An Open-Source Library for the Numerical Modeling of Mass-Transfer in Solid-Oxide Fuel Cells

The generation of direct current electricity using Solid Oxidize Fuel Cells (SOFCs) involves several interplaying transport phenomena. Their simulation is crucial for the design and optimization of reliable and competitive equipment, and for the eventual market deployment of this technology. An open-source library for the computational modeling of mass-transport phenomena in SOFCs is presented in this article. It includes several multicomponent mass-transport models (ie Fickian, Stefan-Maxwell and Dusty Gas Model), which can be applied both within porous media and in porosity-free domains, and several diffusivity models for gases. The library has been developed for its use with OpenFOAM(R), a widespread open-source code for fluid and continuum mechanics. The library can be used to model any fluid flow configuration involving multi-component transport phenomena and it is validated in this paper against the analytical solution of one-dimensional test cases. In addition, it is applied for the simulation of a real SOFC and further validated using experimental dat

EFFECT OF CHEMICAL NON-EQUILIBRIUM ON FLOW PARAMETERS IN THE INTERMEDIATE HYPERSONIC REGIME

The new solver hypersonicIithFoam has been developed in the OpenFOAM framework. OpenFOAM has rhoCentralFoam which is a density based N-S solver, is used as a base solver. Additional features are incorporated to model reacting flows, variable multi-species diffusion and thermodynamic proper- ties of high-temperature air. The solver is implemented to model the transport properties based on a kinetic theory for its widespread applicability. Viscosity and Thermal conductivity are obtained using the model based on Lennard-Jones potential, and Chapman-Enskog diffusivity model is used to compute binary dif- fusion coefficient. Multicomponent mixture properties are calcu- lated based on a mole fraction. All species are assumed to be in thermodynamic equilibrium, so the state of the gas is governed by single equilibrium temperature. The solver is tested with the available experimental data for Heat flux and coefficient of pres- sure Cp distribution over a surface of ELECTRE article. The hy- personic solver is shown significant improvement over a conven- tional compressible solver. Simulations are carried out for the flow over a sphere at different altitudes using both the conven- tional and the hypersonic solver for qualitative and quantitative comparisons. Post shock temperature and peak heat flux values are remarkably reduces due to the implementation of real gas ef- fects and air chemistry. Rarefaction effects become significant from 70 km

Comparison of Humidified Hydrogen and Partly Pre-Reformed Natural Gas as Fuel for Solid Oxide Fuel Cells applying Computational Fluid Dynamics

A three-dimensional computational fluid dynamics (CFD) approach based on the finite element method (FEM) is used to investigate a solid oxide fuel cell (SOFC). Governing equations for heat, gas-phase species, electron, ion and momentum transport are implemented and coupled to kinetics describing electrochemical as well as internal reforming reactions. The model cell design is based on a cell from Ningbo Institute of Material Technology and Engineering in China and the electrochemical area-to-volume ratios are based on experimental work performed at Kyushu University in Japan. A parameter study is performed focusing on the inlet fuel composition, where humidified hydrogen, 30 % pre-reformed natural gas (as defined by IEA) and 50 % pre-reformed natural gas (as defined by Kyushu University) are compared. It is found that when 30 % pre-reformed natural gas is supplied as fuel the air mass flow rate is halved, compared to the case with humidified hydrogen, keeping the inlet and outlet temperatures constant. The current density is decreased but the fuel utilization is kept at 80 %. It is found that the cathode support layer has a significant oxygen gas-phase resistance in the direction normal to the cathode/electrolyte interface (at positions under the interconnect ribs), as well as an electron resistance inside the cathode (at positions under the air channel) in the same direction. The methane steam reforming reaction is shown, both according to the experiments and to the models, to proceed along the main flow direction throughout the cell

Design and modelling an innovative SOEC stack

The present work is focused on the design of a solid oxide cell stack that mainly works in electrolysis mode. The framework of the activity is the energetic issue related to the renewable sources management and storage capabilities. The analysis starts observing the energetic issue from an alternative standpoint that emphasizes the ethical aspects and instills in the reader the secondary importance of the efficiency respect to the feasibility and the robustness of the devices. In order to predict the stack performance, a new numerical solver has been developed based on open source tool. This multi-physic solver can handle complete SOC stack both in fuel cell mode and in electrolysis mode. As a part of this activity an insight concerning SOC Electrochemical Impedance Spectroscopy physical simulation has been done. This part of the solver can be coupled with additional plugins and provides the basis for the impedance analysis of the low frequency part of the SOC spectrum. Basing on pragmatic approach a new stack design was proposed and technical drawings have been released. The stack is based on tubular cells considering some peculiarity of the planar configuration especially concerning charge transfer between electrodes and external current takes. Some simulations have been run in order to validate the main assumptions of the design process

DESIGN & DEVELOPMENT OF PLANAR SOLID OXIDE FUEL CELL STACK

In the present work, planar anode-supported Solid Oxide Fuel Cell short-stacks have been designed, assembled, tested and characterized. The design of the stacks and its components (frame, housing, interconnect, compressive and bonded seals) required a great attention to the materials properties (i.e. thermal expansion coefficient compatibility, durability, strength and oxidation resistance, conductivity and so on), as well as to the fluid-dynamic analysis focused on flow field and gas distribution. Then, a careful analysis was done based on a multidisciplinary approach to select the stack components materials, geometries, and dimensions; in order to assure a high performing stack at elevated temperatures with cost reduction of materials, parts manufacturing and assembly procedure. The materials selected were: Crofer®22APU for the interconnect and the frame; AISI 316L for bolts and housing; Thermiculite® 866 for the compressive seal placed between the frame and the interconnect plate; Flexible Mica Paper for the compressive seal positioned between the interconnect endplate and the housing; SiO2-CaO-Al2O3-Na2O glass-ceramic sealant for the bonded seal to join the frame with the cell. On the other hand, the stack assembly was focused on the implementation of innovative and simple procedures, which allowed power capacity scale-up in accordance to power requirements. In this work, two different stack configurations were produced: with one cell (for initial testing of the materials and fluid-dynamic selected solutions) and with three cells. It must be mentioned that all developed stacks in this research were assembled with commercial cells "ASC3" from H.C. Starck. Also, calculations at ambient temperature and 800°C were done in the stack compression system to determine the proper tightening torque to be applied: this value was 50N. Although this calculation took into consideration the loss of tightening torque at high temperatures, some marks were found in housing and micas during the stack inspection after disassembly. These marks are a clear indicator of gas leakage. Additionally, a study was carried out related to the effect of the protective Mn1.5Co1.5O4 coating deposited on interconnect surface to prevent the cathode Cr poisoning. This experiment was executed in the stack of one cell configuration. No voltage degradation was observed during the galvanostatic experiment of 360 h at 800°

An open-source library for the numerical modeling of mass-transfer in solid oxide fuel cells

This program has been imported from the CPC Program Library held at Queen's University Belfast (1969-2018) Abstract The generation of direct current electricity using solid oxide fuel cells (SOFCs) involves several interplaying transport phenomena. Their simulation is crucial for the design and optimization of reliable and competitive equipment, and for the eventual market deployment of this technology. An open-source library for the computational modeling of mass-transport phenomena in SOFCs is presented in this article. It includes several multicomponent mass-transport models (i.e. Fickian, Stefan–Maxwel... Title of program: multiSpeciesTransportModels Catalogue Id: AEKB_v1_0 Nature of problem This software provides a library of models for the simulation of the steady state mass and momentum transport in a multispecies gas mixture, possibly in a porous medium. The software is particularly designed to be used as the mass-transport library for the modeling of solid oxide fuel cells (SOFC). When supplemented with other submodels, such as thermal and charge-transport ones, it allows the prediction of the cell polarization curve and hence the cell performance. Versions of this program held in the CPC repository in Mendeley Data AEKB_v1_0; multiSpeciesTransportModels; 10.1016/j.cpc.2011.08.00

Simulação fluidodinâmica da misturação de correntes líquidas aplicada à injeção de inibidores termodinâmicos de hidratos de gás

Natural gas hydrates are crystalline compounds formed by low molecular weight hydrocarbons and water in proper temperature and pressure conditions. In oil industry, one of the most likely scenarios of hydrate blockage appearance is the well shut in. When there is risk, a usual operational procedure is the replacement of flowline content by diesel or dead oil. However, there are scenarios where this procedure may not be the best option and the usage of thermodynamic hydrate inhibitor controlled injection may be the practicable solution. Therefore, this work aimed to understanding the mixing phenomenon between thermodynamic inhibitor and water through experimental data generation and modeling with subsequent algorithm implementation in OpenFOAM, a CFD software. The experimental results showed that in spite of ethanol and MEG being infinitely miscible in water, the mixing of these two inhibitors has completely different behavior. The implemented algorithm was capable to reproduce qualitatively the phenomena observed during experiments. What is more, the diffusive term seems not have relevance in macro-mixing process.Hidratos de gás natural são sólidos cristalinos formados a partir de moléculas de hidrocarbonetos de baixo peso molecular e água, em condições adequadas de temperatura e pressão. Na indústria do petróleo, um dos cenários mais prováveis de ocorrer a formação de bloqueio é a partida de poço. Quando há risco, um procedimento operacional usual é a substituição do conteúdo da linha seja substituído por óleo diesel ou morto. Entretanto, há cenários os quais este procedimento pode não ser a melhor opção e o uso da injeção controlada de inibidor termodinâmico pode ser a solução mais viável. Desta forma, este trabalho objetivou compreender o fenômeno de misturação entre inibidores termodinâmicos e água através da geração de dados experimentais e modelagem com posterior implementação do algoritmo no software CFD OpenFoam. Os resultados experimentais mostraram que, apesar do etanol e do MEG serem infinitamente miscíveis na água, a misturação destes dois inibidores tem comportamento completamente distinto. A modelagem implementada foi capaz de representar qualitativamente os fenômenos observados durante o experimento. Além disso, o termo difusivo não tem grande influência no processo de macro-mistura

Mejora del diagnóstico y de la hemodinámica en la revascularización carotídea : aplicación de la dinámica de fluidos computacional mediante el OpenFOAM® y otras herramientas de libre distribución

Stroke is a major cause of death and disability in Spain and in the Western world. It is often caused by an accumulation of atherosclerotic plaques on the walls of carotid arteries. Carotid revascularization may be the solution chosen by the specialist. This choice depends directly on the symptoms, the diagnosis and the potential benefits vs. costs of performing surgery. Hemodynamics plays a crucial role in all decision making. The conventional methods for analyzing hemodynamics are Doppler ultrasound, computed tomography angiography (CTA) and magnetic resonance angiography (MRA). These methods may be enriched with the numerical simulation of blood flow in the area of interest, using techniques of computational fluid dynamics (CFD). The result of the simulations can be used to improve diagnosis and to propose hemodynamic improvement during surgery or treatment. It can also provide conclusions on the progress of the patient. However, it is currently very difficult to perform these simulations and reach valid conclusions. This difficulty is due to the state of the technique and to the lack of scientific consensus in regard to clinical aspects, data gathering and processing, reproduction of geometries, construction of models, and execution of the simulations, among other aspects. Furthermore, obtaining results and drawing conclusions from them requires a high degree of specialization and the use of software that is often expensive. The present thesis uses numerical simulation to replicate the blood flow in the carotid arteries. It uses the results to guide the diagnosis and prognosis of patient progress. It develops a methodology for the creation of numeric models using data provided by CTA and Doppler ultrasound, both of which are used in routine clinical practice. From the images contained in the files with DICOM format resulting from the CTA, the geometries of carotid arteries of patients are reproduced. The data provided by the ultrasound velocities are used to obtain velocity curves in the inputs, outputs and areas of interest within the carotid artery. Models of carotid arteries are also built with CAD tools. OpenFOAM®; is used for model meshing, solving the equations that govern the fluid movement and obtaining the relevant hemodynamic variables such as carotid wall shear stress. The Womersley boundary condition for velocities, which is the most suitable one for simulating pulse flows in carotid arteries, is implemented in this software environment. In cases of moderate stenosis, a diagnosis by a specialist is added. A comparison between a pre- and postoperative situation was made in order to take it into account for any proposals of hemodynamic improvement. The pre-processing, processing and post-processing were performed almost entirely with open source tools such as vmtk, enGrid, ParaView and OpenFOAM®.El ictus es una de las principales causas de muerte e invalidez en España y en el mundo occidental. Su origen se debe, en muchos casos, a la acumulación de placas de ateromas en las paredes de las arterias carótidas. La revascularización carotídea, puede ser la solución elegida por el especialista. Dicha elección depende directamente de la sintomatología del paciente, del diagnóstico efectuado y de los posibles riesgos vs. beneficios, vinculados a realizar la intervención. La hemodinámica juega un papel fundamental en la toma de cualquier decisión. Su análisis con métodos convencionales como la ecografía Doppler, la angiografía por tomografía computarizada (angio-TC) y por resonancia magnética (angio-RM), puede ser enriquecido con la simulación numérica del flujo sanguíneo en la zona de interés, utilizando técnicas de fluidodinámica computacional (CFD). El resultado de las simulaciones podría ser utilizado para realizar un mejor diagnóstico y proponer mejoras hemodinámicas, durante la intervención o tratamiento. También aportaría nuevas conclusiones sobre la posible evolución del paciente. No obstante, realizar estos estudios computacionales y llegar a conclusiones válidas, presenta un alto grado de dificultad en la actualidad. Esta dificultad viene dada por el estado de la técnica y la no existencia de un consenso científico en cuanto a aspectos clínicos, toma y procesamientos de los datos, reproducción de geometrías, construcción de los modelos y a la propia realización de las simulaciones, entre otros. Al mismo tiempo obtener resultados y llegar a conclusiones a partir de estos, requiere de un alto grado de especialización y el uso de software que, en general, tiene un elevado coste económico. En el presente trabajo de tesis se emplea la simulación numérica para reproducir la circulación del flujo sanguíneo en las arterias carótidas. Utiliza los resultados para influir tanto en el diagnóstico, como en el pronóstico de la evolución del paciente. Se elabora una metodología para la creación de modelos numéricos utilizando los datos que aporta el angio-TC y la ecografía Doppler, ambas técnicas empleadas en la clínica habitual. A partir de las imágenes contenidas en ficheros con formato DICOM, resultados del angio-TC, se reproducen las geometrías de carótidas de pacientes y con los datos proporcionados por la ecografía Doppler se obtienen curvas de velocidades en las entradas, salidas y zonas de interés dentro de la arteria carótida. Son construidos además modelos de carótidas con herramientas CAD. OpenFOAM® es utilizado para realizar el mallado de los modelos, la resolución de las ecuaciones que gobiernan el movimiento del fluido y la obtención de variables hemodinámicas relevantes como la tensión de cizallamiento en la cara interna de la pared arterial carotídea. En el entorno de este software se implementa la condición de contorno Womersley para las velocidades, que es la más apropiada para simular de flujos pulsátiles en las carótidas. Para el caso de una estenosis moderada, se complementa un diagnóstico realizado por el especialista. Se ha efectuado una comparativa entre una situación pre y postperatoria con el objetivo de tenerla en cuenta ante posibles propuestas de mejoras hemodinámicas. El trabajo de pre-procesado, procesado y post-procesado ha sido realizado casi en su totalidad con herramientas de código abierto como vmtk, enGrid, ParaView y OpenFOAM® entre otra