gm of a powder of particle density $1800k\frac{g}{m^3}$ are $1\mathrm{.}1$

charged into the cell of an apparatus for measurement of

particle size and specific surface area by permeability.

The cylindrical cell has a diameter of $1\mathrm{.}14cm$ and the

powder forms a bed of depth $1cm.$ Dry air of density $1\mathrm{.}2$

$k\frac{g}{m^3}$ and viscosity $18\mathrm{.}4{10}^{-6}$ Pas flows at a rate of $36$

$c\frac{m^3}{m}in$ through the powder. The measured variation in

pressure difference across the bed with changing air flow

:rate is given in Table Q$2$ below

Table $01$

:Determine

a$.$ Bed voidage

b$.$ assume that the pressure drop $-$ flow relationship for

this packed bed of powder is described by the

:Carman$-$Kozeny equation

$\frac{(-p)}{H}=180\frac{(1-)}{({}^3{)}^2}\frac{U}{x^2}$

$.$Calculate the surface$-$volume mean diameter