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@INPROCEEDINGS{CHENG:1022605,
      author       = {CHENG, TIANLIANG and Beale, Steven and Kadyk, Thomas and
                      Eikerling, Michael},
      title        = {{CFD} modeling of a {PEM} water electrolyzer: relationship
                      between flow regime number and performance},
      reportid     = {FZJ-2024-01571},
      year         = {2023},
      abstract     = {The relationships between operating conditions, two-phase
                      flow regime in the anode channel, and performance of a
                      polymer electrolyte membrane water electrolyzer (PEMWE) is
                      not well understood. These relationships are important for
                      optimizing cell operation in view of power consumption and
                      stability. To address this issue, a model for the interplay
                      of the relative velocity between the two phases and the
                      bubble diameter in the anode channel is developed. It
                      accounts for the effect of current density on the bubble
                      diameter using fitting to experimental data as input [1].
                      This model is coupled with the electro-chemical kinetics in
                      catalyst layers to perform 3-D computational fluid dynamics
                      (CFD) simulations of a PEMWE (Fig. 1) in the open-source
                      platform OpenFOAM. The operating point is defined by the
                      average area current density i, and the water stoichiometry
                      λ. The two-phase flow regime is quantified by the
                      normalized flow regime number, frn*, and the cell
                      performance is characterized by the cell voltage, U. The
                      model is compared to the experimental data of two-phase flow
                      reported in Ref. [2]. Results show that the frn* provides a
                      criterion to distinguish the three main flow regimes
                      (bubbly, plug, and slug). Simulation results help furnish
                      relationships between operating point, flow regime and cell
                      performance. The best cell performance (lowest cell voltage)
                      is found to occur at the highest water stoichiometry, λ =
                      1000, in simulations, where the bubbly flow regime prevails
                      for current densities from 0.1 A/cm2 to 2.0 A/cm2. Slug flow
                      with the highest value of frn* appears at 0.8 A/cm2 with the
                      lowest water stoichiometry 100 (Fig. 2) due to the high
                      oxygen volume fraction. Among other findings, it
                      demonstrates that the water stoichiometry should be
                      increased to decrease cell voltage and oxygen bubble sizes
                      in the anode channel. This work provides important basic
                      trends and limiting values for cell operation.},
      month         = {Mar},
      date          = {2023-03-21},
      organization  = {19th Symposium on Fuel Cell and
                       Battery Modeling and Experimental
                       Validation, Duisburg (Germany), 21 Mar
                       2023 - 23 Mar 2023},
      subtyp        = {After Call},
      cin          = {IEK-13 / IEK-14},
      cid          = {I:(DE-Juel1)IEK-13-20190226 / I:(DE-Juel1)IEK-14-20191129},
      pnm          = {1231 - Electrochemistry for Hydrogen (POF4-123)},
      pid          = {G:(DE-HGF)POF4-1231},
      typ          = {PUB:(DE-HGF)6},
      doi          = {10.34734/FZJ-2024-01571},
      url          = {https://juser.fz-juelich.de/record/1022605},
}