Apparent viscosity measurements in a homogeneous gas-fluidized bed

Colafigli, Alessandro; Mazzei, Luca; Lettieri, Paola; Gibilaro, L.G.

doi:10.1016/j.ces.2008.08.036

Cited by 20 publications

(14 citation statements)

References 25 publications

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“…This regime has been extensively studied experimentally through a number of experimental techniques such as shear testers . The inertial regime, where the kinetic theory is usually adopted, is characterized by instantaneous and binary collisions; such behavior has been widely investigated in various experimental configurations such as fluidized beds . The intermediate regime, which develops between the slow and rapid regimes, has become the subject of numerical and experimental studies.…”

Section: Introductionmentioning

confidence: 99%

“…A different experimental configuration, the coaxial cylinder viscometer, was also used in a number of studies to investigate the particles stress in aerated and fluidized beds . Such a device is commonly used for liquids and consists of a rotating inner cylinder, the so‐called bob, and a static outer cylinder or cup; the material under investigation is placed in the annular gap between the two cylinders.…”

Section: Introductionmentioning

confidence: 99%

“…Both viscosity and yield stress were found to be nearly independent of the diameter of the particles when similar FI was maintained. Similarly, Colafigli et al evaluated the apparent viscosity of silica powders in the Couette FBR (CFBR), where they performed experiments above the minimum fluidization velocity. Their results revealed a pseudoplastic‐type behavior and the apparent viscosities significantly decrease with increasing the shear stress.…”

Section: Introductionmentioning

confidence: 99%

“…The studies discussed show that aerated shearing devices, such as the aerated coaxial cylinder viscometer, have the potentials to shed light on the flow behavior of granular materials in some relevant flow regimes.…”

Section: Introductionmentioning

confidence: 99%

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Development of a virtual Couette rheometer for aerated granular material

et al. 2020

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A novel rheometer to study the behavior of granular materials in an aerated bed of particles has been developed. The device, called the aerated bed virtual Couette rheometer, is shown to be able to measure the shear stresses in the quasi-static and in the intermediate flow regimes. To validate the instrument, a Newtonian fluid of known viscosity was first sheared. The device was then used for measuring the shear stress of nonaerated glass beads with three -3D printed cells of different sizes to validate the optimal radial position, r*, where both shear rate and shear stress are independent of the cell radius. The results for the nonaerated glass beads displayed Coulomb behavior. The same behavior was observed when the bed was aerated.These experiments also showed that for a fixed shear rate the shear stress decreases as the aeration velocity, U. increases. K E Y W O R D Saerated bed, rheology, glass beads, granular materials, inertial number

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Development of a virtual Couette rheometer for aerated granular material

et al. 2020

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“…The formula for calculating the viscosity of percolation fluid is also given [25], but it is difficult to be applied directly because the thickness of the boundary layer and the average viscosity involved in this formula are difficult to be measured. Currently, there are many kinds of conventional viscosity testing methods, which are generally divided into three categories: capillary method [35,36], rotation method [37][38][39], and vibration method [40][41][42][43]. These methods can only measure the viscosity by direct contact with the fluid, and it is impossible to test the viscosity of the fluid in the porous media: that is, the in situ viscosity of fluid in porous media cannot be measured, whereas the in situ viscosity of the fluid in porous media is more capable of characterizing the transport capacity of the fluid, so it is especially necessary to develop the method of testing the in situ viscosity of fluid in porous media.…”

Section: Introductionmentioning

confidence: 99%

A Measured Method for In Situ Viscosity of Fluid in Porous Media by Nuclear Magnetic Resonance

Yang

Luo

et al. 2018

Geofluids

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At present, the existing measuring methods for viscosity of fluid can only obtain the viscosity of bulk fluid, while the in situ viscosity of fluid in porous media cannot be acquired. In this paper, with the combination of nuclear magnetic resonance (NMR) and physical simulation experiment, a testing method for in situ viscosity of fluid in porous media is established, and the in situ viscosity spectra of water in tight cores under different displacement conditions is obtained. The experimental results show that the in situ viscosity distribution of water in porous media is inhomogeneous, and it is not a constant but is related to the distance between water and rock walls. When the distance between fluid and rock walls is close enough (e.g., 2 relaxation time is less than 1 ms), the viscosity of fluid increases rapidly, and the in situ viscosity is greater than the bulk viscosity. Moreover, after the rock samples are saturated with water, the in situ viscosity of water is distributed as a double-peak structure. The left peak is characterized mainly by the in situ viscosity distribution of movable fluid, whose in situ viscosity is smaller, and the right peak mainly represents the in situ viscosity distribution characteristics of immovable fluid, whose in situ viscosity is larger and increases gradually. Under a relatively large driving force, the in situ viscosity amplitude of movable fluid decreases greatly, and the average in situ viscosity of residual water in the core is much higher than that of saturated water in initial state.

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Effective drag on spheres immersed in a fluidized bed at minimum fluidization—Influence of bulk solids properties

et al. 2022

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The aims of this work are to elucidate the effects that bulk solids properties have on the effective drag experienced by large spheres immersed in an emulsion of group-B solids under minimum fluidization conditions and to analyze the ways in which the different suspensions react towards different applied shear rates. To investigate this, magnetic particle tracking was applied to resolve the trajectory of falling-sphere measurements in which the size, density, and sphericity of the bulk solids were varied as well as the size and density of the spherical tracers. The resulting experimental scope included both rising and sinking tracers as well as full segregation and in-bed stagnation of the tracers. The set-up provided highly resolved tracer trajectories, from which the drag experienced by the sphere can be calculated. For sinking tracers, the results showed that an increase in bulk solids size, angularity, and density reduced the terminal velocity of the sphere. This effect correlated well with the bed expansion and Hausner ratio, indicating that a reduced void space among the bulk solids is the main reason for the increase in motion resistance. At lower shear rates, namely, during the de-acceleration towards the stagnant state, beds of larger, more angular, or denser bulk solids yield lower levels of shear stress. The angle of repose of the bulk solids correlated with the rate at which the emulsion thins with increasing shear rate. For rising tracers, shear stress did not show any significant dependency on the properties of the bulk solids.

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Apparent viscosity measurements in a homogeneous gas-fluidized bed

Cited by 20 publications

References 25 publications

Development of a virtual Couette rheometer for aerated granular material

Development of a virtual Couette rheometer for aerated granular material

A Measured Method for In Situ Viscosity of Fluid in Porous Media by Nuclear Magnetic Resonance

Effective drag on spheres immersed in a fluidized bed at minimum fluidization—Influence of bulk solids properties

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