Impact of channel geometry on two-phase flow in fuel cell microchannels

• Published in: Journal of power sources Vol. 196; no. 11; pp. 5012 - 5020
• Main Authors: Steinbrenner, Julie E., Lee, Eon Soo, Hidrovo, Carlos H., Eaton, John K., Goodson, Kenneth E.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.06.2011; Elsevier
• Subjects: Applied sciences; Cathodes; Channels; Current density; Direct energy conversion and energy accumulation; Electrical engineering. Electrical power engineering; Electrical power engineering; Electrochemical conversion: primary and secondary batteries, fuel cells; Energy; Energy. Thermal use of fuels; Equipments for energy generation and conversion: thermal, electrical, mechanical energy, etc; Ex situ; Exact sciences and technology; Flooding; Fluid dynamics; Fuel cells; Liquid flow; Microchannels; PEM fuel cell; Slug flow; Stratified flow; Two-phase flow; Ex situ; Flooding; Two-phase flow; Microchannels; PEM fuel cell; Two phase flow; Polymer electrolytes; Polymer solid electrolyte; Micromachine; Proton exchange membrane fuel cells; Fuel cell
• ISSN: 0378-7753; 1873-2755
• DOI: 10.1016/j.jpowsour.2011.02.032

► Ex situ setup shows flow structure transition with distributed water injection. ► Flow consistently progresses from intermittent regime to stable stratified film. ► Increased GDL hydrophobicity favors flow stratification and water evacuation. ► Flow in short, straight channels remains intermittent. ► Observations inform design of fuel cell gas delivery channels. An important function of the gas delivery channels in PEM fuel cells is the evacuation of water at the cathode. The resulting two-phase flow impedes reactant transport and causes parasitic losses. There is a need for research on two-phase flow in channels in which the phase fraction varies along the flow direction as in operating fuel cells. This work studies two-phase flow in 60 cm long channels with distributed water injection through a porous GDL wall to examine the physics of flows relevant to fuel cells. Flow regime maps based on local gas and liquid flow rates are constructed for experimental conditions corresponding to current densities between 0.5 and 2 A cm −2 and stoichiometric coefficients from 1 to 4. Flow structures transition along the length of the channel. Stratified flow occurs at high liquid flow rates, while intermittent slug flow occurs at low liquid flow rates. The prevalence of stratified flow in these serpentine channels is discussed in relation to water removal mechanisms in the cathode channels of PEM fuel cells. Corners facilitate formation of liquid films in the channel, but may reduce the water-evacuation capability. This analysis informs design guidelines for gas delivery microchannels for fuel cells.