Pressure Drop in Entrance Flows from Cavity to Slot of Viscoelastic Fluids inside Slot Die

Abstract

In this work, entrance flows of viscoelastic fluids from a cavity to a slot in a slot die coating were investigated experimentally and numerically. Aqueous solutions of polyethylene glycol (PEG) and polyethylene oxide (PEO) mixtures, having viscoelasticity and Newtonian viscosity, were tested in order to clarify the effects of viscoelastic characteristics to the excess pressure drops at the entrance. The measured excess pressure drop changes corresponded to the flow pattern changes from a Newtonian-like flow pattern to vortex generation and growth patterns in an asymmetric entrance flow with a submillimeter slot. Numerical predictions of the transitions in the flow patterns and the pressure drops were also made utilizing exponential Phan-Thien-Tanner (EPTT) model with a finite element method. The predictions qualitatively indicated the increase in excess pressure drop and the vortex generation and growth.