NUMERICAL STUDY OF TWIN-SCREW EXTRUDERS BY 3-DIMENSIONAL FLOW-ANALYSIS - DEVELOPMENT OF ANALYSIS TECHNIQUE AND EVALUATION OF MIXING PERFORMANCE FOR FULL FLIGHT SCREWS

We have developed a method for predicting the three-dimensional flow f ield in the melt conveying zone in counter-rotating and co-rotating tw in-screw extruders. We applied this technique to the full flight screw s with thin flight width and open C-shaped channels in both rotating t ype extruders having the same screw configurations. We compared the de tails oi velocity and stress fields, the now rates of transportation, and various kinds of leakage flows for both rotating type extruders. A lso, we obtained the spatial distribution of tracer particles and resi dence time distribution using a numerical tracer experiment. The flow rate in the transport direction in the co-rotating twin-screw was larg er than that in the counter-rotating twin-screw, and this suggested th at. the latter has higher transport performance when the screws have: thin flight width and open C-shaped channels as used in this study, As for the distributive mixing, it was found that the co-rotating twin-s crew excels in the area of fluid rearrangement between the two screws and distribution in the rotational direction, while the counter-rotati ng twin-screw has the desirable characteristic of wide distribution in the axial direction. With regard to dispersive mixing, there was no c onsiderable difference between calculated stress fields in both rotati ng; type extruders.