Abstract
Moisture transport is an important phenomenon in many technological fields. We summarize a fundamental description method with use of the relative permeability and the moisture diffusion coefficient. The theoretical approach for the two-phase flow in the porous media is based on the extended Darcy model. The relative permeability and the moisture diffusion coefficient are functions of the moisture content and they express the effects of the friction loss and the capillary pressure, respectively. The model is applied to the microwave vacuum drying of food, where the vapor pressure drives the moisture from the inner to the outer because of the internal heating by the microwave irradiation. The numerical moisture-distributions are compared with the experimental results obtained by the MRI. It is shown that the microwave vacuum drying gives a desirable moisture-distribution for the drying.
