Binary diffusion and heat transfer in laminar free convection boundary layers on a vertical plate

Abstract

Free convection in laminar boundary layers with coupled momentum, heat and binary mass transfer was investigated in terms of relevant parameters. Buoyancy effects caused by both temperature and concentration gradients were considered. Exact solutions of the nonlinear system of three coupled equations for variable physical property systems with a constant generating body force parallel to the solid surface were investigated for many different cases in order to get a reasonable idea of how the various parameters influence the transport processes involved. The effects of variations in specie enthalpy, thermal conductivity, viscosity and density with concentration were studied individually and in various combinations. The most striking effects are those caused by specie enthalpy differences and thermal conductivity for the low molecular weight gases. Also the interactions of Prandtl number and interfacial velocity effects for single component mass-transfer systems were investigated. A method of integrating the coupled transport equations was developed which appears to be substantially faster than previously used techniques. The improved speed of computation occurs primarily because each solution of the momentum equation is obtained by iterating only on a boundary condition rather than on both a boundary condition and a function as previous methods require.