Numerical analysis of nonequilibrium gas flows induced by evaporation from two-dimensional nanoscale slit arrays*

Increasing power density of electronic devices necessitates advanced thermal management technology that can dissipate high heat flux of the order of >1 kW/cm². One of the options is a nanoporous membrane-based evaporative cooling device, where a vapor flow induced by evaporation forms a highly nonequilibrium region near the membrane, so-called the Knudsen layer. In this work, we analyze the non-equilibrium flows of polyatomic gas molecules evaporating from two-dimensional nanoscale pore arrays using the direct simulation Monte Carlo (DSMC) method and clarify the effect of the pore size and pore spacing on the flow characteristics. In addition, we present a method to deal with the Knudsen layer with the low variance DSMC (LVDSMC) method, which can drastically reduce the statistical noise at low Mach number conditions compared with the conventional DSMC method.