Air at 206.8 kPa and an average of 460 K is being heated as it flows through a (steel) tube of5.4 mm inside diameter at a velocity of 7.62 m/s. The heating medium is 500 K steam condensing on the outside of the tube. Since the heat-transfer coefficient of condensing steam is 10500 W/m2 · K.

a. Calculate the convective coefficient hi of air for an L/D = 120.

b. Calculate the convective coefficient hi of air for entrance region L/D = 10.

c. Calculate the overall coefficient Ui based on the inside surface area and the heat transfer flux q/A for L/D = 120