Buoyancy Effects on Heat and Mass Transfer in Boundary Layer on a Continuous, Moving Horizontal Plate

The combined effects of buoyancy forces from thermal and mass diffusion in laminar boundary layer adjacent to a continuous, horizontal flat plate moving through an otherwise quiescent fluid are studied analytically by the local nonsimilarity method of solution. In the analysis, the diffusion-thermo and thermo-diffusion effects as well as the interfacial velocities due to mass diffusion are neglected. Numerical results are presented for a Prandtl number of 0.7, with Schmidt numbers of 0.6 and 2.0, for thermal buoyancy parameter Grx/Rex s/2 ranging from 0 to 1.0 and relative buoyancy parameter N = Grx,c/Grx from —0.5 to 2.0. In general, it has been found that the wall shear stress and the surface heat and mass transfer rates increase with increasing thermal buoyancy force. These quantities are further increased when the buoyancy force from mass diffusion assists the thermal buoyancy force, but are decreased when it opposes the thermal buoyancy force. While a Schmidt number of 0.6 is found to yield higher wall shear stresses and surface heat transfer rates, higher surface mass transfer rates occur for a Schmidt number of 2.0. A comparison with the results for a stationary plate reveals that a continuous moving plate provides larger heat and mass transfer rates than a stationary plate.