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@PHDTHESIS{Renz:1041605,
      author       = {Renz, Stefanie},
      title        = {{M}ethodological {A}pproach {E}nabling the {T}wo-phase
                      {F}low {I}nvestigation in {A}lkaline {E}lectrolysis under
                      {D}emanding {C}onditions},
      volume       = {661},
      school       = {RWTH Aachen University},
      type         = {Dissertation},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {FZJ-2025-02339},
      isbn         = {978-3-95806-821-6},
      series       = {Schriften des Forschungszentrums Jülich Reihe Energie $\&$
                      Umwelt / Energy $\&$ Environment},
      pages        = {IX, 252},
      year         = {2025},
      note         = {Dissertation, RWTH Aachen University, 2024},
      abstract     = {In this examination, a methodological approach is developed
                      for the investigation of the two-phase flow behavior of an
                      alkaline electrolysis cell using multiphase particle image
                      velocimetry. Typically, imaging techniques or transparent
                      cells are used to investigate the gas bubble behavior inside
                      electrochemical cells. Certain drawbacks of these methods
                      urge the necessity for a universally applicable two-phase
                      flow investigation method for alkaline electrolysis cells.
                      Therefore, a method is developed which is able to
                      investigate both phases (liquid and gaseous) using a
                      transparent half-cell. The half cell is capable of
                      simulating the alkaline electrolysis two-phase flow behavior
                      on anode or cathode side separately. By exchanging the
                      electrolyte solution for a model electrolyte solution with
                      the same density and viscosity as potassium hydroxide, the
                      two-phase flow investigation can be done at lower
                      temperatures than the usual alkaline electrolysis operation
                      temperature. This is especially advantageous at temperatures
                      above boiling point where pressurized operation is necessary
                      because, with the proposed measurement method, the necessity
                      of operating the electrolysis cell under pressure is
                      avoided. Additionally, the exchange of potassium hydroxide
                      to a less corrosive model electrolyte solution prevents the
                      used transparent cell from getting dull from highly
                      concentrated lye. The simulated cell is operated with
                      equivalent volumes of nitrogen gas instead of hydrogen and
                      oxygen for safety reasons. For method validation, the NeXT
                      (Neutron and X-Ray Tomograph) device at Institute
                      Laue-Langevin (ILL) in Grenoble is used to observe the gas
                      bubbles forming and moving inside the flow channel of an
                      alkaline electrolysis cell. For the first time, a temporal
                      resolution of 0.02 seconds could be achieved for an active
                      cell area of several cm2. Measurement methods like neutron
                      radiography are a powerful tool to analyze the gas bubble
                      behavior inside alkaline electrolysis flow cells, but has
                      limited accessibility. For both measurement methods, neutron
                      radiography measurements and multiphase particle image
                      measurements, cells of the same flowfield geometry are used.
                      For the comparison of both investigation methods, an
                      alkaline water electrolysis single cell is operated at
                      different operation conditions. In this work, the results of
                      both measurement methods are shown and compared. The
                      applicability of an experimentally ”simulated”
                      electrolysis cell, measured with multiphase particle image
                      velocimetry measurements, is shown, as well as the
                      assumptions, prerequisites, and limitations of the
                      simulation of the two-phase flow of an alkaline electrolysis
                      cell. Using the simulated electrolysis half-cell is
                      advantageous compared to neutron radiography measurements
                      because smaller gas bubbles can be identified. Especially
                      for difficult operation conditions like in alkaline
                      electrolysis at intermediate temperatures, where
                      measurements like neutron radiography are extremely
                      difficult to realize, a flow behavior analysis method, which
                      is easy to apply, is helpful. Additionally, the flow
                      behavior of electrochemical flow cells can be optimized for
                      improved electrolysis cell designs and higher efficiencies.
                      This examination is the first step towards a simpler
                      investigation of the two-phase flow behavior of
                      electrochemical cells with the application example of a low
                      temperature alkaline electrolysis zero-gap cell, with the
                      potential to extend the method to intermediate temperature
                      alkaline electrolysis or any other electrochemical device
                      that forms gas bubbles.},
      cin          = {IET-4},
      cid          = {I:(DE-Juel1)IET-4-20191129},
      pnm          = {1231 - Electrochemistry for Hydrogen (POF4-123)},
      pid          = {G:(DE-HGF)POF4-1231},
      typ          = {PUB:(DE-HGF)3 / PUB:(DE-HGF)11},
      urn          = {urn:nbn:de:0001-2505121038103.565400670875},
      doi          = {10.34734/FZJ-2025-02339},
      url          = {https://juser.fz-juelich.de/record/1041605},
}