Abstract
The field of simulation and optimisation of dynamic mixing elements (‘mixers’) is lacking good methods for spatially resolved validation and flow visualisation. For this reason, the authors present an experimental setup that gives better insight into the thermal, distributive and dispersive mixing process by measuring melt temperatures upstream of the mixer and injecting a secondary, visually distinguishable stream of melt upstream. Running extrusion trials for a polyethylene on both a rhomboidal and a Maddock mixer, temperatures, gray scale distribution of images of extrudates and size of dispersed domains in incompatible polystyrene were measured. It was found that temperatures upstream and downstream of the mixer can be quantified. This was used to validate a simulation of thermal mixing. In distributive mixing, good agreement with simulation and an excellent spatial resolution were observed, thereby identifying an area of the rhomboidal mixer in need of geometric improvement. For dispersive mixing, a trend coherent with extrusion theory was found.
Highlights
The authors give an overview of single-screw extrusion, the mixing element for single-screw extrusion and simulative optimisation of these mixing elements
Multiple researchers from IKT in Stuttgart are known to work on several fields related to the design of mixing elements: They use simulation technology to analyse the influence of rheological behaviour on mixing [36]
The size of polystyrene the first material was expected to blend with the primary flow of melt, the polystyrene was domains is an excellent indicator of dispersive mixing
Summary
Other recent work by Moritzer and Wittke compares numerous diamond-type, cylinder-type and ‘anticlockwise’ mixing elements in a simulation driven by the finite volume method [26] Both distributive and dispersive mixing are considered, but thermal mixing is neglected. Multiple researchers from IKT in Stuttgart (most notably Celik, Erb and Bonten) are known to work on several fields related to the design of mixing elements: They use simulation technology to analyse the influence of rheological behaviour on mixing [36] They investigate varying methods to determine criteria for the both interpretation of simulation [37,38] and extrudate photography data [39]. 2. Materials and Methods resolution and, should make it possible to correlate simulation and experiment data at single operating point.2,Itthe should alsopresent removethe the material necessityand to analyse mixers several. The authors will attempt to validate this hypothesis by means of comparing simulation data to results from with both ‘classical’ and spatially resolved interpretations
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