Plenary Lecture

TWO-PHASE FLOW IN FUEL CELLS

 


Dr. Ned Djilali
Professor and Canada Research Chair
Department of Mechanical Engineering and
Institute for Integrated Energy Systems (IESVic)
University of Victoria
P.O. Box 3055, Victoria,
BC V8W 3P6
Canada
Phone: (250) 721-6034 Fax: (250) 721-6323
E-mail: ndjilali@uvic.ca
Web page: http://www.me.uvic.ca/~ndjilali  

Abstract: Polymer Electrolyte Membrane (PEM) Fuel Cells have emerged as one of the most promising energy conversion technologies to help mitigate pollution and green house gas emissions. The effective operation of a PEM fuel cell depends on the optimized regulation of the flow of reactant gases, product water, heat and charged species in conjunction with reaction kinetics. The coupling of these processes and the diversity of media and materials used in fuel cells give rise to a fascinating and challenging array of transport phenomena problems. The formation, phase change and transport of water play a particularly prominent role in determining performance and durability of fuel cells. Net water balance is primarily determined by the water production rate at the cathode, and transport across the membrane via diffusion and electro-osmotic drag. At higher currents, excessive water condensation can lead to “flooding” of the porous electrodes. The resulting blockage of transport pathways for reactant gases can lead to severe performance losses. Excess liquid water often appears in the cathode gas flow micro-channels as well, leading to partial coverage of the gas channel/electrode interface, increased pressure drop, and flow maldistribution. In this talk, we will focus on fundamental aspects of two-phase flow in the micro-channels and in the porous electrodes of fuel cells. The two-phase flow regimes encountered in PEM fuel cells differ significantly from the well documented two-phase flows encountered in more classical engineering applications. Some of the distinguishing features are the fibrous structure of the porous electrodes, the important role of surface forces, and hydrophobicity. Numerical simulations and quantitative visualization experiments will be presented to characterize the liquid water transport processes relevant to PEM fuel cells, and the use of pore network and volume-of-fluid simulation results towards determining some of the macroscopic parameters required for model closure will be discussed. 
 

Brief Biography of the Speaker:
After a stint in Industry as an Aerodynamicist, Ned Djilali joined the University of Victoria in 1991 where he applied his expertise in fluid dynamics, transport phenomena and computational modelling to an array of research problems including complex turbulent flows, crystal growth of semi-conductors, novel water purification technology, and energy systems. A major thrust of his research in the last ten years has been fuel cell technology. Djilali is internationally recognized for his pioneering research in computational modelling and design of fuel cells, and for furthering fundamental understanding of the complex fluid, heat and electrochemical processes that take place in this promising clean energy technology. He has consulted and collaborated extensively with industry leaders on the development of state-of-the-art modelling tools and their use in innovative design. Djilali has served as Director of UVic’s Institute for Integrated Energy Systems, and has represented UVic on a number of provincial and national strategic R&D initiatives. He has published over 200 papers and book chapters, many of which are highly cited, and holds five patents and several awards, including a Fellowship of the Canadian Society for Mechanical Engineering, the Ludwig Mond Prize from the Institution of Mechanical Engineers, The President’s Research Award and the Outstanding Teacher Award of the Engineering Institute of Canada (VI Branch). Djilali served as President of the CFD Society of Canada, and on several editorial boards, including those of the ASME Journal of Fuel Cell Science and Technology and the International Journal of Hydrogen Energy. He currently holds the Canada Research Chair in Energy Systems Design and Computational Modelling at the University of Victoria.