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2009 Asia-Pacific power and Energy engineering Conference, APPEEC 2009

作者： Jiabin, Fang Jinjia, Wei Xunwei, Dong Yueshe, Wang State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an China

ISBN: (纸本)9781424424870

One of the most important components of solar thermal power system is the solar central receiver, which performance is in direct relation to the efficiency of the whole power generation system. The calculation of internal surface heat flux and thermal efficiency of receiver therefore plays a very important role in receiver design. A calculation method of heat loass of a cavity receiver is put forward in this paper. The first step of this method is to use the Monte Carlo method to simulate the track of solar beam and compute surface heat flux inside the receiver. The second step is to employ the correlations of flow boiling heat transfer to figure out the convective heat transfer coefficient inside the tubes and then the wall temperature of the boiling tubes laid inside the receiver. The last step is to simulate the air flow field inside the receiver to calculate convective thermal loss of the receiver. As every step can not be independently done, all steps are coupled and an iterative scheme is needed. Internal surface heat flux and thermal efficiency of the receiver can be finally gained with this method, and the result can provide theoretical guide for receiver design. © 2009 IEEE.

关键词： Monte Carlo methods

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Numerical investigation of edl effects on the flow characteristics of polar fluids in rectangular microchannels

Numerical investigation of edl effects on the flow character...

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4th International Conference on Nanochannels, Microchannels and Minichannels, ICNMM2006

作者： Li, Zhuo Tang, Gui-Hua He, Ya-Ling Tao, Wen-Quan State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi'an Jiaotong University China

ISBN: (纸本)0791847608

Recently, a large number of experiments have been conducted to examine the applicability of Navier-Stokes equations to predict the friction factor for the laminar flow of polar fluids in microchannels. However, significant discrepancies still exist between various results. In order to investigate the effect of electric double layer on the pressure-driven flow of polar fluid in smooth rectangular microchannels and to reveal whether continuum model can still be applied, numerical investigations are conducted in this paper. The simulated microchannels are made of silicon engraved substrate with Pyrex cover, and the measured relative roughness of channels is less than 0.5%. Deionized water and tap water with different ion concentration and electrical conductivity are used as the working fluid. The governing equations include the two-dimensional, non-linear Poisson-Boltzmann equation, the modified N-S equation and the electric field Ez equation. The steady state electric field E z equation is coupled with the momentum equation. The FVM (finite volume method) is adopted to discretize the governing equations. The non-uniform grid systems 152×102 is applied and the Reynolds number ranges from 0.1 to 300. Good agreements are achieved between the numerical results and the experimental data available in the literature. The effects of electrical potential, fluid ion concentration, electrical conductivity and the channel dimensions on the EDL profile, and the electroviscous effect and the friction coefficient are presented in detail. The simulation results reveal that the Debye thickness depends on ion concentration greatly. Only when the ratio of Dh/δ (the ratio of channel hydraulic diameter to the Debye thickness) is low, the electroviscous effect should be considered. According to the experimental conditions, the numerical results show that if the ratio of Dh/δ is greater than 15, the predicted friction factors agree well with the macroscale classical law, and the disparities

关键词： Channel flow

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Experimental and modeling study of low temperature ignition characteristics of methylcyclohexane/ethanol binary fuel 12

Experimental and modeling study of low temperature ignition ...

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12th Asia-Pacific Conference on Combustion, ASPACC 2019

作者： Liu, Yang Tang, Chenglong Huang, Zuohua State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an China

The purpose of this work is to investigate the effect of ethanol blending into methylcyclohexane during the ignition at low temperatures. The ignition delay times of the binary fuels with ethanol blending ratio varied from 0% to 100% at = 1.0, Pc = 20 bar, Tc = 680 - 890 K were measured with the rapid compression machine, and the mechanism of Bissoonauth et al. (Proc Combust Inst 2018) well predicts the experimental results. Based on the high quality of the model, the effects of ethanol blending on the pressure and heat release are studied. Both of the maximum pressure and the heat release during the ignition decrease with the ethanol blending ratio increases. The interaction of MCH and ethanol happens in the competition of active radicals like OH, and MCH dominates the ignition process as it occupies about two thirds of the OH to form the fuel radical. © Asia-Pacific Conference on Combustion, ASPACC *** right reserved.

关键词： Ethanol

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Au@SiO_2 core/shell nanoparticle-decorated TiO_2 nanorod arrays for enhanced photoelectrochemical water splitting

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Chinese Science Bulletin 2014年第18期59卷 2191-2198页

作者： Jianan Chen Miao Yu Yuhao Wang Shaohua Shen Meng Wang Liejin Guo International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power EngineeringXi’an Jiaotong University School of Chemical Engineering and Technology Harbin Institute of Technology

To improve the separation efficiency of photoinduced charge carries,Au@SiO2nanoparticles(NPs)with core–shell structure were loaded onto the surface of TiO2nanorods grown on fluorine-doped tin oxide substrate by a facile two-step *** resulted Au@SiO2/TiO2photoanodes were characterized by X-ray diffraction,scanning electron microscopy,transmission electron microscopy,as well as photoelectrochemical *** with pristine TiO2nanorod film,the Au@SiO2/TiO2films showed remarkable enhancement in photoelectrochemical water splitting,with incident photonto-current conversion efficiency increasing from 31%to37%at 380 nm at 0.7 V versus saturated calomel *** could be interpreted by the effect of metallic surface plasmon resonance of Au@SiO2NPs,which would generate an intense electromagnetic field with spatially nonhomogenous distributed *** a result,the charge carriers generated in the near-surface region of TiO2nanorods could be easily *** modification method based on the effect of metallic surface plasmon resonance for promoted charge carrier separation provides a promising way to develop semiconductor photoelectrodes with high solar water-splitting performance.

关键词：二氧化硅纳米粒子二氧化钛纳米棒电解水表面等离子体共振效应纳米颗粒金属 TiO2薄膜

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Base-or acid-assisted polystyrene plastic degradation in supercritical CO_(2)

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Waste Disposal and Sustainable Energy 2023年第2期5卷 165-175页

作者： Yanbing Liu Jinwen Shi Liuhao Mao Bingru Lu Xing Kang Hui Jin International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power EngineeringXi’an Jiaotong University28 West Xianning RoadXi’an710049ShaanxiChina

Plastic has caused serious"white pollution"to the environment,and the highly inert characteristics of plastic bring a major challenge for *** fluids have unique physical properties and have been widely used in various *** this work,supercritical CO_(2)(Sc-CO_(2))with mild conditions was selected and assisted by NaOH/HCl solution to degrade polystyrene(PS)plastic,and the reaction model was designed using response surface methodology(RSM).It was found that,regardless of the types of assistance solutions,the factors affecting PS degradation efficiencies were reaction temperature,reaction time,and NaOH/HCl *** the temperature of 400℃,time of 120 min,and base/acid concentration of 5%(in weight),0.15 g PS produced 126.88/116.99±5 mL of gases with 74.18/62.78±5 mL of H2,and consumed 81.2/71.5±5 mL of CO_(2).Sc-CO_(2)created a homogeneous environment,which made PS highly dispersed and uniformly heated,thus promoting the degradation of ***,Sc-CO_(2)also reacted with the degradation products to produce new CO and more CH_(4)and C_(2)H_(x)(x=4,6).Adding NaOH/HCl solution not only improved the solubility of PS in Sc-CO_(2),but also provided a base/acid environment that reduced the activation energy of the reaction,and effectively improved the degradation efficiencies of *** short,degrading PS in Sc-CO_(2)is feasible,and better results are obtained with the assistance of base/acid solution,which can provide a reference for the disposal of waste plastics in the future.

关键词： Plastic degradation Polystyrene Supercritical CO_(2) NaOH HCl

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Experimental study on a linear concentrating solar photovoltaic/thermal system

Experimental study on a linear concentrating solar photovolt...

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26th International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems, ECOS 2013

作者： Ma, Qiuming Cao, Fei Zhao, Liang State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an China

A set of solar photovoltaic and thermal combined (PV/T) system is installed and tested in the present study. The PV/T system is designed and constructed by integrating coiled-channel flat-plate collectors with polycrystalline silicon PV modules. The linear Fresnel lens acts as the concentrator. Three systems, i.e. the non-cooling PV system, the non-concentrating PV/T system and the concentrating PV/T system, are tested and analyzed. Experimental results show that a high thermal and electrical combined efficiency, over 65%, is achieved by the PV/T system. Water in the flat plate can significantly decrease the PV module temperature and improve the electricity-conversion efficiency. Comparing with the non-concentrating PV/T system, the concentrating PV/T system can increase the total utilization of solar energy.

关键词： Solar energy

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Dynamic simulation of coal-fired power plant integrated with trough solar collector operating in parallel with high pressure heaters

Dynamic simulation of coal-fired power plant integrated with...

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2019 Canadian Society for Civil engineering Annual Conference, CSCE 2019

作者： Yan, Hui Li, Xin Liu, Ming Chong, Daotong Yan, Junjie State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an China

ISBN: (纸本)9780791883747

Solar-aided coal-fired power plant (SACFPP) is a costeffective approach to overcome solar energy intermittency. SACFPPs frequently operate in dynamic processes due to power load and solar energy fluctuations. This study investigated the dynamic characteristics of SACFPPs;such characteristics are important for flexibility evaluation and control system design. The SACFPP used in this study was based on a 660 MW coalfired power plant, and a trough collector system (TCS) operates in parallel with high pressure (HP) heaters. After model development and validation, the dynamic performance of the SACFPP was analyzed under four load ratios of power plant, with disturbances of two parameters: direct normal irradiance (DNI) and mass flowrate ratio to TCS. The performance was also compared with three parallel TCS connection modes. Results showed that the magnitude and response time for power variation under DNI disturbance increased with load ratio. With 500 W/m2 DNI step increments, power increased by approximately 18.4, 21.2, 24.7, and 29.8 MW in 2200, 2330, 2550 and 2620 s at 70%, 80%, 90%, and 100% load ratios, respectively, when all the HP heaters were replaced. The serial number and the number of HP heaters replaced also increased the power variation and response time. Under mass flowrate ratio to TCS increase disturbance, the power rapidly changed to its maximum and then slowly decreased, but the variation value depended on the load ratio. Copyright © 2020 ASME.

关键词： Coal fired power plant

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Experimental and modeling study of n -butanol oxidation at high temperature

Experimental and modeling study of n -butanol oxidation at h...

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作者： Zhang, Jiaxiang Wei, Liangjie Man, Xingjia Jiang, Xue Zhang, Yingjia Hu, Erjiang Huang, Zuohua State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an China

Ignition delay times of n-butanol/oxygen diluted with argon were measured behind reflected shock waves. Experiments were carried out in the temperature range 1200-1650 K, at 2 and 10 atm, and at equivalence ratios of 0.5, 1.0, and 2.0. Correlations of ignition delay times were constructed on the basis of measured data through multiple linear regression. A modified kinetic model for the oxidation of n-butanol at high temperature was developed, based on previous models by adding and modifying some key reactions. The modified model shows good prediction of the measured data under all measured conditions. This model was also validated against jet-stirred reactor (JSR) data obtained from the literature, and fairly good agreement was observed. A fair improvement on the simulation of aldehydes (acetaldehyde and butyraldehyde) was found compared to the original model. Finally, reaction pathway and sensitivity analysis indicate that the H-abstraction reactions play a dominant role in the consumption of n-butanol, while unimolecular decomposition reactions become more important with increasing temperature. High-level accurate investigation of the rate constants of H-abstraction reactions and unimolecular decomposition reactions is required to further improve n-butanol oxidation kinetics. © 2012 American Chemical Society.

关键词： Oxidation

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Research on the effects of diluents and dilution ratios on laminar burning velocities and flame instabilities of hydrogen flame 11

Research on the effects of diluents and dilution ratios on l...

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11th Asia-Pacific Conference on Combustion, ASPACC 2017

作者： Lu, Xin Hu, Erjiang Li, Xiaotian Huang, Zuohua State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an China

Laminar burning velocities and flame instabilities of H2/O2/diluents mixture were studied at initial pressure of 0.3 MPa, initial temperature of 373 K and equivalence ratio of 1.0. The He diluted mixtures have the largest laminar burning velocities and the N2 diluted mixtures have the smallest, while He diluted mixtures have the largest mole fraction of H and OH radical and N2 diluted mixtures have the smallest. And laminar burning velocities fall when the dilution ratio rises, due to the mole fractions of H and OH radical fall with increasing dilution ratio. The cellular structure appeared on both N2 and Ar diluted mixture, while only wrinkles grew on He diluted mixtures. When dilution ratio rose, the appearance of cellular structure deferred. Thus, He diluted mixtures are more stable than N2 and Ar diluted mixtures, and higher dilution ratios restrain the flame instabilities. © 2017 Combustion Institute. All rights reserved.

关键词： Hydrogen

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Surface sulfurization activating hematite nanorods for efficient photoelectrochemical water splitting

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Science Bulletin 2019年第17期64卷 1262-1271页

作者： Lianlian Mao Yu-Cheng Huang Yanming Fu Chung-Li Dong Shaohua Shen International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China Department of Physics Tamkang University Tamsui 25137 Taiwan China

Surface treatment is an effective method to improve the photoelectrochemical(PEC) performance of photoelectrodes. Herein, we introduced a novel strategy of surface sulfurization to modify hematite(a-Fe2 O3)nanorods grown in an aqueous solution, which triggered encouraging improvement in PEC *** comparison to the solution-grown pristine a-Fe2 O3 nanorod photoanode that is PEC inefficient and always needs high temperature(>600 °C) activation, the surface sulfurized a-Fe2 O3 nanorods show photocurrent density increased by orders of magnitude, reaching 0.46 mA cmà2 at 1.23 V vs. RHE(reversible hydrogen electrode) under simulated solar illumination. This improvement in PEC performances should be attributed to the synergy of the increased carrier density, the reduced surface charge carrier recombination and the accelerated water oxidation kinetics at the a-Fe2 O3/electrolyte interface, as induced by the incorporation of S ions and the formation of multi-state S species(Fe-Sx-Oy) at the surface of a-Fe2 O3 nanorods. This study paves a new and facile approach to activate a-Fe2 O3 and even other metal oxides as photoelectrodes for improved PEC water splitting performances, by engineering the surface structure to relieve the bottlenecks of charge transfer dynamics and redox reaction kinetics at the electrode/electrolyte interface.

关键词： Photoelectrochemical Water splitting Hematite nanorods Photoanodes Surface sulfurization

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