[CCoE Notice] FW: PhD Defense Abstract - Santhosh Gundlapally

[Khator, Suresh]

Ph.D. Defense Announcement

Santhosh Gundlapally, Wednesday, July 13, 2011, 2:00 PM
Chemical Engineering Conference Room
Major Professor: Dr. V. Balakotaiah
Effect of Non-uniform Activity and Conductivity on the Steady-State and Transient Performance of Catalytic Reactors.
In the first part, we develop accurate correlations for estimating the local Nusselt and Sherwood numbers for developing flows with constant flux (slow reaction) and constant wall concentration or temperature (fast reaction) cases for a channel of arbitrary shape. These new correlations need only a single parameter, namely, the asymptotic value, which depends on the channel geometric shape. We use the new correlations to analyze the effect of flow conditions near the inlet of the channel on the ignition and extinction behavior of catalytic monoliths used in combustion and after-treatment applications as well as laboratory experiments. It is shown that the bifurcation behavior, such as the number and location of the ignition/extinction points, the number of stable steady-states and the hysteresis behavior is sensitive to the flow conditions in the entry region. Next, we study the effect of non-uniform catalyst activity and conductivity on the steady-state and transient performance of the monoliths.
In the second part, we examine pattern formation in a system consisting of a catalytic wire or a string of catalyst particles suspended in a fluid phase in an adiabatic reactor. For the case of uniform activity, conductivity and diffusivity in the solid phase, local bifurcation analysis and transient simulations  show that only moving temperature and concentration fronts exist when the Lewis number (Lef) ≥1, while both stationary and moving fronts exist when Lef<1. Next, we examine pattern formation with non-uniform activity but uniform conductivity and diffusivity within the solid and show that both stationary and moving patterns can exist for any value of Lef. Finally, we study the pattern formation with non-uniform activity, conductivity and diffusivity within the solid and show that stationary patterns can exist for any Lef and realistic values of all other parameters. This last result explains the differences between various literature results on pattern formation using discrete and continuum models with uniform properties. It shows that one of main reasons for stationary pattern formation in catalytic packed-bed reactors is the spatial non-uniformity in activity and conductivity caused due to the discrete nature of the solid phase (particles) with point contacts.
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