Drying Experiments in a Hydrophobic Model Porous Medium in the Presence of a Dissolved Salt

Eloukabi, H.; Sghaier, N.; Prat, Marc; Nassrallah, Sassi Ben

doi:10.1002/ceat.201100064

Cited by 25 publications

(22 citation statements)

References 32 publications

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“…10 is a consequence of the coupling between the evaporation process and the transfers in both the porous medium and the growing efflorescence. It can be noted that such a nonmonotonous behavior was also observed in the experiments with a micromodel presented in [13] as well as in the drying experiments from long sand column discussed in [16]. As in our experiments, these experiments are characterized by the major development of efflorescence in the first phase of drying.…”

Section: Influence Of Initial Salt Concentration On Drying With Patchsupporting

confidence: 68%

“…According to this analysis, the efflorescence would grow from salt precipitation at its bottom (porous medium/efflorescence interface) rather than precipitation at the efflorescence outer surface. This analysis is not consistent with the experiments reported in [12][13][14][15] but might be relevant in the case of blocking crust formation, which is the case considered in [11]. This short review clearly illustrates that much remains to be done to fully understand the factors controlling the formation, growth and properties of efflorescence.…”

Section: Introductionmentioning

confidence: 45%

“…[1,11] and references therein, report that the efflorescence forms a crust, whose net effect is to severely limit the evaporation. On the other hand, other studies [12][13][14][15][16] do not report a significant blocking effect, at least as long as the efflorescence is hydraulically connected to the aqueous solution present within the porous medium. On the contrary, it is even observed that the efflorescence formation can even enhance the drying rate [12,13].…”

Section: Introductionmentioning

confidence: 95%

“…On the other hand, other studies [12][13][14][15][16] do not report a significant blocking effect, at least as long as the efflorescence is hydraulically connected to the aqueous solution present within the porous medium. On the contrary, it is even observed that the efflorescence formation can even enhance the drying rate [12,13]. Furthermore, there are also important differences in the analysis of the mechanisms controlling the efflorescence growth.…”

Section: Introductionmentioning

confidence: 95%

“…Furthermore, there are also important differences in the analysis of the mechanisms controlling the efflorescence growth. In [12][13][14][15][16], the efflorescence is seen as a set of isolated porous structures saturated by the aqueous solution and growing as a result of salt precipitation at the outer surface of efflorescence structures where evaporation takes place. Growth stops when the efflorescence ceases to be hydraulically connected to the aqueous 0017-9310/$ -see front matter Ó 2012 Elsevier Ltd. All rights reserved.…”

Section: Introductionmentioning

confidence: 99%

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

Eloukabi

Sghaier

Nasrallah

et al. 2013

International Journal of Heat and Mass Transfer

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114

107

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a b s t r a c tWe 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.

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Section: Influence Of Initial Salt Concentration On Drying With Patchsupporting

confidence: 68%

Section: Introductionmentioning

confidence: 45%

Section: Introductionmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

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

Eloukabi

Sghaier

Nasrallah

et al. 2013

International Journal of Heat and Mass Transfer

Self Cite

114

107

View full text Add to dashboard Cite

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Effect of salt types on salt precipitation and water transport in saline sandy soil

Wang,

Li,

Guo

et al. 2024

Hydrological Processes

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Salt precipitation on the surface of porous media significantly affects water transport processes. Most studies on salt precipitation mainly focused on single salts, but in nature, salt precipitation usually occurs as mixtures. Consequently, information on the crystallization of salt mixtures and its effect on water transport remains scarce. This study investigated the precipitation of mixtures (the mass ratios of NaCl:Na2SO4 were 3:7, 5:5, and 7:3, respectively) of NaCl (typical efflorescence) and Na2SO4 (typical subflorescence) in the initially saturated sandy soil columns and its effect on evaporation and compared it with the cases of the two salts individually. The results showed that salt mixtures exhibited a mixed pattern of crystals including both efflorescence and subflorescence, and the efflorescence showed granular aggregation, unlike the mono‐salts. The crystallization coverage of the salt mixtures was smaller than that of NaCl mono‐salt; high (7:3) and low (5:5 and 3:7) proportions of NaCl led to larger and smaller crystallization coverage than that of Na2SO4 mono‐salt, respectively. While the salt mixtures had less crystallization coverage than the mono‐salts, they showed lower evaporation because the salt mixtures formed a denser crystallization structure of efflorescence‐subflorescence‐soil layer, this crystallization structure exhibited greater inhibition of water vapour diffusion, thus reducing evaporation. In addition, the crystallization of the salt mixtures with higher NaCl proportion afforded greater resistance of evaporation. The mixed crystallization pattern formed by the salt mixtures significantly enhances the crystallization resistance to evaporation.

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Effects of evolving salt precipitation on the evaporation and temperature of sandy soil with a fixed groundwater table

Shi

2021

Vadose Zone Journal

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The effects of salt precipitation on water and heat transport in soil have garnered considerable attention. However, salt precipitation growth on the soil surface and its influence on soil evaporation and temperature under a fixed groundwater table are not well understood. Therefore, the objective of this study was to investigate the impact of the evolution of salt precipitation on evaporation and temperature in sandy soils with a fixed groundwater table depth (20 cm). The laboratory experiment consisted of two treatments for sand columns: one with fresh groundwater, and the other with saline groundwater. Regions with salt precipitates expanded laterally and vertically whereby a salt crust was formed that disconnected from the soil. The lateral growth of salt precipitation had a minor impact on evaporation as the soil remained wet, while mostly being covered by the salt crust. However, the elevated salt crust caused a sharp decrease (>60%) in the evaporation rate. Therefore, a new stage of saline soil evaporation was determined; the evaporation rate was further reduced by the elevated salt crust. Moreover, the soil profile temperature decreased when the soil was covered by the salt crust, which is likely attributable to the increased albedo and the formation of a layer of air owing to the elevated salt crust. Therefore, we suggest that the upward growth of salt precipitation should be comprehensively studied because it can cause significant reductions in evaporation rates and soil temperature.Abbreviations: PVC, polyvinyl chloride; SS1, SS2, SS3, and SS4, the four stages of saline soil evaporation, in their order of occurrence This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.

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Drying Experiments in a Hydrophobic Model Porous Medium in the Presence of a Dissolved Salt

Cited by 25 publications

References 32 publications

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

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

Effect of salt types on salt precipitation and water transport in saline sandy soil

Effects of evolving salt precipitation on the evaporation and temperature of sandy soil with a fixed groundwater table

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