Experiments have been conducted to determine local heat transfer coefficients for flow perpendicular to a long, isothermal bar of rectangular cross section. The bar is of width e parallel to the flow, and height d normal to the flow. For Reynolds numbers in the range 104 < Ra≤ 5 × 104, the face-averaged Nusselt numbers are well correlated by an expression of the form The values of C and m for the front face, side faces, and back face of the rectangular rod are found to be the following:

Determine the value of the average heat transfer coefficient for the entire exposed surface (that is, averaged over all four faces) of a c = 40- mm-wide, d = 30-mm-tall rectangular rod. The rod is exposed to air in cross flow at V = 10 m/s, T = 300 K. Provide a plausible explanation of the relative values of the face-averaged heat transfer coefficients on the front, side, and back faces.