PhD Dissertation Defense by Logan Battrell, Chemical & Biological Engineering
- Tuesday, November 13, 2018 from 1:00pm to 2:00pm
- Barnard Hall, 126 - view map
Analysis of Water Transport Phenomena in Thin Porous Media of a Polymer Electrolyte Membrane Fuel Cell
Abstract: Polymer electrolyte membrane fuel cells (PEMFCs) are a promising green energy conversion technology that have been imagined as a focal point for a hydrogen-based power supply. Their main attractive qualities include zero local greenhouse gas emissions, high power density, and scalability. This thesis explores and quantifies water transport associated with the desaturation of the thin porous layer known as the Gas Diffusion Layer (GDL) associated with PEMFCs. The proper management of water within this layer is critical to optimal fuel cell performance, if there is not enough water, the membrane can become dehydrated, which leads to poor cell performance, but if too much water accumulates or becomes flooded, gas transport is restricted, which also lowers performance and can potentially lead to total cell failure. Understanding the desaturation of this layer is thus key to obtaining and maintaining optimal fuel cell performance. This behavior is explored both at the macro-scale, through the quantification of the removal of excess water from an active fuel cell, as well as at the micro-scale, through the use of synchrotron X-ray computed tomography (X-ray CT) to visualize and quantify the desaturation of an initially flooded GDL. The macro-scale investigation extends the previously developed qualitative Anode Water Removal (AWR) test, which functions to identify when poor PEM fuel cell performance is due to excess water, to a diagnostic protocol that quantifies the amount of water being removed by the test through an analysis of the anode pressure drop. Results show that the protocol can be applied to a variety of fuel cell setups and can be used to quickly quantify water management capabilities of novel GDL materials. The micro-scale investigations show that while both convection and evaporation play a role in the desaturation, evaporation is required to fully desaturate the GDL. Additionally, the micro-scale investigation allows for the spatial segmentation of the GDL to identify local desaturation rates and temporal saturation profiles, which show that the overall desaturation of the GDL is a heterogeneous process that depends on initial conditions, flow field geometry and the natural anisotropy of the material.
- Department of Chemical and Biological Engineering