Abstract
We show that an accurate description of the mass transfer controlled
regime in long catalytic monolith channels in which the flow is fully
developed and laminar, requires the knowledge of two constants, namely,
the asymptotic Sherwood number (Shinfin, or dimensionless mass
transfer coefficient) and the first normalized Fourier weight, alpha1.
While the first of these has received considerable attention in the
literature, the second factor has been assumed to be unity. Because
of this systematic error (of about 20% for common channel geometries),
literature data and correlations for mass transfer in monoliths have
large uncertainties. We present new experimental data that corroborates
the theory and a new method for experimental estimation of the asymptotic
constants for any arbitrary channel shape. For the case of a square
channel we obtain experimental values for the constants of Shinfin=2.92+/-0.16
and alpha1=0.78+/-0.09, which are in excellent agreement with the
theoretical values (Shinfin=2.977 and alpha1=0.8074). Using the
asymptotic solutions of the convection-diffusion equation, we develop
new correlations for mass transfer coefficients for the case of developing
laminar flow that agree with numerical solutions of the Navier-Stokes
equations, and theory in the limits.
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