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Residence time in a single screw free helix extruder using a new solution to the biharmonic equation
Author(s) -
Campbell Gregory A.,
Bomma Sirisha,
St. John Samuel,
Chempath Shaji,
Hunt Diana,
Taylor Ross,
Powers David L.,
Wetzel Mark D.
Publication year - 2021
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.25567
Subject(s) - plastics extrusion , residence time distribution , biharmonic equation , mechanics , materials science , extrusion , residence time (fluid dynamics) , helix (gastropod) , flow (mathematics) , helix angle , displacement (psychology) , composite material , boundary value problem , physics , mathematics , engineering , mathematical analysis , ecology , geotechnical engineering , snail , biology , psychology , psychotherapist
A new analytical solution for the biharmonic equation was developed for single screw extrusion cross‐channel fluid mechanical flow. This analysis led to a quantitative model for residence time distribution when combined with the historic solutions of the drag and pressure flow in the rectangular channel in the single‐screw extruder. The focus of the theoretical and experimental investigation here was to examine how closely the new analytical solution correlated with experimental residence time data for a free‐helix extruder. This new extrusion device was operated as both a conventional extruder and a more positive displacement device by using only helix rotation as the pump. The Moffatt eddies that occur in the quiescent corners of the rectangular channel with screw rotation were found to have a strong effect on the residence time of the extruder. Because there were no quiescent corners for the free‐helix flow there was essentially no residence time tail for this mode of extruder displacement. The theoretical results for a sheet of dye spanning the screw channel width and dye “blobs” were compared with experimental results for both modes of operation. In all cases, the experiments and the theory predictions were essentially consistent.