Comparison of Experimental and Computational Particle Trajectories in a Stirred Vessel

Abstract

A particle trajectory in a turbulent flow is measured by a 3-dimensional tracking technique and compared with the pattern calculated by a Lagrangian model. The geometry chosen is a standard vessel provided with a Rushton turbine. First, the flow field is simulated using the commercial Fluent package. The impeller global performance is determined. The dimensionless numbers are calculated: t c , N QP , N P . These results are validated by LDV data. The numerical particle trajectory is compared to the experimental trajectory, and the reliability of the numerical trajectory is proved. Finally, some news tools for analyzing the flow are presented. Useful information is included in the long particle trajectory, which enables one to compute a probability of presence. The fluid dynamic behavior is visualized by PoincarØ sections.

On the performance of static mixers: A quantitative comparison

“…Although higher order SMX(n) elements, like the n = 4, SMX (4,7,12), or the n = 5, etc. versions, of course yield continuously more compact mixers but at cost of high pressure losses, the n = 3, SMX (3,5,9) is a good compromise in the series of compact motionless mixers. The building block of the SMX(n) designs can be injection molded, see [26], and thus can any mixer be build up from staggered building blocks inside a square hollow pipe, and can be made disposable.…”

“…Because this series is based on optimum interfacial stretching per element [26], Schemes 1 and 2 in Table 1 are identical. The standard SMX is defined as a (2,3,8) mixer, that is somewhere in between the (2, 3, 6) and (3,5,9) configurations of the optimum interfacial stretch series, and clearly does not have this advantage. Where ideally it would result in 8 Nelem − 1, see Fig.…”

“…Results are as expected: simple geometries need large lengths, compact mixers need large pressure gradients. The most energy efficient mixer is the Kenics, shortly followed by the SMX (1, 1, 3) while the most compact mixer is the SMX (4, 7, 12) shortly followed by the SMX (3,5,9).…”

“…Not shown in the figure, for clarity, are results of slightly different variants, like the square (1, 1, 3) and (3,5,9) and the circular (4,7,12); they perform similar as their counterparts. The conclusion is that simple mixers are long and complex mixers short, with an interesting exception for the new SMX (1, 1, 3, Â = 90 • ) and SMX (1, 1, 4, Â = 135 • ) designs.…”

“…The review paper of Thakur et al [8] provides a nice summary that discusses in what applications static mixers are beneficial and to be preferred above stirred vessels and other conventionally agitated vessels. Over the years various groups work on mixing in those stirred and agitated vessels using both new experimental and computational methods, like for example Barrue, who focuses on particle trajectories in stirred vessels [9] and also studies mixing in the turbulent regime [10]. Important handbooks and textbooks that discuss fluid mixing and applications in process technology from a much wider perspective are those of Oldshue [11], Nienow et al [12] and Kresta [13].…”