The effects of tank size and impeller type on turbulent flocculation

A basic conceptual and experimental study of the flocculation process is described. The turbulence in three square flocculation reactors of size (6.7in)$\sp3$ ($\approx$5L), 1ft$\sp3$ ($\approx$28L), and (2.7 ft)$\sp3$ ($\approx$560L) with two impeller types (Rushton turbine and A310 fluid foil impeller) were evaluated experimentally using a laser Doppler velocimeter and numerically using a computational fluid dynamic software called FIDAP. The results of both the experimental and numerical characterization of the fluid mechanics in the flocculation basin indicate that when G$\rm\sb{m}$ = constant, the rms turbulent fluctuating velocity was proportional to the impeller tip speed and increased with increasing tank size regardless of impeller type. The fluid mechanics results also indicate that the ratio of the rms fluctuating velocity divided by ND, the tip speed, was higher for the Rushton turbine than for the A310 foil impeller especially in the impeller discharge zone. Furthermore, the rms value in the impeller discharge zone was found to be proportional to N\rm\sb{p} \sp{0.5}ND regardless of tank size and impeller type where N$\rm\sb{p}$ represents the dimensionless impeller power number. \rm N\sb{p} \sp{0.5}ND represents the magnitude of the rms fluctuating velocity in a region where the turbulent flow is anisotropic. These turbulence results suggest that G$\rm\sb{m}$ does not adequately describe the turbulence produced by the Rushton turbine or the A310 foil impeller in the 5L, 28L, and 560L square tanks.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Engineering, Mechanical

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2011

Author dc:creator

• Ducoste, Joel Jean

Contributors dc:contributor

• Clark, Mark M.

• Engineering, Civil
• Engineering, Mechanical
• Engineering, Environmental

Statement dc:rights

• Copyright 1996 Ducoste, Joel Jean

Language dc:language

eng

Identifier

9780591198010
AAI9712261
(UMI)AAI9712261

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/20407