Analysis of isothermal flow of a Phan-Thien—Tanner fluid in a simplified model of a single-screw extruder

An analytical solution is obtained for the flow in a simplified model of the shallow single screw extruder of polymer melts described by the simplified Phan-Thien—Tanner fluid with linear kernel function. To arrive at the analytical solution in the rectangular channel, both the effects of the channel curvature and of the spanwise coordinate are neglected in the flow (shallow channel/extruder) and the fluid properties are considered to be temperature-independent. The two Couette–Poiseuille flows are coupled via the nonlinear constitutive equation and the results are presented in dimensionless form as a function of all relevant dimensionless numbers. The results show that as shear-thinning is enhanced there is a decrease in the ratio between the strengths of the main and secondary flows and in the dimensionless pressure rise through the extruder.

► Exact analytical solution for flow of PTT fluid in a model of a shallow single screw extruder.
► Screw extruder modeled as shallow rectangular channel with moving wall (no curvature).
► Weakening of secondary flow, mixing and dissipated power with increasing Weissenberg number.
► Increasing of secondary flow with angle of helix.