Bubble eruption diameter in a fluidized bed of large particles at elevated temperatures

1981 ◽  
Vol 36 (7) ◽  
pp. 1259-1260 ◽  
Author(s):  
Norkun Sitthiphong ◽  
Alan H. George ◽  
Dwight Bushnell
Keyword(s):  
Fluidized Bed ◽  
Elevated Temperatures ◽  
Large Particles

The Pressure Drop at Critical Fluidization of Large Particles in Vibrated Fluidization Bed

2012 ◽  
Vol 550-553 ◽  
pp. 2763-2766
Author(s):  
Xue Jun Zhu ◽  
Jun Deng
Keyword(s):  
Pressure Drop ◽  
Fluidized Bed ◽  
Large Particle ◽  
Particle Diameter ◽  
Future Design ◽  
Vibration Strength ◽  
Bed Height ◽  
Large Particles ◽  
Vibrated Fluidized Bed ◽  
Critical Fluidization

The pressure drop at critical fluidization for two-dimensional vibrated fluidized bed(240 mm×80 mm) was studied, with large particle glass beads of average diameters dp of 1.8mm, 2.5mm and 3.2mm.The effect of the vibration strength, the static bed height and the particle diameter on the pressure drop was analyzed. The results of the study show that the pressure drop decreases with the increase of the vibration strength. It plays an even more prominent part with decreases of the static bed height and the particle diameter. The empirical correlation equations to predict the pressure drop was established, and the results of the prediction was compared with the experimental data, the error is in range of ±10%. The results can provide references for future design and research on the vibrated fluidized bed.

Failure at Elevated Temperatures: Influence of Dynamic Restoration

2008 ◽  
Vol 604-605 ◽  
pp. 285-329 ◽  
Author(s):  
H.J. McQueen
Keyword(s):  
Pore Formation ◽  
Elevated Temperatures ◽  
Dynamic Recovery ◽  
Failure Mechanisms ◽  
Vacancy Diffusion ◽  
Triple Junctions ◽  
Stress Concentrations ◽  
Large Particles ◽  
Wedge Crack ◽  
Reducing Stress

Inherent failure mechanisms at elevated temperature are primarily wedge crack growth at triple junctions arising from differential grain boundary (GB) sliding at higher stresses and pore formation on sliding boundaries due to vacancy diffusion at lower stresses and higher T. The behaviours of these mechanisms have been ascertained in creep where they can be studied over long periods. They continue to operate in hot working although their effects per unit strain have been reduced by decrease in fractional contribution of GB sliding. Dynamic recovery (DRV) significantly develops a stable substructure that strongly mitigates stress concentration. In alloys of austenitic steel, Ni and Cu, dynamic recrystallization (DRX) aids DRV in reducing stress concentrations and the migrating GB isolate fissures so they cannot propagate. Solutes and precipitates generally reduce ductility by diminishing DRV and DRX. Large particles and inclusions, notably on GB, introduce new sources of fissure nucleation, lowering ductility; solidification segregation and low melting constituents, especially if they spread along the GB, create severe problems.

The dynamics of large particles in a four-compartment interconnected fluidized bed

1999 ◽  
Vol 101 (3) ◽  
pp. 229-239 ◽  
Author(s):  
F.F. Snieders ◽  
A.C. Hoffmann ◽  
D. Cheesman ◽  
J.G. Yates ◽  
M. Stein ◽  
...  
Keyword(s):  
Fluidized Bed ◽  
Large Particles

MATHEMATICAL MODELLING OF SIMULTANEOUS HEAT AND MASS TRANSFER IN FLUIDIZED BED DRYING OF LARGE PARTICLES

1999 ◽  
Vol 23 (1B) ◽  
pp. 129-145 ◽  
Author(s):  
E. Hajidavaloo ◽  
F. Hamdullahpur
Keyword(s):  
Mass Transfer ◽  
Partial Differential Equations ◽  
Differential Equations ◽  
Heat And Mass Transfer ◽  
Fluidized Bed ◽  
Solid Phase ◽  
Variable Mass ◽  
Partial Differential ◽  
Large Particles ◽  
Fluidized Bed Drying

A mathematical model for simulation of simultaneous unsteady heat and mass transfer in fluidized-bed drying of large particles is proposed. A set of coupled non-linear partial differential equations is employed to accurately model the process without using adjustable parameters. A three phase model representing a bubble (dilute) phase, interstitial gas phase and a solid phase is used to describe the thermal and hydrodynamic characteristics of the bed. The bubble and temperature distributions inside the solid phase is applied. The flow field is divided by an orthogonal grid to a finite number of control volumes to simulate the variation of the properties for the three phases in longitudinal direction. The Crank-Nicholson implicit numerical method is applied to solve the set of coupled nonlinear partial differential equations with variable mass and thermal diffusivity for a spherical-shape particle. A pilot-scaled fluidized bed dryer was built to test the results of proposed model with those obtained by experiments using wheat particles as a bed charge. A good agreement between the numerical and experimental results is observed.

Effect of gas extraction on the hydrodynamics in a fluidized bed membrane reactor at elevated temperatures

2019 ◽  
Vol 14 (4) ◽  
Author(s):  
Yao Xiao ◽  
Chenxi Bai ◽  
Yumin Chen ◽  
Weijie Yan ◽  
Jizhi Du ◽  
...  
Keyword(s):  
Fluidized Bed ◽  
Membrane Reactor ◽  
Elevated Temperatures ◽  
Gas Extraction
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