Non-Isothermal Modeling of a Non-Newtonian Fluid Flow in a Twin Screw Extruder Using the Fictitious Domain Method

• Published in: Macromolecular theory and simulations 2013-11, Vol.22 (9), p.462-474
• Main Authors: Sobhani, Hadi, Anderson, Patrick D., Meijer, Han H. E., Ghoreishy, Mir Hamid Reza, Razavi-Nouri, Mohammad
• Format: Article
• Language: English
• Subjects: Computer simulation; Dissipation; fictitious domain method; finite element method; Mathematical analysis; Mathematical models; Melts; non-isothermal; Oscillations; Shear rate; simulation; twin screw extruder; Twin screw extruders
• ISSN: 1022-1344; 1521-3919
• DOI: 10.1002/mats.201300110

In this study, using a developed mathematical model, the non‐isothermal behavior of a non‐Newtonian fluid flow in the conveying elements of an intermeshing co‐rotating twin screw extruder (TSE) is simulated based on the combination of mixed finite elements and fictitious domain methods. The flow equations are solved employing the standard Galerkin method and a streamline‐upwind/Petrov–Galerkin technique is used in the solution scheme of the energy equation to reduce numerical oscillation. This model is combined with the Carreau rheological model to solve governing equations of continuity, momentum, and energy in a 3D Cartesian coordinate system. Using a developed mathematical model, the velocity and pressure fields are simulated for a non‐isothermal flow in a co‐rotating TSE. The shear rate distribution as a criterion for viscous dissipation and also the temperature distribution is calculated based on the simulated flow fields. The applicability of this model is verified by the comparison of experimentally measured pressures and mass flow rates with the simulation results for a high‐density polyethylene melt. This comparison shows a good correlation between experimental data and model predictions. The combination of the fictitious domain method and the finite element method gives rise to a robust scheme for the non‐isothermal simulation of the flow of polymeric melts in co‐rotating twin screw extruders (TSEs). The numerical oscillations of the results are reduced applying the streamline‐upwind/Petrov–Galerkin technique. Using the shear rate distribution, the local viscous dissipation in different regions of TSEs is calculated. Maximum values of the shear rate appear in both the intermeshing region and the screwy tips and therefore, the maximum temperature is observed in these regions.