Premiers instants du refroidissement d'une goutte métallique après son impact sur une paroi

Abstract

This paper presents an experimental study of the evolution of thermal contact conditions (temperature jump at the interface, heat flux and transient thermal contact resistance) during the first stages of solidification of a liquid metal drop on a water-cooled wall. Two complementary approaches were developed. The first method, valid for times longer than 10 −3 s, is based on the use of one temperature measurement inside the solidifiying drop, using a usual thermocouple, and several temperature measurements in the wall using very fine semi-intrinsic thermocouples installed near the active surface. By solving an inverse heat conduction problem in both regions (drop, wall), this method allows a local thermal characterization. The second approach uses an intrinsic method, based on the use of metal drop and wall as two thermocouple elements, to measure the mean micro-contact temperature of drop and wall. This kind of sensor, without inertia, has approximatively the time delay of fast data acquisition ( t c < 10 −6s). The measured temperature represents the mean surface temperature of all the contact areas of drop and wall. The physical interpretation of this kind of measurement is difficult and needs the development of a new theoretical model. We can already observe that at t = 0 +, the measured temperature is close to the theoretical one, ie, the interface temperature contact of two semi-infinite media, the liquid metal drop and the wall (effusivity ratio). This means that solidification has not yet taken place.