Modeling of interfacial mass transfer based on a single-field formulation and an algebraic VOF method considering non-isothermal systems and large volume changes

This work presents a consistent numerical model for the prediction of interfacial heat and mass transfer with high volume changes based on a single-field formulation and an algebraic Volume-of-Fluid (VOF) method. The model is based on the Continuous Species Transfer (CST) model for chemical species transport, and the compressive CICSAM scheme is used to advect both volume fraction and species concentration in order to ensure consistency. The computation of the interfacial mass transfer rate (ṁ) is based on the variables solved by the single-field formulation and four different procedures for its discretisation are analysed. It is shown that the discretisation of this term has a significant impact on the predictive capabilities of the model. The use of the compressive velocity term, which is based on the relative velocity between the phases (u_r) is also investigated for both the algebraic VOF method and the Compressive Continuous Species Transfer (C-CST) model. The results show that the use of u_r is not necessary if the CICSAM scheme is used for the discretisation of the advection terms of both the volume fraction and the concentration, even for advection-dominated cases with negligible diffusion. The modeling approach is validated against several test cases and applied to the heating and evaporation of droplets. The proposed numerical model provides accurate results for droplet evaporation and is able to handle the high concentration jump at the droplet interface and the high volume changes resulting from droplet evaporation.