On the applicability of continuum scale models for ultrafast nanoscale liquid-vapor phase change

Continuum methods are efficient in modeling multi-phase flow at large time and length scales, however, their applicability to nanoscale systems and processes is questionable. When mean free path and average time between atomic collisions are comparable to the characteristic length and time scales of interest, the continuum hypothesis approaches its spatial and temporal limit. Here we discuss the implications of modeling such a limiting problem involving liquid-vapor phase change using continuum equations of mass, momentum, and energy conservation. Our results indicate that, continuum conservation laws can correctly represent the dynamics of the specific problem of interest provided appropriate constitutive relations are used at liquid-vapor interfaces. We show that with the Schrage relation for phase change rates and a physically motivated expression for temperature jump, interfacial phenomena can be described quite accurately. (C) 2020 Elsevier Ltd. All rights reserved.