The spectral absorptivity of a large diffuse surface is????=0.850 for ??<1???? and ????=0.25 for ???1????. The bottomof the surface is well insulated, while the top may be exposed toone of two different conditions.
(a) In case (a) the surface is exposed to the sun, which providesan irradiation of ????=1200 W/m2, and to an airflow for which T =300 K. If the surface temperature is Ts =320 K, what is theconvection coefficient associated with the airflow?
(b) In case (b) the surface is shielded from the sun by a largeplate and an airflow is maintained between the plate and thesurface. The plate is diffuse and gray with an emissivity of????=0.8. If ???=300 K and the convection coefficient 30 W/m2K,what is the plate temperature Tp that is needed to maintain thesurface at Ts =320 K?
(c) in case (b) the large surface and the plate both have adimension of 8m by 8m, and the separation distance is 2m. The otherconditions remain the same. What would be the plate temperaturethat is needed to maintain the surface at Ts=320K?
