Rheological Characterization and CFD Simulation of Soy White Flakes Based Dough in a Single Screw Extruder

Understanding the rheological properties such as shear profile, viscosity of a dough inside the extruder is very important for product development, process control, final product quality and scaling up operations. This study aims to characterize the rheological properties of high-protein dough and perform isothermal flow simulation in a complex geometry for generalized Newtonian fluids. The flow of soy white flakes based dough in a single screw extruder was simulated by using computational fluid dynamics. Process conditions considered were screw speeds (40, 80, 120, 160 and 200rpm), barrel temperature (100, 120 and 140C) and soy white flakes contents (30, 40 and 50% db). A mesh superposition technique was used to reduce the geometrical complexity. Simulation results were validated quantitatively by experimental data. The results showed good agreement between experimental and computational results. Moreover, the flow profile in the extruder was analyzed by using the influence of screw speed and level of soy white flakes content. Qualitative behavior of local shear rate and viscosity along the screw are analyzed and comparisons of different process conditions are presented. The results of these simulations can be used to optimize processing conditions and also to improve the product quality of extrudates. Practical ApplicationsThe flow of material within the extruder is complicated due to its helical screw configuration and the different zones of solids-conveying, melting and melts conveying. Shear profile and viscosity of dough within the extruder directly influences the product quality. In the present study, rheological characterization of dough inside the extruder was done by using online capillary die rheometer. The flow of dough during extrusion processing was simulated using computational fluid dynamics. The results of the simulation can be used to optimize the extrusion process influenced by complex flows of relatively high concentration of soy white flakes based dough in an extruder and also to improve the product quality.