Analysis of Pressure Drop in Extruder Dies

Entrance pressure drop of extruder dies increased with a decrease in the ratio of barrel‐to‐die diameter during the extrusion of corn. For the low Reynolds number flow studied (1.77 x 10 −3 ≤ Re ≤ 9 x 10 −5 ) the viscous component, obtained from Weissberg's analysis, contributed 2% to 40% of the entrance pressure drop and increased as the barrel‐to‐die diameter ratio decreased. The friction factor for laminar fully developed flow through the die followed the expression f = 16/Re'. Fully developed flow within the die was achieved at a die length‐to‐diameter ratio of 9.