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Thermodynamic Analysis on a Pre-dried Lignite-fired power System: Comparison on Energy Supply Systems for Dryer

Energy Procedia 2014年 61卷 1424-1427页

作者： Ming Liu Junjie Yan Jinshi Wang Daotong Chong Jiping Liu State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an 710049 China

Pre-drying is a potential way to improve the electric generation efficiency of lignite-fired power plant, and steam is a main kind of drying heat source. In conventional pre-dried lignite-fired power system, the steam extraction of regenerative system is led to the dryer directly. The steam extraction must be used by the dryer after throttling, if the energy mismatch exists between the supply of steam extraction and the need of dryer. Two systems of energy supply for the dryer, that the energy of the steam extraction is supplied to the dryer via compressor or ejector, were proposed in this paper to further increase the energy utilization efficiency. These systems were thermodynamic analyzed, and the electric generation efficiencies of these systems were compared. The energy saving boundary was gotten.

关键词： Thermodynamics Lignite pre-drying Compressor Ejector

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Research on the two-phase flow and separation mechanism in the oil-gas cyclone separator

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IOP Conference Series: Materials Science and engineering 2015年第1期90卷

作者： L Z Wang X Gao J M Feng X Y Peng School of Energy and Power Engineering Xi'an Jiaotong University Xi'an 710049 China State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049China

The cyclone separator has attracted increasing attention due to its small size, rapid construction and high separation efficiency. This study investigated its gas-liquid two-phase flow and separation characteristics experimentally and numerically. A numerical model of two- phase flow in the cyclone separator was proposed using the Euler-Lagrange method. The distribution of pressure, tangential and axial velocity in the gas-phase flow field was obtained, and the oil droplet movement was traced. Separation efficiency was also studied experimentally, and the diameter distributions of oil droplets at the inlet and the outlet of the separator were measured by a Malvern laser particle size analyser to verify the simulation model. Based on high-speed photography technology, the oil film distribution and flow pattern on the wall of the cyclone separator were visualised. The variation of oil-gas two-phase flow in the cyclone separator was compared under various inlet flow rates. Based on the results, an improved structure was proposed, and the performance of the improved separator was investigated experimentally.

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Preliminary study of coupling CFD code FLUENT and system code RELAP5

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Annals of Nuclear Energy 2014年 73卷 96-107页

作者： Wei Li Xiaoli Wu Dalin Zhang Guanghui Su Wenxi Tian Suizheng Qiu Department of Nuclear Science and Technology State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an 710049 China

The present paper discusses a coupling strategy of the 3D (three-dimensional) computational fluid dynamics (CFD) code ANSYS-FLUENT with the best estimate 1D (one-dimensional) thermal–hydraulic system code RELAP5/MOD3.1. Preliminarily, by using DLL (Dynamic Link Library) technology and FLUENT UDF (User Defined Functions), an explicit coupling method expected to be able to support the analysis of multi-purpose thermal–hydraulic phenomena in nuclear reactor systems has been developed. Calculations for two test cases using the coupled FLUENT/RELAP5 code have been carried out to test and demonstrate the coupling capability: (i) the first one consisting of single-phase water transient flow in a square straight tube with well controlled mass flow rates; (ii) the second one illustrating the process of single-phase water flow in a system including two closed loops and one vessel, on which loss of loop water flow due to pump trip and increase of loop water temperature are studied. Both reasonable 1D systematic behaviors and 3D distribution information are naturally obtained for the test cases. Besides, a study of a highly transient experiment problem, i.e. Edwards–O’Brien pipe blowdown problem, has been performed by using the coupled FLUENT/RELAP5 code. The results are compared with standalone RELAP5 calculation and available experimental data, which shows the coupled FLUENT/RELAP5 code’s acceptable potential for the capability of analyzing either simple single-phase or complex two-phase flow problem.

关键词： Explicit coupling method DLL FLUENT RELAP5

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The development of Module In-vessel degraded severe accident Analysis Code MIDAC and the relevant research for CPR1000 during the station blackout scenario

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Progress in Nuclear Energy 2014年 76卷 44-54页

作者： Jun Wang Wenxi Tian Yapei Zhang Lie Chen Longze Li Luteng Zhang Yukun Zhou Guanghui Su Suizheng Qiu State Key Laboratory of Multiphase Flow in Power Engineering Department of Nuclear Science and Technology Xi'an Jiaotong University Xi'an 710049 China

To meet the domestic demand of software autonomous scheduling, Xi'an Jiaotong University had developed MIDAC (a Module In-vessel degraded severe accident Analysis Code) which can not only analyze the processes of in-vessel severe accident, but also provide the related results of each one. This code was composed of five modules: the early behavior module, the core degradation module, the debris bed module, the melting materials IVR module and the connecting module. In this paper, the basic mathematic-physical models of those modules were briefly introduced. Then, the CPR1000 station blackout scenario severe accident was set as an example to calculate the primary system thermal-hydraulic transient, the core degradation and the debris behavior, as well as the creep rupture of heat structures in primary loop pressure boundary. At last, the accuracy of MIDAC was verified in partial comparison with SCDAP/RELAP5 in primary system thermal-hydraulic transient analyzing part.

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MAAP5 simulation of the PWR severe accident induced by pressurizer safety valve stuck-open accident

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Progress in Nuclear Energy 2014年 77卷 141-151页

作者： Longze Li Yapei Zhang Wenxi Tian Guanghui Su Suizheng Qiu State Key Laboratory on Power Engineering and Multiphase Flow School of Nuclear Science and Technology Xi’an Jiaotong University Xi'an 710049 China

The Modular Accident Analysis Program version 5 (MAAP5) is a computer code that can simulate the response of light water reactor power plants during severe accident sequences. The present work aims to simulate the severe accident of a typical Chinese pressure water reactor (PWR) with MAAP5. The pressurizer safety valve stuck-open accident is essentially a small break loss-of-coolant accident (SBLOCA), which becomes one of the major concerns on core melt initiating events of the PWR. Six cases with different assumptions in the pressurizer (PZR) safety valves (SVs) stuck-open accident stuck open accident were analyzed for comparison. The results of first three cases show that the severe accident sequence is correlated with the number of the stuck open valve . The primary system depressurized faster in a more SVs stuck open case, and the consequences in which is hence slighter. The remaining 3 cases along with the case 2 were then analyzed to study the effect of operator intervention to the accident. The results show that the auxiliary feed water (AFW) is effective to delay the core degradation and hence delayed the finally system recovery. The high pressure injection (HPI) operation and manually opening the steam generator (SG) SVs are effective to mitigate this kind of severe accident. The results are meaningful and significant for comprehending the detailed process of PWR severe accident, which is the basic standard for establishing the severe accident management guidelines.

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Li-DOPED CERIUM TERNARY OXIDE IN CO2-SPLITTING VIA SOLAR THERMOCHEMICAL CYCLE

Li-DOPED CERIUM TERNARY OXIDE IN CO2-SPLITTING VIA SOLAR THE...

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10th IUPAC International Conference on Novel Materials and their Synthesis NMS-X(IUPAC第十届新材料及其合成国际会议)

作者： YOUJUNLU CHUNLEI ZHANG LIYA ZHU State Key Laboratory of Multiphase Flow in Power Engineering Xi ''an Jiaotong UniversityXi ''an710049China

Ceria-based oxides have been wildly investigated for thermochemical two-step CO_2-splitting cycle. Among various dopants, cations with small ionic radius and/or multi-valence have shown obvious advantage and are believed to modify ceria in different way. Considering this, CeO_2 doped with both Li and transition metal (Ni, Fe, Cr) were synthesized via sol-gel method and tested for their CO_2-dissociation performance. The cycle proceeded at the reduction temperature of 1773K through a ramp rate of 10K/min and the oxidation temperature of 1273K with a isothermal environment. Ce_(1-x)Li_xO_y(x=0,0.025,0.05,0.075,0.1) were tested at first. Ce_(0.975)Li_(0.025)O_y exhibited the best performance with the highest rate and yield of CO(5.23 mL·g-1). Analysis shows that small radius and low valence of Li~+ lead to lattice disorder and high O~(2-) diffusion rate, which could enhance the Ce~(4+) reduction. Transition metal oxides (MO_x, M=Ni, Fe, Cr) were then added to Ce_(0.975)Li_(0.025)O_y, and among them, Ce_(0.935)Ni_(0.04)Li_(0.025)O_y exhibited the best performance with the highest rate and yield of CO(5.96 mL·g-1). XPS analysis indicates that Ni~(2+) with better redox property could promote the reduction of Ce~(4+). Meanwhile Ce_(0.935)Ni_(0.04)Li_(0.025)O_y, and Ce_(0.955)Ni_(0.02)Li_(0.025)O_y also exhibited excellent performance. For the reduction step, nonisothermal kinetics analysis was performed and it turns out that the reduction process can be well discribed by shrinking core model. As for CO_2 splitting reaction, master plot method was used to determine the mechanism. Results indicate that the surface chemical reaction seem to be the controlling step.

关键词： ternary cerium oxide thermochemical cycle CO2-splitting Li

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Numerical and Experimental Analysis of Two Phase flow in Ejector

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Energy Procedia 2014年 61卷 1298-1301页

作者： Weixiong Chen Chaoyin Shi Mengqi Hu Daotong Chong Jinshi Wang Junjie Yan State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an Shaanxi 710049 P.R. China

When the ejector was applied in the natural gas exploitation and sea water desalination industries, the ejector always operated on the two phase operation, because of the primary fluid or the induced fluid usually companying some water inside. The water inside the primary and induced gas will affect the ejector performance. In the present study, the experimental and CFD methods were used to investigate the two phase flow inside the ejector, when the water was injected into the induced flow. The results show that: when the water was injected into the induced flow, the experimental results decreased, as well as numerical results. The numerical results agreed with the experimental data, with the maximum deviations less than 20% for critical mode and less than 40% for sub-critical mode.

关键词： Ejector Entrainment ratio Back pressure Two phase flow

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An 1-D model for species crossover through the membrane in all-vanadium redox flow batteries 15

An 1-D model for species crossover through the membrane in a...

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15th International Heat Transfer Conference, IHTC 2014

作者： Lei, Yuan Zhang, Baowen Bai, Bofeng Zhao, Tianshou State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University 28 Xianning West Rd. Beilin District Xi'an710049 China Department of Mechanical Engineering Hong Kong University of Science and Technology Clear Water Bay Kowloon Hong Kong

Membrane, as a key component in all-vanadium redox flow batteries, plays the role of conducting the current and isolating the solutions between the anode and cathode electrodes. Both functional groups and charge numbers of membranes influence the performance of the battery. However, in simulating the species crossover through the membrane conventional models take account of mass transfer with the effect of functional groups in the membrane on crossover neglected. In this work, we propose an 1-D model for the membrane region of all-vanadium redox flow battery with the effect of functional groups considered. The model is formulated based on the conservation equations for charge and mass. Donnan potentials at the interfacial regions between membrane and electrodes are modeled, where the conditions are non-electrically neutral. The effects of various factors, including the state of charge, the number of functional groups and the applied current on species crossover are studied. It is shown that there exists a significant jump in electric potential and ion concentrations at the interfacial regions between membrane and electrodes. For a cation membrane, the concentrations of cations at the membrane side in the interfacial region are higher than those at the electrode side, while those of anions opposite. With more charges in the cation exchange membrane, the fluxes of vanadium ions crossover through the membrane are larger, leading to a lower efficiency. The model not only helps shed light into the mechanism of species crossover through the membrane, but also provides a tool to optimize the membrane design for all-vanadium flow batteries.

关键词： Membranes

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Numerical simulation of hemodynamics in portal vein with thrombosis by computational fluid dynamics

Numerical simulation of hemodynamics in portal vein with thr...

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作者： Wang, Xinkai Li, Guojie Chen, Bin Pu, Yansong Nie, Peng Li, Xiao Li, Zongfang Su, Kai State Key Laboratory of Multiphase Flow in Power Engineering Xi'An Jiaotong University Xi'an710049 China Department of General Surgery Second Affiliated Hospital Xi'An Jiaotong University Xi'an710004 China Huaihe Hospital of Henan University Kaifeng475000 China

Portal vein thrombosis (PVT) is an important complication that is associated with cirrhotic portal hypertension. The etiology is as yet unclear but could be closely related to the hemodynamics of the portal vein system. This paper investigated the hemodynamics in the portal vein model, both with and without thrombosis, as well as the effect of obstructions on the hemodynamics of the portal vein system using the computational fluid dynamics (CFD) method. PVT can probably develop in the inlets of the portal vein as well as the left/right branches of the portal vein because the distribution of wall shear stress satisfies the conditions for PVT formation based upon the simulation of the hemodynamics in the normal portal vein model. According to the above results, geometric models for a portal vein with a thrombus were constructed and the influence of different degrees (26%, 39%, 53% and 64%) of obstructions was studied. In the model with the maximum obstruction (64% blocked), the maximum velocity of portal vein (PV) increased up to twice than in the model without thrombosis, and the maximum wall shear stress of PV in the model with thrombosis (64% blocked) increased up to 9.4 Pa, whereas it was only 1.9 Pa in the model without thrombosis (nearly one fifth of the maximum wall shear stress). Excessive wall shear stress may cause mechanical damage to the blood vessels and induce physiological changes. © 2014 World Scientific Publishing Company.

关键词： Computational fluid dynamics

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Novel doped barium cerate-carbonate composite electrolyte material for low temperature solid oxide fuel cells

Novel doped barium cerate-carbonate composite electrolyte ma...

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作者： Hei, Yuanfei Huang, Jianbing Wang, Cheng Mao, Zongqiang International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power Engineering Xi'An Jiaotong University Xianning West Road No. 28 Xi'an 710049 China Institute of Nuclear and New Energy Technology Tsinghua University Beijing 100084 China

A composite of a perovskite oxide proton conductor (BaCe 0.7Zr0.1Y0.2O3-δ, BCZ10Y20) and alkali carbonates (2Li2CO3:1Na2CO 3, LNC) is investigated with respect to its morphology, conductivity and fuel cell performance. The morphology shows that the presence of carbonate phase improves the densification of oxide matrix. The conductivity is measured by AC impedance in air, nitrogen, wet nitrogen, hydrogen, and wet hydrogen, respectively. A sharp increase of the conductivity at certain temperature is seen, which relates to the superionic phase transition at the interface phases between oxide and carbonates. Single cell with the composite electrolyte is fabricated by dry-pressing technique, using nickel oxide as anode and lithiated nickel oxide as cathode, respectively. The cell shows a maximum power density of 957 mW cm-2 at 600 °C with hydrogen as the fuel and oxygen as the oxidant. The remarkable proton conductivity and excellent cell performance make this kind of composite material a good candidate electrolyte for low temperature solid oxide fuel cells (SOFCs). © 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

关键词： Nickel oxide

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