“…The 60-mm-diameter vessel (working volume = 1.7 × 10 -3 m -3 ) is representative of a large HTE vessel, such as those employed in industry for three- or four-phase slurry catalyst screening. The larger vessel of 88-mm diameter (working volume = 5 × 10 -3 m -3 ) is comparable to the smallest categories of laboratory-scale vessels that have been used in previous mixing studies. ,, …”
Section: Introductionmentioning
confidence: 81%
“…The larger vessel of 88-mm diameter (working volume ) 5 × 10 -3 m -3 ) is comparable to the smallest categories of laboratory-scale vessels that have been used in previous mixing studies. 8,15,16 2. Experimental Section 2.1.…”
With the increasing implementation of high-throughput experimentation techniques within research laboratories throughout the chemicals industries, it is important that the flow regimes in such unbaffled vessels be fully characterized and the implications on mixing performance be understood. Particle image velocimetry (PIV) and planar laser-induced fluorescence (PLIF) techniques are used in this work to study the mixing and hydrodynamic behavior of low-viscosity fluids in small stirred vessels with diameters 60 and 88 mm. Baffled and unbaffled vessels are considered, and the difference in efficiency is quantified at a constant power input per unit volume. Positioning the impeller into an eccentric configuration is adopted as a means toward improving mixing efficiency in unbaffled vessels. Results show that the eccentric configuration provides equally efficient mixing as the traditional baffled vessel in terms of mixing time and turbulent kinetic energy distribution. PIV and PLIF measurements show that the distribution of turbulent kinetic energy is more evenly spread in smaller vessels, leading to the conclusion that such vessels are better mixers.
“…The 60-mm-diameter vessel (working volume = 1.7 × 10 -3 m -3 ) is representative of a large HTE vessel, such as those employed in industry for three- or four-phase slurry catalyst screening. The larger vessel of 88-mm diameter (working volume = 5 × 10 -3 m -3 ) is comparable to the smallest categories of laboratory-scale vessels that have been used in previous mixing studies. ,, …”
Section: Introductionmentioning
confidence: 81%
“…The larger vessel of 88-mm diameter (working volume ) 5 × 10 -3 m -3 ) is comparable to the smallest categories of laboratory-scale vessels that have been used in previous mixing studies. 8,15,16 2. Experimental Section 2.1.…”
With the increasing implementation of high-throughput experimentation techniques within research laboratories throughout the chemicals industries, it is important that the flow regimes in such unbaffled vessels be fully characterized and the implications on mixing performance be understood. Particle image velocimetry (PIV) and planar laser-induced fluorescence (PLIF) techniques are used in this work to study the mixing and hydrodynamic behavior of low-viscosity fluids in small stirred vessels with diameters 60 and 88 mm. Baffled and unbaffled vessels are considered, and the difference in efficiency is quantified at a constant power input per unit volume. Positioning the impeller into an eccentric configuration is adopted as a means toward improving mixing efficiency in unbaffled vessels. Results show that the eccentric configuration provides equally efficient mixing as the traditional baffled vessel in terms of mixing time and turbulent kinetic energy distribution. PIV and PLIF measurements show that the distribution of turbulent kinetic energy is more evenly spread in smaller vessels, leading to the conclusion that such vessels are better mixers.
“…Due to the complex setup used for this technique, ERT is employed for validation of computational fluid dynamics (CFD) mixing predictions instead of determining mixing time. The tomographic measurements using the dual wavelength photometry developed by Buchmann and Mewes give comparable results with ERT except that both micro- and macromixing are studied. 1 Mixing systems: (a) single shaft configuration; (b) dual shaft configuration; (c) Maxblend configuration.…”
A new image analysis technique is proposed to determine the macromixing time in a transparent stirred tank.
It consists of capturing on video a decolorization process by using a fast acid−base indicator reaction and
employing image analysis to quantify the color evolution. The color change is quantified by means of individual
thresholds on the RGB color model and provides a direct measurement of the macromixing evolution as it
can be seen by an operator in front of the vessel. It is shown that this technique removes the subjectivity of
the estimation of macromixing time by the naked eye, has a high degree of reliability and repeatability, and
can yield accurate macromixing information by considering the possible presence of segregated regions and
dead zones. Moreover, applications show that the macromixing curves bring new insights to study and compare
mixing efficiency of different impellers or multiple impeller mixing systems.
This article addresses the characterization of dispersion and homogenization phenomena in stirred vessels through the analysis of dispersion curves that can be obtained experimentally by means of conductivity measurements. New insights on mixing conditions can be achieved from the analysis of the qualitative and asymptotic properties of tracer dispersion curves. The results obtained are interpreted in the context of the spectral approach to the advection‐diffusion equation. It is shown that any flow model aimed at reproducing the experimentally determined dispersion curves must be at least two‐dimensional. Convection‐enhanced dispersion associated with the spectral structure of the advection‐diffusion equation is addressed.
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