Experimental investigations of high temperature industrial processes, for example the melting and smelting processes taking place inside furnaces, are complicated by the high temperatures and the chemically reactive environment in which they take place. Fortunately, mathematical models can be used in conjunction with the limited experimental results that are available to gain insight into these high temperature processes. However, mathematical models of high temperature processes require high temperature material properties, which are difficult to measure experimentally since container materials are often unable to withstand high enough temperatures, and sample contamination often occurs. These difficulties can be overcome by employing containerless processing techniques such as electromagnetic levitation melting to allow for characterisation of high temperature material properties. Efficient design of electromagnetic levitation cells is challenging since the effects of changes in coil design, sample size and sample material on levitation force and sample temperature are not yet well understood. In this work a numerical model of the electromagnetic levitation cell is implemented and used to investigate the sensitivity of levitation cell operation to variations in coil design, sample material and sample size. Various levitation cell modelling methods in literature are reviewed and a suitable model is chosen, adapted for the current application, and implemented in Python. The finite volume electromagnetic component of the model is derived from Maxwell’s equations, while heat transfer is modelled using a lumped parameter energy balance based on the first law of thermodynamics. The implemented model is verified for a simple case with a known analytical solution, and validated against published experimental results. It is found that a calibrated model can successfully predict the lifting force inside the levitation cell, as well as the sample temperature at low coil currents. The validated model is used to characterise the operation of a levitation cell for a number of different sample materials and sample sizes, and for variations in coil geometry and coil current. The model can be used in this way to investigate a variety of cases and hence to support experimental levitation cell design. Based on model results, a number of operating procedure recommendations are also made. / Dissertation (MEng)--University of Pretoria, 2016. / Mechanical and Aeronautical Engineering / MEng / Unrestricted

<p> Levitation melting was used to study the oxidation kinetics of free falling iron droplets. Single droplets of Armco iron were deoxidized and allowed to fall through oxidizing columns of known heights and then quenched in Silicone Oil. The rate of oxygen pick up by a droplet was found to be dependent upon its initial temperature, its size, and the composition of the reacting gas. The proposed mechanism is presented with kinetic data.</p> / Thesis / Master of Engineering (MEngr)

<p> Levitation melting was used to measure the equilibrium between H2-H2o or CO-C02 gas mixtures and pure Fe or Fe-Cr alloys over the temperature range 1550 - 1750°C. The effects of thermal diffusion on the two types of gases were investigated. First and second order interaction parameters were employed to describe the interaction between oxygen and chromium {up to 25 wt. pct. of Cr.). </p> / Thesis / Master of Science (MSc)