Incipient fluidization at different temperatures and powder characterization

Saxena, S.C.; Mathur, A.; Zhang, Z. F.

doi:10.1002/aic.690330317

Cited by 10 publications

(2 citation statements)

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“…e transition velocities depend on the operating conditions, physical properties and design parameters. Saxena et al (1987) found that U mf is not in uenced by the bed height and it shi s to somewhat higher values as the temperature increases. Despite the extensive literature (Yerushalmi and Cankurt, 1979;Satija and Fan, 1985;Lancia et al, 1988;Cai et al, 1990;Bi and Fan, 1992;Brereton and Grace, 1992;Chehbouni et al, 1994;Bai et al, 1999;Jung et al, 2005) devoted to ow regime mapping in uidized beds over the past three decades, the ow structures in the various hydrodynamic regimes are still not well understood.…”

Section: Introductionmentioning

confidence: 94%

A New Method for Flow Regime Identification in a Fluidized Bed Based on Gamma-Ray Densitometry and Information Entropy

Nedeltchev

Ahmed

Al‐Dahhan

2012

J. Chem. Eng. Japan / JCEJ

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The accurate identi cation of the boundaries of the main ow regimes in uidized beds is very important since the degrees of mixing and mass and heat transfer depend on the prevailing ow regime. Both the minimum uidization velocity U mf (0.103 m•s 1 ) and the transition velocity U trans (0.12 m•s 1 ) to bubbling uidization regime have been successfully identi ed based on a newly developed maximum information entropy (IE max ) algorithm applied to gamma photon time series. The latter are recorded by means of gamma-ray densitometry scans performed in an air-polyethylene uidized bed (0.438 m in ID) operated at ambient conditions. A comparison with the Kolmogorov entropy (KE) algorithm has found that the new approach yielded more accurate transition velocities. The value of U mf is also validated by means of the pro les of both bed pressure drop and bed height, respectively. It has been found, however, that these parameters are not capable of identifying the second transition velocity U trans . It is demonstrated that the U mf value identi ed on the basis of IE max is theoretically predictable. In the bubbling uidization regime, a simple correlation between both the KE and IE max values is developed.

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