Abstract
The aim of this study was to gain some fundamental insight in the dynamics of the flow during mixing in a twin screw extruder. The major difficulty in this specific problem is connected to the geometry of the flow domain in the extruder and the solution of the flow problem. In general, one can separate this flow domain into two parts: the flow in the regular flighted elements and the flow between the kneading disks. The flow in the regular flighted elements can in turn be divided into the region away from the nip region and the flow at the nip region. The flow away from the nip region is very similar to the one in a single screw extruder. Near the nip, however, the shear rates are much higher, as the fluid now experiences the flow field between two rotating screws with double relative linear velocities and very small clearances. Finally there are no valid assumptions to simplify the flow in the kneading disks region and calculations have to be carried out in the real domain. The emphasis in the present work is on the study of the mechanisms that drive the mixing process in the twin screw extruder. Stress profiles, particle paths, streamlines and accumulated energy are the quantities that are monitored as an indication of the progress of mixing. Tracer studies of materials pigmented with different colours were used to visualize the deforming phases and compare them with the numerical calculations. (from paper.)
Original language | English |
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Journal | [No source information available] |
State | Published - 1989 |