Microfilter simulations and scaling laws

A series of direct simulation Monte Carlo calculations of flows through mic rofilters were performed to evaluate the range of validity of a previously derived scaling law. This scaling law, which describes how the pressure dro p across a filter depends on the Reynolds number and filter geometry, is ba sed on Navier-Stokes calculations and experiments in the continuum regime. The simulations show that this sealing law predicts the correct Reynolds nu mber dependence for a fixed Knudsen number, but the magnitude of the pressu re drop is overpredicted as effects due to collisional nonequilibrium becom e important. The results of the simulations were used to derive a correctio n term to the scaling law that includes the Knudsen number and, thus, accou nts for nonequilibrium effects.