Hydraulic mean radius for flow through packed bed of spherical particle of size, ‘Dp, with porosity ‘ε’ is________________?
A. (Dp/6) (ε/1- ε)
B. (Dp/6) (1- ε/ε)
C. ⅔Dp (1- ε/ε)
D. ⅔Dp (ε/1- ε)