Thermal transport across the interface between liquid n-dodecane and its own vapor: A molecular dynamics study

There are two possible thermal transport mechanisms at liquid-gas interfaces, namely, evaporation/condensation (i.e., heat transfer by liquid-vapor phase change at liquid surfaces) and heat conduction (i.e., heat exchange by collisions between gas molecules and liquid surfaces). Using molecular dynamics (MD) simulations, we study thermal transport across the liquid-vapor interface of a model n-dodecane (C₁₂H₂₆) under various driving force conditions. In each MD simulation, we restrict the thermal energy to be transferred across the liquid-vapor interface by only one mechanism. In spite of the complex intramolecular interactions in n-dodecane molecules, our modeling results indicate that the Schrage relationships, which were shown to give accurate predictions of evaporation and condensation rates of monatomic fluids, are also valid in the prediction of evaporation and condensation rates of n-dodecane. In the case of heat conduction at the liquid-vapor interface of n-dodecane, the interfacial thermal conductance obtained from MD simulations is consistent with the prediction from the kinetic theory of gases. The fundamental understanding of thermal transport mechanisms at liquid-gas interfaces will allow us to formulate appropriate boundary conditions for continuum modeling of heating and evaporation of small fuel droplets.