scholarly journals The role of particle-particle interactions in bubbling gas-fluidized beds of Geldart A particles: A discrete particle study

2010 ◽  
Author(s):  
J. W. Wang ◽  
M. A. van der Hoef ◽  
J. A. M. Kuipers ◽  
Liejin Guo ◽  
D. D. Joseph ◽  
...  
Keyword(s):  
Fluidized Beds ◽  
Particle Interactions ◽  
Discrete Particle ◽  
Gas Fluidized Beds

scholarly journals Segregation and intermixing in polydisperse liquid-solid fluidized beds: A multi-fluid model validation study

2021 ◽  
Author(s):  
Shashank S. Tiwari ◽  
Swapnil V. Ghatage ◽  
Jyeshtharaj Joshi ◽  
Bo Kong
Keyword(s):  
Fluidized Beds ◽  
Fluid Model ◽  
Flow Regimes ◽  
Direct Numerical Simulations ◽  
Particle Interactions ◽  
Rational Closure ◽  
Regime Map ◽  
Bed Expansion ◽  
Flow Regime Map

Multifluid model (MFM) simulations have been carried out on liquid-solid fluidized beds (LSFB) consisting of binary and higher-order polydisperse particle mixtures. The role of particle-particle interactions was found to be as crucial as the drag force under laminar and homogenous LSFB flow regimes. The commonly used particle-particle closure models are designed for turbulent and heterogeneous gas-solid flow regimes and thus exhibit limited to no success when implemented for LSFB operating under laminar and homogenous conditions. A need is perceived to carry out Direct Numerical Simulations of liquid-solid flows and extract data from them to develop rational closure terms to account for the physics of LSFB. Finally, a recommendation flow regime map signifying the performance of the MFM has been proposed. This map will act as a potential guideline to identify whether or not the bed expansion characteristics of a given polydisperse LSFB can be correctly simulated using MFM closures tested.

scholarly journals The role of discrete-particle noise in the Ostwald ripening

2005 ◽  
Vol 72 (4) ◽  
pp. 604-610 ◽  
Author(s):  
B Meerson ◽  
L. M Sander ◽  
P Smereka
Keyword(s):  
Ostwald Ripening ◽  
Discrete Particle

Expulsion of particles from a buoyant blob in a fluidized bed

1994 ◽  
Vol 278 ◽  
pp. 63-81 ◽  
Author(s):  
G. K. Batchelor ◽  
J. M. Nitsche
Keyword(s):  
Fluidized Bed ◽  
Fluidized Beds ◽  
Particle Concentration ◽  
Small Concentration ◽  
Numerical Calculations ◽  
Significant Feature ◽  
Average Particle ◽  
Remarkable Property ◽  
Gas Fluidized Beds ◽  
Secondary Instabilities

It is a significant feature of most gas-fluidized beds that they contain rising ‘bubbles’ of almost clear gas. The purpose of this paper is to account plausibly for this remarkable property first by supposing that primary and secondary instabilities of the fluidized bed generate compact regions of above-average or below-average particle concentration, and second by invoking a mechanism for the expulsion of particles from a buoyant compact blob of smaller particle concentration. We postulate that the rising of such an incipient bubble generates a toroidal circulation of the gas in the bubble, roughly like that in a drop of liquid rising through a second liquid of larger density, and that particles in the blob carried round by the fluid move on trajectories which ultimately cross the bubble boundary. Numerical calculations of particle trajectories for practical values of the relevant parameters show that a large percentage of particles, of such small concentration that they move independently, are expelled from a bubble in the time taken by it to rise through a distance of several bubble diameters.Similar calculations for a liquid-fluidized bed show that the expulsion mechanism is much weaker, as a consequence of the larger density and viscosity of a liquid, which is consistent with the absence of observations of relatively empty bubbles in liquid-fluidized beds.It is found to be possible, with the help of the Richardson-Zaki correlation, to adjust the results of these calculations so as to allow approximately for the effect of interaction of particles in a bubble in either a gas- or a liquid-fluidized bed. The interaction of particles at volume fractions of 20 or 30 % lengthens the expulsion times, although without changing the qualitative conclusions.

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