Residence time distributions (RTD) are measured for both a baffled and an unbaffled laboratory reactor of the same size with several internal pipes and a Rushton turbine operating at different feed flow rates and impeller rpms. Ideal behavior as determined by the mean and the variance of the RTD was observed at an impeller Reynolds number of 2327 for the baffled tank and 3878 for the unbaffled tank both in the turbulent transition range. The experimental results for the baffled tank are compared to computational fluid dynamics (CFD) predictions of the RTD using the k-turbulence model in Fluent for transitional flow regime in the tank, i.e., impeller Reynolds number between 10 and 10 000. All the qualitative aspects of the predicted RTDs are similar to those measured experimentally. The mean residence times as well as the variances of the residence time are accurately predicted by CFD in the transition flow regime.

The process of synthesizing silica nanopowder by the gas phase thermal oxidation of tetraethylorthosilicate in a diffusion flame reactor was simulated using a commercial computational fluid dynamic code. The fuel combustion process and silica particle formation and growth in the flame were modeled. The temperature, velocity, and particle size distribution (PSD) fields inside the reactor were computed. Chemical reaction rate and a population balance model were used to calculate the particle formation and growth and PSD. Satisfactory results were obtained for the temperature profile and PSD. Computed values of the average size of the final products were consistent with those obtained in a previous experimental work.

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