The Experts below are selected from a list of 8463 Experts worldwide ranked by ideXlab platform
Tissa H Illangasekare - One of the best experts on this subject based on the ideXlab platform.
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Comparison of height-Averaged and point-measured capillary pressure-Saturation relations for sands using a modified Tempe cell
Water Resources Research, 2007Co-Authors: Toshihiro Sakaki, Tissa H IllangasekareAbstract:[1] Tempe cells and similar devices are often used for measurements of capillary pressure versus Saturation relationships (retention curves) of soils. Average Water Saturation within the sample is often used as the representative Saturation. For cases where the Saturation distribution along the cell height is nonuniform, use of the height-Averaged Water Saturation artificially smoothes the retention curve when the capillary pressure head reaches the displacement pressure head. This leads to an inaccurate representation of the retention curve in flow modeling. For nine test sands with a wide range of displacement pressure head values (6-78 cm of Water), height-Averaged and point-measured retention curves were simultaneously obtained to investigate the effect of the height-averaging procedure. A Tempe cell was used, which was modified by installing a small time domain reflectometry probe and a tensiometer at the midpoint of the sample height to measure Water Saturation and pressure, respectively. When the sample height is large relative to the displacement pressure head, the bulk drainage (initial drainage at the top of the sample) leads to inaccuracies in the determination of retention curves. For such cases, point-measured Saturation should be used, otherwise height correction is necessary.
Toshihiro Sakaki - One of the best experts on this subject based on the ideXlab platform.
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Comparison of height-Averaged and point-measured capillary pressure-Saturation relations for sands using a modified Tempe cell
Water Resources Research, 2007Co-Authors: Toshihiro Sakaki, Tissa H IllangasekareAbstract:[1] Tempe cells and similar devices are often used for measurements of capillary pressure versus Saturation relationships (retention curves) of soils. Average Water Saturation within the sample is often used as the representative Saturation. For cases where the Saturation distribution along the cell height is nonuniform, use of the height-Averaged Water Saturation artificially smoothes the retention curve when the capillary pressure head reaches the displacement pressure head. This leads to an inaccurate representation of the retention curve in flow modeling. For nine test sands with a wide range of displacement pressure head values (6-78 cm of Water), height-Averaged and point-measured retention curves were simultaneously obtained to investigate the effect of the height-averaging procedure. A Tempe cell was used, which was modified by installing a small time domain reflectometry probe and a tensiometer at the midpoint of the sample height to measure Water Saturation and pressure, respectively. When the sample height is large relative to the displacement pressure head, the bulk drainage (initial drainage at the top of the sample) leads to inaccuracies in the determination of retention curves. For such cases, point-measured Saturation should be used, otherwise height correction is necessary.
Yulin Wang - One of the best experts on this subject based on the ideXlab platform.
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investigation of the through plane effective oxygen diffusivity in the porous media of pem fuel cells effects of the pore size distribution and Water Saturation distribution
International Journal of Heat and Mass Transfer, 2016Co-Authors: Shixue Wang, Yulin WangAbstract:Abstract A thorough understanding of the oxygen transport properties in the gas diffusion layers (GDLs) of polymer electrolyte membrane (PEM) fuel cells is crucial for improving cell performance. However, because of the complex pore structure of the GDLs and the presence of Water in them, the effective oxygen diffusivity (EOD) in porous medium of a PEM fuel cell is still not precisely understood. In this paper, the EODs were measured in two typical porous materials (TGP-H-120 carbon paper and carbon cloth, commonly used as GDLs) by using an oxygen sensor based on a galvanic cell under both dry and partially saturated conditions. The measurements were performed for various pore size distributions (PSDs) and Water Saturation distributions (WSDs); different PSDs were obtained by increasing the PTFE loading and different WSDs were realized via two impregnation methods using liquid Water, namely vacuum impregnation and moist air condensation impregnation. The EOD was found to strongly depend on the PSD and WSD in the GDL, not simply on the Average porosity and Average Water Saturation, as reported in previous studies. Finally, this paper presents the experimentally verified equations that account for PSDs and WSDs under both dry and partially saturated conditions for the prediction of the EODs in PEM fuel cells.
Trung Van Nguye - One of the best experts on this subject based on the ideXlab platform.
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three dimensional simulation of liquid Water distribution in a pemfc with experimentally measured capillary functions
Journal of The Electrochemical Society, 2007Co-Authors: Trung Van NguyeAbstract:Modeling of liquid Water distribution in polymer electrolyte membrane fuel cells (PEMFCs) is challenged by uncertainties in characterizing the two-phase transport properties of the porous transport layer (PTL) and the catalyst layer (CL). Capillary pressure, representing both pore structures and wetting features of the porous media, is a key factor in controlling liquid Water transport and distribution in the porous electrode of PEMFCs. By incorporating experimentally measured capillary pressure functions, a single-domain, three-dimensional, and two-phase transport model was developed to predict liquid Water Saturation in the PTL and CL of a PEMFC with long straight channels, where the two-phase flow complications were minimized at practical stoichiometry. In the cathode CL, the liquid Water Saturation was found to be higher under the channel than that under the ribs at high current densities. In the cathode PTL, however, the liquid Water Saturation level was observed to be lower under the channel than that under the ribs. At high current densities, the Average Water Saturation levels are insensitive to current density and fall in the range of 0.4-0.5 in the CL and 0.2-0.3 in the PTL. Finally, the effects of liquid Water on oxygen transport and cell performance were investigated.
Shixue Wang - One of the best experts on this subject based on the ideXlab platform.
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investigation of the through plane effective oxygen diffusivity in the porous media of pem fuel cells effects of the pore size distribution and Water Saturation distribution
International Journal of Heat and Mass Transfer, 2016Co-Authors: Shixue Wang, Yulin WangAbstract:Abstract A thorough understanding of the oxygen transport properties in the gas diffusion layers (GDLs) of polymer electrolyte membrane (PEM) fuel cells is crucial for improving cell performance. However, because of the complex pore structure of the GDLs and the presence of Water in them, the effective oxygen diffusivity (EOD) in porous medium of a PEM fuel cell is still not precisely understood. In this paper, the EODs were measured in two typical porous materials (TGP-H-120 carbon paper and carbon cloth, commonly used as GDLs) by using an oxygen sensor based on a galvanic cell under both dry and partially saturated conditions. The measurements were performed for various pore size distributions (PSDs) and Water Saturation distributions (WSDs); different PSDs were obtained by increasing the PTFE loading and different WSDs were realized via two impregnation methods using liquid Water, namely vacuum impregnation and moist air condensation impregnation. The EOD was found to strongly depend on the PSD and WSD in the GDL, not simply on the Average porosity and Average Water Saturation, as reported in previous studies. Finally, this paper presents the experimentally verified equations that account for PSDs and WSDs under both dry and partially saturated conditions for the prediction of the EODs in PEM fuel cells.
