Spatially resolved measurement of transient concentration and temperature fields using Schlieren and LIF technique
Final Report Abstract
The project dealt with the quantitative determination of local and transient concentration and temperature fields near interfaces. These fields determine the occurring mass or energy transport and were quantified optically using the Schlieren technique. This measurement technique allows a nearly instantaneous, two-dimensional examination of the measurement volume. From the obtained images, the transfer coefficients can be determined non-invasively as well as space- and time-resolved. As a result, it is possible to elucidate transient behavior during mass transfer processes. This behavior has not yet been sufficiently taken into account for the design of contact apparatuses, which up to now depends on the availability of purely integral empirical equations. An example of transient interfacial phenomena is Marangoni convection, which influences the mass transfer at quiescent single droplets. The consideration of these influences opens up great potential for optimizing apparatus design and helps to gain a deeper understanding of the basics of mass transfer processes. In addition, the measurements provide accurate experimental data to validate numerical approaches and improve predictions. As part of the measurements, transport coefficients at different geometries were determined. Initially, energy transport on self-constructed test specimens was measured since the use of temperature fields allowed better reproducibility and enabled a reliable validation of the measuring procedure. In the context of this validation process, an algorithm for automated analysis of spherical fields was implemented. Based on this, concentration fields near planar surfaces and single droplets were examined. For single droplets, liquid/liquid systems without interfacial instabilities were investigated before systems with interfacial instabilities. An important part of the project was the development of the measurement setup with regard to measurement accuracy and reliability. Here, improvements in hardware and software, such as the integration of a linear guide for more precise filter positioning and the use of advanced image processing methods, were implemented. Due to the first-time use of the Schlieren technique for the quantitative determination of liquid/liquid mass transport, several validation steps were carried out. Laser Induced Fluorescence (LIF) was used to experimentally validate the Schlieren data. Additionally, measurement data were numerically validated using Computational Fluid Dynamics (CFD) and ray tracing calculations. Ray tracing calculations also provided the opportunity to check the accuracy and sensitivity of the Schlieren measurements. Finally, the construction of a second optical axis enabled the validation of assumptions made about the refractive index field. Furthermore, the use of a second optical axis served as the starting point for the analysis of irregularly shaped concentration fields as they occurred during interfacial instabilities.
Publications
-
Development of an experimental setup applying rainbow schlieren deflectometry for visualization and quantification of heat and mass transfer in multiphase systems in Proceedings of the 5th International Conference on Experimental Fluid Mechanics ICEFM 2018 Munich, Kähler, C. and Hain, R. and Scharnowski, S. and Fuchs, T., Eds. 226-231.
Schulz, Joschka M.; Junne, Henning; Böhm, Lutz & Kraume, Matthias
-
Measuring local heat transfer by application of Rainbow Schlieren Deflectometry in case of different symmetric conditions. Experimental Thermal and Fluid Science, 110, 109887.
Schulz, Joschka M.; Junne, Henning; Böhm, Lutz & Kraume, Matthias
-
Ortsaufgelöste Messung von Konzentrations- und Temperaturfeldern mittels Schlieren und LIF-Messtechnik. Jahrestreffen der ProcessNet-Fachguppen Fluidverfahrenstechnik, Adsorption und Extraktion 2020, Berchtesgarden, Germany. (Präsentation)
Junne, H., Schulz, J., Böhm, L. & Kraume, M.
-
Real‐Time Visualization of Internal and External Concentration Fields in Multiphase Systems via Laser‐induced Fluorescence and Rainbow Schlieren Deflectometry During and After Droplet Production. Chemie Ingenieur Technik, 93(1-2), 180-190.
Heine, Jens Stefan; Schulz, Joschka Marco; Junne, Henning; Böhm, Lutz; Kraume, Matthias & Bart, Hans‐Jörg
-
Spatially resolved measurement of concentration and temperature fields using Schlieren technique. 4th International Symposium on Multiscale Multiphase Process Engineering, Berlin, Germany. (Poster)
Junne H., Böhm L. & Kraume M.
-
Rainbow Schlieren Deflectometry for spherical fields: A new algorithm and numerical validation approach. Numerical Heat Transfer, Part B: Fundamentals, 85(9), 1178-1201.
Junne, Henning; Jurtz, Nico; Schulz, Joschka M.; Kraume, Matthias & Böhm, Lutz
-
Validierung eines neuen Algorithmus zur Bestimmung sphärischer Brechungsindexfelder mittels freier Konvektion. Jahrestreffen der ProcessNet-Fachgruppen Computational Fluid Dynamics und Wärme- und Stoffübertragung, Frankfurt a.M., Germany. (Präsentation)
Junne H., Jurtz N., Böhm L. & Kraume M.
