ISSN:
0001-1541
Keywords:
Chemistry
;
Chemical Engineering
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Process Engineering, Biotechnology, Nutrition Technology
Notes:
The minimum transport velocity (defined as the mean stream velocity required to prevent the accumulation of a layer of stationary or sliding particles on the bottom of a horizontal conduit) has been determined for flocculated thorium oxide and kaolin suspensions flowing in glass pipes. The pipes ranged from 1 to 4 in. in diameter, and the concentration was varied from 0.01 to 0.17 volume fraction solids.Two flow regimes were observed depending on the concentration of the suspension. In the first the suspension was sufficiently concentrated to be in the compaction zone and hence had an extremely low settling rate. The second regime was observed with more dilute suspensions which were in the hindered-settling zone and settled ten to one-hundred times faster than slurries which were in compaction. The concentration for transition from one regime to the other was dependent on both the tube diameter and the degree of flocculation. The suspension particles were smaller than the thickness of the laminar sublayer, and they settled according to Stokes' law for the particular conditions of this study. Under these circumstances the relation developed for dilute suspensions is consistent with particle transfer in the radial direction owing to Bernoulli forces on the particle and the action of turbulent fluctuations which penetrate the laminar sublayer. For concentrated suspension in compaction the minimum transport velocity was given by a characteristic critical Reynolds number.
Additional Material:
8 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/aic.690070316
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