Influence of irradiation time, particle sizes, and initial moisture content during microwave drying of multi-layered capillary porous materials

The drying of capillary porous materials by microwave with rectangular waveguide has been investigated numerically and experimentally. Most importantly, it focuses on the investigation of the distributions of electric field, temperature and moisture profiles within the capillary porous materials. The measurements of temperature and moisture distributions within the capillary porous materials provide a good basis for understanding of the microwave drying process. The mathematical model gives qualitatively comparable trends to experimental data. The calculations of electromagnetic fields inside the rectangular waveguide and the capillary porous materials show that the variation of particle sizes and initial moisture content changes the degree of penetration and rate of microwave power absorbed within the sample. Further, the small particle size leads to much higher capillary pressure resulting in a faster drying time.