Einladung zum Vortrag im Kolloquium Systemdynamik und Prozesstechnik
Simulation of Reactive Flows:
Micromixing in Multiphase Systems with Fast Reactions
Prof. Dr. Johannes Khinast
, Rutgers State University of New Jersey
Zeit: Freitag · 12. 7. 2002 · 14:00 Uhr
Ort: Hörsaal V 9. 41 · Pfaffenwaldring 9 · Campus Stuttgart-Vaihingen
novel, highly efficient solver for Navier-Stokes, mass and heat balance
equations was developed, which allows the numerical simulation of flows with
a large number of reacting species. A main advantage of our algorithm is
that the code is stable even for very stiff reaction networks.
Using this solver, micro-mixing effects in multiphase flows were studied.
Our group showed that the selectivity and yield of fast gas-liquid reaction
networks depends on the flow around single bubbles, that is, mainly on the
dynamics of the wake. Depending on bubble size and shape, the bubble wake
can be either closed (with or without recirculation) or open (vortex
shedding). Spherical bubbles have only closed wakes without recirculation,
while all other bubble types exhibit recirculation or vortex shedding
depending on their shape and the Reynolds number. A model was developed,
which accounts for the flow around the bubble, mass transfer, and reactions.
As a test reaction the oxidation of cyclohexane was chosen, which is a
highly complex free-radical reaction of industrially importance for the
manufacture of Nylon-6 and Nylon6,6 and other synthetic materials. The main
results of our work are that (1) the different residence times in the bubble
wake and at the bubble roof can lead to the formation of different products,
(2) recirculation in the bubble wake acts as a transport barrier for the
liquid-phase reactants, and (3) vortex shedding causes qualitatively
different mixing patterns than a closed wake, thus leading to a different
product distribution in the case of mixing-sensitive reactions.
Prof. F. Allgöwer · Institut für Systemtheorie technischer Prozesse · (0711) 685-7733 ·