Effect of impellers configuration on the gas dispersion of high-viscosity fluid using Narrow Annular Gap Unit. Part 2: numerical approach

Mardaru, Anamaria; Souidi, Kaies; Marcati, Alain; Jinescu, Gheorghiţa; Habchi, Charbel; Valle, Dominique Della; Djelveh, Gholamreza

doi:10.1016/j.ces.2012.02.056

Cited by 11 publications

(7 citation statements)

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“…Any gap between two successive elements (δ = 0) shifted at angle θ = 30° (Figure 1(b)). Such configuration permitted to assure dispersive and distributive aspects of gas dispersion within continuous phases [11,12]. The jacketed column was thermally regulated (4°C) using cooling fluid connected to a WKL 600 cryothermostat (LAUDA GmbH, Germany).…”

Section: Experimental Set-up For Batch and Continuousmentioning

confidence: 99%

“…When aligned configuration was used, the gas phase followed liquid paths within the column; however, the shifted impeller generates a venture effect and enhances gas dispersion through the liquid phase. More details on the effect of impeller design with experimental and numerical approaches are given in Souidi et al [11,12]. The present work is aimed at performing the foaming of CS solution alone and with addition of hydroxyapatite (HAp) and/or tetraethyl orthosilicate (TEOS) under steady-state flow conditions using optimum configuration of impellers [11,12].…”

Section: Introductionmentioning

confidence: 99%

“…More details on the effect of impeller design with experimental and numerical approaches are given in Souidi et al [11,12]. The present work is aimed at performing the foaming of CS solution alone and with addition of hydroxyapatite (HAp) and/or tetraethyl orthosilicate (TEOS) under steady-state flow conditions using optimum configuration of impellers [11,12]. The influence of operating conditions-gas/liquid flow rates-on the density and porosity of the final porous biomaterial (scaffold) was investigated.…”

Section: Introductionmentioning

confidence: 99%

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Comparison Study between Batch and Continuous Processes to Obtain Chitosan-Based High Porous Biomaterial for Biological Applications

Ursu

Furtuna

Requia

et al. 2019

International Journal of Polymer Science

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Foaming process can be monitored under batch or continuous flows conditions. In the batch process, foaming is time-dependent and the foaming efficiency is controlled by the operator. On the other hand, in the continuous process, the foaming efficiency is only monitored by gas and liquid flow rates. The aim of this work is to compare the two technologies to perform porous scaffold biomaterial based on chitosan (a biocompatible polysaccharide) as well as calcium (Ca2+) and silica (SiO2) (two osteogenesis compounds). Diverse recipes using chitosan (CS) solution (2% (w/v)) in acetic acid (1% (v/v in distilled water)) mixed with whey protein isolate (WPI) (2% (w/v)) as natural surfactant were studied. They were supplemented or not by hydroxyapatite powder (HAp) and tetraethyl orthosilicate (TEOS). A jacketed narrow annular gap unit (NAGU) was used to perform the continuous foaming process. For all experimentations, the mixture flow rate was maintained at 30 mL min-1. The influence of operating conditions such as gas and liquid flow rates was studied to obtain foams and final scaffold material with different densities and porosities. Some other recipes followed foaming under batch conditions. Generally, the recipes were placed in a vessel under mixing allowing the gas phase to come from the roof of the vessel. In this case, it becomes very difficult to control the density and the size distribution of bubbles in the final product. In both cases, liquid foams were analysed (density, bubble size distribution) and then freeze-dried for mechanical and porosity investigations using the dynamic mechanical analysis (DMA) system and scanning electron microscopy (SEM). It has been shown that the controlled injected gas affected the continuous phase, resulting in a lighter and higher porous structure, a more homogeneous appearance, and a more uniform distribution of osteogenesis components compared to one obtained using batch operation. The obtained porous materials exhibited good properties (porosity, interconnectivity, and good HAp and silica distribution) and potential for future bone regeneration applications.

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Section: Experimental Set-up For Batch and Continuousmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Comparison Study between Batch and Continuous Processes to Obtain Chitosan-Based High Porous Biomaterial for Biological Applications

Ursu

Furtuna

Requia

et al. 2019

International Journal of Polymer Science

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“…Numerical simulations based on Computational Fluid Dynamics (CFD) also share some of these difficulties, especially under turbulent flow conditions because turbulence in a narrow gap is not accurately described by the standard k‐ε model used commonly for turbulence modelling. Under laminar conditions, CFD can however provide qualitative useful information on the comparison of mixer geometry (see, e.g., Mardaru et al) . It constitutes, therefore, a useful tool that could also be used quantitatively for design purpose, but remains time‐consuming and requires experienced users.…”

Section: Introductionmentioning

confidence: 99%

CFD simulation of flow and mixing in‐inline rotor‐stator mixers with complex fluids

2014

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The objective is to apply CFD methodology for the validation of the scale‐up of rotor‐stator units formed by flat blades and used as in‐line mixers under laminar flow conditions. The comparison between simulated and experimental data as a function of rotor geometry, rotation speed and flow rate has shown a good agreement in terms of power input and RTD curves both for Newtonian and power‐law fluids with a flow index between 0.2 and 1. The applicability of the virtual Couette analogy has been validated quantitatively and explained by the analysis of the local flow in the mixer. As a result, a shear coefficient independent of fluid rheology has been deduced from CFD data. This has been shown to depend only on the dimensionless gap when the length‐to‐diameter ratio is higher than 2.5. In this case, fast 2D simulations can provide a good approximation of the shear coefficient obtained from 3D calculations from which a master power curve can be deduced, but these are not able to predict flow transition, contrary to 3D computations. Finally, original correlations able to estimate the power and shear coefficients as a function of the mixer geometry have been established.

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“…CFD can be used to model multi impeller systems, e.g. gas dispersers and biochemical reactors [3]. The effect of impeller and baffle configurations on gas dispersion can be evaluated and the optimal structure of the disperser can be determined.…”

Section: Introductionmentioning

confidence: 99%

CFD Based Qualification of Mixing Efficiency of Stirred Vessels

Till

Molnár²,

Egedy

et al. 2018

Period. Polytech. Chem. Eng.

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In this work, we focus on the most crucial units in a chemical technology, the chemical reactors. Using a commercially available CFD software package, COMSOL Multiphysics, 3D mathematical models of a batch reactor with different impeller geometries have been investigated. The reasonable agreement between the experimental and simulation results indicates the validity of the developed CFD model. The effect of the impeller design, e. g. number of blades on the mixing efficiency is evaluated based on the simulation studies.The proposed measure to determine the energy efficiency of mixing (i. e. mixing index) is based on the calculated velocity field and energy usage. The information about the homogeneity of the mixed phase in the system can be extracted from the developed velocity field. Hence, we proposed histograms of velocity fluctuations on a logarithmic scale as an efficient tool to measure the achieved homogeneity of the phase in case of different impellers and rotational speeds. IntroductionDuring the last few decades, computational fluid dynamics (CFD) method has become a very powerful tool in the process industry primarily to analyse the hydrodynamic behavior. In general, CFD methods rely on the numerical solution of the Navier-Stokes equations, thus flow velocity, velocity magnitudes, and pressure values can be calculated in the geometric space investigated. A particularly significant benefit of the CFD simulators is that they can include entire apparatuses in three dimensions, regarding either single phase or multiphase systems [1,2]. This property of the CFD simulators makes them useful in a large number of research areas, including the study of mixing phenomena. Fluid mixing is a fundamental operation in the chemical process industry and the stirred tank or autoclave is a commonly used reactor type in many kinds of chemical technologies; therefore these systems are well described. Regardless, when it comes to design work, simple experimental correlations are still commonly used, e.g. Reynolds number, Froude number, power number or the Euler number which is derived from the previous ones. This approach has its limitations when it comes to the design of stirred vessels with complex internal structure.

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Effect of impellers configuration on the gas dispersion of high-viscosity fluid using Narrow Annular Gap Unit. Part 2: numerical approach

Cited by 11 publications

References 11 publications

Comparison Study between Batch and Continuous Processes to Obtain Chitosan-Based High Porous Biomaterial for Biological Applications

Comparison Study between Batch and Continuous Processes to Obtain Chitosan-Based High Porous Biomaterial for Biological Applications

CFD simulation of flow and mixing in‐inline rotor‐stator mixers with complex fluids

CFD Based Qualification of Mixing Efficiency of Stirred Vessels

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