and (c), single nozzles forming a square, rectangular or oval water film pattern are arranged at a predetermined nozzle pitch in the longitudinal direction of the surface to be cooled, or (d) in FIG. ), (E), and (f), a plurality of nozzles that form a square or oval water film pattern are combined vertically and uniformly arranged in the longitudinal direction of the surface to be cooled at a predetermined nozzle pitch. It is also possible to spray cool.

(3) Collision pressure of cooling water 0.05 g / mm ²
Regarding the above, the collision pressure of the cooling water on the cooling surface is an important factor that determines the cooling capacity together with the amount of cooling water. FIG. 2 shows conventional nozzles A and B having a spray water film width (b) of 25 mm.
And the results of confirming that the collision pressure affects the heat transfer coefficient using the new nozzle C having the spray water film width (b) of 50 mm, respectively.

That is, although the nozzle A and the nozzle B have been conventionally used, the result of detailed investigation of the nozzle characteristics, paying attention to the fact that the nozzle is not cooled uniformly only by the conventional water amount adjustment Is the graph shown in FIG.
In FIG. 2, when the collision pressure between the conventional nozzle A and the conventional nozzle B is approximately 0.25 (g / mm ² ), one nozzle B
Although the amount of water is 4 (l / min), the other nozzle A has a water amount of 6 (l / min) and the heat transfer coefficient α of each is 600 (kcal / m ^2). h ° C).

Conventionally, when such a phenomenon of the nozzles A and B occurs in the spray, the nozzles are unevenly cooled, and it is difficult to adjust the cooling capacity for adjusting the amount of water. However, if the conditions for obtaining a high heat transfer coefficient α with a small amount of water are summarized, by analogy with making the nozzle pitch dense and making the spray width thick (wide), the cooling water is evenly distributed and the collision pressure is also reduced. The new nozzle C used in the present invention was prototyped on the assumption that the effective water amount density can be increased if the collision pressure can be made uniform and a certain level or more can be maintained.

In FIG. 2 described above, the collision pressure (g / mm ² ) of the cooling water on the cooling surface and the water amount W (l / min) of the cooling water are used.
And the heat transfer coefficient α (kcal / m ² h ° C.) are shown. According to the new nozzle C of the present invention, the amount W of cooling water is at least new compared to the conventional nozzles A and B. Increasing the spray water film width of the nozzle C includes the effect and has an extremely high heat transfer coefficient α
(kcal / m ² h ℃) is obtained.

With the new nozzle C, the collision pressure of the cooling water is 0.03 g.
Comparing the heat transfer coefficient α at the collision pressure between / mm ² and 0.05 g / mm ² , it was significantly improved from 600 kcal / m ² h ℃ to 900 kcal / m ² h ℃. And the collision pressure is from 0.05g / mm ²
The heat transfer coefficient α is 900 kcal / m as it increases to 0.2 g / mm ^{2.
From 2} h ℃ to 1100 kcal / m ² h ℃ gradually increases from 0.2 g / mm ² or more, and when the collision pressure exceeds 0.5 g / mm ² , the heat transfer coefficient α becomes saturated and the collision pressure increases further. However, the effect is small. Therefore, in the present invention, the collision pressure of the cooling water on the cooling surface is set to 0.
It is set in the range of 05 to 0.5 g / mm ² .

(4) Equalization of the collision force of the cooling water on the cooling water collision surface. While moving an H-shaped rope having a flange width of 200 mm in the longitudinal direction at a speed of 1.0 m / s, the central portion thereof was cooled by a spray nozzle having a cooling width of 100 mm. In FIG. 3, the vertical axis shows the flange width and the horizontal axis shows the heat transfer coefficient distribution at each width position. In FIG. 3, the circle marks show the heat transfer coefficient distribution in the flange width direction by the conventional nozzles A and B, and the X mark show the heat transfer coefficient distribution in the flange width direction by the new nozzle C used in the present invention.
It can be seen that the conventional nozzles A and B have a large variation in the heat transfer coefficient in the direct cooling range, whereas the new nozzle C used in the present invention cools with a uniform heat transfer coefficient with little variation. .

FIG. 4 shows the distribution of the collision pressure when the new nozzle C of the present invention is used to inject cooling water having a substantially constant amount of cooling water onto a cooling surface having a pressure receiving area of 6 mm × 50 mm. The water pressure at that time is 2.0, 1.5, 1.0, and 0.5 kg, respectively.
There are 4 types of / cm ² . The distribution of collision pressure in Fig. 4 is 0.05g / mm ²
Within the above range. As indicated by the mark X in FIG. 3, the heat transfer coefficient α (kcal / m ² h ° C.) in the direct cooling range according to the present invention shows an excellent value. However, as indicated by a circle in FIG. 3, in the water film sprayed from the conventional nozzle, the heat transfer coefficient varies depending on the position in the width direction on the collision surface, and there is a difference between the central part and the end part of the water film width. Therefore, in order to keep the heat transfer coefficient almost constant, it is empirically desirable to keep the variation of the collision pressure within the set value ± 20%.

[0019]

EXAMPLE A H-shaped rope as shown in FIG. 6 was cooled by the method of the present invention. Flange widths of 150mm and 200mm respectively
, 250 mm and 300 mm H-shaped flanges were water-cooled with the nozzle pattern shown in FIG. Since only the flange of the H-shaped rope is cooled, it is necessary to prevent the cooling water from splashing to the web side. The spray direction of the nozzle is the oblique type shown in Fig. 6, and the cooling water collision pressure is 0.2 (g / g / mm ² ), the spray water film width b is 20 mm and 40 mm, respectively, and the nozzle pitch p
Was 200 mm and 100 mm, and the total water consumption Q was the same.
The height of the spray water film at that time was defined as h. The results are shown in Table 2. In the example, cooling efficiency (effective water amount density)
Was doubled, and uniform cooling was possible.

[0020]

[Table 2]

[0021]

According to the present invention, in cooling using a spray nozzle, the shape, arrangement, operating conditions, etc. of the nozzle are defined by a novel factor that has not been studied in the past.
Cooling with high cooling efficiency can be realized.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between total water density and effective water density.

FIG. 2 is a graph showing the relationship between collision pressure and heat transfer coefficient.

FIG. 3 is a graph showing a heat transfer coefficient distribution on a cooling surface.

FIG. 4 is a chart showing a collision pressure distribution.

FIG. 5 is a graph showing the relationship between spray water pressure and each water amount density.

FIG. 6 is an explanatory view of cooling the spray nozzle of the H-shaped rope of the embodiment.

FIG. 7 is a plan view showing a spray water film pattern from a nozzle.

FIG. 8 is an explanatory diagram showing a pattern combination state in the case where a surface to be cooled is cooled by a water film sprayed from a nozzle.

[Explanation of symbols]

 α Heat transfer coefficient W Water quantity b Water film width h Water film height We Effective water quantity density Wn Injection water quantity density

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Tsuneo Seto Tsuneo Seto 1-chome, Mizushima Kawasaki-dori, Kurashiki-shi, Okayama Prefecture (No address) Inside the Mizushima Works, Kawasaki Steel Co., Ltd. (72) Yoji Fujimoto 1-shima-shima Kawasaki, Kurashiki-shi, Okayama Chome (No house number) Kawasaki Steel Co., Ltd. Mizushima Steel Works

Claims (1)

[Claims] 1. In spray cooling using water or a water-water mixture as a cooling medium, the collision pressure of the cooling water on the cooling surface is set to 0.05 to 0.5 g / mm ² , and the collision pressure of the cooling water is set. Variation is within ± 20% of the set value, the water film pattern of the cooling water is rectangular, square or oval, and the horizontal width of the spray water film is 20 mm or more at the part where the cooling water collides with the cooled object. A spray cooling method characterized by: