Felix Kexel, M.Sc.

Eißendorfer Str. 40, Building N, Room 1.082

Telephone +49 40 42878-4663

E-Mail: Felix Kexel, M.Sc.


DFG Priority Project 1740 - "Reactive Bubbly Flows"


How are the diffrent timescales of fluid dynamic mixing, mass transfer and reaction kinetics imapcting the yield and selectivity of competitive-consecutive gas-liquid reactions?

Applying measuring techniques as Particle Image Velocimetry (PIV), Laser Induced Fluorescence (LIF) or imaging UV-VIS Spectroscopy to obtain information on velocity and concentration fields of primary and secondary products in the wake of rising gas bubbles


Graduate Teaching Assistant

  • Fluid Mechanics in Process Engineering (Winter term)


Supervised Theses

Current Thesis:
  • "Experimentelle Untersuchung des Einflusses der Fluiddynamik auf eine kompetitiv-konsekutive Reaktion in einer Hele-Shaw Zelle" [Working Title], Rene Weglewski, Master thesis
Finished Thesis:
  • "Taylor Bubbles in Organic Solvents", Sina Bertram, Bachelor thesis, 2022
  • "Computation of Unsteady Mass Transfer in Bubble Wakes by Means of 2D Lagrangian Analysis", Lotta Kursula, Master thesis, 2022
  • "Anwendung der Penetrationstheorie auf lokale Stofftransportprozesse an Taylor Blasen", Benjamin Rahimian, Bachelor thesis, 2022
  • "Characterization of the fluid dynamic properties of a Methanol based chemical reaction", Noah von Schnitzler, Bachelor thesis, 2021
  • "Taylor Bubble Generation Using a Selonoid Valve", Tarlan Ramazanli, Project Work 2021
  • "Detailed investigations of bubble trajectories in clean and contaminated systems", Sam Dors, Bachelor thesis, 2020
  • "Determination of mass transfer coefficients from single Taylor bubbles in contaminated systems – a study for industrial applications", Aaron Kaulbarsch, Bachelor thesis, 2019
  • "Experimentelle Analyse des Einflusses von organischen Lösemitteln auf die Hydrodynamik von Taylorblasen am Bespiel von Acetonitril", Carolin Lohmann, Bachelor thesis, 2019

Oral and Poster Presentations

  • Kexel, F.; Bertram, S.; Mehrbach, T.; von Kameke, A.; Hoffmann, M.; Tomiyama, A.; Schlüter, M.: "Influence of Taylor Bubble Shapes on Wake Structures" 4th International Symposium on Multiscale Multiphase Process Engineering, Berlin, 2022, poster presentation
  • Radmehr, A; Kexel, F.; von Kameke, A.; Hoffmann, M.; Schlüter, M.: "Local Velocity Fields at Taylor Bubbles in Methanol" 11th Workshop Chemical and Biological Mico Laboratory Technology 2022, Ilmenau, 2022, oral presentation
  • Kexel, F.; von Kameke, A.; Hoffmann, M.; Schlüter, M.: "Fluid Dynamics of Taylor Bubbles in Organic Solvents" ProcessNet Jahrestreffen Mehrphasenströmungen, Mechanische Flüssigkeitsabtrennung & Zerkleinern und Klassieren 2022, virtual, 2022, oral presentation
  • Kexel, F.; von Kameke, A.; Hoffmann, M.; Schlüter, M.: "Investigation on Velocity and Concentration Fields at Taylor Bubbles in a Reactive Bubbly Flow" Dispersed Two-Phase Flows 2021, virtual, 2021, oral presentation
  • Kexel, F.; von Kameke, A.; Hoffmann, M.; Schlüter, M.: "Influence of Fluid Dynamics on the Selectivity of Competitive Consecutive Gas Liquid Reactions" 13th European Congress of Chemical Engineering (ECCE13), virtual, 2021, oral presentation
  • Kexel, F.; von Kameke, A; Hoffmann, M.; Schlüter, M.: "Optimization of Chemical Reactions with Tailored Flow Strucures" ProcessNet Jahrestreffen Reaktionstechnik 2021, virtual, 2021, poster presentation
  • Kexel, F.; von Kameke, A; Hoffmann, M.; Schlüter, M.: "Investigation of the influence of fluid dynamics on the selectivity of fast gas-liquid reactions by means of high speed imaging UV/VIS spectroscopy at a Taylor bubble setup" ProcessNet Jahrestreffen Mehrphasenströmungen & CFD 2021, virtual, 2021, poster presentation
  • Kexel, F.; von Kameke, A.; Colombi, R.; Rüttinger, S.; Hoffmann, M.; Schlüter, M.: "Inverstigation of Reactive Mass Transfer Processes at Single Rising Bubbles by Means of Time-Resolved Scanning Laser Induced Fluorescence" 12th European Congress of Chemical Engineering (ECCE12), Florence, Italy, 2019, oral presentation 
  • Kexel, F.; Rüttinger, S.; Kastens, S.; von Kameke, A.; Oßberger, M.; Hoffmann, M.; Schlüter, M.: "Does the wake structure in bubbly flows affect yield and selectivity of a competitive consecutive reaction? – A Taylor-Bubble study" ProcessNet Jahrestreffen Reaktionstechnik & Mehrphasenströmungen 2019, Würzburg, 2019, oral presentation


Title: Experimental Investigation of Reactive Bubbly Flows—Influence of Boundary Layer Dynamics on Mass Transfer and Chemical Reactions. <em>Reacticve Bubbly Flows</em>
Written by: Kexel, F.; Kastens, S.; Timmermann, J.; Kameke, A. v.; Schlüter, M.
in: (2021).
Volume: Number:
on pages: 267–307
Editor: In Schlüter, M.; Bothe, D.; Herres-Pawlis, S.; Nieken, U. (Eds.)
Publisher: Springer:
ISBN: 978-3-030-72361-3
how published:
DOI: https://doi.org/10.1007/978-3-030-72361-3_12


Abstract: Bubbly flows are extensively used processes in the chemical industry. Since the complex interaction of fluid dynamics, mass transfer and chemical reaction is not yet fully understood, a reliable prediction of yield and selectivity is not possible. Within this work different benchmark experiments are developed, allowing the investigation of the interplay of mixing and chemical reactions. For precise predictions of the chemical process, a detailed knowledge about the intrinsic kinetics is essential. Therefore, the guiding measure “SuperFocus Mixer” (SFM) has been developed and successfully tested by determining the kinetics of a model system and of the oxidation of a temperature sensitive copper complex. In a second step, the identified reaction is transferred into the Taylor bubble setup, marking the second benchmark system. Here the effect of mixing on the production of the products in consecutive and competitive-consecutive reaction is investigated. The conducted experiments show significant influence of the mixing intensity on the production of the first reaction product MNIC and the side product DNIC, favoring the first product at intensified mixing. Finally, the local mass transfer at freely ascending bubbles superimposed by a chemical reaction is determined by applying planar-LIF, and the influence of bubble–bubble bouncing is quantified. In addition, a novel method, the Time Resolved Scanning-LaserInduced Fluorescence (TRS-LIF) for the visualization of 3D concentration fields, is introduced and tested at single rising oxygen bubbles.