A Visualization of Flow Patterns of Viscoelastic Fluid Partially Filled in a Co‐Rotating Nontwin Screw Extruder

A novel type of co‐rotating nontwin screw geometry is presented in this paper. The left and right screw elements have a speed ratio of 2. In order to investigate the flow pattern and mixing mechanism in the channels of such two screws, a visualization prototype with a global transparent barrel was developed. A kind of colored sodium carboxymethyl cellulose solution was prepared and used as a tracer viscoelastic fluid. Four cameras were used to capture the instantaneous images during processing. A relationship model of the axial fill length and the fill degree of fluid was established. This is the first time that the flow patterns of a viscoelastic fluid partially filled in nontwin screw elements has been captured. An asymmetry phenomenon was found in the intermeshing region and another region far from it. It was also found that material dams experienced elongation in the single‐tip screw channel, and local pile‐ups of conveyed fluid were located at the top and bottom intermeshing regions. POLYM. ENG. SCI., 59:E24–E32, 2019. © 2018 Society of Plastics Engineers