Evaluating the performance of static mixers using the -number: the case of the Koflo® mixer

Abstract

Static mixers (SMs) are widely used in applications that involve chemical reactions, heat transfer, blending of fluids, or some combination of these. Accurately evaluating the performance of SMs is critical for the appropriate selection of these devices. Traditional approaches involve parameters that separately evaluate the mixing level and the energy spent in mixing (i.e., pressure drop) but do not account for both simultaneously. The -number has been recently proposed as a means to simultaneously evaluate the quality of mixing as well as the pressure drop across the static mixer (SM). This work demonstrates an implementation of the -number by evaluating the performance of a KOFLO® static mixer (KSM) for mixing water vapor and air via Computational Fluid Dynamics (CFD), for Schmidt number of approximately unity. Pipe and mixer sizes as well as inlet profile distribution were varied. A single-element KSM was used based on the impetus of our study: Selective Catalytic Reactor (SCR) applications, which requires minimization of the pressure drop. The results are shown to be reasonably comparable with respect to previous works containing experimental data.