Investigation of transient flow and element analysis in modular intermeshing co-rotating twin screw extruders

Since the mid 1980s, there have been many studies to analyze melt flow in screw and kneading disc block elements of the self-wiping co-rotating twin screw extruder with varying degrees of complexity. Non-Newtonian flow behavior of the special mixing elements is analyzed using cylindrical coordinate hydrodynamic lubrication theory.; A model for flow start-up of a isothermal Newtonian liquid in an initially empty modular self-wiping co-rotating twin screw extruder was developed. The changes of length of fill in front of the die and kneading disc block elements and output flow rate with time were predicted for various modular screw configurations. Experiments were also carried out on a laboratory modular machine with windows to verify the predictions. Generally, good agreement with the flow analysis was found.; A model for non-isothermal Newtonian flow startup in an extruder was developed. A viscous Newtonian fluid was considered to gradually fill a modular co-rotating twin screw extruder with viscous heating and heat transfer to the barrel (and screw). The build up of the axial cup mixing temperature profiles with time was calculated for various modular screw configurations.; A process dynamics model of surging and transient output composition variations in a modular self-wiping twin screw extruder caused by superposed disturbances from feeders was developed. The changes of output flow rate with time(surging) were predicted and the changes of output mass flow rate and weight fraction of additives in the output stream were also predicted for various time dependent input modes such as step function and sinusoidal function inputs into the hopper and other ports part way along the length of the machine.