Simulation of mixing in co-rotating twin screw extruders

The emphasis in this 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 colors were used to visualize the deforming phases and compare them with the numerical calculations. To simplify the calculations in the co-rotating twin screw extruder, the flow domain was divided into three regions; region I describes the regular flighted element away from the nip region, II describes the nip area and III describes the region of the staggered kneading blocks. The calculations in the first two regions were done in two dimensional space but the calculations for the kneading blocks were done in the 3-D space. The numerical results presented can be used to optimize screw design and operating conditions