Changes in micropore structure and moisture transport properties in fibrous porous media after ultrasound treatment
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ORIGINAL
Changes in micropore structure and moisture transport properties in fibrous porous media after ultrasound treatment Panpan Li 1,2 & Enhai Liu 3 & Zhenqian Chen 2 Received: 2 July 2020 / Accepted: 14 September 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract 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. Keywords Ultrasound . Fibrous porous media . Micropore structure . Moisture transport
Nomenclature a, b, c, n empirical coefficients obtained by fitting the experimental data. De effective moisture content diffusion coefficient (m2/min). k dehydration rate in drying process (min−1). MR dimensionless moisture ratio. RH relative humidity (%). t dehydration time (min). T ambient temperature (°C).
* Enhai Liu [email protected] * Zhenqian Chen [email protected] 1
School of Environmental and Municipal Engineering, North China University of Water Resources and Electric Power, Zhengzhou 450046, People’s Republic of China
2
School of Energy and Environment, Southeast University, Nanjing 210096, People’s Republic of China
3
School of Petroleum Engineering, Changzhou University, Changzhou 213164, People’s Republic of China
v X Xe X0
air velocity (m/s). dry basis moisture content at the given time (kg water/kg dry solids). equilibrium dry basis moisture content (kg water/kg dry solids). initial dry basis moisture content (kg water/kg dry solids).
1 Introduction Fibrous porous media which have the advantages of abundance, large specific area and low density are widely used in the fields of textile, military, medical, biology and architecture, in products such as fireproof suit, flight suits and medical textiles. Therefore, it is very important to study the mechanism of heat and mass tran
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