Publikationsrepositorium - Helmholtz-Zentrum Dresden-Rossendorf

CFD simulations of dispersed bubbly flow on the scale of technical equipment are feasible within the Eulerian two-fluid framework of interpenetrating continua. However, accurate numerical predictions rely on suitable closure models. To achieve predictive capability, all details of the closure models have to be fixed in advance without reference to any measured data.
Concerning the fluid dynamics of bubbly flows a baseline model has recently been proposed to this end and shown to work for a range of different applications in a unified manner [1,2]. This provides a reliable background which is well suited to add more complex physics.
Concerning mass transfer in bubbly flows both with and without an accompanying chemical reaction only few studies have been performed to date [e.g. 3 and Refs. therein]. For the mass transfer coefficient, a variety of entirely different closures have been applied in rather similar situations. To facilitate predictive applications, a standard model which is validated for a broad range of conditions yet has to be developed. The effect of a chemical reaction on the mass transfer is described by an enhancement factor which depends on the type of the reaction. As an example for which some measured data are available for comparison [4], the absorption of CO2 in NaOH is considered.

[1] Rzehak, R., Ziegenhein, T., Kriebitzsch, S., Krepper, E., and Lucas, D. (2017), Unified modeling of bubbly flows in pipes, bubble columns, and airlift columns, Chem. Eng. Sci. 157, 147-158.
[2] Rzehak, R., Krauß, M., Kovats, P., and Zähringer, K. (2017), Fluid dynamics in a bubble column: New experiments and simulations, Int. J. Multiphase Flow 89, 299-312.
[3] Rzehak, R., and Krepper, E. (2016), Euler-Euler simulation of mass-transfer in bubbly flows, Chem. Eng. Sci. 155, 459-468.
[4] Darmana, D., Henket, R., Deen, N. and Kuipers, J. (2007), Detailed modelling of hydrodynamics, mass transfer and chemical reactions in a bubble column using a discrete bubble model, Chem. Eng. Sci. 62, 2556–2575.