Residence time distribution in a twin screw extruder

Abstract

The residence time distribution (RTD) in a fully intermeshing, corotating twin screw extruder was determined with a stimulus‐response technique. In addition to varying three process parameters (i.e. throughput, screw rotational speed, and barrel temperature), two screw configurations were also studied: one containing four kneading block mixing sections, and the other consisting only of regular screw bushings. Although screw configuration was an important variable, it was found that for both configurations the throughput had the largest effect on RTD. The screw rotational speed was second in importance, and the barrel temperature change produced no effect.A fluid mechanical model based on the fluid flow in a partially‐filled rectangular channel was used to explain the experimentally observed dependence of RTD on the process parameters. Reaction engineering approaches were adopted to compare the RTD results of two screw configurations with two idealized flows.