The sol-gel route can produce highly porous solid aggregates with large surface area, which are u... more The sol-gel route can produce highly porous solid aggregates with large surface area, which are usually dried under supercritical conditions. Convective drying is not yet suited to produce such dry gels. In the small pores, the liquid-gas interface causes high capillary stress, which results in mechanical damage of the commonly very fragile solid. However, a better understanding of micro-scale phenomena inducing shrinkage, breakage or cracks during convective drying is expected to lead to an extended range of applications for this inexpensive and safe process. We propose a 3D micro-scale model for convective drying, which resolves the three phases (solid, liquid, and gas). The solid phase is described as an aggregate of rigid primary particles, which are accelerated by capillary and contact forces. The diameter of the primary particles also determines the characteristic length scale of the problem, which is ~10-8 m. At this length scale, gravitational forces are negligible compared ...
International Journal of Heat and Mass Transfer, 2008
The influence of heat transfer on the drying behaviour of capillary porous media saturated with w... more The influence of heat transfer on the drying behaviour of capillary porous media saturated with water is studied. To overcome the limitations of continuum approaches, a pore network model based on statistical physics and invasion percolation is used. The presented non-isothermal model is the first of its kind to describe free evolution of temperatures in convective drying. Gas-side mass transfer
ABSTRACT A discrete three-dimensional model for the fluid flow and phase transition at the micros... more ABSTRACT A discrete three-dimensional model for the fluid flow and phase transition at the microscopic scale during convective drying of highly porous particle aggregates has been developed. The phase distributions are described by time-dependent cell volume fractions on a stationary cubic mesh. The solid phase volume fractions are computed from an arbitrary collection of spherical primary particles generated by gravitational deposition using the discrete element method. The volume of fluid method is used to track the liquid–gas interface over time. Local evaporation rates are computed from a finite difference solution of a vapor diffusion problem in the gas phase, and the liquid–gas interface dynamics is described by volume-conserving mean curvature flow, with an additional equilibrium contact angle condition along the three-phase contact lines. The evolution of the liquid distribution over time for different wetting properties of the solid surface as well as binary liquid bridges between solid particles are presented.
The sol-gel route can produce highly porous solid aggregates with large surface area, which are u... more The sol-gel route can produce highly porous solid aggregates with large surface area, which are usually dried under supercritical conditions. Convective drying is not yet suited to produce such dry gels. In the small pores, the liquid-gas interface causes high capillary stress, which results in mechanical damage of the commonly very fragile solid. However, a better understanding of micro-scale phenomena inducing shrinkage, breakage or cracks during convective drying is expected to lead to an extended range of applications for this inexpensive and safe process. We propose a 3D micro-scale model for convective drying, which resolves the three phases (solid, liquid, and gas). The solid phase is described as an aggregate of rigid primary particles, which are accelerated by capillary and contact forces. The diameter of the primary particles also determines the characteristic length scale of the problem, which is ~10-8 m. At this length scale, gravitational forces are negligible compared ...
International Journal of Heat and Mass Transfer, 2008
The influence of heat transfer on the drying behaviour of capillary porous media saturated with w... more The influence of heat transfer on the drying behaviour of capillary porous media saturated with water is studied. To overcome the limitations of continuum approaches, a pore network model based on statistical physics and invasion percolation is used. The presented non-isothermal model is the first of its kind to describe free evolution of temperatures in convective drying. Gas-side mass transfer
ABSTRACT A discrete three-dimensional model for the fluid flow and phase transition at the micros... more ABSTRACT A discrete three-dimensional model for the fluid flow and phase transition at the microscopic scale during convective drying of highly porous particle aggregates has been developed. The phase distributions are described by time-dependent cell volume fractions on a stationary cubic mesh. The solid phase volume fractions are computed from an arbitrary collection of spherical primary particles generated by gravitational deposition using the discrete element method. The volume of fluid method is used to track the liquid–gas interface over time. Local evaporation rates are computed from a finite difference solution of a vapor diffusion problem in the gas phase, and the liquid–gas interface dynamics is described by volume-conserving mean curvature flow, with an additional equilibrium contact angle condition along the three-phase contact lines. The evolution of the liquid distribution over time for different wetting properties of the solid surface as well as binary liquid bridges between solid particles are presented.
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