Heat and mass transfer in monolithic honeycomb catalysts—III: Radiation model

Abstract

An analysis is made of the effect of radiation exchange upon the behavior of an exothermic catalytic reaction occurring on a surface of a cylindrical passage. An a priori model was developed for calculation of temperature and conversion profiles in the passage and solid phase as well. The model postulates plug flow and gas-to-solid heat and mass transfer. The gas is assumed to be transparent but radial exchange within the passage, longitudinal conduction of the solid phase and exothermic reaction occurring on the catalyst surface are taken into account. The governing equations describing this model represent a nonlinear boundary value problem for ordinary differential equations and integro-differential equation of Fredholm type subject to integral boundary conditions. The resulting set of nonlinear differential and integro-differential equations was approximated by a special finite-difference scheme and quadrature formulas. The set of nonlinear algebraic equations was solved by the Newton-Raphson method. It was found that radiation exchange can cause significant changes of temperature distribution in the passage. Calculated examples indicated that the model suggests the existence of multiple steady states.