3-DIMENSIONAL FINITE-ELEMENT ANALYSIS OF POLYMERIC FLUID-FLOW IN AN EXTRUSION DIE .1. ENTRANCE EFFECT

The Galerkin finite element method has been applied to study the three -dimensional flow field of power-law fluids inside an extrusion die. T wo inlet designs, i.e., center-fed and end-fed, have been considered. The effects of inertial force as represented by the Reynolds number Re , inlet geometry, and the power-law index n on lateral flow uniformity and vortex formation in the entrance region have been examined. A flo w visualization technique has been carried out to experimentally verif y the theoretical prediction of the three-dimensional flow field insid e a die. It has been found that increasing Re or decreasing n will det eriorate flow uniformity. Depending on the direction of the inlet jet stream, the inertial force may create a flow peak in the central regio n of a center-fed die, or the maximum flow rate will appear close to t he end of the die for an end-fed die. For highly shear-thinning fluids , lower flow rates are always observed close to the end of the dies. I t is concluded that creating a plug flow in the inlet tube of the extr usion die is advantageous for both center-fed and end-fed designs.