The spectral absorptivity of a large diffuse surface is \(\alpha_{\lambda}=0.9\) for \(\lambda

(a) In case (a) the surface is exposed to the sun, which provides an irradiation of \(G_{S}=1200 \mathrm{~W} / \mathrm{m}^{2}\), and to an airflow for which \(T_{\infty}=300 \mathrm{~K}\). If the surface temperature is \(T_{s}=320 \mathrm{~K}\), what is the convection coefficient associated with the airflow?

(b) In case (b) the surface is shielded from the sun by a large plate and an airflow is maintained between the plate and the surface. The plate is diffuse and gray with an emissivity of \(\varepsilon_{p}=0.8\). If \(T_{\infty}=300 \mathrm{~K}\) and the convection coefficient is equivalent to the result obtained in part (a), what is the plate temperature \(T_{p}\) that is needed to maintain the surface at \(T_{s}=320 \mathrm{~K}\) ?

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h. T T Case (a) h. T T- LE, Tp Case (b)