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Developing methods for design and analysis of continuous mixers through 3D numerical simulation of flow and mixing
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Text
TitleInfo
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Title
Developing methods for design and analysis of continuous mixers through 3D numerical simulation of flow and mixing
Identifier
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http://hdl.rutgers.edu/1782.2/rucore10001600001.ETD.17429
Identifier
ETD_1300
Language
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English
Genre
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theses
Subject
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(authority = RUETD)
Topic
Food Science
Subject
(ID = SBJ-2);
(authority = ETD-LCSH)
Topic
Mixers (Cookery)--Design and construction
Abstract
Design, 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.
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.
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xviii, 190 pages
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Note
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Ph.D.
Note
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Includes bibliographical references (p. 147-152).
Name
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Ashokan
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Bharani Kumar
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Bharani Kumar Ashokan
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Kokini
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Jozef L.
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Jozef L. Kokini
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Karwe
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Mukund V.
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Advisory Committee
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Mukund V. Karwe
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Yam
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Kit L.
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Advisory Committee
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Kit L. Yam
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Marianthi
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outside member
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Advisory Committee
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Marianthi Ierapetritou
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Rutgers University
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Graduate School - New Brunswick
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2008
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2008-10
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NjNbRU
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Title
Graduate School - New Brunswick Electronic Theses and Dissertations
Identifier
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rucore19991600001
Identifier
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doi:10.7282/T3JM29Z9
Genre
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ETD doctoral
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Open
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Bharani Ashokan
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Rutgers University. Graduate School - New Brunswick
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Non-exclusive ETD license
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I hereby grant to the Rutgers University Libraries and to my school the non-exclusive right to archive, reproduce and distribute my thesis or dissertation, in whole or in part, and/or my abstract, in whole or in part, in and from an electronic format, subject to the release date subsequently stipulated in this submittal form and approved by my school. I represent and stipulate that the thesis or dissertation and its abstract are my original work, that they do not infringe or violate any rights of others, and that I make these grants as the sole owner of the rights to my thesis or dissertation and its abstract. I represent that I have obtained written permissions, when necessary, from the owner(s) of each third party copyrighted matter to be included in my thesis or dissertation and will supply copies of such upon request by my school. I acknowledge that RU ETD and my school will not distribute my thesis or dissertation or its abstract if, in their reasonable judgment, they believe all such rights have not been secured. I acknowledge that I retain ownership rights to the copyright of my work. I also retain the right to use all or part of this thesis or dissertation in future works, such as articles or books.
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