Coupled electromagnetics, multiphase transport and large deformation model for microwave drying

• Comprehensive description of microwave drying with all relevant physics.
• Electromagnetics, multiphase transport and large deformation solid mechanics are three-way coupled.
• Mechanical deformation critically affects electromagnetics and heat and moisture transport.
• Volume change is primarily due to moisture loss.
• Pressure gradients within the material are responsible for stress development.

The present work involves development of a fundamentals-based coupled electromagnetics, multiphase transport and large deformation model to understand microwave drying of a hygroscopic porous material. Microwave drying is carried out in a 950 W domestic microwave oven operating at 10% power level. Electric field distribution inside the oven cavity and porous material are obtained by solving Maxwell's equations for electromagnetics. Modes of fluid transport include capillarity, binary diffusion and gas pressure-driven flow. Large deformation, included by treating the solid as hyperelastic, is implemented in a novel way using the Arbitrary-Lagrangian–Eulerian framework for mesh movement. Deformation during microwave drying was found to critically alter material structure that significantly affected microwave absorption, heat and moisture transport within the material. Sensitivity analysis revealed that moisture loss and volumetric shrinkage were unaffected with changes in intrinsic permeability and elastic modulus of the material while stress state within the material was highly sensitive to elastic modulus values.