Letteratura scientifica selezionata sul tema "Super calendered paper (SC)"
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Articoli di riviste sul tema "Super calendered paper (SC)"
1
Gorski, Dmitri, e Jan Hill. "Improved quality of SC magazine paper through enhanced fibre development using the ATMP process". Nordic Pulp & Paper Research Journal 27, n. 1 (1 gennaio 2012): 35–41. http://dx.doi.org/10.3183/npprj-2012-27-01-p035-041.
Testo completoAbstract (sommario):
Abstract A pilot scale refining trial was conducted using the ATMP (Advanced Thermomechanical Pulp) refining concept with White spruce as raw material. Low-intensity TMP and high-intensity TMP with mechanical pretreatment of chips were compared to ATMP (Mg+P), where development of fibres was enhanced using hydrogen peroxide and magnesium hydroxide. The main goal of the trial was to evaluate the potential of using ATMP process for production of SC (supercalendered) magazine paper. SC paper is especially demanding when it comes to the paper surface structure which is strongly influenced by the development of fibre properties. Improvement in individual fibre properties such as flexibility, fibre split index and fibre surface area index achieved using ATMP process was found to translate into decreased surface roughness and air permeability of calendered laboratory sheets. Both the refining process configuration and the addition of process chemicals were found to have significant impacts though the process configuration had major role. The influence of process chemicals on surface roughness was mainly pronounced after second stage refining. The magnitude of surface roughening (fibre rising) was found to be influenced mainly by the process configuration.
2
Bogatov, S. A., D. V. Kryuchkov, D. I. Pavlov e D. V. Sychenko. "Analysis of Various Concepts for RW Class 1 Disposal in Crystalline Rocks". Radioactive Waste 12, n. 3 (2020): 66–77. http://dx.doi.org/10.25283/2587-9707-2020-3-66-77.
Testo completoAbstract (sommario):
The paper considers most elaborated concepts for SNF and HLW disposal in crystalline rocks. It explores in detail an alternative concept suggesting the use of a super-container (SC) with a bentonite buffer located inside a steel body and the SC itself located in vertical wells inside a cement backfill, which is also used to seal fractures crossing the wells.
3
Xie, Congzhen, Jigang Wang, Bing Luo, Xiaolin Li e Lei Ja. "A control strategy for battery/supercapacitor hybrid energy storage system". Journal of Physics: Conference Series 2108, n. 1 (1 novembre 2021): 012091. http://dx.doi.org/10.1088/1742-6596/2108/1/012091.
Testo completoAbstract (sommario):
Abstract In DC microgrid (MG), the hybrid energy storage system (HESS) of battery and supercapacitor (SC) has the important function of buffering power impact, which comes from renewable energy sources (RES) and loads. This paper proposes a HESS control strategy with DC bus voltage self-recovery function. High and low frequency power decomposition based on virtual droop control, and DC bus drop voltage is compensated by added proportional integral regulation. The relationship between DC bus voltage recovery and super-capacitor (SC) state of charge (SoC) recovery is analyzed. The system can realize stable energy storage, supply under frequent load power impact. The effectiveness of the proposed control strategy is verified by simulation in MATLAB/Simulink.
4
Dimitriadis, Georgios, Ryan J. Foley, Nikki Arendse, David A. Coulter, Wynn V. Jacobson-Galán, Matthew R. Siebert, Luca Izzo et al. "A Carbon/Oxygen-dominated Atmosphere Days after Explosion for the “Super-Chandrasekhar” Type Ia SN 2020esm". Astrophysical Journal 927, n. 1 (1 marzo 2022): 78. http://dx.doi.org/10.3847/1538-4357/ac4780.
Testo completoAbstract (sommario):
Abstract Seeing pristine material from the donor star in a type Ia supernova (SN Ia) explosion can reveal the nature of the binary system. In this paper, we present photometric and spectroscopic observations of SN 2020esm, one of the best-studied SNe of the class of “super-Chandrasekhar” SNe Ia (SC SNe Ia), with data obtained −12 to +360 days relative to peak brightness, obtained from a variety of ground- and space-based telescopes. Initially misclassified as a type II supernova, SN 2020esm peaked at M B = −19.9 mag, declined slowly (Δm 15(B) = 0.92 mag), and had particularly blue UV and optical colors at early times. Photometrically and spectroscopically, SN 2020esm evolved similarly to other SC SNe Ia, showing the usual low ejecta velocities, weak intermediate-mass elements, and the enhanced fading at late times, but its early spectra are unique. Our first few spectra (corresponding to a phase of ≳10 days before peak) reveal a nearly pure carbon/oxygen atmosphere during the first days after explosion. This composition can only be produced by pristine material, relatively unaffected by nuclear burning. The lack of H and He may further indicate that SN 2020esm is the outcome of the merger of two carbon/oxygen white dwarfs. Modeling its bolometric light curve, we find an 56Ni mass of 1.23 − 0.14 + 0.14 M ☉ and an ejecta mass of 1.75 − 0.20 + 0.32 M ☉, in excess of the Chandrasekhar mass. Finally, we discuss possible progenitor systems and explosion mechanisms of SN 2020esm and, in general, the SC SNe Ia class.
5
Tang, Bin, Di Zhang, Haobin Jiang e Yinqiu Huang. "Optimization of Energy Management Strategy for the EPS with Hybrid Power Supply Based on PSO Algorithm". Energies 13, n. 2 (16 gennaio 2020): 428. http://dx.doi.org/10.3390/en13020428.
Testo completoAbstract (sommario):
The traditional vehicle power supply is unable to meet the power requirement of electric power steering system (EPS) in heavy-duty vehicles at low speeds. A novel EPS with hybrid power supply (HP-EPS) is constructed in this paper, and a new optimized rule-based energy management strategy of hybrid power supply system is designed. The strategy determines the power distribution of the vehicle power supply (VPS) and super capacitor (SC), as well as the charging or discharging of SC. Furthermore, to minimize the output current fluctuation of the VPS, the optimization model of parameters in the strategy is established and the particle swarm optimization algorithm (PSO) algorithm is applied to optimize the rules in the energy management strategy. The verification for the designed energy management strategy is carried out in MATLAB/Simulink and results show that the output current peak of VPS decreases by 33% and its fluctuation depresses significantly. In addition, the SC is charged timely and fast, which is beneficial to guarantee enough state of charge (SOC) of SC. In conclusion, the optimized rule-based energy management strategy used for the HP-EPS system can meet the current requirement of EPS and effectively reduce the peak and fluctuation of the VPS output current.
6
Song, Y. D., Qian Cao, Xiaoqiang Du e Hamid Reza Karimi. "Control Strategy Based on Wavelet Transform and Neural Network for Hybrid Power System". Journal of Applied Mathematics 2013 (2013): 1–8. http://dx.doi.org/10.1155/2013/375840.
Testo completoAbstract (sommario):
This paper deals with an energy management of a hybrid power generation system. The proposed control strategy for the energy management is based on the combination of wavelet transform and neural network arithmetic. The hybrid system in this paper consists of an emulated wind turbine generator, PV panels, DC and AC loads, lithium ion battery, and super capacitor, which are all connected on a DC bus with unified DC voltage. The control strategy is responsible for compensating the difference between the generated power from the wind and solar generators and the demanded power by the loads. Wavelet transform decomposes the power difference into smoothed component and fast fluctuated component. In consideration of battery protection, the neural network is introduced to calculate the reference power of battery. Super capacitor (SC) is controlled to regulate the DC bus voltage. The model of the hybrid system is developed in detail under Matlab/Simulink software environment.
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Häkkänen, H. J., e J. E. I. Korppi-Tommola. "Laser-Induced Fluorescence Imaging of Paper Surfaces". Applied Spectroscopy 47, n. 12 (dicembre 1993): 2122–25. http://dx.doi.org/10.1366/0003702934066307.
Testo completoAbstract (sommario):
Laser-induced fluorescence imaging has been used to study the microstructure of paper surfaces. Pulses from a XeCl-excimer laser, 10 ns in duration at 308 nm, were used for excitation, and fluorescence was collected at 420 nm. The excitation spot diameter was approximately 20 µm, and the sampling interval 0.15 mm. Within an area of 5*5 mm2, 1023 sampling points were recorded to generate 3D fluorescence maps of paper surfaces. Papers containing fluorescence whitening agents (FWAs) gave the highest average fluorescence signals. Coated papers with no FW As show weaker signals than the base sheet. For some thirty different paper samples, an obvious correlation between the amount of coating and the average intensity of the fluorescence signal was observed. Signal fluctuations around the average intensity values were sensitive to (1) the chemical pulp content in super calantered (SC) paper, (2) the amount of recycled fiber in newsprint, and (3) the amount of coating on the light-weight coated (LWC) paper surface. An effort was made to correlate fluorescence imaging results to predict mottling (diffusion of printing ink after printing) in various paper brands.
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Yang, Yintang, Yingbo Zhao e Gang Dong. "A Multi-Output on-Chip Switched-Capacitor DC–DC Converter with Unequal Flying Capacitors for Different Power Modes". Journal of Circuits, Systems and Computers 24, n. 04 (4 marzo 2015): 1550051. http://dx.doi.org/10.1142/s0218126615500516.
Testo completoAbstract (sommario):
This paper presents a multi-output on-chip switched-capacitor (SC) DC–DC converter simultaneously providing two output voltages (2VDD/3 and VDD/3, in addition to the available full VDD) that enables the use of three different power modes for optimizing system power/performance trade-offs: super-threshold (full VDD), near-threshold (2VDD/3) and sub-threshold (VDD/3). Unlike some previously proposed multi-output SC converters, the multiple conversion ratios of the proposed converter are achieved without changing the topology of the circuit, thus fewer components being needed to support multiple voltages. The paper also presents an optimization method by using unequal flying capacitors for different regions of the circuit by taking advantage of the different levels of expected power consumption in the various power modes. Above 84% and 70% efficiencies are obtained in simulation over a range of load currents from 0.4 to 5 mA, and from 0.4 to 1 mA, with conversion ratios of 2/3 and 1/3, respectively. The target application for the proposed converter is for circuits with discrete power modes and for systems that use dithering to emulate a continuous range of voltages such as the panoptic dynamic voltage scaling (PDVS).
9
Xin, Jingwei, Nannan Wang, Xinrui Jiang, Jie Li, Xinbo Gao e Zhifeng Li. "Facial Attribute Capsules for Noise Face Super Resolution". Proceedings of the AAAI Conference on Artificial Intelligence 34, n. 07 (3 aprile 2020): 12476–83. http://dx.doi.org/10.1609/aaai.v34i07.6935.
Testo completoAbstract (sommario):
Existing face super-resolution (SR) methods mainly assume the input image to be noise-free. Their performance degrades drastically when applied to real-world scenarios where the input image is always contaminated by noise. In this paper, we propose a Facial Attribute Capsules Network (FACN) to deal with the problem of high-scale super-resolution of noisy face image. Capsule is a group of neurons whose activity vector models different properties of the same entity. Inspired by the concept of capsule, we propose an integrated representation model of facial information, which named Facial Attribute Capsule (FAC). In the SR processing, we first generated a group of FACs from the input LR face, and then reconstructed the HR face from this group of FACs. Aiming to effectively improve the robustness of FAC to noise, we generate FAC in semantic, probabilistic and facial attributes manners by means of integrated learning strategy. Each FAC can be divided into two sub-capsules: Semantic Capsule (SC) and Probabilistic Capsule (PC). Them describe an explicit facial attribute in detail from two aspects of semantic representation and probability distribution. The group of FACs model an image as a combination of facial attribute information in the semantic space and probabilistic space by an attribute-disentangling way. The diverse FACs could better combine the face prior information to generate the face images with fine-grained semantic attributes. Extensive benchmark experiments show that our method achieves superior hallucination results and outperforms state-of-the-art for very low resolution (LR) noise face image super resolution.
10
Kumar, G. V. Brahmendra, Palanisamy Kaliannan, Sanjeevikumar Padmanaban, Jens Bo Holm-Nielsen e Frede Blaabjerg. "Effective Management System for Solar PV Using Real-Time Data with Hybrid Energy Storage System". Applied Sciences 10, n. 3 (7 febbraio 2020): 1108. http://dx.doi.org/10.3390/app10031108.
Testo completoAbstract (sommario):
This paper proposes an effective management system for stand-alone solar photovoltaic (PV) using real-time data with Hybrid Energy Storage System (HESS). The abrupt movement of fleeting clouds often gives rise to PV power output fluctuations which in turn affect the power quality and system stability due to scattered solar radiation reception. These variations can limit through a ramp-limit controller and employing a DC link controller to maintain the stable DC link voltage. The battery is used in the system for continuous power application and the sudden variations in charging and discharging of battery power can create stress on the battery. These sudden changes in a battery will be removed by the super-capacitor (SC) unit and achieves a fast DC link voltage regulation. Hence, the high energy and power density devices such as battery and SC units will deliver more stable power into the system. The control scheme is tested in Matlab/Simulink and validated by Real-Time Hardware-in-Loop (HIL) simulator using periodic one-minute data for one year from the solar PV power plant from real-time.
Tesi sul tema "Super calendered paper (SC)"
1
Le, Ny Corinne. "Propriétés des fibres recyclées et leur développement technologique pour la fabrication de papiers magazines super calandrés". Grenoble INPG, 2006. http://www.theses.fr/2006INPG0186.
Testo completoAbstract (sommario):
Les travaux présentés dans cette thèse ont permis de clarifier le potentiel des fibres recyclées (RCF) et les limites rencontrées dans la fabrication de papiers magazines Super Calandrés (SC). La pâte recyclée contribue à améliorer densité d'impression et homogénéité des aplats en héliogravure mais tend à détériorer diffusion de la lumière, transvision, marbrage et points manquants. L'origine des différences observées entre les papiers à base de RCF et ceux à base de fibres vierges a été étudiée en simulant les effets de la composition fibreuse, du recyclage et du raffinage sur la qualité des papiers SC. Le taux de fibres chimiques s'est révélé être un paramètre influençant la plupart des caractéristiques des SC, dont transvision et marbrage. Par contre le taux de fibres mécaniques à paroi cellulaire épaisse a un effet marginal sur la qualité des papiers SC. La tendance vers une augmentation des points manquants lorsqu'un papier SC à taux élevé de pâte recyclée est imprimé en héliogravure a partiellement pour origine le raffinage de la RCF à haut niveau d'énergie spécifiqueBased on industrial experience of UPM mills and advanced pulp and paper analysis, this thesis has aimed to clarify the potential and limitations of recycled fibres (RCF) for Super Calendered (SC) magazines and recommend future developments in fibre processing technology. RCF is found to improve SC print density and evenness in Rotogravure but tends to deteriorate light scattering, print through, calender blackening and missing dots. The origin of the differences observed between virgin fibre and RCF based SC has been studied by simulating the effects of fibre composition, recycling and refining stages on SC paper quality. Chemical fibres content turns out to be a parameter driving most of SC characteristics, including print through and calender blackening. Conversely, the presence of coarse mechanical fibres within RCF was found to have a marginal effect on SC paper quality. Finally, the trend for more missing dots when printing RCF compared to virgin fibres based SC originates at least partially from high energy RCF refining
2
Johansson, Nils. "Printing colour hard proofs using EFI Colorproof XF v. 3.1 and Photoshop CS3, and production substrates". Thesis, Högskolan Dalarna, Grafisk teknik, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:du-4215.
Testo completoAbstract (sommario):
EFI Colorproof XF was found to be more convenient from a user’s aspect, and had features which are covered in the ISO 12647-7 standard (e.g. the ability to simulate screening and print margin information), which Photoshop CS3 lacked. None of the proofing systems distinguished itself in a clear way from the other; sometimes, on certain substrates, Photoshop CS3 produced most accurate colours, sometimes EFI Colorproof XF did. Further investigations need to be carried out to tell more exactly which system produce most accurate colours. Only 6 out of 34 simulation-combinations had colours within the tolerances in the standard. The result also shows that the production substrates should not be used as proofing substrates. Instead the proofing papers especially made for ink jet should be used to obtain more colour-accurate prints.
Atti di convegni sul tema "Super calendered paper (SC)"
1
Al-Qasim, Abdulaziz S., Sunil Kokal e Fawaz AlOtaibi. "CO2-Foam Rheology Behavior Under Reservoir Conditions". In ASME 2019 38th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/omae2019-95191.
Testo completoAbstract (sommario):
Abstract Super critical carbon dioxide (SC-CO2) flooding is one of the most important enhanced oil recovery (EOR) methods used for conformance control and deep diversion of SC-CO2. It minimizes gravity override of SC-CO2 bypassing oil in the lower part of the formation. This paper investigates the impact of various parameters such as liquid/liquid ratio, different foam qualities and different injection modes on the SC-CO2-foam quality and its rheological properties. SC-CO2 foam can control the SC-CO2 mobility, enhance the sweep efficiency in reservoirs and improve the conformance control. Experimental results shows that combining foam with supercritical and dense CO2 will reduce the mobility of SC-CO2 to oil and water, stabilize the SC-CO2 injection front and mitigate the gravity override to a great extent resulting in less amount of unwept oil and better displacement efficiency and more recovery gain. Different set of lab experiments designed and conducted to identify the right ratio that can drastically increase SC-CO2 viscosity. In this work, we explored the rheological properties of SC-CO2 foam/gel chemicals with different pressure and temperature. Two different types of surfactants were tested. The experimental setup and conditions were designed to allow surfactant to mix with SC-CO2 under high reservoir pressure and temperature (HPHT) to create foam to evaluate and screen the foam quality and texture. The rheological properties of the SC-CO2-foam were investigated by varying the shear rate, shear stress, foam quality, injection modes and foaming agent concentrations at reservoir conditions. The effects of foam quality and liquid/liquid ratio, pressure and temperature on SC-CO2-foam at synthetic brine-environment rheology behavior, stability and mobility of foam were investigated. The foam study experiments were conducted using different scenarios: once by injecting SC-CO2 and surfactant solutions simultaneously and another time by alternate injection of CO2/surfactant solution at different flow rates at different foam qualities. The experimental results have shown that the foam mobility (total mobility of CO2 /surfactant solution) decreased with increasing foam quality ranging from 20% to 80%. The rheological properties of N2-foam were investigated and compared with SC-CO2-foam properties. This was correlated with the images of the high pressure, high temperature (HPHT) foams that were captured through microscope at different time intervals and analyzed to indicate their stability.
2
Dragunov, Alexey, Eugene Saltanov, Sergey Bedenko e Igor Pioro. "A Feasibility Study on Various Power-Conversion Cycles for a Sodium-Cooled Fast Reactor". In 2012 20th International Conference on Nuclear Engineering and the ASME 2012 Power Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/icone20-power2012-55130.
Testo completoAbstract (sommario):
One of the current engineering challenges is to design next generation (Generation IV) Nuclear Power Plants (NPPs) with significantly higher thermal efficiencies compared to those of current NPPs to match or at least to be close to thermal efficiencies reached at thermal power plants (43–55%). A Sodium-cooled Fast Reactor (SFR) is one of six concepts considered under the Generation IV International Forum (GIF). This concept is the only one from the Generation IV reactors, which is actually in operation in Russia. In general, there are 3 possibilities for an SFR in terms of the secondary cycle: 1. Subcritical-pressure Rankine-“steam”-cycle through a heat exchanger (current approach used in Russian and Japanese power reactors). 2. Supercritical-pressure Rankine-“steam”-cycle through a heat exchanger (new approach). 3. Supercritical-pressure CO2 Brayton-gas-turbine-cycle through a heat exchanger (US approach). The BN-600 reactor is a sodium-cooled fast-breeder reactor built at the Beloyarsk NPP in Russia. It has been in operation since 1980 and adopts the secondary subcritical-pressure Rankine-“steam”-cycle with heat regeneration. Steam extractions are taken from High-Pressure (HP), Intermediate-Pressure (IP) and Low-Pressure (LP) turbines. The basic method of increasing the thermal efficiency of power plants is to improve it by increasing the operating pressure and temperature. With the advent of modern super alloys, the Rankine-“steam”-cycle has progressed into the supercritical region of the coolant and is generating net efficiencies into the mid 40% range. Calculations of thermal efficiency of a secondary sub- and supercritical-pressure Rankine-“steam”-cycle with heat regeneration are presented in the paper. The Brayton-gas-turbine cycle is under consideration for future nuclear power reactors. The higher operating temperatures will be achieved, the higher thermal efficiency will be. Supercritical CO2 cycle is a new approach in Brayton-gas-turbine cycle. Carbon dioxide has a critical pressure of 7.38 MPa and a critical temperature of 31.0°C, which is significantly less than that of water (22.064 MPa and 373.95°C). However, liquid sodium is more compatible with SC CO2 than with water. Therefore, thermal efficiency of this SC CO2 cycle is also calculated.
3
Shang, Ziduan, Chunhua Wu, Boyu Han, Chenyu Chang e Lutong Zhang. "Nuclear Island Basemat Modeling for Generation III Nuclear Power Plant Design in China". In 2017 25th International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/icone25-66346.
Testo completoAbstract (sommario):
Nuclear Island (NI) basemat is a very thick reinforced concrete mat sitting on sub-grade soil to function as one-piece-foundation to support all super-structures anchored above the basemat. The Generation III (GEN III) NI is designed with more structures housing on the basemat, as such it is even greater in dimensions compared to GEN II. In the design process of a GEN III Passive-Safety-Plant (PSP), NI base mat is the most critical part for foundation design, since it is not only serves as the pressure boundary in foundation system but also support the whole nuclear island, carrying vertical load from upper structures, seismic loads both in vertical and horizontal directions, lateral soil pressures and buoyant force due to water table etc. For a typical AP plant the main structural systems which are housing within NI comprises of steel containment vessel (SCV), shield building (SC wall), internal structures, and auxiliary buildings etc. The scope for this paper is to investigate the approach and method which are suitable for modeling GEN III passive-safety-plant basemat. The investigation scopes are focused on (1) concrete basemat FE modeling and related subgrade medium (soil) modeling; (2) Design loads evaluation method and application for a typical basemat FE static analysis. Structurally speaking SCV is designed to directly anchored in concrete basemat, the interface between upper structure and foundation, its geometry and connection are unique and complicated, this lead to the modeling of basemat not only have to consider an appropriate FE meshing and element type selection but also need to consider the load application and transferring from the SCV to the basemat basin. Since passive-safety-plant NI basemat is a deep foundation, basemat is deeply buried below the grade, the complete foundation model not only shall consider the basemat and immediate soil under the basemat, but also need to consider the backfill soil, the surrounding soil in vicinity, fill concrete under the basemat and deeper soil condition under the basemat. Since seismic loads pose great effects on basemat and its foundation design, how to evaluation seismic loadings and simplified their application for basemat static analysis is critical for such type of foundation.
4
Dragunov, Alexey, Eugene Saltanov, Igor Pioro, Glenn Harvel e Brian Ikeda. "Study on Primary and Secondary Heat-Transport Systems for Sodium-Cooled Fast Reactor". In 2013 21st International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/icone21-16014.
Testo completoAbstract (sommario):
One of the current engineering challenges is to design next generation (Generation IV) Nuclear Power Plants (NPPs) with significantly higher thermal efficiencies (43–55%) compared to those of current NPPs to match or at least to be close to the thermal efficiencies reached at fossil-fired power plants (55–62%). The Sodium-cooled Fast Reactor (SFR) is one of the six concepts considered under the Generation IV International Forum (GIF) initiative. The BN-600 reactor is a sodium-cooled fast-breeder reactor built at the Beloyarsk NPP in Russia. This concept is the only one from the Generation IV nuclear-power reactors, which is actually in operation (since 1980’s). At the secondary side, it uses a subcritical-pressure Rankine-steam cycle with heat regeneration. The reactor generates electrical power in the amount of 600 MWel. The reactor core dimensions are 0.75 m (height) by 2.06 m (diameter). The UO2 fuel enriched to 17–26% is utilized in the core. There are 2 loops (circuits) for sodium flow. For safety reasons, sodium is used both in the primary and the intermediate circuits. Therefore, a sodium-to-sodium heat exchanger is used to transfer heat from the primary loop to the intermediate one. In this work major parameters of the reactor are listed. The actual scheme of the power-conversion heat-transport system is presented; and the results of the calculation of thermal efficiency of this scheme are analyzed. Details of the heat-transport system, including parameters of the sodium-to-sodium heat exchanger and main coolant pump, are presented. In this paper two possibilities for the SFR in terms of the power-conversion cycle are investigated: 1. a subcritical-pressure Rankine-steam cycle through a heat exchanger (current approach in Russian and Japanese power reactors); 2. a supercritical-pressure CO2 Brayton gas-turbine cycle through a heat exchanger (US approach). With the advent of modern super-alloys, the Rankine-steam cycle has progressed into the supercritical region of the coolant and is generating thermal efficiencies into the mid 50% range. Therefore, the thermal efficiency of a supercritical Rankine-steam cycle is also briefly discussed in this paper. According to GIF, the Brayton gas-turbine cycle is under consideration for future nuclear power reactors. The supercritical-CO2 cycle is a new approach in the Brayton gas-turbine cycle. Therefore, dependence of the thermal efficiency of this SC CO2 cycle on inlet parameters of the gas turbine is also investigated.
5
Naidin, M. C., I. Pioro, U. Zirn e K. Chophla. "SuperCritical-Water Reactor NPP Concept: No-Reheat Cycle Option". In 17th International Conference on Nuclear Engineering. ASMEDC, 2009. http://dx.doi.org/10.1115/icone17-75989.
Testo completoAbstract (sommario):
Research activities are currently conducted worldwide to develop Generation IV nuclear reactor concepts with the objective of improving thermal efficiency and increasing economic competitiveness of Generation IV Nuclear Power Plants (NPPs) compared to modern thermal power plants. The Super-Critical Water-cooled Reactor (SCWR) concept is one of the six Generation IV options chosen for further investigation and development in several countries including Canada and Russia. Water-cooled reactors operating at subcritical pressures (10 – 16 MPa) have provided a significant amount of electricity production for the past 50 years. However, the thermal efficiency of the current NPPs is not very high (30–35%). As such, more competitive designs, with higher thermal efficiencies, which will be close to that of modern thermal power plants (45 – 50%), need to be developed and implemented. Previous studies have shown that direct cycles, with no-reheat and single-reheat configurations are the best choice for the SCWR concept. However, the single-reheat cycle requires a nuclear steam-reheat, thus increasing the complexity of the reactor core design. Although preliminary results show that the thermal efficiency of the no-reheat cycle is approximately 2% lower than that of the single-reheat cycle, the less complex core configuration may prove to be a major factor when selecting the most suitable design. This paper investigates the main parameters and performance in terms of thermal efficiency of a SCW NPP based on a no-reheat, direct cycle with heat regeneration. When compared to the single-reheat cycle, the no-reheat configuration has a more simplified design: the Intermediate-Pressure (IP) turbine section is eliminated and the exhaust from the High-Pressure (HP) turbine is directly routed to the inlet of the Low-Pressure (LP) turbines. The cycle also consists of a condenser, nine feedwater heaters, a topping de-superheater, associated pumps, and the nuclear source of energy, i.e., the SCWR. In general, the major technical challenge associated with a SC no-reheat turbine is the high moisture content in the LP turbine exhaust. A thermal-performance simulation reveals that the steam quality at the exhaust from the LP turbine is approximately 81%. However, the moisture can be reduced by implementation of contoured channels in the inner casing for draining water and moisture removal stages. The overall thermal efficiency of the cycle was determined to be about 50% (assumptions are made to account for turbine and pump efficiency losses). Furthermore, important safety parameters such as bulk-fluid temperature, sheath temperature and fuel-centerline temperature are calculated for a non-uniform cosine Axial Heat Flux Profile (AHFP) along a generic fuel channel of the no-reheat SCWR concept.