Transport characteristics of suspensions: Part VI. Minimum transport velocity for large particle size suspensions in round horizontal pipes
✍ Scribed by David G. Thomas
- Publisher
- American Institute of Chemical Engineers
- Year
- 1962
- Tongue
- English
- Weight
- 786 KB
- Volume
- 8
- Category
- Article
- ISSN
- 0001-1541
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✦ Synopsis
Abstract
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) vas determined in a 1‐in. pipe for an aqueous suspension of glass beads using glass beads having mean diameters of 78 and 310 μ.
The results of the present study were combined with prior pneumatic‐ and hydraulic‐transport data for air and water suspensions to give a unique minimum‐transport relation, valid for particles larger than the thickness of the laminar sublayer, that is for particles which are immersed in the buffer layer or which extend into the turbulent core when resting on the pipe wall. The correlation showed that the ratio of particle settling velocity to friction velocity at the minimum transport condition was a function of particle Reynolds number, pipe Reynolds number, and the relative density ratio of particle to fluid. The results of the correlation suggest that a single mechanism is responsible for the initiation of particle transport throughout the range of conditions covered. This mechanism may be identified with Bernoulli forces due to instantaneous velocity differences accompanying turbulent fluctuations and largely confined to the buffer layer.