The main aim of this project is to develop, test and validate modelling techniques for the evaluation of RH vacuum degasser performance with respect to steel cleanness. Principally, physical model and plant results on a wide variety of steel grade (ULC and high carbon steels) will be used to validate computational fluid dynamic models which will take into account coalescence of inclusions, thermal effects, thermodynamics of inclusions and dynamic interactions between melt/inclusions/gaseous phases. It will thus be possible to fully predict the range of inclusion composition and the level of cleanness of the steel with respect to treatment conditions.