Steady-state temperature of a roof, estimate the maximum temperature attained by a level roof at 45° north latitude on June 21 in clear weather. Radiation from sources other than the sun may be neglected, and a convection heat transfer coefficient of 2.0 Btu/hr ∙ ft² ∙ F may be assumed. A maximum temperature of 100°F may be assumed for the surrounding air. The solar constant of Example 16.4-1 may be used, and the absorption and scattering of the sun's rays by the atmosphere may be neglected.

(a) Solve for a perfectly black roof.

(b) Solve for an aluminum-coated roof, with an absorptivity of 0.3 for solar radiation and an emissivity of 0.07 at the temperature of the roof.