Influence of extruder geometry on laminar mixing: entropic analysis

Rigorous measures of mixing are needed to optimise processes and equipment design. In this work, the Shannon entropy, a rigorous measure of mixing universally employed across sciences, is used to quantify laminar mixing in an extruder. The classical unwound channel model of a single screw extruder is used in the present study and the influence of extruder geometry on mixing quality is the focus of this work. Three geometries are analysed: a simple single screw extruder, a single screw extruder with ridges placed diagonally on the bottom of the channel and a single screw extruder with pins on the bottom of the channel. The pin geometry is found to be more efficient at mixing than the other two geometries. The influence of scale of observation on the mixing measure is also studied. As the scale of observation decreases, the entropy decreases.