The Experts below are selected from a list of 216765 Experts worldwide ranked by ideXlab platform

Xianguo Li - One of the best experts on this subject based on the ideXlab platform.

  • numerical investigation of water dynamics in a novel proton exchange membrane fuel cell Flow Channel
    Journal of Power Sources, 2013
    Co-Authors: Qing Du, Kui Jiao, Yan Yin, Xianguo Li, Yanzhou Qin
    Abstract:

    Abstract Water dynamics in the Flow Channel of a proton exchange membrane fuel cell is significantly important to water management and removal. In this study, volume-of-fluid method is used to investigate numerically the three-dimensional water dynamics in a Flow Channel with a hydrophilic needle. It is found that water transport and dynamics in this novel Flow Channel are quite different from the conventional Channel. Liquid water droplet, introduced on the electrode surface, is removed through capillary effect once touching the hydrophilic needle. This is desirable since the electrode surface becomes free of liquid water, avoiding the flooding and blockage of reactant gas transport into the electrode. Increasing the contact area between the water droplet and needle, through an increase in the diameter or length of the needle, can facilitate water removal from the electrode surface because of greater capillary effect, but it also increases the pressure drop in the Channel due to greater blockage by the needle. Overall, the pressure drop in the modified Channel is still small compared to the pressure drop in a serpentine Flow Channel, making the present approach viable for use in the conventional parallel Flow Channels for proton exchange membrane fuel cells.

  • an experimental and numerical investigation on the cross Flow through gas diffusion layer in a pem fuel cell with a serpentine Flow Channel
    Journal of Power Sources, 2007
    Co-Authors: Jae Wan Park, Xianguo Li
    Abstract:

    A serpentine Flow Channel is one of the most common and practical Channel layouts for a polymer electrolyte membrane (PEM) fuel cell since it ensures the removal of water produced in a cell with acceptable parasitic load. During the reactant Flows along the Flow Channel, it can also leak or cross to neighboring Channel via the porous gas diffusion layer due to the high pressure gradient caused by the short distance. Such a cross Flow leads to a larger effective Flow area altering reactant Flow in the Flow Channel so that the resultant pressure and Flow distributions are substantially different from that without considering cross Flow, even though this cross Flow has largely been ignored in previous studies. In this work, a numerical and experimental study has been carried out to investigate the cross Flow in a PEM fuel cell. Experimental measurements revealed that the pressure drop in a PEM fuel cell is significantly lower than that without cross Flow. Three-dimensional numerical simulation has been performed for wide ranges of Flow rate, permeability and thickness of gas diffusion layer to analyze the effects of those parameters on the resultant cross Flow and the pressure drop of the reactant streams. Considerable amount of cross Flow through gas diffusion layer has been found in Flow simulation and its effect on pressure drop becomes more significant as the permeability and the thickness of gas diffusion layer are increased. The effects of this phenomenon are also crucial for effective water removal from the porous electrode structure and for estimating pumping energy requirement in a PEM fuel cell, it cannot be neglected for the analysis, simulation, design, operation and performance optimization of practical PEM fuel cells.

Yanzhou Qin - One of the best experts on this subject based on the ideXlab platform.

  • effective removal and transport of water in a pem fuel cell Flow Channel having a hydrophilic plate
    Applied Energy, 2014
    Co-Authors: Kui Jiao, Yanzhou Qin, Yan Yin
    Abstract:

    Effective removal and transport of water in the Flow Channel of a proton exchange membrane (PEM) fuel cell (PEMFC) is significantly important to the critical water management in PEMFCs. In this study, the process of water removal and transport is investigated numerically by using the volume-of-fluid method for a Flow Channel having a hydrophilic plate in the middle of the Channel. The results show that the liquid water droplet on the membrane-electrode assembly (MEA) surface can be removed effectively, and the removal process is facilitated significantly by the hydrophilic plate which should have a surface contact angle larger than the bottom Channel surface but less than the MEA surface. Once the liquid water contacts the plate, it is detached from the MEA surface, and transported to the Channel surface along the plate surface; whereas without the plate the water droplet is transported along the MEA surface under the same Flow condition. The pressure drop associated with the Flow in the Channel can be reduced substantially by the presence of the plate due to a characteristic change in the water removal and transport process, when compared to the pressure drop in a conventional Flow Channel or a Channel with a needle shown in literature. The wettability, the length and the height of the plate all can have an impact on the water transport and dynamics as well as the associated pressure drop in the Flow Channel. A parametric study is carried out to determine the optimal values for the surface contact angle, the length and height of the plate.

  • effect of wettability on water removal from the gas diffusion layer surface in a novel proton exchange membrane fuel cell Flow Channel
    International Journal of Hydrogen Energy, 2013
    Co-Authors: Yanzhou Qin, Yan Yin, Kui Jiao
    Abstract:

    Effective water removal from the proton exchange membrane fuel cell (PEMFC) surface exposed to the Flow Channel is critical to the operation and water management in PEMFCs. In this study, the water removal process is investigated numerically for a novel Flow Channel formed by inserting a hydrophilic needle in the conventional PEMFC Flow Channel, and the effect of the surface wettability of the membrane electrode assembly (MEA) and the inserted needle on the water removal process is studied. The results show that the liquid water can be more effectively removed from the MEA surface for larger MEA surface contact angles and smaller needle surface contact angles. The pressure drop for the Flow in the Channel is also examined and it is seen to be indicative of the liquid water Flow and transport in the Flow Channel, suggesting that pressure drop is a useful parameter for the investigation of water transport and dynamics in the Flow Channel.

  • numerical investigation of water dynamics in a novel proton exchange membrane fuel cell Flow Channel
    Journal of Power Sources, 2013
    Co-Authors: Qing Du, Kui Jiao, Yan Yin, Xianguo Li, Yanzhou Qin
    Abstract:

    Abstract Water dynamics in the Flow Channel of a proton exchange membrane fuel cell is significantly important to water management and removal. In this study, volume-of-fluid method is used to investigate numerically the three-dimensional water dynamics in a Flow Channel with a hydrophilic needle. It is found that water transport and dynamics in this novel Flow Channel are quite different from the conventional Channel. Liquid water droplet, introduced on the electrode surface, is removed through capillary effect once touching the hydrophilic needle. This is desirable since the electrode surface becomes free of liquid water, avoiding the flooding and blockage of reactant gas transport into the electrode. Increasing the contact area between the water droplet and needle, through an increase in the diameter or length of the needle, can facilitate water removal from the electrode surface because of greater capillary effect, but it also increases the pressure drop in the Channel due to greater blockage by the needle. Overall, the pressure drop in the modified Channel is still small compared to the pressure drop in a serpentine Flow Channel, making the present approach viable for use in the conventional parallel Flow Channels for proton exchange membrane fuel cells.

Kui Jiao - One of the best experts on this subject based on the ideXlab platform.

  • multi component multi phase lattice boltzmann modeling of droplet coalescence in Flow Channel of fuel cell
    Journal of Power Sources, 2018
    Co-Authors: Yuze Hou, Hao Deng, Kui Jiao
    Abstract:

    Abstract A multi-component multi-phase lattice Boltzmann model is presented to study the dynamic behavior of droplet coalescence in the Flow Channel of proton exchange membrane fuel cell. The original pseudopotential multiphase model is developed to realize high density and kinematic viscosity ratios, low spurious velocity, good thermodynamic consistency and independent adjustment of surface tension. Multi-component Laplace law and capillary wave tests are conducted to validate the capability of model in capturing static and dynamic characteristics. A new method for multiphase open boundary is proposed, enabling the droplet to pass the outlet naturally. The droplet coalescence is studied elaborately with the consideration of different droplet size arrangement, distance between two droplets, wall contact angle and gas Flow velocity. The droplet shapes are shown with detailed description during the coalescence processes, and the evolutions of droplet height and position throughout the whole processes are measured. Results show that droplet coalescence is beneficial for droplet motion, because the shear force exerted on the droplet, which is determined by the droplet height and gas Flow velocity, is strengthened during the coalescence.

  • direct numerical simulation of low reynolds number turbulent air water transport in fuel cell Flow Channel
    Chinese Science Bulletin, 2017
    Co-Authors: Zhiqiang Niu, Qing Du, Kui Jiao, Renfang Wang, Yan Yin
    Abstract:

    With performance improvement of low-temperature fuel cell (FC), high reactant supply and water generation rates may induce air-water turbulence in the FC Flow Channel. In this research, an air-water turbulent direct numerical simulation (DNS) model is developed to simulate different droplet sizes, locations and interactions in the air-water transport processes comprehensively. It is found that a larger droplet breaks up more easily in turbulence, and a smaller droplet tends to keep lumped. The droplet at corner does not break up because it is away from Channel center. The droplet interaction simulations show that the small droplets merge to form slugs, but still keep lumped in turbulence. It is suggested that two conditions need to be satisfied for droplet break up in FC Flow Channel, one is turbulent Flow, and another is that the droplet needs to be large enough and occupy the center region of Flow Channel to suffer sufficient turbulence fluctuations. The DNS results illustrate some unique phenomena in turbulent Flow, and show that the turbulence has significant effect on the air-water Flow behavior in FC Flow Channel.

  • direct numerical simulation of two phase turbulent Flow in fuel cell Flow Channel
    International Journal of Hydrogen Energy, 2016
    Co-Authors: Zhiqiang Niu, Qing Du, Kui Jiao, Fan Zhang, Yan Yin
    Abstract:

    Abstract For high-performance low-temperature fuel cells (e.g. hydrogen proton exchange membrane fuel cell for powering vehicles), significant amount of reactant needs to be supplied, leading to turbulent two-phase Flow, which is largely ignored in previous studies. In this study, a direct numerical simulation (DNS) model of the two-phase turbulent Flow in fuel cell Flow Channel is developed with a modified volume-of-fluid (VOF) approach for tracking the air/water interface. The turbulent Flow inlet of the two-phase DNS model is obtained from a validated single-phase DNS model. By resolving the whole range of spatial and temporal scales of turbulence, the results of the two-phase DNS model show that the deformation of water droplet is asymmetric and broken into small pieces/films, and is significantly different from the laminar and the corresponding k − e models. It is suggested that the turbulence effect on the two-phase transport in fuel cell Flow Channel is significant and needs to be considered for water management by using the DNS model.

  • effective removal and transport of water in a pem fuel cell Flow Channel having a hydrophilic plate
    Applied Energy, 2014
    Co-Authors: Kui Jiao, Yanzhou Qin, Yan Yin
    Abstract:

    Effective removal and transport of water in the Flow Channel of a proton exchange membrane (PEM) fuel cell (PEMFC) is significantly important to the critical water management in PEMFCs. In this study, the process of water removal and transport is investigated numerically by using the volume-of-fluid method for a Flow Channel having a hydrophilic plate in the middle of the Channel. The results show that the liquid water droplet on the membrane-electrode assembly (MEA) surface can be removed effectively, and the removal process is facilitated significantly by the hydrophilic plate which should have a surface contact angle larger than the bottom Channel surface but less than the MEA surface. Once the liquid water contacts the plate, it is detached from the MEA surface, and transported to the Channel surface along the plate surface; whereas without the plate the water droplet is transported along the MEA surface under the same Flow condition. The pressure drop associated with the Flow in the Channel can be reduced substantially by the presence of the plate due to a characteristic change in the water removal and transport process, when compared to the pressure drop in a conventional Flow Channel or a Channel with a needle shown in literature. The wettability, the length and the height of the plate all can have an impact on the water transport and dynamics as well as the associated pressure drop in the Flow Channel. A parametric study is carried out to determine the optimal values for the surface contact angle, the length and height of the plate.

  • effect of wettability on water removal from the gas diffusion layer surface in a novel proton exchange membrane fuel cell Flow Channel
    International Journal of Hydrogen Energy, 2013
    Co-Authors: Yanzhou Qin, Yan Yin, Kui Jiao
    Abstract:

    Effective water removal from the proton exchange membrane fuel cell (PEMFC) surface exposed to the Flow Channel is critical to the operation and water management in PEMFCs. In this study, the water removal process is investigated numerically for a novel Flow Channel formed by inserting a hydrophilic needle in the conventional PEMFC Flow Channel, and the effect of the surface wettability of the membrane electrode assembly (MEA) and the inserted needle on the water removal process is studied. The results show that the liquid water can be more effectively removed from the MEA surface for larger MEA surface contact angles and smaller needle surface contact angles. The pressure drop for the Flow in the Channel is also examined and it is seen to be indicative of the liquid water Flow and transport in the Flow Channel, suggesting that pressure drop is a useful parameter for the investigation of water transport and dynamics in the Flow Channel.

Yan Yin - One of the best experts on this subject based on the ideXlab platform.

  • direct numerical simulation of low reynolds number turbulent air water transport in fuel cell Flow Channel
    Chinese Science Bulletin, 2017
    Co-Authors: Zhiqiang Niu, Qing Du, Kui Jiao, Renfang Wang, Yan Yin
    Abstract:

    With performance improvement of low-temperature fuel cell (FC), high reactant supply and water generation rates may induce air-water turbulence in the FC Flow Channel. In this research, an air-water turbulent direct numerical simulation (DNS) model is developed to simulate different droplet sizes, locations and interactions in the air-water transport processes comprehensively. It is found that a larger droplet breaks up more easily in turbulence, and a smaller droplet tends to keep lumped. The droplet at corner does not break up because it is away from Channel center. The droplet interaction simulations show that the small droplets merge to form slugs, but still keep lumped in turbulence. It is suggested that two conditions need to be satisfied for droplet break up in FC Flow Channel, one is turbulent Flow, and another is that the droplet needs to be large enough and occupy the center region of Flow Channel to suffer sufficient turbulence fluctuations. The DNS results illustrate some unique phenomena in turbulent Flow, and show that the turbulence has significant effect on the air-water Flow behavior in FC Flow Channel.

  • direct numerical simulation of two phase turbulent Flow in fuel cell Flow Channel
    International Journal of Hydrogen Energy, 2016
    Co-Authors: Zhiqiang Niu, Qing Du, Kui Jiao, Fan Zhang, Yan Yin
    Abstract:

    Abstract For high-performance low-temperature fuel cells (e.g. hydrogen proton exchange membrane fuel cell for powering vehicles), significant amount of reactant needs to be supplied, leading to turbulent two-phase Flow, which is largely ignored in previous studies. In this study, a direct numerical simulation (DNS) model of the two-phase turbulent Flow in fuel cell Flow Channel is developed with a modified volume-of-fluid (VOF) approach for tracking the air/water interface. The turbulent Flow inlet of the two-phase DNS model is obtained from a validated single-phase DNS model. By resolving the whole range of spatial and temporal scales of turbulence, the results of the two-phase DNS model show that the deformation of water droplet is asymmetric and broken into small pieces/films, and is significantly different from the laminar and the corresponding k − e models. It is suggested that the turbulence effect on the two-phase transport in fuel cell Flow Channel is significant and needs to be considered for water management by using the DNS model.

  • effective removal and transport of water in a pem fuel cell Flow Channel having a hydrophilic plate
    Applied Energy, 2014
    Co-Authors: Kui Jiao, Yanzhou Qin, Yan Yin
    Abstract:

    Effective removal and transport of water in the Flow Channel of a proton exchange membrane (PEM) fuel cell (PEMFC) is significantly important to the critical water management in PEMFCs. In this study, the process of water removal and transport is investigated numerically by using the volume-of-fluid method for a Flow Channel having a hydrophilic plate in the middle of the Channel. The results show that the liquid water droplet on the membrane-electrode assembly (MEA) surface can be removed effectively, and the removal process is facilitated significantly by the hydrophilic plate which should have a surface contact angle larger than the bottom Channel surface but less than the MEA surface. Once the liquid water contacts the plate, it is detached from the MEA surface, and transported to the Channel surface along the plate surface; whereas without the plate the water droplet is transported along the MEA surface under the same Flow condition. The pressure drop associated with the Flow in the Channel can be reduced substantially by the presence of the plate due to a characteristic change in the water removal and transport process, when compared to the pressure drop in a conventional Flow Channel or a Channel with a needle shown in literature. The wettability, the length and the height of the plate all can have an impact on the water transport and dynamics as well as the associated pressure drop in the Flow Channel. A parametric study is carried out to determine the optimal values for the surface contact angle, the length and height of the plate.

  • effect of wettability on water removal from the gas diffusion layer surface in a novel proton exchange membrane fuel cell Flow Channel
    International Journal of Hydrogen Energy, 2013
    Co-Authors: Yanzhou Qin, Yan Yin, Kui Jiao
    Abstract:

    Effective water removal from the proton exchange membrane fuel cell (PEMFC) surface exposed to the Flow Channel is critical to the operation and water management in PEMFCs. In this study, the water removal process is investigated numerically for a novel Flow Channel formed by inserting a hydrophilic needle in the conventional PEMFC Flow Channel, and the effect of the surface wettability of the membrane electrode assembly (MEA) and the inserted needle on the water removal process is studied. The results show that the liquid water can be more effectively removed from the MEA surface for larger MEA surface contact angles and smaller needle surface contact angles. The pressure drop for the Flow in the Channel is also examined and it is seen to be indicative of the liquid water Flow and transport in the Flow Channel, suggesting that pressure drop is a useful parameter for the investigation of water transport and dynamics in the Flow Channel.

  • numerical investigation of water dynamics in a novel proton exchange membrane fuel cell Flow Channel
    Journal of Power Sources, 2013
    Co-Authors: Qing Du, Kui Jiao, Yan Yin, Xianguo Li, Yanzhou Qin
    Abstract:

    Abstract Water dynamics in the Flow Channel of a proton exchange membrane fuel cell is significantly important to water management and removal. In this study, volume-of-fluid method is used to investigate numerically the three-dimensional water dynamics in a Flow Channel with a hydrophilic needle. It is found that water transport and dynamics in this novel Flow Channel are quite different from the conventional Channel. Liquid water droplet, introduced on the electrode surface, is removed through capillary effect once touching the hydrophilic needle. This is desirable since the electrode surface becomes free of liquid water, avoiding the flooding and blockage of reactant gas transport into the electrode. Increasing the contact area between the water droplet and needle, through an increase in the diameter or length of the needle, can facilitate water removal from the electrode surface because of greater capillary effect, but it also increases the pressure drop in the Channel due to greater blockage by the needle. Overall, the pressure drop in the modified Channel is still small compared to the pressure drop in a serpentine Flow Channel, making the present approach viable for use in the conventional parallel Flow Channels for proton exchange membrane fuel cells.

Cha'o-kuang Chen - One of the best experts on this subject based on the ideXlab platform.

  • improvement of performance of gas Flow Channel in pem fuel cells
    Energy Conversion and Management, 2008
    Co-Authors: Jenn-kun Kuo, Tzushuang Yen, Cha'o-kuang Chen
    Abstract:

    This study performs numerical simulations to evaluate the convective heat transfer performance and velocity Flow characteristics of the gas Flow Channel design to enhance the performance of proton exchange membrane fuel cells (PEMFCs). To restrict the current simulations to two-dimensional incompressible Flows, the Flow regime is assumed to be laminar with a low Reynolds number of approximately 200. In addition, the field synergy principle is applied to demonstrate that an increased interruption within the fluid Flow reduces the intersection angle between the velocity vector and the temperature gradient. The interruption within the fluid Flow is induced by different type of obstacles: wave like, trapezoid like and ladder like forms and the straight form of the gas Flow Channel. The numerical results show that, compared to a conventional straight gas Flow Channel, the wave like, trapezoid like and ladder like geometry of the proposed gas Flow Channel increases the mean Nusselt number by a factor of approximately two. Furthermore, the periodic three patterns (wave like, trapezoid like and ladder like) structure increases the gas Flow velocity in the Channel and, hence, improves the catalysis reaction performance in the catalyst layer. Finally, the results show that the three patterns geometry of the gas Flow Channel reduces the included angle between the velocity vector and the temperature gradient. Hence, the present numerical results are consistent with the field synergy principle, which states that the convective heat transfer is enhanced when the velocity vector and temperature gradient are closely aligned with one another.

  • the effects of buoyancy on the performance of a pem fuel cell with a wave like gas Flow Channel design by numerical investigation
    International Journal of Heat and Mass Transfer, 2007
    Co-Authors: Jenn-kun Kuo, Cha'o-kuang Chen
    Abstract:

    This study performs numerical simulations to investigate the effects of buoyancy on the gas Flow characteristics, temperature distribution, electrochemical reaction efficiency and electrical performance of a proton exchange membrane fuel cell (PEMFC) with a novel wave-like gas Flow Channel design. In general, the simulation results show that compared to the straight geometry of a conventional gas Flow Channel, the wave-like configuration enhances the transport through the porous layer and improves the temperature distribution within the Channel. As a result, the PEMFC has an improved fuel utilization efficiency and an enhanced heat transfer performance. It is found that the buoyancy effect increases the velocity of the reactant fuel gases in both the vertical and the horizontal directions. This increases the rate at which the oxygen gas is consumed in the fuel cell but improves the electrical performance of the PEMFC. The results show that compared to the conventional straight gas Flow Channel, the wave-like gas Flow Channel increases the output voltage and improves the maximum power density by approximately 39.5%.

  • The effects of buoyancy on the performance of a PEM fuel cell with a wave-like gas Flow Channel design by numerical investigation
    International Journal of Heat and Mass Transfer, 2007
    Co-Authors: Jenn-kun Kuo, Cha'o-kuang Chen
    Abstract:

    This study performs numerical simulations to investigate the effects of buoyancy on the gas Flow characteristics, temperature distribution, electrochemical reaction efficiency and electrical performance of a proton exchange membrane fuel cell (PEMFC) with a novel wave-like gas Flow Channel design. In general, the simulation results show that compared to the straight geometry of a conventional gas Flow Channel, the wave-like configuration enhances the transport through the porous layer and improves the temperature distribution within the Channel. As a result, the PEMFC has an improved fuel utilization efficiency and an enhanced heat transfer performance. It is found that the buoyancy effect increases the velocity of the reactant fuel gases in both the vertical and the horizontal directions. This increases the rate at which the oxygen gas is consumed in the fuel cell but improves the electrical performance of the PEMFC. The results show that compared to the conventional straight gas Flow Channel, the wave-like gas Flow Channel increases the output voltage and improves the maximum power density by approximately 39.5%.

  • evaluating the enhanced performance of a novel wave like form gas Flow Channel in the pemfc using the field synergy principle
    Journal of Power Sources, 2006
    Co-Authors: Jenn-kun Kuo, Cha'o-kuang Chen
    Abstract:

    This study performs numerical simulations to evaluate the convective heat transfer performance and velocity Flow characteristics of a novel gas Flow Channel with a wave-like form designed to enhance the performance of Proton Exchange Membrane Fuel Cells (PEMFCs). To restrict the current simulations to two-dimensional incompressible Flows, the Flow regime is assumed to be laminar with a low Reynolds number of approximately 200. The numerical results show that compared to a conventional straight gas Flow Channel, the wave-like geometry of the proposed gas Flow Channel increases the mean Nusselt number by a factor of approximately two. Furthermore, the periodic wave-like structure increases the gas Flow velocity in the Channel and hence improves the catalysis reaction performance in the catalyst layer. Finally, the results show that the wave-like geometry of the gas Flow Channel reduces the included angle between the velocity vector and the temperature gradient. Hence, the present numerical results are consistent with the field synergy principle, which states that the convective heat transfer is enhanced when the velocity vector and temperature gradient are closely aligned with one another.