A model porous block of cross-sectional area (A) and length (L) is made up of N independent capillaries of equal radii (r) and length (L)

Q. A model porous block of cross-sectional area (A) and length (L) is made up of N independent capillaries of equal radii (r) and length (L). The porosity of the block is 10%, and the permeability for a laminar, incompressible and steady state flow is 0.02 mD. If the flow is only through the capillaries, then the value of r is____________x 10-6 cm (round off to 1 decimal place). [1 mD = 10-15 m2].

Ans: 3-5

Sol:

k = (ϕr2/8)

0.02 x 10^-11 = (0.1r2/8)

r = 4 x 10^-6 cm