Three-Dimensional Thermohydrodynamic Modeling of Carbohydrate–Protein Feed Extrusion: Effects of Screw Speed and Radial Clearance in a Co-Rotating Twin-Screw Extruder
Abstract
Three-Dimensional Thermohydrodynamic Modeling of Carbohydrate–Protein Feed Extrusion: Effects of Screw Speed and Radial Clearance in a Co-Rotating Twin-Screw Extruder
Abstract
Co-rotating twin-screw extrusion is used to process carbohydrate–protein blends for aquaculture feeds. Viscous dissipation in the screw intermeshing zone can generate local temperature peaks that expose heat-sensitive proteins to thermal degradation. This study develops a coupled three-dimensional thermohydrodynamic model of non-Newtonian flow and energy transport in the intermeshing zone of a 32-mm extruder. A modified Arrhenius–Ostwald power-law model describes apparent viscosity as a function of local shear rate and temperature. The governing equations are solved using the finite element method on a refined unstructured mesh.
The simulations indicated that up to 75% of the total mechanical energy was dissipated in the intermeshing clearance, where local shear rates reached 1,200 s⁻¹. At 200 rpm, the predicted peak temperature was 408 K (135 °C), a condition identified as favorable for starch gelatinization while limiting thermal exposure of proteins. At speeds above 300 rpm, predicted hot spots reached 458 K (185 °C), indicating a risk of amino acid degradation. Increasing the radial clearance from 0.5 to 0.7 mm reduced the maximum shear rate by 15–18% and moderated the temperature field.
The maximum reported deviation between model predictions and experimental measurements was below 7.4%. The model can support the selection of screw speed and radial clearance to manage local heating during aquaculture feed extrusion.
Keywords — Co-rotating twin-screw extrusion, aquaculture feed, thermohydrodynamic modeling, viscous dissipation, screw speed, radial clearance, finite element method.
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References
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