Mixing in stirred tanks influences conversion of reactants for fast reactions, and the efficiency of a mixing process can be determined from
the power consumption and mixing time, which are the two parameters that define homogenization energy. In this study, the computational fluid
dynamics (CFD) and laser Doppler velocimetry (LDV) techniques were employed to study the effect of the Rushton turbine bottom clearance
on the flow field, mixing time and power consumption in a stirred tank. Experimental and simulation studies were conducted in a tank with and
without a draft tube where a conductivity meter and decolourization methods were employed in validating the mixing time simulation results. A
good agreement between the experimental and simulation results for the flow field and mixing time was obtained. The results showed a reduction
in mixing time and power consumption at a low impeller clearance, with reference to the standard clearance, and a further reduction of the same
parameters was obtained for a system fitted with a draft tube. At the low clearance, there was an increase in mixing efficiency by 46%, for a system
without draft tube and 61% for that with the draft tube.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:tut/oai:encore.tut.ac.za:d1000755 |
| Date | 15 August 2006 |
| Creators | Ochieng, A, Onyango, MS |
| Publisher | Elsevier |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Text |
| Format | |
| Rights | Elsevier |
| Relation | Chemical Engineering and Processing |
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