Comparative assessment of diffusion modeling methods in evaporation problems of liquid bulk cargoes during tanker loading

This paper examines various models describing the evaporation of liquid bulk cargoes based on the classical diffusion equation. The numerical solutions obtained using the considered models were validated against well-known experimental data on methanol evaporation in a Stefan diffusion tube. A comparative analysis of experimental measurements and numerical modeling results demonstrates that the diffusion equation incorporating a correction for Stefan flow provides a more accurate description of the diffusive evaporation behavior of volatile substances. Within the framework of numerical simulations, dependencies of the mass transfer rate of the volatile component n-hexane (one of the primary constituents of light gasoline fractions) evaporating from a liquid surface during tank filling were obtained as functions of the filling velocity for different evaporation models. The results indicate that accounting for the Stefan flow correction in the diffusion equation significantly affects both the saturation time of the tank vapor space with product vapors and the total mass of vapors accumulated in the vapor–gas space by the time the tank is completely filled.