Consider a thin-walled tube of 10-mm diameter and 2-m length. Water enters the tube from a large reservoir at in = 0.2 kg/s and Tm,i = 47°C.

(a) If the tube surface is maintained at a uniform temperature of 27°C, what is the outlet temperature of the water, Tm,o? To obtain the properties of water, assume an average mean temperature of Tm = 300 K.

(b) What is the exit temperature of the water if it is heated by passing air at T∝ = 100°C and V = 10 m/s in cross flow over the tube? The properties of air may be evaluated at an assumed film temperature of Tf = 350 K.

(c) In the foregoing calculations, were the assumed values of T m and Tf appropriate? If not, use properly evaluated properties and re-compute Tm,o for the conditions of part (b).