(239e) Investigation of Mixing In a Microscale Reactor Using Confocal μ-LIF

Authors: 
Shi, Y., Iowa State University
Fox, R. O., Iowa State University


Mixing has a significant impact on many processes in chemical engineering and has been a bub-
bling area for decades. For example, ‘Flash Nanoprecipitation’, one promising technique that can
be used to produce nanoparticles within small size distribution, requires fast mixing. To understand
turbulent mixing in the reactors more thoroughly, the laser induced flourescence (LIF) method has
been developed and applied by many researchers to large scale reactors. It is proved LIF is one of
the best ways to measure the concentration fields. In this work, in conjunction with the confocal
laser scanning microscopy, which is capable of improving the resolution, this method is applied to
a microscale multi-inlet vortex (MIV) reactor.

Of the four inlet streams of the MIV, two opposing ones are dyed with Rhodamine 6G, in which
way mixing is visualized. As in a previous study on MIV [1], mixing effects at three inlet Reynolds
numbers, Rej = 53, 93 and 240, are investigated, each representing a flow regime. Flow is steady
and laminar at Rej = 53 but is turbulent at Rej = 240. Rej = 93, however, falls into the transi-
tion range. As such, different mixing patterns between streams are detected at different Reynolds
numbers. Due to scan speed limitation of the confocal system, line-scanning data at 21 different
locations are acquired for statistical analysis. By subtracting the background noise from the mixing
data and then normalizing it against the dye data, the mean concentration profiles and root mean
square (RMS) of the fluctuations can be obtained. These experimental results are compared to
large-eddy simulations to validate/improve the models. In addition to all that, a three dimensional
reconstruction is also obtained to give us more intuitive insight on the mixing in the reactor.

[1] J. C. Cheng, M. G. Olsen and R. O. Fox. A microscale multi-inlet vortex nanoprecipitation
reactor: Turbulence measurement and simulation. Applied Physics Letters. 2009(94):204104

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