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Guilley, Sylvain, Florent Flament, Philippe Hoogvorst, Renaud Pacalet y Yves Mathieu. "Secured CAD Back-End Flow for Power-Analysis-Resistant Cryptoprocessors". IEEE Design & Test of Computers 24, n.º 6 (noviembre de 2007): 546–55. http://dx.doi.org/10.1109/mdt.2007.202.
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Guilley, Sylvain, Florent Flament, Philippe Hoogvorst, Renaud Pacalet y Yves Matheiu. "Secured CAD back-end flow for power-analysis resistant cryptoprocessors". IEEE Design & Test of Computers 24, n.º 99 (2007): x2. http://dx.doi.org/10.1109/mdt.2007.4343579.
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Ehrich, F. F., Z. S. Spakovszky, M. Martinez-Sanchez, S. J. Song, D. C. Wisler, A. F. Storace, H. W. Shin y B. F. Beacher. "Unsteady Flow and Whirl-Inducing Forces in Axial-Flow Compressors: Part II—Analysis". Journal of Turbomachinery 123, n.º 3 (1 de febrero de 2000): 446–52. http://dx.doi.org/10.1115/1.1370165.
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An experimental and theoretical investigation was conducted to evaluate the effects seen in axial-flow compressors when the centerline of the rotor becomes displaced from the centerline of the static structure of the engine, thus creating circumferentially nonuniform rotor-tip clearances. This displacement produces unsteady flow and creates a system of destabilizing forces, which contribute significantly to rotor whirl instability in turbomachinery. These forces were first identified by Thomas (1958. Bull. AIM, 71, No. 11/12, pp. 1039–1063.) for turbines and by Alford (1965. J. Eng. Power, Oct., pp. 333–334) for jet engines. In Part I, the results from an experimental investigation of these phenomena were presented. In this Part II, three analytic models were used to predict both the magnitude and direction of the Thomas/Alford force in its normalized form, known as the β coefficient, and the unsteady effects for the compressors tested in Part I. In addition, the effects of a whirling shaft were simulated to evaluate differences between a rotor with static offset and an actual whirling eccentric rotor. The models were also used to assess the influence of the nonaxisymmetric static pressure distribution on the rotor spool, which was not measured in the experiment. The models evaluated were (1) the two-sector parallel compressor (2SPC) model, (2) the infinite-segment-parallel-compressor (ISPC) model, and (3) the two-coupled actuator disk (2CAD) model. The results of these analyses were found to be in agreement with the experimental data in both sign and trend. Thus, the validated models provide a general means to predict the aerodynamic destabilizing forces for axial flow compressors in turbine engines. These tools have the potential to improve the design of rotordynamically stable turbomachinery.
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Guo, Ling, Yue Sun, Ling Liu, Zhixi Shen, Ruizhen Gao y Kai Zhao. "The Flow Field Analysis and Flow Calculation of Ultrasonic Flowmeter Based on the Fluent Software". Abstract and Applied Analysis 2014 (2014): 1–8. http://dx.doi.org/10.1155/2014/528602.
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We can build the three-dimensional structure model based on the Gambit software and achieve the distribution of flow field in the pipe and reflux flow condition at the position of transducer in regard to the real position of transducer according to the Fluent software. Under the framework, define the reflux length based on the distance of reflux along the channel and evaluate the effect of reflux on flow field. Then we can correct the power factor with the transmission speed difference method in the ideal condition and obtain the matching expression of power correction factor according to the practice model. In the end, analyze the simulation experience and produce the sample table based on the proposed model. The comparative analysis of test results and simulation results demonstrates the validity and feasibility of the proposed simulation method. The research in this paper will lay a foundation for further study on the optimization of ultrasonic flowmeter, enhance the measurement precision, and extend the application of engineering.
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Qu, Ouyang, Yuan y Zeng. "Steady-State Power Flow Analysis of Cold-Thermal-Electric Integrated Energy System Based on Unified Power Flow Model". Energies 12, n.º 23 (22 de noviembre de 2019): 4455. http://dx.doi.org/10.3390/en12234455.
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The integrated energy system includes various energy forms, complex operation modes and tight coupling links, which bring challenges to its steady-state modeling and steady-state power flow calculation. In order to study the steady-state characteristics of the integrated energy system, the topological structure of the cold-thermal-electric integrated energy system is given firstly. Then, the steady-state model of the power subsystem, the thermal subsystem, the cold subsystem and the distributed energy station are established, the unified power flow model is established, and the Newton Raphson algorithm is used to solve the unified power flow model. Finally, the influence of the key technical parameters on the steady-state power flow of the integrated energy system is analyzed. Research results show that the photovoltaic power generation plays a supporting role in the voltage of each bus; with the increase of electric load power, the unit value of bus voltage decreases continuously; the water supply temperature of the source node has a greater impact on the steady-state flow in the pipeline and the water supply temperature of each node; the pipeline length of the heat network has a greater impact on the end temperature of the pipeline, the water supply temperature, and the return water temperature of each node. The analysis results can support the planning, design, and optimal operation of the integrated energy system.
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Wirasanti, Paramet y Egon Ortjohann. "Active Distribution Grid Power Flow Analysis using Asymmetrical Hybrid Technique". International Journal of Electrical and Computer Engineering (IJECE) 7, n.º 4 (1 de agosto de 2017): 1738. http://dx.doi.org/10.11591/ijece.v7i4.pp1738-1748.
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A conventional distribution power flow analysis has to be improved regards the changes in distribution network. One of the changes is a grid operation because a new grid concept, e.g. micro-grid and aggregation, is aimed to be operated based on area itself. Consequently, each area can be actively operated in either grid connected mode or islanding mode. Hence, this paper proposes an asymmetrical power flow analysis using hybrid technique to support this flexible mode change. The hybrid technique offers an opportunity to analyze power flow in a decoupling way. This means that the power flow analysis can be performed separately in each grid area. Regards the distributed generation, this paper also introduces a model based on inverter-based operation, i.e. grid forming, grid supporting and grid parallel. The proposed asymmetrical hybrid load flow method is examined in three case studies, i.e. a verification study with the DIgSILENT PowerFactory, a demonstration of decoupling analysis approach and a performance study with the Newton-Raphson method.
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Hlaing, Ya Min Su y Ze Ya Aung. "Performance Analysis on Transmission Line for Improvement of Load Flow". Advanced Materials Research 433-440 (enero de 2012): 7208–12. http://dx.doi.org/10.4028/www.scientific.net/amr.433-440.7208.
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This thesis implements power flow application, Newton-Raphson method. The Newton-Raphson method is mainly employed in the solution of power flow problems. The network of Myanma electric power system is used as the reference case. The system network contains 90 buses and 106 brunches. The weak points are found in the network by using Newton-Raphson method. Bus 16, 17, 85 and 86 have the most weak bus voltages. The medium transmission line between bus 87 and bus 17 is compensated by using MATLAB program software. The transmission line is compensated with shunt reactors, series and shunt capacitors to improve transient and steady-state stability, more economical loading, and minimum voltage dip on load buses and to supply the requisite reactive power to maintain the receiving end voltage at a satisfactory level. The system performance is tested under steady-state condition. This paper investigates and improves the steady–state operation of Myanma Power System Network.
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Obushevs, Artjoms, Mario Turcik, Irina Oleinikova y Gatis Junghans. "Market Based Analysis of Power System Interconnections". Scientific Journal of Riga Technical University. Power and Electrical Engineering 28, n.º 1 (1 de enero de 2011): 25–30. http://dx.doi.org/10.2478/v10144-011-0004-z.
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Market Based Analysis of Power System InterconnectionsAnalysis in this Article is focused on usage of transmission grid under liberalized market with implicit transmission capacity allocation method, e.g. Nordic market. Attention is paid on fundamental changes in transmission utilization and its economical effective operation. For interconnection and power flow analysis and losses calculation model of Nordic grid was developed and transmission losses calculation method was created. Given approach will improve economical efficiency of system operation in electricity market conditions.
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Saraswathi, Ananthavel y S. Sutha. "Investigation of Modified Generalized Interline Power Flow Controller (GIPFC) and Performance Analysis". Applied Mechanics and Materials 622 (agosto de 2014): 111–20. http://dx.doi.org/10.4028/www.scientific.net/amm.622.111.
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Nowadays in the restructured scenario, the main challenging objective of the modern power system is to avoid blackouts and provide uninterrupted quality power supply with dynamic response during emergency to improve power system security and stability. In this sense the convertible static compensator (CSC) that is the Generalized Inter line power flow controller (GIPFC), can control and optimize power flow in multi-line transmission system instead of controlling single line like its forerunner FACTS (Flexible AC Transmission System) controller. By adding a STATCOM (Static synchronous Shunt Converter) at the front end of the test power system and connecting to the common DC link of the IPFC, it is possible to bring the power factor to higher level and harmonics to the lower level and this arrangement is popularly known as Generalized Inter line power flow controller (GIPFC). In this paper a new concept of GIPFC based on incorporating a voltage source converter with zero sequence injection SPWM technique is presented for reinforcement of system stability margin. A detailed circuit model of modified GIPFC is developed and its performance is validated for a standard test system. Simulation is done using MATLAB Simulink.Index Terms—Convertible static controller, Flexible AC Transmission System (FACTS), Generalized Interline Power Flow Controller (GIPFC),STATCOM, SSSC, Reactive power compensation.
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Imen, Labed y Labed Djamel. "Power flow variation based on extreme learning machine algorithm in power system". International Journal of Power Electronics and Drive Systems (IJPEDS) 10, n.º 3 (1 de septiembre de 2019): 1244. http://dx.doi.org/10.11591/ijpeds.v10.i3.pp1244-1254.
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<p>The main focus of this paper is a study that empowers us to understand how the temperature variation affects the transmission line resistance and as a result the power flow analysis with a specific end goal to assess losses in the electrical network. The paper is composed of two sections; the first part is a power flow study under normal conditions utilizing the neural network approach while the second investigated extreme learning machine algorithm efficiency and exactitude. Extreme learning machine algorithm has been used to settle several complications in power system: load forecasting, fault diagnosis, economic dispatch, security, transient stability; Thus, we proposed to study this technique to figure out this sort of complex issue.</p>The study was conducted for IEEE 30 bus test system. The simulation results are exposed and analyzed in detail at the end of this paper.
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Xu, Yan y Jing Zhi. "Fast Search of Dangerous Lines in Power Flow Transferring in Power System". Advanced Materials Research 1070-1072 (diciembre de 2014): 849–54. http://dx.doi.org/10.4028/www.scientific.net/amr.1070-1072.849.
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A method for fast search of dangerous lines in power flow transferring was put forward. Search the equal-phase parallel lines of the overload line by graph theory and voltage phasor angle. Search the shortest path between the end nodes of the overload line which went through the equal-phase parallel lines. The lines on the paths belonged to the power flow transferring line set, where the lines with high active power flow distribution coefficient were dangerous lines in power flow transferring. The method is more targeted in the search for power flow transferring path. It will not leave out dangerous lines for only looking for the shortest line between the two nodes of the overload line, and it wil not select the redundant lines for searching the K shortest paths between the two nodes of the overload line. This method is simple and accurate with little calculation. The method is verified by simulation analysis based on IEEE 39 and IEEE 118 bus system.
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Noureddine, Tebbakh y Labed Djamel. "Load flow analysis using newton raphson method in presence of distributed generation". International Journal of Power Electronics and Drive Systems (IJPEDS) 12, n.º 1 (1 de marzo de 2021): 489. http://dx.doi.org/10.11591/ijpeds.v12.i1.pp489-498.
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<p>Distributed generations (DG), specially including renewable sources such as wind and sun are offering several opportunities for the currently in existence distribution networks and becoming one of the keys of treatment of its problems. Knowing the effects of each kind of DG on distribution networks is a primordial task because DG impacts differ from one kind to another. In this paper, we have analyzed and compared the effects of two kinds of DG, DG which provides real power only and DG which provides real power and reactive power at the same time connected at the critical bus in DN on the voltage profile, real and reactive power losses. We have proposed Newton Raphson method using Matlab to investigate the impacts of these two kinds of DG on 57-bus IEEE distribution test system. The obtained results have been exposed in detail at the end of this paper.</p>
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Park, Jingyeong, Daisuke Kodaira, Kofi Afrifa Agyeman, Taeyoung Jyung y Sekyung Han. "Adaptive Power Flow Prediction Based on Machine Learning". Energies 14, n.º 13 (25 de junio de 2021): 3842. http://dx.doi.org/10.3390/en14133842.
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Power flow analysis is an inevitable methodology in the planning and operation of the power grid. It has been performed for the transmission system, however, along with the penetration of the distributed energy resources, the target has been expanded to the distribution system as well. However, it is not easy to apply the conventional method to the distribution system since the essential information for the power flow analysis, say the impedance and the topology, are not available for the distribution system. To this end, this paper proposes an alternative method based on practically available parameters at the terminal nodes without the precedent information. Since the available information is different between high-voltage and low-voltage systems, we develop two various machine learning schemes. Specifically, the high-voltage model incorporates the slack node voltage, which can be practically obtained at the substation, and yields a time-invariant model. On the other hand, the low voltage model utilizes the deviation of voltages at each node for the power changes, subsequently resulting in a time-varying model. The performance of the suggested models is also verified using numerical simulations. The results are analyzed and compared with another power flow scheme for the distribution system that the authors suggested beforehand.
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Dong, Mingyu, Dezhi Li, Fenkai Chen, Meiyan Wang, Rongjun Chen y Peiliang Liu. "Analysis of Output Characteristics of Typical Distributed Wind Power". E3S Web of Conferences 79 (2019): 03017. http://dx.doi.org/10.1051/e3sconf/20197903017.
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With the development of smart power distribution technology in the future, a large range of power supply load (such as distributed wind power generation) will appear on the power receiving end. When distributed wind power is connected to the power grid on a large scale, it will have a certain impact on the safe and stable operation of the power grid. However, if the wind power output characteristics can be analyzed and the wind power output is properly regulated, the one-way flow of power from the distribution network to the user side will be broken, so that the future "network-load" has dual interaction characteristics based on response and substantial power exchange.
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Amanze, Fortune Chukwuebuka y Amanze Destiny Josiah. "Fault analysis in power system using power systems computer aided design". International Journal of Advances in Applied Sciences 9, n.º 3 (1 de septiembre de 2020): 171. http://dx.doi.org/10.11591/ijaas.v9.i3.pp171-179.
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<span>This work presents a fault analysis simulation model of an IEEE 30 bus system in a distribution network. This work annalysed the effect of fault current and fault voltage in a distribution system. A circuit breaker was introduced into the system to neutralize the effect of the fault. The system was run on a PSCAD software and results were obtained. The system was monitored based on the start time and the end time of the fault and how well the circuit breaker reacts with those times. Fault occurred from 0.100 to 0.300 seconds before it was removed. At the time fault was not applied (i.e. from 0.00 to 0.100 and from 0.300 to 0.72), the circuit breaker was close and became open when fault was applied so as to cut off current flow through the line.The result obtained gave the disruption caused by the fault and the quick response of the circuit breaker in neutralizing it. Results gotten are based on when the circuit breaker is close and no fault is applied and when the circuit breaker is open due to fault. From this work, it was obtained that circuit breakers are very essential in system protection and reliability.</span>
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Wang, Li Quan, Yong Dong An, Rong Hua Sun y Shao Jun An. "Research on Loading Method of High-Speed Closed Power Flow Test System". Key Engineering Materials 419-420 (octubre de 2009): 129–32. http://dx.doi.org/10.4028/www.scientific.net/kem.419-420.129.
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In this paper, a new type of shaft end torque loadling device is studied for the closed power flow test system of the high-power marine reducer, and it illustrates the structure of the load device, makes the principle of analysis and power calculation of the loading device; and analyses the test system power flow conditions and anti-way self-locking of the installation, Finally, the loading devices of the test system is designed to the order of 100000 magnitude reducer, verify the feasibility of this loading method.
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Létal, Tomáš, Vojtěch Turek, Dominika Babička Fialová y Zdeněk Jegla. "Nonlinear Finite Element Analysis-Based Flow Distribution and Heat Transfer Model". Energies 13, n.º 7 (2 de abril de 2020): 1664. http://dx.doi.org/10.3390/en13071664.
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A new strategy for fast, approximate analyses of fluid flow and heat transfer is presented. It is based on Finite Element Analysis (FEA) and is intended for large yet structurally fairly simple heat transfer equipment commonly used in process and power industries (e.g., cross-flow tube bundle heat exchangers), which can be described using sets of interconnected 1-D meshes. The underlying steady-state model couples an FEA-based (linear) predictor step with a nonlinear corrector step, which results in the ability to handle both laminar and turbulent flows. There are no limitations in terms of the allowed temperature range other than those potentially stemming from the usage of fluid physical property computer libraries. Since the fluid flow submodel has already been discussed in the referenced conference paper, the present article focuses on the prediction of the tube side and the shell side temperature fields. A simple cross-flow tube bundle heat exchanger from the literature and a heat recovery hot water boiler in an existing combined heat and power plant, for which stream data are available from its operator, are evaluated to assess the performance of the model. To gain further insight, the results obtained using the model for the heat recovery hot water boiler are also compared to the values yielded by an industry-standard heat transfer equipment design software package. Although the presented strategy is still a “work in progress” and requires thorough validation, the results obtained thus far suggest it may be a promising research direction.
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Yu, Tian Biao, Jia Shun Shi, Xiao Ping Zheng, He Bin Liu y Wan Shan Wang. "Dynamic Characteristics Analysis of Two-Phase Flow Diaphragm Pump Based on MATLAB and ADAMS". Key Engineering Materials 522 (agosto de 2012): 495–502. http://dx.doi.org/10.4028/www.scientific.net/kem.522.495.
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Two-phase flow diaphragm pump (hereafter referred to as the diaphragm pump) is a new generation pump of the reciprocating pump, which used to transport high fretting corrosion medium. At present, the diaphragm pump is widely used in many fields such as Non-ferrous metals, Chemical, Coal, Electric power and so on. The diaphragm pump is of the heart of the equipment; therefore it must have the very high reliability. As the important part of diaphragm pump, the dynamic characteristics of the power end will directly affect the behaviors and life of the solid machine. This paper introduces the work principle of the diaphragm pump, carries a simulation to the virtual prototype of the diaphragm pump based on the numerical value analyze software MATLAB and the dynamics of mechanical system simulation software ADAMS and get the relationships between the design parameters and the dynamic characteristics of the power end of diaphragm pump, which provide a theoretical basis for optimizing the diaphragm pump in the future.
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Yuan, Lei, Zunlong Jin, Penghui Yang, Youchen Yang, Dingbiao Wang y Xiaotang Chen. "Numerical Analysis of the Influence of Different Flow Patterns on Power and Reactant Transmission in Tubular-Shaped PEMFC". Energies 14, n.º 8 (10 de abril de 2021): 2127. http://dx.doi.org/10.3390/en14082127.
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The influence of a tubular structure PEMFC (proton exchange membrane fuel cell) with different flow patterns is investigated in this study. A complete 3D non-isothermal model is constructed for square and circular tubular PEMFCs, and the distribution of oxygen and water concentration in cathode channels, current density, power density and cell net power are studied. To this end, the four arrangements of tubular PEMFC are square chordal (SC), square peripheral (SP), circular chordal (CC) and circular peripheral (CP). The calculation of the effective area and boundary conditions remains the same when performing all four configurations. The consequent results show that for the tubular structure PEMFC, compared with the co-flow mode, the counter-flow mode has better performance and provides more power. Using a counter-flow pattern, the permeability of the species increases, so a more uniform reaction occurs at the cell. The entire performance of the SP and CP model is not as good as that of the SC and CC models because the SP and CP models have a higher flow velocity. Moreover, the SC model using the counter-flow pattern has the maximum predicted net power among the other models.
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Han, Fei, Lei Wang y Guang Feng. "An Advanced Algorithm of Power Flow Calculation for Radial Distribution Networks". Advanced Materials Research 860-863 (diciembre de 2013): 1933–36. http://dx.doi.org/10.4028/www.scientific.net/amr.860-863.1933.
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Through the analysis of traditional forward and backward substitution method, put forward an advanced algorithm of power flow calculation applied for the radial distribution network. This method optimizes the numbered embranchments, nodes, branches, uses directly the branch impedance parameter and the given power of the end node to calculate the voltage and power distribution, And use MATLAB to compile power flow calculation program, which is proved to be feasible by an example.
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Burian, Ondrej, Vaclav Dostal y Ladislav Vesely. "STUDY OF IDENTIFICATION OF TWO-PHASE FLOW PARAMETERS BY PRESSURE FLUCTUATION ANALYSIS". Acta Polytechnica CTU Proceedings 4 (16 de diciembre de 2016): 1. http://dx.doi.org/10.14311/ap.2016.4.0001.
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This paper deals with identification of parameters of simple pool boiling in a vertical rectangular channel by analysis of pressure fluctuation. In this work is introduced a small experimental facility about 9 kW power, which was used for simulation of pool boiling phenomena and creation of steam-water volume. Several pressure fluctuations measurements and differential pressure fluctuations measurements at warious were carried out. Main changed parameters were power of heaters and hydraulics resistance of channel internals. Measured pressure data was statistically analysed and compared with goal to find dependencies between parameters of two-phase flow and statistical properties of pressure fluctuation. At the end of this paper are summarized final results and applicability of this method for parameters determination of two phase flow for pool boiling conditions at ambient pressure.
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Ma, Tengfei, Junyong Wu, Liangliang Hao y Dezhi Li. "Corrigendum to “Energy flow matrix modeling and optimal operation analysis of multi energy systems based on graph theory” [Appl. Therm. Eng. 146 (2019) 648–663]". Applied Thermal Engineering 162 (noviembre de 2019): 114323. http://dx.doi.org/10.1016/j.applthermaleng.2019.114323.
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Thanon Dawood, Eethar y Mafaz Hani Abdullah. "Behavior of non-reinforced and reinforced green mortar with fibers". Open Engineering 11, n.º 1 (19 de noviembre de 2020): 67–84. http://dx.doi.org/10.1515/eng-2021-0006.
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AbstractThe behavior of non-reinforced green mortar with fibers has been observed. Different green mortar mixes have been prepared using different percentages of waste glass powder (WGP), steel slag (SG) and silica fume (SF).The properties of flow, density, ultrasonic pulse velocity (UPV), compressive and flexural strengths have been tested for such green mortar in the first phase of the experimental work. The selected green mortar mix that gives good properties with the acceptable ranges of cement replacement by such cementitious materials has been utilized to achieve the second phase of the experimental work. Thus, the uses of human hair fibers, sisal fibers and stainless steel nails fibers in the form of individual and hybrid fibers system and testing for the same properties mentioned above have been performed. The third phase includes the cost estimation for the said mortar. Whereas, the last phase deals with analysis of the results using the integrated AHP and TOPSIS method for selection the best performance of the green mortar. The results of mono sisal fiber, human hair fiber and stainless nails fiber by 0.75, 0.75 and 2% of volume fraction respectively, exhibited the highest increase in compressive strength, flexural strength, UPV and density compared with other percentages.
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Guo, Gang y Rui Li. "Energy Saving Analysis and Application of Secondary Pump in Air Conditioning Water System". Advanced Materials Research 516-517 (mayo de 2012): 1235–39. http://dx.doi.org/10.4028/www.scientific.net/amr.516-517.1235.
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The application of frequency conversion technique in secondary pump and variable flow system is expounded in this essay. In the view of energy conservation, the secondary frequency conversion pump in variable flow system is in favor of energy conservation due to its variability on power according to the end load change, the principle of frequency conversion pump is also analysed. Combined with actual project case, he energy saving potential of secondary pump and variable flow system is discussed.
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Wang, Lei, Ye Xin Xu, Rui Ming Yuan, Xi Wu y Xiao Jie Xu. "Analysis of Radiation Performance for a Combustion-End Radiator of a TPV System". Applied Mechanics and Materials 448-453 (octubre de 2013): 1353–58. http://dx.doi.org/10.4028/www.scientific.net/amm.448-453.1353.
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In this paper, the authors analyzed effects of the factors, such as the air mass flow rate, the geometric dimensioning of the inner and outer combustion tubes and the thickness of the radiator, to the performance of the combustion-end radiator system. The result shows that optimal performance will be achieved when the combustion power is 1kW and the air mass flow rate is 5 times higher than the requirement for the complete combustion of CH4. On this basis, the effect of the geometric dimensioning to the combustion-radiator system is discussed. The performance of the combustion-radiator system is the best when the inner diameter of inner tube is 24mm, the length of the combustion tube is 40mm and the radiator thickness is 1mm. In this condition, the average temperature of the radiant surface, the radiant power density of the radiator and the combustion efficiency are 1530K, 9.41W/cm2 and 47.3%, respectively.
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Yuya, H., K. Nagata, Y. Watahiki, E. Yokoyama, J. Hatazawa, K. Nakajima y M. Nakamura. "4-15-09 Combined analysis of EEG power with blood flow and metabolism in mitochondrial cytopathies". Journal of the Neurological Sciences 150 (septiembre de 1997): S233. http://dx.doi.org/10.1016/s0022-510x(97)86009-1.
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Soulas, Thomas y Luis San Andres. "A Bulk Flow Model for Off-Centered Honeycomb Gas Seals". Journal of Engineering for Gas Turbines and Power 129, n.º 1 (1 de marzo de 2002): 185–94. http://dx.doi.org/10.1115/1.2227031.
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A computational analysis for prediction of the static and dynamic forced performance of gas honeycomb seals at off-centered rotor conditions follows. The bulk-flow analysis, similar to the two-control volume flow model of Kleynhans and Childs (1997, “The Acoustic Influence of Cell Depth on the Rotordynamic Characteristics of Smooth-Rotor/Honeycomb-Stator Annular Gas Seals,” ASME J. Eng. Gas Turbines Power, 119, pp. 949–957), is brought without loss of generality into a single-control volume model, thus simplifying the computational process. The formulation accommodates the honeycomb effective cell depth, and existing software for annular pressure seals and is easily upgraded for damper seal analysis. An analytical perturbation method for derivation of zeroth- and first-order flow fields renders the seal equilibrium response and frequency-dependent dynamic force impedances, respectively. Numerical predictions for a centered straight-bore honeycomb gas seal shows good agreement with experimentally identified impedances, hence validating the model and confirming the paramount influence of excitation frequency on the rotordynamic force coefficients of honeycomb seals. The effect of rotor eccentricity on the static and dynamic forced response of a smooth annular seal and a honeycomb seal is evaluated for characteristic pressure differentials and rotor speeds. Leakage for the two seal types increases slightly as the rotor eccentricity increases. Rotor off-centering has a pronounced nonlinear effect on the predicted (and experimentally verified) dynamic force coefficients for smooth seals. However, in honeycomb gas seals, even large rotor center excursions do not sensibly affect the effective local film thickness, maintaining the flow azimuthal symmetry. The current model and predictions thus increase confidence in honeycomb seal design, operating performance, and reliability in actual applications.
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Liu, C. Q. "Combination of an Improved FRF-Based Substructure Synthesis and Power Flow Method with Application to Vehicle Axle Noise Analysis". Shock and Vibration 15, n.º 1 (2008): 51–60. http://dx.doi.org/10.1155/2008/830281.
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In this paper, an improved FRF-based substructure synthesis method combined with power flow analysis is presented and is used for performing a vehicle axle noise analysis. The major transfer paths of axle noise transmitted from chassis to vehicle body are identified and ranked based on power flows transmitted through bushings between the chassis and body. To calculate the power flows, it is necessary to know the reaction forces and the vibrations at the bushing locations on the body side. To this end, the body is represented in terms of experimentally derived frequency response functions (FRF's) at the bushing locations, and the FRF's are coupled with the FEA model of the chassis for performing a total system dynamic analysis. This paper also describes how the FRF's of the vehicle body and the frequency dependent stiffness data of the bushings can be combined together with a simple formulation to better represent the dynamic characteristics of a full vehicle. A classical example is used to illustrates the concept of the method, and the method is then applied to a vehicle axle noise analysis with detailed procedure. The theoretical predictions are compared with experimentally measured results. Good correlation has been obtained.
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Dong, Peng, Shengdun Zhao, Yongqiang Zhao, Peng Zhang y Yongfei Wang. "Design and experimental analysis of end face profile of tri-screw pump". Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 234, n.º 4 (20 de agosto de 2019): 481–89. http://dx.doi.org/10.1177/0957650919870373.
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This study proposes a new type of tri-screw pump, which has a 1:2:3 ratio of the active diameter of the screw, the diameter of the pitch circle, and the top diameter of the active screw. Fixed width correction method of the driven screw is also proposed to avoid wear of tooth top. The mathematical model of active and driven screws is established. To avoid the wear of the tooth top arc, several transition patterns are proposed, and the transition curve in the form of a circular arc is deduced. The designed screw curve is grinded, and the tri-screw pump is assembled. The hydraulic pump test bench is tested using the overflow valve to perform pressure loading of 3–5 MPa on the outlet of the screw pump. The outlet flow rate and pressure are tested, and results indicate that the output flow of the pump conforms to the designed flow rate. This study establishes the detailed equation of the end face profile of the tri-screw pump (active and driven screws) and corrects the arc profile of the line angle.
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Liu, Hui, Zhihao Zhang y Shuang Wu. "Theoretical and experimental analysis of thermal energy management system of air source self-powered electric gas generator". Thermal Science 24, n.º 5 Part B (2020): 3395–403. http://dx.doi.org/10.2298/tsci191223131l.
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In order to solve the problem that the auxiliary equipment of electric gas turbine can operate only by relying on external power, and realize the purpose that auxiliary equipment of electric gas turbine can operate independently without the external power grid, in this research, a management system of air source self-powered electric gas generator is proposed. Firstly, the process of the thermal energy management system of the air source self-powered electric gas generator is introduced, and the thermodynamic theory of the thermal energy management system of the air source self-powered electric gas generator is analyzed. Then, the experimental conditions of air source self-powered electric gas generator are introduced. Finally, the results of variable speed and terminal variable flow in heating condition and terminal variable flow in cooling condition of the thermal energy management system of air source self-powered electric gas generator are analyzed. The results show that whether the thermal energy management system of air source self-powered electric gas generator studied in this research is in heating or cooling conditions, both the output power of the engine and the power of the compressor increase with the increase of the rotating speed. It can be concluded from the variable flow results in heating conditions that the smaller the end flow is, the smaller the output power of the engine will be. In this way, the loss of heat transfer efficiency of the plate can be reduced as much as possible, and the users? demand for heat can be met.
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Abirami, P. y C. N. Ravi. "Load flow analysis of 10 bus loop distribution network excited by a generator simulated using open modelica". International Journal of Power Electronics and Drive Systems (IJPEDS) 12, n.º 2 (1 de junio de 2021): 1006. http://dx.doi.org/10.11591/ijpeds.v12.i2.pp1006-1014.
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<span lang="EN-CA">In recent days, due to advancement in technology, the end users are facing severe power quality issues. Load flow analysis is one of the fundamental methodologies in solving power network problems. The key importance of Load flow analysis is to improve the performance of distribution network. The main intention of this reserach is to carry out the load flow and voltage stability analysis of 10 bus loop distribution network energized by a generator. Load flow analysis is carried out by using Newton Raphson method. The per unit voltage and angle of the proposed network is determined in all 10 buses by load flow analysis. The voltage stability analysis is implemented by introducing a fault in the network. Here, a power fault is injected at bus 4 between the time interval of 2 to 3 sec to analyse the stability of the system. The voltage stability of the system is analysed for the network with and without automatic voltage regulator (AVR). The AVR unit is tuned by using power system stabilizer (PSS). The results are examined by simulating the network using open modelica connection editor. From the simulation results the per unit voltages and angles at all 10 buses are determined for the network with and without AVR. By comparing both the results it is proved that the network with AVR has better voltage stability than the other. Thus, the voltage stability of the system is improved by connecting the generator with AVR and PSS.</span>
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Haque, Md Enamul, Md Efthakher Hossain y Mohammad Mashud. "Performance Analysis of a Heat Pipe with Stainless Steel Wick". Journal of Engineering Advancements 01, n.º 01 (abril de 2020): 16–22. http://dx.doi.org/10.38032/jea.2020.01.004.
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In this study, the influences of different parameters on performance of a heat pipe with stainless steel net as wick have been presented. Experiments have been carried out for an input power range from 80 W to 160 W, constant cooling water mass flow rate of 0.0515 liter/s, and constant temperature at the inlet to condenser of 11°C. The temperatures were recorded at different power level by using a laser thermometer of the heater block, evaporator and condenser end at 50 second interval. Variation in the input power was done by varying the input voltage. It was done by a variack. Considering all criteria the copper is selected as the material of the container, water is selected as the working fluid of the heat pipe, stainless steel net is used as wick material. As copper/water heat pipes are able to tolerate storage temperatures between -65°C and 250°C, and can effectively operate between 10°C and 250°C. So a .9144 m copper tube is used to construct the heat pipe. Inside this tube stainless steel net is used as wick material to aid the flow of fluid. In the observation it is observed that the temperature of the evaporator end increases at a greater rate of the copper pipe than the heat pipe at different power level. It has been shown the variation of temperature of the heater block and the evaporator section at 80V, 100V, 120V, 140V, 160V respectively of the heat pipe and copper pipe.
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Li, Zheng, Hong Wu Zhu, Xiao Li Fan, Jian Sheng Hao y Xiang Ling Kong. "Numerical Analysis of Pressure Gradient along Casing in Helical Turbulent Flow of Power Law Fluid in Eccentric Annulus". Advanced Materials Research 616-618 (diciembre de 2012): 685–89. http://dx.doi.org/10.4028/www.scientific.net/amr.616-618.685.
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With the use of casing running tool (CRT), casing can be rotated and reciprocated at the same time with circulation of drilling fluid. Thus the flow in well bore was eccentric annular helical. Pressure exerted on casing was important for casing buckling analysis. A numerical model of eccentric annular helical flow of power law fluid was built in this paper. The relationship between average pressure gradient on pipe and some influence factors (pipe axial velocity, rotating angular velocity, drilling fluid circulation velocity, and axial coordination) was analyzed. Results showed that average pressure gradient caused by shear stress was only affected by average annular flow velocity, and it didn’t change along pipe length. Effect of rotating angular velocity on average pressure gradient on pipe was very small and could be negligible. A fitting function between average pressure gradient and average annular flow velocity was obtained in this end.
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Oliveira, T. F., R. B. Miserda y F. R. Cunha. "Dynamical Simulation and Statistical Analysis of Velocity Fluctuations of a Turbulent Flow behind a Cube". Mathematical Problems in Engineering 2007 (2007): 1–28. http://dx.doi.org/10.1155/2007/24627.
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A statistical approach for the treatment of turbulence data generated by computer simulations is presented. A model for compressible flows at large Reynolds numbers and low Mach numbers is used for simulating a backward-facing step airflow. A scaling analysis has justified the commonly used assumption that the internal energy transport due to turbulent velocity fluctuations and the work done by the pressure field are the only relevant mechanisms needed to model subgrid-scale flows. From the numerical simulations, the temporal series of velocities are collected for ten different positions in the flow domain, and are statistically treated. The statistical approach is based on probability averages of the flow quantities evaluated over several realizations of the simulated flow. We look at how long of a time average is necessary to obtain well-converged statistical results. For this end, we evaluate the mean-square difference between the time average and an ensemble average as the measure of convergence. This is an interesting question since the validity of the ergodic hypothesis is implicitly assumed in every turbulent flow simulation and its analysis. The ergodicity deviations from the numerical simulations are compared with theoretical predictions given by scaling arguments. A very good agreement is observed. Results for velocity fluctuations, normalized autocorrelation functions, power spectra, probability density distributions, as well as skewness and flatness coefficients are also presented.
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Pierzga, M. J. y J. R. Wood. "Closure to “Discussions of ‘Investigation of the Three-Dimensional Flow Field Within a Transonic Fan Rotor: Experiment and Analysis’” (1985, ASME J. Eng. Gas Turbines Power, 107, p. 448)". Journal of Engineering for Gas Turbines and Power 107, n.º 2 (1 de abril de 1985): 449. http://dx.doi.org/10.1115/1.3239747.
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Asha Devi, Dharmavaram, Chintala Sandeep y Sai Sugun L. "Design of Power Efficient 32-Bit Processing Unit". International Journal of Engineering & Technology 7, n.º 2.16 (12 de abril de 2018): 52. http://dx.doi.org/10.14419/ijet.v7i2.16.11415.
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The proposed paper is discussed about the design, verification and analysis of a 32-bit Processing Unit. The complete front-end design flow is processed using Xilinx Vivado System Design Suite software tools and target verification is done by using Artix 7 FPGA. Virtual I/O concept is used for the verification process. It will perform 32 different operations including parity generation and code conversions: Binary to Grey and Grey to Binary. It is a low power design implemented with Verilog HDL and power analysis is implementedwith clock frequencies ranging from 10MhZ to 100GhZ. With all these frequencies, power analysis is verified for different I/O standards LVCMOS12, LVCMOS25 and LVCMOS33.
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Skalozubov, V., I. Kozlov, O. Chulkin, Yu Komarov y O. Piontkovskyi. "Analysis of Reliability-Critical Hydraulic Impact Conditions at WWER-1000 NPP Active Safety Systems". Nuclear and Radiation Safety, n.º 1(81) (12 de marzo de 2019): 42–45. http://dx.doi.org/10.32918/nrs.2019.1(81).07.
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An original method to determine the onset of conditions for reliabilitycritical hydraulic impacts for reliability analysis of active safety systems of nuclear power installations is proposed. The suggested method is based on determining the effect of head-flow characteristic delay onto hydraulic impact preconditions during the changes of pipeline system hydrodynamic parameters under transitional modes (e.g. in pump start-up). The delay time of responses to change in the hydrodynamic system parameters embodies the determining factor of head-flow characteristic’s inertance, depending on both design and technical parameters of system components (including pumps), and the hydrodynamic parameters change rate under transitional modes. Using the proposed method, the analysis of conditions for critical hydraulic impacts is performed for the primary high-pressure safety injection system of serial WWER-1000 nuclear power plants. The analysis results allow a conclusion that for this system the conditions leading to hydraulic impact due to the pump start are not reached. The developed method can be applied to any thermal and nuclear power facilities’ pipeline systems equipped with pumps.
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Kress, R. y R. Roemer. "A Comparative Analysis of Thermal Blood Perfusion Measurement Techniques". Journal of Biomechanical Engineering 109, n.º 3 (1 de agosto de 1987): 218–25. http://dx.doi.org/10.1115/1.3138672.
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The object of this study was to devise a unified method for comparing different thermal techniques for the estimation of blood perfusion rates and to perform a comparison for several common techniques. The approach used was to develop analytical models for the temperature response for all combinations of five power deposition geometries (spherical, one- and two-dimensional cylindrical, and one- and two-dimensional Gaussian) and three transient heating techniques (temperature pulse-decay, temperature step function, and constant-power heat-up) plus one steady-state heating technique. The transient models were used to determine the range of times (the time window) when a significant portion of the transient temperature response was due to blood perfusion. This time window was defined to begin when the difference between the conduction-only and the conduction-plus-blood flow transient temperature (or power) responses exceeded a specified value, and to end when the conduction-plus-blood flow transient temperature (or power) reached a specified fraction of its steady-state value. The results are summarized in dimensionless plots showing the size of the time windows for each of the transient perfusion estimation techniques. Several conclusions were drawn, in particular: (a) low perfusions are difficult to estimate because of the dominance of conduction, (b) large heated regions are better suited for estimation of low perfusions, (c) noninvasive heating techniques are superior because they have the potential to minimize conduction effects, and (d) none of the transient techniques appears to be clearly superior to the others.
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Bidini, G., C. N. Grimaldi y L. Postrioti. "Thermodynamic analysis of hydraulic air compressor-gas turbine power plants". Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 211, n.º 5 (1 de agosto de 1997): 429–37. http://dx.doi.org/10.1243/0957650971537321.
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Nowadays, the most common way to improve energy conversion efficiency is the integration of different systems, thus achieving a better exploitation of the available exergy potential (e.g. combined cycles, cogeneration, etc.). As a means of producing power in hydroelectric plants hydraulic energy is commonly considered to be almost completely exploited. The aim of this paper is to analyse the possible integration of hydraulic energy sources with conventional, fossil fuel based systems; in particular, power plants based on the combination of an hydraulic air compressor (HAC) and a gas turbine are considered. In an HAC, air is entrained in the water flow in a downcomer pipe and compressed. Once separated from the water in a ‘stilling chamber’ at the bottom of the downpipe, the compressed air is supplied to a combustion chamber and then to a conventional gas turbine expander. An attractive characteristic of HACs is the capability, in principle, to perform an isothermal air compression instead of an adiabatic one, as in conventional compressors. In the present work, a thermodynamic analysis is presented of HAC-gas turbine energy conversion systems, which are compared with conventional hydroelectric and gas turbine power plants. The calculated performance levels of such systems are comparable to those of combined cycle plants, making further technical and economical investigations quite interesting.
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Zhao, Wei, Yuting Liu, Xiandong Liu, Yingchun Shan y Xiaojun Hu. "Analysis of Tire Acoustic Cavity Resonance Energy Transmission Characteristics in Wheels Based on Power Flow Method". Applied Sciences 11, n.º 9 (27 de abril de 2021): 3979. http://dx.doi.org/10.3390/app11093979.
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As a kind of low-frequency vehicle interior noise, tire acoustic cavity resonance noise plays an important role, since the other noise (e.g., engine noise, wind noise and friction noise) has been largely suppressed. For the suspension system, wheels stand first in the propagation path of this energy. Therefore, it is of great significance to study the influence of wheel design on the transmission characteristics of this vibration energy. However, currently the related research has not received enough attention. In this paper, two sizes of aluminum alloy wheel finite element models are constructed, and their modal characteristics are analyzed and verified by experimental tests simultaneously. A mathematically fitting sound pressure load model arising from the tire acoustic cavity resonance acting on the rim is first put forward. Then, the power flow method is applied to investigate the resonance energy distribution and transmission characteristics in the wheels. The structure intensity distribution and energy transmission efficiency can be described and analyzed clearly. Furthermore, the effects of material structure damping and the wheel spoke number on the energy transmission are also discussed.
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Li, Kewen y Roland N. Horne. "A Decline Curve Analysis Model Based on Fluid Flow Mechanisms". SPE Reservoir Evaluation & Engineering 8, n.º 03 (1 de junio de 2005): 197–204. http://dx.doi.org/10.2118/83470-pa.
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Summary Decline-curve-analysis models are used frequently but still have many limitations. Approaches of decline-curve analysis used for naturally fractured reservoirs developed by waterflooding have been few. To this end, a decline-analysis model derived on the basis of fluid-flow mechanisms was proposed and used to analyze the oil-production data from naturally fractured reservoirs developed by waterflooding. Relative permeability and capillary pressure were included in this model. The model reveals a linear relationship between the oil-production rate and the reciprocal of the oil recovery or the accumulated oil production. We applied the model to the oil-production data from different types of reservoirs and found a linear relationship between the production rate and the reciprocal of the oil recovery as foreseen by the model, especially at the late period of production. The values of maximum oil recovery for the example reservoirs were evaluated with the parameters determined from the linear relationship. An analytical oil-recovery model was also proposed. The results showed that the analytical model could match the oil-production data satisfactorily. We also demonstrated that the frequently used nonlinear type curves could be transformed to linear relationships in a log-log plot. This may facilitate the production-decline analysis. Finally, the analytical model was compared with conventional models. Introduction Estimating reserves and predicting production in reservoirs has been a challenge for many years. Many methods have been developed in the last several decades. One frequently used technique is the decline-curve-analysis approach. There have been a great number of papers on this subject. Most of the existing decline-curve-analysis techniques are based on the empirical Arps equations: exponential, hyperbolic, and harmonic. It is difficult to foresee which equation the reservoir will follow. On the other hand, each approach has some disadvantages. For example, the exponential decline curve tends to underestimate reserves and production rates; the harmonic decline curve has a tendency to overpredict the reservoir performance. In some cases, production-decline data do not follow any model but cross over the entire set of curves. Fetkovich combined the transient rate and the pseudosteady-state decline curves in a single graph. He also related the empirical equations of Arps to the single-phase-flow solutions and attempted to provide a theoretical basis for the Arps equations. This was realized by developing the connection between the material balance and the flow-rate equations on the basis of his previous papers. Many derivations were based on the assumption of single-phase oil flow in closed-boundary systems. These solutions were suitable only for undersaturated(single-phase) oil flow. However, many oil fields are developed by waterflooding. Therefore, two-phase fluid flow (rather than single-phase flow)occurs. In this case, Lefkovits and Matthews derived the exponential decline form for gravity-drainage reservoirs with a free surface by neglecting capillary pressure. Fetkovich et al. included gas/oil relative permeability effects on oil production for solution-gas drive through the pressure-ratio term. This assumes that the oil relative permeability is a function of pressure. It is known that gas/oil relative permeability is a function of fluid saturation, which depends on fluid/rock properties.
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Yang, Liu y Chunlin Deng. "A United Method for Sensitivity Analysis of the Locational Marginal Price Based on the Optimal Power Flow". Mathematical Problems in Engineering 2014 (2014): 1–7. http://dx.doi.org/10.1155/2014/141636.
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Locational marginal prices (LMPs) are influenced by various factors in the electricity market; knowing the sensitivity information of LMPs is very important for both the purchase and the consumer. This paper presents a united method to compute the sensitivities of LMPs based on the optimal power flow (OPF). The Karush-Kuhn-Tucher (KKT) system to solve LMPs can be transferred into an equation system by using an NCP function, and then by using the properties of the derivative of the semismooth NCP function, this paper provides a simultaneous obtention of the sensitivities of LMPs with respect to power demands, the cost of production, voltage boundary, and so forth. Numerical examples illustrate the concepts presented and the proposed methodology by a 6-bus electric energy system. Some relevant conclusions are drawn in the end.
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Alabrudziński, Sławomir. "Numerical Analysis of Shell-Side Fluid Flow in Shell-and-Tube Heat Exchanger". Applied Mechanics and Materials 797 (noviembre de 2015): 255–62. http://dx.doi.org/10.4028/www.scientific.net/amm.797.255.
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This work presents velocity field and flow resistance analysis on shell-side of shell-and-tube heat exchanger. Numerical investigations have been carried out using a finite volume method implemented in ANSYS Fluent code. In case of heat exchangers with a great number of tubes in bundle, the finite volume method numerical model representing real geometry of the apparatus becomes very complex and results in a high computing power demand. To overcome the above difficulty, an attempt has been made to represent the tube bundle using the continuum approach. The resulting pressure drop values have been compared with e.g. calculation results using HTRI code and exemplary values obtained from the real apparatus.
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Ilk, D., D. M. M. Anderson, G. W. J. W. J. Stotts, L. Mattar y T. A. A. Blasingame. "Production-Data Analysis—Challenges, Pitfalls, Diagnostics". SPE Reservoir Evaluation & Engineering 13, n.º 03 (8 de junio de 2010): 538–52. http://dx.doi.org/10.2118/102048-pa.
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Summary The analysis of production data to determine reservoir characteristics, completion effectiveness, and hydrocarbons in place has become very popular in recent years. Although production analysis (PA) for reservoir characterization is approaching the popularity of pressure-transient analysis (PTA), there are few consistent diagnostic methods in practice for the analysis of production data. Many of the diagnostic methods for production-data analysis are little more than observation-based approaches—and some are essentially rules of thumb. In this work, we provide guidelines for the analysis of production data, as well as identify common pitfalls and challenges. Although PTA and production-data analyses have the same governing theory (and solutions), we must recognize that pressure transient data are acquired as part of a controlled experiment, performed as a specific event [e.g., a pressure-buildup (PBU) test]. In contrast, production data are generally considered to be surveillance/monitoring data—with little control and considerable variance occurring during the acquisition of the production data. We note that since both PA and PTA have the same governing relations, it is possible "in theory" that the same deliverables of PTA can be obtained using PA. This paper attempts to provide a state-of-the-technology review of current production-data-analysis techniques/tools—particularly tools to diagnose the reservoir model and assess the reservoir condition. The reservoir model is diagnosed mainly by examining the character exhibited by the data [that is the evidence of transient flow (e.g., quarter-slope might indicate a finite-conductivity fracture, or half-slope might indicate radial/pseudoradial flow)]. In addition, one can also assess the reservoir condition by inspecting the character of production data, which can confirm the evidence of boundary-dominated flow such that unit slope may indicate the boundary-dominated-flow regime and, therefore, in-place fluid volume can be estimated. This work also identifies the challenges and pitfalls of PA—and we try to provide guidance toward best practices and best tools. To complement this mission, we use relevant field examples to address specific issues, and we illustrate the value and function of production-data analysis for a wide range of reservoir types and properties. In this work, we propose the use of a sequence of raw and enhanced data plots for the diagnostic analysis of production data. We strongly believe that a comprehensive and systematic approach for production-data diagnosis has significant importance for the analysis and forecast of production performance.
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Kasap, Ekrem, Kun Huang, Than Shwe y Dan Georgi. "Formation-Rate-Analysis Technique: Combined Drawdown and Buildup Analysis for Wireline Formation Test Data". SPE Reservoir Evaluation & Engineering 2, n.º 03 (1 de junio de 1999): 271–80. http://dx.doi.org/10.2118/56841-pa.
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Summary The formation-rate-analysis (FRASM) technique is introduced. The technique is based on the calculated formation rate by correcting the piston rate with fluid compressibility. A geometric factor is used to account for irregular flow geometry caused by probe drawdown. The technique focuses on the flow from formation, is applicable to both drawdown and buildup data simultaneously, does not require long buildup periods, and can be implemented with a multilinear regression, from which near-wellbore permeability, p * and formation fluid compressibility are readily determined. The field data applications indicate that FRA is much less amenable to data quality because it utilizes the entire data set. Introduction A wireline formation test (WFT) is initiated when a probe from the tool is set against the formation. A measured volume of fluid is then withdrawn from the formation through the probe. The test continues with a buildup period until pressure in the tool reaches formation pressure. WFTs provide formation fluid samples and produce high-precision vertical pressure profiles, which, in turn, can be used to identify formation fluid types and locate fluid contacts. Wireline formation testing is much faster compared with the regular pressure transient testing. Total drawdown time for a formation test is just a few seconds and buildup times vary from less than a second (for permeability of hundreds of millidarcy) to half a minute (for permeability of less than 0.1 md), depending on system volume, drawdown rate, and formation permeability. Because WFT tested volume can be small (a few cubic centimeters), the details of reservoir heterogeneity on a fine scale are given with better spatial resolution than is possible with conventional pressure transient tests. Furthermore, WFTs may be preferable to laboratory core permeability measurements since WFTs are conducted at in-situ reservoir stress and temperature. Various conventional analysis techniques are used in the industry. Spherical-flow analysis utilizes early-time buildup data and usually gives permeability that is within an order of magnitude of the true permeability. For p* determination, cylindrical-flow analysis is preferred because it focuses on late-time buildup data. However, both the cylindrical- and spherical-flow analyses have their drawbacks. Early-time data in spherical-flow analysis results in erroneous p* estimation. Late-time data are obtained after long testing times, especially in low-permeability formations; however, long testing periods are not desirable because of potential tool "sticking" problems. Even after extended testing times, the cylindrical-flow period may not occur or may not be detectable on WFTs. When it does occur, permeability estimates derived from the cylindrical-flow period may be incorrect and their validity is difficult to judge. New concepts and analysis techniques, combined with 3-D numerical studies, have recently been reported in the literature.1–7 Three-dimensional numerical simulation studies1–6 have contributed to the diagnosis of WFT-related problems and the improved analysis of WFT data. The experimental studies7 showed that the geometric factor concept is valid for unsteady state probe pressure tests. This study presents the FRA technique8 that can be applied to the entire WFT where a plot for both drawdown and buildup periods renders straight lines with identical slopes. Numerical simulation studies were used to generate data to test both the conventional and the FRA techniques. The numerical simulation data are ideally suited for such studies because the correct answer is known (e.g., the input data). The new technique and the conventional analysis techniques are also applied to the field data and the results are compared. We first review the theory of conventional analysis techniques, then present the FRA technique for combined drawdown and buildup data. A discussion of the numerical results and the field data applications are followed by the conclusions. Analysis Techniques It has been industry practice to use three conventional techniques, i.e., pseudo-steady-state drawdown (PSSDD), spherical and cylindrical-flow analyses, to calculate permeability and p* Conventional Techniques Pseudo-Steady-State Drawdown (PSSDD). When drawdown data are analyzed, it is assumed that late in the drawdown period the pressure drop stabilizes and the system approaches to a pseudo-steady state when the formation flow rate is equal to the drawdown rate. PSSDD permeability is calculated from Darcy's equation with the stabilized (maximum) pressure drop and the flowrate resulting from the piston withdrawal:9–11 $$k {d}=1754.5\left({q\mu \over r {i}\Delta p {{\rm max}}}\right),\eqno ({\rm 1})$$where kd=PSSDD permeability, md. The other parameters are given in Nomenclature.
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Lakovic, Mirjana, Mladen Stojiljkovic, Slobodan Lakovic, Velimir Stefanovic y Dejan Mitrovic. "Impact of the cold end operating conditions on energy efficiency of the steam power plants". Thermal Science 14, suppl. (2010): 53–66. http://dx.doi.org/10.2298/tsci100415066l.
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The conventional steam power plant working under the Rankine Cycle and the steam condenser as a heat sink and the steam boiler as a heat source have the same importance for the power plant operating process. Energy efficiency of the coal fired power plant strongly depends on its turbine-condenser system operation mode. For the given thermal power plant configuration, cooling water temperature or/and flow rate change generate alterations in the condenser pressure. Those changes have great influence on the energy efficiency of the plant. This paper focuses on the influence of the cooling water temperature and flow rate on the condenser performance, and thus on the specific heat rate of the coal fired plant and its energy efficiency. Reference plant is working under turbine-follow mode with an open cycle cooling system. Analysis is done using thermodynamic theory, in order to define heat load dependence on the cooling water temperature and flow rate. Having these correlations, for given cooling water temperature it is possible to determine optimal flow rate of the cooling water in order to achieve an optimal condensing pressure, and thus, optimal energy efficiency of the plant. Obtained results could be used as useful guidelines in improving existing power plants performances and also in design of the new power plants. <br><br><font color="red"><b> This article has been corrected. Link to the correction <u><a href="http://dx.doi.org/10.2298/TSCI151102198E">10.2298/TSCI151102198E</a><u></b></font>
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Wanjing, Luo y Tang Changfu. "Pressure-Transient Analysis of Multiwing Fractures Connected to a Vertical Wellbore". SPE Journal 20, n.º 02 (21 de agosto de 2014): 360–67. http://dx.doi.org/10.2118/171556-pa.
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Summary The principal focus of this work is on transient-pressure behaviors of multiwing fractures connected to a vertical wellbore. The vertical well is fractured with multiple-fracture wings with varied intersection angle, length, and asymmetry factor (AF). In the case of equally spaced fractures connected to a vertical wellbore, three flow regimes may be observed: bilinear-flow regime, formation linear flow, and pseudoradial-flow regime. With the increase of fracture numbers, the interaction of fractures becomes stronger and a “hump” occurs on the curves of pressure derivative for low and moderate fracture conductivities. For an anisotropic formation, the fracture may grow at a specific azimuth, and a fracture cluster develops. Because of the strong interactions among fracture clusters, the end of bilinear flow occurs earlier, and the formation linear flow will not be observed even for high fracture conductivities. In some extreme case in which a vertical well is intercepted with highly asymmetrically distributed fracture clusters, its transient performances of pressure and pressure-derivative curves may deviate from the conventional type curves totally. In addition, it is found that the complexity of multiple fractures near the wellbore can enhance the recovery of oil and gas.
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Hua, Ze Jia, Jing Wu, Ze Ya Mi y Jia Lei Zhu. "Simulation of PV and Wind Hybrid Power System". Advanced Materials Research 953-954 (junio de 2014): 591–94. http://dx.doi.org/10.4028/www.scientific.net/amr.953-954.591.
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The PV and wind hybrid power system uses the front-end DC-DC conversion circuit, the system's overall output power is unified deployment and controlled, through elaborating the component characteristics and assessing mathematical model of the actual obtained, more accurately determines operation condition of the system per hour. The system energy analysis of flow and motion makes the system in dynamic change switch from the different forms of work patterns and operation, completing the corresponding control, so as to realize the optimization of system and reliable operation.
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Liberal, Iñigo, Michaël Lobet, Yue Li y Nader Engheta. "Near-zero-index media as electromagnetic ideal fluids". Proceedings of the National Academy of Sciences 117, n.º 39 (10 de septiembre de 2020): 24050–54. http://dx.doi.org/10.1073/pnas.2008143117.
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Near-zero-index (NZI) supercoupling, the transmission of electromagnetic waves inside a waveguide irrespective of its shape, is a counterintuitive wave effect that finds applications in optical interconnects and engineering light–matter interactions. However, there is a limited knowledge on the local properties of the electromagnetic power flow associated with supercoupling phenomena. Here, we theoretically demonstrate that the power flow in two-dimensional (2D) NZI media is fully analogous to that of an ideal fluid. This result opens an interesting connection between NZI electrodynamics and fluid dynamics. This connection is used to explain the robustness of supercoupling against any geometrical deformation, to enable the analysis of the electromagnetic power flow around complex geometries, and to examine the power flow when the medium is doped with dielectric particles. Finally, electromagnetic ideal fluids where the turbulence is intrinsically inhibited might offer interesting technological possibilities, e.g., in the design of optical forces and for optical systems operating under extreme mechanical conditions.
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Ji, Lin. "Power Flow and Energy Sharing between an Oscillator and a Continuous Receiver Structure". Advanced Materials Research 189-193 (febrero de 2011): 1914–17. http://dx.doi.org/10.4028/www.scientific.net/amr.189-193.1914.
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A key assumption of conventional Statistical Energy Analysis (SEA) theory is that, for two coupled subsystems, the transmitted power from one to another is proportional to the energy differences between the mode pairs of the two subsystems. Previous research has shown that such an assumption remains valid if each individual subsystem is of high modal density. This thus limits the successful applications of SEA theory mostly to the regime of high frequency vibration modeling. This paper argues that, under certain coupling conditions, conventional SEA can be extended to solve the mid-frequency vibration problems where systems may consist of both mode-dense and mode-spare subsystems, e.g. ribbed-plates.