I023 Modulation de la dysfonction endothelium dependente par la maladie artérielle liée aux pathologies associées chez l’hémodialysé

ObjectifsLa fonction endothéliale (vasodilatation flux dépendante, FMD) est réduite chez l’hémodialysé. Nous avons étudié le rôle des atteintes artérielles reflétant les pathologies cardiovasculaires associées, dans l’altération de la FMD en fonction de la contrainte de cisaillement mesurée localement.MéthodologieChez 35 patients avec insuffisance rénale dialysés (ESRD), 16 avec un antécédent de maladie cardio-vasculaire (CV+), 19 indemnes (CV-) et chez 22 contrôles appariés, nous avons évalué la géométrie de l’artère humérale (diamètre : D et épaisseur : IMT, Wall Track System) et ses changements (FMD) en réponse aux modifications du taux de cisaillement et de la contrainte de cisaillement (SS), calculée avec mesure de viscosité sanguine (viscosimètre Brookfield), pendant une hyperhémie induite par chauffage de la main dans un bain thermostaté (paliers de 35 à 44°C). Les comparaisons multiples ont été faites par ANOVA et analyses post Hoc par test de Bonferonni.RésultatsESRD CV+ étaient plus agés avec pressions systolique et pulsée, D, IMT et module élastique plus élevés alors que SS étaient significativement réduit en baseline versus les deux autres groupes. Avec chauffage, les ESRD CV- et contrôles avaient une augmentation similaire de la pente D vs SS pour les températures faibles mais la pente devenait significativement plus faible pour ESRD à 44°. Les ESRD CV+ ont présenté une altération de la relation D vs SS pour toute la gamme de température. La réponse à la TNT était réduite pour ESRD CV+ versus les deux autres groupes.ConclusionLes altérations artérielles des ESRD avec pathologies cardio-vasculaires associées sont structurales, mais également fonctionnelles. Par contre en absence de maladie vasculaire les ESRD ont un comportement non différent des contrôles pour des stimulations non maximales mais ont une réduction de la réserve de dilatation altérée lors de stimulations soutenues et maximales

Engineering safety in hydrogen-energy applications

International audienceSince a few years, hydrogen appears as a practical energy vector and some hydrogen applications are already on the market. However these applications are still considered dangerous, hazardous events like explosion could occur and some accidents, like the Hindenburg disaster, are still in the mind. Objectively, hydrogen ignites easily and explodes violently. Safety engineering has to be particularly strong and demonstrative; a method of precise identification of accidental scenarios (“probabilities”; “severity”) is developed in this article. This method, derived from ARAMIS method, permits to identify and to estimate the most relevant safety barriers and therefore helps future users choose appropriate safety strategies

Development of a model evaluation protocol for CFD analysis of hydrogen safety issues the SUSANA project

The “SUpport to SAfety aNAlysis of Hydrogen and Fuel Cell Technologies (SUSANA)” project aims to support stakeholders using Computational Fluid Dynamics (CFD) for safety engineering design and assessment of FCH systems and infrastructure through the development of a model evaluation protocol. The protocol covers all aspects of safety assessment modelling using CFD, from release, through dispersion to combustion (self-ignition, fires, deflagrations, detonations, and Deflagration to Detonation Transition - DDT) and not only aims to enable users to evaluate models but to inform them of the state of the art and best practices in numerical modelling. The paper gives an overview of the SUSANA project, including the main stages of the model evaluation protocol and some results from the on-going benchmarking activities.JRC.C.1-Energy Storag

An inter-comparison exercise on the capabilities of CFD models to predict the short and long term distribution and mixing of hydrogen in a garage

The paper presents the results of the CFD inter-comparison exercise SBEP-V3, performed within the activity InsHyde, internal project of the HySafe network of excellence, in the framework of evaluating the capability of various CFD tools and modelling approaches in predicting the short and long term mixing and distribution of hydrogen releases in confined spaces. The experiment simulated was INERIS-TEST-6C, performed within the InsHyde project by INERIS, consisting of a 1 g/s vertical hydrogen release for 240s from an orifice of 20 mm diameter into a rectangular room (garage) of dimensions 3.78 x 7.2 x 2.88 In in width, length and height respectively. Two small openings at the bottom of the front side of the room assured constant pressure conditions. During the test hydrogen concentration time histories were measured at 12 positions in the room, for a period up to 5160 s after the end of release, covering both the release and the subsequent diffusion phases. The benchmark was organized in two phases. The first phase consisted of blind simulations per-formed prior to the execution of the tests. The second phase consisted of post-calculations performed after the tests were concluded and the experimental results made available. The participation in the benchmark was high: 12 different organizations (2 non-HySafe partners), 10 different CFD codes and 8 different turbulence models. Large variation in predicted results was found in the first phase of the benchmark, between the various modelling approaches. This was attributed mainly to differences in turbulence models and numerical accuracy options (time/space resolution and discretization schemes). During the second phase of the benchmark the variation between predicted results was reduced. (C) 2009 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved

An inter-comparison exercise on the capabilities of CFD models to predict the short and long term distribution and mixing of hydrogen in a garage

International audienceThe paper presents the results of the CFD inter-comparison exercise SBEP-V3, performed within the activity InsHyde, internal project of the HYSAFE network of excellence, in the framework of evaluating the capability of various CFD tools and modeling approaches in predicting the physical phenomena associated to the short and long term mixing and distribution of hydrogen releases in confined spaces. The experiment simulated was INERIS-TEST-6C, performed within the InsHyde project by INERIS, consisting of a 1 g/s vertical hydrogen release for 240 s from an orifice of 20 mm diameter into a rectangu ar room (garage) of dimensions 3.78x7.2x2.88 m in width, length and height respectively. Two small openings at the front and bottom side of the room assured constant pressure conditions. During the test hydrogen concentration time histories were measured at 12 positions in the room, for a period up to 5160 s after the end of release, covering both the release and the subsequent diffusion phases. The benchmark was organized in two phases. The first phase consisted of blind simulations performed prior to the execution of the tests. The second phase consisted of post-calculations performed after the tests were concluded and the experimental results made available. The participation in the benchmark was high: 12 different organizations (2 non-HYSAFE partners) 10 different CFD codes and 8 different turbulence models. Large variation in predicted results was found in the first phase of the benchmark, between the various modeling approaches. This was attributed mainly to differences in turbulence models and numerical accuracy options (time/space resolution and discretization schemes). During the second phase of the benchmark the variation between predicted results was reduced