Application of Analytical Technique to Resolving the Flow Dynamics in Self-wiping Co-rotating Twin Screw Extruders

In this paper, a method by which the fluid velocity profile and the net flow rate in self-wiping co-rotating twin screw extruders can be estimated without determining the pressure gradient has been proposed. The method involves using analytical technique to determine the fluid velocity in the local zones of the extruder such as the down channel and axial velocity and subsequently, the net flow rate in the extruder, based on the simplified flow theory for isothermal Newtonian channel flow. It is shown that the velocity distribution is highly dependent on the helix angle, channel height and the ratio of the pressure to drag flow rate. The velocity profile in the down channel direction is shown to have positive values for pressure to drag flow ratio , valid for helix angle , whereas it has both positive and negative values for pressure to drag flow ratio . The reverse is the case for helix angle , with negative values for the pressure to drag flow rate and the presence of backflow, having positive and negative values for pressure to drag flow rate . In the axial direction, the axial velocity is always positive for helix angles between . The purpose of this technique is to aid theoretical estimation of several important parameters in twin screw extruders which are directly or indirectly related to the velocity profile such as the degree of fill in conveying zones, the effective mean residence time, mean time delay and also the residence time distribution, with the goal of avoiding the use empirical method of estimation. The approach has been validated by carrying out experimental investigation.