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Drop penetration into porous powder beds
journal contributionposted on 2002-09-15, 00:00 authored by Karen HapgoodKaren Hapgood, J D Litster, S R Biggs, T Howes
The kinetics of drop penetration were studied by filming single drops of several different fluids (water, PEG200, PEG600, and HPC solutions) as they penetrated into loosely packed beds of glass ballotini, lactose, zinc oxide, and titanium dioxide powders. Measured times ranged from 0.45 to 126 s and depended on the powder particle size, viscosity, surface tensions, and contact angle. The experimental drop penetration times were compared to existing theoretical predictions by M. Denesuk et al. (J. Colloid Interface Sci.158, 114, 1993) and S. Middleman ("Modeling Axisymmetric Flows: Dynamics of Films, Jets, and Drops," Academic Press, San Diego, 1995) but did not agree. Loosely packed powder beds tend to have a heterogeneous bed structure containing large macrovoids which do not participate in liquid flow but are included implicitly in the existing approach to estimating powder pore size. A new two-phase model was proposed where the total volume of the macrovoids was assumed to be the difference between the bed porosity and the tap porosity. A new parameter, the effective porosity epsilon(eff), was defined as the tap porosity multiplied by the fraction of pores that terminate at a macrovoid and are effectively blocked pores. The improved drop penetration model was much more successful at estimating the drop penetration time on all powders and the predicted times were generally within an order of magnitude of the experimental results.
JournalJournal of Colloid and Interface Science
Pagination353 - 366
LocationMaryland Heights, Mo.
Publication classificationC Journal article; C1.1 Refereed article in a scholarly journal
Copyright notice2002, Elsevier Science (USA)
CategoriesNo categories selected
Drop penetrationEffective porosityGlassGranulationImbibitionKineticsLactoseModels, TheoreticalNucleationParticle SizePore sizePorous powder bedsPolyethylene GlycolsPorosityPowdersSurface PropertiesSurface TensionTitaniumWaterWettabilityZinc OxideScience & TechnologyPhysical SciencesChemistry, PhysicalChemistryDYNAMIC CONTACT-ANGLECAPILLARY PENETRATIONLIQUIDPRESSUREFLUIDSRISE