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Drop penetration into porous powder beds
Karen P Hapgood1, James D Litster, Simon R Biggs
1Department of Chemical Engineering, University of Queensland, Brisbane, Queensland, Australia 4072. karen_hapgood@merck.com
Journal of Colloid and Interface Science
|November 18, 2005
Summary
This study investigated fluid drop penetration into powders, finding existing models inadequate. A new two-phase model incorporating macrovoids improved penetration time predictions.
Area of Science:
- Physical Chemistry
- Materials Science
- Fluid Dynamics
Background:
- Drop penetration into powders is crucial in pharmaceutical and chemical industries.
- Existing models fail to accurately predict penetration times due to powder bed heterogeneity.
Purpose of the Study:
- To investigate the kinetics of fluid drop penetration into various powder beds.
- To develop an improved model for predicting drop penetration times.
Main Methods:
- Filming single drops of fluids (water, PEG200, PEG600, HPC) penetrating powder beds (glass ballotini, lactose, zinc oxide, titanium dioxide).
- Comparing experimental data with existing theoretical models.
- Developing a new two-phase model accounting for macrovoids and effective porosity.
Main Results:
- Experimental penetration times varied based on powder particle size, fluid viscosity, surface tension, and contact angle.
- Existing theoretical models showed poor agreement with experimental results.
- The new two-phase model significantly improved the estimation of drop penetration times, with predictions generally within an order of magnitude of experimental values.
Conclusions:
- Powder bed macrovoids significantly impact fluid penetration kinetics.
- The proposed two-phase model, defining effective porosity, provides a more accurate prediction of drop penetration times.
- This improved model has implications for processes involving fluid-powder interactions.