Simulation of pipe extrusion : cooling and annealing

When plastic pipe is extruded, it emerges from an annular die and passes through a sizing sleeve to set its outer diameter. The pipe is then solidified in a cooling tank by spraying the outer surface with cold water. The final pipe properties depend on cooling and annealing process.

The objective of the present research is to develop an improved process model for cooling and annealing of the extruded plastic pipe with a better understanding of polymer crystallization and polymer physics underlying the extrusion behavior.

To accomplish that version 6.04 of FIDAP finite element method has been used. We need to predict temperature profile and crystallinity distribution for polypropylene. We consider the axi- symmetric, steady-state problem with Newtonian behavior and plug flow with no rheology. We also assume only axial velocity because the pipe is not rotating nor is pipe thickness changing.

The mathematical model, includes energy equation for heat transfer and Nakamura's equation for the crystallization kinetics. We use a very sophisticated numerical method to predict crystallinity distribution and adjustment of the operation conditions. In this method we should use large number of iterations to get the convergence and let the solver solve the iv equations until the difference between two guesses become less than the tolerance.