Kinetic boundary condition in vapor–liquid two-phase system during unsteady net evaporation/condensation

Abstract

Heat and mass transfer caused by nonequilibrium phase change (net evaporation/condensation) play a major role in a vapor-liquid two-phase flow. In general, liquid temperature changes with time because of the heat and mass transfer between the vapor and liquid phases; however, a precise investigation of the transport phenomena related to this temporal evolution of liquid temperature is still lacking. The aim of this study is to examine a kinetic boundary condition, which depends on liquid temperature, for the Boltzmann equation in a vaporliquid two-phase system with unsteady net evaporation/condensation. In this study, we confirmed whether the kinetic boundary condition follows the temporal evolution of liquid temperature attributed to unsteady net evaporation/condensation by using the molecular simulation based on mean-field kinetic theory, and then we validated the accuracy of the kinetic boundary condition by solving the initial boundary value problem of the Boltzmann equation in unsteady net evaporation/condensation. These results showed that the kinetic boundary condition follows the temporal evolution of liquid temperature in the simulation setting of this study. Furthermore, we concluded that the kinetic boundary condition that depends on liquid temperature is guaranteed to be accurate even in unsteady net evaporation/condensation by considering the temporal evolution of liquid temperature.

Mass transfer through vapour–liquid interfaces: a molecular dynamics simulation study

“…Some related simulation methods have been described previously in the literature. The heat and mass transfer through vapor-liquid interfaces during evaporation and condensation has been studied extensively in the literature using molecular simulation [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] or mesoscopic models such as density functional theory [8,13,17,[19][20][21][22][23]. Most of these studies consider a temperature gradient as the driving force of the heat and mass transfer.…”

Distributions of Two Atoms Collisions over the Surface of the Condensed Phase

“…Analysis of the evaporation of a substance consisting of molecules is a more complex task compared to the evaporation of a substance consisting of atoms, since when interacting with molecules, the exchange between the internal degrees of freedom of the molecules must be taken into account. With lowintensity evaporation of a substance, atoms or molecules can travel a sufficiently long distance before colliding [12][13][14][15], so there is a Knudsen layer near the wall surface and the surface of the condensed phase. In this layer, there are significant changes in the parameters that characterize the gas -temperature, density, etc.…”

Molecular Dynamics Investigation of Liquid and Vapor Interactions Near an Evaporating Interface: A Theoretical Genetics Perspective

“…[13,14] A classical Schrage model derived from kinetic theory explains the evaporation mass and energy fluxes at a liquid-vapor interface, which requires the precise measurement of interfacial thermofluidic parameters such as temperature and pressure. [15][16][17] In addition, the Schrage model and many other theories require the use of empirical parameters to be implemented in the models to account for intermolecular properties at the vapor-liquid interface. [14,18,19] For example, evaporation and condensation accommodation coefficients represent the probabilities for a liquid particle to evaporate and for a vapor particle to condense at the interface.…”