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Geometry effects on ignition in catalytic monoliths
Author(s) -
Ramanathan Karthik,
Balakotaiah Vemuri,
West David H.
Publication year - 2004
Publication title -
aiche journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.958
H-Index - 167
eISSN - 1547-5905
pISSN - 0001-1541
DOI - 10.1002/aic.10120
Subject(s) - nusselt number , sherwood number , laminar flow , geometry , thermodynamics , chemistry , mechanics , heat flux , ignition system , diffusion , heat transfer , reynolds number , materials science , physics , mathematics , turbulence
The convection–diffusion equations with wall reaction are solved for the case of fully developed laminar flow in monoliths having smooth (circular or flat plate) as well as geometries with sharp corners (triangular, rectangular, square, or sinusoidal). The circumferentially averaged Nusselt/Sherwood numbers along the channel length are calculated and their dependency on the local Damköhler number (ϕ s 2 ), solid to fluid conductivity ratio (κ = k s /k f ), and monolith aspect ratio (d h /L) is studied. As these parameters are varied, the asymptotic Sherwood/Nusselt numbers are bounded by the constant flux (Sh H 2/Nu H 2), the axially constant flux (Sh H 1/Nu H 1), and the constant wall temperature (Sh T /Nu T ) asymptotes. For asymmetric geometries, the difference between Nu H 2and Nu H 1is a measure of the nonuniformity of ignition in the circumferential direction for κ = 0. When wall conduction is significant (κ ≥ 10), ignition can be predicted accurately by using Nu H 1value in a one‐dimensional model, whereas conversion in the mass transfer controlled regime is determined by Sh T . © 2004 American Institute of Chemical Engineers AIChE J, 50: 1493–1509, 2004