Electronic Thesis and Dissertation Repository

Degree

Doctor of Philosophy

Program

Chemical and Biochemical Engineering

Supervisor(s)

Andrew N. Hrymak

Abstract

Dip coating of liquid film deposition on cylindrical substrates is studied using mathematical modeling, numerical simulation and experimental investigation. A mathematical model based on the Landau-Levich approach for dip coating has been developed using the Ellis constitutive equation, for cylindrical geometries, to analyze the effects on the coating thickness of the substrate radius and hydrodynamic behavior for a non-Newtonian fluid. The influence of the viscosity at low shear rates near the surface of the withdrawal film is included in the Ellis model and coating thickness results for Ellis, power law and Newtonian models are compared with experimental data. Good agreement for the measured and predicted coating thickness was obtained with the Ellis model.

Dip coating process is numerically simulated to understand the effects of the proximity of the coating bath wall to the substrate. The free surface position is determined by the volume of fluid technique applying Carreau, power law and Newtonian constitutive models in a three dimensional system, including density, viscosity and surface tension effects. Numerical calculations have been performed in an open source CFD software package of OpenFOAM. Numerical outcomes are validated with experimental data over a range of withdrawal velocities up to 6 , capillary range and a dimensionless range of distance, 4 to 60 for bath radius to the substrate radius being withdrawn.

Finally, dip coating of dispersions is examined with particle distribution in the free-surface concentrated suspensions studied by developing a numerical algorithm in a computational fluid dynamic platform based on the particle diffusion-flux model. The numerical predictions are for finite length cylinder being pulled out of a concentrated suspension bath in the unsteady condition. The initial rigid particle volume fraction of 0.1-0.4 and the withdrawal velocity varies in the range of 0.05-0.15 and capillary number range of . Simulation results are compared against experimental data with good agreement in the predicted coating thickness.


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