This work presents a computational fluid dynamic (CFD) model to investigate the effect of binary gas (H-2/Ar) composition and fluid dynamics at high temperatures (from 200 up to 500 degrees C) for a reasonably sized membrane module containing two cobalt oxide silica membrane tubes in series for H-2 separation. The model provided the local information of velocity, pressure and H-2 fraction for the driving force analysis. The H-2 molar fraction was found to be the most influential factor affecting the driving force, though the total pressure varied slightly along the axial length. In feed domain the H-2 molar fraction showed a clear decline in the axial direction from feed inlet to retentate outlet by 45.34% (for the case of feed fraction 50% H-2 and feed flow rate 100 N ml min(-1)). In permeate domain, H-2 fraction showed the same trend but the decline slope was much less than feed domain being 2.22%. Concentration-polarizations in both feed and permeate domains were very weak with the concentration polarization degree less than 0.4% and can be ignored in cobalt-oxide-silica membrane module. High temperature promoted the performance of pure gas permeation, but had little impact on mixed gas separation as the driving force reduction at higher temperature is more significant. (C) 2014 Elsevier Ltd. All rights reserved.