Hydrodynamics numerical simulation of a vertical falling film evaporator for ionic liquid systems

With a series of advantages, falling film evaporator is potentially appropriate for the purification and regeneration of ionic liquids (ILs). Due to the unique molecular structure of ILs, the IL film in falling film evaporator exhibits special hydrodynamic behaviors compare with organic solvents. The Nusselt method exhibits large deviations in predicting the film thickness and film velocity of ILs, which can be ascribed to the neglect of surface tension. In consideration of surface tension and wall adhesion, a novel simulation model was developed for quantitatively predicting the hydrodynamics of falling film flow. With the proposed model, the film flow distribution, film velocity and thickness were investigated. The predicted film thickness data are in general agreement with the experimental results. A novel empirical film thickness correlation considering surface tension is proposed, with deviations less than ±10%. The hydrodynamic models will provide fundamentals for designing the falling film evaporator of IL systems.