Statistische Analyse des lokalen Wassertransportes einer Polymer‐Elektrolyt‐Brennstoffzelle

Abstract

Der Wassertransport in der Gasdiffusionsschicht (gas diffusion layer, GDL) einer Polymer-Elektrolyt-Brennstoffzelle (PEFC) wurde mithilfe der Lattice-Boltzmann-Methode simuliert. Mit einem stochastischen Geometriemodell wurde ein Ensemble von Mikrostrukturen generiert, die alle stochastisch äquivalent zur realen Struktur einer GDL sind. Die raue Oberfläche der GDL bildet das Interface zwischen GDL und Luftkanal einer PEFC. Die aus der GDL austretenden Wassertropfen wurden hinsichtlich ihrer Kontaktwinkel analysiert und kurz der dynamische Verlauf betrachtet.The water transport in the gas diffusion layer (GDL) of a polymer electrolyte fuel cell (PEFC) was simulated using the Lattice Boltzmann method. By means of a stochastic geometry model an ensemble of microstructures was generated, all of them stochastically equivalent to the real structure of a GDL. The rough surface of the GDL defines the interface between the GDL and air channel of a PEFC. The water droplets emerging from the GDL were analyzed statistically regarding their contact angles. A short insight to the dynamics is given.

Inhomogeneous Distribution of Polytetrafluorethylene in Gas Diffusion Layers of Polymer Electrolyte Fuel Cells

“…For this reason, the one-sided inhomogeneous global PTFE distribution was chosen as the best option for the next step. Because the previous simulations were based on fully PTFE-covered fibers, the PTFE distribution of configuration D.8 (with 8% PTFE) is completed with configuration F. Configuration F is the same as D -not re-calculated but exactly the same local distribution-with additional PTFE upon the uppermost GDL layer to create a situation close to previous simulations with regard to contact angles (Yu et al 2018a;Froning et al 2019).…”

“…Mortazavi and Tajiri (2013) measured contact angles on the surface of Toray GDL. While the conditions of their measurements and simulations by Yu et al (2018a) and Froning et al (2019) differ, the resulting contact angles are in a fairly similar range. For this reason, the one-sided inhomogeneous global PTFE distribution was chosen as the best option for the next step.…”

“…Every configuration from Table 2 was chosen with 8% PTFE, while configuration D was also evaluated with 6% PTFE in the micro-structure. As in previous studies (Yu et al 2018a(Yu et al , 2019Froning et al 2019), transport simulations were run for 60,000 time steps. Within this period, droplets emerged from the upper surface of the GDL after the liquid water was transported through the porous structure.…”

“…The second property to be analyzed is the contact angle. The shape of the droplets leaving the GDL was characterized by their contact angles which were calculated using the sub-pixel polynomial fitting (SPPF) method as introduced by Yu et al (2018a) and Froning et al (2019).…”

“…Lin et al (2019) demonstrated experimentally the relevance of contact angles for fuel cell efficiency. Meanwhile, Yu et al (2018a) and Froning et al (2019) simulated liquid transport in GDL using the LB method and presented statistical distributions of contact angles, mainly influenced by the irregular geometry of the individual pores. The contact angles of fresh and aged GDLs on the anode and cathode sides of a fuel cell were measured by Planes et al (2018).…”