Couplage Flux-Expert / Fluent : application à la modélisation 3D d'un électrolyseur à production d'hydrogène

Les électrolyseurs à production d'hydrogène de type Westinghouse sont des dispositifs électrochimiques constitués d'un empilement de compartiments cathodiques et anodiques séparés par une membrane. Ils abritent un ensemble de phénomènes physiques couplés. Pour modéliser ces installations nous avons développé un couplage entre les logiciels Fluent® (volumes finis) et Flux-Expert® (éléments finis). Le premier est utilisé pour la résolution de la partie thermo-hydraulique du problème, le second pour la partie électrocinétique avec surtensions d'activation. Leur couplage met en œuvre un processus itératif dans lequel chacun calcule des grandeurs physiques et les transmet à l'autre. Ces interpolations de grandeurs d'un maillage sur l'autre nécessitent une localisation des points de calcul sur des régions volumiques ou surfaciques 3D. Une librairie de passation de messages simple et robuste permet aux deux codes de communiquer

EFFICACITE DE L'INFILTRATION DE ROPIVACAINE POUR LA PRISE DE GREFFON OSSEUX ILIAQUE SUR L'ANALGESIE POSTOPERATOIRE

RENNES1-BU Santé (352382103) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF

Numerical modeling for preliminary design of the hydrogen production electrolyzer in the Westinghouse hybrid cycle

International audienceThe Westinghouse sulfur process decomposes water into hydrogen and oxygen in several steps. This process requires a high-temperature thermal source, which could ideally be a fourth-generation nuclear reactor for recycling compounds. The process consists of producing hydrogen in a specific electrolyzer where protons are reduced at the cathode while an oxidation reaction, in which sulfur dioxide forms sulfuric acid, takes place in the anode compartment. This type of reaction enables mass hydrogen production at a very low cell voltage because the thermodynamic oxidation potential of SO2/H2SO4 is 0.17 V, compared with 1.23 V for the common electrolysis of water by H2O/O2 oxidation. This article describes the electrical/thermal coupling of an individual filter press electrolysis cell for the preliminary design of a future test pilot. Solving coupled equations describing heat transfer and electrokinetics in the presence of forced convective flow of a two-phase electrolyte allows charge and heat transfer to be predicted for different configurations

Hydrogen filter press electrolyser modelled by coupling Fluent^<b>®</b> and Flux Expert^<b>®</b> codes

International audienceMass production of hydrogen is a major issue for the coming decades particularly to decrease greenhouse gas production. The development of fourth-generation high-temperature nuclear reactors has led to renewed interest for hydrogen production. In France, the CEA is investigating new processes using nuclear reactors, such as the Westinghouse hybrid cycle. A recent study was devoted to electrical modeling of the hydrogen electrolyzer, which is the key unit of this process. In this electrochemical reactor, hydrogen is reduced at the cathode and SO2 is oxidized at the anode with the advantage of a very low voltage cell. This paper describes an improved model coupling the electrical and thermal phenomena with hydrodynamics in the electrolyzer, designed for a priori computational optimization of our future pilot cell. The hydrogen electrolyzer chosen here is a filter press design comprising a stack of identical cathode and anode compartments separated by a membrane. In a complex reactor of this type the main coupled physical phenomena involved are forced convection of the electrolyte flows, the plume of evolving hydrogen bubbles that modifies the local electrolyte conductivity, and all the irreversible processes that contribute to local overheating (Joule effect, overpotentials, etc.). The secondary current distribution was modeled with a commercial FEM code, Flux Expert®, which was customized with specific finite interfacial elements capable of describing the potential discontinuity associated with the electrochemical overpotential. Since the finite element method is not capable of properly describing the complex two-phase flows in the cathode compartment, the Fluent® CFD code was used for thermohydraulic computations. In this way each physical phenomenon was modeled using the best numerical method. The coupling implements an iterative process in which each code computes the physical data it has to transmit to the other one: the two-phase thermohydraulic problem is solved by Fluent® using the Flux-Expert® current density and heat sources; the secondary distribution and heat losses are solved by Flux-Expert® using the Fluent® temperature field and flow velocities. A set of dedicated library routines was developed for process initiation, message passing, and synchronization of the two codes. The first results obtained with the two coupled commercial codes give realistic distributions for the electrical current density, gas fraction, and velocity in the electrolyzer. This approach allows us to optimize the design of a future experimental device

Influence of particle properties on cake resistance and compressibility : a modelling study

International audienc

Influence of particle properties and working pressures on cake dewatering

International audienc

New filterability and compressibility test cell design for nuclear product

International audienc

Filtration Process Optimization: Rheological Behavior of a Filter Cake at Different Moisture Contents

International audienceTransferring a wet cake from a filter to a dryer or furnace could severely lower the productivity of a whole process when the wet cake exhibits high viscosity and a sticky paste behavior. Depending on their moisture content, three distinct regions of rheological behavior were identified. Among them, only the granular solid type had sufficient flowability during the transfer operation. It was possible to discriminate the flow behavior more quantitatively by determining two transition values of moisture content. Rheological measurements were carried out at a constant shear rate representative of that encountered in the mechanical transfer system used at plant scale. The use of vane geometry for the rheometer was necessary to ensure an accurate repeatability of the viscosity measurements

AIF deficiency compromises oxidative phosphorylation

Apoptosis-inducing factor (AIF) is a mitochondrial flavoprotein that, after apoptosis induction, translocates to the nucleus where it participates in apoptotic chromatinolysis. Here, we show that human or mouse cells lacking AIF as a result of homologous recombination or small interfering RNA exhibit high lactate production and enhanced dependency on glycolytic ATP generation, due to severe reduction of respiratory chain complex I activity. Although AIF itself is not a part of complex I, AIF-deficient cells exhibit a reduced content of complex I and of its components, pointing to a role of AIF in the biogenesis and/or maintenance of this polyprotein complex. Harlequin mice with reduced AIF expression due to a retroviral insertion into the AIF gene also manifest a reduced oxidative phosphorylation (OXPHOS) in the retina and in the brain, correlating with reduced expression of complex I subunits, retinal degeneration, and neuronal defects. Altogether, these data point to a role of AIF in OXPHOS and emphasize the dual role of AIF in life and death