The Experts below are selected from a list of 32877 Experts worldwide ranked by ideXlab platform
Svetlozar Velizarov - One of the best experts on this subject based on the ideXlab platform.
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mass transfer in reverse electrodialysis flow entrance effects and diffusion Boundary Layer Thickness
Journal of Membrane Science, 2014Co-Authors: Sylwin Pawlowski, Philippe Sistat, Joao G Crespo, Svetlozar VelizarovAbstract:Abstract Power generation by reverse electrodialysis (RED) depends on ionic mass transfer through alternately arranged cation- and anion-exchange membranes. Chronopotentiometric measurements were carried out in an EDR-Z Mini stack (MEGA a.s.), equipped with Ralex heterogeneous membranes, separated by either sheet flow spacers or mesh-free gaskets. Various concentrations of model NaCl solutions were used to study the ohmic and non-ohmic resistances in the stack under different hydrodynamic conditions. In order to eliminate the uncertainties associated with a non-uniform distribution of the applied current over the membrane surface, the relaxation zone of the obtained chronopotentiograms was used to estimate the diffusion Boundary Layer Thickness. It was found that this approach provide more accurate data under RED operating conditions, which are strongly influenced by entrance effects on mass transfer, especially for a spacer-free channel configuration. For shorter flow channels, since the salt concentration profile across the diffusion Boundary Layer is not yet fully developed, more power can be obtained than in the case of longer channels. The presence of spacers was found to reduce the Boundary Layer Thickness, but also increased the ohmic resistance, due to their shadow effect over the membrane surface. The description of the impact of flow entrance effects on mass transfer, and therefore on diffusion Boundary Layer Thickness, can be useful for characterization and further design and/or optimization of RED stacks performance.
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mass transfer in reverse electrodialysis flow entrance effects and diffusion Boundary Layer Thickness
Journal of Membrane Science, 2014Co-Authors: Sylwin Pawlowski, Philippe Sistat, Joao G Crespo, Svetlozar VelizarovAbstract:Abstract Power generation by reverse electrodialysis (RED) depends on ionic mass transfer through alternately arranged cation- and anion-exchange membranes. Chronopotentiometric measurements were carried out in an EDR-Z Mini stack (MEGA a.s.), equipped with Ralex heterogeneous membranes, separated by either sheet flow spacers or mesh-free gaskets. Various concentrations of model NaCl solutions were used to study the ohmic and non-ohmic resistances in the stack under different hydrodynamic conditions. In order to eliminate the uncertainties associated with a non-uniform distribution of the applied current over the membrane surface, the relaxation zone of the obtained chronopotentiograms was used to estimate the diffusion Boundary Layer Thickness. It was found that this approach provide more accurate data under RED operating conditions, which are strongly influenced by entrance effects on mass transfer, especially for a spacer-free channel configuration. For shorter flow channels, since the salt concentration profile across the diffusion Boundary Layer is not yet fully developed, more power can be obtained than in the case of longer channels. The presence of spacers was found to reduce the Boundary Layer Thickness, but also increased the ohmic resistance, due to their shadow effect over the membrane surface. The description of the impact of flow entrance effects on mass transfer, and therefore on diffusion Boundary Layer Thickness, can be useful for characterization and further design and/or optimization of RED stacks performance.
Sylwin Pawlowski - One of the best experts on this subject based on the ideXlab platform.
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mass transfer in reverse electrodialysis flow entrance effects and diffusion Boundary Layer Thickness
Journal of Membrane Science, 2014Co-Authors: Sylwin Pawlowski, Philippe Sistat, Joao G Crespo, Svetlozar VelizarovAbstract:Abstract Power generation by reverse electrodialysis (RED) depends on ionic mass transfer through alternately arranged cation- and anion-exchange membranes. Chronopotentiometric measurements were carried out in an EDR-Z Mini stack (MEGA a.s.), equipped with Ralex heterogeneous membranes, separated by either sheet flow spacers or mesh-free gaskets. Various concentrations of model NaCl solutions were used to study the ohmic and non-ohmic resistances in the stack under different hydrodynamic conditions. In order to eliminate the uncertainties associated with a non-uniform distribution of the applied current over the membrane surface, the relaxation zone of the obtained chronopotentiograms was used to estimate the diffusion Boundary Layer Thickness. It was found that this approach provide more accurate data under RED operating conditions, which are strongly influenced by entrance effects on mass transfer, especially for a spacer-free channel configuration. For shorter flow channels, since the salt concentration profile across the diffusion Boundary Layer is not yet fully developed, more power can be obtained than in the case of longer channels. The presence of spacers was found to reduce the Boundary Layer Thickness, but also increased the ohmic resistance, due to their shadow effect over the membrane surface. The description of the impact of flow entrance effects on mass transfer, and therefore on diffusion Boundary Layer Thickness, can be useful for characterization and further design and/or optimization of RED stacks performance.
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mass transfer in reverse electrodialysis flow entrance effects and diffusion Boundary Layer Thickness
Journal of Membrane Science, 2014Co-Authors: Sylwin Pawlowski, Philippe Sistat, Joao G Crespo, Svetlozar VelizarovAbstract:Abstract Power generation by reverse electrodialysis (RED) depends on ionic mass transfer through alternately arranged cation- and anion-exchange membranes. Chronopotentiometric measurements were carried out in an EDR-Z Mini stack (MEGA a.s.), equipped with Ralex heterogeneous membranes, separated by either sheet flow spacers or mesh-free gaskets. Various concentrations of model NaCl solutions were used to study the ohmic and non-ohmic resistances in the stack under different hydrodynamic conditions. In order to eliminate the uncertainties associated with a non-uniform distribution of the applied current over the membrane surface, the relaxation zone of the obtained chronopotentiograms was used to estimate the diffusion Boundary Layer Thickness. It was found that this approach provide more accurate data under RED operating conditions, which are strongly influenced by entrance effects on mass transfer, especially for a spacer-free channel configuration. For shorter flow channels, since the salt concentration profile across the diffusion Boundary Layer is not yet fully developed, more power can be obtained than in the case of longer channels. The presence of spacers was found to reduce the Boundary Layer Thickness, but also increased the ohmic resistance, due to their shadow effect over the membrane surface. The description of the impact of flow entrance effects on mass transfer, and therefore on diffusion Boundary Layer Thickness, can be useful for characterization and further design and/or optimization of RED stacks performance.
O Samimiabianeh - One of the best experts on this subject based on the ideXlab platform.
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dual perspective Boundary Layer Thickness measurements using filtered natural emissions of species
Experimental Thermal and Fluid Science, 2021Co-Authors: J A Piehl, O SamimiabianehAbstract:Abstract Boundary Layer Thickness measurements have been taken via spectroscopic methods in the past, but were traditionally limited to a single point of view due to the need of an excitation source (such as a laser) and a detector. A new optical technique that measures the broadband filtered natural emissions of species does not require an excitation source to measure the Boundary Layer and thus can be used in multiple perspectives. In this work, two mid-wavelength infrared cameras are used to determine the Boundary Layer Thickness on two inside surfaces of a rapid compression machine based on the emission from a gaseous mixture of N2, CO and CO2. The experiments were performed at two different gas pressures of 5.1 and 9.9 bar, and with gas temperatures of approximately 666 and 669 K, respectively. The wavelength ranges of 4.35–4.55, 4.545–4.785 and 4.069–4.445 μm were used to determine the Boundary Layer Thicknesses at the side and front optical access of the rapid compression machine.
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gas temperature and Boundary Layer Thickness measurements of an inert mixture using filtered broadband natural emission of species at rapid compression machine conditions part ii
Experimental Thermal and Fluid Science, 2020Co-Authors: O Samimiabianeh, M Alsadoon, Luis BravoAbstract:Abstract Our understanding of the combustion process is hindered by the Boundary Layer at the optical access. To be detected by the camera, the infrared emission of the mixture (or the laser) should pass the Boundary Layer at the window of the combustion system. Regardless of the type of experimental techniques used (either the laser or natural emission of the species), part of the emission could be absorbed by the Boundary Layer due to its low temperature. Hence, the measured data includes some uncertainty and errors due to the Boundary-Layer absorption and its Thickness (it reduces the optical length), which have not yet been quantified due to the unavailability of the Boundary Layer Thickness, especially during a transient process such as engine compression stroke. A new methodology was used to measure the gas mixture temperature and Boundary Layer Thickness using the Rapid Compression Machine (RCM). The methodology is based on filtering and measuring the infrared natural emission of the species at two different band-pass wavelength ranges. The new methodology was applied to measure the gas temperature and Boundary Layer Thickness by measuring the filtered infrared emission of methane, carbon monoxide and carbon dioxide at two compressed gas pressures and two compressed gas temperatures in this work. The measured and modeled gas temperatures were compared during the post compression. An excellent agreement within 1% between the measured and modeled gas temperatures were reached at all of the studied conditions.
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gas temperature and Boundary Layer Thickness measurements of an inert mixture using filtered broadband natural species emission part i
Journal of Quantitative Spectroscopy & Radiative Transfer, 2020Co-Authors: M Alsadoon, O SamimiabianehAbstract:Abstract A new experimental methodology to simultaneously measure gas temperature and Boundary Layer Thickness was developed and explained for the first time in this work. The new methodology is based on the line-of-sight broadband filtered natural infrared emission of species and it solves one of the main challenges of using the broadband spectroscopy to measure gas temperatures: quantification of the absorption of the core gas infrared emission due to the cold Boundary Layer on the optical access of combustion systems. To evaluate and validate the new methodology, it was applied to measure the gas temperature and Boundary Layer Thickness of a mixture of methane, carbon dioxide, and nitrogen using Rapid Compression Machine RCM). High-speed infrared cameras with two filters at wavelength ranges of 3.329 to 3.629 μm and 4.069 to 4.445 μm were used to measure the filtered natural emission of methane and carbon dioxide during the post-compression period. Measured gas temperatures at two conditions were compared with the modeled temperature calculated using the isentropic compression equation. Excellent agreement, within 1%, was reached between modeled and measured gas temperatures.
Philippe Sistat - One of the best experts on this subject based on the ideXlab platform.
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mass transfer in reverse electrodialysis flow entrance effects and diffusion Boundary Layer Thickness
Journal of Membrane Science, 2014Co-Authors: Sylwin Pawlowski, Philippe Sistat, Joao G Crespo, Svetlozar VelizarovAbstract:Abstract Power generation by reverse electrodialysis (RED) depends on ionic mass transfer through alternately arranged cation- and anion-exchange membranes. Chronopotentiometric measurements were carried out in an EDR-Z Mini stack (MEGA a.s.), equipped with Ralex heterogeneous membranes, separated by either sheet flow spacers or mesh-free gaskets. Various concentrations of model NaCl solutions were used to study the ohmic and non-ohmic resistances in the stack under different hydrodynamic conditions. In order to eliminate the uncertainties associated with a non-uniform distribution of the applied current over the membrane surface, the relaxation zone of the obtained chronopotentiograms was used to estimate the diffusion Boundary Layer Thickness. It was found that this approach provide more accurate data under RED operating conditions, which are strongly influenced by entrance effects on mass transfer, especially for a spacer-free channel configuration. For shorter flow channels, since the salt concentration profile across the diffusion Boundary Layer is not yet fully developed, more power can be obtained than in the case of longer channels. The presence of spacers was found to reduce the Boundary Layer Thickness, but also increased the ohmic resistance, due to their shadow effect over the membrane surface. The description of the impact of flow entrance effects on mass transfer, and therefore on diffusion Boundary Layer Thickness, can be useful for characterization and further design and/or optimization of RED stacks performance.
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mass transfer in reverse electrodialysis flow entrance effects and diffusion Boundary Layer Thickness
Journal of Membrane Science, 2014Co-Authors: Sylwin Pawlowski, Philippe Sistat, Joao G Crespo, Svetlozar VelizarovAbstract:Abstract Power generation by reverse electrodialysis (RED) depends on ionic mass transfer through alternately arranged cation- and anion-exchange membranes. Chronopotentiometric measurements were carried out in an EDR-Z Mini stack (MEGA a.s.), equipped with Ralex heterogeneous membranes, separated by either sheet flow spacers or mesh-free gaskets. Various concentrations of model NaCl solutions were used to study the ohmic and non-ohmic resistances in the stack under different hydrodynamic conditions. In order to eliminate the uncertainties associated with a non-uniform distribution of the applied current over the membrane surface, the relaxation zone of the obtained chronopotentiograms was used to estimate the diffusion Boundary Layer Thickness. It was found that this approach provide more accurate data under RED operating conditions, which are strongly influenced by entrance effects on mass transfer, especially for a spacer-free channel configuration. For shorter flow channels, since the salt concentration profile across the diffusion Boundary Layer is not yet fully developed, more power can be obtained than in the case of longer channels. The presence of spacers was found to reduce the Boundary Layer Thickness, but also increased the ohmic resistance, due to their shadow effect over the membrane surface. The description of the impact of flow entrance effects on mass transfer, and therefore on diffusion Boundary Layer Thickness, can be useful for characterization and further design and/or optimization of RED stacks performance.
Joao G Crespo - One of the best experts on this subject based on the ideXlab platform.
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mass transfer in reverse electrodialysis flow entrance effects and diffusion Boundary Layer Thickness
Journal of Membrane Science, 2014Co-Authors: Sylwin Pawlowski, Philippe Sistat, Joao G Crespo, Svetlozar VelizarovAbstract:Abstract Power generation by reverse electrodialysis (RED) depends on ionic mass transfer through alternately arranged cation- and anion-exchange membranes. Chronopotentiometric measurements were carried out in an EDR-Z Mini stack (MEGA a.s.), equipped with Ralex heterogeneous membranes, separated by either sheet flow spacers or mesh-free gaskets. Various concentrations of model NaCl solutions were used to study the ohmic and non-ohmic resistances in the stack under different hydrodynamic conditions. In order to eliminate the uncertainties associated with a non-uniform distribution of the applied current over the membrane surface, the relaxation zone of the obtained chronopotentiograms was used to estimate the diffusion Boundary Layer Thickness. It was found that this approach provide more accurate data under RED operating conditions, which are strongly influenced by entrance effects on mass transfer, especially for a spacer-free channel configuration. For shorter flow channels, since the salt concentration profile across the diffusion Boundary Layer is not yet fully developed, more power can be obtained than in the case of longer channels. The presence of spacers was found to reduce the Boundary Layer Thickness, but also increased the ohmic resistance, due to their shadow effect over the membrane surface. The description of the impact of flow entrance effects on mass transfer, and therefore on diffusion Boundary Layer Thickness, can be useful for characterization and further design and/or optimization of RED stacks performance.
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mass transfer in reverse electrodialysis flow entrance effects and diffusion Boundary Layer Thickness
Journal of Membrane Science, 2014Co-Authors: Sylwin Pawlowski, Philippe Sistat, Joao G Crespo, Svetlozar VelizarovAbstract:Abstract Power generation by reverse electrodialysis (RED) depends on ionic mass transfer through alternately arranged cation- and anion-exchange membranes. Chronopotentiometric measurements were carried out in an EDR-Z Mini stack (MEGA a.s.), equipped with Ralex heterogeneous membranes, separated by either sheet flow spacers or mesh-free gaskets. Various concentrations of model NaCl solutions were used to study the ohmic and non-ohmic resistances in the stack under different hydrodynamic conditions. In order to eliminate the uncertainties associated with a non-uniform distribution of the applied current over the membrane surface, the relaxation zone of the obtained chronopotentiograms was used to estimate the diffusion Boundary Layer Thickness. It was found that this approach provide more accurate data under RED operating conditions, which are strongly influenced by entrance effects on mass transfer, especially for a spacer-free channel configuration. For shorter flow channels, since the salt concentration profile across the diffusion Boundary Layer is not yet fully developed, more power can be obtained than in the case of longer channels. The presence of spacers was found to reduce the Boundary Layer Thickness, but also increased the ohmic resistance, due to their shadow effect over the membrane surface. The description of the impact of flow entrance effects on mass transfer, and therefore on diffusion Boundary Layer Thickness, can be useful for characterization and further design and/or optimization of RED stacks performance.