An improved numerical model for evaporation with multicomponent gas

Evaporation is a key process in a wide range of industrial applications. To gain a better insight into this process, investigation on the evaporation model is an important aspect. In the present study, it is found that the computation with the Hertz-KnudsenSchrage model is not easy to converge in the numerical simulation of the evaporation with multicomponent gas. The reason for the divergence is that the Hertz-Knudsen-Schrage model will lead to an improper vapor mass fraction which is much larger than the saturated vapor mass fraction in the iterations. To improve the convergence performance, an improved model for evaporation with multicomponent gas is proposed. In the improved evaporation model, when the predicted vapor density is larger than the saturated vapor density, a strategy that calculates the volumetric mass transfer rate with the difference between the saturated vapor density and the current vapor density will be implemented. As a result, the vapor density is bounded by the saturated values and no improper large vapor mass fraction arises in the iterations. The improved evaporation model shows much better convergence performance. In the case of the present study, the improved evaporation model can converge with the time step of 5×10-6s, while the original Hertz-Knudsen-Schrage model cannot converge with the time step of 5×10-9s. The improved evaporation model is also compared with the empirical correlations and shows a good agreement.