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Porous medium coffee ring effect and other factors affecting the first crystallisation time of sodium chloride at the surface of a drying porous medium

Hidri, Faiza and Sghaier-Ben Chiekh, Nour and Eloukabi, Houda and Prat, Marc and Ben Nasrallah, Sassi Porous medium coffee ring effect and other factors affecting the first crystallisation time of sodium chloride at the surface of a drying porous medium. (2013) Physics of Fluids, 25. 1-23. ISSN 1070-6631

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Official URL: http://dx.doi.org/10.1063/1.4834356

Abstract

We study the distribution of ions in a drying porous medium up to the formation of first crystals at the surface. The study is based on comparisons between numerical simulations and experiments with packings of glass beads. The experimental configuration, which is representative of many previous drying experiments, is characterized by the formation of an efflorescence fairy ring at the surface of the porous medium. The preferential formation of crystals at the periphery is explained by the combined effect of higher evaporation fluxes at the surface periphery, as in the classical coffee ring problem, and variations in the porosity near the wall bordering the packing. It is shown that both effects have a great impact on the time marking the occurrence of first crystals, which is referred to as the first crystallization time. The experiments indicate that the first crystallization time increases with a decreasing bead size for a given initial ion concentration. This is explained by the variation with bead size of the characteristic size of the near wall region where a preferential desaturation of the sample occurs as a result of the porosity increase near the wall. The study also reveals a significant salt supersaturation effect. This represents a noticeable fact in relation with salt weathering issues.

Item Type:Article
Additional Information:Thanks to AIP Publishing. The definitive version is available at http://scitation.aip.org/content/aip/journal/pof2/25/12/10.1063/1.4834356?showFTTab=true&containerItemId=content/aip/journal/pof2
HAL Id:hal-00952047
Audience (journal):International peer-reviewed journal
Uncontrolled Keywords:
Institution:French research institutions > Centre National de la Recherche Scientifique - CNRS (FRANCE)
Université de Toulouse > Institut National Polytechnique de Toulouse - Toulouse INP (FRANCE)
Université de Toulouse > Université Toulouse III - Paul Sabatier - UT3 (FRANCE)
Other partners > Université de Monastir - UM (TUNISIA)
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Deposited On:26 Feb 2014 09:36

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