A study on the scaling features for mixing and deflagration potential of stratified layer of hydrogen due to molecular diffusion |
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| Affiliation: | 1. Safety Research Institute, Atomic Energy Regulatory Board, Kalpakkam, India;2. Indira Gandhi Centre for Atomic Research, Kalpakkam, India;3. Department of Mechanical Engineering, Indian Institute of Technology, Madras, India;1. State Key Laboratory of Engines, Tianjin University, 135 Yaguan Rd, 300350 Tianjin, China;2. FEMTO-ST Institute, Univ. Bourgogne Franche-Comté, UTBM, CNRS, Rue Ernest Thierry Mieg, F-90010 Belfort, France;1. National Center for Atmospheric Research (NCAR), Boulder,CO, USA;2. Texas A & M University, College Station, TX, USA;3. Helmholtz Center for Ocean Research, GEOMAR, Kiel, Germany;4. Uni Research Climate, Bjerknes Centre for Climate Research, Bergen, Norway;5. Centre for Australian Weather and Climate Research, a partnership between CSIRO and the Bureau of Meteorology, Commonwealth Scientific and Industrial Research Organisation (CSIRO), Melbourne, Australia;6. NOAA Earth System Research Laboratory, Boulder, CO, USA;7. NASA Goddard Institute for Space Studies (GISS), New York, NY, USA;8. Center for Ocean-Atmospheric Prediction Studies (COAPS), Florida State University, Tallahassee, FL, USA;9. Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique (CERFACS), Toulouse, France;10. National Oceanography Centre Southampton (NOCS), Southampton, UK;11. Alfred Wegener Institute for Polar and Marine Research (AWI), Bremerhaven, Germany;12. Institute of Numerical Mathematics, Russian Academy of Sciences, Moscow, Russia;13. Geophysical Institute, University of Bergen and Bjerknes Centre for Climate Research, Bergen, Norway;14. International Centre for Theoretical Physics (ICTP), Trieste, Italy;15. Mercator-Ocean, Toulouse, France;p. Centro Euro-Mediterraneo sui Cambiamenti Climatici (CMCC), Bologna, Italy;q. Massachusetts Institute of Technology, Cambridge, MA, USA;r. Meteorological Research Institute (MRI), Japan Meteorological Agency, Tsukuba, Japan;s. NOAA Geophysical Fluid Dynamics Laboratory (GFDL), Princeton, NJ, USA;t. Medgar Evers College of the City University of New York, Brooklyn, NY, USA;u. IPSL/LOCEAN, CNRS-IRD-UPMC, Paris, France;v. Istituto Nazionale di Geofisica e Vulcanologia (INGV), Bologna, Italy;w. International CLIVAR Project Office, ICTP, Trieste, Italy;x. Columbia University, New York, NY, USA;y. Centre National de Recherches Météorologiques (CNRM-GAME), Toulouse, France;z. Laboratoire de Physique des Océans, UMR 6523, CNRS-Ifremer-IRD-UBO, IUEM, Plouzane, France;11. Finnish Meteorological Institute, Helsinki, Finland;12. Bedford Institute of Oceanography, Fisheries and Oceans Canada, Dartmouth, Canada;1. International Centre for Theoretical Physics (ICTP), Trieste, Italy;2. Research School of Earth Sciences and ARC Centre of Excellence for Climate System Science, Australian National University (ANU), ACT, Australia;3. NOAA Geophysical Fluid Dynamics Laboratory (GFDL), Princeton, NJ, USA;4. Centre for Australian Weather and Climate Research, a partnership between CSIRO and the Bureau of Meteorology, Aspendale, Australia;5. GEOMAR Helmholtz Centre for Ocean Research Kiel, Germany;6. Uni Research Ltd. Bergen, Norway;7. Center for Ocean-Atmospheric Prediction Studies (COAPS), Florida State University, Tallahassee, USA;8. NASA Goddard Institute for Space Studies (GISS), New York, NY, USA;9. National Center for Atmospheric Research (NCAR), Boulder, CO, USA;10. Alfred Wegener Institute (AWI), Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany;11. Institute of Numerical Mathematics, Russian Academy of Sciences, Moscow, Russia;12. University of Bergen, Bergen, Norway;13. Centro Euro-Mediterraneo sui Cambiamenti Climatici (CMCC), Bologna, Italy;14. Trinnovim LLC, New York, New York, USA;15. Istituto Nazionale di Geofisica e Vulcanologia (INGV), Bologna, Italy;p. National Oceanography Centre Southampton (NOCS), Southampton, UK;q. Meteorological Research Institute (MRI), Japan Meteorological Agency, Tsukuba, Japan;r. Finnish Meteorological Institute, Helsinki, Finland;s. Medgar Evers College of CUNY, New York, NY, USA |
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| Abstract: | Hydrogen deflagration in confined spaces is an important safety issue. The dispersion of a stratified layer of hydrogen due to molecular diffusion is studied. It represents an important class of problems related to long term behaviour of hydrogen release in confined spaces. Diffusion being a slow process, gives an upper bound on the time taken for the stratified layer to mix with air below. A method, based on four indices, namely, average mole fraction (of hydrogen), non-uniformity index, deflagration volume fraction and deflagration pressure ratio, developed recently by the authors, is used to provide vital temporal information on mixing of the stratified layer with air below and formation of flammable cloud in the enclosure. In the present paper, stratified layers of different thickness are considered and the temporal evolutions of the above indices are plotted against diffusion Fourier number. The results in non-dimensional form provide an upper bound of the time that would be required to form a uniform mixture and to attain a state with respect to deflagration potential for enclosures of different sizes. This estimate is an important input for planning mitigation measures before the accident and for post accident investigations. |
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