64 research outputs found

    Development of a simulation tool for MHD flows under nuclear fusion conditions

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    In Nuclear Fusion Technology, MHD flows can be encountered in liquid metal (LM) breeding blankets, the part of a fusion reactor where tritium, one of the fusion fuels, is to be produced. There are several types of LM breeding blankets, which can be classified according to the fraction of the thermal load extracted by the LM. Such classification provides valuable information on liquid metal flow properties. For instance, if no heat removal is carried out by the LM, its velocity can be quite low, what makes buoyancy the predominant force in front of inertia. The flow inside breeding blanket channels can be very complex, particularly in those blanket types where buoyancy plays a relevant role. The understanding of the flow nature, including the possible instabilities that might appear, the exact knowledge of flow profiles for tritium control purposes, and the prediction of thermal fluxes for thermal efficiency analysis are of great interest for blanket design optimization. In this direction, a thermal-MHD coupled simulation tool has been implemented in the OpenFOAM toolkit. The resultant code can be understood as a preliminary predictive tool for liquid metal breeding blanket channel design. The developed code is a transient 3D tool that accounts for thermal-MHD coupling and can deal with several layers of materials. Various MHD modeling strategies have been studied, starting with the implementation of an induced magnetic field formulation and continuing with an electric potential formulation based on the low magnetic Reynolds approximation, in this case using the conservative formula of the Lorentz force proposed by Ni et al. (2007). Two pressure-velocity couplings have been analyzed. The first one is based on a projection method whereas the second one, which has proved to be more robust, follows a PISO-like algorithm (Weller et al. 1998). The thermal coupling has been achieved by means of the Boussinesq hypothesis. The developed tool accounts for the linear wall function for Hartmann boundary layers from Leboucher (1999), which reduces substantially the CPU time of the simulations. The code also accounts for fluid-solid thermal and electrical coupling by means of implicit coupling of fluid and solid grids. Special attention has been placed in correctly coupling liquid-solid energy transport equations by means of the conservative form of the equations in both domains. All along the development process, validation steps have been carried out with successful results. An alternative thermal-MHD tool has also been implemented following the 2D approach from Sommeria and Moreau (1982). Such code accounts for the 0-equation Q2D turbulence RANS model from Smolentsev and Moreau (2006). Three application cases are considered. In the first case, the integrated effect of volumetric heating and magnetic field on tritium transport in a U-bend flow, as applied to the EU HCLL blanket concept, is studied. The second application case corresponds to the thermal analysis of the blanket design that is being developed in the framework of the Spanish National Project on Breeding Blanket Technologies TECNO_FUS (through CONSOLIDER-INGENIO 2010 Programme). The third and last case includes the instability analysis of a pressure-driven MHD flow in a horizontal channel with a constant thermal load. The application cases have not only shown the code capabilities to simulate liquid metal channels in breeding blankets but, also, have provided a useful know-how on flow properties inside those channels.En Tecnologia de Fusió Nuclear, per descriure la circulació de fluids dins dels embolcalls regeneradors de metall líquid (ML) cal recórrer a la magnetohidrodinàmica (MHD). Un embolcall regenerador (o tritigeni) és la zona d'un reactor de fusió on es produeix triti, un dels combustibles de fusió. Els embolcalls regeneradors de ML poden classificar-se atenent a la fracció de la càrrega tèrmica extreta pel ML. Aquesta classificació proporciona informació valuosa sobre les propietats del flux de metall líquid. Per exemple, si el ML no extreu potència tèrmica, la seva velocitat pot ser bastant baixa, el que implica que la força dominant sigui la flotació en front de la inèrcia. El flux dins dels canals d’un embolcall regenerador pot ser molt complex, especialment en aquells tipus d’embolcall on la flotació juga un paper rellevant. La comprensió de la naturalesa del flux, incloent les inestabilitats que podrien aparèixer, el coneixement exacte dels perfils de flux per al control de triti, i la predicció de fluxos tèrmics per a l’anàlisi de l’eficiència tèrmica són de gran interès per a l’optimització del disseny. En aquest sentit, s’ha implementat un codi de simulació acoblada tèrmica-MHD en l’eina de codi lliure OpenFOAM. El codi resultant pot ser entès com una eina predictiva preliminar per al disseny dels canals de ML dels embolcalls regeneradors. El codi desenvolupat permet el càlcul transitori en 3D amb acoblament tèrmic-MHD i pot tractar amb diverses capes de materials. S’ha estudiat diferents models MHD, començant per la implementació d’una formulació basada en el camp magnètic induït i continuant amb una formulació basada en el potencial elèctric mitjançant l’aproximació per a Reynolds magnètics baixos, en aquest darrer cas utilitzant la fórmula conservativa de la força de Lorentz proposada per Ni et al. (2007). S’han analitzat dos acoblaments pressió-velocitat. El primer acoblament es basa en un mètode de projecció, mentre que el segon, que ha demostrat ser més robust, segueix un algorisme tipus PISO (Weller et al. 1998). L’acoblament tèrmic s'ha modelat per mitjà de la hipòtesi de Boussinesq. El codi desenvolupat compta amb la funció de paret lineal de Leboucher (1999) per a les capes límit de Hartmann, cosa que redueix substancialment el temps de CPU de les simulacions. El codi també inclou acoblament tèrmic i magnètic líquid-sòlid mitjançant l'acoblament implícit de les malles del fluid i del sòlid. S’ha tingut una cura especial en realitzar correctament aquest acoblament fluid-sòlid fent ús de la forma conservativa de l’equació d’energia en ambdós dominis. Al llarg del procés de desenvolupament, s’han dut a terme les corresponents validacions amb resultats satisfactoris. També s'ha implementat un codi tèrmic-MHD alternatiu basat en el model MHD 2D de Sommeria i Moreau (1982). Aquest segon codi té implementat el model RANS de 0-equacions de Smolentsev i Moreau (2006) per a la turbulència Q2D. Els codis desenvolupats s’han emprat en tres casos d’interès. En el primer cas, s’ha estudiat l’efecte integrat de l’escalfament volumètric i el camp magnètic en el transport de triti en un canal en U, com el que es pot trobar en el disseny d’embolcall regenerador UE HCLL. En el segon cas, s’ha realitzat una anàlisi tèrmica del disseny d’embolcall que s’està definint dins del Programa Nacional Espanyol en Tecnologia d’Embolcalls Regeneradors TECNO_FUS (a través del Programa CONSOLIDER-INGENIO 2010). En el tercer i últim cas, s’han analitzat les inestabilitats que tenen lloc en fluxos MHD en canals horitzontals amb gradient de pressió extern, amb camp magnètic transversal i amb una càrrega tèrmica uniforme. Els casos d’aplicació no només han demostrat la capacitat del codi per simular canals de metall líquid en embolcalls regeneradors; també han permès caracteritzar el flux a l’interior d’aquests canals.Postprint (published version

    Flow analysis in the HCLL-TBM ITER channels including MHD and heat transfer

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    One of the key components regarding heat transfer and tritium inventories in deuterium-tritium nuclear fusion reactors is the (tritium) Breeding Blanket, called Test Blanket Module or TBM in ITER experiment. Several designs are going to be tested in ITER, one of those is the HCLL (Helium Cooled Lithium Lead) design. Before being tested, it is of major interest to predict in detail several ow parameters such as pressure drop, tritium inventories and tritium permeation rates through walls. The goal of the present study is to analyze the ow near the gap region (close to the rst wall) in the HCLL-TBM so as to quantify tritium inventories and permeation uxes. To do so, simpli ed C-shaped channels are simulated under ITER speci cations. The ow appears to be very complex and, in order to get the origin of this complexity, the phe- nomenon physics are decoupled. First, the pure hydrodynamic case is simulated; obtaining that the critical Reynolds number is around TBM/ITER speci cations. Second, the MHD ow with perfectly insulating walls is studied and, as expected due to the high Hartmann number, hydrodynamic instabilities disappear. Finally, when heat transfer is introduced, vorticity is generated due to Rayleigh-B enard instabilities at the channel inlet and, as the ow travels through the channel, faster vortices appear in the gap region and in the outlet channel. These vortices originate high tritium concentration zones. Hence, the existence of vortices is of crucial interest for tritium inventories prediction and HCLL design.Postprint (published version

    Enginyeria Industrial: guies per a una docència universitària amb perspectiva de gènere

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    L'Enginyeria Industrial forma part de les STEM, àmbit de coneixement molt masculinitzat on existeixen poques investigacions i manuals que aborden les problemàtiques específiques en clau de gènere. La Guia per a una docència universitària amb perspectiva de gènere d'Enginyeria Industrial ofereix propostes, exemples de bones pràctiques, recursos docents i eines de consulta que permeten desmasculinitzar aquest àmbit i visibilitzar els models femenins per potenciar l’accés de les dones als estudis de grau.Aquest projecte ha rebut finançament del Departament d’Empresa i Coneixement de la Generalitat de Catalunya.Mas De Les Valls Ortiz, E.; Peña Carrera, M. (2020). Enginyeria Industrial: guies per a una docència universitària amb perspectiva de gènere. Xarxa Vives d'Universitats. http://hdl.handle.net/10251/15073

    An approach to verification and validation of MHD codes for fusion applications

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    We propose a new activity on verification and validation (V&V) of MHD codes presently employed by the fusion community as a predictive capability tool for liquid metal cooling applications, such as liquid metal blankets. The important steps in the development of MHD codes starting from the 1970s are outlined first and then basic MHD codes, which are currently in use by designers of liquid breeder blankets, are reviewed. A benchmark database of five problems has been proposed to cover a wide range of MHD flows from laminar fully developed to turbulent flows, which are of interest for fusion applications: (A) 2D fully developed laminar steady MHD flow, (B) 3D laminar, steady developing MHD flow in a non-uniform magnetic field, (C) quasi-two-dimensional MHD turbulent flow, (D) 3D turbulent MHD flow, and (E) MHD flow with heat transfer (buoyant convection). Finally, we introduce important details of the proposed activities, such as basic V&V rules and schedule. The main goal of the present paper is to help in establishing an efficient V&V framework and to initiate benchmarking among interested parties. The comparison results computed by the codes against analytical solutions and trusted experimental and numerical data as well as code-to-code comparisons will be presented and analyzed in companion paper/papers.Peer ReviewedPostprint (author's final draft

    A Formal Verification and Validation of a Low Magnetic Reynolds Number MHD Code for Fusion Applications

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    © 2022 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other worksAs the nuclear fusion research advances, resear-chers and engineers focus more on the design of the required systems that complement the nuclear fusion reaction in the plasma of a Tokamak. Some proposals for breeding blankets as well as plasma-facing components’ protection systems are based in liquid metal flows under the Tokamak intense magnetic fields. This creates the situation where induced magnetic field can be neglected and the low magnetic Reynolds number (Re) electric potential formulation can be used to close the magnetohydrodynamic (MHD) system of equations. In the last few years, many different laboratories have developed their own MHD codes to study the liquid metal flow. A formal verification and validation of such codes is necessary to enhance the reliability of the numerical results and to make sure that design decisions are based on safe grounds. The fusion community has made the effort of proposing standardized benchmark cases through which any MHD code should demonstrate its reliability. This work contains the formal validation and verification activities of the MHD code developed some years ago in the Universitat Politecnica de Catalunya (UPC) and currently candidate to contribute to the research done at the Princeton Plasma Phyisics Laboratory (PPPL). The code is implemented over OpenFOAM which makes it easily modifiable. Among these benchmark cases, there are high Hartmann number (Ha), 3-D flows, and magneto-convective interaction cases.Peer ReviewedObjectius de Desenvolupament Sostenible::9 - Indústria, Innovació i InfraestructuraPostprint (published version

    Conceptual design of the EU-DEMO dual coolant lithium lead equatorial module

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    © 20xx IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.Within the framework of EUROfusion Program, the Dual Coolant Lithium Lead (DCLL) is one of the four EU breeder blanket concepts that are being investigated as candidates for DEMO. DCLL uses PbLi as the main coolant, tritium breeder, tritium carrier, and neutron multiplier. The main structures, including the first wall, are cooled with helium. The EU program proposed for the next years will consider a DCLL version limited to 550 °C in order to allow the use of conventional materials and technologies. During the first year of EUROfusion activities, a draft design of the DCLL has been proposed. The main blanket performances were adapted to the new specifications and the CAD model of DEMO. The breeder zone has been toroidally divided into four parallel PbLi circuits, separated through stiffening grid radial walls. The PbLi flow routing has been designed to maximize the amount of thermal power extracted by flowing PbLi and to avoid the occurrence of reverse flows due to volumetric heating. Thermal hydraulics, magnetohydrodynamic and neutronics calculations have been performed for the first draft design. The new DCLL design employs Eurofer-alumina-Eurofer sandwich as flow channel insert (FCI).Postprint (published version

    Perspectiva de género en docencia STEM

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    La Universitat Politècnica de Catalunya, dentro del III Plan de Igualdad de Género 2016-2020, está llevando a cabo diferentes acciones para promover la transversalidad de género en la universidad. El presente artículo expone el trabajo del proyecto Género y Docencia, cuyo objetivo principal es la capacitación del personal académico para la incorporación de la perspectiva de género en la docencia. Este proyecto cuenta con la participación voluntaria de 41 docentes de 8 titulaciones STEM. Su duración, que coincide con el cuatrimestre de primavera de 2019, ha permitido llevar a cabo las estrategias propuestas a lo largo del curso. Los aspectos que se han tenido en cuenta incluyen la relevancia social y de género de las asignaturas, la metodología inclusiva, la gestión del aula y la evaluación. Se ha tenido especial cuidado en la elaboración de indicadores para poder realizar la correcta evaluación del proyecto a su término. Se ha elaborado una herramienta de autoevaluación para el equipo docente y un cuestionario para analizar la sensibilización del alumnado, así como su percepción respecto a la falta de igualdad de género en el ámbito docente.Postprint (published version

    STEM students’ perception of gender mainstreaming in teaching: the development of a measuring tool

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    This study assesses the development process of a tool to measure students’ perceptions of gender mainstreaming in STEM (Science, Technology, Engineering and Mathematics) studies. Within the framework of a pilot project named Gender Dimension in Teaching implemented at the Universitat Politècnica de Catalunya · BarcelonaTech (UPC), a group of 35 teachers worked during one semester on how to introduce the gender perspective in their teaching. This aim is especially relevant when considering STEM studies, since they have traditionally been defined as gender-neutral when, in fact, they are gender-blind. The teachers that participate in the project cover a wide range of STEM studies, including Architecture, Civil Engineering, ICT Systems Engineering, Naval Systems and Technology Engineering, Aerospace Systems Engineering, Applied Telecommunications and Engineering Management, Industrial Engineering and Environmental Pathways for Sustainable Energy Systems. The project is part of the III Gender Equality Plan at the UPC and is supported by GEECCO project, which receives funding from the European Union's Horizon 2020 Research and Innovation programme. The Gender Dimension in Teaching project focuses on the four pillars of teaching (i.e. contents, classroom management, methodology and assessment), which were revised from a gender perspective. Within each pillar, gender issues were identified according to the experienced perception of the project participants. These gender issues included, for instance, gender differences in classroom participation, the stereotypical roles adopted in teamwork activities, the use of female references as models for students, the adoption of a gender-inclusive language by both teachers and students, the use of stereotypes in teaching materials, gender bias in assessment, etc. However, uncertainty aroused concerning the reliability of such a perception. Indeed, teachers’ perception might be influenced by stereotypes and prejudices that could alter the identification of gender issues. Hence, it became obvious that more reliable data concerning students’ perceptions was needed. To this end, a first set of questions was collaboratively defined and a first survey was developed using Google Forms. The survey was tested at the beginning of the semester in 8 different UPC degrees, both at Bachelor and Master level, obtaining more than 500 answers. Despite some interesting preliminary results, a detailed revision of the questionnaire was conducted in order to remove some acquiescence bias and formal errors, thus improving the quality of the survey for a more global study. The improvement process included discussions among the members of the Gender Dimension in Teaching project, and discussions with the Feminist Assembly of the Industrial Engineering School at the UPC. As a final step, this revised survey was tested and discussed with a small sample of students. As a result, an improved survey to assess student’s perceptions of gender mainstreaming in STEM studies has been collaboratively obtained, which may become an essential tool for further studies extended to all the university community.Peer ReviewedPostprint (published version
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