Heat balance in levitation melting: Sample cooling by forced gas convection in Helium
Georg Lohöfer and Stephan Schneider
Electromagnetic levitation melting is a containerless processing technique for liquid metals requiring non-contact diagnostic tools. In order to properly perform such experiments, a precise knowledge of the temperature-time behaviour of the metal sample resulting from the heat balance between its heating and cooling during the processing is a prerequisite. In two preceding papers we provided the necessary theoretical background for the inductive heat input by the high frequency magnetic levitation field and the heat loss due to radiation and heat conduction through a surrounding process gas atmosphere and defined the set of experiments needed for obtaining the key parameters of the thermal model. In the present paper we extend the previous work by investigating theoretically and, at hand of further tests under microgravity, experimentally the influence of the sample cooling by forced gas convection at low Péclet number in a surrounding Helium atmosphere.
Keywords: Electromagnetic levitation, containerless processing, microgravity, gas cooling, forced convection