Investigation of Bubble Growth in Extrusion Expansion of Cornstarch with CFD Method

Abstract

The bubble growth in the extrusion expansion of cornstarch was studied with computational fluid dynamic (CFD) method. The effects of initial temperature, initial moisture content and viscoelasticity on the changes of bubble radius, forces, and temperature during the first 4 seconds of expansion were investigated. WLF equation was employed for the description of viscoelasticity of starch melt during expansion. It was showed that the higher the initial temperature, the higher the expansion ratio. The maximum expansion ratio was achieved when the initial moisture content was 20%.