The pressure losses in the flow distributor plate of the fuel cell depend on the Reynolds number and geometric parameters of the small flow channels. Very little information has been published on the loss coefficients for laminar flow. This study reports a numerical simulation of laminar flow though single sharp and curved bends, 180° bends and serpentine channels of typical fuel cell configurations. The effect of the geometric parameters and Reynolds number on the flow pattern and the pressure loss characteristics is investigated. A three-regime correlation is developed for the excess bend loss coefficient as a function of Reynolds number, aspect ratios, curvature ratios and spacer lengths between the channels. These have been applied to calculate the pressure drop in typical proton-exchange membrane fuel cell configurations to bring out the interplay among the important geometric parameters. © 2004 Elsevier B.V. All rights reserved.

Sreenivas Jayanti

Department Of Chemical Engineering

Abhijit P. Deshpande

S. Maharudrayya

Automotive engineering

Computational fluid dynamics

Computer simulation

Energy dissipation

Flow of fluids

Laminar flow

Optimization

Pressure effects

Reynolds number

Serpentine

BEND LOSS COEFFICIENTS

DESIGN CORRELATIONS

PRESSURE LOSS

Serpentine channels

Fuel cells

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

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IIT Madras

Journal of Power Sources

For high current density operation of redox flow batteries, proper circulation of the electrolytes over the active area of the cell is important. In the present paper, we study experimentally the effect of channel dimensions of a serpentine flow field for vanadium redox flow battery applications. The study encompasses three aspects: effect on the extent of felt intrusion into the flow channels, effect on the pressure drop over a cell for a given electrolyte circulation rate, and effect on the electrochemical performance characterized by a number of parameters. Eight variants of channel and/or rib dimensions in serpentine flow fields have been studied in cells of 400 cm 2 and 900 cm 2 active area. A lumped parameter model, validated with water and electrolyte circulation data, has been developed to predict the pressure loss and flow apportionment in the cell. The results show that sensitivity to channel dimensions is more keenly felt in the larger cell with noticeable improvements in pressure drop, peak power density and discharge energy density. Increasing channel width and decreasing rib width is recommended as the ideal strategy to improve the overall performance of the cell. © 2019 Elsevier Ltd

Journal of Energy Storage

Effect of channel dimensions of serpentine flow fields on the performance of a vanadium redox flow battery

Electrolyte distribution using parallel flow field for redox flow battery (RFB) applications shows severe non-uniformity, while the conventional design of using the carbon felt itself as the flow distributor gives too high pressure drop. An optimized flow field design for uniform flow distribution at a minimal parasitic power loss is therefore needed for RFB systems. Since the materials and geometrical dimensions in RFBs are very different from those used in fuel cells, the hydrodynamics of the flow fields in RFBs is likely to be very different. In the present paper, we report on a fundamental study of the hydrodynamics of a serpentine flow field relevant to RFB applications. The permeability of the porous medium has been measured under different compression ratios and this is found to be in the range of 5-8 × 10-11 m2. The pressure drop in two serpentine flow fields of different geometric characteristics has been measured over a range of Reynolds numbers. Further analysis using computational fluid dynamics simulations brings out the importance of the compression of the porous medium as an additional parameter in determining the flow distribution and pressure drop in these flow fields. © 2013 Elsevier B.V. All rights reserved.

Ex-situ experimental studies on serpentine flow field design for redox flow battery systems

Serpentine flow-fields have long been used in polymer electrolyte membrane (PEM) fuel cells for effective transportation of reactants from the flow-field to the reaction sites. It has been observed in the literature that localized flooding near the U-bend region of serpentine flow-fields occurs at high current densities. This has been attributed to the boundary layer separation and recirculation of flow in the U-bend. In the present study, it is established, using computational fluid dynamics (CFD) simulations, that this is due to lower channel-to-channel cross-flow in the electrodes between consecutive serpentine channels rather than to the flow-field in the gas distribution channels. © 2008 Elsevier B.V. All rights reserved.

Effect of channel-to-channel cross-flow on local flooding in serpentine flow-fields

Single U- and Z-type parallel-channel configurations for gas distributor plates in planar fuel cells reduce the pressure drop but give rise to the problem of severe flow maldistribution wherein some of the channels may be starved of the reactants. In this paper, previous analytical solutions obtained for single U- and Z-type flow configurations are extended to multiple U- and multiple Z-type flow configurations of interest to fuel cell applications. Algorithms to calculate flow distribution and pressure drop in multiple U- and Z-type flow configurations are developed. The results are validated by comparison with those obtained from three-dimensional computational fluid dynamics (CFD) simulations. It is found that there is a significant improvement in the flow distribution in some configurations without paying for extra pressure drop. The possibility of unmatched distribution on the cathode and the anodes sides is also highlighted. Careful design of the flow configuration is therefore necessary for optimum performance. © 2005 Elsevier B.V. All rights reserved.

Pressure drop and flow distribution in multiple parallel-channel configurations used in proton-exchange membrane fuel cell stacks

The interdigitated flow configuration is unique in the sense that the reactants are forced through the porous electrodes in this configuration, whereas this occurs by diffusion in the conventional types of flow fields. Previous studies have shown that this reduces the possibility of flooding of the cathode electrode resulting in improved efficiency of the fuel cell, however, at the cost of a higher-pressure drop. In the present study, computational fluid dynamics (CFD)-based simulations have been used to study the effect of important geometric parameters such as the channel, the header and the electrode dimensions. The results show that for low permeabilities the flow is uniform across the porous electrode; however, for permeabilities in the range of 10-11 to 10-10 m2, the flow may become non-uniform. Under these conditions, calculations in four-cell and eight-cell parallel interdigitated configuration show that significant flow maldistribution among the parallel channels is likely to occur. © 2005.

Flow maldistribution in interdigitated channels used in PEM fuel cells

Pipelines and ducting systems used in process industry applications are characterized by large sizes, sharp bends and successive bends connected by short straight sections. Systematic studies of such flow situations have not been reported in the literature and the design of such ducting systems is based on rules of thumb and scaled-model testing. Taking advantage of the potential size-insensitivity of CFD-based calculations, a large number of calculations of typical flow situations has been carried out in the present study to address such issues as the optimum location of guides vanes, the influence of an upstream bend on the loss coefficient and the scaling laws for proper extrapolation of laboratory results to industrial scale applications. It is shown that the ideal radial location of a vane for a square duct is given by (RiRo )0.5 and that the influence of an upstream bend on the loss coefficient is beneficial in most cases. Thus, the calculation of bend losses treating each bend as being isolated is likely to be conservative. The velocity profile is uniformly improved by the use of vanes. The loss coefficient is not very sensitive to the fluid scaling, but the effect of wall roughness has to be considered carefully in scaled-down conditions. © 2004 Institution of Chemical Engineers.

Chemical Engineering Research and Design

Pressure losses and flow maldistribution in ducts with sharp bends

Numerical Heat Transfer and Fluid Flow

Heat Conduction

Journal of the American Society for Naval Engineers

LAMINAR FLOW PRESSURE LOSSES IN 90 DEGREE CONSTANT CIRCULAR CROSS-SECTION BENDS

Experimental Thermal and Fluid Science

Liquid flow friction factor and heat transfer coefficient in small channels: an experimental investigation

Visualization of water buildup in the cathode of a transparent PEM fuel cell

Pressure losses in laminar flow through serpentine channels in fuel cell stacks

Journal	Journal of Power Sources
ISSN	03787753
Open Access	No