Dispersive prediction of single-screw extruder with mixing head using Boundary Element Method

Abstract : The relationship between the mixing performance in extrusion and the process conditions is of great importance but is never easy to establish. Although experimental prototyping of mixing equipment provides insight into the mixing process, it is too time consuming and cost prohibitive to fully optimize the geometry and the process itself. Alternatively, numerical methods can be used to provide more detailed information on the mixing flows to alleviate the problems with experimental modeling. The Boundary Element Method is an alternative technique which offers the possibility of modeling complex systems since it requires only the discretisation of the model boundaries. In this paper, we examine the use of a Boundary Element Method (BEM) model to predict the dispersive mixing performance of Maddock-like mixing heads on single screw extruders. We use this method to calculate the flow number on the middle plan of the studied geometries and compare it between different conditions of extrusion. The experiments were conducted with a classical Maddock mixing head (in-house design). Two materials were extruded: a polypropylene/ calcium carbonate blend and a polyvinyl chloride/ red pigment blend. The numerical simulations were compared to the observed mixing behavior.