Comparison of micromixing models for CFD simulation of nanoparticle formation

Reactive precipitation is an important research topic in chemical engineering because of its numerous industrial applications in the formation of nanoparticles. Recently, computational fluid dynamics (CFD) has been successfully coupled with micromixing models and probability density function (PDF) methods to predict the effect of mixing on the particle size distribution. The micromixing model is generally based on the presumed PDF method. The objective of this work is to compare multienvironment-presumed PDFs and a recently proposed direct-quadrature-method-of-moments-interaction-by-exchange-with-the-mean (DQMOM-IEM) micromixing model with transported PDF predictions for the simulation of reactive precipitation, including simultaneous mixing-limited reaction, nucleation, and growth in a plug-flow reactor. DQMOM is applied to calculate the turbulent spurious dissipation rate for the multienvironment micromixing models. The results show that the DQMOM-IEM model agrees well with the transported PDF simulations, even when the number of nodes used in DQMOM is small (such as 2-4). Given the computational efficiency of the DQMOM-IEM model relative to transported PDF methods, this model offers great promise as a practical CFD tool for simulating plant-scale reactors. (C) 2004 American Institute of Chemical Engineers.