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OpenFOAM Computational Fluid Dynamic Simulations of Two-Phase Flow and Mass Transfer in an Advanced-Flow Reactor

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journal contribution
posted on 08.07.2015, 00:00 by María José Nieves-Remacha, Lu Yang, Klavs F. Jensen
Advanced-flow reactor (AFR) technology is an alternative to scale-up continuous flow chemistries from micro to milli scales, while retaining mass and heat transfer performance. Here we conduct two-phase computational fluid dynamic (CFD) simulations using the open source software OpenFOAM in order to predict hydrodynamic parameters in the AFR for different operating conditions. After modification and validation of the interFoam solver based on the volume-of-fluid method to account for mass transfer across immiscible interfaces, it is applied to the AFR to predict specific interfacial areas (a) and individual mass transfer coefficients (kL) to yield overall mass transfer coefficients (kLa). The results are in good agreement with semiempirical values and the surface renewal theory of Danckwerts, except at the largest flow rates for which numerical coalescence is observed. A study of the influence of fluid properties yields the following conclusions. The contact angle is the variable that affects the flow patterns the most (and more specifically, the interfacial area); varying the contact angle can change the flow regime from bubbly to stratified flow. Decreasing surface tension decreases droplet size, but in order to achieve large specific interfacial areas and have a positive impact on the mass transfer process, a larger dispersed phase flow rate with increased holdup is also required. Viscosity of the continuous phase does not have a significant effect on mass transfer. The effect of reactor design was also seen to not be significant for the AFR designs and flow rates tested, with overall mass transfer coefficients varying within 17%.