Numerical investigation of continuous mixing of highly viscous, non-Newtonian polymer suspensions by a starved-fed single-screw extruder

Proper mixing of highly viscous, non-Newtonian, multicomponent fluids is complex but essential in industries such as food, catalyst production, and medical device manufacturing. Continuous mixing offers advantages such as more homogeneous products and reduced processing time and energy consumption. One common method for continuous mixing is the use of an extruder. In this study, a computational fluid dynamics model is developed to simulate the mixing of highly viscous, non-Newtonian, multicomponent fluids in a starved-fed single-screw extruder. The material behavior is described using the Herschel-Bulkley model, and the free surface of the material is captured by the volume of fluid method. The mixing performance is evaluated through two parameters: dispersive and distributive mixing. Dispersive mixing is assessed using the well-known Manas-Zloczower mixing index λMZ, while distributive mixing is evaluated through the Kramer mixing index. The more filled extruder yields better results in dispersive mixing, while distributive mixing is more easily achieved with lower percent fill length.