Simulation of the evaporation/boiling transition for the vaporization of a bi-component droplet under wide-temperature environments

A boiling model was proposed and coupled with a quasi-dimensional evaporation model to simulate the vaporization of a bi-component droplet under wide-temperature environments. Different from previous droplet evaporation models, the transition between droplet evaporation and boiling was especially focused on in this study. In the boiling model, the bubble point temperature of the bi-component mixture was employed to determine the critical condition for the occurrence of the boiling phenomenon. The mass rate of the boiling vaporization of the droplet was calculated by combining the heterogeneous nucleation model, bubble growth model, and bubble fragmentation model. Based on the measurements of the vaporization of an n-heptane/n-hexadecane droplet, the results indicate that the present vaporization model can satisfactorily reproduce the droplet lifetime and diameter evolution under wide ambient temperatures. The simulation results of the vaporization process are greatly affected by the boiling mass rate as the droplet enters the boiling stage. The heterogeneous nucleation rate is the main factor affecting the boiling mass rate, and the decrease of effective thermal conductivity slows down the overall droplet vaporization rate.