Prediction and control of flow properties and cooling process for a hot strip on a runout table by water film

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For a hot rolling process of sheet steel, the finishing temperature of a hot strip is controlled to be kept beyong the A_3 critical point at the exit of the last finisher. Then, the hot strip passing through the last finisher is cooled on a runout table from the autenitic finishing temperatures in the range between 820ﾟC and 900ﾟ to the coiling temperatures between 500ﾟ and 700ﾟ according to the final strip thickness and steel grade. The investigation performed here is concerned with a predictable model for the temperature change of hot steel plates cooled by a laminar water flow. The results defined here are summarized as follows :First, it is indispensable to build up a predictable and reproducible numerical model for the flow field of the water film formed by the laminar water flow impinging on a horizonatal plate surface. In ordet to do so, first, the cold model which neglects the thermal effect has been adopted. The numerical model has been constructed using a system of the Navier … More Stokes equations governing the flow field of the water film on a plate surface. It has been confirmed that the flow field obtained by the model gives close agreement with experimental data.Next, the temperature rise of water film has been taken into account. When the temperature of the cooling water is kept low, the initially hot red plate begins to darken in the neighborhood of the water impinging point, as soon as the water impinges on the plate. As the cooling time elapses, the circular black zone expands. The visually observed fact is a positive proof of the occurence of the wetting phenomena. The numerical model has been made so that the effective forced water cooling zone can be determined by accounting for temperature change of the water film spreading on the hot plate. As the result of comparison of the numerical results obtained by the model with the experimental ones, a fairly good agreement has been found between the two, especially near the Leidenfrost temperature.Also, the predictable model for the estimation of the temperature change of a hot steel plate cooled by a laminar water curtain, which is horizontally moving at a certain velocity. Then, it has been confirmed that the numerical model proposed here is valid to the prediction of the cooling process of hot plate cooled by a laminar water curtain.In conclusion, we believe that the beforemensioned desired purpose of this research has been fulfillled for the most part. However, we think that are a number of problems which remains unsolved and will continue to promote the present investigation more deeply. Less