Evaporation of a bicomponent droplet during depressurization

•Large concentration gradient exists within bicomponent droplet under pressure drop.•For ethanol/water droplet, higher ethanol concentration accelerates its evaporation.•For acetic acid/water droplet, the addition of water inhibits its evaporation.•Larger pressure drop results faster evaporation rate and lower droplet temperature.

This paper reports an experimental and numerical study of evaporation process of a two-volatile bicomponent (ethanol/water and acetic acid/water) droplet during depressurization. The environmental pressure, the ambient temperature, and the droplet temperature are investigated during the experiments. A mathematic model is then constructed to simulate the droplet evaporation process. The model solves one-dimensional heat conduction equation and species diffusion equation to acquire the temperature distribution and the concentration distribution inside the droplet. The activity coefficient is introduced to imitate the vapor partial pressure at the droplet surface. By numerical calculations, the variations of temperature distribution and concentration distribution within the ethanol/water droplet and the acetic acid/water droplet are discussed. The effects of composition, final ambient pressure and initial droplet diameter on droplet evaporation are also analyzed in the current study. Results show that the model predictions agree well with the measured temperature data, demonstrating the soundness of the present model and providing insight into the complex heat and mass transfer during the evaporation process of a bicomponent droplet under depressurization.