Jeffrey J. Gagliardo

Accumulation and Removal of Liquid Water in Proton Exchange Membrane Fuel Cells

Removal of liquid water from proton exchange membrane fuel cells is critical for efficient performance, low temperature operation, and robustness for start-up under freezing conditions. The present work investigates the three-dimensional location of liquid water during steady-state operation and the governing mechanisms that control its accumulation and removal. A combination of ex situ and in situ methods with neutron imaging diagnostics is used to investigate water transport in the bulk materials and flow field channels. These results provide experimental evidence of the mechanisms by which water vapor condenses in the anode during operation and the transport resistance for its removal during shutdown purge. Based on these results, a one-dimensional model is proposed that can be applied to calculate the effectiveness of cathode purge starting from a wide range of fuel cell shutdown conditions.

Two-Phase Flow Considerations in PEMFC Design and Operation

A proton exchange membrane fuel cell (PEMFC) must maintain a balance between the hydration level required for efficient proton transfer and excess liquid water that can impede the flow of gases to the electrodes where the reactions take place. Therefore, it is critically important to understand the two-phase flow of liquid water combined with either the co-flowing hydrogen (anode) or air (cathode) streams. In this paper, we describe the design of an in-situ test apparatus that enables investigation of two-phase channel flow within PEMFCs, including the flow of water from the porous gas diffusion layer (GDL) into the channel gas flows; the flow of water within the bipolar plate channels themselves; and the dynamics of flow through multiple channels connected to common manifolds which maintain a uniform pressure differential across all possible flow paths. These two-phase flow effects have been studied at relatively low operating temperatures under steady-state conditions and during transient air purging sequences.Copyright