A model study has been conducted for Flash Nanoprecipitation(FNP)) - a novel approach to produce functional nanoparticles. A mixing study has been conducted in a custom-designed microscale multi-inlet vortex reactor (MIVR) and a scalar mixing model was validated against experimental data. A microPIV experiment was conducted to further validate the turbulent model. A population balance equation (PBE) has been proposed to model the FNP process. It was furthermore, integrated into a computational fluid dynamics (CFD) simulation of to yield conditions comparable to the real experimental settings. In coping with the complicated aggregation model in the CFD code, a new numerical approach, conditional quadrature method of moments (CQMOM), has been proposed, which is capable of solving the multivariate system efficiently and accurately. It is shown that the FNP process is highly influenced by mixing effects in the microreactor and thus coupling CFD with the kinetics model is essential in obtaining valid comparisons with experiments.