ITEMS

modern scholarly publishers in the finest tradition

	Search

ICHMT DIGITAL LIBRARY ONLINE

ISSN 961-91393-0-5

Individual price:

$246.00 (Must be sent to your home address)

You can order single issue or individual article. To purchase a single issue or an individual article as well as to view tables of contents and abstracts click on issue number.

Institutional price:

$518.00

Volumes per year:

various

For Online Access

Year 2004

• 3Thermal Sciences 2004
Proceedings of The ASME - ZSIS International Thermal Science Seminar II, Bled, Slovenia, June 13-16, 2004

1032 pages

Volume price - $246.00

Visualization of micro- and macromixing phenomena in stirred vessels by optical methods

Dieter Mewes
University of Hannover, Institut fur Verfahrenstechnik (Process Engineering), Callinstr. 36, 30167 Hannover, Germany

Kerstin Kling
Institute of Process Engineering, University of Hannover, Callinstr. 36, 30167 Hannover, Germany

ABSTRACT

The course of Micro- and Macromixing inside a stirred vessel is visualized by means of two different optical measurement techniques, the optical tomography and the Planar Laser Induced Fluorescence (PLIF) technique. In order to distinguish between macro- and micromixing, a mixture of two dyes is injected into the mixing vessel. One component is an inert dye whereas the second dye is undergoing a fast chemical reaction with the vessel content. The distribution of the inert dye throughout the mixing vessel visualizes the macromixing but does not predicate the mixing quality on the nano scale. Since the chemical reaction requires mixing on the molecular scale, the reacting dye, which is changing its emission characteristics during the reaction, indirectly visualizes the micromixing.
The tomographical dual wavelength photometry is used to measure the three-dimensional, transient concentration fields in the whole vessel at the same time. Measurements with the Planar Laser Induced Fluorescence technique are performed in an arbitrary plane of the vessel. This restriction on a two-dimensional concentration field is recompensed with a much higher spatial resolution which allows to visualize small scale structures in the order of 100 μm.
For both techniques low Reynolds number measurements are performed in a mixing vessel equipped with a Rushton turbine. Results are presented as two- or three- dimensional concentration fields. Areas of micromixing are detected by calculating the local degree of deviation from the concentration fields. They are depending on the injection position of the dye and are mainly found in the boundary layer of the lamellas.