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On the two-phase theory of fluidisation

✍ Scribed by M.J. Lockett; J.F. Davidson; D. Harrison

Publisher
Elsevier Science
Year
1967
Tongue
English
Weight
499 KB
Volume
22
Category
Article
ISSN
0009-2509

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✦ Synopsis

Theory is given to predict the value of k in the equation for a bubbling fluidised bed U=kUo+ QB/A; here U is the superficial fluidising velocity, U= U0 at incipient fluidisation, Qn is the observed bubble flow, and A the cross-sectional area of the bed. In the simple two-phase theory, k = 1 ; but the theory herein, assuming constant voidage fraction between the bubbles, shows that for a regular array of bubbles, k = 1 +e~ for a two-dimensional system, provided tb =volume of all bubbles/ bed volume, is small. It is inferred that for a three-dimensional system, k= 1 +2e~.

Thus the simple two-phase theory, though not strictly correct, is not much in error; the error is likely to be largest when U is not much greater than U0, and particularly just above the distributor of a fluidised bed.

πŸ“œ SIMILAR VOLUMES

On the two-phase theory of fluidization
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✍ J.R. Grace; R. Clift πŸ“‚ Article πŸ“… 1974 πŸ› Elsevier Science 🌐 English βš– 786 KB

The distribution of gas flow between bubbles and the dense phase in a fluidized bed is considered. By deriving general equations for gas and solids continuity in a freely-bubbling fluidized bed, the possible contributions to the invisible gas flow are formulated. It is shown that the gross assumptio

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Experimental evidence for the two-phase theory of fluidization-that all the gas in excess of that required for incipient fluidization rises in the bubble phase-is discussed from two viewpoints. Fist, measurements of the volume flow-rate of bubbles in a two-dimensional fluidized bed are compared with

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✍ D.L. Pyle; D. Harrison πŸ“‚ Article πŸ“… 1967 πŸ› Elsevier Science 🌐 English βš– 407 KB

The rising velocity of an isolated bubble in a "two-dimensional" air-fluidised bed has been measured and found to be wel1 described by the relation, ub= 15'9Abf cm/sec, where Ab is the area of the bubble measured in cm\*. This predicts a smaller rising velocity than the corresponding @avies and Tayl