Theoretical and experimental studies of flow behavior in modular nonintermeshing counter-rotating twin screw extruders

Flow and mixing behavior in modular non-intermeshing counter-rotating twin screw extruders were studied both experimentally and theoretically.; A specially designed modular non-intermeshing counter-rotating twin screw extruder having glass windows was built for the experimental studies. The twin screw extruder was operated with either all screw elements or screw-kneading disc elements combinations. Pumping characteristics were compared with various screw configurations. A low density polyethylene was used as a basic material. Comparisons were also made for matched and staggered twin screw extruder and for the single screw extruder made by blocking one barrel of the twin screw extruder.; Flow visualization through the glass windows allowed us to observe melting mechanism and movement of tracers in the twin screw extruder. Two incompatible polymers, low density polyethylene and polycarbonate, were mixed in the twin screw extruder to investigate the effect of screw configurations on the mixing behavior.; In the theoretical part, a new flow model based on hydrodynamic lubrication theory and modified Flow Analysis Network method was developed for both isothermal Newtonian and non-Newtonian fluids in the twin screw extruders. The new model agrees well with the experimental data. The effects of screw configurations and design variables on the extruder performances were determined. Comparisons between the matched and the staggered screw configurations were emphasized.; The contributions of axial leakage flows between two screws to the distributive mixing in non-intermeshing counter-rotating twin screw extruders were described. Mixing coefficient G was introduced as a mixing criterion and interfacial area growth based on this was calculated.; The same numerical approaches were applied to analyze the flow behavior in a Farrel Continuous Mixer.