In this work the heat transfer of a thin-film evaporator in ionic liquid purification, as a recycling step in a cellulose fiber production process, was modeled. A literature survey over the field of falling film and agitated thin film evaporation was undertaken to summarize the existing knowledge on the process. To provide a basic understanding of the model dynamics, a short introduction over the area of computational fluid dynamics was given also. A brief enumeration of exemplary research CFD applications of evaporation processes rounded off the theoretical part. Experiments with the thin-film evaporation were conducted to evaluate the process parameters and to create an empirical basis for the model evaluation. In a first stage, a correlation analysis of the different process variables was completed with the results of the thin-film evaporation of water. Then, in the second stage the process parameters were adjusted for a conclusive set of experiments for ionic-liquid purification that represented the actual experimental basis for the model evaluation. The modeling part consists of three different models. In the first one, a two-phase CFD Openfoam model was used to set up a case for falling-film flow. Although it was not possible to build up a fully working model, it provided some information on the validity of previous assumptions of thin film evaporation. Two other models were designed in Comsol to predict the heat transfer of the process in terms of required vaporization energy for evaporation. Both were liquid single-phase models.Instead of a continuous flow a series of ideal stages was assumed. Each single stage was simulated in the model and the results were interpolated to attain a result over the whole evaporator column. The models were opposed to the experimental values. In three out of four cases the model did not match with the empirical result. The possible reasons for the divergence were discussed and summarized.