On the Comparison between Presumed and Full PDF Methods for Turbulent Precipitation

Turbulent precipitation is an important topic in chemical reaction engineering because of its numerous industrial applications. Several modeling approaches have been used in the past, but in recent years, computational fluid dynamics (CFD) coupled with micromixing models has been successfully applied to predict the influence of mixing on the crystal size distribution (CSD). The micromixing model is generally based on the presumed probability density function (PDF) approach, such as finite-mode PDF or beta PDF, and the aim of this work is to compare presumed PDF predictions and full PDF predictions with experimental data. The experimental data were obtained from a tubular reactor in which turbulent precipitation of barium sulfate is carried out from aqueous solutions of barium chloride and sodium sulfate. The implementation of the presumed PDF model was done using FLUENT user-defined subroutines, whereas the full PDF calculations were carried out with an in-house code based on Monte Carlo methods using the flow field prediction from FLUENT.