Home > Publications database > Two-phase Flow in Porous Transport Layers of Polymer Electrolyte Membrane Electrolysers |
Book/Dissertation / PhD Thesis | FZJ-2021-03290 |
2021
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag
Jülich
ISBN: 978-3-95806-564-2
Please use a persistent id in citations: http://hdl.handle.net/2128/28716 urn:nbn:de:0001-2021093016
Abstract: Polymer electrolyte membrane (PEM) water electrolysis is an important technology for the electrochemical splitting of water. Inside PEM electrolysers, the porous transportlayers (PTL) facilitate mass-transport and electric conduction. An understanding of the gas-water flow inside the PTL is a prerequisite to improving cell performance. To the best of the author’s knowledge, experimentally measured relative permeability of PEM electrolyser PTLs has not yet been published in literature. This thesis aims to achieve this through experiments and to validate results from simulations. For experimental characterisation, six different PTLs were chosen, and similar techniques for measurements of geological samples were considered. However, their microscale size presents unique challenges in applying these techniques directly. Hence, a new test cell was developed, and both absolute, and relative permeability were determined. Computer tomography (CT) images were taken for all six samples to generate 3D-models of the porous PTL structures. The flow simulations were performed using four different tools: pore network model (OpenPNM), voxel-based computation (GeoDict), conventional computational fluid dynamics (ANSYS Fluent), and Lattice Boltzmann method (Palabos). Two-phase flow simulations were performed only with OpenPNM and ANSYS Fluent. Out of the four methods, GeoDict and Palabos required the minimum amount of preprocessing. Pore network method was the least computationally expensive method. ANSYS Fluent required the most amount of preprocessing and computation time. Three-dimensional meshes were created using different open-source and proprietary tools, but only a relatively small portion of the image stack could be used due to computational limitations. GeoDict and Palabos produced nearly identical results. Except for ANSYS Fluent, all the other tools computed through-plane permeability values close to experimental values. The simulations did not match the experimental in-plane permeability values. Relative permeability was computed from pore network simulations. Computed air relative permeability curves and the respective measurements agreed. The water relative permeability curves did not match experiments, although both were very small in magnitude. It is observed that relative permeability saturation correlations used in literature are not experimentally validated. This work produced experimental relative permeability curves for sintered titanium porous transport layers of PEM electrolyser systems for the first time.
The record appears in these collections: |