The Experts below are selected from a list of 297 Experts worldwide ranked by ideXlab platform
Matthew M. Mench - One of the best experts on this subject based on the ideXlab platform.
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quantification of liquid water accumulation and distribution in a polymer electrolyte fuel Cell using neutron imaging
Journal of Power Sources, 2006Co-Authors: Aylin Turhan, K Heller, Jack S. Brenizer, Matthew M. MenchAbstract:Operating parameters, material properties and flow field geometry have a deterministic role on the water storage and distribution within the flow channels and porous media in a fuel Cell. However, their effects are not yet precisely understood. In this study, extensive neutron imaging experiments were conducted to visualize and quantify the amount of liquid water in the fuel Cell channels and diffusion media as a function of inlet gas flow rate, Cell pressure and inlet relative humidity. A seven-channel parallel flow configuration PEFC was used to isolate these parameters from flow field switchback interaction effects. The neutron imaging experiments were performed at different inlet gas flow rates, Operating Cell pressures and inlet relative humidities. At each Operating condition, the distribution of liquid water in the diffusion media under the lands, and in or under the channels was obtained. Furthermore, at three different Cell pressures (0.2 MPa, 0.15 MPa and 0.1 MPa), liquid water distribution and quantification was obtained. The liquid water mass in the Cell decreased with increasing pressure for over-humidified anode inlet conditions. Comparison of the fuel Cell performance with the total liquid water mass in the Cell indicates a non-monotonic relationship between liquid water content and performance. Furthermore, Cell performance was highly sensitive to incremental changes in the membrane liquid water content.
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quantification of liquid water accumulation and distribution in a polymer electrolyte fuel Cell using neutron imaging
Journal of Power Sources, 2006Co-Authors: Aylin Turhan, K Heller, Jack S. Brenizer, Matthew M. MenchAbstract:Operating parameters, material properties and flow field geometry have a deterministic role on the water storage and distribution within the flow channels and porous media in a fuel Cell. However, their effects are not yet precisely understood. In this study, extensive neutron imaging experiments were conducted to visualize and quantify the amount of liquid water in the fuel Cell channels and diffusion media as a function of inlet gas flow rate, Cell pressure and inlet relative humidity. A seven-channel parallel flow configuration PEFC was used to isolate these parameters from flow field switchback interaction effects. The neutron imaging experiments were performed at different inlet gas flow rates, Operating Cell pressures and inlet relative humidities. At each Operating condition, the distribution of liquid water in the diffusion media under the lands, and in or under the channels was obtained. Furthermore, at three different Cell pressures (0.2 MPa, 0.15 MPa and 0.1 MPa), liquid water distribution and quantification was obtained. The liquid water mass in the Cell decreased with increasing pressure for over-humidified anode inlet conditions. Comparison of the fuel Cell performance with the total liquid water mass in the Cell indicates a non-monotonic relationship between liquid water content and performance. Furthermore, Cell performance was highly sensitive to incremental changes in the membrane liquid water content.
J W Van Zee - One of the best experts on this subject based on the ideXlab platform.
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verifying predictions of water and current distributions in a serpentine flow field polymer electrolyte membrane fuel Cell
Journal of The Electrochemical Society, 2003Co-Authors: W K Lee, Sirivatch Shimpalee, J W Van ZeeAbstract:A three-dimensional numerical model is used to predict the local current density and membrane conductivity inside a 10 cm 2 polymer electrolyte membrane fuel Cell with a serpentine flow path. The model includes the gas diffusion layer, and it accounts for the area hidden from direct contact with the flowing gases by the current collector contacts (i.e., the ribs). The predictions agree with experimental data for various Operating Cell temperatures at a fixed inlet humidity condition. Data on closure of the water balances are presented and are also shown to be consistent with the numerical predictions of water transport by electro-osmotic drag and back diffusion. The data and the model show conditions where insufficient water lowers the conductivity of the membrane and yields low currents at a fixed voltage. Finally, predictions of the distributions of current density, water flux per proton, and membrane conductivity are presented.
Shawn M. Clapham - One of the best experts on this subject based on the ideXlab platform.
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In-situ membrane hydration measurement of proton exchange membrane fuel Cells
Journal of Power Sources, 2015Co-Authors: Yeh-hung Lai, Gerald W Fly, Shawn M. ClaphamAbstract:Abstract Achieving proper membrane hydration control is one of the most critical aspects of PEM fuel Cell development. This article describes the development and application of a novel 50 cm 2 fuel Cell device to study the in-situ membrane hydration by measuring the through-thickness membrane swelling via an array of linear variable differential transducers. Using this setup either as an air/air (dummy) Cell or as a hydrogen/air (Operating) Cell, we performed a series of hydration and dehydration experiments by cycling the RH of the inlet gas streams at 80 °C. From the linear relationship between the under-the-land swelling and the over-the-channel water content, the mechanical constraint within the fuel Cell assembly can suppress the membrane water uptake by 11%–18%. The results from the air/air humidity cycling test show that the membrane can equilibrate within 120 s for all RH conditions and that membrane can reach full hydration at a RH higher than 140% in spite of the use of a liquid water impermeable Carbel MP30Z microporous layer. This result confirms that the U.S. DOE's humidity cycling mechanical durability protocol induces sufficient humidity swings to maximize hygrothermal mechanical stresses. This study shows that the novel experimental technique can provide a robust and accurate means to study the in-situ hydration of thin membranes subject to a wide range of fuel Cell conditions.
Aylin Turhan - One of the best experts on this subject based on the ideXlab platform.
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quantification of liquid water accumulation and distribution in a polymer electrolyte fuel Cell using neutron imaging
Journal of Power Sources, 2006Co-Authors: Aylin Turhan, K Heller, Jack S. Brenizer, Matthew M. MenchAbstract:Operating parameters, material properties and flow field geometry have a deterministic role on the water storage and distribution within the flow channels and porous media in a fuel Cell. However, their effects are not yet precisely understood. In this study, extensive neutron imaging experiments were conducted to visualize and quantify the amount of liquid water in the fuel Cell channels and diffusion media as a function of inlet gas flow rate, Cell pressure and inlet relative humidity. A seven-channel parallel flow configuration PEFC was used to isolate these parameters from flow field switchback interaction effects. The neutron imaging experiments were performed at different inlet gas flow rates, Operating Cell pressures and inlet relative humidities. At each Operating condition, the distribution of liquid water in the diffusion media under the lands, and in or under the channels was obtained. Furthermore, at three different Cell pressures (0.2 MPa, 0.15 MPa and 0.1 MPa), liquid water distribution and quantification was obtained. The liquid water mass in the Cell decreased with increasing pressure for over-humidified anode inlet conditions. Comparison of the fuel Cell performance with the total liquid water mass in the Cell indicates a non-monotonic relationship between liquid water content and performance. Furthermore, Cell performance was highly sensitive to incremental changes in the membrane liquid water content.
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quantification of liquid water accumulation and distribution in a polymer electrolyte fuel Cell using neutron imaging
Journal of Power Sources, 2006Co-Authors: Aylin Turhan, K Heller, Jack S. Brenizer, Matthew M. MenchAbstract:Operating parameters, material properties and flow field geometry have a deterministic role on the water storage and distribution within the flow channels and porous media in a fuel Cell. However, their effects are not yet precisely understood. In this study, extensive neutron imaging experiments were conducted to visualize and quantify the amount of liquid water in the fuel Cell channels and diffusion media as a function of inlet gas flow rate, Cell pressure and inlet relative humidity. A seven-channel parallel flow configuration PEFC was used to isolate these parameters from flow field switchback interaction effects. The neutron imaging experiments were performed at different inlet gas flow rates, Operating Cell pressures and inlet relative humidities. At each Operating condition, the distribution of liquid water in the diffusion media under the lands, and in or under the channels was obtained. Furthermore, at three different Cell pressures (0.2 MPa, 0.15 MPa and 0.1 MPa), liquid water distribution and quantification was obtained. The liquid water mass in the Cell decreased with increasing pressure for over-humidified anode inlet conditions. Comparison of the fuel Cell performance with the total liquid water mass in the Cell indicates a non-monotonic relationship between liquid water content and performance. Furthermore, Cell performance was highly sensitive to incremental changes in the membrane liquid water content.
John Livingstone - One of the best experts on this subject based on the ideXlab platform.
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seasonal variations in amorphous silicon solar module outputs and thin film characteristics
Solar Energy Materials and Solar Cells, 1995Co-Authors: Ricardo Ruther, John LivingstoneAbstract:Abstract Hydrogenated amorphous silicon (a-Si:H) solar modules exposed to outdoor conditions exhibit, over a long-time scale, an efficiency pattern which improves during summer months and decreases in winter time. The variations are usually attributed to two main mechanisms: (a) thermal annealing effects enhanced by summer month temperatures, which might partly offset the efficiency decrease caused by light-induced changes in the amorphous silicon material (known as the Staebler-Wronski effect), and (b) seasonal spectral variations in the solar radiation reaching the earth's surface, which are quite marked in the wavelength region in which amorphous silicon solar Cells respond. While both factors might contribute to a more severe performance degradation in winter, we show, by exposing both commercial a-Si : H solar modules and thin films to the same AM 1.0 spectrum while keeping them at temperatures corresponding to extreme summer and winter Operating Cell temperatures, that the second effect might be the major factor in the overall seasonal efficiency changes. Light-induced annealing, enhanced by the higher radiation levels to which modules are exposed during summer months, might be playing a role as well, adding extra complexity to the effect.