Evaporation of a Heated Hydrocarbon Liquid from a Free Surface

This work addresses the topical problem of improvement of the mathematical model for calculating the evaporation rate from the free surfaces of accidental spill pools to determine the explosibility indicators of technological units. A comparative analysis of the results of calculating the mass of evaporated liquid from the pool surface of heated benzene is carried out using a semi-empirical model and a computational fluid dynamics (CFD) model. The effect of wind velocity and pool length and depth on the mass of the evaporated liquid is analyzed. It is shown that for pools of liquids with high molecular weight and at low wind velocity (1 m/s), the semi-empirical model can result in significant overestimation (severalfold) of the values of the evaporated mass, since, unlike the CFD model, it does not take into account the buoyancy effects. The buoyancy effects are expressed in the fact that the vertical density gradient that occurs above the pool surface contributes to the suppression of turbulence (stable density stratification), which, in turn, prevents the removal of vapors from the interface, leading, as a result, to a decrease in the intensity of evaporation. It is shown that the role of buoyancy effects is higher when the wind velocity is lower, the initial thickness of the pool is larger, and the horizontal pool size is larger. It is shown that the semi-empirical model demonstrates a weaker dependence of the mass of the evaporated liquid on the horizontal dimensions of the pool compared to the CFD model, since it does not take into account the effects of buoyancy, which increase with an increase in the dimensions of the pool.