Improving Flow Balancing: Employing GNF-X for Predicting Flow Profile

Abstract

Flow balancing is the process of changing the geometry of an extrusion die to achieve a uniform flow distribution at the die-exit. This can be an iterative and costly process. Computational Fluid Dynamics (CFD) is often used to aid in flow balancing of extrusion dies by predicting the flow profile without the need for experiments. The numerical models used in literature simplify the behavior significantly by using a Generalized Newtonian Fluid (GNF) approach. This study investigates the effects of applying the recently introduced GNF-eXtended (GNF-X) model to the flow balancing problem for molten polymers. This aims to include the effect of extensional flow on the materials apparent viscosity and increase the accuracy of numerical predictions. The model was implemented into ANSYS CFX and the effects on the flow balance of an extrusion die evaluated. A substantial impact was observed on the flow distribution at the die-exit when using the GNFX model instead of the GNF version. The prediction of the flow balance with the GNF-X model differs by a factor of up to two with the GNF model, underlining the importance of including extensional flow behavior.