PROBLEM 4

Problem 7.21. Atmospheric water at 300 K flows through a 0.5 cm inner diameter tube that is 12 cm long. The velocity

at inlet can be assumed to be uniform, and equal to 2.5 m/s. The surface temperature is 350 K.

a) Find the heat transfer coefficient at the exit.

b) Suppose that the mean surface roughness was 46 um. Estimate the heat transfer coefficient at the exit.

c) For part a, calculate the time-average water temperature at exit on the centerline of the tube.

Hint: The Fanning friction factor C, can be found from the correlation of Churchill (1977a) for the transition flow

regime.