Abstract
This paper describes an experimental and theoretical study on heat transfer within two-layered packed beds of iron and graphite in a high-frequency induction furnace. An unsteady, two-dimensional mathematical model for the induction furnace was developed in cylindrical coordinates and was verified by the experimental results. Temperature dependence of physical properties of packing materials such as magnetic transformation of iron was needed to be taken into account in the model. The experimental results showed that iron spheres near the wall were heated most quickly.
Parametric analysis was performed by using this mathematical model to investigate optimum operation conditions. The influence of supplied current, induced frequency, voidage and diameter of graphite particles and layer height ratio of iron and graphite on the heating rate of iron spheres was assessed. As a result, the heating rate of iron spheres was found to be significantly dependant on the supplied current, the frequency and the layer height ratio. Interestingly, small graphite particles were well heated although their diameter is less than the skin depth in the furnace. These results suggest the possibility of dense packing of graphite near the wall in the high-frequency induction furnace for efficient heating.
