Abonnement à la biblothèque: Guest
Portail numérique Bibliothèque numérique eBooks Revues Références et comptes rendus Collections
Journal of Porous Media
Facteur d'impact: 1.49 Facteur d'impact sur 5 ans: 1.159 SJR: 0.43 SNIP: 0.671 CiteScore™: 1.58

ISSN Imprimer: 1091-028X
ISSN En ligne: 1934-0508

Volumes:
Volume 22, 2019 Volume 21, 2018 Volume 20, 2017 Volume 19, 2016 Volume 18, 2015 Volume 17, 2014 Volume 16, 2013 Volume 15, 2012 Volume 14, 2011 Volume 13, 2010 Volume 12, 2009 Volume 11, 2008 Volume 10, 2007 Volume 9, 2006 Volume 8, 2005 Volume 7, 2004 Volume 6, 2003 Volume 5, 2002 Volume 4, 2001 Volume 3, 2000 Volume 2, 1999 Volume 1, 1998

Journal of Porous Media

DOI: 10.1615/JPorMedia.v8.i2.60
pages 175-191

Radon-222 Exhalation Rates from Phosphogypsum-Bearing Embankment Subjected to Constant Temperature and Fixed Activity Concentration

J. A. Rabi
Faculty of Zootechny and Food Engineering, University of Sao Paulo, Av. Duque de Caxias Norte, 225, Pirassununga, SP, 13635-900, Brazil

RÉSUMÉ

Stack or embankment disposal of phosphogypsum — a by-product from phosphate fertilizer industries-has given rise to environmental issues concerning 222Rn exhalation rates into the local atmosphere. Early models for radon transport in porous media have considered both diffusion and convection, although basically taking into account air flow driven by predefined pressure differences and Darcy's law. The present paper introduces buoyant effects and outlines a steady-state two-dimensional model for 222Rn transport through a phosphogypsum-bearing embankment, inside of which there are sources and sinks for this gaseous radionuclide. The embankment is treated as an open cavity filled with porous material and surrounded by isothermal and impermeable ground. Its top surface is subjected to fixed activity concentration and fixed lower temperature. Buoyancy-driven interstitial air flow is supposedly laminar and modeled according to Darcy-Brinkman-Boussinesq formulation. Governing equations are written in dimensionless form in order to account for concurrent effects of the various physical parameters involved, and three unconventional dimensionless groups are put forward apart from usual controlling parameters, such as Darcy, Grashof, Prandtl, and Schmidt numbers. An analytical solution regarding a strictly diffusive approach is inferred, whereas full model equations are solved numerically by adapting an existing finite-volume simulator. As a preliminary investigation, results are reported for Pr = 0.71 and Sc = 15, while Da and Gr are allowed to vary from 10−7 to 10−13 and from 107 to 109 , respectively. Results are also presented as a function of the modified Grashof number Grm = Gr·Da. For porous media with relatively low permeability (Da ≤ 10−9), 222Rn transport is diffusion dominated (i.e., natural convective effects play a minor role) and both Nusselt and Sherwood numbers prove to be insensitive to Grashof number. At approximately Grm ≈ 10, circulation cell splitting occurs within each embankment half, as the natural convective fluid flow increases its strength, which results in very low 222Rn concentration levels inside the porous matrix.


Articles with similar content:

THREE-DIMENSIONAL STUDY OF PERMEABILITY EFFECT ON CONVECTION IN HETEROGENEOUS POROUS MEDIUM FILLED WITH A TERNARYN HYDROCARBON MIXTURE
Journal of Porous Media, Vol.14, 2011, issue 4
M. Ziad Saghir, T. J. Jaber
MODELING OF THERMALLY-DRIVEN TRANSPORT IN INTERIOR SPACES FOR APPLICATIONS TO ZONAL MIXING MODELS
International Heat Transfer Conference 13, Vol.0, 2006, issue
Gregory H. Evans, Ralph Greif, W. Winters
DOUBLE-DIFFUSIVE MIXED CONVECTION IN A COMPOSITE POROUS ENCLOSURE WITH ARC-SHAPED MOVING WALL: TORTUOSITY EFFECT
Journal of Porous Media, Vol.21, 2018, issue 4
Muneer A. Ismael
FREE CONVECTION ACROSS A BILAYERED AND INCLINED POROUS CAVITY SUBMITTED TO NONSYMMETRICAL HEATING
Journal of Porous Media, Vol.15, 2012, issue 5
Yacine Ould-Amer, Rachid Bennacer
MIXED CONVECTION AND ENTROPY GENERATION IN A POROUS DEEP CAVITY: EFFECT OF UNIFORM AND NONUNIFORM HEATED WALLS
Journal of Porous Media, Vol.19, 2016, issue 6
Swapan K. Pandit, Anirban Chattopadhyay