The average interstitial velocity in a packed bed is $2\mathrm{.}5$ m$/$s and the superficial velocity

under minimum fluidization condition is $1$ m$/$s$.$ Solid particles having density of $1200$

kg$/$m$3$

and size of $0\mathrm{.}15$ mm are to be fluidized using air at $3$ atm absolute pressure and

$30$oC temperature having a density of $3\mathrm{.}5$ kg$/$m$3$

$.$The empty bed cross section is $0\mathrm{.}4$ m$2$

and the bed contains $400$ kg of solid. What will be the pressure drop at minimum

fluidization condition?