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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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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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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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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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A numerical study of the MPS method for simulating non-newtonian free surface flows

A numerical study of the MPS method for simulating non-newto...

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23rd International Congress of Theoretical and Applied Mechanics

作者： Hao Xiang Bin Chen State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University

The moving particle semi-implicit method(MPS) is a Lagrangian particle method which is suitable for simulating surface flows *** paper couples the non-Newtonian model with the MPS method by treating the non-Newtonian ... 详细信息

关键词： A numerical study of the MPS method for simulating non-newtonian free surface flows

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Study on Performance of Double Helical Capacitance Probe for Water Fraction Measurement in multiphase flow

Study on Performance of Double Helical Capacitance Probe for...

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The 7th International Symposium on Measurement Techniques for multiphase flows

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

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 *** 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 *** electrostatic field of the probe is preliminarily analyzed referred to stratified flow of air-water two-phase flow *** 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 *** 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 *** by using circuit simulation method,the numerical calculated lumped capacitance is transferred to voltage output through the circuit used in the *** relationship between voltage and water fraction of calculated and experimental result are compared in order to test the reasonableness of the *** results show that at high water fraction,the difference between numerical and measured data agrees very well.

关键词： Numerical simulation water fraction capacitance probe multiphase flow

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An Experimental Study of on-line Measurement of Water Fraction in Gas-Oil-Water Three-Phase flow

An Experimental Study of on-line Measurement of Water Fracti...

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The 7th International Symposium on Measurement Techniques for multiphase flows

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

Gas-oil-water two- or three-phase flow is widely encountered in industry,such as petroleum chemical industry,bio-chemicals,food chemicals,and mineral engineering and energy *** kinds of on-line measurement technique,which are double-ring conductance sensor and double-helical capacitance sensor,for water fraction in oil-water two-phase flow and gas-oil-water three-phase flow were developed in this *** calibration results shows that the responses of the two sensors are good enough as the variation of water *** on the other hand,it is possible that the oil and the gas regard as one phase in gas-oil-water three-phase flow by using double-helical capacitance sensor,and the ratio between water and gas has no effect with the output *** range of water fraction which can be measured becomes bigger and bigger because of the using of new *** the capacitance sensor is better enough to measure water fraction in the three phases *** dynamic experiment,because of phase inversion phenomenon between oil and water,the conductance sensor outputs poorly,however the capacitance sensor performs somewhat *** reason for the error using capacitance sensor is the edge effect of the *** experiment results show that the edge effect of the double-helical capacitance sensor causes that the output is smaller so that the measuring water fraction is a litter larger than the actual *** when the variation of water fraction is above 10%,the edge effect of capacitance sensor can be almost *** the contrary,when the variation of water fraction is below 10%,the edge effect is so lager than the results above that it cannot be ***,the double-helical capacitance probe is more suitable for measuring water fraction in slug flow and oil-water emulsion,in which the results agree better with static calibration than that in bubble flow.

关键词： Double-ring conductance sensor Double-helical capacitance sensor Gas-oil-water three-phase flow Water fraction Measurement technique

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CaTaO2N-CaZrO3 solid solution: Band-structure engineering and visible-light-driven photocatalytic hydrogen production

CaTaO2N-CaZrO3 solid solution: Band-structure engineering an...

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作者： Wu, Po Shi, Jinwen Zhou, Zhaohui Tang, Wendong Guo, Liejin International Research Center for Solar-Hydrogen Renewable and Clean Energy State Key Laboratory of Multiphase Flow in Power Engineering Xi'An Jiaotong University 28 West Xianning Street Xi'an 710049 China

A series of CaTaxZr(1-x)O(3-x)N x solid solutions were successfully synthesized through nitriding precursors prepared by the polymerized complex method. The physicochemical properties of these multicomponent semiconductors were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), N2 adsorption-desorption isotherms, UV-visible optical absorption spectra (UV-Vis) and density functional theory (DFT) calculations. The diffraction peaks in XRD patterns gradually shifted to higher angles as x increased, indicating that CaTaxZr(1-x)O(3-x)Nx solid solutions had been formed. The absorption edges in UV-Vis spectra red-shifted monotonically as x increased, demonstrating that the band gap of the prepared photocatalysts could be precisely controlled with the adjustment of compositions. The solid solutions rendered photocatalytic H2 evolution from a formic acid aqueous solution under visible-light irradiation. The narrow band gap, sufficient crystallization, enough pore volume and large specific surface area resulted in the best photocatalytic activity of CaTa 0.8Zr0.2O2.2N0.8. Highlights: CaTaxZr(1-x)O(3-x)Nx solid solutions were synthesized by PC method. Absorption edges red-shifted monotonically as x increased. CaTa0.8Zr0.2O2.2N0.8 showed best H2 evolution. Band gap and specific surface area were both key factors. © 2012 Hydrogen Energy Publications, LLC.

关键词： Solid solutions

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Experimental study of two-phase flow instability of vertical parallel rifled tube with different sizes at low-mass flow rate

Experimental study of two-phase flow instability of vertical...

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作者： Deng, Zhian Luo, Yushan Wang, Haijun Chen, Tingkuan State Key Laboratory of Multiphase Flow in Power Engineering Xi'An Jiaotong University No. 28 Xianning Road Xian China Xi'An Shiyou University 2 Dianzi Road Xian 710065 China

Under certain operating conditions, two-phase flow oscillations can occur and induce undesired problems such as system control, vibration, tube burn-out, etc. Therefore, it is essential to avoid and control two-phase flow instabilities when designing and operating equipments that are susceptible to such effects. The authors conducted an experimental study of vapor-liquid two-phase flow instabilities in vertical parallel tubes for a high-pressure vapor-water loop. Two types of vertical parallel rifled tubes (31.8 mm OD × 6 mm thickness, and 28.6 mm × 5.8 mm) were used as the tube sections. During experimentation, pressure-drop and density-wave type oscillations appeared, and the influence of the inlet pressure, mass flow rate, and inlet subcooling on the two-phase flow instability in both types of vertical parallel-connected tubes was studied. The results showed that with an increase in the inlet pressure and mass flow rate, the boundary thermal load of the pressure-drop and density-wave oscillations increased. As the inlet pressure increased, so the boundary quality of the pressure-drop and density-wave oscillations occurring in both types of the rifled tubes also increased. Experiments showed that under the same operating conditions, the stability of the 31.8 × 6 mm rifled tube is better than the 28.6 × 5.8 mm rifled tube. For the 31.8 × 6 mm rifled tube, the occurrence of the boundary quality of the pressure-drop type oscillation increased with the increasing mass flow rate. However, for the 28.6 × 5.8 mm rifled tube, the occurrence of the boundary quality of the pressure-drop oscillation first increased and then decreased with an increasing mass flow. © 2011 Curtin University of Technology and John Wiley & Sons, Ltd.

关键词： Pressure drop

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