A Unified View of Modeling Flow in Counter-rotating Twin Screw Extruders

Intermeshing counter-rotating twin screw extruders have played an important role in polymer processing technology in the post World War II period. They operate on basically the same principle as low viscosity multiple screw pumps, i.e. they involve forward pumping of fluid contained in C-chambers, which are regions between the screw root and barrel between the interlocked intermeshing regions. Tangential counter-rotating twin screw extruders with open screw channels have also been manufactured in the same period. A new more general model of flow of a Newtonian fluid in a counter-rotating twin screw extruder with partially intermeshing screws is presented. The model allows transition from fully intermeshing to tangential screw machine systems. Calculations are made to show the effect of level of intermesh on pumping capability. Modular counter-rotating twin screw machines are analyzed. The problem of starvation is discussed.