Gas Permeation Unit (GPU)

The intrinsic permeation property of a gas through a membrane is characterized by the permeability coefficient P of a gas A, P_A. Barrer was early introduced as a practical unit for this property and made it easy to compare the suitability of materials to be used for membrane gas separation. Barrer is also defined below.

Permeance is directly related to the thickness, l, of the membrane and as such defined as pressure-normalized steady-state flux, P/l. The permeance will characterize the gas transport through the membrane. Permeance is an important parameter when comparing the separation suitability of membranes for mixed gases. A practical unit often used is GPU (gas permeation unit) (see below).

Permeability:

$$ \begin{array}{ll}1 \mathrm{Barrer}& =1{0}^{-10}{\mathrm{cm}}^3\left(\mathrm{S}\mathrm{T}\mathrm{P}\right) \mathrm{cm} {\mathrm{cm}}^{-2}{\mathrm{s}}^{-1}\mathrm{cm} {\mathrm{Hg}}^{-1}\hfill \\ {}& =1,33\times 1{0}^{14}{\mathrm{m}}^3\left(\mathrm{S}\mathrm{T}\mathrm{P}\right)...