LAUSR

Abstract An experimental investigation was performed to determine the local value of heat transfer coefficient with a free-surface axisymmetric downward jet of lubricating oil impinging on a fixed plate. A large range of Prandtl numbers was considered ( 148 P r 925 ) in order to fill a data gap on highly viscous fluids, especially regarding local measurements. In the range of Reynolds numbers considered (170 5 z / d 20 ) showed no particular effect. Local and mean values of the Nusselt number were correlated by taking into account the above-mentioned parameters. Nevertheless, data exploitation showed that the warming of the thin liquid film over the plate, which is dependent on the heating flux to evacuate, should be taken into account for viscous fluids such as oils; the induced changes of viscosity lead to divergencies in measured heat exchanges. A methodology based on empirical observation was developed to take this phenomenon into consideration.