Detailed numerical simulation of short-term microgravity experiments to determine heat conductivity of melts

In the frame of an international cooperation a 4 year long project was executed to determine thermal conductivity in metallic melts. During the project, the University of Miskolc designed and developed unique apparatus which was capable to perform measurements under microgravity conditions. The experiments were carried out at the Drop Tower Bremen" where the conditions of reduced gravity could be provided for 4.7 s and a gravity level of 10(-5)g was achieved. The registered temperature distribution data of the examined melts always show a clear difference between the experiments measured in the normal and in the low gravity environment. During the evaluation of the datasets it was proven, that the well known canonical evaluations could not be used with high reliability for all the measurements, for all the materials and for all the geometry used. Besides of the understanding of the underlying physics and evaluating the measured data, the Crank-Nicolson method and error function analysis were used at the beginning, some numerical analyses were also initiated to simulate the system in FEM (Marc). The results showed acceptable results, but also pointed out a need for further study, so a detailed numerical analysis on a specialized FVM (Fluent) system was started. The code used for the numerical simulation (Fluent) was able to handle the heat conductivity, the liquid flow, the complex material parameters changes and the used geometries as well. With this technique, from the data of the drop experiments, the pure - free from the effect of the liquid flow - thermal conductivity could be separated. The results show that after these simulations, using different conditions (temperature, gravity level, etc.) for one material the same thermal conductivity value could be determined, within acceptable tolerance.