Henning Struchtrup (University of Victoria, Canada)

Title: Nonequilibrium Processes at Liquid-Vapor Interfaces
Abstract: While evaporation of liquids and condensation of vapors are processes of daily experience, as well as commonly employed in technical systems, some finer details of these processes are still surprisingly little understood. Theoretical evaluation as well as experiments yield finite temperature jumps between liquid and vapor on both sides of the interface, and deviations of pressure from equilibrium saturation pressure. As interface effects, these jumps are mostly visible in smaller, i.e., microscopic, systems, where interface resistances contribute relatively more to overall system resistance than in macroscopic systems. Nevertheless, significant temperature jumps were reported for systems on the centimeter scale.
In this presentation, I will discuss and compare various approaches to observe and model nonequilibrium interfaces, based on molecular methods, kinetic theory of gases, and nonequilibrium thermodynamics.  It will be shown that the often-used assumption of local thermodynamic equilibrium of the interface loses validity for the steep gradients encountered in molecular simulations. Accordingly, interface resistivities will not only depend on the local temperature, but as well on process quantities such as heat and mass flux across the interface.