CFD-PBM simulation of PET and supercritical CO2 microcellular foaming

By loading Cross model and Oldroyd-B model with User-defined Function (UDF) program, a method to simulate the extrusion flow of viscoelastic non-Newtonian fluid in Fluent software was proposed. In the homogeneous solution of Polyethylene terephthalate (PET) and supercritical CO2, the microscopic bubble growth kinetics model was coupled with the Population Balance Module (PBM), analysis effect of shear rate on bubble nucleation and growth, numerically simulated of the nucleation and growth of bubbles in the extrusion die of PET microcellular foam sheet. Through analysis, the bubble size distribution is more uniform under the condition of 60 degrees template convergence angle. The larger the extrusion speed, the wider the uniform distribution range of bubble density at the outlet position. The initial concentration of CO2 has the greatest impact on the bubble density. Increasing the initial concentration of CO2 can improve the bubble density, but appropriately reducing the initial concentration of CO2 can improve the effective distribution range of bubble density of foam sheet.

Automated summary

A method to simulate the extrusion flow of viscoelastic non-Newtonian fluid was proposed in this study. The effects of shear rate, extrusion speed, and initial concentration of CO2 on bubble nucleation and growth in PET microcellular foam sheet were numerically analyzed. The results showed that the bubble size distribution is more uniform under certain conditions, and the initial concentration of CO2 has the greatest impact on bubble density.