Dense-phase velocity fluctuation in a 2-D fluidized bed

Sánchez-Delgado, S.; Marugán-Cruz, C.; Acosta-Iborra, A.; Santana, D.

doi:10.1016/j.powtec.2010.02.005

Cited by 35 publications

(26 citation statements)

References 18 publications

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“…frequencies greater to 10 4 Hz) have been reported for conventional FB of Geldart B particles beyond the on set of bubbling [33]. In fact, bubble rise in conventional FB pushes upwards and downwards the particles within a region close to each bubble, the size of this region being of order of the bubble diameter [34]. The fluctuation induced by bubbles on the particle velocity has a characteristic frequency that can be roughly esti mated dividing the bubble velocity by the size of the perturbed area f b % 0:…”

Section: Transformed Two Fluid Model Equationsmentioning

confidence: 95%

A novel methodology for simulating vibrated fluidized beds using two-fluid models

Acosta-Iborra

Hernández-Jiménez

Vega

et al. 2012

Chemical Engineering Journal

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Section: Transformed Two Fluid Model Equationsmentioning

confidence: 95%

A novel methodology for simulating vibrated fluidized beds using two-fluid models

Acosta-Iborra

Hernández-Jiménez

Vega

et al. 2012

Chemical Engineering Journal

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“…In addition, the authors provide time averaged solids concentration maps for a subset of the test matrix. To the best of our knowledge, this is the only study that provides circulation times in bubbling fluidized beds by means of PIV and DIA, and further details on the experimental setup are offered in [24,29].…”

Section: Simulation Setupmentioning

confidence: 99%

3D Eulerian modeling of thin rectangular gas–solid fluidized beds: Estimation of the specularity coefficient and its effects on bubbling dynamics and circulation times

2015

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This study aims at investigating the influence of the wall boundary conditions and specifically the specularity coefficient on the fluidization behavior of a thin rectangular fluidized bed by means of 3D numerical simulation employing an Eulerian description of the gas and the solid phases. Thin rectangular fluidized beds have been extensively used in the research literature since it is assumed that the flow behaves like a simpler twodimensional flow and hence they offer validation data for 2D simulations. However, the effects of the front and the back walls are significant, influencing the sensitivity of the fluidization hydrodynamics to the third dimension whose consideration is thus necessary. In order to investigate the influence of the specularity coefficient, φ (a parameter controlling the momentum transfer from the particles to the wall), on the fluidization hydrodynamics, a parametric analysis is conducted and the response of the bubble dynamics, reflecting the gas motion, and the circulation fluxes, displaying the solids motion, are examined in detail. The computational results are compared with available experimental data in order to determine the values of φ that lead to the accurate description of the fluidization hydrodynamics via a two-fold validation strategy which involves the calculation of the circulation time and the solids concentration maps. It is observed that the appropriate value of the specularity coefficient depends rather strongly on the superficial gas velocity of the bed.

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“…The experimental facility used for the comparison of the computational data is a two dimensional cold fluidized bed of dimensions 0.5 m Â 2 m Â 0.005 m (width W, height h, and thick ness Z) (Sá nchez Delgado et al, 2010). Fig.…”

Section: Experimental Facility and Data Acquisitionmentioning

confidence: 99%

“…The particular implementation of the technique is also explained in Sánchez Delgado et al (2010), and is based on the correlation of consecutive in time images using the multigrid PIV code MATPIV (Sveen, 1998(Sveen, 2007. Interrogation windows of 16 Â 16 pixels with 0.5 overlap were typically used in this PIV analysis performed to compute the velocity field of the dense phase.…”

Section: Experimental Facility and Data Acquisitionmentioning

confidence: 99%

“…With the development of CCD cameras and Particle Image Velocimetry (PIV) or other velocimetry techniques, there are several studies showing experimental information on particle velocity in very thin, fluidized beds, whose behaviour can be considered two or quasi two dimensional (e.g. Bokkers et al, 2004;Liu et al, 2005;Santana et al, 2005;Almendros Ibá ñ ez et al, 2006;Laverman et al, 2008;Sá nchez Delgado et al, 2010). At this regard, reported mean particle velocities are clearly smaller than the characteristic bubble velocity in two dimen sional beds working with Geldart B particles and superficial velocity around 2 times the minimum fluidisation velocity U mf .…”

Section: Introductionmentioning

confidence: 99%

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Comparison between two-fluid model simulations and particle image analysis & velocimetry (PIV) results for a two-dimensional gas–solid fluidized bed

Hernández-Jiménez

Sánchez-Delgado

Gómez-García

et al. 2011

Chemical Engineering Science

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109

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a b s t r a c tThis work compares simulation and experimental results of the hydrodynamics of a two dimensional, bubbling air fluidized bed. The simulation in this study has been conducted using an Eulerian Eulerian two fluid approach based on two different and well known closure models for the gas particle interaction: the drag models due to Gidaspow and Syamlal & O'Brien. The experimental results have been obtained by means of Digital Image Analysis (DIA) and Particle Image Velocimetry (PIV) techniques applied on a real bubbling fluidized bed of 0.005 m thickness to ensure its two dimensional behaviour. Several results have been obtained in this work from both simulation and experiments and mutually compared. Previous studies in literature devoted to the comparison between two fluid models and experiments are usually focused on bubble behaviour (i.e. bubble velocity and diameter) and dense phase distribution. However, the present work examines and compares not only the bubble hydrodynamics and dense phase probability within the bed, but also the time averaged vertical and horizontal component of the dense phase velocity, the air throughflow and the instantaneous interaction between bubbles and dense phase. Besides, quantitative comparison of the time averaged dense phase probability as well as the velocity profiles at various distances from the distributor has been undertaken in this study by means of the definition of a discrepancy factor, which accounts for the quadratic difference between simulation and experiments The resulting comparison shows and acceptable resemblance between simulation and experiments for dense phase probability, and good agreement for bubble diameter and velocity in two dimensional beds, which is in harmony with other previous studies. However, regarding the time averaged velocity of the dense phase, the present study clearly reveals that simulation and experiments only agree qualitatively in the two dimensional bed tested, the vertical component of the simulated dense phase velocity being nearly an order of magnitude larger than the one obtained from the PIV experiments. This discrepancy increases with the height above the distributor of the two dimensional bed, and it is even larger for the horizontal component of the time averaged dense phase velocity. In other words, the results presented in this work indicate that the fine agreement commonly encountered between simulated and real beds on bubble hydrodynamics is not a sufficient condition to ensure that the dense phase velocity obtained with two fluid models is similar to that from experimental measurements on two dimensional beds.

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Dense-phase velocity fluctuation in a 2-D fluidized bed

Cited by 35 publications

References 18 publications

A novel methodology for simulating vibrated fluidized beds using two-fluid models

A novel methodology for simulating vibrated fluidized beds using two-fluid models

3D Eulerian modeling of thin rectangular gas–solid fluidized beds: Estimation of the specularity coefficient and its effects on bubbling dynamics and circulation times

Comparison between two-fluid model simulations and particle image analysis & velocimetry (PIV) results for a two-dimensional gas–solid fluidized bed

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