Practical application of inverse heat conduction for wall condition estimation on a rotating cylinder

International audienceThe solution of the linear, inverse, transient heat conduction problem (IHCP) in a cylindrical geometry is analysed. The rotating cylinder under investigation is experiencing boiling convection induced by the impingement of a water jet. The initial temperature is known, additional temperature measurements in time are taken with sensors positioned at a constant radius within the solid material, and the estimation of the wall heat flux at the external radius is sought. First, simulated temperature measurements inside the cylinder are processed in order to be used to estimate the wall heat flux. When noise is present in the data, some of the simulated results obtained using the least squares method exhibit oscillatory behavior, but these large oscillations are substantially reduced by the implementation of a regularization technique. Real experimental data are also used for the wall condition estimation and for the subsequent building of local boiling curves are plotted and discussed. The question of the possible effect of a temperature dependent conductivity on the reconstructed wall condition is also considered

Heat transfer from a hot moving cylinder impinged by a planar subcooled water jet

International audienceA hot moving (rotating) cylinder was heated up to 500-600°C and then was cooled by a planar water jet impinging on a line parallel to the symmetry axis. The time dependent wall temperature was measured using embedded thermocouples and the corresponding wall heat fluxes were estimated through an inverse conduction method. In a recent paper, we showed that cooling rates depend on the subcooled temperature of the jet, the velocity of the jet and the surface-to-jet velocity ratio. Since the initial temperature of the cylinder was higher than the Leidenfrost temperature, we observed all the boiling regimes from film boiling to nucleate boiling. The objectives of this paper are firstly to describe the current conditions which exist in the Run Out Table in hot rolling mills, secondly to review the main experimental studies dedicated to jet cooling which have led to modelling heat transfer in boiling conditions and finally to propose new correlations taking into account the velocity of the wall