Chapter 8, Problem 8.61P

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

(a) If the tube surface is maintained at a uniform temperature of $\text{27}°\text{C}$ . what is the outlet temperature of the water, $T_{m,o}$ ? To obtain the properties of water, assume an average mean temperature of $T_m=300$ K.

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

(c) In the foregoing calculations, were the assumed values of $T_m$ and $T_f$ appropriate? If not, use properly evaluated properties and recompute $T_{m,o}$ , for the conditions of part (b).