Evaluation of permeability applicability based on continuum mechanics law in fluid flow through graphene membrane

Graphene is expected to be used in separation applications such as desalination. However, it is difficult to predict the flow phenomena at the nanoscale using the conventional continuum law. Particularly at a Knudsen number (Kn) of >0.1, which is applied in filtration, it has been reported that not even slip boundary conditions can be applied. In this study, to identify the parameters that affect the applicability of the continuum law, we conducted a fluid permeation simulation using graphene. The deviation of the permeability from that of the continuum model was calculated by changing the channel width, fluid temperature, and fluid type. The result showed that the channel width has the largest influence among the three factors, and that the magnitude of the divergence is sorted out based on the Knudsen number. Therefore, the permeability can be predicted even at the nanoscale where the continuum law cannot be applied.