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Experimental study of the effect of sodium chloride on drying of porous media: The crusty–patchy efflorescence transition

Eloukabi, Houda and Sghaier-Ben Chiekh, Nour and Ben Nasrallah, Sassi and Prat, Marc Experimental study of the effect of sodium chloride on drying of porous media: The crusty–patchy efflorescence transition. (2013) International Journal of Heat and Mass Transfer, 56 (1-2). 80-93. ISSN 0017-9310

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Official URL: http://dx.doi.org/10.1016/j.ijheatmasstransfer.2012.09.045

Abstract

We present an experimental study of drying in the presence of dissolved sodium chloride. The process is characterized by the formation of a crystallized salt layer, referred to as efflorescence, at the evaporative surface of the porous medium. By varying the average size of the beads forming the porous medium, we show that the formation of the crystal layer does not affect significantly the drying process and can even enhance the drying rate when the beads are sufficiently large. By contrast, the crystal layer can greatly affect the drying process and even blocks or severely limit the evaporation process for sufficiently small beads. We therefore show the existence of two regimes, namely the blocking regime and the enhanced drying rate regime. It is shown that the two regimes correspond to two different types of efflorescence, referred to as crusty and patchy, respectively. Then by varying the initial salt concentration for a given bead size, we show that the interplay between drying and the efflorescence formation leads to a nonmonotonous variation of the drying rate with the initial salt concentration when the efflorescence is patchy but not when the efflorescence is crusty. The crusty–patchy transition is finally discussed from a simple model of capillary rise in the efflorescence.

Item Type:Article
Additional Information:Thanks to Elsevier editor. The original PDF can be found at http://www.sciencedirect.com/science/article/pii/S0017931012007478
HAL Id:hal-00951512
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:24 Feb 2014 18:08

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