On-line rheology, flow simulation and system-based modelling of twin-screw extrusion processing of corn meal
Mirza, Iqbal A.
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Permalink
https://hdl.handle.net/2142/23661
Description
Title
On-line rheology, flow simulation and system-based modelling of twin-screw extrusion processing of corn meal
Author(s)
Mirza, Iqbal A.
Issue Date
1991
Doctoral Committee Chair(s)
Villota, Ricardo
Department of Study
Agriculture, Food Science and Technology
Engineering, Agricultural
Engineering, Chemical
Discipline
Agriculture, Food Science and Technology
Engineering, Agricultural
Engineering, Chemical
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Agriculture, Food Science and Technology
Engineering, Agricultural
Engineering, Chemical
Language
eng
Abstract
Rheological characterization of corn meal formulations was carried out using a twin screw extruder as a rheometer. On-line rheometrical techniques used for rheological characterization of non-food polymers were modified to make them adaptable to food materials extruded in a twin-screw extruder. The experimentally obtained pressure drop data was transformed into rheological parameters and was fitted to known rheological models (e.g. Power-law model). Furthermore, the effects of temperature and moisture content were incorporated to arrive at a more comprehensive rheological model.
Objective Driven Modelling and Simulation (ODMS) methodology was applied to carry out computer simulations of flow through extrusion dies. The rheological model parameters obtained from online rheometry was used along with fluid flow models for flow simulation. A fluid dynamic analysis program (FIDAP) was utilized for flow simulation studies. The simulation experiments were carried out on both simple capillary dies and more complex mandrel geometries.
The rheological parameters obtained from on-line rheological experiments along with the system parameters (mechanical and thermal energy input) were employed as a bridge between the influencing and influenced parameters of the extrusion process. The influencing parameters (operating variables of the extrusion process) were correlated via design of experiments and regression techniques to the system parameters and rheological parameters of the food melt. The system parameters (specific mechanical energy and product temperature) were correlated to the functional properties and morphology of the extruded product. This approach allows the prediction of product characteristics from the knowledge of system parameters or if the product characteristics are known, the system parameters can be determined. The knowledge of system parameters permits the selection of operating environment needed to attain the desired product characteristics.
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