Chemical Engineering Science, Vol.66, No.16, 3666-3674, 2011
A two-scale model for discrete cell gravure roll coating
A two-dimensional model for predicting the fluid pick out and coated film thickness characteristics of a discrete cell direct gravure roll coater operating in reverse mode is derived. A novel multiscale approach is adopted for this purpose and the resulting equations solved numerically for inertia-less flow conditions. A system of stiff ordinary differential equations is found to be sufficient to capture the major gross flow features, while at the cell level the analysis is based on a finite element solution of the momentum and continuity equations. It represents the first such predictive model of its kind, with particular interest placed on the nature of both the pressure distribution and web-to-roll gap profile spanning the coating bead. The effect of key operating parameters, web-to-roll speed ratio, web tension, wrap-angle, capillary number and cell-geometry, on the degree of fluid pick out from gravure cells and the coated film thickness is explored. Although an idealised model, the trends observed show qualitative agreement with existing experimental data collected on a small-scale gravure coating rig and point the way forward to the eventual formulation of a full three-dimensional predictive model of the process. Crown Copyright (C) 2011 Published by Elsevier Ltd. All rights reserved.
Keywords:Films;Fluid mechanics;Hydrodynamics;Mathematical modelling;Coating flows and gravure roll coating;Mathematical modelling and simulation