- 8-81 Air flows in a pipe under fully developed conditions with an average velocity of 1.25 m/sand a temperature of 20°C. The pipe's inner diameter is 4 cm, and

its length is 4 m. The first half of the pipe is kept at a constant wall temperature of 100°C. The second half of the pipe is subjected to a constant heat flux of 200 W.Determine (a) the air temperature at the 2 m length, (b) the air temperature at the exit, (c) the total heat transfer to the air, and (d) the wall temperature at the exit of the tube. Evaluate the properties of air at 80°C.FIGURE P8-81