Abstract:
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.
