Hybrid Thermal Treatment Based on Microwaves and Heating Resistance for Composite Materials

Abstract

Nowadays, it is well known that volumetric heating through microwaves inhibits certain surface properties from being achieved. Similarly, exclusively heating via thermal radiation is neither deep nor homogeneous enough for short periods of time. But combining both approaches can alleviate such issues. In fact, this kind of hybrid heating has been used for many years in real processes for thermal treatment of composite materials. Nonetheless, many questions remain unsettled. In this manuscript, we discuss the modeling and simulation of such a hybrid system, when heating a heterogeneous load composed of a solid core with three concentric spherical shells. The heating sources are given by electromagnetic waves in the microwave range, and by constant thermal radiation over one of the outer hemispheres. Only the core is considered to absorb the energy transported by the electromagnetic waves (high dielectric loss material). Hence, shells are transparent to microwaves (low dielectric loss materials). The thermophysical properties were considered constant with position. For all cases, peak temperature was observed in the geometrical center of the system, as has been shown by experimentation. Furthermore, simulation results revealed that this hybrid heating strategy has a drastic effect on the temperature profiles generated with only microwave, although the surface temperature homogeneity can be improved using an external electrical resistance.