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Non-isothermal and Non-Newtonian Flow Analysis for the Non-intermeshing Counter-rotating Twin Screw Extruder Based on FAN Method
•Ÿ‰ªFEKyonsuku Min
Fukuoka, Takamasa / Min Kyonsuku
On the basis of the flow analysis network (FAN) method, a two-dimensional simulation for the non-isothermal flow of non-Newtonian fluid was developed and applied to the flow of polypropylene (PP) melt in a non-intermeshing counter-rotating twin screw extruder. The constitutive model for the PP melt we used was the Cross model with an Arrhenius-type function for temperature dependence. Calculating the movement of fluid particles permitted us to represent not only streamlines themselves but internal residence time profiles in the flow field. Then, the energy equation was able to be successfully solved along the streamlines after replacing it in the convected coordinates.
Taking into accunt back flow and leakage flow, flux fields and streamlines in the flow field clearly showed the difference of conditions between staggered and matched screw flight configurations. The profiles of pressure, shear rate, shear viscosity, temperature and residence time also told us the mechanism of this complicating flow in the extruder. The non-isothermal flow of non-Newtonian fluid in the extruder was differentiated from the isothermal flow of non-Newtonian fluid and the isothermal flow of Newtonian fluid in terms of screw characteristics. The effects of several geometrical and operating conditions, including staggering angle, helix angle of screw flight, screw rotational speed and set temperature, on the screw characteristics were also investigated. Furthermore, some simulated results were compared with experiments using a model twin screw extruder and they demonstrated good agreements in pressure profiles and screw characteristics.
Key words: Twin screw extruder / Non-isothermal flow / Non-Newtonian fluid / Flow analysis network method