TitleDeveloping methods for design and analysis of continuous mixers through 3D numerical simulation of flow and mixing
NameAshokan, Bharani Kumar (author), Kokini, Jozef L. (chair), Karwe, Mukund V. (internal member), Yam, Kit L. (internal member), Ierapetritou, Marianthi (outside member), Rutgers University, Graduate School - New Brunswick,
Mixers (Cookery)--Design and construction
DescriptionDesign, scale up and selection of alternative geometries for dough mixers in order to achieve a well mixed final product with consistent rheological character is a major challenge in the food industry. The objective of this work is to develop methods to formulate design rules for continuous mixers and identify continuous mixer geometries with similar mixing performance as a model batch mixer using 3D numerical simulations.
FEM simulations were performed with Polyflow (Fluent Inc.) which uses a mixed Galerkin formulation of the isothermal governing equations of motion and continuity. 3D continuous mixer geometries that simulate a 2" Readco Twin Screw mixer with three different paddle configurations were developed and flow profiles and mixing efficiencies were predicted. Accurate predictions of the flow profiles in a continuous mixer were attained by optimizing the FEM mesh, flow geometry and operating conditions through convergence analysis of velocity and pressure. The predictions were validated with favorable comparisons to experimentally observed velocities that demonstrated the accuracy of the predicted velocities increased with increasing length of mixer geometry, showing the importance of considering the axial flow in a continuous.
Using the calculated flow profiles, trajectories for material points with random initial positions were calculated to predict mixing efficiencies. Segregation scale, mean logarithm of stretching, mean instantaneous efficiency and time averaged efficiency, along with the shear rates and mixing index were used to evaluate mixing. The forward conveying paddle configuration provided the best mixing efficiency when compared to neutral and reverse conveying paddle arrangements and the continuous mixer was also shown to be significantly better than a batch mixer for the same time of operation. Existing numerical techniques that can solve flow problems with moving objects in the flow domain cannot simulate the flow of viscoelastic materials. New techniques were evaluated in this research to simulate the flow and mixing of viscoelastic materials in the twin screw mixing geometry.
NoteIncludes bibliographical references (p. 147-152).
CollectionGraduate School - New Brunswick Electronic Theses and Dissertations
RightsThe author owns the copyright to this work.