Calculate the value of the average heat transfer coefficient for the plate of Problem 7.21 when the entire plate is rotated 90° so that half of the leading edge consists of a very smooth portion (A) and the other half consists of a highly roughened portion (B).

Data From Problem 7.21

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 T_s = 100°C, T_∞ = 20°C, and u_∞ = 20 m/s, what is the convection heat transfer from the entire surface for this orientation?

Transcribed Image Text:

0.5 m 1 m |+0.5 m+ A or B В or A И Т И Т A В (1) (2) B A