The top surface of a heated compartment consists of very smooth (A) and highly roughened (B) portions, and the surface is placed in an atmospheric airstream. In the interest of minimizing total convection heat transfer from the surface, which orientation, (1) or (2), is preferred? If Ts = 100°C, T∞ = 20°C, and U∞; = 20 m/s, what is the convection heat transfer from the entire surface for this orientation?

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0.5 m + A (1) 0.5 m or or T, (2) B.