Klinkenberg correction

Under steady state and laminar flow condition, Klinkenberg demonstrated that the permeability of porous media to gases is approximately a linear function of the reciprocal pressure.

When Klinkenberg defined the interactions to be considered, he supposed the existence of a layer (sometimes called Knudsen layer), thinner than molecular mean free path, adjacent to the pore’s wall where only molecules-wall collisions would occur and collisions among molecules could be ignored. Thus the slippage velocity, as obtained from the Klinkenberg’s approach, captures the contribution of molecule-wall interactions and when this velocity is zero, the Poiseuille velocity profile (which results from molecule-molecule interactions) is recovered. However, Klinkenberg’s formulation ignores the transition flow region, where neither molecule-molecule nor molecule-wall interactions can be neglected because both are playing a relevant role. The feasibility of Klinkenberg linear function of the reciprocal pressure depends on the Knudsen number. For Knudsen numbers from 0.01 to 0.1 the Klinkenberg approach is acceptable.