3,253 research outputs found
Specifications for a coupled neutronics thermal-hydraulics SFR test case
No full textCoupling neutronics/thermal-hydraulics calculations for the design of nuclear reactors is a growing trend in the scientific community. This approach allows to properly represent the mutual feedbacks between the neutronic distribution and the thermal-hydraulics properties of the materials composing the reactor, details which are often lost when separate analysis are performed. In this work, a test case for a generation IV sodium-cooled fast reactor (SFR), based on the ASTRID concept developed by CEA, is proposed. Two sub-assemblies (SA) characterized by different fuel enrichment and layout are considered. Specifications for the test case are provided including geometrical data, material compositions, thermo-physical properties and coupling scheme details. Serpent and ANSYS-CFX are used as reference in the description of suitable inputs for the performing of the benchmark, but the use of other code combinations for the purpose of validation of the results is encouraged. The expected outcome of the test case are the axial distribution of volumetric power generation term (q'''), density and temperature for the fuel, the cladding and the coolant
Magnetic induction and electric potential solvers for incompressible MHD flows
No full textThis work describes the theoretical background and the implementation of OpenFOAM solvers suitable for the simulation of incompressible magneto-hydrodynamic (MHD) flows. This class is a topic of interest for many research activities and industrial applications including nuclear fusion reactors, materials engineering and metallurgy. The main purpose of this document is to help the reader to get accustomed with the relevant phenomena and peculiar challenges of this kind of problems. In order to accomplish this goal it will focus the attention on the 2D MHD flows that arise in a rectangular duct with walls of arbitrary electrical conductivity when an electric conductive fluid moves in the presence of a transverse magnetic field
Influence of PbLi hydraulic path and integration layout on MHD pressure losses
No full textA critical point in the design of liquid metal blankets for fusion reactors is the accurate estimate of magnetohydrodynamic (MHD) pressure losses caused by the interaction between flowing breeder and magnetic field. In the Water-Cooled Lithium Lead (WCLL), the liquid metal (PbLi) is used as tritium breeder and carrier, whereas power extraction is delegated to water, thus allowing to minimize the breeder velocity. However, pressure drop for the PbLi loop is expected to remain significant due to high field intensity and direct electrical contact at fluid/wall interface. In this study, a comparative analysis between four alternative WCLL-DEMO configurations is performed to investigate the influence of blanket layout and piping system integration on this variable. Empirical and semi-empirical correlations, supported by numerical simulation results, have been used to estimate the baseline MHD loss, thus neglecting secondary contributions from viscous, inertial, and coupling effects. The larger contribution has been observed in the connection pipes, which are characterized by extensive length, high velocity, and large field gradients. Integration scheme with DEMO reactor is also a key factor, whereas breeding zone and manifold layout play secondary, albeit significant, roles in determining overall MHD loss. Adopting insulating elements in feeding and draining pipes should be carefully considered to reduce PbLi pumping requirements. Further numerical and experimental characterization of 3D MHD flow in manifolds and for coupling phenomena is vigorously suggested to reduce the uncertainty about blanket flow distribution and pressure loss estimate
A imagem de Alessandro Baricco no Brasil
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Comunicação e Expressão, Programa de Pós-Graduação em Estudos da Tradução, Florianópolis, 2013.Com a intenção de delinear o modo pelo qual o escritor italiano Alessandro Baricco se inseriu no sistema literário brasileiro e os caminhos percorridos pelos seus livros traduzidos, esta dissertação dá voz às experiências tradutórias de seus tradutores. A inserção de Bariccono Brasil tem seu início em 1997, através de uma proposição da Profa. Dra. Roberta Barni à editora Iluminuras da tradução de Oceano Mare. A partir daí, outras sete obras foram publicadas no Brasil, sendo três delas traduzidas por Roberta Barni e as outras quatro por quatro tradutores diferentes. De um lado, considera-se o tradutor como figura principal namediação entre culturas, e, de outro, se analisa a realidade desta figuradentro do sistema literário, sua invisibilidade, seus limites e o exercíciode sua profissão. A pesquisa conta, ainda, com críticas e resenhas referentes ao autor italiano publicadas em jornais consagrados no Brasil, considerando estas como parte constituinte da imagem de Baricco refletida em território nacional. Abstract : Intending to delineate the way the Italian writer Alessandro Baricco has been inserted in the Brazilian literary system and the paths his translated books have followed, this thesis gives voice to the translating experiences of his translators. Baricco's insertion in Brazil began in 1997, through a personal project of Dr. Roberta Barni, with her translation of Oceano Mare. Since then, seven other of his works have been published in Brazil, three of which were translated by Roberta Barni and the other four by four different translators. On the one hand,the translator is considered as the main figure in mediation betweencultures and, on the other, this figure's reality is analyzed within theliterary system: its invisibility, its limits and its professional practice. Criticisms and reviews of this Italian author published in well established Brazilian newspapers are also considered, with the understanding that they are part of Baricco's image reflected here
CFD simulation of the magnetohydrodynamic flow inside the WCLL breeding blanket module
No full textThe interaction between the molten metal and the plasma-containing magnetic field in the breeding blanket causes the onset of a magnetohydrodynamic (MHD) flow. To properly design the blanket, it is important to quantify how and how much the flow features are modified compared with an ordinary hydrodynamic flow. This paper aims to characterize the evolution of the fluid inside one of the proposed concepts for DEMO, the Water-Cooled Lithium Lead (WCLL), focusing on the central cell of the equatorial outboard module. A preliminary validation was required to gauge the capability of ANSYS CFX to deal with MHD problems. The buoyant and pressure-driven fully developed laminar flows in a square duct were selected as benchmarks. Numerical results were compared with theoretical solutions and an excellent agreement was found. The channel analysis was realized on a simplified version of the latest available design geometry, developed by ENEA, for M ≤1000. The simulation highlighted the formation of high velocity jets close to the baffle and the onset of an asymmetrical potential distribution
Three-dimensional MHD flow in moderate change ratio orifice
No full textIn fusion reactor blanket design, liquid metals are attractive working fluids since it is possible to combine in a single fluid the functions of coolant, tritium carrier and breeder. These electrically conductive fluids flow in the presence of a strong magnetic field, inducing the appearance of Lorentz forces and magnetohydrodynamic MHD effects. Increased pressure loss, particularly in complex geometry elements, is a critical point for blanket design. The MHD flow through an orifice plate made by electroconductive walls (c = 0.01 ÷ 0.1) has been analysed in this paper using ANSYS CFX in the range Re = 108, and Ha = 0 ÷ 300. A wide recirculation region is detected after the flow exits the orifice, with potentially harmful consequences for efficient tritium removal. Large pressure loss occurs in the orifice due to conductive wall and non-negligible axial length. The 3D pressure drop term is characterized through a local resistance coefficient (k) that is found to be k ≈ 0.205 for well conducting walls (c = 0.1) and k ≈ 0.063 for poorly conducting ones (c = 0.01)
Numerical simulation of thin-film MHD flow for nonuniform conductivity walls
No full textLiquid metals offer unique properties and their use in a nuclear fusion reactor, both as confined flows and free surface flow, is widely studied in the fusion community. The interaction between this conductive fluid and the tokamak magnetic fields leads to Magnetohydrodynamic (MHD) phenomena that influence the flow features. To properly design components that employ liquid metals, it is necessary to accurately predict these features and, although the efforts made in development, a mature code specifically customized to simulate MHD flows is still unavailable. In this work, the general purpose computational fluid dynamics code ANSYS CFX 18.2 is validated for MHD free surface thin film flow with insulated walls, up to Ha=1000 and for several values of the characteristic width/thickness ratio, comparing the results with the theoretical relation available in the literature. For all the cases considered, the maximum integral error is found below 10 %. Successively, the validated code is used to investigate the MHD flow in a chute with a characteristic film ratio equal to 0.1 and for Ha=300. Uniform and non-uniform wall electrical conductivity cases are considered with the latter modeled by placing on the side walls and on the back wall localized regions with different conductivity. The electrical conductivity of the back wall is found to have a negligible effect on the global flow when the lateral wall in insulated, similarly to what is observed for the analogous bounded flow. Contrariwise, an electrically conductive lateral wall is found to enhance the free surface jet and to modify the Hartmann layer structure
Numerical characterization of liquid metal MHD flow in electroconductive thick orifices with asymmetric contraction
No full textIn this paper, the 3D MHD flow through an orifice with asymmetric contraction is investigated. This hydraulic element is commonly found in fusion reactor liquid blanket designs, e.g. connecting the manifold and breeding zone region. This component is characterized about flow features and pressure losses using the CFD code ANSYS CFX for the case of electroconductive walls in the range c=0.01÷0.1, Re=108, and Ha=0÷300. The sudden variation of cross section in the orifice causes the induction of electric currents in the streamwise direction that contribute to determine the overall MHD pressure drop. A wide recirculation region is observed in the duct center after the flow egress from the orifice, which could be potentially harmful for efficient tritium transport outside of the blanket. Large pressure loss occurs in the orifice due to the enhanced wall conductivity and non-negligible axial length. The 3D pressure drop term is characterized through a local resistance coefficient (k) that is found to be k≈0.205 for well conducting walls (c=0.1) and k≈0.063 for poorly conducting ones (c=0.01)
MHD mixed convection around curved pipes in water-cooled breeding blankets
No full textThe magneto-convection regime established in a variant of the Water-Cooled Lead- Lithium blanket is analysed through numerical simulations with Ansys CFX code. This variant foreseen a poloidal-upward flow of the breeder, where the cooling is carried out by nested double-walled tube U-pipes inserted horizontally from the back plate. Fusion-relevant magnetic field intensity and volumetric power source are considered in the study, which combination produces a weak inertial magneto-convection flow regime. The simulations are performed considering the equatorial, the apical and the near-divertor elementary cell. The flow regime is slightly altered by different gravity orientations, confirming in all the case the suppression of advection in favour of conduction as dominant heat transfer mechanism
Electromagnetic coupling phenomena in co-axial rectangular channels
No full textIn the Water-Cooled Lithium Lead (WCLL) blanket, the eutectic alloy lithium-lead (PbLi) is used as tritium breeder and carrier, neutron multiplier and heat transfer medium. The liquid metal is distributed to and collected from the breeding zone through a compact poloidal manifold composed of two co-axial rectangular channels. The external channel, tasked with distribution, and the internal one, assigned to the collection, are co-flowing and share an electrically conductive wall (c_w=0.1). The liquid metal, interacting with the reactor magnetic field, leads to the arising of MagnetoHydroDynamic (MHD) effects that are expected to significantly modify the flow feature and electrically couple the external and internal channels. In this work, the general-purpose CFD code Ansys CFX 18.2 is used to study the coupling phenomena in a wide range of magnetic fields (up to Ha=2000) for a prototypical square co-axial channel. Characteristic flow features and their evolution with increasing magnetic field and varying mass flow rate between the channels are discussed and compared with the uncoupled case, which is in turn composed by a rectangular electro-conductive annulus (external) and a square electro-conductive duct (internal). A correlation is found linking the pressure loss in the studied configuration and an equivalent square channel through a corrective factor , which exhibits an asymptotic behavior for Ha > 1000
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