Measurements of turbulence in a microscale multi-inlet vortex nanoprecipitation reactor

• Published in: Journal of micromechanics and microengineering Vol. 23; no. 7; pp. 75005 - 10
• Main Authors: Shi, Yanxiang, Cheng, Janine Chungyin, Fox, Rodney O, Olsen, Michael G
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 01.07.2013; Institute of Physics
• Subjects: Chemical synthesis methods; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Fluctuation; Fluid dynamics; Fluid flow; Materials science; Methods of nanofabrication; microfluidics; microreactor; nanoprecipitation; Physics; Reactors; Reynolds number; Turbulence; Turbulent flow; turbulent mixing; Vortices; Viscosity; Particle size; Mixing; Turbulence; Chemical precipitation; Reynolds number; Velocity distribution; Nanoparticles; Nano precipitate; Vortices; Shear stress; Particle image velocimetry; Nanomaterial synthesis
• ISSN: 0960-1317; 1361-6439
• DOI: 10.1088/0960-1317/23/7/075005

The microscale multi-inlet vortex reactor (MIVR) is designed for use in Flash NanoPrecipitation (FNP), a promising technique for producing nanoparticles within small particle size distribution. Fluid mixing is crucial in the FNP process, and due to mixing's strong dependence upon fluid kinematics, investigating velocity and turbulence within the reactor is crucial to optimizing reactor design. To this end, microscopic particle image velocimetry has been used to investigate flow within the MIVR. Three Reynolds numbers are studied, namely, Rej = 53, 93 and 240. At Rej = 53, the flow is laminar and steady. Due to the strong viscous effects at this Reynolds number, distinct flow patterns are observed at different distances from the reactor top and bottom walls. The viscous effects also retard the tangential motions within the reactor, resulting in a weaker vortex than appears at the higher Reynolds numbers. As the Reynolds number is increased to 93, the flow becomes more homogeneous over the depth of the reactor due to weaker viscous effects, yet the flow is still steady. The diminishing effects of viscosity also result in a stronger vortex. At the highest Reynolds number investigated, the flow is turbulent. Turbulent statistics including tangential and radial velocity fluctuations and Reynolds shear stresses are analyzed for this case in addition to the mean velocity field. The tangential motions of the flow are strongest at Rej = 240. Both the tangential and radial velocity fluctuations increase as the flow spirals toward the center of the reactor. The magnitudes of the tangential and radial velocity fluctuations are similar, suggesting that the turbulence is locally isotropic.