A 10-m long circular steel pipe (k60 W/m C) with an outside diameter of 100 mm and 8 mm wall thickness is used to carry hot air from one location to another The pipe is not insulated and is exposed to cold ambient air at -10C which moves cross flow over the pipe at a flowrate of 5 m/s. The temperature of the inner surface of the pipe can be taken as an average temperature of 80 C

a. Determine the external heat transfer coefficient and -the heat loss from the pipe if radiation loss from the pipe and the pipe wall resistance can be neglected.

b. if instead of using a circular pipe, the hot air is transported using a 10 m- long rectangular duct whose cross section is 10 cm X 10 cm, calculate the heat loss from the duct. Neglect the resistance of the pipe wall.

C. For the circular pipe in (a), calculate the heat loss if radiation heat loss is to be included. The emissivity of the pipe can be taken as 0.4 and the resistance of the thin wall pipe can be neglected.