Evaluating surface heat flux in planar water-jet cooling of moving hot solid by inversely solving steady-state heat conduction

Abstract

In steel-manufacturing industries, water-jet quenching of a moving hot solid is commonly used for run-out table cooling in hot rolling mills. Hence, the evaluation of the surface heat flux in the jet-impact region is necessary for precise temperature control. In this study, we developed an evaluation method for surface heat flux in the impact region by inversely solving the steady-state heat-conduction equation, considering the temperature profile on the reverse side of jet impingement. The main advantage was that the heat-flux distribution could be evaluated with a high spatial resolution. The developed method was validated using the exact solution of the heat-conduction equation. The inverse analysis was highly sensitive to the numerical scheme and small errors in the temperature profile on the reverse side. An appropriate numerical scheme and smoothing operation of the temperature profile allowed the reasonable evaluation of surface heat flux on the cooled surface. In addition, the developed method was applied to laboratory-scale cooling experiments to confirm its applicability. The heat-transfer characteristics of planar jet impinging on a moving solid were studied in the conditions that the temperature of the solid with 0.5 mm thickness was 200–600 °C, and its velocity was 1.5, 3.0, and 4.4 m/s. The heat flux in the jet-impact region depended significantly on these parameters.