Turbulent heat transfer in liquid iron during electron beam evaporation

Electron beam evaporation of high-purity liquid metals is characterized by vigorous (turbulent) convection in the melt pool resulting in unwelcome hea t losses. This convective motion is exclusively driven by thermocapillary f orces. We exploit this unique feature to measure the Nusselt number in liqu id iron for Marangoni numbers up to 10(8). The experiments are carried out in a real-to-life test facility for electron beam evaporation. We compare t he results of our investigations with findings of a recent scaling analysis . Moreover. we perform direct numerical simulations employing a 2D model. T he numerical results demonstrate the turbulent character of the flow as wel l as the dominance of thermocapillarity over buoyancy. (C) 2000 Elsevier Sc ience Ltd. All rights reserved.