Innovative µ-PIV measurement technique for film flow investigations
Advancing the chemical engineering fundamentals
Multifase Flows - II (T2-5b)
Keywords: Micro-PIV measurements, film flow, CFD simulation, validation, 3D velocity profile
S. Paschke * Paschke@dynamik.fb10.Tu-Berlin.de
I. Ausner* Ilja.Ausner@TU-Berlin.de
J.-U. Repke* jens-uwe.repke@TU-berlin.de
G. Wozny* guenter.wozny@TU-berlin.de
*TU Berlin, Institute of Process and Plant Technology, Strasse des 17. Juni 135 – KWT 9, 10623 Berlin, Germany
In a multitude of process engineering applications film flows can be found, e.g. in packed columns for distillation and absorption or falling-film evaporators. It was found that e.g. the separation efficiency of such processes strongly depends on the hydrodynamics of the liquid flow behavior. For prediction of the flow behavior and the design of film flow apparatus, a detailed knowledge of the fluid dynamic on the surface in dependence on the process and system parameters is urgently required. With the aid of CFD simulations it is possible to investigate the flow behavior inside complex geometries with insignificant effort compared to measurements. However, it is necessary to validate the CFD simulations with accurate measurements.
The liquid phase inside film flow apparatus mainly flows as film flow or after break-up as rivulet and droplet flow often on strongly corrugated surfaces. With the additional formation of waves on the liquid surface, the flow behavior becomes very complex. Therefore, researchers of previous studies have investigated the liquid flow from the backside through a transparent wall in order to avoid reflection and refraction effects due to the wavy vapor-liquid interface. However, the transparent wall material is different to materials, which are used in industrial applications, and with that the flow properties like liquid spreading can be changed.
For this application, a new micro Particle Image Velocimetry (µ-PIV) method is developed and will be presented in this contribution. This method enables the measurement of a three dimensional velocity field from the top side of the flow through the wavy interface. First measurements are carried out from the top side and from behind through a transparent glass wall with water-glycerol mixtures at different Reynolds numbers. A comparison of the velocity profiles for the different cases shows that this new measurement technique is feasible. Consequently, flow investigations on industrially used wall materials like stainless steel are carried out.
Further measurements are conducted with water-glycerol on a flat inclined stainless steel plate under different Reynolds numbers. The results are compared with own CFD simulations as well as other correlations published in the literature. The comparison of the three-dimensional velocity field shows good agreements and leads to further investigations in more complex geometries. With that, the fundamentals are formed for the better understanding of multiphase flow processes, e.g. three-phase flows in packed columns [1].
[1] J.-U. Repke, I. Ausner, S. Paschke , A. Hoffmann, G. Wozny: On the track of understanding three phases in one tower. Chem. Eng. Res. Des., in press
Presented Monday 17, 15:00 to 15:20, in session Multifase Flows - II (T2-5b).
