Though it may be classified as a rather simple mistake, a frequent cause for substantial error in convection calculations is failure to select the correct geometry for the problem. Consider the following three geometries for flow of air at 1 atm, 300 K, and a Reynolds number of 50,000:
(a) Flow across a cylinder with diameter of 10 cm,
(b) Flow inside a tube with diameter of 10 cm
(c) Flow along a flat plate of length 10 cm. Calculate the average heat-transfer coefficient for each of these geometries and comment on the results.