MICROWAVE IRRADIATION AND CONVENTIONAL HEATING: A COMPARISON USING IN SILICO EXPERIMENTS WITH WATER AND ETHYLENE GLYCOL

In this paper, we compare numerically the behavior of two solvents, water and ethylene glycol, under two different heating mechanisms: microwave irradiation and conventional heating. The thermophysical and dielectric properties of each solvent determine how they are heated up. Under conventional heating, the temperature profiles show the development of thermal plumes at the bottom that move towards the lateral wall, with convection being the mechanism heating up the sample. For ethylene glycol, of higher viscosity than water, the number of thermal plumes is considerably reduced implying a slower heating of this solvent in comparison to water. However, under microwave irradiation, ethylene glycol heats faster than water due to its higher susceptibility to microwave irradiation. Temperature profiles show stratification and localization of a hotter region at the center of the sample for both solvents. In addition, microwave irradiation implies a faster heating of the sample, that increases with the microwave power. A three-dimensional temporal model is used which couples heat and momentum equations and Maxwell equations based on spectral element methods. Results are interesting as they provide, in silico, a full spatio-temporal description of temperature and flow velocity of the solvents under these two heating mechanisms.