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Free drainage in aqueous foams: Model and experimental study
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Free drainage in aqueous foams: Model and experimental study

S.A. Magrabi, B.Z. Dlugogorski and G.J. Jameson
AIChE Journal, Vol.47(2), pp.314-327
2001
DOI: https://doi.org/10.1002/aic.690470210
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Abstract

Free drainage in compressed-air foams were studied experimentally and theoretically. The time evolution of liquid holdup profiles in a 0.2-m-high by 0.29-m-diameter foam column was determined at various heights by measuring sonic velocity. A new experimental technique was devised to measure the true drainage rate of surfactant solution leaving the foam column. A drainage model was outlined to predict the discharge rate and evolution of the liquid-fraction profile in aqueous foams. The model led to the formulation of a nonlinear partial differential equation in which the liquid fraction was used explicitly as a dependent variable. The model was applied with one adjustable parameter to simulate drainage in foams made from fluorocarbon surfactants containing mobile plateau border and film walls. The liquid-fraction profiles, drainage rates, and final equilibrium liquid profiles depended strongly on the surface mobility of plateau border and film walls; the bubble size; and therefore on the coarsening history in the foam under study. Over longer time periods this model needs to be coupled with inter-bubble gas diffusion to account for coarsening-induced drainage. Free drainage in compressed-air foams were studied experimentally and theoretically. The time evolution of liquid holdup profiles in a 0.2-m-high by 0.29-m-diameter foam column was determined at various heights by measuring sonic velocity. A new experimental technique was devised to measure the true drainage rate of surfactant solution leaving the foam column. A drainage model was outlined to predict the discharge rate and evolution of the liquid-fraction profile in aqueous foams. The model led to the formulation of a nonlinear partial differential equation in which the liquid fraction was used explicitly as a dependent variable. The model was applied with one adjustable parameter to simulate drainage in foams made from fluorocarbon surfactants containing mobile plateau border and film walls. The liquid-fraction profiles, drainage rates, and final equilibrium liquid profiles depended strongly on the surface mobility of plateau border and film walls; the bubble size; and therefore on the coarsening history in the foam under study. Over longer time periods this model needs to be coupled with inter-bubble gas diffusion to account for coarsening-induced drainage.

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Citation topics
2 Chemistry
2.190 Surfactants, Lipid Bilayers & Antimicrobial Peptides
2.190.215 Critical Micelle Concentration
Web Of Science research areas
Engineering, Chemical
ESI research areas
Chemistry
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