Comparative computational analysis of dispersive mixing in extension‐dominated mixers for single‐screw extruders

Pandey, Vivek; Maia, João M.

doi:10.1002/pen.25478

Cited by 11 publications

(4 citation statements)

References 36 publications

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“…However, for certain materials, such as shear-sensitive ones, shear flow fields can induce excessive shear viscosity heating [7] and damage fibrous components [8], significantly compromising material properties. Research indicates that, under similar stretching or shearing rates, extension-dominated flow mixing exerts twice the maximum force on solid particles compared to shear flow mixing [9][10][11]. Consequently, extension-dominated flow mixing offers higher dispersion efficiency and more effective dispersion effects, albeit with greater difficulty in acquisition and control compared to shear flow fields.…”

Section: Introductionmentioning

confidence: 99%

Kinematics-Based Design Method and Experimental Validation of Internal Meshing Screw for High-Viscosity Fluid Mixing

Guo,

Liu,

Hao

et al. 2024

Applied Sciences

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The challenge of mixing high-viscosity materials is a common issue encountered in the manufacturing process of food materials. The advantages of the internal meshing screw mixer have led to its adoption in various manufacturing processes, but it has yet to be implemented in the food industry. The paper presents a design method for an internal meshing screw mixer based on kinematic principles. The mixer features a helical chamber created by alternating volumes formed by the stator and rotor, establishing an extension-dominated environment for mixing high-viscosity fluids. A kinematic model based on the internal cycloid principle was established, providing trajectories and equations for key points on the rotor, simulating both its rotation and revolution processes, and revealing the velocity variations at different points on the rotor. Based on the kinematic analysis results, a stator and rotor design method was developed according to relevant functional divisions. To achieve the desired motion effects, transmission and support devices were designed, and the relationship between the transmission device and the internal cycloid surface of the fixed rotor was established. The mixer’s application and mixing effectiveness in the food industry were validated using corn syrup and flour. Experimental results showed that the extensional mixer described in the paper effectively mixed high-viscosity fluids while also efficiently blending fine powders. Slurry viscosity was tested with a rheometer at different speeds with an eccentric rotor mixer. Results showed that viscosity decreased with increasing shear rate, with a more pronounced decrease at higher shear rates. The apparent viscosity trend remained consistent at different speeds, although variations were observed at lower shear rates, especially concerning speed. The non-Newtonian fluid index exhibited minimal variations at different speeds, while the consistency coefficient showed significant fluctuations. The mixing uniformity index of the slurry was used to evaluate the mixing uniformity and dispersion uniformity of this extensional mixer. At different rotational speeds, the density of the slurry changes little. The uniformity index of mixing decreases gradually with the increase of rotational speed, reaching its maximum at 15 r/min. The overall trend of the uniformity index decreases with increasing rotational speed, indicating a decrease in density uniformity. A peak appears at 45 r/min, possibly due to the maximum values of elongation rate and shear rate at this speed. As the rotational speed increases, the residence time of the material in the mixer decreases, which may be the main reason for the decrease in mixing uniformity. These findings provide valuable insights into the design and utilization of extension-dominated screw mixers within the food industry, laying a solid foundation for future research and practical applications in this field.

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Section: Introductionmentioning

confidence: 99%

Kinematics-Based Design Method and Experimental Validation of Internal Meshing Screw for High-Viscosity Fluid Mixing

Guo,

Liu,

Hao

et al. 2024

Applied Sciences

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“…One of the pioneers within the field of mixing is Ica Manas-Zlaczower [6][7][8][9][10][11]. Her famous dispersive mixing index from 1992 is still used today [12][13][14][15][16][17], along with her distributive Cluster Distribute Index [12,17,18]. There have not been many alternatives to Zlaczower's dispersive mixing index.…”

Section: Introductionmentioning

confidence: 99%

Numerical Modeling of the Mixing of Highly Viscous Polymer Suspensions in Partially Filled Sigma Blade Mixers

Roland

Ottsen²,

Olofsson

et al. 2023

Polymers

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This paper presents a non-isothermal, non-Newtonian Computational Fluid Dynamics (CFD) model for the mixing of a highly viscous polymer suspension in a partially filled sigma blade mixer. The model accounts for viscous heating and the free surface of the suspension. The rheological model is found by calibration with experimental temperature measurements. Subsequently, the model is exploited to study the effect of applying heat both before and during mixing on the suspension’s mixing quality. Two mixing indexes are used to evaluate the mixing condition, namely, the Ica Manas-Zlaczower dispersive index and Kramer’s distributive index. Some fluctuations are observed in the predictions of the dispersive mixing index, which could be associated with the free surface of the suspension, thus indicating that this index might not be ideal for partially filled mixers. The Kramer index results are stable and indicate that the particles in the suspension can be well distributed. Interestingly, the results highlight that the speed at which the suspension becomes well distributed is almost independent of applying heat both before and during the process.

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“…The experiment results together with the simulation of PS/PMMA blending process proved that the new device was more efficient in dispersing and mixing. Pandey and Maia [21][22][23] introduced hyperbolic flow channels into the mixing elements of extruders to generate extensional flow, and results showed that the extruders with elongational mixing elements were the better dispersive mixer competed with normal extruder mixers.…”

Section: Introductionmentioning

confidence: 99%

A mixing device with phase transition for enhanced exfoliation and dispersion in composites fabrication

Yin

Qian

Jie

et al. 2022

Journal of Reinforced Plastics and Composites

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In this study, a novel mixing device under convergent–divergent elongational flow is developed, mainly contains vane conveying unit and wedge channel unit, generating multi-source pulsating pressure in the mixing procedure to induce phase transition. During the design process, some mathematical works and simulations are conducted to optimize the structural design. High-density polyethylene (HDPE)/expanded graphite (EG) composites are fabricated by phase transition assisted melting mixing. The composites feature lower melt resistance and improved tensile modulus. Furtherly, the prepared HDPE/EG composites exhibit a greater increment of dielectric constant when adding more EG, but always maintain low dielectric loss about 0.05 in low frequency. These results show the excellent exfoliation and dispersion effect, confirming that this new designed equipment and phase transition effect complement each other with fabulous effect in the preparation of filler reinforced polymer.

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Comparative computational analysis of dispersive mixing in extension‐dominated mixers for single‐screw extruders

Cited by 11 publications

References 36 publications

Kinematics-Based Design Method and Experimental Validation of Internal Meshing Screw for High-Viscosity Fluid Mixing

Kinematics-Based Design Method and Experimental Validation of Internal Meshing Screw for High-Viscosity Fluid Mixing

Numerical Modeling of the Mixing of Highly Viscous Polymer Suspensions in Partially Filled Sigma Blade Mixers

A mixing device with phase transition for enhanced exfoliation and dispersion in composites fabrication

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