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Mustafa Seker - One of the best experts on this subject based on the ideXlab platform.
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residence time distributions of starch with high moisture content in a Single Screw Extruder
Journal of Food Engineering, 2005Co-Authors: Mustafa SekerAbstract:Starch was extruded with sodium trimetaphosphate and sodium hydroxide in a Single-Screw Extruder with a mixing element at 28.5%, 35.5%, and 41.2% moisture content (wet basis) and 90, 140 and 190 rpm Screw speeds. The effects of moisture content of starch on mean residence time, spread of residence time distribution curve, and flow pattern were determined at three Screw speeds. Increasing the Screw speed reduced mean residence time at the moisture contents between 28.5% and 41.2%. Increasing the moisture content from 28.5% to 41.2% did not significantly affect the mean residence time. The spread of residence time distribution curve was reduced as Screw speed was increased, but was not affected as moisture content was increased from 28.5% to 41.2%. The flow pattern was between plug flow and mixed flow. Two flow models were used to represent the flow pattern in the Extruder. The parameters of each model were determined by a nonlinear regression, and the fitness of experimental data to the flow models was examined.
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Distribution of the residence time in a Single-Screw Extruder with differing numbers of mixing elements
International Journal of Food Science and Technology, 2004Co-Authors: Mustafa SekerAbstract:Summary Starch was extruded with sodium trimetaphosphate and sodium hydroxide in a Single-Screw Extruder at 40% moisture content and Screw speeds of 90 and 140 r.p.m. The effect of Screw configurations, which included one and two mixing elements, on mean residence time, spread of residence time distribution (RTD), and flow pattern were determined. Increasing the Screw speed and reducing the number of mixing elements reduced mean residence time. Higher RTD spread values were obtained at a Screw speed of 90 r.p.m. when compared with 140 r.p.m. and increasing the number of mixing elements in the Screw increased the RTD spread. The flow pattern was between plug and mixed flow, and increasing the number of a mixing element in the Screw did not significantly affect the flow pattern in the Single-Screw Extruder.
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PROPERTIES of CROSS‐LINKED STARCH PRODUCED IN A Single Screw Extruder WITH and WITHOUT A MIXING ELEMENT
Journal of Food Process Engineering, 2004Co-Authors: Mustafa Seker, H. Saddikoglu, Milford A. HannaAbstract:Starch was extruded with sodium hydroxide and sodium trimetaphosphate in order to cross-link it in a Single-Screw Extruder with and without a mixing element at constant Screw speed of 90 rpm in the first set of experiments and at similar mean residence time controlled by Screw speed in the second set of experiments. For the Screw without mixing element in the second set of experiments, Screw speed was adjusted to give the similar residence time as the Single-Screw Extruder with mixing element at 220 rpm. Phosphorus content and pasting curves of extrudates showed that starch was cross-linked during extrusion. Replacing the Screw without mixing element by the Screw with mixing element increased specific mechanical energy dissipation into starch, but there was not significant difference between water solubility and absorption indices of starch cross-linked in the Single-Screw Extruder with and without the mixing element at constant Screw speed in the first set of experiments and at similar mean residence time in the second set of experiments.
Mukund V Karwe - One of the best experts on this subject based on the ideXlab platform.
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numerical simulation of the extrusion process for food materials in a Single Screw Extruder
Journal of Food Engineering, 1996Co-Authors: Raman V. Chiruvella, Yogesh Jaluria, Mukund V KarweAbstract:Abstract A numerical study of extrusion cooking of starch based materials in a Single-Screw Extruder is carried out. The low moisture levels and high temperatures typically encountered in practical circumstances are considered. The starch conversion process is studied in the rheological region of the Extruder which is often the last few turns of the Screw, where the material is treated as a non-Newtonian fluid. A numerical method based on finite-difference approximation is employed to solve the governing non-linear equations for momentum, energy and mass conservation for a non-Newtonian fluid undergoing physicochemical changes. The initial conditions for the problem are taken from experimental observations. The Screw configuration and the operating parameters, such as barrel temperature, Screw speed and throughput, are varied to study their influence on the conversion of starch. It is found that 28% conversion is obtained due to viscous dissipation alone, whereas 61% conversion occurs by raising the barrel temperature by about 25 °C above the inlet. It is also observed that, at any Screw speed, a smaller flow rate caused by a smaller die diameter leads to a higher degree of conversion. Furthermore, it is found that the compression ratio of the Screw has a significant influence on pressure rise, bulk temperature and average residence time. As the compression ratio increases the temperature increases but the residence time decreases. The former effect increases the degree of conversion where as the latter decreases the degree of conversion. Therefore there exists a compression ratio at which a minimum degree of conversion at the die is obtained.
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numerical simulation of fluid flow and heat transfer in a Single Screw Extruder for non newtonian fluids
Numerical Heat Transfer Part A-applications, 1990Co-Authors: Mukund V Karwe, Yogesh JaluriaAbstract:Thermal transport within the channel of a Single-Screw Extruder has been studied numerically for non-Newtonian fluids, the computations art carried out for a given barrel temperature distribution and adiabatic Screw. Numerical results are obtained using finite-difference techniques. The results indicate that the temperature variation in the downstream direction has a small effect on the corresponding velocity field, which is determined mainly by the total volume flow rate. It is also found that heat may be transferred from the flowing material to the barrel farther downstream under certain conditions. The residence time distribution is obtained numerically. Screw characteristics are presented in terms of bulk temperature rise versus Screw speed
Yogesh Jaluria - One of the best experts on this subject based on the ideXlab platform.
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numerical simulation of the extrusion process for food materials in a Single Screw Extruder
Journal of Food Engineering, 1996Co-Authors: Raman V. Chiruvella, Yogesh Jaluria, Mukund V KarweAbstract:Abstract A numerical study of extrusion cooking of starch based materials in a Single-Screw Extruder is carried out. The low moisture levels and high temperatures typically encountered in practical circumstances are considered. The starch conversion process is studied in the rheological region of the Extruder which is often the last few turns of the Screw, where the material is treated as a non-Newtonian fluid. A numerical method based on finite-difference approximation is employed to solve the governing non-linear equations for momentum, energy and mass conservation for a non-Newtonian fluid undergoing physicochemical changes. The initial conditions for the problem are taken from experimental observations. The Screw configuration and the operating parameters, such as barrel temperature, Screw speed and throughput, are varied to study their influence on the conversion of starch. It is found that 28% conversion is obtained due to viscous dissipation alone, whereas 61% conversion occurs by raising the barrel temperature by about 25 °C above the inlet. It is also observed that, at any Screw speed, a smaller flow rate caused by a smaller die diameter leads to a higher degree of conversion. Furthermore, it is found that the compression ratio of the Screw has a significant influence on pressure rise, bulk temperature and average residence time. As the compression ratio increases the temperature increases but the residence time decreases. The former effect increases the degree of conversion where as the latter decreases the degree of conversion. Therefore there exists a compression ratio at which a minimum degree of conversion at the die is obtained.
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extrusion of non newtonian fluids in a Single Screw Extruder with pressure back flow
Polymer Engineering and Science, 1996Co-Authors: Raman V. Chiruvella, Yogesh Jaluria, V Sernas, Moez EsseghirAbstract:The transport phenomena underlying the extrusion of non-Newtonian fluids in Single-Screw Extruders is investigated numerically and experimentally. The viscosity of the investigated fluids is a strong function of the temperature and, for the non-Newtonian case, of the shear rate. Therefore, the governing equations of motion are coupled to the energy equation through the viscosity. The velocity in the down channel direction of the Screw Extruder is a result of both shear and pressure driven transport. The pressure acts in a direction opposite to that of the drag flow, and comparatively high pressures arise at the die in typical Extruders. When a narrow die is used in the Screw Extruder, the pressure gradient in the down-channel direction becomes so large that the down-channel velocity near the Screw root becomes negative in terms of the coordinate system fixed to the Screw. The conventional marching schemes fail to simulate the fluid flow when the down-channel velocity becomes negative, since the downstream conditions are not known. Two different numerical schemes used to simulate the fluid flow in a Single-Screw Extruder for this circumstance, which often arises when dies with high flow resistance are used and which is termed as pressure back flow in the literature, have been discussed. One scheme is based on including the down-channel thermal diffusion, making the problem elliptic, and the other scheme uses a different coordinate system. Both formulations are found to yield results that are fairly close. Experiments were also carried out to measure the pressures at three different locations in a Single-Screw Extruder. The computed results were found to be in good agreement with the experimental results. The pressures at the die obtained numerically by treating the flow as isothermal are found to be lower than those obtained when the flow is treated as nonisothermal, indicating the strong influence of thermal transport in this problem.
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numerical simulation of fluid flow and heat transfer in a Single Screw Extruder for non newtonian fluids
Numerical Heat Transfer Part A-applications, 1990Co-Authors: Mukund V Karwe, Yogesh JaluriaAbstract:Thermal transport within the channel of a Single-Screw Extruder has been studied numerically for non-Newtonian fluids, the computations art carried out for a given barrel temperature distribution and adiabatic Screw. Numerical results are obtained using finite-difference techniques. The results indicate that the temperature variation in the downstream direction has a small effect on the corresponding velocity field, which is determined mainly by the total volume flow rate. It is also found that heat may be transferred from the flowing material to the barrel farther downstream under certain conditions. The residence time distribution is obtained numerically. Screw characteristics are presented in terms of bulk temperature rise versus Screw speed
José A. Covas - One of the best experts on this subject based on the ideXlab platform.
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the influence of pellet barrel friction on the granular transport in a Single Screw Extruder
Powder Technology, 2014Co-Authors: O P Michelangelli, A Gasparcunha, José A. CovasAbstract:Abstract The flow of individual polymer pellets along the solids conveying zone of a Single Screw Extruder is studied by means of a numerical model based on the discrete element method (DEM). The effect of the pellet–barrel friction coefficient (μ p–b ) is discussed in terms of mass output, volume fraction, residence time distribution and velocity profiles. Model predictions are compared with experimental data, showing a good match, and with calculations using traditional analyses by assuming the movement of an elastic solid plug. As μ p–b is increased, three regimes with distinct behavior were identified. For up to μ p–b = 0.25 (this value coinciding with that of the pellet–Screw friction coefficient), particle collisions drive the granular transport. For higher values, friction determines the conveying efficiency, but when μ p–b > 2.00 a plug-type behavior is anticipated.
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Laboratory modular instrumented Single Screw Extruder for optimisation of polymer processing
Plastics Rubber and Composites, 2012Co-Authors: António Gaspar-cunha, Olga S. Carneiro, S. M. Cunha, José A. CovasAbstract:A laboratory fully modular instrumented Single Screw Extruder designed to gather information on the development along its axis of temperature, mixing, chemical conversion and/or morphology development of a given material is presented. Some of its capabilities are utilised to study the effect of operating conditions and of Screw geometry, including conventional versus barrier profiles, on the evolution of the plasticating sequence of a low density polyethylene. Melting of an immiscible polymer blend (polyamide 6/polypropylene) is also investigated and a specific melting mechanism is proposed.
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Dynamics of Filler Size and Spatial Distribution in a Plasticating Single Screw Extruder – Modeling and Experimental Observations
International Polymer Processing, 2010Co-Authors: N. Domingues, José A. Covas, Marco Camesasca, Miron Kaufman, António Gaspar-cunha, Ica Manas-zloczowerAbstract:A model of agglomerate break-up, incorporating both rupture and erosion, is employed to predict the dynamics of filler size distribution in a plasticating Single Screw Extruder. Filler spatial distribution along the Extruder length was also ascertained and direct comparison of experimental and computational data proved to be satisfactory. The method was also used to investigate the effect of material properties, operating conditions and Extruder geometry on the dynamics of agglomerate dispersion along a Single Screw Extruder. Generally, dispersion levels were primarily governed by the magnitude of the hydrodynamic stresses developed in the Extruder and the residence time in the melt.
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Computational and Experimental Study of Mixing in a Single Screw Extruder
AIP Conference Proceedings, 2007Co-Authors: N. Domingues, António Gaspar-cunha, José A. CovasAbstract:This work reports a computational and experimental effort to quantify (distributive and dispersive) mixing in a Single Screw Extruder. This is done by considering the presence of solid‐liquid or liquid‐liquid systems and following changes in the average size of the disperse phase along the channel. The experiments are performed in a prototype modular Extruder that allows changes in Screw geometry and quick extraction of the Screw from the barrel, thus yielding helical samples of material along the Screw channel that can be subsequently analysed in terms of morphology (number, size and distribution of droplets / solids). The results are confronted with numerical predictions along the metering section of the Screw, good agreement being found.
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A COMPUTATIONAL INVESTIGATION ON THE EFFECT OF POLYMER RHEOLOGY ON THE PERFORMANCE OF A Single Screw Extruder
2001Co-Authors: José A. Covas, António Gaspar-cunhaAbstract:This work investigates the influence of the rheological characteristics of a polymer on the (predicted) performance of a typical Single Screw Extruder. A global modelling package is developed in order to yield important process responses such as axial pressure, melting rate, melt temperature, power consumption and degree of mixing. The effect of the power law constants is studied both in terms of the general process behaviour and of the sensitivity of the Extruder to small changes of the input conditions.
Kurt A Rosentrater - One of the best experts on this subject based on the ideXlab platform.
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Functional and Biochemical Alterations of Fish Meal, Soybean Meal, and Distillers Dried Grains with Solubles as Affected by a Single-Screw Extruder
Food and Bioprocess Technology, 2016Co-Authors: Parisa Fallahi, Kasiviswanathan Muthukumarappan, Kurt A RosentraterAbstract:The goal of this study was to investigate the effect of extrusion-forced structural changes on the extent of functional and biochemical changes of three selected protein sources that are predominantly used in aquafeed, i.e., fish meal (FM), soybean meal (SBM), and distillers dried grains with solubles (DDGS). The samples were individually extruded in a Single-Screw Extruder using a factorial design with replicated central composite points at a temperature of 80, 110, and 140 °C; Screw speed of 80, 150, and 220 rpm; and moisture content of 150, 225, and 300 (g/kg). Extrusion temperature and feed moisture significantly affected the nitrogen solubility in water (NSI), sodium dodecyl sulfate, and 2-mercaptoethanol solvents. Screw speed had only a minor effect on this value ( P
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functional and structural properties of corn potato and cassava starches as affected by a Single Screw Extruder
International Journal of Food Properties, 2016Co-Authors: Parisa Fallahi, Kasiviswanathan Muthukumarappan, Kurt A RosentraterAbstract:The aim of this study was to identify suitable starch sources that can improve the structural integrity of plant protein-based extruded feeds, specifically aquatic feeds. Extrusion trials were performed, using a Single-Screw Extruder. Extruder temperature, Screw speed, and moisture content were varied in a factorial design with a replicated central composite point. The effects of these variables on functional and structural properties of the extrudates were evaluated. Temperature had the dominant effect on all properties. Increasing Extruder temperature resulted in notable increases in onset temperature of gelatinization and glass transition temperature of all extrudates. The lowest water absorption, alkaline viscosity, and the highest water solubility, in addition to the lowest Rapid Visco Analyzer profile were found for corn starch extrudates. The lowest thermal stability was observed for the potato extrudate. It is expected that cassava and potato starches can contribute better in the formation of a co...
