You may have found that the design of the previous problem is not very satisfactory, so let us consider an alternative that uses vertical internals $)=(8(cm)$ to give the same equivalent bubble size in the big and small units. For this design find

$($a$)$ The bed diameter.

$($b$)$ The spacing of internals $($use an equilateral triangle arrangement$).$

$($c$)$ The depth of the fluidized bed, $L_f.$