HR: 0800h
AN: H21D-0748    [Abstracts]
TI: Neutron Radiography Measurements Of Phase Distributions And Transport Mechanisms During Drying Of Hydrophobic And Hydrophilic Coarse Porous Media
AU: * Shokri, N
EM: nima.shokri@epfl.ch
AF: Laboratory of Soil and Environmental Physics (LASEP), EPFL / ENAC / ISTE / LASEP GR A1 444(Bâtiment GR) Station 2, Lausanne, CH-1015, Switzerland
AU: Lehmann, P
EM: peter.lehmann@epfl.ch
AF: Laboratory of Soil and Environmental Physics (LASEP), EPFL / ENAC / ISTE / LASEP GR A1 444(Bâtiment GR) Station 2, Lausanne, CH-1015, Switzerland
AU: Willson, C
EM: cwillson@lsu.edu
AF: Department of Civil and Environmental Engineering, Civil & Environmental Engineering Department 3418 CEBA - LSU, Baton Rouge, LA 70803, United States
AU: Vontobel, P
EM: Peter.Vontobel@psi.ch
AF: Spallation Neutron Source Division, ASQ Division WBBA 107 Paul Scherrer Institut, Villigen, CH-5232, Switzerland
AU: Or, D
EM: dani.or@epfl.ch
AF: Laboratory of Soil and Environmental Physics (LASEP), EPFL / ENAC / ISTE / LASEP GR A1 444(Bâtiment GR) Station 2, Lausanne, CH-1015, Switzerland
AB: Drying rate and patterns in porous media are strongly influenced by interplay between internal structural and transport properties and external boundary conditions. Liquid flow from the receding drying front to evaporating surface is induced by capillary gradients and sustained by liquid films connecting these domains. In addition to capillary influences, wettability may play a role in maintaining continuity of liquid films required for sustaining high evaporation rates. We used neutron radiography imaging coupled with direct mass-loss measurements of evaporation rates to link phase distributions with dominant transport mechanisms, and to deduce potential impacts on morphology and dynamics of drying fronts in hydrophobic and hydrophilic sands. Results suggest that drying front dynamics may be affected by surface wettability leading to early dominance of vapor diffusion in drying of hydrophobic sand. In contrast, the persistence of a network of liquid films in hydrophilic sand sustains prolonged stage 1 evaporation by liquid flow as the main transport mechanism. Differences in fluid phase distributions in hydrophobic and hydrophilic sands resolved by neutron transmission observations provide new insights into the nonlinear dependency of diffusion coefficient on water content distribution above the drying front, the impact of wettability on dispersion of receding front and liquid phase distribution affected by wettability of porous medium.
DE: 1800 HYDROLOGY
SC: Hydrology [H]
MN: 2007 Fall Meeting