It is desired to dry $10$ kg$/$min of soap continuously from $20\%$ moisture by weight to $4\%$ moisture in a countercurrent stream of hot air. The air enters the dryer at the rate of $30\mathrm{.}0$ m$3/$min at $350$ K$,101\mathrm{.}3$ kPa, and initial water$-$vapor partial pressure of $2$ kPa. The dryer operates at constant temperature and pressure.

Calculate the moisture content of the entering air, in kg of water$/$kg of dry air.

Calculate the flow rate of dry air, in kg$/$min$.$

Calculate the water$-$vapor partial pressure and relative humidity in the air leaving the dryer.

Answer: $24\mathrm{.}7\%$ relative humidity