No abstract

No abstract

The combined effects of buoyancy forces from thermal and species diffusion on the heat and mass transfer characteristics are analyzed for laminar boundary layer flow over a horizontal flat plate. The analysis is restricted to processes with low concentration levels such that the interfacial velocities due to mass diffusion and the diffusion-thermo/thermo-diffusion effects can be neglected. Numerical results for friction factor, Nusselt number, and Sherwood number are presented for gases having a Prandtl number of 0.7, with Schmidt numbers ranging from 0.6 to 2.0. In general, it is found that, for the thermally assisting flow, the surface heat and mass transfer rates as well as the wall shear stress increase with increasing thermal buoyancy force. These quantities are further enhanced when the buoyancy force from species diffusion assists the thermal buoyancy force, but are reduced when the two buoyancy forces oppose each other. While a higher heat transfer rate is found to be associated with a lower Schmidt number, a higher mass transfer rate occurs at a higher Schmidt number.

The combined effects of buoyancy forces from t h e m 1 and mass diffurion in laminar boun&ry layer adjacent to a continuous, horirontal m t phte moving through an otherwise quiescent fluid are studied analytically by the local nonsimiloriry method of solution In the analysis. the diffusion-thenno and thermo-diffurin effects as well as the interfacial velocities due to mass diffusion are neglected Numerical results me presented for a Prundtl number of 0.7. with Schmidt numbers of 0.6 and 2.0, for thermal buoyancy parameter Gr,/Rep mnging from 0 to 1.0 and relative buoyancy parameter N = Gr,,,/Gr, from -0.5 to 2.0. In genetul, it her been found thar the wall shear stress and the surface heat and maw tramfer mres increase wirh inereusing thermal buoyancy force. These quantities are funher increased when the buoyancy force from mau dufusion assicrs the thermal buoyancy force, but are decreased when it opposes the thermal buoyancy force. While a Schmidt number of 0.6 ic found to yield higher wall shear stresses and surface heat mnsfer mtes, higher surface mass rmnsfer mres occur for a Schmidr number of 2.0. A compurison wirh the results for a srario~ry phte reveals that a continuous moving phte provides larger hear and mass transfer rates than a stationary plate.

No abstract