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Hydrodynamic analysis and calculation of metal temperature distribution in spiral water wall of ultra supercritical tower boiler

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AIP Conference Proceedings 2013年第1期1547卷

作者： Chengwu Shen Dong Yang Danhua Yao Yufeng Zhu Xueyuan Xu State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University China Shanghai Boiler Works Ltd. Shanghai China

In this paper, the spiral water wall system of a 1000MW ultra supercritical tower boiler is simplified as a network system, consisting of circuits, pressure grids and connecting tubes. The establishment of the mathematical model for calculating the mass flux distribution and metal temperature in water wall is based on the mass, momentum and energy conservation equations. The water wall flow distribution and temperature profile of the boiler were computed. The result shows that the differences of outlet temperature and mass flux are small in spiral tube water wall at BMCR, 75%BMCR load and 40%BMCR load. The metal temperatures are all in the allowable ranger.

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Influence of nozzle diameter on spray characteristics and surface heat transfer dynamics in cryogen spray cooling for dermatologic laser surgery 12

Influence of nozzle diameter on spray characteristics and su...

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12th International Conference on Liquid Atomization and Spray Systems, ICLASS 2012

作者： Zhou, Zhifu Wang, Rui Wang, Guoxiang Chen, Bin State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China Department of Mechanical Engineering University of Akron AkronOH44325 United States

Cryogen spray cooling (CSC) is an effective method to minimize or even eliminate laser-induced irreversible injury to the epidermis during laser surgery of various cutaneous anomalies such as port wine stain (PWS). This paper conducts an experimental investigation of the atomization characteristics and surface heat transfer dynamics in pulsed cryogen spray cooling of epidermis by R-134a, focusing on the effect of the nozzle diameter. A Phase Doppler Particle Analyzer (PDPA) is used to measure the distributions of the diameter and velocity of the liquid droplets in the spray. The temperature of liquid droplets in spray is measured by a micro-thermocouple with a bead diameter of around 100 μm. A thin-film thermocouple of 2 μm thickness is deposited directly onto the epoxy resin substrate (which serves as the skin phantom) to monitor the variation of the surface temperature induced by the CSC. The dynamic variation of the surface heat flux and convective heat transfer coefficient in CSC can then be quantified from the measured temperatures using the Duhamel's theorem. Four nozzles with diameter ranging from 0.48 mm to 1.75 mm have been used and a systematic parametric study was conducted to illustrate the effect of nozzle diameter on spray characters and surface heat transfer dynamics. It is found that the nozzle with the smaller diameter produces finer liquid droplets and larger droplets velocity than that with the larger diameter. Furthermore, the temperature of droplets from the smaller diameter nozzle decreases faster with the spray distance. Analysis of surface heat transfer indicates that the size and velocity of liquid droplets in spray has a large effect on surface heat flux and heat transfer coefficient, with large droplets leading to high heat flux at the cooling surface. In addition, a criterion is proposed to evaluate the cooling efficiency of a given nozzle based on the variation of heat extraction from the cooling surface within the effective cooling time

关键词： Heat transfer coefficients

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Vertically oriented TiO_2 nanotube arrays with different anodization times for enhanced boiling heat transfer

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Science China(Technological Sciences) 2012年第8期55卷 2184-2190页

作者： XU Jia YANG MingJie XU JinLiang JI XianBing Beijing Key Laboratory of Low-Grade Energy Multiphase Flow and Heat Transfer School of Renewable EnergyNorth China Electric Power UniversityBeijing 102206China Laboratory of Advanced Materials Department of Material Science and EngineeringTsinghua UniversityBeijing 100084China

Pool boiling of saturated water on a plain Ti surface and surfaces covered with vertically-oriented TiO2 nanotube arrays(NTAs) has been *** technique of potentiostatic anodization using non-aqueous electrolytes was adopted to fabricate three types of TiO2 NTAs distinguished by their anodization *** to the bare Ti surface,the incipient boiling wall superheat on the TiO2 NTAs was decreased by 11 *** the critical heat flux and heat transfer coefficient of pool boiling on the TiO2 NTAs were higher than those from boiling on a bare Ti *** measured maximum critical heat flux and heat transfer coefficient values were 186.7 W/cm2 and 6.22 W/cm2K,*** performances for the enhancement of heat transfer by the three types of TiO2 NTAs were attributed to the different degrees of deformation in the nanostructure during ***-term performance of the nanomaterial-coated surfaces for enhanced pool boiling showed degradation of the TiO2 NTAs prepared with an anodization time of 3 hours.

关键词： TiO2 nanotube arrays pool boiling heat transfer enhancement deformation of nanostructure

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Study on performance of double helical capacitance probe for water fraction measurement in multiphase flow

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AIP Conference Proceedings 2012年第1期1428卷 120-127页

作者： J. Ye L. J. Guo H. L. Zhou State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an China

A type of capacitance probe performance with two brass electrodes intertwined on the outer wall of insulation pipe like a double helix is investigated numerically in this paper, which can measure water fraction in air-oil-water two or three-phase flow in oil industry. The motivation of this paper is to optimize this kind of probe to improve its electric response and spatial resolution and so a 3-D numerical simulation using finite element method is employed to evaluate the effect of electrodes configuration of this capacitance probe on measuring water fraction in horizontal pipes. The electrostatic field of the probe is preliminarily analyzed referred to stratified flow of air-water two-phase flow regime. Several parameters are considered as main variables which have an important effect on the precision of the probe, such as central angle, position angle and length of the two electrodes. From the electrostatic field analysis, lumped capacitance between the two electrodes is obtained in every different electrode geometry model and the results of each model are compared to each other in order to select a better arrangement of the electrodes that has a better response to water fraction. And by using circuit simulation method, the numerical calculated lumped capacitance is transferred to voltage output through the circuit used in the experiment. The relationship between voltage and water fraction of calculated and experimental result are compared in order to test the reasonableness of the simulation. The results show that at high water fraction, the difference between numerical and measured data agrees very well.

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Electrodeposition of zinc coatings from the solutions of zinc oxide in imidazolium chloride/urea mixtures

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Science China Chemistry 2012年第8期55卷 1587-1597页

作者： ZHENG Yong DONG Kun WANG Qian ZHANG SuoJiang ZHANG QinQin LU XingMei Beijing Key Laboratory of lonic Liquids Clean Process State Key Laboratory of Multiphase Complex SystemsInstitute of Process EngineeringChinese Academy of SciencesBeijing 100190China College of Chemistry and Chemical Engineering Graduate University of Chinese Academy of SciencesBeijing 100049China

To solve the inherent disadvantages in conventional processes for electrodeposition of zinc, it＇s necessary to develop more high-efficiency and environmentally friendly electrolytes. In this work, it was found that the dissolution of ZnO was remarka- bly enhanced in some imidazolium chloride by the addition of urea, and the solubility of ZnO in 1：1 [Amim]C1/urea mixture was as high as 8.35 wt% at 373.2 K. Electrochemical measurements showed that zinc could be readily electrodeposited from the solutions of ZnO. Bright, dense and well adherent zinc coatings with good purity were obtained from 0.6 M solution of ZnO in 1：1 [Amim]C1/urea at 323.2-343.2 K. It＇s expected that the solutions of ZnO in imidazolium chloride/urea mixtures have the potential to replace the traditional electrolytes, especially toxic zinc chloride-based ones for zinc electroplating, as well as preparation of zinc materials.

关键词： electrochemistry electroplating metal oxide zinc deposits ionic liquids

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Experimental and modeling study of the effects of equivalence ratio on the benzene formation chemistry of one-dimensional laminar premixed n-heptane flames

Experimental and modeling study of the effects of equivalenc...

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8th International Conference on Modeling and Diagnostics for Advanced Engine Systems, COMODIA 2012

作者： Chen, Gen Yu, Wu Fu, Jin Huang, Zuohua Yang, Jiuzhong Wang, Zhandong Qi, Fei State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China National Synchrotron Radiation Laboratory University of Science and Technology of China Hefei Anhui 230029 China

In order to gain a better understanding of the soot formation mechanism involved in the combustion process of hydrocarbon fuels, laminar premixed n-heptane flames with different equivalence ratios (1.20, 1.60 and 1.80) are studied by using synchrotron photoionization and molecular-beam mass spectrometry (PI-MBMS) techniques at low pressure(30Torr). To isolate the influence from flame temperature, the composition of unburned mixtures is adjusted such that the temperature profiles are approximately equivalent. Mole fraction profiles of major and intermediate species were derived and compared among different flames. Parallel modeling study based on a modified mechanism is conducted. The predicted mole fraction profiles of concerned species agree reasonably well with experimental measurements. The results show that, as equivalence ratio increases, the equilibrium mole fractions of H2O and CO2 decrease while those of H2 and CO increase, and the concentrations of benzene and toluene and those of C2-C 5 hydrocarbon intermediates increase apparently. The reaction flux analysis indicates that the self-recombination of propargyl radical (C 3H3) and the cross reaction between C3H 3 and allyl radical (a-C3H5) are the dominant pathway leading from small aliphatics to C6H6. The consumption of C6H6 is primarily resulted from the attack by OH and H radicals. The larger amount of C6H6 formed in richer flames should be attributed mainly to the higher concentrations of benzene precursors. In addition, the weakening influence of the OH-attack and O-attack reaction tends to slow down the consumption of C6H 6, which also contributes to the higher C6H6 concentration in the richer flames. Copyright © 2012 by the Japan Society of Mechanical Engineers.

关键词： Benzene

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Three international conferences on ionic liquids held in Beijing in 2012

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Science China Chemistry 2012年第8期55卷 1695-1696页

作者： WANG Qian LU XingMei Beijing Key Laboratory of Ionic Liquids Clean Process State Key Laboratory of Multiphase Complex SystemsInstitute of Process Engineering Chinese Academy of Sciences Beijing 100190 China

Ionic liquids (ILs) have recently received worldwide intense attention as environmentally friendly solvents and become a hot topic in green chemistry. As we know, ILs have been utilized in diverse fields, such as synthesis, catalysis,separa- tion technology, electrochemistry, analytical chemistry, nan- otechnology, and so on, which makes ILs into a separated topic in many native and international conferences. Here we introduce three international conferences, which will be held in Beijing, China soon, for devotees of ILs.

关键词：离子液体国际会议北京环保溶剂绿色化学分离技术分析化学 ILS

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Hydraulic and thermal effects of coke deposition during pyrolysis of hydrocarbon fuel in a mini-channel

Hydraulic and thermal effects of coke deposition during pyro...

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作者： Liu, Zhao H. Bi, Qin C. Guo, Yong Ma, Xue S. Yang, Zhu Q. Yan, Jian G. Hu, Shen L. State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China Science and Technology on Scramjet Laboratory 31st Research Institute of CASIC Beijing 100074 China

Coke deposition in a mini-channel reduced the effective diameter greatly during pyrolysis of hydrocarbon fuel. In the paper, the hydraulic resistance method (HRM) was introduced to quantitatively evaluate the coke deposition. Pyrolysis of hydrocarbon fuel was carried out at fuel temperature up to 725 °C at supercritical pressure of 4 MPa in an electrically heated mini-channel (heated length, 508.0 mm;inner diameter, 2.0 mm;wall thickness, 0.5 mm). The test run was maintained at steady state for 30 min. The post-test coke evaluation by HRM is nondestructive and onboard performed at normal temperature and pressure. Compared with the optical microscope visualization, the HRM was validated to be feasible and effective. Experimental results show that the thickness of coke deposit along the channel, varying from several to about 130 μm, is a function of film temperature (average of the wall and bulk fuel temperature). Contributing to the coke deposition during fuel pyrolysis, the hydraulic resistance continuously increased. However, depending on the deposit thickness, the thermal effects can be contrary. The gully coke nature at high Re turbulent flow and the large deposit thickness as a thermal resistance can dominate to enhance and reduce the heat transfer, respectively. © 2012 American Chemical Society.

关键词： Pyrolysis

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Simultaneous operation of dibenzothiophene hydrodesulfurization and methanol reforming reactions over Pd promoted alumina based catalysts

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Ranliao Huaxue Xuebao/Journal of Fuel Chemistry and Technology 2012年第6期40卷 714-720页

作者： Yaseen, Muhammad Shakirullah, Muhammad Ahmad, Imtiaz Rahman, Ata Ur Rahman, Faiz Ur Usman, Muhammad Razzaq, Rauf Institute of Chemical Sciences University of Peshawar Khyberpukhtunkhwa Pakistan State Key Laboratory of Multiphase Complex Systems Institute of Process Engineering Chinese Academy of Sciences Beijing 100190 China

In the current study simultaneous reactions of hydrodesulfurization (HDS) of dibenzothiophene (DBT) and reforming of methanol in a micro-autoclave reactor were studied over bi-metallic (Co-Mo/Al2O3 and Ni-Mo/Al2O3) and tri-metallic (Pd-Co-Mo/Al2O3 and Pd-Ni-Mo/Al2O3) catalyst systems which were prepared by incipient impregnation method. In situ hydrogen utilization and low Pd loadings were the major targets of this study. For comparison purpose, catalytic activity was separately determined for both the methanol reforming and HDS of DBT reactions as well. Ni based catalysts were confirmed with better activity than Co ones for both the reactions with Pd promoted ones ranking at the top i.e. Pd-Ni-Mo/Al2O3 > Ni-Mo/Al2O3 > Pd-Co-Mo/Al2O3 > Co-Mo/Al2O3 where Pd-Ni-Mo/Al2O3 showed 91% DBT conversion at 380°C and 12 h reaction time. Some of the selected organic additives on catalytic activity were tested for their effect toward HDS reaction which was unique with close relation to their chemical nature. Reaction products were quantitatively and qualitatively analyzed via HPLC and GC-MS techniques respectively which helped in elucidating reaction mechanism.

关键词： Catalyst activity

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All-atom and united-atom simulations of guanidinium-based ionic liquids

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Science China Chemistry 2012年第8期55卷 1573-1579页

作者： LIU XiaoMin ZHANG XiaoChun ZHOU GuoHui YAO XiaoQian ZHANG SuoJiang State Key Laboratory of Multiphase Complex Systems Institute of Process EngineeringChinese Academy of SciencesBeijing 100190China Beijing Salien Computer Co. Building 8Beijing 100083China

Ionic liquids (ILs) have been widely used in separation, catalysis, electrochemistry, etc., and one of the most outstanding characteristics is that ILs can be tailored and tuned for specific tasks. In order to design and make better use of ionic liquids, the structures and properties relationship is indispensable. Both molecular dynamics and Monte Carlo simulations have been proved useful to understand the behavior of molecules at the microscale and the properties of the system. However, the quality of such simulations depends on force field parameters describing the interactions between atoms. All-atom (AA) or the united-atom (UA) force fields will be chosen because of the demand for more exact results or the lower computational cost, respectively. In order to make a systematic comparison of the two force fields, molecular simulations for four kinds of acyclic guanidinium-based ionic liquids (cations: (R2N)2C=N+<, anion: nitric or perchloric acid) were performed based on the AA and the UA force fields in this work. AA force field parameters were derived from our previous work (Fluid Phase Equilib., 2008, 272: 1-7), and the UA parameters were proposed in this work. Molecular dynamics simulation results for the AA and UA force fields were compared. Simulation densities are very similar to each other. Center of mass radial distribution functions (RDFs), site to site RDFs and spatial distribution functions (SDFs) were also investigated to depict the microscopic structures of the ILs.

关键词： all-atom force field united-atom force field molecular simulation ionic liquids

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