$21$: Cylinder direct flat cylinder

Problem:

A cylindrical naphthalene piece $10cm$ in diameter and $5mm$ thick is exnosed to air at $25C$ and $1$atm flowing on the upper surface at $10\frac{m}{sec}$ as she

a$)$ Calculate the time required for the whole piece to evaporate

Given:

$P_{\text{a}\text{n}\text{t}}=0\mathrm{.}011mmHg,P_{\text{m}\text{a}\text{t}}=1\mathrm{.}14g\frac{m}{c}{m}^3,D_{As}=0\mathrm{.}06c\frac{m^2}{sec,{}_c}=1\mathrm{.}86{10}^{-4}\frac{gm}{cm-sec},$

${}_{-}=1\mathrm{.}18{10}^{-3}\frac{gm}{c{m}^3}\frac{M}{w}{t}_{\text{a}\text{m}\text{t}}=128\mathrm{.}1,R=82\mathrm{.}05\frac{\text{a}\text{t}\text{m}*c{m}^3}{(mol)*K}$

If the mass transfer convection equal $K_G=8\mathrm{.}38{10}^{-5}\frac{\text{m}\text{o}\text{l}}{c{m}^2.sec.\text{a}\text{t}\text{m}},$ the time to evaporate whole piece

a$)380hr$

b$)550hr$

c$)1019hr$

d$)1500hr$

If the time to evaporate whole piece is reduced by $50\%,$ then the mass transfer convection $K_G$ :

a$)1\mathrm{.}2{10}^{-4}mo\frac{l}{c}{m}^2*sec*atm$

b$)1\mathrm{.}67{10}^{-4}mo\frac{l}{c}{m}^2.sec.$atm

c$)2\mathrm{.}4{10}^{-4}mo\frac{l}{c}{m}^2*sec.$atm

d$)3\mathrm{.}9{10}^{-4}mo\frac{l}{c}{m}^2*sec.$atm