AI AA-88-2640 Entropy Production in Radiation- Affected Boundary Layers

A one-dimensional divergence of the monochromatic heat flux for wall-affected attenuating thingas, is developed from general considerations. Here Ebl. K~ cy and r, respectively denote the monochromatic values of the emissive power, absorption coefficient of gas, wall emissivity and optical thickness; , E, is the second exponential integ-ral, y the -4' coordinate normal to boundary. infinite geometry. The model applies to semiFor the spectral average of the heat flux divergence (needed for radiation-affected thermal transport), new definitions are i n t d u c e d (including the wall and attenuation effects) for the absorption coefficient of gas and the wall emissivity. This heat flux is applied to thermal baundary layer over a horizontal Rat plate. An explicit expression for the local Nusselt number involving both conduction and radiation is shown to be Nu: k i n g the Nusselt number for pure conduction, the wall gradient of temperature for pure conduction, 4 the wall emissivity, P the ratio of emission to conduction, and the local optical thickness. The effect of radiation an the thermal part of entropy production is demonstrated in terms of the forced convection over a flat plate.