$7\mathrm{.}7$ A drier requires $1\mathrm{.}50\frac{m^1}{s}(3178f\frac{t}{m}in)$ of air at $65C,20\%$ humidity. This is to be prepared

HUMIDIFICATION OPERATIONS $273$

from air at $27C$ dry$-$bulb, $18C$ wet$-$bulb temperatures by direct injection of steam into the airstream followed by passage of the air over steam$-$heatind finned tubes. The available steam is saturated at $35000\frac{N}{m^2}(5\mathrm{.}08l\frac{b_r}{i}{n}^2)$ gauge. Compute the kilograms of steam per second required $($a$)$ for direct injection and $($b$)$ for the heat exchanger.

Ans:: $($a$)0\mathrm{.}0463k\frac{g}{s}$; $($b$)0\mathrm{.}0281k\frac{g}{s}.$