Numerical simulation of fluid flow and heat transfer in a single‐screw extruder with different dies

Abstract

In a plasticating screw extruder, a polymer melt forms in the melting zone of the extruder. Pressurization of the molten polymer takes place in the melting and the metering sections so that the melt can flow through the restricted passage of the die and assume a desired shape. In a melt fed extruder, the throughput is governed by the pressure rise over the entire length of the extruder. The pressure developed in the screw channel may also be employed in rapid filling of molds, such as those in injection molding. When the geometry of the screw, the barrel temperature, and the die are selected, a unique set of operating parameters arise for a particular flow rate or screw speed. In the present study, numerical and analytical methods are used to calculate the transport in the extruder and the pressure drop in the die. An iterative numerical method based on solving the equations of motion and energy in the screw channel and a correction scheme to couple the die with the screw channel is discussed. The numerical algorithm is capable of handling an arbitrary variation of the viscosity of the polymeric fluid with the shear rate and temperature. The results obtained by simulating the fluid flow in the screw channel are compared with available numerical and experimental results in the literature, indicating good agreement. The performance characteristics of the extruder, for chosen thermal boundary conditions and screw geometry, are presented for different die geometries and different fluids. The important considerations that arise in the numerical simulation of the extrusion process are also discussed.

Residence time and conversion in the extrusion of chemically reactive materials

“…The configumtions and dimensions of dies used in the present work are similar to those considered by Chiruvella et aL (15). For twin-screw extruders, it is assumed that there are two orifices, and therefore, half the throughput flows through each orifice.…”

Transport processes and feasible operating domain in a twin‐screw polymer extruder

“…The distributions of velocity, pressure and temperature in the translation regon are very similar to that in a single-screw extruder, which has been studied extensively in the literature: see, for instance, the work of Karwe and Jaluria (8) and of Chiruvella et al (9,12). Therefore, the more interesting results in a twinscrew extruder are related to the nip region.…”

“…For further details on this modeling, the paper by Chiruvella et al (4) may be consulted. tions are commonly made, as discussed by Karwe and Jaluria (8) and by Chiruvella et aL (9). As the viscosity of the investigated fluids is very high, the inertia terms in the Navier-Stokes equation can be neglected.…”

Melt Conveying in Single-Screw Extruders: Modeling and Simulation

“…Due to the temperature sensitivity of the viscosity, the local temperature change additionally affects the velocity field, which was traditionally assumed to adjust instantaneously to the local temperature field. Two-dimensional thermally developing flows of power-law fluids in infinitely wide screw channels have been solved by many researchers, including Yates [ 56 ], Fenner [ 107 ], Agur and Vlachopolous [ 108 ], Bruker et al [ 109 ], and others [ 110 , 111 , 112 ]. Details on the governing equations and boundary conditions are shown in Table 3 (2D_d).…”