Documents disponibles écrits par cet auteur

Analysis of water transmembrane profiles and ionic transport during proton exchange membrane fuel cell transient behavior / Javier Parrondo in Industrial & engineering chemistry research, Vol. 47 N° 13 (Juillet 2008) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 47 N° 13 (Juillet 2008) . - p. 4481–4489 Titre : Analysis of water transmembrane profiles and ionic transport during proton exchange membrane fuel cell transient behavior Type de document : texte imprimé Auteurs : Javier Parrondo, Auteur ; Arantxa Barrio, Auteur ; Jose Lombraña, Auteur ; Federico Mijangos, Auteur Année de publication : 2008 Article en page(s) : p. 4481–4489 Note générale : Bibliogr. p. 4488-4489 Langues : Anglais (eng) Mots-clés : Transmembrane  water  profiles;  Current−voltage  curves;  Electrochemical  reaction Résumé : A one-dimensional isothermal model is used to calculate transmembrane water profiles and current−voltage curves under different operating conditions. The mechanistic model solves the mass balance over the system, basically by considering the main source-sink terms and transport contributions: fuel and air humidity, water generated by the electrochemical reaction; water concentration−diffusion and the electro-osmotic drag of water caused by the hydration shield of protons. The model is used to analyze the transient behavior of a fuel cell and the dynamics of water inside the membrane as a consequence of changes in the load, voltage, or power released by the cell. The current−voltage transient responses are analyzed and explained in terms of the hydration of the membrane and the heterogeneity of water distribution over the membrane. Temporary changes in the power released by the cell operated at constant load are associated with wetting−drying processes. Wetting curves show an induction stage because initially the membrane is critically dehydrated. The estimations from the model suggest that local water contents lower than 2.4 mol of water per 1 mol of the sulfonic group act as a bottleneck for proton transport. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie070740h [article] Analysis of water transmembrane profiles and ionic transport during proton exchange membrane fuel cell transient behavior [texte imprimé] / Javier Parrondo, Auteur ; Arantxa Barrio, Auteur ; Jose Lombraña, Auteur ; Federico Mijangos, Auteur . - 2008 . - p. 4481–4489. Bibliogr. p. 4488-4489 Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 47 N° 13 (Juillet 2008) . - p. 4481–4489 Mots-clés : Transmembrane  water  profiles;  Current−voltage  curves;  Electrochemical  reaction Résumé : A one-dimensional isothermal model is used to calculate transmembrane water profiles and current−voltage curves under different operating conditions. The mechanistic model solves the mass balance over the system, basically by considering the main source-sink terms and transport contributions: fuel and air humidity, water generated by the electrochemical reaction; water concentration−diffusion and the electro-osmotic drag of water caused by the hydration shield of protons. The model is used to analyze the transient behavior of a fuel cell and the dynamics of water inside the membrane as a consequence of changes in the load, voltage, or power released by the cell. The current−voltage transient responses are analyzed and explained in terms of the hydration of the membrane and the heterogeneity of water distribution over the membrane. Temporary changes in the power released by the cell operated at constant load are associated with wetting−drying processes. Wetting curves show an induction stage because initially the membrane is critically dehydrated. The estimations from the model suggest that local water contents lower than 2.4 mol of water per 1 mol of the sulfonic group act as a bottleneck for proton transport. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie070740h

Simulation of internal concentration profiles in a multimetallic ion exchange process / Nikolay Tikhonov in Industrial & engineering chemistry research, Vol. 47 N° 23 (Décembre 2008) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 47 N° 23 (Décembre 2008) . - p. 9297–9303 Titre : Simulation of internal concentration profiles in a multimetallic ion exchange process Type de document : texte imprimé Auteurs : Nikolay Tikhonov, Auteur ; Federico Mijangos, Auteur ; Andreei Dautov, Auteur Année de publication : 2009 Article en page(s) : p. 9297–9303 Note générale : Chemistry engineering Langues : Anglais (eng) Mots-clés : Simulation  of  internal  Ion  exchange  process Résumé : The kinetics of heavy metal uptake—copper and cobalt against sodium—by chelating resins was analyzed experimentally by measuring the internal concentration profiles inside a single bead. Metal concentration profiles inside the particles at different reaction times were measured using an energy dispersive X-ray (SEM-EDX) coupled to a scanning electron microscope. This technique provided a line scan along diametrical positions, yielding the metal concentration profiles needed in order to build mathematical models for the simultaneous uptake of copper and cobalt. This process is described by means of a mathematical model which uses the Nernst−Planck equation for diffusion and takes into account relevant physical and chemical effects. The diffusion model proposed here takes into account the mobility of ions through the macroporous ion exchanger and the corresponding electric field generated by the diffusion of ions with dissimilar diffusivities. The estimated diffusion coefficients are discussed in terms of the mobility of a single metal and the contribution of its co-ion. The dynamic behavior of a system composed of two intraparticular phases is correctly described by this diffusion model, including the nonmonotonous tendencies which are not associated with the different values of the diffusion coefficient. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie800648v#afn1 [article] Simulation of internal concentration profiles in a multimetallic ion exchange process [texte imprimé] / Nikolay Tikhonov, Auteur ; Federico Mijangos, Auteur ; Andreei Dautov, Auteur . - 2009 . - p. 9297–9303. Chemistry engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 47 N° 23 (Décembre 2008) . - p. 9297–9303 Mots-clés : Simulation  of  internal  Ion  exchange  process Résumé : The kinetics of heavy metal uptake—copper and cobalt against sodium—by chelating resins was analyzed experimentally by measuring the internal concentration profiles inside a single bead. Metal concentration profiles inside the particles at different reaction times were measured using an energy dispersive X-ray (SEM-EDX) coupled to a scanning electron microscope. This technique provided a line scan along diametrical positions, yielding the metal concentration profiles needed in order to build mathematical models for the simultaneous uptake of copper and cobalt. This process is described by means of a mathematical model which uses the Nernst−Planck equation for diffusion and takes into account relevant physical and chemical effects. The diffusion model proposed here takes into account the mobility of ions through the macroporous ion exchanger and the corresponding electric field generated by the diffusion of ions with dissimilar diffusivities. The estimated diffusion coefficients are discussed in terms of the mobility of a single metal and the contribution of its co-ion. The dynamic behavior of a system composed of two intraparticular phases is correctly described by this diffusion model, including the nonmonotonous tendencies which are not associated with the different values of the diffusion coefficient. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie800648v#afn1