MRI evidence for a "coffee-front effect" in drying porous media
Résumé
After drying colloidal particles suspended in a porous medium a concentration gradient appears. Using 1H MRI we propose a protocol to observe simultaneously the distributions of air, liquid, and colloid through the unsaturated solid porous structure. Thus we show that the above phenomenon comes from a receding-front effect: The elements migrate towards the free surface of the sample and accumulate in the remaining liquid films. Our understanding of the process makes it possible to establish a simple model without diffusion predicting the drying rate and the concentration distribution in time, in excellent agreement with the experimental observations. © 2013 American Physical Society.
Domaines
Sciences de l'ingénieur [physics] Mécanique [physics.med-ph] Mécanique des solides [physics.class-ph] Physique [physics] Mécanique [physics] Mécanique des solides [physics.class-ph] Sciences de l'ingénieur [physics] Mécanique [physics.med-ph] Mécanique des matériaux [physics.class-ph] Physique [physics] Mécanique [physics] Mécanique des matériaux [physics.class-ph]
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