Hydrogen separation from H-2-N-2 gas mixtures by means of high-permeance Pd membranes is an appropriate route to gain pure hydrogen for fuel cell applications. To figure out the mass transfer phenomena of H-2 in membrane tubes, H-2 permeation and recovery characteristics of two high-permeance Pd membranes are investigated. Four important factors influencing H-2 permeation, namely, the H-2 pressure difference, H-2 concentration, the flow rate at the exit of the retentate side, and membrane temperature, are taken into account. The experimental results suggest that decreasing H-2 concentration, flow rate, and temperature reduce the permeances of the membranes and H-2 recovery, even though the H-2 pressure difference is identical. The dimensionless permeance, a permeance ratio between H-2-N-2 gas mixture and pure H-2 as feed gases, is used to evaluate the extent of concentration polarization. Within the investigated ranges of the four factors, the dimensionless permeances of the two membranes are in the ranges of 0.022-0.206 and 0.042-0.359, respectively, revealing that the concentration polarization diminishes the permeance of the membranes down to the level within two orders of magnitude. Nevertheless, over 46% of H-2 is recovered. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.