Project Details
Projekt
Modeling of the electrolyte distribution in representative volumes
Applicant
Professor Dr.-Ing. Ulrich Nieken
Subject Area
Chemical and Thermal Process Engineering
Term
from 2016 to 2023
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 276655287
In the first project phase we could show that it is possible to simulate the penetration of an electrolyte into a gas diffusion electrode on the pore scale. A particular difficulty is the description of the mixed wetting behavior. While the silver phase is wetted by the electrolyte, the PTFE part is strongly hydrophobic and prevents the penetration of the electrolyte. The phase boundary may get in contact with both, electrolyte and PTFE. The numerical effort is very high, therefore only small volumens of the real structure could be considered. Simulation results suggest that the electrolyte exhibits fingering behaviour and forms strongly fractal structures.The goal for the second funding period is to simulate the electrolyte distribution in volumes that can be considered representative. For this purpose, a hybrid calculation method is proposed. The vicinity of the free phase boundaries will be rigorously calculated, while the flow of the electrolyte through filled pores is simplified and modelled as flow resistances. A speed up of the calculation shall be achieved by a fully implicit time integration for the SPH simulation on the one hand, and by parallel calculations of the moving phase boundaries on the other hand.From preliminary measurements it is known that an electric potential leads to a better wetting of the silver phase by the electrolyte. This behaviour, known as "electrowetting", will be considered in the second funding period for the simulation of the electrolyte distribution.In order to validate the model, capillary pressure saturation measurements on GDE’s will be carried out, whereby the electric potential is varied. This allows the comparison of the integral electrolyte holdup with the simulated holdup. Spatially resolved measurements of the electrolyte distribution by the AK Manke allows a detailed validation on the pore scale.
DFG Programme
Research Units
