ID 81

Comparison of diffusion models for application in low- to high-pressure droplet evaporation problems

 

Abstract:

Several diffusion models are compared for their applicability in droplet evaporation modeling over a wide range of temperatures and pressures. Major differences in the physical derivation of the methods are being discussed. Most models being evaluated are only valid for the infinite dilution limit. Additionally they use various numbers of empirically fitted parameters to either correct or simplify correlations based on kinetic theory. All non-ideal models are a strong function of either ambient or mixture density. As an alternative approach, corrections to ideal gas models have been also considered. They are shown to be similarly accurate as more complicated methods for near- and supercritical solvents. However, care should be taken when applying them to the liquid-like supercritical region. Concentration dependence of the coefficient is shown to be important with some systems, especially near the critical point. Finally, the sensitivity of an evaporation model to diffusion coefficient estimation is demonstrated to be significant only for very high pressures. The choice of a reference state, at which the diffusion coefficient is calculated, is of relevance only in presence of large temperature difference between the drop and the surrounding gas.