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A comprehensive 2D+1 computational model has been developed to explore the operation of a polymer electrolyte fuel cell (PEFC) with a porous flow field, also called open metallic element (OME), in the ultra-high current density regime (>2A/cm 2 ). The computational model has been validated to a greater extent than previously published multi-phase models, including in-situ experimental measurement of performance, high frequency resistance (HFR) and net water drag coefficient under a wide range of input relative humidity (RH) conditions. The combined experimental and modeling investigation found that, with the OME used as the flow field, gas phase transport of oxygen is not the limiting factor, even in the ultra-high current regime. The use of OME results in significant performance improvement compared to the conventional land-channel architecture at high current. Instead of oxygen transport limitation, however, anode dry-out limits performance, as confirmed by net water drag data from both experiment and model. With the OME architecture, diffusion flow is the dominant transport mechanism of water from the catalyst layer to the flow field, compared to capillary action and convection. Results also highlight the utility of experimentally-determined anode dry-out limits for validating multi-phase models.

The current paper evaluates the thermal performance of immersion cooling for an Electric Vehicle (EV) battery module comprised of NCA-chemistry based cylindrical 21700 format Lithium-ion cells. Efficacy of immersion cooling in improving maximum cell temperature, cell’s temperature gradient, cell-to-cell temperature differential, and pressure drop in the module are investigated by direct comparison with a cold-plate-cooled battery module. Parametric analyses are performed at different module discharge C-rates and coolant flow rates to understand the sensitivity of each cooling strategy to important system performance parameters. The entire numerical analysis is performed using a validated 3D time-accurate Computational Fluid Dynamics (CFD) methodology in STAR-CCM+. Results demonstrate that immersion cooling due its higher thermal conductance leads to a lower maximum cell temperature and lower temperature gradients within the cells at high discharge rates. However, a higher rate of heat rejection and poor thermal properties of the dielectric liquid results in a much higher temperature non-uniformity across the module. At lower discharge rates, the two cooling methods show similar thermal performance. Additionally, owing to the lower viscosity and density of the considered dielectric liquid, an immersion-cooled battery module performs significantly better than the cold-plate-cooled module in terms of both coolant pressure drop.

A comprehensive 2D + 1 multi-phase computational model has been applied to polymer electrolyte fuel cells with a porous metallic flow field to investigate operating strategies which enable high power density operation in dry, elevated temperature environment. Extensive experimental model validation has been completed under a wide range of temperature, pressure, stoichiometry and humidity conditions. Both qualitative and quantitative agreement has been achieved in regard to voltage, area-specific resistance, and net water drag coefficient. Internal water distribution predictions show that modest changes in operating parameters on the cathode side help maintain a hydrated anode stream and thus effectively push the envelope of stable operating temperature 20 • C higher, enabling more efficient heat dissipation in coolant system. Results also show that thermo-osmotic water flux across the membrane, as observed and measured experimentally, can be significant compared to electro-osmosis under high current (> 2 A/cm 2 ) hot and dry conditions, even with thin electrolyte membranes.Despite dramatic reduction in polymer electrolyte fuel cell (PEFC) projected system costs, 1 some additional cost reduction is still required to achieve parity with chemical combustion-based propulsion systems. In order to make PEFCs more cost-competitive, two trajectories have been researched. In one case, attempts are made to reduce costs through innovative materials including reduced noble metal content. In another trajectory studied here, system architecture and materials are engineered to enable much greater operating current density, which reduces overall stack volume and material costs with conventional electrodes.Recent progress on flow field design have made better use of progress in material development and reached the level of current density that normally cannot be achieved by conventional design. 2-4 One example is the open metallic element (OME) porous flow field architecture demonstrated by Nuvera Fuel Cells Inc. With this architecture, a total noble metal power density of 7.3 W/mg Pt has been achieved on their single cell. 5 By direct comparison with land / channel structure, our recent publication 3 analyzed the porous flow field to a greater extent than previously-published literature 6-12 and demonstrated significant performance improvement, especially in high current density regime. Rather than flooding or oxygen mass transport limitations as in a conventional flow field, anode dehydration has been identified as the potential limiting factor preventing higher current density operation in the OME porous flow field.The delicate interplay between dehydration and flooding is the core of water management and critical not only in porous flow field. Actually it has been widely studied in conventional land / channel architecture because flooding in the catalyst layer, diffusion media, and / or flow channel is a major concern. As reviewed by Li et al., 13 both experimental and modeling efforts on flooding reduction included adjusting...