Insights in mechanism of drying shrinkage by pore-scale modeling of heat-moisture and stress-strain distribution for high-moisture porous media

Abstract

Drying shrinkage occurs accompanying with heat-moisture transfer during drying process of high-moisture porous media and forming mechanism of drying shrinkage is complicated and influenced by micro-pore structure characteristics of porous media. In order to explore the forming mechanism of shrinkage caused by drying, the pore-scale modeling of heat-moisture and stress-strain distributions for high-moisture porous media was directly established considering the effect of micro-pore structure characteristics of porous media in drying process and analyzed using self-developed pore network simulation algorithm. Simulation results indicated that the drying curves (moisture vs drying time, average temperature vs drying time, and shrinkage vs drying time) were in a good agreement with hot-air drying experimental measurement using apple slices as the typical representation of high-moisture porous media. The phenomenon of dry spots, wet spots, irregular drying front, and irregular asymmetric shrinkage were reflected through pore network simulation. Capillary stress was a key factor affecting drying shrinkage and capillary stress was negative related to the porosity of materials and positive related to the coordination number of materials. Capillary stress produced by materials with uniform diameter distribution was larger, followed by the distribution of normal distribution materials and experimental materials. The findings in current elucidate the mechanism of drying shrinkage and provide insights into drying optimization of high-moisture porous media.