A flat slab of wood $7$cm thick containing $40$wt$\%$ moisture is being dried

from both sides $($drying on other sides and edges is neglected$).$ Hot air flows

over both sides of the slab, and the equilibrium moisture at the wood surface

due to is held at $8$wt$\%.$ The wood piece may be considered as a semi$-$infinite

slab. The diffusivity of the moisture in the wood is h

$/$

cm

$10$x$72\mathrm{.}32$

$.$

Page $1$ of $2$

a$)$ Calculate the time for the centre to reach $29\mathrm{.}91$wt$\%$ and $10$ wt$\%$

b$)$ Determine the fluxes in a$)($specify the unit$).$

Note: wt $\%=1$g water$/100$g of dry wood.