Hydrodynamic characterization of a new small-scale reactor mixed by a magnetic bar

• Characterization of mixing process in a novel small-scale reactor.
• Development of three original-novel methods to analyze the mixing process.
• Validation of an image analysis method to determine mixing time in a small stirred reactor
• Comparison of 3 numerical approaches and validation of CFD tool to analyze the mixing process.

The purpose of this study was to evaluate the mixing characteristics of a new milliliter-scale (mL-scale) reactor developed for studying enzymatic activity or physiological cell response. The mL-scale reactor was designed to enable the integration of several sensors to carry out dynamic measurements in a controlled environment. Rapid homogeneity of the entire system is essential to ensure reproducible and reliable results, consequently the reactor was stirred to optimize both mass and heat transfers. A comparative study using three different techniques was undertaken to study mixing performances in the system. Firstly, mixing time (tm) was estimated in the reactor using both experimental methods, including instrumental method and image analysis, and CFD. As hydrodynamics is not occurring in the fully-turbulent regime, turbulent numerical simulations using the SST transitional and the standard k-ϵ turbulence models were conducted and compared to laminar approach. Results showed good agreement between the two experimental methods and no significant differences were observed between the simulation methods. Moreover, according to results, a minimum agitation rate of 350 rpm seemed to be appropriated to obtain a quick homogenization in the system. Finally, the second part of the study seemed to indicate that probes had no significant impact in the studied reactor.