CFD simulation analysis of fouling formation in a milk falling-film evaporator

The concentration of milk in falling-film evaporators suffers the risk of fouling formation that reduces the quality of the product and increases financial losses. The literature indicates the importance of this topic in the food industry and the need for further research. This study presents a computational fluid dynamic (CFD) analysis of the fouling formation during milk concentration in ANSYS FLUENT (R). This analysis includes boiling, nonNewtonian flow of the falling-film, and fouling prediction by kinetic models. The proposed system applied the required CFD tests to guarantee suitable results: meshing test, iteration test, and flow regime analysis. The results satisfactorily matched the falling-film thickness and the Reynolds number with experimental data and also contained the oscillation level of the film, temperature distribution, and the risk zones of fouling formation during the descendent flow. The inlet velocity and the overall heat transfer coefficient were changed to determine their influence on the fouling formation, and the inlet velocity was found to be the preponderant factor. The cases demonstrated a low effect of the oscillations and the remarkable influence of the falling-film thickness on the fouling formation. These results indicate the importance of keeping the tube wet during the evaporation process.