Development of two-phase flow regime specific pressure drop models for proton exchange membrane fuel cells

Anderson, Ryan; Eggleton, Erica; Zhang, Lifeng

doi:10.1016/j.ijhydene.2014.11.032

Cited by 27 publications

(7 citation statements)

References 43 publications

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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%

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%

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

Kandlikar

See

Banerjee

2015

J. Electrochem. Soc.

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“…According to past studies, [40][41][42] at a higher back pressure, both the entire performance 40 and local performance 42 of the cell increased and efficiency of the cell was improved. 41 In this study, the effectiveness of backpressure on internal current is further investigated during shutdowns under various operating conditions.…”

Section: Effect Of Cathode Backpressurementioning

confidence: 96%

Dynamic characteristics of internal current during startups/shutdowns in proton exchange membrane fuel cells

2019

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Summary Studying dynamic characteristics of proton exchange membrane fuel cells (PEMFCs) during startups/shutdowns is of great importance to proposing strategies to improve fuel cell performance and durability. In this study, internal current during startup and shutdown processes in PEMFC is investigated, and effects of gas supply/shutoff sequences and backpressure are analyzed by measuring local current densities and the cell voltage in situ. The experimental results show that when reactants were fed/shut off, internal current occurs and variation patterns of local current densities along the flow channel are different. During startups, local current densities in the downstream drop to negative values and internal current can be eliminated when air is first supplied into the cell. While during shutdowns, the results show that negative currents occur in the upstream, and if hydrogen is shut off first, all local current densities remain constant at zero, indicating the effectiveness of gas shutoff sequence in eliminating/mitigating internal current in PEM fuel cells. Further experimental results show that the magnitude of internal current increases with the pressure difference between the anode and the cathode.

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“…Water and airflow rates varied in a microchannel model of a PEMFC showed a transition from slug to droplet (5 m s –1 ) to film flow (30 m s –1 ) as the velocity increases. Other regime maps have shown the transition between slug, droplet, and film flow to exist between 1 and 3 m s –1 . ,, …”

Section: Introductionmentioning

confidence: 99%

“…Two-phase flow in channels is encountered in other applications, including PEWE and boiling heat transfer in microheat exchangers used to cool electronic equipment. , During PEFC operation, air and water have orders of magnitude difference in velocity. To characterize the effect of these variables on the flow pattern, two-phase flow regime maps for PEFC have been developed. − However, quantitative data are difficult to obtain from the reflective materials of the GDL and water, including the two-dimensional view in transparent operating fuel cells. , …”

Section: Introductionmentioning

confidence: 99%

Discrete-Particle Model to Optimize Operational Conditions of Proton-Exchange Membrane Fuel-Cell Gas Channels

Niblett

Holmes

Niasar

2021

ACS Appl. Energy Mater.

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Operation of proton-exchange membrane fuel cells is highly deteriorated by mass transfer loss, which is a result of spatial and temporal interaction between airflow, water flow, channel geometry, and its wettability. Prediction of two-phase flow dynamics in gas channels is essential for the optimization of the design and operating of fuel cells. We propose a mechanistic discrete particle model (DPM) to delineate dynamic water distribution in fuel cell gas channels and optimize the operating conditions. Similar to the experimental observations, the model predicts seven types of flow regimes from isolated, side wall, corner, slug, film, and plug flow droplets for industrial temporal and spatial scales. Consequently, two-phase flow regime maps are proposed. The results suggest that an increase in water accumulation in the channel is related to the increase in the water cluster density emerging from the gas diffusion layer rather than the increased water flow rate through constant water pathways. From a modeling perspective, the DPM replicated well volume-of-fluid channel simulation results in terms of saturation, water coverage ratio, and interface locations with an estimated 5 orders of magnitude increase in calculation speed.

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Development of two-phase flow regime specific pressure drop models for proton exchange membrane fuel cells

Cited by 27 publications

References 43 publications

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

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

Dynamic characteristics of internal current during startups/shutdowns in proton exchange membrane fuel cells

Discrete-Particle Model to Optimize Operational Conditions of Proton-Exchange Membrane Fuel-Cell Gas Channels

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