Numerical modeling of microwave induced natural convection inside a rectangular wave guide

The heating of liquid layer by microwave in a rectangular wave guide has been investigated numerically and experimentally. It was performed for two different liquids, water and NaCl-water solution. A complete mathematical model is proposed, which uses a comprehensive two-dimensional heat and momentum equations to describe unsteady temperature and fluid flow fields, coupled with a complete solution of the three-dimensional Maxwell´s equations in the time domain (FDTD), can be used to investigate many aspects of heating process. In this study, the effects of the electric conductivity (which corresponds to the percentage by weight of NaCl in liquid layer) and microwave power level on the heating process were examined. Based on a model combining the Maxwell and heat transport and fluid flow equations, the results showed that the heating process strongly depends on the dielectric properties.