Experimental and parametric analyses of heat transfer within two-layered packed beds of iron and graphite in a high-frequency induction furnace

An experimental and theoretical study on heat transfer within two-layered packed beds of iron and graphite in a high-frequency induction furnace is described. 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 Fe was taken into account in the model. The experimental results showed that Fe 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 Fe and graphite on the heating rate of Fe spheres was assessed. As a result, the heating rate of Fe spheres was found to be significantly dependent 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.