Local shear and skin friction on particles in three-phase fluidized beds
Identifieur interne : 001717 ( Main/Merge ); précédent : 001716; suivant : 001718Local shear and skin friction on particles in three-phase fluidized beds
Auteurs : A. H. Essadki [Maroc] ; I. Nikov [France] ; H. Delmas [France]Source :
- Chemical engineering science [ 0009-2509 ] ; 2005.
Descripteurs français
- Pascal (Inist)
- Wicri :
- topic : Verre, Matière plastique.
English descriptors
- KwdEn :
Abstract
An extension of the electrochemical shear-rate measurement technique is carried out in this work to evaluate the friction force and the shear stress on a particle in two and three phase fluidized beds. Using this technique, the skin friction on a sphere has first been validated for single phase flow. In two- and three-phase fluidized bed, the significance and the direction of the velocity gradient at the wall are discussed. In the case of three phase fluidization, glass spheres (2mm in diameter, ρs = 2532 kg m-3) and plastic spheres (5 mm in diameter, ρs = 1388 kg m-3) were used. This choice provides very different bubbly flows due to different balances of coalescence and break-up of bubbles. The contribution of the frictional force is more important in "coalescent" fluidized beds than in "break-up" fluidized beds. The effect of gas injection is depending on the fluidized particle effect on bubble coalescence and break-up. Correlations have been developed linking frictional force to gas hold-up. The correlations recommended for frictional force in fluidized beds for both systems, (i.e., coalescence and break-up) are as follows: ● Glass spheres (2 mm diameter, coalescence regime): F = 2.43 Re0.052ε0.4g, standard deviation = 6%. ● Plastic spheres (5 mm diameter, break-up regime): F = 0.123 Re0.3ε0.1g, standard deviation = 4%. F is a dimensionless force defined by F = Ff/Pa, where Pa is the effective weight of the sphere. In the case of inverse fluidization, where the solid phase consisted of expanded polystyrene particles 5 mm in diameter (ρs = (350-550) kg m-3), the average frictional force remains almost unaffected by gas injection due to opposite effects on terminal particle velocity and on turbulence.
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Nikov</name><affiliation wicri:level="3"><inist:fA14 i1="02"><s1>ProBioGEM, POLYTECH'Lille, Cité scient@que</s1><s2>59655 Villeneuve d'ASCQ</s2><s3>FRA</s3><sZ>2 aut.</sZ></inist:fA14><country>France</country><placeName><region type="region" nuts="2">Hauts-de-France</region><region type="old region" nuts="2">Nord-Pas-de-Calais</region><settlement type="city">Villeneuve d'ASCQ</settlement></placeName></affiliation></author><author><name sortKey="Delmas, H" sort="Delmas, H" uniqKey="Delmas H" first="H." last="Delmas">H. 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H." last="Essadki">A. H. Essadki</name><affiliation wicri:level="1"><inist:fA14 i1="01"><s1>Ecole Supérieure de Technologie de Casablanca, B.P. 8012</s1><s2>Oasis, Casablanca</s2><s3>MAR</s3><sZ>1 aut.</sZ></inist:fA14><country>Maroc</country><wicri:noRegion>Oasis, Casablanca</wicri:noRegion></affiliation></author><author><name sortKey="Nikov, I" sort="Nikov, I" uniqKey="Nikov I" first="I." last="Nikov">I. Nikov</name><affiliation wicri:level="3"><inist:fA14 i1="02"><s1>ProBioGEM, POLYTECH'Lille, Cité scient@que</s1><s2>59655 Villeneuve d'ASCQ</s2><s3>FRA</s3><sZ>2 aut.</sZ></inist:fA14><country>France</country><placeName><region type="region" nuts="2">Hauts-de-France</region><region type="old region" nuts="2">Nord-Pas-de-Calais</region><settlement type="city">Villeneuve d'ASCQ</settlement></placeName></affiliation></author><author><name sortKey="Delmas, H" sort="Delmas, H" uniqKey="Delmas H" first="H." last="Delmas">H. Delmas</name><affiliation wicri:level="3"><inist:fA14 i1="03"><s1>Laboratoire de Génie Chimique, ENSIACET-INPT, 5 rue Paulin Talabot</s1><s2>31106 Toulouse</s2><s3>FRA</s3><sZ>3 aut.</sZ></inist:fA14><country>France</country><placeName><region type="region" nuts="2">Occitanie (région administrative)</region><region type="old region" nuts="2">Midi-Pyrénées</region><settlement type="city">Toulouse</settlement></placeName></affiliation></author></analytic><series><title level="j" type="main">Chemical engineering science</title><title level="j" type="abbreviated">Chem. eng. sci.</title><idno type="ISSN">0009-2509</idno><imprint><date when="2005">2005</date></imprint></series></biblStruct></sourceDesc><seriesStmt><title level="j" type="main">Chemical engineering science</title><title level="j" type="abbreviated">Chem. eng. sci.</title><idno type="ISSN">0009-2509</idno></seriesStmt></fileDesc><profileDesc><textClass><keywords scheme="KwdEn" xml:lang="en"><term>Bubble</term><term>Bubble flow</term><term>Coalescence</term><term>Correlation</term><term>Correlation analysis</term><term>Fluidization</term><term>Fluidized bed</term><term>Friction</term><term>Gas holdup</term><term>Gas injection</term><term>Glass</term><term>Hydrodynamics</term><term>Measurement method</term><term>Plastics</term><term>Shear</term><term>Shear stress</term><term>Turbulence</term></keywords><keywords scheme="Pascal" xml:lang="fr"><term>Cisaillement</term><term>Frottement</term><term>Fluidisation</term><term>Lit fluidisé</term><term>Méthode mesure</term><term>Contrainte cisaillement</term><term>Verre</term><term>Matière plastique</term><term>Ecoulement bulle</term><term>Coalescence</term><term>Bulle</term><term>Injection gaz</term><term>Corrélation</term><term>Analyse corrélation</term><term>Retenue gaz</term><term>Hydrodynamique</term><term>Turbulence</term></keywords><keywords scheme="Wicri" type="topic" xml:lang="fr"><term>Verre</term><term>Matière plastique</term></keywords></textClass></profileDesc></teiHeader><front><div type="abstract" xml:lang="en">An extension of the electrochemical shear-rate measurement technique is carried out in this work to evaluate the friction force and the shear stress on a particle in two and three phase fluidized beds. Using this technique, the skin friction on a sphere has first been validated for single phase flow. In two- and three-phase fluidized bed, the significance and the direction of the velocity gradient at the wall are discussed. In the case of three phase fluidization, glass spheres (2mm in diameter, ρ<sub>s</sub> = 2532 kg m<sup>-3</sup>) and plastic spheres (5 mm in diameter, ρ<sub>s</sub> = 1388 kg m<sup>-3</sup>) were used. This choice provides very different bubbly flows due to different balances of coalescence and break-up of bubbles. The contribution of the frictional force is more important in "coalescent" fluidized beds than in "break-up" fluidized beds. The effect of gas injection is depending on the fluidized particle effect on bubble coalescence and break-up. Correlations have been developed linking frictional force to gas hold-up. The correlations recommended for frictional force in fluidized beds for both systems, (i.e., coalescence and break-up) are as follows: ● Glass spheres (2 mm diameter, coalescence regime): F = 2.43 Re<sup>0.052</sup>ε<sup>0.4</sup><sub>g</sub>, standard deviation = 6%. ● Plastic spheres (5 mm diameter, break-up regime): F = 0.123 Re<sup>0.3</sup>ε<sup>0.1</sup><sub>g</sub>, standard deviation = 4%. F is a dimensionless force defined by F = F<sub>f</sub>/P<sub>a</sub>, where Pa is the effective weight of the sphere. In the case of inverse fluidization, where the solid phase consisted of expanded polystyrene particles 5 mm in diameter (ρ<sub>s</sub> = (350-550) kg m<sup>-3</sup>), the average frictional force remains almost unaffected by gas injection due to opposite effects on terminal particle velocity and on turbulence.</div></front></TEI><affiliations><list><country><li>France</li><li>Maroc</li></country><region><li>Hauts-de-France</li><li>Midi-Pyrénées</li><li>Nord-Pas-de-Calais</li><li>Occitanie (région administrative)</li></region><settlement><li>Toulouse</li><li>Villeneuve d'ASCQ</li></settlement></list><tree><country name="Maroc"><noRegion><name sortKey="Essadki, A H" sort="Essadki, A H" uniqKey="Essadki A" first="A. H." last="Essadki">A. H. Essadki</name></noRegion></country><country name="France"><region name="Hauts-de-France"><name sortKey="Nikov, I" sort="Nikov, I" uniqKey="Nikov I" first="I." last="Nikov">I. Nikov</name></region><name sortKey="Delmas, H" sort="Delmas, H" uniqKey="Delmas H" first="H." last="Delmas">H. Delmas</name></country></tree></affiliations></record>Pour manipuler ce document sous Unix (Dilib)
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