The hydrogen and
fuel cell center
ZBT GmbH

Your Contact

Dipl.-Ing. Jens Wartmann

Head of department

Micro Systems and Fluid Mechanics

phone: +49-203-7598-3336
j.wartmann@zbt-duisburg.de
online form

Laser-Optical Flow Measurements

To analyze flow conditions in a wide range of technical applications and geometries, ZBT uses modern laser-optical measurement techniques: Laser-Doppler-Velocimetry (LDV) and Particle-Image-Veloci­metry (PIV) are non-invasive, particle-based methods that are well suited to analyse flow phenomena on small and large scales based on the measured flow velocities. Note that qualitative as well as quantitative information of the flow condition can be gained. It is possible to measure in laminar, transient as well as in turbulent flows. The flow to be investigated may be steady or unsteady. Different flow phenomena can be analysed, e.g. separation, vortical or mixing flows.

 

 

Exemplary visualizations of a measured unsteady, vortical flow in a tubing system
Flow around a CO2-bubble in the anode channel of an operated DMFC

It is also possible to measure multi-phase flows, e.g. CO2-bubbles in water-methanol at the anode of an operating Direct-methanol-fuel-cell (DMFC). Based on the measured flow velocity distribution other relevant flow parameters can be calculated (e.g. shear). Laser-optical flow measurements with LDV or PIV-technique are possible in real configu­rations; the only constriction is the implementation of an optical access. Usually, this can be achieved by the implementation of a window or a glass-tube. Alternatively, the measure­ment can be performed in a representative model, as long as the relevant fluid mechanical analogy is ensured. ZBT can provide the necessary expertise, consulting services and the manufacturing of measurement models. Given the appropriate technical modifications and data-treatment also three-dimensional flow phenomena may be measured, visualized and analyzed. LDV and PIV-measurements can be performed in the laser-lab at ZBT as well as on-site, if the necessary laser safety can be assured.

Example of flow measurements in the manifold of a fuel cell stack with optical access: visualization of the velocity profile
Streamline visualization of a measured three-dimensional Dean vortex in the micro-channel of a fuel cell
Illustration of the measurement principle of µPIV applied to the flow in a micro-channel

ZBT is one of the few organizations in Germany that has the appropriate technique for small scale flow-measurements at its disposal, i.e. µPIV, which allows for measurements of flows in geometries of µm to mm size, based on a modified microscope. This special technique is best suited for the analysis of, e.g. flows within the micro-channels of fuel cells, micro-mixers in micro process engineering or flows in life-science applications (Lab-on-a-chip).

ZBT uses these laser-optical measurement techniques to analyze flow conditions in fuel cells and related subjects. In cooperation with research partners, these measurement tech­niques are modified and enhanced. E.g. based on such a modification the coherence of CO2-bubbles in water-methanol at the anode of an operated DMFC with the instantaneous cell-power could be analyzed. To investigate gas-flows in micro-channels by means of µPIV, a special technique for seeding the flow with liquid, fluorescent droplets has been developed. This allowed for gas-flow measurements of the cathode of an operating fuel cell at conditions where liquid water is formed in the channels.

Laser-lab at ZBT

At ZBT, CFD-competences are closely connected to the experimentally gained findings of flow phenomena to analyse and optimize processes and apparatus. As a non-profit limited company for industry-related research and development ZBT supports industry by means of (laser-optical) flow measurements and CFD-simulations.

Applications

  • Development of flow geometries for fuel cells, electrolysis, zinc-slurry batteries etc. (flowfield, manifold etc.)
  • Analysis of sprays, e.g. for cooling, aerosol generation etc.
  • Analysis of cooling flows, e.g. air or water cooling of fuel cell stacks
  • Analysis of multi-phase flows, e.g. on the anode or the cathode of a DMFC/PEMFC
  • Analysis of mixing processes, e.g. in reformer systems, process engineering

Further details on these measurement techniques and their application to fuel cells can be found in:

Lindken, R. & Burgmann, S.: Laser-optical methods for transport studies in low temperature fuel cells in: Hartnig, C. & Roth, C. (Eds.) Polymer electrolyte membrane and direct methanol fuel cell technology, Volume 2: In situ characterization techniques for low temperature fuel cells, Sawston, Cambridge: Woodhead Publishing Limited, 2012, 425–461

Examples

PIV-measurements in a particle-filtration system; courtesy of Palas GmbH
LDV-measurements in a modified tubing system with obstacles and a window; courtesy of ILA GmbH
µPIV-measurement in a micro-mixer; courtesy of institute for micro process engineering at KIT
Flow measurements in a modified chloralkali electrolysis-cell; courtesy of ThyssenKrupp Electrolysis GmbH, ThyssenKrupp Industrial Solutions AG and CABB GmbH
Last update:  31.08.2016