3d Shell Research Articles

Efficient Electrochemical Oxygen Reduction to Hydrogen Peroxide Production from Nickel-Nitrogen-Doped Mesoporous Graphene Catalyst

Hydrogen peroxide(H2O2) is an excellent oxidizing agent with various uses in industrial bleaching, chemical synthesis, and wastewater treatment. Because of its wide range of applications, the global market demand is rapidly increasing. At present, over 95 % of H2O2 is produced through the anthraquinone process which is an environmentally unfriendly process. Therefore, numerous studies have focused on replacing this process for H2O2 with more eco-friendly processes. One of the alternative methods is the electrochemical production of H2O2 through oxygen reduction reaction(ORR), which offers an economical and environmentally friendly route to H2O2.The oxygen reduction reaction involves a multielectron transfer process in which O2 can be reduced to produce H2O in a four-electron process or undergo a two-electron pathway to form H2O2. However, the design of selective and active electrocatalysts remains a challenge due to competitive reaction pathways between two-electron and four-electron reduction.We develop 3D mesoporous graphene with high H2O2 production in neutral electrolytes by adjusting the pore size and regulating the atmosphere of Nickel single atom. This catalyst has 3D interconnected hollow N-doped graphene shells and Nickel single atoms will be atomically dispersed on N-doped graphene shells. The mesoporous structure with a large surface area accelerates mass transport. Moreover, electron-poor Nickel atoms yield high selectivity above 90 % and high activity for electrochemical oxygen reduction to produce H2O2 in neutral conditions. This result represents a benchmark for the two-electron ORR electrocatalyst in the neutral conditions.

Immersed boundary Mindlin-Reissner 3D shell element for modeling isotropic and laminated composite shells

An immersed boundary 3D shell element is presented here that is based on Mindlin-Reissner shell theory assumptions and uses quadratic B-spline approximation for the solution. It enables mesh independent analysis wherein the surface representing the shell geometry is defined independently and not by the mesh. The shell geometry is immersed in a uniform background mesh whose elements are 3D B-spline shell elements. By making the geometric model independent of the mesh, the typical difficulties associated with mesh generation can be avoided. The quadratic 3D B-spline shell elements in the mesh can represent the displacement field as a tangent continuous piece-wise polynomial approximation. The nodes of the element have three translational and no rotational degrees of freedom. The element is formulated under small-deformation and plane stress assumptions. Constructing the element based on shell theory enables the use of effective properties to model thin fiber reinforced laminated composite shell-like structures. The element formulation and the mesh independent approach are validated against a series of common shell element benchmark problems. • Immersed boundary 3D B-spline element based on Mindlin-Reissner shell theory assumptions. • Mesh independent analysis where geometry is embedded in a uniform background mesh. • The iso-parametric quadratic B-spline shell elements are used for C 1 continuous approximation. • Step boundary method (SBM) is used for applying boundary conditions. • Immersed boundary FEM for shells is validated for isotropic and composite shells.

Isotropic 3D printing using material extrusion of thin shell and post-casting of reinforcement core

Material extrusion (ME) can be used to manufacture a range of three-dimensional shapes by stacking extruded polymer layers with a heated nozzle. While the process is suitable for customized production in small quantities, the use of ME-printed features is often limited with regard to mechanical purposes due to the intrinsic anisotropic strength shortcoming, as parts can easily failure against a load in the transverse direction. In addition, the production speed for multiple parts is another major drawback preventing real competition with other mass manufacturing technologies. In this paper, we introduce an additive manufacturing strategy of shell pre-printing and core post-casting (referring as shell-core printing) that effectively enhances the isotropic strength and the production speed. Shell-core printing involves 3D printing a thin shell of the three-dimensional shape using the conventional ME method, followed by the injection and curing of a reinforcement resin inside the core. We show that the transverse strength of the layered shell can be reinforced by the core and that the reinforcement can be more effective when the shell-core interface roughness is effectively removed. Using an additional surface-polishing step between the pre-printing and the post-casting, the degree of isotropy with regard to the strength can be enhanced significantly from 0.4 to nearly 1, while the overall production time can also be reduced by half that in the conventional ME process. We also investigate the tensile behavior of the shell-core printed specimen and experimentally verify that the characteristics in general follow the classical theory of the rule of mixtures. In addition, we find that many different fracture modes exist in shell-core printed parts depending on the adhesive strength at the shell-core interface. We provide a theoretical criterion for the interfacial bonding energy which determines the different fracture behaviors and experimentally validate this in a mode II fracture test. • We introduce a shell-core printing strategy, material extrusion of 3D shell and casting of reinforcement material in the core. • Shell-core printing can improve the degree of isotropy in strength from 0.4 to nearly 1. • Total production time of shell-core printing can also be reduced by half that in general material extrusion 3D printing. • Shell-core Interface topography and adhesive strength determine the fracture behavior of the printed shell-core products.

Investigation and elimination of nonlinear Poisson stiffening in 3d and solid shell finite elements

AbstractWe show that most geometrically nonlinear three‐dimensional shell elements and solid shell elements suffer from a previously unknown artificial stiffening effect that only appears in geometrically nonlinear problems, in particular in the presence of large bending deformations. It can be interpreted as a nonlinear variant of the well‐known Poisson thickness locking effect. We explain why and under which circumstances this phenomenon appears and propose concepts to avoid it.

Experimental Research and Numerical Analysis of CFRP Retrofitted Masonry Triplets under Shear Loading.

This paper presents an experimental and numerical study into the shear response of brick masonry triplet prisms under different levels of precompression, as well as samples reinforced with carbon fiber-reinforced polymer (CFRP) strips. Masonry triplets were constructed with two different mortar mix ratios (1:1:3 and 1:1:5). In this study, finite element models for the analysis of shear triplets are developed using detailed micro-modelling (DMM) approach and validated with the experimental data. The failure mechanisms observed in the masonry triplets were simulated using a coupled XFEM-cohesive behaviour approach in ABAQUS finite element software. The nonlinear behaviour of mortar and brick was simulated using the concrete damaged plasticity (CDP) constitutive laws. The cohesive element with zero thicknesses was employed to simulate the behaviour of the unit–mortar interfaces. The extended finite element method (XFEM) was employed to simulate the crack propagation in the mortar layer without an initial definition of crack location. CFRP strips were simulated by 3D shell elements and connected to masonry elements by an interface model. The changes in failure mechanism and shear strength are calculated for varying types of mortar and fiber orientation of CFRP composite. Based on this study, it was concluded that the ultimate shear strength of masonry triplets is increased due to the external bonding of CFRP strips. The performance of masonry specimens strengthened with CFRP strips is assessed in terms of gain in shear strength and post-peak behaviour for all configurations and types of mortar considered. The comparison of FE and experimental results proved that the models have the potential to be used in practice to accurately predict the shear strength and reflect damage progression in unreinforced and CFRP-reinforced masonry triplets under in-plane loading, including the debonding of the CFRP reinforcement. Additionally, XFEM was found to be a powerful technique to be used for the location of crack initiation and crack propagation in the mortar layer.

Probabilistic Seismic Risk Analysis of Buried Pipelines Due to Permanent Ground Deformation for Victoria, BC

Buried continuous pipelines are prone to failure due to permanent ground deformation as a result of fault rupture. Since the failure mode is dependent on a number of factors, a probabilistic approach is necessary to correctly compute the seismic risk. In this study, a novel method to estimate regional seismic risk to buried continuous pipelines is presented. The seismic risk assessment method is thereafter illustrated for buried gas pipelines in the City of Victoria, British Columbia. The illustrated example considers seismic hazard from the Leech River Valley Fault Zone (LRVFZ). The risk assessment approach considers uncertainties of earthquake rupture, soil properties at the site concerned, geometric properties of pipes and operating conditions. Major improvements in this method over existing comparable studies include the use of stochastic earthquake source modeling and analytical Okada solutions to generate regional ground deformation, probabilistically. Previous studies used regression equations to define probabilistic ground deformations along a fault. Secondly, in the current study, experimentally evaluated 3D shell and continuum pipe–soil finite element models were used to compute pipeline responses. Earlier investigations used simple soil spring–beam element pipe models to evaluate the pipeline response. Finally, the current approach uses the multi-fidelity Gaussian process surrogate model to ensure efficiency and limit required computational resources. The developed multi-fidelity Gaussian process surrogate model was successfully cross-validated with high coefficients of determination of 0.92 and 0.96. A fragility curve was generated based on failure criteria from ALA strain limits. The seismic risks of pipeline failure due to compressive buckling and tensile rupture at the given site considered were computed to be 1.5 percent and 0.6 percent in 50 years, respectively.

Superior hybrid improper ferroelectricity and enhanced ferromagnetism of Ca3(Ti1-xCox)2O7 ceramics through the superexchange interaction

Ca3(Ti1-xCox)2O7 ceramics were prepared by a tartaric acid sol-gel method and sintered in an oxygen atmosphere. The introduction of Co2+/Co3+ as acceptor dopants leads to the formation of more oxygen vacancies and defect dipoles in Ca3(Ti1-xCox)2O7 ceramics. Oxygen vacancy and defect dipoles lead to the transition of dielectric, leakage, and ferroelectric behaviors of Ca3(Ti1-xCox)2O7 ceramics. The coexistence of hybrid improper ferroelectricity and ferromagnetism at room temperature in Ca3(Ti1-xCox)2O7 ceramics has been successfully realized through the superexchange interaction of Co–O–Co. Ca3(Ti1-xCox)2O7 ceramics exhibit superior ferroelectricity (the remnant polarization is 3.29 μC/cm2) and enhanced ferromagnetism (the remnant magnetization reaches 6.4×10−3 emu/g). This strategy based on the introduction of transition metal ions with unfilled 3d shells at B sites is an important approach to realize novel room-temperature single-phase multiferroic materials for Ca3Ti2O7-based materials.

Shell microelectrode arrays (MEAs) for brain organoids.

Brain organoids are important models for mimicking some three-dimensional (3D) cytoarchitectural and functional aspects of the brain. Multielectrode arrays (MEAs) that enable recording and stimulation of activity from electrogenic cells offer notable potential for interrogating brain organoids. However, conventional MEAs, initially designed for monolayer cultures, offer limited recording contact area restricted to the bottom of the 3D organoids. Inspired by the shape of electroencephalography caps, we developed miniaturized wafer-integrated MEA caps for organoids. The optically transparent shells are composed of self-folding polymer leaflets with conductive polymer–coated metal electrodes. Tunable folding of the minicaps’ polymer leaflets guided by mechanics simulations enables versatile recording from organoids of different sizes, and we validate the feasibility of electrophysiology recording from 400- to 600-μm-sized organoids for up to 4 weeks and in response to glutamate stimulation. Our studies suggest that 3D shell MEAs offer great potential for high signal-to-noise ratio and 3D spatiotemporal brain organoid recording.

Effect of different pitches on the 3D helically coiled shell and tube heat exchanger filled with a hybrid nanofluid: Numerical study and artificial neural network modeling

The effects of using hybrid nanofluids and of helical coil pitch (λ) in a 3D shell and tube heat exchanger (STHE) are investigated. The algorithm used in this study is Phase Coupled SIMPLE and the method used is Eulerian. Nanofluid flow with Reynolds (Re) numbers of 10,000, 15,000, and 20,000, nanoparticles with volume fractions (ϕ) of 2 and 4%, and λ = 20, 25, 40, and 50 mm are investigated. The highest numbers related to the thermal index (Nu) and effectiveness occurred in the λ = 20 mm and the maximum ϕ and Re. In the case of λ = 20 mm, the maximum Nusselt number is 15.8%, 26%, and 45.3% more than that of 25, 40, and 50 mm, respectively. However, in the same case, in comparison between the ϕ = 4% and ϕ = 0, the Nu increases by 45.7%, 61.7%, and 76%. The present study shows that combining using hybrid nanofluids and changing the geometry of STHE, as an innovative approach can positively increase efficiency. Finally, the results are used for training an artificial neural network (ANN). In this regard, for finding the optimum neuron numbers in the hidden layer, the optimum feed-forward network is obtained to predict the efficiency of the material.

Zeeman spectroscopy of the internal transition 4T1 to 6A1 of Fe3+ ions in ZnO

In this work, internal 4T1→6A1 transitions within the half-filled 3d shell of Fe3+ in extremely pure chemical vapor deposition (CVD)-grown ZnO layers were investigated by means of high-resolution, low-temperature continuous wave (cw) photoluminescence (PL), time-resolved PL, photoluminescence excitation (PLE) spectroscopy, Zeeman spectroscopy, and deep level transient spectroscopy (DLTS). For comparison, Zeeman spectroscopy measurements were also performed on commercially available, hydrothermally grown ZnO bulk crystals. Magnetic fields up to 15T were applied parallel and perpendicular to the c-axis of the ZnO crystals in order to investigate the fine structure of included states. The splitting pattern of emission lines related to 4T1→6A1 Fe3+ transitions was theoretically modeled by a Hamiltonian matrix including the crystal field in cubic and trigonal symmetries and spin–orbit interaction for the complete excited 4T1 state. The extremely pure ZnO used in this study, in direct comparison to hydrothermally grown ZnO, allows the identification, investigation, and description of single isolated Fe3+ defects in ZnO for the first time—different from literature reports hitherto, which seemingly were recording data on Fe–Li complexes. The resulting exact energy-level scheme in combination with the experimental data leads to a re-evaluation of 4T1→6A1 Fe3+ transitions in ZnO.

Lignin-derived hierarchical porous flower-like carbon nanosheets decorated with biomass carbon quantum dots for efficient oxygen reduction

Excavating and developing efficient and economical non-metallic nanomaterial catalysts for oxygen reduction reactions (ORR), which are vital for fuel cells, but is still challenging. Here, we synthesize a nitrogen-doped hierarchical porous flower-like carbon nanosheets decorated with nitrogen-doped carbon quantum dots. The hierarchically porosity heteroatom-doped flower-like carbon nanosheets are first synthesized using MgO as hard template, KOH/NaOH as activator, lignin/urea as carbon/heteroatom source, and then lignin-based carbon quantum dots (CQDs) fabricated via microwave hydrothermal are compounded with carbon nanosheets after a one-step hydrothermal treatment. Benefitting from the interconnection of its 3D graphite shell network, abundant active sites, high specific surface area, and multi-scale pore structure, the n-HPFN@CQDs exhibits favorable ORR activity and stability in 0.1 mol KOH media. Compared with commercial Pt/C, the assembled Zn-air batteries using n-HPFN@CQDs as electrode catalysts exhibit comparable discharge performance. This work synthesized a novel and green biomass-based carbon composite materials achieving high-performance for energy conversion applications.

Dynamic Properties Comparison of 1D, 2D, and 3D Model for Concrete Box-Girder Bridge of 40-meter Span

Concrete box-girder structure is considered the thin-walled structure, undergoing deformation and forces, as well as having structural rigidity in three dimensional directions. However, it’s commonly modeled as 1D structure for the sake of design practicality, which influences the numerical result of its dynamic properties when compared to both real time SHMS and field test result. To see how far the difference of the dynamic properties between 1D, 2D, and 3D model of concrete box-girder structure, the concrete box-girder structure is modeled as 1D (frame), 2D (shell), and 3D (solid) element with MIDAS Civil 2019. Considering the allowable deflection and stress limited by design code, concrete box-girder structure is modeled and analyzed as linearly elastic material. The dynamic properties obtained from these 3 models were compared with those obtained from real time SHMS and field test. These results indicate that both natural frequency and period of 2D and 3D models are close to those of real time SHMS and field test. However, the natural frequency of 1D model is slightly larger than the real SHMS and field test, indicating that 1D model gives the slightly overestimate natural frequency and structural rigidity compared to the reality. Unlike 2D and 3D model, the structure is accounted to have the uniform sectional rigidity along transversal direction in 1D model. This is why 1D model seems to have higher structural rigidity compared to 2D and 3D model, which subsequently yields the higher natural frequency than 2D and 3D model. This research proves that the designers’ discretion is advised if 1D model is used for the sake of design practicality.

On the frequencies of graphene nanoplatelet agglomerated nanocomposite paired paraboloidal-cylindrical shells under arbitrary boundary conditions

This paper evaluates the vibrational behavior of the complex types of nanocomposites paired shells with arbitrary support conditions. The paired shell comprises two segments, including a paraboloid and a cylinder. In addition, arbitrary support conditions are incorporated and investigated by thirty-six different cases of boundary conditions. The influence of using agglomerated Graphene Nano-Platelets (GNP) for reinforcing the polymer matrix on the natural frequency of the nanocomposite shells is studied by conducting the Eshelby-Mori-Tanaka scheme as an efficient homogenization procedure. Furthermore, the impact of the GNP accumulation throughout the polymer matrix is also considered in formulation by defining agglomeration factors. To attain the displacement fields of the shell structure, the three-dimensional (3D) shell approach and First-order Shear Deformation Theory (FSDT) are engaged. Afterward, Hamilton's principle determines the structure's total strain and kinetic energies. By applying the variational calculus, the governing differential equations of the structural model are available. In this step, a robust and reputable approximated numerical solution method, namely Generalized Differential Quadrature (GDQ), is used to discretize the shell structure by defining several grid points. Finally, the established eigenvalue problem is solved numerically to capture the structure's natural frequency. The authors validate their formulation by comparing the results obtained by the present procedure and the outputs of the Finite Element Method (FEM). Some more functional, intricate, and new nanocomposite Paired Paraboloidal-Cylindrical Shells (PPCS) are considered to be analyzed for achieving the associated natural frequency.

Boosting Interfacial Ion Transfer in Potassium-Ion Batteries via Synergy Between Nanostructured Bi@NC Bulk Anode and Electrolyte.

Using high-capacity alloy-type anodes can greatly advance potassium-ion batteries (PIBs). However, the primary limits are unstable solid electrolyte interphase (SEI) and tough interfacial ion transfer associated with large-size K+ during electrochemical (de)alloy reactions. Here, we achieve excellent energy storage performance of PIBs via the synergy between a nanostructured Bi@N-doped carbon (Bi@NC) bulk anode and a KPF6-dimethoxyethane (DME) electrolyte. The Bi@NC material with a high tap density of 3.81 g cm-3 is prepared by simply pyrolyzing a commercial Bi salt yet affords a favorable nano/microstructure consisting of Bi nanograins confined in 3D ultrathin N-doped carbon shells, facilitating electron/ion transport and structural integrity. Detailed impedance spectroscopy investigation unveils that K+ transport through SEI at the Bi@NC anode, rather than the desolvation of K+, dominates the interfacial K+ transfer. More importantly, spectroscopic and microscopic characterizations provide clear evidence that the interplay between Bi@NC anode and optimized KPF6-DME electrolyte can produce a unique SEI layer containing Bi3+-solvent complex that enables the activation energy of interfacial K+ transfer as low as 25.9 kJ mol-1, thereby ultrafast charge transfer at Bi@NC. Consequently, the Bi@NC anode in half cells achieves exceptional rate capability (206 mAh g-1 or 784 mAh cm-3 at 120C) accompanied by high specific capacity (331 mAh g-1 or 1261 mAh cm-3) and long cycle life (running 1400 cycles at 15C with a tiny capacity fading rate of 0.013% per cycle). Moreover, the Bi@NC anode and KPF6-DME electrolyte are also compatible with a potassium Prussian blue cathode and assembled full PIBs achieve stable cyclability (87.3% capacity retention after 100 cycles at 2.5C) and excellent rate performance (65.1% capacity retention upon increasing rates from 1 to 20C).

Investigation of the synergistic effect of platelet-rich plasma and polychromatic light on human dermal fibroblasts seeded chitosan/gelatin scaffolds for wound healing.

Conventional wound healing treatments are insufficient for chronic wounds caused by factors such as senescence of fibroblasts, reduced growth factor synthesis, and poor angiogenesis. Recently, tissue engineering approaches have been investigated to develop effective therapies. In this study, a biochemical/biophysical stimulant-based 3D system was developed for the healing of chronic wounds. In this direction, genipin crosslinked chitosan (CHT)/gelatin (GEL) scaffolds were fabricated by freeze-drying and loaded with platelet-rich plasma (PRP). The scaffolds were seeded with human dermal fibroblasts and then, polychromatic light in near infrared region (NIR) was applied to the scaffolds for activating the platelets and stimulating the fibroblasts (photoactivation, PAC). Thus, fibroblasts were stimulated both chemically and physically by PRP and light, respectively. Cell migration, proliferation, morphology, gene expressions and reactive oxygen species (ROS) activity were evaluated in-vitro. Laminin and collagen 4 expressions that are important for extracellular matrix (ECM) formation, and PDGF (Platelet-derived growth factor) and VEGF (Vascular endothelial growth factor) expressions that are important for vascularization significantly increased in the presence of both PRP and light. Besides, PRP and light improved cell migration in 3D core-and shell model synergistically. Hydrogen peroxide content decreased in both PRP and light, indicating inhibition of ROS production. It was concluded that the stimulation of platelets with light in the NIR has a great potential to use for both platelets activation and stimulation of fibroblasts. As a result, an effective therapy can be developed for chronic wounds by using scaffold-based 3D systems together with PRP and photostimulation.

Comparison of wind turbine blade structural models of different levels of complexity against experimental data

As the design process of a wind turbine blade is highly iterative, one needs to perform the same calculations several times. During that process, the kind of structural model that should be used must be chosen carefully, trying to obtain a good compromise between precision and model setup and computational time. This paper compares four different blade structural models having different levels of complexity. These models are compared to each other and also with experimental results with respect to their abilities to analyze blade cross-sectional properties, natural frequencies, deflection, strains, buckling strength, and composite strength. This comparison shows that even if the 3D shell finite element model is the more precise and is the only one that can manage the regions of the blade where the cross-sectional shape changes quickly, the strength of material based models gives accurate results. Even the simpler model, based on blade shape simplification, gives conservative and accurate results at a very low computational cost.

Modelling of in-plane seismic behaviour of one-way steel or timber jack arch floors in existing buildings. Application to the Eixample district of Barcelona

The type of floor system has a decisive role in the seismic performance of unreinforced masonry buildings. The in-plane stiffness of the floors has to be adequately represented in the numerical modelling of existing buildings, as it can influence their seismic capacity. This paper investigates the seismic behaviour of one-way arch floor systems composed of steel or timber beams, and ceramic tile vaults. The main objective of the research is to provide a numerical procedure for the simplified modelling of jack arch floor systems in the seismic assessment of unreinforced masonry buildings. The presented approach aims to provide values for the orthotropic properties of simplified floor models composed of elastic 2D shell elements. The orthotropic elastic properties are computed and calibrated by means of comparisons with detailed 3D nonlinear models of the floors. The case study is a multi-storey existing masonry building of the historical “Eixample” district in Barcelona, which includes one-way arch floor systems. The Finite Element Method has been used for the numerical simulation of the seismic performance through nonlinear static (pushover) analyses. The results of the study contribute to a better understanding of the effect of the behaviour of one-way floors with steel or timber beams and tile vaults on the seismic response of masonry buildings. This work provides indicative values for the proper modelling of these particular floor slabs. The proposed methodology is also applicable to the numerical simulation of any other one-way floor system.

Approaching the Limits of Aspect Ratio in Free‐Standing Al2O33D Shell Structures

Nanoscale free‐standing membranes are used for a variety of sensors and other micro/nano‐electro‐mechanical systems devices. To tune performance, it is indispensable to understand the limits of aspect ratios achievable. Herein, vapor hydrofluoric (VHF) processes are employed to release 3D shell structures made of atomic‐layer‐deposited Al2O3etch‐stop layers. Structure heights of 100–600 nm and widths of 1–200 nm are fabricated for membranes with 20 and 50 nm thickness. Undercut depths of and aspect ratios of 475:1 etch depth to structure width (50 nm films) and etch depth to membrane thicknesses of 495:0.02 (20 nm films) are achieved. The etch‐rate stagnates above a ratio of 31% hydrofluoric (HF), where decreasing EtOH shares reduce reproducibility. Etch rates reach 0.75 mm min−1and are generally constant over vapor etch depth. For 100 nm heights and widths of , etch rates however stagnate for deeper depths. All explored structures remained stable with widths up to 5 μm independent of the height. Above width, top membranes deflect, likely from stress accumulated during deposition. Herein, exploring and understanding the limits of aspect ratio in future free‐standing membrane devices are helped.

An innovative multi-layer shell model for in-pile thermo-mechanical behavior analysis of plate-type fuel assemblies

In this study, an innovative large-deformation multi-layer shell model is developed. In order to improve the efficiency of simulating the thermo-mechanical coupling behavior in complex plate-type fuel assemblies, the fuel plates are simulated by 2D shell element, with the irradiation swelling and creep effects involved. The specific theoretical frame for the kinematic models and three-dimensional constitutive models is presented, together with the generalized force update algorithm. The application of the developed shell model in the thermal–mechanical behavior simulation of a monolithic U-Mo/Al fuel assembly indicates that (1) the out-of-plane displacements of the side plates can be precisely calculated, with the calculation time ∼92% shorter than that of a full 3D simulation of 308-day irradiation behavior; (2) the out-of-plane displacements of the fuel plates excluding the peripheral ones can also be well obtained, with small relative deviations to the full 3D simulation results; (3) using 3D solid models for the peripheral fuel plates, a fuel assembly finite element (FE) model with 2D&3D geometric models for the fuel plates is proposed with a total computation time decrease of 64%, and the precise of deformation simulation results can be improved comprehensively. This research provides important theoretical models and algorithms for the irradiation-induced deformation analysis of complex plate-type fuel assemblies.

A 3D Transient CFD Simulation of a Multi-Tubular Reactor for Power to Gas Applications

A 3D stationary CFD study was conducted in our previous work, resulting in a novel reactor design methodology oriented to upgrading biogas through CO2 methanation. To enhance our design methodology incorporating relevant power to gas operational conditions, a novel transient 3D CFD modelling methodology is employed to simulate the effect of relevant dynamic disruptions on the behaviour of a tubular fixed bed reactor for biogas upgrading. Unlike 1D/2D models, this contribution implements a full 3D shell cooled methanation reactor considering real-world operational conditions. The reactor’s behaviour was analysed considering the hot-spot temperature and the outlet CH4 mole fraction as the main performance parameters. The reactor start-up and shutdown times were estimated at 330 s and 130 s, respectively. As expected, inlet feed and temperature disruptions prompted “wrong-way” behaviours. A 30 s H2 feed interruption gave rise to a transient low-temperature hot spot, which dissipated after 60 s H2 feed was resumed. A 20 K rise in the inlet temperature (523–543 K) triggered a transient low-temperature hot spot (879 to 850 K). On the contrary, a 20 K inlet temperature drop resulted in a transient high-temperature hot spot (879 to 923 K), which exposed the catalyst to its maximum operational temperature. The maximum idle time, which allowed for a warm start of the reactor, was estimated at three hours in the absence of heat sources. No significant impacts were found on the product gas quality (% CH4) under the considered disruptions. Unlike typical 1D/2D simulation works, a 3D model allowed to identify the relevant design issues like the impact of hot-spot displacement on the reactor cooling efficiency.