$18\mathrm{.}37.$ Spray drying of an aqueous coffee.

A $25wt\%$ solution of coffee in water at $70F$ is spray$-$dried to a

moisture content of $5\%($dry basis$)$ with air entering at $450F$ and $1$

atm with a humidity of $0\mathrm{.}01l\frac{b}{l}b($dry basis$)$ and exiting at $200F.$

Assuming the specific heat of coffee $=0\mathrm{.}3Bt\frac{u}{l}b-F,$ calculate: $($a$)$

air rate in lb dry air$/$lb coffee solution; $($b$)$ temperature of evapora$-$

tion; $($c$)$ heat$-$transfer rate in Btu$/$lb coffee solution.