Local measurements of fluid and particle velocities in a stirred suspension

Guiraud, Pascal; Costes, J.; Bertrand, J.

doi:10.1016/s1385-8947(97)00076-4

Cited by 44 publications

(37 citation statements)

References 14 publications

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“…This supports the fi ndings of Rasmuson (1997 and1998) rather than those of Guiraud et al (1997). However, as also observed by Guiraud et al, large mean slip was also found in the vicinity of the wall, especially close to the bottom of the vessel.…”

Section: Slip Velocitiessupporting

confidence: 90%

“…The difference in fl ow angle between the two phases was rarely found to be more than a few degrees. According to Pettersson and Rasmuson, large particles normally lag relative to the small ones whilst moving upwards, and vice versa, due to the infl uence of gravitation, contrary to the results recorded in Guiraud et al (1997). In contradiction to the fi ndings of Guiraud et al (1991), the largest slip velocities were observed in the impeller discharge, and signifi cant radial and tangential slip velocities were reported.…”

Section: * Author To Whom Correspondence May Be Addressed E-mail Addmentioning

confidence: 72%

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The Two‐Phase Flow in an Axially Stirred Vessel Investigated Using Phase‐Doppler Anemometry

Ljungqvist

Rasmuson

2004

Can J Chem Eng

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The phase‐Doppler technique has been used to characterize the two‐phase flow of liquid and particles in a stirred vessel agitated by a pitched blade turbine. The number of measurement locations used is considerably larger than in previous investigations and the behaviour of four different types of particles is studied. The fluid phase and particle phase flow is studied with particular emphasis on the relative velocities of the two phases. The largest slip velocities in the tank were found just beneath the impeller, and large slip velocities generally coincide with large velocity gradients. Generally, particles lag in relation to the fluid when the fluid flow is directed upwards, and vice versa, but exceptions to this are not unusual.

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Section: Slip Velocitiessupporting

confidence: 90%

Section: * Author To Whom Correspondence May Be Addressed E-mail Addmentioning

confidence: 72%

The Two‐Phase Flow in an Axially Stirred Vessel Investigated Using Phase‐Doppler Anemometry

Ljungqvist

Rasmuson

2004

Can J Chem Eng

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“…The settling velocity in solid suspension is a function of free settling velocity (Guiraud et al, 1997). As per Eq.…”

Section: -1500 MMmentioning

confidence: 99%

Study of solid–liquid mixing in agitated tanks through electrical resistance tomography

Hosseini

Patel

Ein‐Mozaffari

et al. 2010

Chemical Engineering Science

138

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“…Previous investigations have shown that differences in both mean and turbulent velocity were found at specific locations, for example on the impeller disk plane when the Rushton turbine had been employed [17] or in the discharge stream area of an axial flow impeller [16]. The continuous phase radial velocity component was measured, at different axial locations and at r/T ¼ 0.224, in the presence of 0.1 per cent volumetric concentration of solid particles and the results are compared with the corresponding single-phase values in Fig.…”

Section: Preliminary Considerationsmentioning

confidence: 99%

“…Some significant influences due to the presence of particles in solid -liquid mixing vessels have been reported [16,20], but it is still not clear under what conditions turbulence is suppressed or enhanced by the particles. However, the particle size to turbulence length scale has been clearly indicated as a crucial parameter in this respect.…”

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confidence: 99%

Study of fluid velocity characteristics in stirred solid-liquid suspensions with a refractive index matching technique

Micheletti

Yianneskis

2004

Proceedings of the Institution of Mechanical Engineers, Part E:

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A refractive index matching laser Doppler anemometry technique was applied to a solid -liquid suspension in order to measure the continuous phase velocity in the impeller stream of a mixing vessel stirred by a Rushton turbine. Monodispersed, neutrally buoyant and impurity-free particles were used up to 2 per cent volumetric concentration. A significant influence of the dispersed phase on the liquid mean and turbulent flow field was found only near the impeller disk plane, at radial locations close to the blade tip, where both the radial mean and fluctuating velocity components were suppressed by the presence of the solid phase. The fluid velocity variation with angular position was also investigated. A locally high concentration of particles in front of the blades and in the trailing vortices area is suggested as the reason for the modification of the flow observed.Keywords: solid -liquid suspensions, stirred vessels, refractive index matching, laser Doppler anemometryvolumetric concentration d p particle mean diameter, m D impeller diameter, m H liquid height, m I r relative turbulence intensity n index of refraction k turbulence kinetic energy, m 2 /s 2 N impeller rotational speed, min 21 r radial distance from the axis of the vessel, m Re Reynolds number Re p particle Reynolds number [¼(u 2 u p )d p r/m] R ij (Dx i ) correlation of the ith and jth velocity components in two points at a distance Dx i in the ith direction St Stokes number t blade thickness, m t b baffle thickness, m T vessel internal diameter, m temperature, 8C u fluid velocity, m/s u 0 fluid turbulence level, m/s u p particle velocity, m/s v 0 radial turbulence level, m/s V mean radial velocity, m/s V tip impeller tip speed (¼pND), m/s w 0 tangential turbulence level, m/s W mean tangential velocity, m/s z axial distance from the vessel bottom, m Dx i displacement in the ith direction, m 1 kinetic energy viscous dissipation rate, m 2 /s 3 h Kolgomorov length scale, m u tangential coordinate direction, degrees l wavelength, m L ij integral length scale of the ith velocity component in the jth direction, m L m mean integral length scale, m m dynamic viscosity, kg/m s n kinematic viscosity, m 2 /s r liquid density, kg m 3 r p particle density, kg m 3 The MS was Downloaded from t p particle response time, s t h Kolmogorov time scale, s t L radial integral time scale, s w blade angle, degrees (w ¼ 08 in the middle of a reference blade)

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Local measurements of fluid and particle velocities in a stirred suspension

Cited by 44 publications

References 14 publications

The Two‐Phase Flow in an Axially Stirred Vessel Investigated Using Phase‐Doppler Anemometry

The Two‐Phase Flow in an Axially Stirred Vessel Investigated Using Phase‐Doppler Anemometry

Study of solid–liquid mixing in agitated tanks through electrical resistance tomography

Study of fluid velocity characteristics in stirred solid-liquid suspensions with a refractive index matching technique

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