Droplet Evaporation in a Turbulent Environment at Elevated Pressure and Temperature Conditions

Abstract

A three-dimensional numerical model is developed to assess the effect of freestream turbulence on the vaporization of n-heptane droplet, which is exposed to a freestream of nitrogen at elevated pressure and subcritical temperature conditions. The freestream pressure, temperature and turbulence intensity are varied in the range of 0.5–10 MPa, 324–502 K, and 0%–60%, respectively. Variable thermophysical properties, the unsteadiness behavior of the gas and liquid phases, as well as heat transfer by radiation are all considered. In addition, non-ideality behavior of the gas phase, solubility of the gas into the droplet and pressure dependence of the gas-phase thermophysical properties are also accounted for. The turbulence terms in the conservation equations of the gas-phase are modeled by using the shear-stress transport (SST) model. The results show that, for the temperature range (T∞ < Tc) explored in the present study, the droplet lifetime increases, and thereby the vaporization rate decreases, as pressure rises. However, the effect of pressure gradually diminishes as the ambient temperature increases and vanishes when T∞ approaches the critical temperature of n-heptane, Tc. Moreover, the effect of freestream turbulence intensity, which is found to enhance droplet heat and mass transfer, weakens as pressure increases. Finally, droplet turbulent heat and mass transfer correlations are proposed which account for all the aforementioned parameters.