Numerical analysis of the effects of temperature and concentration jumps on transient evaporation of moderately large (0.01 approx< Kn approx< 0.3) droplets in non-isothermal multicomponent gaseous mixtures

摘要

In this study transient evaporation of a single moderately large (0.01 approx< Kn approx< 0.3) droplet in non-isothermal multicomponent gaseous mixture taking into account the effects of temperature and concentration jumps is investigated numerically. System of nonstationary nonlinear energy and mass conservation equations is solved using anelastic approximation. The performed analysis is pertinent to slow droplet evaporation when Mach number is much less then unity (M 1). Transport coefficients are calculated as functions of temperature and concentrations of the gaseous species. The dependence of the droplet surface temperature on time is taken into account. Comparison of numerical results obtained using models with different types of boundary conditions at the gas-liquid interface is performed. It is found that the effect of temperature and concentration jumps on the evaporation of moderately large droplet during warming-up period is significant when the temperature and vapor concentration at the droplet surface is relatively low. It is shown that in case of large concentrations at the droplet surface boundary conditions for concentration jump obtained from kinetic theory and those obtained from the Fick's law yield the same results. It is shown also that taking into account the kinetic effects results in a significant deviation from the D~2-law.