移動平板へ衝突する円形水噴流の熱伝達特性の評価手法の構築

Abstract

In metal hot-rolling processes, water jet cooling of a moving hot solid is commonly used for run-out table (ROT) cooling. High-accuracy evaluation of the surface heat flux at jet-impinging areas is important for accurate temperature control to produce high-quality steel plates. Most previous studies on the heat transfer characteristics of jet impingement areas have considered water jet impingement on stationary hot solids; however, the flow conditions are different in ROT cooling because the water jet impinges on moving hot solids. Thus, the estimation of the heat flux at the jet impact zone of a water jet on a moving hot solid is essential. Therefore, we developed a method for evaluating the surface heat flux in the impinging areas of water jet cooling of a moving hot solid. The method was based on the inverse solution of the heat conduction equation, using the measured temperature profile as a boundary condition, such that the heat removal in the jet impinging area was obtained numerically. To demonstrate the validity of our model, we performed cooling experiments on a circular water jet impinging obliquely on a moving hot solid. The experiments were conducted under the following conditions: temperature of the solid made of stainless steel was 300-550 °C, moving velocity of the solid was 0.5-1.0 m/s, jet diameter was approximately 0.31 mm, and water flow rate was 10 ml/min. We confirmed that the model was useful for evaluating the heat flux in the jet impact region.