Three-dimensional computational fluid dynamics modeling of anode-supported planar SOFC

CFD modeling using reactions kinetics for selective hydrogenation for acetylene in a fixed-bed reactor

A simple one-dimensional (1D) computational fluid dynamics (CFD) model of the chemical oxygen iodine laser (COIL) with supersonic mixing is compared with three-dimensional (3D) CFD models and with experimental measurements of the COIL parameters. Dependence of the gain, iodine dissociation fraction and temperature at the resonator optical axis and of the output lasing power on the iodine flow rate predicted by the 1D model is in good agreement with that found using 3D models and experimental results. Hence the 1D model can be used instead of much more complicated 3D models for estimates of the working parameters of supersonic COILs.

A three-dimensional computational fluid dynamics (CFD) model has been created to model high-temperature steam electrolysis in a planar solid oxide electrolysis cell (SOEC). The model represents a single cell, as it would exist in an electrolysis stack. Details of the model geometry are specific to a stack that was fabricated by Ceramatec, Inc. and tested at the Idaho National Laboratory. Mass, momentum, energy, and species conservation and transport are provided via the core features of the commercial CFD code FLUENT. A solid-oxide fuel cell (SOFC) model adds the electrochemical reactions and loss mechanisms and computation of the electric field throughout the cell. The FLUENT SOFC user-defined subroutine was modified for this work to allow for operation in the SOEC mode. Model results provide detailed profiles of temperature, Nernst potential, operating potential, anode-side gas composition, cathode-side gas composition, current density and hydrogen production over a range of stack operating conditions. Mean model results are shown to compare favorably with experimental results obtained from an actual ten-cell stack tested at INL.

Modeling a thermoplate conical heat exchanger in a point focus solar thermal collector

It is always an important research direction to improve the performance of solid oxide fuel cells (SOFCs) through structural optimization. For anode-supported SOFC, the thin cathode thickness results in an uneven distribution of oxygen concentration in the porous electrode, which limits the output performance. In this paper, a three-dimensional model of the anode-supported planar SOFC was established, and the thickness of the cathode diffusion layer in the area covered by the connector was increased to improve the uniformity of oxygen distribution in the cathode. The results show that increasing the thickness of the cathode diffusion layer under the connector can significantly improve the overall output performance of SOFC. The uniformity of oxygen concentration distribution in the cathode is improved, the local current density under the connector is increased, and the maximum output power density of the cell is increased by 29.14%. The results show that the output performance of the SOFC and the uniformity of gas distribution in the porous electrode can be improved by increasing the thickness of the cathode diffusion layer under the connector in the structure design and practical application of the SOFC. The research of this paper provides a reference for the optimization design of SOFC.

In this study, a high-fidelity, full-scale three-dimensional Computational Fluid Dynamics (CFD) model was developed to analyze the effects of U-type and Z-type interconnection configurations on flow and distribution uniformity within a 4 × 1 kW planar solid oxide fuel cell (SOFC) stack composed of 40 unit cells. Mesh independence was verified using the Richardson extrapolation method. The results reveal that on the anode (fuel inlet) side, the Z-type configuration exhibits significantly better flow and pressure uniformity than the U-type configuration and shows low sensitivity to variations in fuel utilization (Uf = 0.3–0.8), maintaining stable flow distribution under different conditions. On the cathode (air inlet) side, however, the U-type configuration demonstrates superior flow stability at an air utilization rate of 0.3. Therefore, it is recommended to employ the Z-type configuration for the anode and the U-type configuration for the cathode to achieve more uniform gas distribution and enhanced operational stability. These findings provide valuable insights for optimizing the design and operation of solid oxide fuel cells (SOFCs) and offer guidance for the development of more efficient fuel cell systems.

Electrochemical performance optimization of a conventional solid oxide fuel cell (SOFC) has been massively performed with computational fluid dynamic (CFD) modelling but it’s usage in a proton conducting fuel cell (PCFC) is still minimal. PCFC is a category of SOFC but with proton conductor as electrolyte instead of oxygen-ion conductor in a conventional SOFC. The fabrication of high electrochemical performance of PCFC is desirable because of its ability to operate at lower temperature. The objective of this short review study is to explore the possibilities of CFD modelling application to improve electrochemical performance of a PCFC system. Some CFD study that have been done to SOFC and PCFC were reviewed. One main finding from this short review is that the application of CFD modelling in PCFC design optimization is still minimal. There is a lack of studies that focus on the impact of PCFC anode microstructure on transport phenomena of the PCFC; for example on gas diffusion. It was also found that CFD modelling software Ansys Fluent with add-on Fluent SOFC module that is widely applied to conventional oxygen-ion SOFC need to be modify using User Defined Function (UDF) in order to be used in PCFC system.

A three-dimensional computational fluid dynamics (CFD) model is developed to simulate urban flow and dispersion, to understand fluid dynamical processes therein, and to provide practical solutions to some emerging problems of urban air pollution. The governing equations are the Reynolds-averaged equations of momentum, mass continuity, heat, and other scalar (here, passive pollutant) under the Boussinesq approximation. The Reynolds stresses and turbulent fluxes are parameterized using the eddy diffusivity approach. The turbulent diffusivities of momentum, heat, and pollutant concentration are calculated using the prognostic equations of turbulent kinetic energy and its dissipation rate. The set of governing equations is solved numerically on a staggered, nonuniform grid system using a finite-volume method with the semi-implicit method for pressure-linked equation (SIMPLE) algorithm. The CFD model is tested for three different building configurations: infinitely long canyon, long canyon of finite length, and orthogonally intersecting canyons. In each case, the CFD model is shown to simulate urban street-canyon flow and pollutant dispersion well.

Due to mismatching of thermophysical properties between involved materials, a non-uniform distribution of generated thermal stress may result in a deformation and warpage in the cell sintering steps for SOFC (solid oxide fuel cell). A three-dimensional CFD (computational fluid dynamics) model is developed to study the displacement and thermal stress distribution within the SOFC sintered functional layers. It is found that the thermal stress is concentrated on the interface between the anode and the electrolyte layers; the warpage is larger during the co-sintering of anode and electrolyte layers (i.e., half-cell sintering). A parameter study is also conducted for the thickness variation of the anode, as well as for the four corners being chamfered. Considering effects of microscopic structure evolution on the cell shrinkage, a correlated method is developed to evaluate the thermal expansion coefficients varied with the sintering temperature. It is found that the difference becomes bigger in the correlated thermal expansion coefficients between the YSZ and anode layers, which leads to even larger displacement predictions. The findings and predicted results may be applied for optimization of the material designs and the sintering parameters for SOFC.

Performance prediction of proton exchange membrane fuel cells using a three-dimensional model

Integrated gasification fuel cell (IGFC) systems combining coal gasification and solid oxide fuel cells (SOFC) are promising for highly efficient and environmentally friendly utilization of coal for power production. Most IGFC system analyses performed to-date have used nondimensional thermodynamic SOFC models that do not resolve the intrinsic constraints of SOFC operation. In this work a quasi-two-dimensional (2D) finite volume model for planar SOFC is developed and verified using literature data. Special attention is paid to making the model capable of supporting recent SOFC technology improvements, including the use of anode-supported configurations, metallic interconnects, and reduced polarization losses. Activation polarization parameters previously used for high temperature electrolyte-supported SOFC result in cell performance that is much poorer than that observed for modern intermediate temperature anode-supported configurations; thus, a sensitivity analysis was conducted to identify appropriate parameters for modern SOFC modeling. Model results are shown for SOFC operation on humidified H2 and CH4 containing syngas, under coflow and counterflow configurations; detailed internal profiles of species mole fractions, temperature, current density, and electrochemical performance are obtained. The effects of performance, fuel composition, and flow configuration of SOFC performance and thermal profiles are evaluated, and the implications of these results for system design and analysis are discussed. The model can be implemented not only as a stand-alone SOFC analysis tool, but also a subroutine that can communicate and cooperate with chemical flow sheet software seamlessly for convenient IGFC system analysis.

In this chapter, the construction, principle of operation, types and production technologies of SOFCs are presented and characterized. Three main types of SOFC are described according to the type of support layer responsible for the mechanical strength of the cell: electrolyte-supported solid oxide fuel cells (ES-SOFC), anode-supported solid oxide fuel cells (AS-SOFC), and metal-supported solid oxide fuel cells (MS-SOFC). Base and raw materials for particular functional layers of solid oxide fuel cells are characterized, i.e., anode, electrolyte, and cathode layers. Thick- and thin-film technologies for the production of particular elements of SOFC fuel cells are presented. Using the example of technology developed in the Institute of Power Engineering Ceramic Department CEREL, the production technology of anode-supported solid oxide fuel cells and the method of characterizing the microstructure and electrochemical properties of the produced cells are presented.

Recent approach based heterogeneous comprehensive learning Archimedes optimization algorithm for identifying the optimal parameters of different fuel cells

A geyser in a closed conduit system is characterized by an explosive release of a mixture of air and water through a drop shaft. Geysers are often observed in combined sewer systems (CSSs) as an explosive form of combined sewer overflows (CSOs). In the present work, the flow characteristics of sewer geyser phenomenon are studied numerically using a three-dimensional computational fluid dynamics (CFD) model for the first time. Traditionally, investigations of flow processes associated with sewer geysers are conducted through physical experiments and one or two-dimensional numerical models. However, sewer geysers are undeniably three-dimensional, hence 3D models are necessary to gain further understanding of the phenomena. The CFD model was calibrated using an experiment that exhibit characteristics of sewer geysers.

In this study, a three-dimensional computational fluid dynamics (CFD) model is employed to investigate the hydrodynamic and combustion characteristics of biomass particles in an industrial-scale circulating fluidized bed (CFB) furnace. The CFD model considered here is based on the Eulerian-Lagrangian framework, the multi-phase particle-in-cell (MP-PIC) collision model, the coarse grain method (CGM), and a recently developed distribution kernel method (DKM). The challenge of simulating industrial-scale CFB furnaces using CFD lies in the large number of particles in the system. MP-PIC and CGM showed that local particle overloading could occur, causing the numerical simulation to diverge. The combination of MP-PIC with CGM and DKM was shown to overcome this problem. The CFD predictions werecompared with onsite temperature experiments in the furnace, and the predicted furnace temperature agreed fairly well with the measured data. Using the CFD results, the study analyzed the transient solids mixing and fluidization characteristics, as well as the thermochemical process in biomass combustion. The simulated individual particle provided insight into the physical and chemical processes of the granular flow in the dilute/dense regions of the CFB furnace. The simulated results revealed the CO and NOx emission processes in the furnace.