A thick-layer drying kinetic model and drying characteristics of moisture-containing porous materials

Abstract

The thick-layer drying kinetics of moisture-containing porous material (honeysuckle) at constant temperature and humidity are experimentally investigated, and the drying characteristics under variable temperature and humidity conditions are analyzed in this paper. The results show that the drying rate is constant and linearly/positively corrected with the moisture content under constant temperature and humidity conditions, and the corresponding slope (drying rate constant) decreases exponentially with the increase in the number of stacked layers because of the increased flow resistance and diminished convective migration of water vapor. The migration of saturated water vapor changes from convection-dominated to diffusion-dominated after the thickness of the stacked materials exceeds a critical value. Based on the experimental data, a new semi-theoretical drying model was proposed for thin-layer and thick-layer drying of moisture-containing stacked porous materials, and it was experimentally verified with a coefficient of determination greater than 0.92. The relative humidity of the drying medium is a key factor in determining the drying rate, and reducing the relative humidity of the drying medium at a constant temperature is suitable for drying heat-sensitive materials. This paper can contribute to the development of drying kinetics and provide a theoretical basis for the drying of moisture-containing porous material.