Experimental validation of two-phase pressure drop multiplier as a diagnostic tool for characterizing PEM fuel cell performance

Banerjee, Rupak; Howe, Danielle; Mejia, Valentina; Kandlikar, Satish G.

doi:10.1016/j.ijhydene.2014.08.118

Cited by 43 publications

(17 citation statements)

References 46 publications

(42 reference statements)

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“…We note that the two-phase multiplier decreases with increase in current density. This has been observed in previous studies, 6,24,35,50,51 and has been attributed to the increase in air velocity with increasing current density, which results in the change in flow patterns with increasing gas velocities. The phenomenon is observed because with increasing current density, there is an increase in both the gas flow rate (due to increased reactant consumption and a constant stoichiometric ratio being maintained) and the water flow rate (increased water generation).…”

Section: Validation Studiessupporting

confidence: 75%

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Modeling Two-Phase Pressure Drop along PEM Fuel Cell Reactant Channels

Kandlikar

See

Banerjee

2015

J. Electrochem. Soc.

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A 1-D down-the-channel two-phase pressure drop modeling scheme has been developed for predicting pressure drop in PEM fuel cell reactant channels. The model is based on local conditions taking into account continuous reactant consumption, water production, membrane transport and change in local saturation conditions along the flow direction. The channel is divided into discrete elements in the flow direction, and a step-wise marching scheme is employed to determine the local air and water flow rates, and local saturation condition. The model is validated using ex situ and in situ experimental data obtained over a range of operating conditions, typical of automotive fuel cell operation. The current density (0.1-1.0 A/cm 2 ), inlet humidity (0, 50 and 95% RH) and stoichiometry (1.5-8) are systematically varied to study the fuel cell pressure drop response for a total of 198 operating conditions. The modified form of the correlation proposed by English and Kandlikar has been shown to provide the most accurate pressure drop predictions. The two-phase pressure drop on the cathode side can be predicted with a mean deviation of 11.6% using the proposed scheme.Reactant gases flowing in the gas channels of Proton Exchange Membrane (PEM) fuel cells interact with the water being generated as part of the reaction and condensation from the stream, resulting in two-phase flow in the channels. Overall size restrictions on the fuel cells required to meet the US -Department of Energy (US -DOE) targets for volumetric power density (640 W/L) result in the use of minichannels, with hydraulic diameters on the order of 500 μm 1 . The two-phase flow configuration in the reactant channels of PEM fuel cells is unique in several ways. The channels are bound on one side by the gas diffusion layer (GDL), which is a porous medium with very high hydrophobicity (contact angles in the range of 110 • -140 • ). Whereas all the two-phase flow studies have been conducted with uniform gas and liquid flows through the length of the channel, in PEM reactant channels, water is introduced continuously along the length of the channel and the reactant gas is consumed along the length. This results in a continuous change in both air and water flow rates on the cathode side. The local quality (gas flow fraction) thus changes in response to changes in the flow rates. In addition, the water transport across the membrane from anode to cathode side and local evaporation or condensation of water causes changes in the water present in liquid form due to varying saturation along the flow length.Understanding the two-phase flow is important for improvement of reactant distribution (flow patterns) and pressure drop prediction. The channel pressure drop directly influences the pumping power required to supply the reactants. Any additional parasitic power (such as an increase in pumping power) results in the reduction of system efficiency. Bosco and Fronk 2 showed a direct link between the pressure drop and the overall cell performance through the cost and sizing of f...

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Section: Validation Studiessupporting

confidence: 75%

“…6 This is due to the change in flow patterns which have a direct effect on the resistance offered to the gas flow through the channel. Therefore, it is important to use the separated flow model (Lockhart and Martinelli approach shown in Eqs.…”

Section: Validation Studiesmentioning

confidence: 99%

Modeling Two-Phase Pressure Drop along PEM Fuel Cell Reactant Channels

Kandlikar

See

Banerjee

2015

J. Electrochem. Soc.

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“…At an operating current density of 1.5 A • cm −2 , Chevalier et al [66] observed an increase in peak local liquid water saturation from <5% to 86% when the cathode RH was varied from 25% to 100%. In addition to the direct studies of GDL water mentioned above, numerous studies have studied PEM fuel cell liquid water accumulation in the channels via direct visualization or measurement of pressure drop [26][27][28][67][68][69][70][71][72][73]. In the studies by Banerjee et al [67], Hussaini and Wang [68] and Spernjak et al [27], increases in the inlet reactant gas RH were observed to increase the presence of liquid water in the channels.…”

Section: Effect Of Reactant Gas Relative Humidity (Rh)mentioning

confidence: 99%

Liquid water saturation and oxygen transport resistance in polymer electrolyte membrane fuel cell gas diffusion layers

Muirhead

Banerjee

George

et al. 2018

Electrochimica Acta

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In this thesis, the relative humidity (RH) of the cathode reactant gas was investigated as a factor which influences gas diffusion layer (GDL) liquid water accumulation and mass transport-related efficiency losses over a range of operating current densities in a polymer electrolyte membrane (PEM) fuel cell. Limiting current measurements were used to characterize fuel cell oxygen transport resistance while simultaneous measurements of liquid water accumulation were conducted using synchrotron X-ray radiography. GDL porosity distributions were characterized with micro-computed tomography (μCT). The work presented here can be used by researchers to develop improved numerical models to predict GDL liquid water accumulation and to inform the design of next-generation GDL materials to mitigate mass transport-related efficiency losses. This work also contributes an extensive set of concurrent performance and liquid water visualization data to the PEM fuel cell field that can be used for validating multiphase transport models.iii

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“…The addition of the hydrophilic layer led to enhanced membrane hydration and fuel cell performance (see also power density curves) under low humidity conditions. However, the GDL with hydrophilic coating 2 exhibited higher mass transport resistance at 2 A/cm 2 and reached a limiting current before reaching the 2.5 A/cm 2 current step. Fig.…”

Section: Effect Of Hydrophilic Coating On Membrane Resistancementioning

confidence: 95%

“…Water management in the PEM fuel cell is critical for balancing two competing needs: a) adequate hydration of the polymer electrolyte membrane for protonic conductivity, and b) preservation of oxygen mass transport pathways for fuel delivery by reducing excess water accumulation at the cathode GDL [2]. To hydrate the membrane and prevent "membrane dry-out", external humidifiers are conventionally incorporated into the fuel cell system.…”

Section: Introductionmentioning

confidence: 99%

Hydrophilic Microporous Layer Coatings for Polymer Electrolyte Membrane Fuel Cells

Shrestha¹,

Banerjee²,

Lee³

et al. 2017

Proceedings of the 4th International Conference of Fluid Flow, Heat and Mass Transfer (FFHMT'17)

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-Polymer electrolyte membrane (PEM) fuel cells are energy conversion devices that are promising components of a sustainable energy system. However, conventional fuel cells suffer from performance degradation at low humidification. To address poor performance under low humidity conditions, we investigate the effect of custom hydrophilic microporous layer (MPL) coatings on liquid water distributions in gas diffusion layers (GDLs), observed in operando using X-ray synchrotron radiography. The visualization was performed during low humidity operating conditions at 60°C, with inlet gas relative humidity (RH) of 50%. Hydrophilic MPLs were coated onto commercial hydrophobic GDLs, and electrical output and simultaneous liquid water measurements were measured, using a fuel cell test station and X-ray synchrotron radiography respectively. The hydrophilic materials showed lower values of membrane resistance (quantified by high frequency resistance) compared to the benchmark hydrophobic GDL. The relatively lower membrane resistance was attributed to improved membrane hydration under low humidity conditions. Correspondingly, the catalyst layer (CL)-MPL interface contained larger quantities of liquid water with the addition of the hydrophilic coating. However, excess liquid water at the cathode side of the GDL led to high oxygen mass transport losses at high current densities. Understanding gained from this study can be used to optimize wettability of the MPL to operate the fuel cell at low or no external humidification.

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Experimental validation of two-phase pressure drop multiplier as a diagnostic tool for characterizing PEM fuel cell performance

Cited by 43 publications

References 46 publications

Modeling Two-Phase Pressure Drop along PEM Fuel Cell Reactant Channels

Modeling Two-Phase Pressure Drop along PEM Fuel Cell Reactant Channels

Liquid water saturation and oxygen transport resistance in polymer electrolyte membrane fuel cell gas diffusion layers

Hydrophilic Microporous Layer Coatings for Polymer Electrolyte Membrane Fuel Cells

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