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Chaoyang Wang - One of the best experts on this subject based on the ideXlab platform.
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Numerical modeling of liquid water motion in a polymer electrolyte fuel cell
2020Co-Authors: Fangming Jiang, Chaoyang WangAbstract:Computational fuel cell dynamics Multiphase Mixture model Water management a b s t r a c t A three dimensional transient model fully coupling the two phase flow, species transport, heat transport, and electrochemical processes is developed to investigate the liquid water formation and transport in a polymer electrolyte fuel cell (PEFC). This model is based on the Multiphase Mixture (M2) formulation with a complete treatment of two phase transport throughout the PEFC, including gas channels, enabling modeling the liquid water motion in the entire PEFC. This work particularly focuses on the liquid water accumulation and transport in gas channels. It is revealed that the liquid water accumulation in gas channels mainly relies on three mechanisms and in the anode and cathode may rely on different mechanisms. The transport of liquid water in the anode channel basically follows a condensationeevaporation mechanism, in sharp contrast to the hydrodynamic transport of liquid water in the cathode channel. Liquid water in the cathode channel can finally flow outside from the exit along with the exhaust gas. As the presence of liquid water in gas channels alters the flow regime involved, from the single phase homogeneous flow to two phase flow, the flow resistance is found to significantly increase
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numerical modeling of liquid water motion in a polymer electrolyte fuel cell
International Journal of Hydrogen Energy, 2014Co-Authors: Fangming Jiang, Chaoyang WangAbstract:Abstract A three dimensional transient model fully coupling the two phase flow, species transport, heat transport, and electrochemical processes is developed to investigate the liquid water formation and transport in a polymer electrolyte fuel cell (PEFC). This model is based on the Multiphase Mixture (M2) formulation with a complete treatment of two phase transport throughout the PEFC, including gas channels, enabling modeling the liquid water motion in the entire PEFC. This work particularly focuses on the liquid water accumulation and transport in gas channels. It is revealed that the liquid water accumulation in gas channels mainly relies on three mechanisms and in the anode and cathode may rely on different mechanisms. The transport of liquid water in the anode channel basically follows a condensation–evaporation mechanism, in sharp contrast to the hydrodynamic transport of liquid water in the cathode channel. Liquid water in the cathode channel can finally flow outside from the exit along with the exhaust gas. As the presence of liquid water in gas channels alters the flow regime involved, from the single phase homogeneous flow to two phase flow, the flow resistance is found to significantly increase.
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comment on a look at the Multiphase Mixture model for pem fuel cell simulations electrochem solid state lett 11 b132 2008
Electrochemical and Solid State Letters, 2009Co-Authors: Chaoyang WangAbstract:The article of Gurau et al. discusses the Multiphase Mixture M2 model developed by Wang and co-workers over the last 15 years for the modeling of Multiphase flow through porous media with liquid-vapor phase change. I would like to offer the following comments. 1. All published works on PEM fuel cell PEMFC simulations, based on either the classical multifluid approach e.g., Ref. 19, 20, and 22 in Ref. 1 and numerous others available in more recent literature or the M2 model, use two-phase Darcy’s law as the momentum equation for individual phase motion, which can be specifically written as
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a combined finite element upwind finite volume method for liquid feed direct methanol fuel cell simulations
International Conference on Fuel Cell Science Engineering and Technology FUELCELL Collocated with ASME International Conference on Energy Sustainabili, 2008Co-Authors: Pengtao Sun, Chaoyang WangAbstract:In this paper, a three-dimensional, two-phase transport model of liquid-feed direct methanol fuel cell (DMFC), which is based on the Multiphase Mixture formulation and encompasses all components in a DMFC using a single computational domain, is specifically studied and simulated by a combined finite element-upwind finite volume discretization along with Newton’s method, where flow, species, charge-transport and energy equations are simultaneously addressed. Numerical simulations in 3D are carried out to explore and design efficient and robust numerical algorithms for the sake of fast and convergent nonlinear iteration. A more reasonable source term of water transport equation, and a series of efficient numerical algorithms and discretizations are specifically designed and analyzed to assist in achieving this goal. Our numerical simulations demonstrate that the convergent and correct physical solutions can be attained within 100 more steps, against the oscillating and long-running nonlinear iterations (up to 5000 steps) operated by standard finite element/volume method without new numerical techniques.Copyright © 2008 by ASME
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prediction of dry wet dry transition in polymer electrolyte fuel cells
Journal of The Electrochemical Society, 2007Co-Authors: Hyunchul Ju, Chaoyang WangAbstract:Condensation and evaporation fronts co-exist in present-day automotive polymer electrolyte fuel cells (PEFCs) where low-humidity reactant gases are fed in counterflow. Capturing of such a transition between a single- and a two-phase regime is not only of technological significance, but also represents a great numerical challenge in PEFC modeling. In this work we demonstrate a computational capability to predict the dry-wet-dry transition in a PEFC based on the Multiphase Mixture (M 2 ) framework. The M 2 model is a three-dimensional, two-phase, and multicomponent full-cell model featuring a detailed membrane-electrode assembly (MEA) sub-model. Three-dimensional results on the dry-wet-dry transition under low-humidity operation and in counterflow are presented. The dry-to-wet transition described in this work provides a benchmark problem to develop and test future generation PEFC models.
Ping Cheng - One of the best experts on this subject based on the ideXlab platform.
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Multiphase flow and heat transfer in porous media
Advances in heat transfer, 1997Co-Authors: Chaoyang Wang, Ping ChengAbstract:Publisher Summary This chapter outlines several theoretical models currently prevailing for Multiphase flow and heat transfer in porous media. In particular, a Multiphase Mixture model is elaborated and compared with the traditional Multiphase flow model and unsaturated flow theory. This model is rigorously derived from the traditional Multiphase flow model (MFM) without making further approximations. The new model views the multiple phases as constituents of a Mixture, and thus consists only of the conservation equations for the whole Multiphase Mixture. All primary variables in this model are Mixture properties; therefore, complex tasks to track phase interfaces separating various subregions and handle phase appearance or disappearance are avoided. The chapter discusses fundamental systems rather than specific applications. To establish a fundamental theoretical framework, basic concepts associated with Multiphase transport in porous media are discussed. The chapter reviews both theoretical and experimental work for single component two-phase systems with major applications to thermal engineering, while general Multiphase, multicomponent systems in connection with a wide variety of engineering applications, such as drying of porous materials, groundwater contamination, and remediation. The chapter concludes that the studies of heat transfer in multicomponent porous media systems are only at the initial stage, and very extensive research is needed in this technologically important and fundamentally intricate subfield of heat transfer.
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a Multiphase Mixture model for Multiphase multicomponent transport in capillary porous media i model development
International Journal of Heat and Mass Transfer, 1996Co-Authors: Chaoyang Wang, Ping ChengAbstract:Abstract A new model for Multiphase, multicomponent transport in capillary porous media is developed, in which the multiple phases are considered as constituents of a Multiphase Mixture. This Multiphase Mixture model consists only of the conservation equations for the Multiphase Mixture and is derived from the classic Multiphase flow formulation without making any approximations. In addition, algebraic relations are found which can be used to back out the individual phase flow fields from the Mixture velocity in a post-processing fashion. While being mathematically exactly equivalent to the traditional Multiphase flow model, the present formulation significantly reduces the number of model equations, thus offering an efficient alternative for the theoretical analysis and numerical simulation of Multiphase transport phenomena in porous media. A detailed application to two-phase, binary systems shows that the complex transport problems become more tractable within the framework of this new formulation.
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a Multiphase Mixture model for Multiphase multicomponent transport in capillary porous media ii numerical simulation of the transport of organic compounds in the subsurface
International Journal of Heat and Mass Transfer, 1996Co-Authors: Ping Cheng, Chaoyang WangAbstract:Abstract A newly developed Multiphase Mixture model is applied to numerically investigate infiltration and transport of nonaqueous phase liquids (NAPLs) in the unsaturated subsurface. Simultaneous flows of liquid and gas phases, solutal convection and the associated organic vapor transport in the gas phase are accounted for in the numerical model. It is shown that the numerical modeling of complex and interactive transport processes in Multiphase, multicomponent systems can become computationally less intensive if based on this new model. The numerical results for three common contaminants reveal that the two-phase zone resulting from a NAPL spill is generally characterized by two distinct regions: an elongated pancake-shaped lens of high NAPL saturation which floats over the water table, and the area above it at lower saturation which was previously swept by the NAPL infiltration front. These predicted features are consistent with previous experimental observations for lighter than water NAPLs. It is also found that the vapor phase transport responsible for large-scale contamination is mainly caused by the displacement flow occurring during NAPL infiltration. In comparison, the density-driven flow due to evaporation of heavier organic chemicals is less important for systems with mobile NAPLs. Finally, several areas where future research is needed are discussed.
Mohamed Ouda - One of the best experts on this subject based on the ideXlab platform.
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development of a new Multiphase sediment transport model for free surface flows
International Journal of Multiphase Flow, 2019Co-Authors: Mohamed Ouda, Erik ToormanAbstract:Abstract Modeling of sediment transport in estuaries and coastal areas requires a lot of compromises to keep the computational costs within acceptable limits. Due to that, existing sediment transport models do not account for particle-scale physics, e.g. particle-particle interaction and turbulence modulation by sediment, which play a significant role, especially in the non-dilute regime. In the current study, a newly developed physics-based sediment transport model for free surface flows and its numerical implementation within the OpenFOAM framework is introduced. The new model is based on the Multiphase Mixture theory to account for interactions between sediment and water while tracking the free surface at the same time. A modified VOF equation for sediment-laden free surface flow was derived and implemented. The interphase momentum transfer is considered by solving an additional closure for the slip velocity which includes the effects of drag force, turbulent dispersion, and shear-induced diffusion. Dense granular flow rheology is used to supply the required closures for particle stresses. Additionally, suitable closures for the Mixture and turbulent viscosities are introduced. The model was validated using experimental data and analytical solutions of five test cases of variable complexity. This includes pure sedimentation, laminar bedload transport, turbulent sheet flow, local scour due to a submerged jet, and wave-induced scour under a submarine pipeline.
Fangming Jiang - One of the best experts on this subject based on the ideXlab platform.
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Numerical modeling of liquid water motion in a polymer electrolyte fuel cell
2020Co-Authors: Fangming Jiang, Chaoyang WangAbstract:Computational fuel cell dynamics Multiphase Mixture model Water management a b s t r a c t A three dimensional transient model fully coupling the two phase flow, species transport, heat transport, and electrochemical processes is developed to investigate the liquid water formation and transport in a polymer electrolyte fuel cell (PEFC). This model is based on the Multiphase Mixture (M2) formulation with a complete treatment of two phase transport throughout the PEFC, including gas channels, enabling modeling the liquid water motion in the entire PEFC. This work particularly focuses on the liquid water accumulation and transport in gas channels. It is revealed that the liquid water accumulation in gas channels mainly relies on three mechanisms and in the anode and cathode may rely on different mechanisms. The transport of liquid water in the anode channel basically follows a condensationeevaporation mechanism, in sharp contrast to the hydrodynamic transport of liquid water in the cathode channel. Liquid water in the cathode channel can finally flow outside from the exit along with the exhaust gas. As the presence of liquid water in gas channels alters the flow regime involved, from the single phase homogeneous flow to two phase flow, the flow resistance is found to significantly increase
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numerical modeling of liquid water motion in a polymer electrolyte fuel cell
International Journal of Hydrogen Energy, 2014Co-Authors: Fangming Jiang, Chaoyang WangAbstract:Abstract A three dimensional transient model fully coupling the two phase flow, species transport, heat transport, and electrochemical processes is developed to investigate the liquid water formation and transport in a polymer electrolyte fuel cell (PEFC). This model is based on the Multiphase Mixture (M2) formulation with a complete treatment of two phase transport throughout the PEFC, including gas channels, enabling modeling the liquid water motion in the entire PEFC. This work particularly focuses on the liquid water accumulation and transport in gas channels. It is revealed that the liquid water accumulation in gas channels mainly relies on three mechanisms and in the anode and cathode may rely on different mechanisms. The transport of liquid water in the anode channel basically follows a condensation–evaporation mechanism, in sharp contrast to the hydrodynamic transport of liquid water in the cathode channel. Liquid water in the cathode channel can finally flow outside from the exit along with the exhaust gas. As the presence of liquid water in gas channels alters the flow regime involved, from the single phase homogeneous flow to two phase flow, the flow resistance is found to significantly increase.
Erik Toorman - One of the best experts on this subject based on the ideXlab platform.
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development of a new Multiphase sediment transport model for free surface flows
International Journal of Multiphase Flow, 2019Co-Authors: Mohamed Ouda, Erik ToormanAbstract:Abstract Modeling of sediment transport in estuaries and coastal areas requires a lot of compromises to keep the computational costs within acceptable limits. Due to that, existing sediment transport models do not account for particle-scale physics, e.g. particle-particle interaction and turbulence modulation by sediment, which play a significant role, especially in the non-dilute regime. In the current study, a newly developed physics-based sediment transport model for free surface flows and its numerical implementation within the OpenFOAM framework is introduced. The new model is based on the Multiphase Mixture theory to account for interactions between sediment and water while tracking the free surface at the same time. A modified VOF equation for sediment-laden free surface flow was derived and implemented. The interphase momentum transfer is considered by solving an additional closure for the slip velocity which includes the effects of drag force, turbulent dispersion, and shear-induced diffusion. Dense granular flow rheology is used to supply the required closures for particle stresses. Additionally, suitable closures for the Mixture and turbulent viscosities are introduced. The model was validated using experimental data and analytical solutions of five test cases of variable complexity. This includes pure sedimentation, laminar bedload transport, turbulent sheet flow, local scour due to a submerged jet, and wave-induced scour under a submarine pipeline.