Changes in micropore structure and moisture transport properties in fibrous porous media after ultrasound treatment

The binding force between water molecules and the solid skeleton of fibrous porous media, determined by the microscopic structure and chemical interactions, has a remarkable influence on the dehydration process. Therefore, the micropore structure is a key factor affecting the dewatering performance of fibrous porous media. In this paper, fibrous porous media is treated by ultrasound; then the micropore structure images are obtained. After that, structural characteristics parameters in the field of statistics and fractal theory are obtained by analysing microscopic images to investigate the effect of mechanical action and cavitation on microscopic structure under different sonication conditions. Finally, the effect of structure change on moisture removal is studied experimentally. It turns out that power and treatment times are the main factors that determine the effect of ultrasound on the pore structure of fibrous porous media. With the increase of power and time, the average pore size, the pore size with maximum ratio, the surface porosity and the surface fractal dimension increase non-linearly. Moreover, the growth is nonlinear; the maximum variation of pore structure is achieved at 530 W for 40 min. The moisture content loss rate and the effective moisture content diffusion coefficient are enhanced by the variation of micropore structure.