Combined heat and mass transfer in mixed convection along vertical and inclined plates

Abstract

An analysis is performed to study the heat- and mass-transfer characteristics of mixed convection flow along vertical and inclined flat plates under the combined buoyancy effects of thermal and mass diffusion. The analysis is for processes in which the diffusion-thermo and thermo-diffusion effects as well as the interfacial velocities due to mass diffusion are negligibly small. The plate is either maintained at a uniform temperature/concentration or subjected to a uniform heat/mass flux. Numerical results for the local Nusselt number and the local Sherwood number are presented for diffusion of common species into air and water. In general, it has been found that for the thermally assisting flow, the local surface heat- and mass-transfer rates are further enhanced when the buoyancy force from mass diffusion assists the thermal buoyancy force, but are reduced when the two buoyancy forces oppose each other. These trends are reversed for the thermally opposing flow. In addition, the effects of the combined buoyancy forces on the surface heat- and mass-transfer rates are found to diminish as the angle of inclination from the vertical increases. A comparison is also made between results from the uniform surface heat/mass flux and the uniform wall temperature/ concentration.