Fluid Dynamics of Jet Mixing Reactors for Building Simulation Models

Continuous flow microreactors are used in the synthesis of nanoparticles, critical materials for the biomedical and agricultural industries. Their value results from their unique, size-dependent properties that differ from those of larger, bulk materials. At the lab-scale, nanoparticle synthesis is achieved primarily in batch. However, these processes become uneconomical at the industrial scale up because of poorer mixing that results in inhomogeneous concentration gradients and polydisperse particles. Continuous flow configurations, such as the jet mixing reactor (JMR), would improve industrial synthesis of these materials by improving mixing.

The JMR consists of three input streams that meet at a central mixing point and exit through the output line. The three streams consist of two 0.02” jet lines that flow antiparallel to each other and one 0.04” main line entering perpendicular to the jet lines. The main and jet lines have different compositions and mix in the central region to produce the product line. The primary goal of this project is to obtain experimental mixing time data to be used to validate and construct COMSOL fluid dynamic models.

We compared experimental measurements and COMSOL simulations of mixing time. In well-mixed situations, a kinetically-limited regime prevails that results in monodisperse particles. Small mixing times of 0.5-100 milliseconds directly correlate with a kinetically-limited regime. Mixing time was measured through the commonly used Villermaux-Dushman reaction, which consists of a competing reaction set. Poorer mixing results from a stoichiometric defect of acid that produces triiodide anions, whose yellow color can be measured through UV-Vis Spectrophotometry. Different flow rates in symmetric flow conditions from 8 to 14 mL/min were tested, and the mixing time was determined to be <100 milliseconds for all conditions, which compared favorably to previous studies of the JMR.

Asymmetric flow configurations are also being studied because limiting the flow of one line could provide economic, product, or safety benefits. We are testing the effect of main to jet line flow ratio on mixing time. Our long-term goal is to examine different JMR geometries to further improve the mixing time, guided by machine learning-directed COMSOL simulations.