# Hydraulic Permeability

The hydraulic permeability of a membrane is the inverse of the fluid resistance normalized to the membrane area.

Experimentally it is found with

# $latex \epsilon = \frac{Q}{\Delta P \, A_m}$

Where Q is the measured flow rate, $latex \Delta P$ is the pressure drop across the membrane and $latex A_m$ is the membrane area.

It can be calculated from membrane properties with

# $latex \epsilon = \frac{\phi }{A_p \, R_f }$

Where $latex R_f$ is the fluid resistance of a pore (Hagen Pousille or Dagen), $latex A_p$ is the area of a pore and $latex \phi$ is the porosity.