The Experts below are selected from a list of 90 Experts worldwide ranked by ideXlab platform
Véronique Roig - One of the best experts on this subject based on the ideXlab platform.
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Using a bio-inspired copper complex to investigate reactive mass transfer around an oxygen bubble rising freely in a thin-Gap Cell
Chemical Engineering Science, 2019Co-Authors: Francisco Felis, Véronique Roig, Florian Strassl, Larissa Laurini, Nicolas Dietrich, Anne-marie Billet, Sonja Herres-pawlis, Karine LoubièreAbstract:The present study describes an original colorimetric method to visualize and quantify the local oxygen mass transfer around a rising bubble in reactive media. This method is based on the use of a colorless bio-inspired copper complex, Cu(btmgp)I, specially tailored for the study, which, dissolved in acetonitrile, oxidizes into an orange copper-complex [Cu2O2(btmgp)2]I2. The latter complex, unstable at ambient temperature, decays quite fast into two Cu(II) complexes, leaving a permanent pale-green color as final products. The flow investigated consists in a pure oxygen single bubble rising freely in a confined thin-Gap Cell (400 × 200 × 1 mm). A wide range of motion regimes for the bubbles are observed as the Archimedes number ranges from and the Reynolds number from . A high-resolution 16-bit sCMOS camera, combined with specific filters, is used to capture images from a region-of-interest of the Cell, illuminated by a white LED backlight panel. An ad hoc calibration protocol is developed to correlate the grey-levels from the colored signal to the equivalent oxygen concentrations. This procedure then allows to measure indirectly the amount of oxygen transferred to the liquid phase. The series of images are also treated to identify the bubble motion and properties. Thanks to this method, equivalent oxygen concentration fields, Gap-averaged and time-averaged, can be reached with high precision in the far-field wake of the bubbles, enabling thus to deeply characterize the mass transfer mechanisms under reactive conditions in such confined configuration, and to establish a dimensionless representation in terms of Sherwood number versus Peclet number. At last, thanks to the knowledge of the kinetic rate of the reaction and of the diffusion coefficients, the Hatta number and the enhancement factor are estimated, and thus the intrinsic Sherwood numbers; these results demonstrate that the enhancement of the mass transfer by the reactions involved with the copper-complexes is not negligible (almost 12–15%).
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oscillatory motion and wake of a bubble rising in a thin Gap Cell
Journal of Fluid Mechanics, 2015Co-Authors: Audrey Filella, Patricia Ern, Véronique RoigAbstract:We investigate the characteristics of the oscillatory motion and wake of confined bubbles freely rising in a thin-Gap Cell (h=3.1 mm width). Once the diameter d of the bubble in the plane of the Cell is known, the mean vertical velocity of the bubble Vb is proportional to the gravitational velocity [...], where g is the gravitational acceleration. This velocity is used to build the Reynolds number [...] that characterizes the flow induced by the bubble in the surrounding liquid (of kinematic viscosity ν), and which determines at leading order the mean deformation of the bubble given by the aspect ratio χ of the ellipse equivalent to the bubble contour. We then show that in the reference frame associated with the bubble (having a fixed origin and axes corresponding to the minor and major axes of the equivalent ellipse) the characteristics of its oscillatory motion in the plane of the Cell display remarkable properties in the range 1200
Karine Loubière - One of the best experts on this subject based on the ideXlab platform.
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Using a bio-inspired copper complex to investigate reactive mass transfer around an oxygen bubble rising freely in a thin-Gap Cell
Chemical Engineering Science, 2019Co-Authors: Francisco Felis, Véronique Roig, Florian Strassl, Larissa Laurini, Nicolas Dietrich, Anne-marie Billet, Sonja Herres-pawlis, Karine LoubièreAbstract:The present study describes an original colorimetric method to visualize and quantify the local oxygen mass transfer around a rising bubble in reactive media. This method is based on the use of a colorless bio-inspired copper complex, Cu(btmgp)I, specially tailored for the study, which, dissolved in acetonitrile, oxidizes into an orange copper-complex [Cu2O2(btmgp)2]I2. The latter complex, unstable at ambient temperature, decays quite fast into two Cu(II) complexes, leaving a permanent pale-green color as final products. The flow investigated consists in a pure oxygen single bubble rising freely in a confined thin-Gap Cell (400 × 200 × 1 mm). A wide range of motion regimes for the bubbles are observed as the Archimedes number ranges from and the Reynolds number from . A high-resolution 16-bit sCMOS camera, combined with specific filters, is used to capture images from a region-of-interest of the Cell, illuminated by a white LED backlight panel. An ad hoc calibration protocol is developed to correlate the grey-levels from the colored signal to the equivalent oxygen concentrations. This procedure then allows to measure indirectly the amount of oxygen transferred to the liquid phase. The series of images are also treated to identify the bubble motion and properties. Thanks to this method, equivalent oxygen concentration fields, Gap-averaged and time-averaged, can be reached with high precision in the far-field wake of the bubbles, enabling thus to deeply characterize the mass transfer mechanisms under reactive conditions in such confined configuration, and to establish a dimensionless representation in terms of Sherwood number versus Peclet number. At last, thanks to the knowledge of the kinetic rate of the reaction and of the diffusion coefficients, the Hatta number and the enhancement factor are estimated, and thus the intrinsic Sherwood numbers; these results demonstrate that the enhancement of the mass transfer by the reactions involved with the copper-complexes is not negligible (almost 12–15%).
Francisco Felis - One of the best experts on this subject based on the ideXlab platform.
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Using a bio-inspired copper complex to investigate reactive mass transfer around an oxygen bubble rising freely in a thin-Gap Cell
Chemical Engineering Science, 2019Co-Authors: Francisco Felis, Véronique Roig, Florian Strassl, Larissa Laurini, Nicolas Dietrich, Anne-marie Billet, Sonja Herres-pawlis, Karine LoubièreAbstract:The present study describes an original colorimetric method to visualize and quantify the local oxygen mass transfer around a rising bubble in reactive media. This method is based on the use of a colorless bio-inspired copper complex, Cu(btmgp)I, specially tailored for the study, which, dissolved in acetonitrile, oxidizes into an orange copper-complex [Cu2O2(btmgp)2]I2. The latter complex, unstable at ambient temperature, decays quite fast into two Cu(II) complexes, leaving a permanent pale-green color as final products. The flow investigated consists in a pure oxygen single bubble rising freely in a confined thin-Gap Cell (400 × 200 × 1 mm). A wide range of motion regimes for the bubbles are observed as the Archimedes number ranges from and the Reynolds number from . A high-resolution 16-bit sCMOS camera, combined with specific filters, is used to capture images from a region-of-interest of the Cell, illuminated by a white LED backlight panel. An ad hoc calibration protocol is developed to correlate the grey-levels from the colored signal to the equivalent oxygen concentrations. This procedure then allows to measure indirectly the amount of oxygen transferred to the liquid phase. The series of images are also treated to identify the bubble motion and properties. Thanks to this method, equivalent oxygen concentration fields, Gap-averaged and time-averaged, can be reached with high precision in the far-field wake of the bubbles, enabling thus to deeply characterize the mass transfer mechanisms under reactive conditions in such confined configuration, and to establish a dimensionless representation in terms of Sherwood number versus Peclet number. At last, thanks to the knowledge of the kinetic rate of the reaction and of the diffusion coefficients, the Hatta number and the enhancement factor are estimated, and thus the intrinsic Sherwood numbers; these results demonstrate that the enhancement of the mass transfer by the reactions involved with the copper-complexes is not negligible (almost 12–15%).
Charles W. Dunnill - One of the best experts on this subject based on the ideXlab platform.
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minimising the ohmic resistance of an alkaline electrolysis Cell through effective Cell design
International Journal of Hydrogen Energy, 2017Co-Authors: Robert Phillips, Adam Edwards, Bertrand Rome, Daniel R. Jones, Charles W. DunnillAbstract:Abstract The efficiency of an alkaline electrolysis Cell depends strongly on its internal Cell resistance, which becomes the dominant efficiency driver at high current densities. This paper uses Electrochemical Impedance Spectroscopy to decouple the ohmic resistance from the Cell voltage, and, for the first time, quantify the reduction in Cell resistance achieved by employing a zero Gap Cell configuration when compared to the conventional approach. A 30% reduction in ohmic resistance is demonstrated for the zero Gap Cell when compared to a more conventional design with a 2 mm electrode Gap (in 1 M NaOH and at standard conditions). The effect on the ohmic resistance of operating parameters, including current density and temperature, is quantified; the zero Gap Cell outperforms the standard Cell at all current densities, particularly above 500 mA·cm −2 Furthermore, the effect of electrode morphology on the ohmic resistance is investigated, showing that high surface area foam electrodes permit a lower ohmic resistance than coarser mesh electrodes. These results show that zero Gap Cell design will allow both low cost and highly efficient alkaline electrolysis, which will become a key technology for short term and inter-seasonal energy storage and accelerate the transition towards a decarbonised society.
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zero Gap alkaline electrolysis Cell design for renewable energy storage as hydrogen gas
RSC Advances, 2016Co-Authors: Robert Phillips, Charles W. DunnillAbstract:Zero Gap alkaline electrolysers hold the key to cheap and efficient renewable energy storage via the production and distribution of hydrogen gas. A zero Gap design, where porous electrodes are spacially separated only by the gas separator, allows the unique benefits of alkaline electrolysis to be combined with the high efficiencies currently only associated with the more expensive PEM set-up. This review covers the basics of alkaline electrolysis, and provides a detailed description of the advantages of employing a zero Gap Cell design over the traditional arrangement. A comparison with different types of zero Gap Cell designs currently seen in research is made, and a description of recent developments is presented. Finally, the current state of research into zero Gap alkaline electrolysis is discussed, and pathways for future research identified. Zero Gap alkaline electrolysis will allow excess renewable energy to be stored, transported and used on demand in a green and environmentally friendly manner as when the hydrogen is burnt or passed into a fuel Cell it produces only water and energy.
Florian Strassl - One of the best experts on this subject based on the ideXlab platform.
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Using a bio-inspired copper complex to investigate reactive mass transfer around an oxygen bubble rising freely in a thin-Gap Cell
Chemical Engineering Science, 2019Co-Authors: Francisco Felis, Véronique Roig, Florian Strassl, Larissa Laurini, Nicolas Dietrich, Anne-marie Billet, Sonja Herres-pawlis, Karine LoubièreAbstract:The present study describes an original colorimetric method to visualize and quantify the local oxygen mass transfer around a rising bubble in reactive media. This method is based on the use of a colorless bio-inspired copper complex, Cu(btmgp)I, specially tailored for the study, which, dissolved in acetonitrile, oxidizes into an orange copper-complex [Cu2O2(btmgp)2]I2. The latter complex, unstable at ambient temperature, decays quite fast into two Cu(II) complexes, leaving a permanent pale-green color as final products. The flow investigated consists in a pure oxygen single bubble rising freely in a confined thin-Gap Cell (400 × 200 × 1 mm). A wide range of motion regimes for the bubbles are observed as the Archimedes number ranges from and the Reynolds number from . A high-resolution 16-bit sCMOS camera, combined with specific filters, is used to capture images from a region-of-interest of the Cell, illuminated by a white LED backlight panel. An ad hoc calibration protocol is developed to correlate the grey-levels from the colored signal to the equivalent oxygen concentrations. This procedure then allows to measure indirectly the amount of oxygen transferred to the liquid phase. The series of images are also treated to identify the bubble motion and properties. Thanks to this method, equivalent oxygen concentration fields, Gap-averaged and time-averaged, can be reached with high precision in the far-field wake of the bubbles, enabling thus to deeply characterize the mass transfer mechanisms under reactive conditions in such confined configuration, and to establish a dimensionless representation in terms of Sherwood number versus Peclet number. At last, thanks to the knowledge of the kinetic rate of the reaction and of the diffusion coefficients, the Hatta number and the enhancement factor are estimated, and thus the intrinsic Sherwood numbers; these results demonstrate that the enhancement of the mass transfer by the reactions involved with the copper-complexes is not negligible (almost 12–15%).
