Experimental study on hydrodynamics of ionic liquids systems in falling film evaporator

Ionic liquids (ILs) have been proved as novel excellent solvents in gas separation and so on. Due to its excellent heat and mass transfer performance, falling film evaporator is often used in the applications of high viscosity systems and has the potential to be the regeneration equipment for IL-based systems. However, there are few reports on the falling film evaporation of ILs system. The relevant experimental data are scarce. Moreover, the traditional models cannot predict the hydrodynamics of ILs well due to the specific properties of ILs. In this study, an experimental method for studying the ILs falling film flow was established. The falling film hydrodynamics of three ILs (BmimBF4, BmimPF6, OmimBF4), including film flow pattern and film thickness were investigated. The effects of streamwise flow distance and the physical property of ILs on the hydrodynamics were analyzed. A calculation model and a dimensionless empirical model of ILs film thickness were established based on experimental data. The average relative deviation of new dimensionless model is 2.83%, which is much lower than that of Nusselt model (13.48%). The measurement of key parameters and the establishment of models provide experiment data and basis for designing the falling film evaporator of IL-based systems.