The sweep gas now effect on hydrogen production via water-gas shift reaction (WGSR) using a membrane reactor (MR) was studied numerically in this work. The sweep gas now rate was used as the primary parameter while the effects of flow pattern, inlet temperature, size, and gas type in the permeation side on MR performance were examined in detail. Using CO conversion and H-2 recovery to characterize the MR performance, it was found that the sweep gas flow with inlet/outlet ports arranged on the same side (parallel flow mode) is the optimal design providing higher CO conversion, H-2 recovery and lower reaction temperature compared with the other examined now pattern designs. By varying the sweep gas flow inlet temperature the sweep gas flow can serve as cooling or heating fluid in the reactor. For both cooling and heating cases reactor performance could be degraded due to lower catalyst activity and reversed WGSR, respectively. For the H-2-selective MR, the sweep gas type does not affect the MR performance under the same operating conditions. By changing the size of the permeation side it was found that H-2 recovery could be improved by permeation side reduction without significantly affecting the CO conversion. (C) 2014 Elsevier B.V. All rights reserved.