Mixed convection and diffusion of reactants, products, and heat with arbitrary-order heterogeneous and homogeneous reactions in a rectangular duct

Abstract

The influence of combined forced and free convection on the isothermal diffusion of reactants and products with arbitrary-order heterogeneous and homogeneous reactions in a rectangular laminar flow reactor is analyzed. The free convective motion, which is superimposed upon the main axial flow, arises from a transverse density gradient induced by the release of reaction products at the channel wall and in the flowing fluid. A numerical stream function-vorticity method is employed to solve the three-dimensional conservation equations in the case of large Schmidt number. The effects of Rayleigh number for mass transfer, reaction rate parameters, reaction orders, diffusivity ratio, and stoichiometric coefficient ratio upon the system performance are examined. Illustrations are performed to approximate parallel plates using a rectangular duct with small aspect ratios. The analysis may also be applicable to the analogous heat transfer phenomena for the nonisothermal reaction systems with buoyancy effects induced by the releases of both products and heat of reactions. Additional parameters, namely, Rayleigh number for heat transfer, Lewis number, and reaction heat parameters appear to describe the systems. The results are in fairly good agreement with known solutions for the simple systems derivable from the present work.