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Q$1]$ A porous solid was dried in a pan $[2$ in $*2$ in$]$ and $0\mathrm{.}5$ in depth. The drying from critical moisture content of $0\mathrm{.}5k\frac{g}{k}g$ dry solid to $0\mathrm{.}15k\frac{g}{k}g$ D$.$S required $5h.$ All the drying was in the falling rate period and are considered to be approximated by a straight line. The equilibrium moisture $G$ content is $0\mathrm{.}1k\frac{g}{k}g$ D$.$S when it contact with air feed to the dryer at $75$C and $400lb/$hr$.$ft flowrate.

It is proposed to dry the product from initial moisture content of $0\mathrm{.}45k\frac{g}{k}g$ of dry solid to $0\mathrm{.}2k\frac{g}{k}g$ of dry solid.

A$.$ What will be the time required for drying.

B$.$ Wet$-$bulb temp. of air if the humidity of air $=0\mathrm{.}02k\frac{g}{k}g.$

Given: $h=0\mathrm{.}0128G^{0\mathrm{.}8},G$ in $l\frac{b}{h}r.f{t}^2$

$G=Q.Q$

$W=2450k\frac{J}{k}g.,h$ in $k\frac{w}{m^2}*k$