Computation of residence time and energy distributions in the reverse screw element of a twin-screw extrusion-cooker

Abstract The isothermal flow of a Newtonian material through the reverse screw element (RSE) of a twin-screw extrusion-cooker was computed. The distribution of a tracer, whose units were incremented in time and energy along their trajectories, was simulated. This resulted in residence time and energy distributions. Both distributions are important in order to quantify the treatment received by the food material during the flow through the RSE and therefore the corresponding level of transformation. The influence of several variables (screw speed, feed rate, geometry) was evaluated. The width of the axial slots was shown to be very efficient in regulating the mechanical treatment of the material.