Water management studies in PEM fuel cells, Part I: Fuel cell design and in situ water distributions Jon P. Owejan a , Jeffrey J. Gagliardo a , Jacqueline M. Sergi b , Satish G. Kandlikar b , Thomas A. Trabold a, * a General Motors Fuel Cell Laboratory, 10 Carriage Street, Honeoye Falls, New York, USA b Rochester Institute of Technology, Department of Mechanical Engineering, Rochester, New York, USA article info Article history: Received 3 November 2008 Received in revised form 23 December 2008 Accepted 23 December 2008 Available online 23 February 2009 Keywords: PEM fuel cell Two-phase flow Neutron radiography Purge Water management abstract 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 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. ª 2009 Published by Elsevier Ltd on behalf of International Association for Hydrogen Energy. 1. Introduction Water management stands out as one of the key engineering challenges in the commercialization of hydrogen PEMFCs. Some minimum level of hydration is required to facilitate efficient ionic conductivity in the proton exchange membrane. However, excess liquid water is associated with a variety of performance and durability problems, including voltage loss at high current density due to mass transport limitations [1], voltage instability at low current density [2], unreliable start-up under freezing conditions [3], and corro- sion of the carbon in the catalyst support due to hydrogen starvation [4]. Therefore, the design of PEMFC hardware and material selection must comprehend this fine balance between too little and too much water, especially for auto- motive propulsion applications where the fuel cell can be subjected to wide variations in load demand and ambient conditions during its lifetime. As shown schematically in Fig. 1, a fuel cell supplies two reactant streams, consisting of a fuel (hydrogen, H 2 ) and an oxidant (oxygen, O 2 , usually from air) to either side of a proton exchange membrane coated with platinum-based electrode layers. Hydrogen ions pass from the anode side through the membrane while electrons must flow through an external load, thus creating electrical current. The hydrogen ions then re-combine with the electrons and oxygen on the cathode side, Abbreviations: GDL, gas diffusion layer; MEA, membrane electrode assembly; PEM, proton exchange membrane; PEMFC, proton exchange membrane fuel cell; RH, relative humidity; USDOE, United States Department of Energy. * Corresponding author. Tel.: þ1 585 624 6807; fax: þ1 585 624 6680. E-mail address: thomas.trabold@gm.com (T.A. Trabold). Available at www.sciencedirect.com journal homepage: www.elsevier.com/locate/he 0360-3199/$ – see front matter ª 2009 Published by Elsevier Ltd on behalf of International Association for Hydrogen Energy. doi:10.1016/j.ijhydene.2008.12.100 international journal of hydrogen energy 34 (2009) 3436–3444