Numerical and experimental studies of the flow in the nip region of a partially intermeshing co‐rotating twin‐screw extruder

The flow pattern within a partially intermeshing co‐rotating twin‐screw extruder is three dimensional and extremely complex. In order to simplify the problem, a slice perpendicular to the axis of the twin‐screw extruder has been considered for flow analysis as a two‐dimensional or a quasi‐three‐dimensional problem. The flow in this slice may be considered to consist of a nip region (located between the two screws) and a translation region in which the movement of the material is very similar to the one found in single‐screw extruders. The flow in these two regions have been studied separately. This paper presents the numerical and experimental results of the nip region study. The flow division in the nip region has been quantified and results are presented in terms of a flow division ratio Xf. The flow field patterns have also been obtained. Newtonian as well as non‐Newtonian behavior has been investigated. The influences of such factors as (i) the geometry (the radius of the barrel, radius of the screw, distance between the two screws), (ii) the material properties (the power‐law index for shear rate dependent viscosity), and (iii) processing conditions (the screw speed), have also been studied.