Radiation from the atmosphere or sky can be estimated as a fraction of the blackbody radiation corresponding to the air temperature near the ground, Tair, That is, irradiation from the sky can be expressed as G sky = ε sky σT4air and for a clear night sky, the emissivity is correlated by an expression of the form εsky = 0.741 + 0.0062TdP, where Tdp is the dew point temperature (oC). Consider a flat plate exposed to the night sky and in ambient air at 15°C with a relative humidity of 70%. Assume the back side of the plate is insulated, and that the convection coefficient on the front side can be estimated by the correlation h(W/m2 ∙ K) = 1.25∆T1/3, where T is the absolute value of the plate-to-air temperature difference. Will dew form on the plate if the surface is

(a) Clean and metallic with ε = 0.23, and

(b) Painted with ε = 0.85?