Chapter 8, Problem 8.127P

The final step of a manufacturing process in which a protective coating is applied to the inner surface of a circular tube involves passage of dry, atmosphere air through the tube to remove a residual liquid associated with the process. Consider a coated $\text{5}-\text{m}$ -long tube with an inner diameter of $\text{5}0\text{ mm}$ . The tube is maintained at a temperature of $\text{300 K}$ . and the residual liquid exists as a thin film whose corresponding vapor pressure is $\text{15 mm Hg}$ . The molecular weight and diffusion coefficient of the vapor are $M_A=70$ kg/kmoland $D_{AB}={10}^{-5}{\text{m}}^{\text{2}}\text{/s}$ , respectively. Air enters the tube at a mean velocity of $0.\text{5 m}$is and a temperature of $\text{3}00\text{ K}$.

(a) Estimate the partial pressure and mass density of vapor in the air exiting the lube.

(b) What is the rate of liquid removal from the tube in kg/s?