Determining local residence time distributions in twin-screw extruder elements via smoothed particle hydrodynamics

Complex flow patterns in twin-screw extruder (TSE) elements lead to a variability in residence times in the equipment. Changes in the Residence Time Distribution (RTD) depend on the processing conditions and can have a major impact on the product quality. While the RTDs of entire TSE processes can easily be determined via experiment, local RTDs (LRTDs) in sections of fully filled zones are difficult to measure experimentally. In this work, we propose an alternative in-silico method based on Smoothed Particle Hydrodynamics (SPH). We simulated five geometrically different screw elements and investigated how their local RTDs varied with the screw speed, throughput and screw length. Furthermore, in-silico tracer experiments provided insights into the underlying flow mechanisms and the resulting RTDs. Good agreement with experimental results confirms the validity of our approach.