A thin-walled metal pipe of Diameter(D) 50 mm covered with a 25 mm thick layer of insulation (0.085 Wm−1K−1 ) and carrying superheated steam at atmospheric pressure is suspended from the ceiling of a large room. The steam temperature entering the pipe is 423K, and the air temperature is 293K. The convection heat transfer coefficient on the outer surface of the covered pipe is 5 Wm−2K−1 . If the mean velocity of the steam is 10 m/s, at what point along the pipe will the steam begin condensing?