| 1. |
- Aravind, P. V., et al.
(författare)
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Negative emissions at negative cost-an opportunity for a scalable niche
- 2022
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Ingår i: Frontiers in Energy Research. - : Frontiers Media SA. - 2296-598X. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- In the face of the rapidly dwindling carbon budgets, negative emission technologies are widely suggested as required to stabilize the Earth's climate. However, finding cost-effective, socially acceptable, and politically achievable means to enable such technologies remains a challenge. We propose solutions based on negative emission technologies to facilitate wealth creation for the stakeholders while helping to mitigate climate change. This paper comes up with suggestions and guidelines on significantly increasing carbon sequestration in coffee farms. A coffee and jackfruit agroforestry-based case study is presented along with an array of technical interventions, having a special focus on bioenergy and biochar, potentially leading to "negative emissions at negative cost. " The strategies for integrating food production with soil and water management, fuel production, adoption of renewable energy systems and timber management are outlined. The emphasis is on combining biological and engineering sciences to devise a practically viable niche that is easy to adopt, adapt and scale up for the communities and regions to achieve net negative emissions. The concerns expressed in the recent literature on the implementation of emission reduction and negative emission technologies are briefly presented. The novel opportunities to alleviate these concerns arising from our proposed interventions are then pointed out. Our analysis indicates that 1 ha coffee jackfruit-based agroforestry can additionally sequester around 10 tonnes of CO2-eq and lead to an income enhancement of up to 3,000-4,000 Euros in comparison to unshaded coffee. Finally, the global outlook for an easily adoptable nature-based approach is presented, suggesting an opportunity to implement revenue-generating negative emission technologies on a gigatonne scale. We anticipate that our approach presented in the paper results in increased attention to the development of practically viable science and technology-based interventions in order to support the speeding up of climate change mitigation efforts.
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| 2. |
- Bian, Boshen, et al.
(författare)
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Scalability of Nek5000 on High-Performance Computing Clusters Toward Direct Numerical Simulation of Molten Pool Convection
- 2022
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Ingår i: Frontiers in Energy Research. - : Frontiers Media SA. - 2296-598X. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- In a postulated severe accident, a molten pool with decay heat can form in the lower head of a reactor pressure vessel, threatening the vessel’s structural integrity. Natural convection in molten pools with extremely high Rayleigh (Ra) number is not yet fully understood as accurate simulation of the intense turbulence remains an outstanding challenge. Various models have been implemented in many studies, such as RANS (Reynolds-averaged Navier–Stokes), LES (large-eddy simulation), and DNS (direct numerical simulation). DNS can provide the most accurate results but at the expense of large computational resources. As the significant development of the HPC (high-performance computing) technology emerges, DNS becomes a more feasible method in molten pool simulations. Nek5000 is an open-source code for the simulation of incompressible flows, which is based on a high-order SEM (spectral element method) discretization strategy. Nek5000 has been performed on many supercomputing clusters, and the parallel performance of benchmarks can be useful for the estimation of computation budgets. In this work, we conducted scalability tests of Nek5000 on four different HPC clusters, namely, JUWELS (Atos Bullsquana X1000), Hawk (HPE Apollo 9000), ARCHER2 (HPE Cray EX), and Beskow (Cray XC40). The reference case is a DNS of molten pool convection in a hemispherical configuration with Ra = 1011, where the computational domain consisted of 391 million grid points. The objectives are (i) to determine if there is strong scalability of Nek5000 for the specific problem on the currently available systems and (ii) to explore the feasibility of obtaining DNS data for much higher Ra. We found super-linear speed-up up to 65536 MPI-rank on Hawk and ARCHER2 systems and around 8000 MPI-rank on JUWELS and Beskow systems. We achieved the best performance with the Hawk system with reasonably good results up to 131072 MPI-rank, which is attributed to the hypercube technique on its interconnection. Given the current HPC technology, it is feasible to obtain DNS data for Ra = 1012, but for cases higher than this, significant improvement in hardware and software HPC technology is necessary.
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| 3. |
- Cousins, Dylan S., et al.
(författare)
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Near-Infrared Spectroscopy can Predict Anatomical Abundance in Corn Stover
- 2022
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Ingår i: Frontiers in Energy Research. - : Frontiers Media S.A.. - 2296-598X. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Feedstock heterogeneity is a key challenge impacting the deconstruction and conversion of herbaceous lignocellulosic biomass to biobased fuels, chemicals, and materials. Upstream processing to homogenize biomass feedstock streams into their anatomical components via air classification allows for a more tailored approach to subsequent mechanical and chemical processing. Here, we show that differing corn stover anatomical tissues respond differently to pretreatment and enzymatic hydrolysis and therefore, a one-size-fits-all approach to chemical processing biomass is inappropriate. To inform on-line downstream processing, a robust and high-throughput analytical technique is needed to quantitatively characterize the separated biomass. Predictive correlation of near-infrared spectra to biomass chemical composition is such a technique. Here, we demonstrate the capability of models developed using an “off-the-shelf,” industrially relevant spectrometer with limited spectral range to make strong predictions of both cell wall chemical composition and the relative abundance of anatomical components of the corn stover, the latter for the first time ever. Gaussian process regression (GPR) yields stronger correlations (average R2v = 88% for chemical composition and 95% for anatomical relative abundance) than the more commonly used partial least squares (PLS) regression (average R2v = 84% for chemical composition and 92% for anatomical relative abundance). In nearly all cases, both GPR and PLS outperform models generated using neural networks. These results highlight the potential for coupling NIRS with predictive models based on GPR due to the potential to yield more robust correlations.
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| 4. |
- Ericsson, Tore, et al.
(författare)
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Investigation of Valence Mixing in Sodium-Ion Battery Cathode Material Prussian White by Mossbauer Spectroscopy
- 2022
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Ingår i: Frontiers in Energy Research. - : Frontiers Media S.A.. - 2296-598X. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Prussian white (PW), Na2Fe [Fe(CN)(6)], is a highly attractive cathode material for sustainable sodium-ion batteries due to its high theoretical capacity of similar to 170 mAhg(-1) and low-cost synthesis. However, there exists significant variability in the reported electrochemical performance. This variability originates from compositional flexibility possible for all Prussian blue analogs (PBAs) and is exasperated by the difficulty of accurately quantifying the specific composition of PW. This work presents a means of accurately quantifying the vacancy content, valence distribution, and, consequently, the overall composition of PW via Mossbauer spectroscopy. PW cathode material with three different sodium contents was investigated at 295 and 90 K. The observation of only two iron environments for the fully sodiated compound indicated the absence of [Fe(CN)(6)](4-) vacancies. Due to intervalence charge transfer between iron centers at 295 K, accurate determination of valences was not possible. However, by observing the trend of spectral intensities and center shift for the nitrogen-bound and carbon-bound iron, respectively, at 90 K, valence mixing between the iron sites could be quantified. By accounting for valence mixing, the sum of iron valences agreed with the sodium content determined from elemental analysis. Without an agreement between the total valence sum and the determined composition, there exists uncertainty around the accuracy of the elemental analysis and vacancy content determination. Thus, this study offers one more stepping stone toward a more rigorous characterization of composition in PW, which will enable further optimization of properties for battery applications. More broadly, the approach is valuable for characterizing iron-based PBAs in applications where precise composition, valence determination, and control are desired.
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| 5. |
- Gong, Yaopeng, et al.
(författare)
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Density Measurement of Molten Drop With Aerodynamic Levitation and Laser Heating
- 2022
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Ingår i: Frontiers in Energy Research. - : Frontiers Media SA. - 2296-598X. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Thermophysical properties of molten core materials (corium) are necessary input parameters of models and computer codes which predict the severe accident progression in light water reactors. The corium contains the components of UO2, ZrO2, Zr and Fe. The measurement of molten corium properties is a very challenging task due to high melting points of corium which can reach 3000 K. This paper presents a density measurement system for a molten drop based on techniques of aerodynamic levitation, laser heating and image processing. A sphere of alumina was firstly levitated by argon gas flow above a conical converging-diverging nozzle. The sphere was then heated up and melted into a liquid drop by a laser beam. The shape of the drop was recorded by a high-speed camera, and the density was calculated from image processing.
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| 6. |
- Gustafsson, Olof, 1992-, et al.
(författare)
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Mind the miscibility gap : Cation mixing and current density driven non-equilibrium phase transformations in spinel cathode materials
- 2022
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Ingår i: Frontiers in Energy Research. - : Frontiers Media S.A.. - 2296-598X. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Cathode materials that exhibit phase transitions with large structural rearrangements during electrochemical cycling are generally seen as disadvantageous. Large volume changes and lattice mismatches between intermediate phases tend to lead to significant kinetic barriers, as well as strain and particle cracking. In this regard, solid solution reactions are more desirable as they provide lower energy barriers and no miscibility gap between co-existing phases. The high-voltage cathode material LiNi0.5Mn1.5O4 is an interesting candidate for high power and rate capability applications, however little is known on how its phase transitions occur on the particle level. In the presented work operando X-ray diffraction was utilized together with detailed peak profile analysis to elucidate the phase transition mechanism dependency on transition metal cation order and current density. When fully disordered, the material was found to undergo a bulk single-phase solid solution reaction between the intermediate phases LiNi0.44Mn1.56O4 and Li0.5Ni0.44Mn1.56O4 followed by a first order phase transition with a coherent interphase between the intermediates Li0.5Ni0.44Mn1.56O4 and Ni0.44Mn1.6O4. When fully ordered and slightly less ordered, two separate first order phase transitions with a coherent interphase between the same intermediate phases were observed. On discharge, the fast kinetics of the transition between Li0.5Ni0.44Mn1.56O4 and LiNi0.44Mn1.56O4 resulted in less strain on the former phase. For all samples the miscibility gap between the intermediate phases narrowed with increased current density, suggesting that the solid solution domain formed at the coherent interphase can be extended when the rate of (de)lithiation exceeds the movement speed of the interphase at the phase transition. This effect was found to be larger with increasing cation disorder. The influence of transition metal ordering on the ability to form solid solutions is in good agreement with computational phase diagrams of LiNi0.5Mn1.5O4, showing that disorder is important for promoting and stabilizing solid solutions. These results indicate that the degree of transition metal ordering within the material is of importance for obtaining a material with small lattice mismatches between the involved intermediate phases and for rational design of full solid solution materials.
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| 7. |
- Jafri, Yawer, 1988-, et al.
(författare)
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Double Yields and Negative Emissions? : Resource, Climate and Cost Efficiencies in Biofuels With Carbon Capture, Storage and Utilization
- 2022
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Ingår i: Frontiers in Energy Research. - : Frontiers Media S.A.. - 2296-598X. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- As fossil-reliant industries turn to sustainable biomass for energy and material supply, the competition for biogenic carbon is expected to intensify. Using process level carbon and energy balance models, this paper shows how the capture of residual CO2 in conjunction with either permanent storage (CCS) or biofuel production (CCU) benefits fourteen largely residue-based biofuel production pathways. With a few noteworthy exceptions, most pathways have low carbon utilization efficiencies (30–40%) without CCS/U. CCS can double these numbers and deliver negative emission biofuels with GHG footprints below −50 g CO2 eq./MJ for several pathways. Compared to CCS with no revenue from CO2 sequestration, CCU can offer the same efficiency gains at roughly two-third the biofuel production cost (e.g., 99 EUR/MWh vs. 162 EUR/MWh) but the GHG reduction relative to fossil fuels is significantly smaller (18 g CO2 eq./MJ vs. −99 g CO2 eq./MJ). From a combined carbon, cost and climate perspective, although commercial pathways deliver the cheapest biofuels, it is the emerging pathways that provide large-scale carbon-efficient GHG reductions. There is thus some tension between alternatives that are societally best and those that are economically most interesting for investors. Biofuel pathways vent CO2 in both concentrated and dilute streams Capturing both provides the best environomic outcomes. Existing pathways that can deliver low-cost GHG reductions but generate relatively small quantities of CO2 are unlikely to be able to finance the transport infrastructure required for transformative bio-CCS deployment. CCS and CCU are accordingly important tools for simultaneously reducing biogenic carbon wastage and GHG emissions, but to unlock their full benefits in a cost-effective manner, emerging biofuel technology based on the gasification and hydrotreatment of forest residues need to be commercially deployed imminently. Copyright © 2022 Jafri, Ahlström, Furusjö, Harvey, Pettersson, Svensson and Wetterlund.
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| 8. |
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| 9. |
- Mesfun, Sennai, et al.
(författare)
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Electrolysis Assisted Biomass Gasification for Liquid Fuels Production
- 2022
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Ingår i: Frontiers in Energy Research. - : Frontiers Media S.A.. - 2296-598X. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Gasification is a promising pathway for converting biomass residues into renewable transportation fuels and chemicals needed to comply with the ambitious Swedish environmental targets. The paper investigates the integration of a molten carbonate electrolysis cell (MCEC) in biofuel production pathway from sawmill byproducts, to improve the performance of gas cleaning and conditioning steps prior to the final conversion of syngas into liquid biofuels. The energy, material, and economic performance of process configurations with different gasification technologies are simulated and compared. The results provide relevant information to develop the engineering of gas-to-liquid transportation fuels utilizing renewable electricity. The MCEC replaces the water-gas shift step of a conventional syngas conditioning process and enables increased product throughput by as much as 15%–31%. Depending on the process configuration and steam-methane reforming technology, biofuels can be produced to the cost range 140–155 €/MWh in the short-term. Copyright © 2022 Mesfun, Engvall and Toffolo.
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| 10. |
- Munir, M. Adeel, et al.
(författare)
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Blockchain Adoption for Sustainable Supply Chain Management : Economic, Environmental, and Social Perspectives
- 2022
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Ingår i: Frontiers in Energy Research. - : Frontiers Media S.A.. - 2296-598X. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Due to the rapid increase in environmental degradation and depletion of natural resources, the focus of researchers is shifted from economic to socio-environmental problems. Blockchain is a disruptive technology that has the potential to restructure the entire supply chain for sustainable practices. Blockchain is a distributed ledger that provides a digital database for recording all the transactions of the supply chain. The main purpose of this research is to explore the literature relevant to blockchain for sustainable supply chain management. The focus of this review is on the sustainability of the blockchain-based supply chain concerning environmental conservation, social equality, and governance effectiveness. Using a systematic literature review, a total of 136 articles were evaluated and categorized according to the triple bottom-line aspects of sustainability. Challenges and barriers during blockchain adoption in different industrial sectors such as aviation, shipping, agriculture and food, manufacturing, automotive, pharmaceutical, and textile industries were critically examined. This study has not only explored the economic, environmental, and social impacts of blockchain but also highlighted the emerging trends in a circular supply chain with current developments of advanced technologies along with their critical success factors. Furthermore, research areas and gaps in the existing research are discussed, and future research directions are suggested. The findings of this study show that blockchain has the potential to revolutionize the entire supply chain from a sustainability perspective. Blockchain will not only improve the economic sustainability of the supply chain through effective traceability, enhanced visibility through information sharing, transparency in processes, and decentralization of the entire structure but also will help in achieving environmental and social sustainability through resource efficiency, accountability, smart contracts, trust development, and fraud prevention. The study will be helpful for managers and practitioners to understand the procedure of blockchain adoption and to increase the probability of its successful implementation to develop a sustainable supply chain network.
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| 11. |
- Nandakishor, T. M., et al.
(författare)
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Agroforestry in Shade Coffee Plantations as an Emission Reduction Strategy for Tropical Regions : Public Acceptance and the Role of Tree Banking
- 2022
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Ingår i: Frontiers in Energy Research. - : Frontiers Media SA. - 2296-598X. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Support for the adoption of climate change mitigation measures in low-income regions depends on how such activities contribute to generating household income and gaining confidence from the local community. The planning of mitigation measures or pro-environmental activities need to consider the cost of deployment, customization of activities according to local conditions, and socio-cultural background and perceptions of people. This paper analyses the incentive induced "agroforestry" or "planting trees in farmland" as part of the Carbon Neutral Programme supported by the Government of Kerala in Meenangadi Grama Panchayath, Wayanad district. An increase in tree cover is proposed as a strategy for increasing carbon sequestration. Planting more trees in farmland (except grain cultivated areas) along with crops, according to farmers, may reduce crop yield and discourage farmers' participation. The Government of Kerala put forward the concept of a tree banking/tree incentive program to attract farmers to expand tree cover. A survey was conducted among 100 individuals from the Meenangadi Grama Panchayath to assess the perceptions and concerns of farmers about the proposed "Agroforestry"/Tree Banking program. The sample size was chosen from the population assuming a 9.98% error tolerance. Tree Banking Programme designed to encourage farmers to plant trees has gained public interest, and the study also documented the factors influencing the willingness of farmers for planting trees. The study revealed that the majority of the individuals (93% of the survey participants) residing in the region are interested in supporting the activities for climate change mitigation. Financial incentives announced under tree banking generated interest among farmers. 89% of the survey participants consider the incentive scheme to be an attractive option, as it can compensate for the short-term loss in crop productivity. However, farmers were very selective in choosing the tree species to be planted on their farms. Incentivization helps to make sure that a large proportion of the planted saplings will grow into mature trees. Overall, it can be concluded that afforestation in the form of agroforestry could be potentially attractive to the farmers and contribute towards achieving carbon neutrality for tropical agricultural areas.
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| 12. |
- Saif-Ul-Allah, Muhammad Waqas, et al.
(författare)
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Computationally Inexpensive 1D-CNN for the Prediction of Noisy Data of NOx Emissions From 500 MW Coal-Fired Power Plant
- 2022
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Ingår i: Frontiers in Energy Research. - : FRONTIERS MEDIA SA. - 2296-598X. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Coal-fired power plants have been used to meet the energy requirements in countries where coal reserves are abundant and are the key source of NOx emissions. Owing to the serious environmental and health concerns associated with NOx emissions, much work has been carried out to reduce NOx emissions. Sophisticated artificial intelligence (AI) techniques have been employed during the past few decades, such as least-squares support vector machine (LSSVM), artificial neural networks (ANN), long short-term memory (LSTM), and gated recurrent unit (GRU), to develop the NOx prediction model. Several studies have investigated deep neural networks (DNN) models for accurate NOx emission prediction. However, there is a need to investigate a DNN-based NOx prediction model that is accurate and computationally inexpensive. Recently, a new AI technique, convolutional neural network (CNN), has been introduced and proven superior for image class prediction accuracy. According to the best of the author's knowledge, not much work has been done on the utilization of CNN on NOx emissions from coal-fired power plants. Therefore, this study investigated the prediction performance and computational time of one-dimensional CNN (1D-CNN) on NOx emissions data from a 500 MW coal-fired power plant. The variations of hyperparameters of LSTM, GRU, and 1D-CNN were investigated, and the performance metrics such as RMSE and computational time were recorded to obtain optimal hyperparameters. The obtained optimal values of hyperparameters of LSTM, GRU, and 1D-CNN were then employed for models' development, and consequently, the models were tested on test data. The 1D-CNN NOx emission model improved the training efficiency in terms of RMSE by 70.6% and 60.1% compared to LSTM and GRU, respectively. Furthermore, the testing efficiency for 1D-CNN improved by 10.2% and 15.7% compared to LSTM and GRU, respectively. Moreover, 1D-CNN (26 s) reduced the training time by 83.8% and 50% compared to LSTM (160 s) and GRU (52 s), respectively. Results reveal that 1D-CNN is more accurate, more stable, and computationally inexpensive compared to LSTM and GRU on NOx emission data from the 500 MW power plant.
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| 13. |
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| 14. |
- Wang, Hongdi, et al.
(författare)
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Vessel Failure Analysis of a Boiling Water Reactor During a Severe Accident
- 2022
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Ingår i: Frontiers in Energy Research. - : Frontiers Media SA. - 2296-598X. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- In a postulated severe accident, the thermo-mechanical loads from the corium debris that has relocated to the lower head of the reactor pressure vessel (RPV) can pose a credible threat to the RPV's structural integrity. In case of a vessel breach, it is vital to predict the mode and timing of the vessel failure. This affects the ex-vessel accident progression and plays a critical role in the development of mitigation strategies. We propose a methodology to assess RPV failure based on MELCOR and ANSYS Mechanical APDL simulations. A Nordic-type boiling water reactor (BWR) is considered with two severe accident scenarios: i) SBO (Station Blackout) and ii) SBO + LOCA (Loss of Coolant Accident). In addition, the approach considers the dynamic ablation of the vessel wall due to a high-temperature debris bed with the use of the element kill function in ANSYS. The results indicate that the stress failure mechanism is the major cause of the RPV failure, compared to the strain failure mechanism. Moreover, the axial normal stress and circumferential normal stress make the dominant contributions to the equivalent stress sigma at the lower head of RPVs. As expected, the region with high ablation is most likely the failure location in both SBO and SBO + LOCA. In addition, comparisons of the failure mode and timing between SBO and SBO + LOCA are described in detail. A short discussion on RPV failure between ANSYS and MELCOR is also presented.
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| 15. |
- Yang, Jiawang, et al.
(författare)
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Review on Thermal Performance of Nanofluids With and Without Magnetic Fields in Heat Exchange Devices
- 2022
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Ingår i: Frontiers in Energy Research. - : Frontiers Media SA. - 2296-598X. ; 10
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Forskningsöversikt (refereegranskat)abstract
- Addition of nanoparticles into a fluid can improve the heat transfer performance of the base fluid in heat exchangers. In this work, the preparation method and process of nanofluids are introduced, and thermal properties of nanofluids, such as thermal conductivity and viscosity, are discussed deeply. This paper summarizes various theoretical models of thermal conductivity and viscosity of nanofluids. A comprehensive literature survey on applications and limitations of nanofluids has been compiled. This paper also aims to review the natural and forced convective heat transfer characteristics of nanofluids with and without magnetic fields. The discussion for the natural convective heat transfer of nanofluids focuses on the heat transfer performance of non-conventional enclosures and electric heaters. The effects on heat transfer due to variations of heated walls are also investigated. Specific applications of nanofluids in a tube with trapezoidal ribs, double-tube heat exchangers, and plate heat exchangers have been reviewed and presented in a discussion about forced convective heat transfer. The previous results show that the inlet temperature of nanofluids obviously affects the heat transfer characteristics of double-tube heat exchangers, whereas a multi-walled carbon nanotube–water nanofluid shows significant advantages in plate heat exchangers. Finally, this paper studies natural convective heat transfer of magnetic fluids in a square cavity and forced convection heat transfer in a straight tube and a corrugated structure under the action of magnetic fields. It is found that the heat transfer performance of an Fe3O4–water nanofluid is enhanced when a magnetic field is applied to the corrugated plate heat exchangers, and the pressure drop can be reduced by around 10%. It is recommended that natural convection of magnetic fluids needs to be investigated experimentally in a real cavity and a corrugated channel under the influence of a magnetic field. In addition, studies of alternating magnetic field are recommended to reveal any improvements of thermal performance of magnetic fluids in heat exchange devices. This review puts forward an effective solution for improvement of the thermal performance of heat transfer equipment and serves as a basic reference for applications of nanofluids in heat transfer fields.
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| 16. |
- Zhang, Li, et al.
(författare)
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Numerical simulation of natural convection and heat transfer in a molten pool with embedded cooling tubes
- 2022
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Ingår i: Frontiers in Energy Research. - : Frontiers Media SA. - 2296-598X. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- This study described the natural circulation and heat transfer of a molten pool in a specifically designed core catcher conceived for a pressurized water reactor. In addition to external cooling, the core catcher features internal cooling tubes embedded in the molten pool. To investigate the coolability in such a configuration, first, a full-scale core catcher simulation is conducted to give a preliminary study under a real SA situation. Results illustrated that cooling efficiency can be remarkably enhanced due to the inner tubes. Then a test facility of the 2D slice with the geometrical scaled factor of 1:4 has been developed, and molten salt (NaNO3-KNO3) experiments will be implemented in the near future. This study also performed a pre-test simulation using molten NaNO3-KNO3 as a stimulant to study the heat transfer and flow characteristics of the salt pool. The melt convection in the test section was represented by a two-dimensional mesh with a WMLES turbulence model using the FLUENT code. The simulation captured the heat transfer enhancement by the cooling tubes as expected, and the results would help decide the proper test matrix and improvement of instrumentation required to obtain the necessary data for code validation.
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| 17. |
- Zlotea, Claudia, et al.
(författare)
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Compositional effects on the hydrogen storage properties in a series of refractory high entropy alloys
- 2022
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Ingår i: Frontiers in Energy Research. - : Frontiers Media S.A.. - 2296-598X. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- The possible combinations in the multidimensional space of high entropy alloys are extremely broad, which makes the incremental experimental research limited. As a result, establishing trends with well-known empirical parameters (lattice distortion, valence electron concentration etc.) and predicting effects of the chemical composition change are vital to guide future research in the field of materials science. In this context, we propose a strategy to rationalize the effect of chemical composition change on the hydrogen sorption properties in a series of high entropy alloys: Ti0.30V0.25Zr0.10Nb0.25 M (0.10) with M = Mg, Al, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, Ta and null (corresponding quaternary alloy). All materials are bcc alloys and absorb hydrogen at room temperature forming fcc or pseudo-fcc dihydride phases. The maximum hydrogen storage capacity at room temperature strongly depends on the valence electron concentration (VEC) of the alloys: the capacity is high (1.5-2.0 H/M) for low values of VEC (< 4.9) whereas, a drastic fading is observed for VEC & GE;4.9 which is the case for alloys with M being a late 3d transition metal. The structural analysis suggests that steric effects might not be responsible for this trend and electronic reasons may be invoked. Increasing the VEC by alloying with late 3d transition metals will fill the unoccupied valence states and the electrons from interstitial hydrogens can no longer be accommodated, which is unfavorable for hydrogen storage. Moreover, the onset temperature of desorption increases almost linearly with VEC for this composition series. These findings suggest that alloys with low VEC are more likely to become promising candidates for hydrogen storage.
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