Hydrodynamic characteristics of gas-irregular particle two-phase flow in a bubbling fluidized bed: An experimental and numerical study

He, Yaning; Yan, Shengnan; Wang, Tianyu; Jiang, Baocheng; Huang, Yimin

doi:10.1016/j.powtec.2015.10.012

Cited by 20 publications

(13 citation statements)

References 41 publications

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“…In practice, most of particles used in BFB are nonspherical . To date, the effect of particle shape on bubble dynamics is still not properly addressed as the fluidization dynamics of nonspherical particles is much more complex than spherical particles . Therefore, further quantifying the effect of particle shape on bubble dynamics is required for improving design and operation of BFB.…”

Section: Introductionmentioning

confidence: 99%

“…The former is typically represented by the so‐called two‐fluid model (TFM), where particle‐phase stresses are described by different theories . There have been some studies based on TFM simulations to show that particle shape needs to be considered especially in the drag model . Alternatively, the discrete‐based approach, typically referred to as CFD‐DEM approach, is popular to study fluidization .…”

Section: Introductionmentioning

confidence: 99%

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Bubble dynamics in bubbling fluidized beds of ellipsoidal particles

Shrestha

Kuang

et al. 2019

AIChE Journal

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This article presents a CFD-DEM study on the effect of particle shape on bubble dynamics in bubbling fluidized beds. The particles used are ellipsoids, covering from disk-type to cylinder-type. The phenomena such as bubble coalescence and splitting are successfully generated, and the results are compared with literature, showing a good agreement. The results demonstrate that the bubble forming/rising regions and patterns are influenced significantly by particle shape. Ellipsoidal particles have asymmetrical bubble patterns with two or more circulation vortices while the bubbles for spherical particles form at the bed centerline and rise through the center of the bed. Hence, the vertical mass flux at the bed centerline for spheres is always positive, and ellipsoids have negative or positive vertical mass fluxes. The solid mixing estimated based on the dispersion coefficient revealed poor mixing for ellipsoids. Spherical particles have a larger bubble size and higher bubble rising velocity than ellipsoids.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Bubble dynamics in bubbling fluidized beds of ellipsoidal particles

Shrestha

Kuang

et al. 2019

AIChE Journal

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“…The continuity equations for gas and solid phases are, respectively, given as:

\frac{\partial}{\partial t} (ε_{g} ρ_{g}) + \nabla . (ε_{g} ρ_{g} \overset{true\to}{u_{g}}) = 0,

\frac{\partial}{\partial t} (ε_{s} ρ_{s}) + \nabla . (ε_{s} ρ_{s} \overset{true\to}{u_{s}}) = 0.

…”

Section: Computational Modelmentioning

confidence: 99%

“…Stress tensor of gas and solid phase are defined as:

{\overset{\bar{τ}}{true}}_{g} = ε_{g} μ_{g} [\nabla \overset{true\to}{u_{g}} + {(\nabla \overset{u_{g}}{true})}^{T}] - \frac{2}{3} ε_{g} μ_{g} \nabla . \overset{true\to}{u_{g}} \overset{true¯}{\overset{I}{true}},

{\overset{\bar{τ}}{true}}_{s} = ε_{s} μ_{s} [\nabla \overset{true\to}{u_{s}} + {(\nabla \overset{u_{s}}{true})}^{T}] + ε_{s} true(λ_{s} - \frac{2}{3} μ_{s} true) \nabla . \overset{true\to}{u_{s}} \overset{true¯}{\overset{I}{true}},

…”

Section: Computational Modelmentioning

confidence: 99%

Numerical study of different gas–solid flow regimes effects on hydrodynamics and heat transfer performance of a fluidized bed reactor

Torfeh

Kouhikamali

2019

Heat Trans. Asian Res.

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In this study, a two-fluid Eulerian-Eulerian model has been carried out applying the kinetic theory of granular flow (KTGF) to study the hydrodynamics and heat transfer behavior of a fluidized bed reactor simultaneously. The effects of different gas-solid flow regimes on the operating conditions and heat transfer rate between the hot air and two types of low and high-density inert particles are investigated in a fluidized bed dryer. Different gas-solid flow regimes for wood and glass particles of groups A, B, and D of Geldart's classification are simulated to introduce the most optimal flow regime in terms of heat transfer rate and operating costs. The compromise between the heating rate, the height required for the reactor, and the ratio of the final mass to the initial mass of solid particles, which specifies the need for a cyclone separator showed that the bubbling regime of Geldart B powder for low-density particles and the turbulent regime of Geldart D powder or bubbling regime of Geldart B powder for high-density particles are the optimal operating conditions and flow regimes. Furthermore, it was concluded that the convective heat transfer is the dominant mechanism, which increases with increasing the air velocity and decreasing the particle diameter in each group. K E Y W O R D Sfluidized bed reactor, gas-solid flow regimes, Geldart classification, heat transfer rate, hydrodynamics behavior, operating costs, two-fluid model 1 | INTRODUCTION Fluidized bed reactors have the advantages of superior solid mixing, uniform temperature distribution, high controllability of the bed temperature, good gas-solid contact, and high heat and mass transfer characteristics. These reactors find widespread applications in chemical reactors, coal combustors, and energy industries, including fluid catalytic cracking, combustion, gasification, coating processes, and solids drying. 1,2 High heat transfer rate in fluidized bed reactors is attributed to complex hydrodynamics and heat transfer mechanisms, which depend on the different gas-solid flow regimes in fluidized beds. 3 According to various studies, fluidization can be divided into some main regimes, namely incipient or minimum fluidization, smooth or homogeneous, bubbling, slugging, turbulent, fast and pneumatic transport, depending on the inlet gas velocity, particles characteristics, and the system configuration. 3,4 The relative importance of gas-particle, particle-particle, and wall interactions, which would generally affect the heat transfer between phases through convection and conduction are different in each flow regime. Therefore, it is necessary to identify an appropriate operating regime in industrial processes and applications. 5,6 Figure 1 shows a schematic diagram of the flow regimes in a gas-solid fluidized bed reactor. This figure depicts the bubble formation, solids entrainments, and the spouted behavior in the bed region by increasing the gas velocity beyond the minimum fluidization velocity (U mf ). 7,8 Geldart classified the fluidization characteristics...

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“…In DEM, the particle phase is modelled as a discrete phase and the gas phase as continuous. Several authors have used both TFM and DEM to study bubble dynamics [4][5][6][7][8]. However, most of the previous studies were focused on spherical particles.…”

Section: Introductionmentioning

confidence: 99%

Effect of particle shape on bubble dynamics in bubbling fluidized bed

Shrestha

Zhou

2021

EPJ Web Conf.

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Particle shape can significantly affect the bubble dynamics of bubbling fluidized beds (BFB). In this paper, findings obtained from simulations using CFD-DEM are summarized to discuss the effect of particle shape on bubble dynamics and bubble properties such as bubble size, shape and velocity at a single orifice and uniform fluidized bed. Particles with aspect ratios at 0.5 (oblate), 1 (spherical) and 2 (prolate) are employed to represent disc-like, spherical and rod-like particles, respectively. Both single jet and uniform fluidized bed simulations demonstrate that the bubble forming/rising regions, bubble coalescence locations, and bubble splitting phenomena are significantly influenced by particle shape. The CFD-DEM results for bubble size and bubble velocity show good agreement with literature correlations.

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Hydrodynamic characteristics of gas-irregular particle two-phase flow in a bubbling fluidized bed: An experimental and numerical study

Cited by 20 publications

References 41 publications

Bubble dynamics in bubbling fluidized beds of ellipsoidal particles

Bubble dynamics in bubbling fluidized beds of ellipsoidal particles

Numerical study of different gas–solid flow regimes effects on hydrodynamics and heat transfer performance of a fluidized bed reactor

Effect of particle shape on bubble dynamics in bubbling fluidized bed

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