Investigating the validity of Schrage relationships for water using molecular dynamics simulations.

Abstract

Recently, molecular dynamics (MD) simulations were utilized to show that Schrage theory predicts evaporation/condensation mass fluxes with good accuracy in the case of monoatomic and non-polar molecular fluids. Here, we examine if they are equally accurate for molecular polar fluids, such as water. In particular, using molecular dynamics (MD) simulations, we study the steady state evaporation/condensation processes of water in a one-dimensional heat-pipe geometry to ascertain the validity of Schrage relationships. Non-equilibrium mass flow is driven by controlling the temperatures of the source/sink. Equilibrium simulations are utilized to evaluate the saturation properties and the mass accommodation coefficients as a function of temperature. Our results indicate that Schrage equations predict the evaporation/condensation rates of water with good accuracy. Moreover, we show that molecular velocity distributions in the vapor phase are indeed Maxwellian distributions shifted by the velocity of the macroscopic vapor flow, as assumed in Schrage's theoretical analysis.