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Effects of the turbulence and drag force on heat transfer characteristics in supercritical water fluidized bed

Kung Cheng Je Wu Li Hsueh Pao/Journal of engineering Thermophysics 2014年第12期35卷 2437-2441页

作者： Lü, You-Jun Dong, Xu-Bin Zhang, Tian-Ning State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China

The Eulerian two-fluid model based on Kinetic Theory of Granular flow was used to investigate the effects of the turbulence and drag force on heat transfer characteristics in supercritical water fluidized bed in this paper. Three drag models including Gidaspow, Syamlal-O'Brien and Wen-Yu drag models, and four turbulence models that are three high Renolds number turbulence model: standard κ - Ε, RNG κ - Ε, realizable κ - Ε and a low Renolds number turbulence model, are adopted. The results show that the Gidaspow drag model is the most proper drag model in SCW fluidized bed among three models employed. As for the four turbulence models, the bed-to-wall heat transfer coefficients simulated with the three high Renolds number turbulence models are in a good consistency, and are all larger than that simulated with the low Renolds number turbulence model. RNG κ- Ε turbulence model is the most proper one for the simulation of heat transfer characteristics in SCW fluidized bed with comprehensive considerations. © 2014, Science Press. All right reserved.

关键词： Fluidized beds

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Shock tube study on ignition delay of multi-component syngas mixtures - Effect of equivalence ratio

Shock tube study on ignition delay of multi-component syngas...

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作者： Thi, Luong Dinh Zhang, Yingjia Huang, Zuohua State Key Laboratory of Multiphase Flow in Power Engineering Xi'An Jiaotong University Xi'an 710049 China Le Quy Don Technical University Hanoi Viet Nam

Ignition delays were measured in a shock tube for syngas mixtures with argon as diluent at equivalence ratios of 0.3, 1.0 and 1.5, pressures of 0.2, 1.0 and 2.0 MPa and temperatures from 870 to 1350 K. Results show that the influences of equivalence ratio on the ignition of syngas mixtures exhibit different tendency at different temperatures and pressures. At low pressure, the ignition delay increases with an increase in equivalence ratio at tested temperature. At high pressures, however, an opposite behavior is presented, that is, increasing equivalence ratio inhibits the ignition at high temperature and vice versa at intermediate temperature. The affecting degree of equivalence ratio on ignition delay is different for each mixture at given condition, especially for the syngas with high CO concentration. Sensitivity analyses demonstrate that reaction H + O2 = O + OH (R1) dominates the syngas oxidation under all conditions. With the increase of CO mole fraction, reactions CO + OH = CO2 + H (R27) and CO + HO2 = CO2 + OH (R29) become more important in the syngas ignition kinetics. With the increase of pressure, the reactions related to HO2 and H 2O2 play the dominate role. The opposite influence of equivalence ratio on ignition delay at high- and intermediate-temperatures is chemically interpreted through kinetic analyses. © 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

关键词： Shock tubes

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Experimental study on the submerged steam jet through side hole nozzle

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IOP Conference Series: Materials Science and engineering 2015年第1期88卷

作者： W Wang F Yuan Q B Zhao D T Chong W X Chen J J Yan State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 PR China

In this paper, the steam shape parameters and the condensation oscillation characteristics of the direct contact condensation of submerged steam jet into subcooled water were investigated through a side hole nozzle. Meanwhile, the dimensionless jet length and the expansion ratio versus pool water temperature and steam mass flux were obtained by measuring the photographs taken by a high speed camera. Both of them increased gradually with rise of pool water temperature and steam mass flux. A comparison of the shape parameters of three different style nozzles was also achieved. And a correlation of the dimensionless jet length was obtained, the predicted data agreed well with the experimental data, while the discrepancy was within ±5%. For the pressure oscillation versus steam mass flux, the peaks and the root mean square value of pressure oscillation were almost consistent in the range of 150-400 kgm-2s-1, while both of them increase in the range of 400-800 kgm-2s-1. The positive peak and negative peak were completely symmetrical.

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Shock tube and kinetic study of C2H6/H 2/O2/Ar mixtures at elevated pressures

Shock tube and kinetic study of C2H6/H 2/O2/Ar mixtures at e...

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作者： Pan, Lun Zhang, Yingjia Zhang, Jiaxiang Tian, Zemin Huang, Zuohua State Key Laboratory of Multiphase Flows in Power Engineering Xi'An Jiaotong University Xi'an 710049 China

Using a high-pressure shock tube facility, the ignition delay times of stoichiometric C2H6/H2/O2 diluted in argon were obtained behind reflected shock wave at elevated pressures (p = 1.2, 4.0 and 16.0 atm) with ethane blending ratios from 0 to 100%. The measured ignition delay times were compared to the previous correlations, and the results show that the ignition delay times of ethane from different studies exhibit an obvious difference. Meanwhile, numerical studies were conducted with three generally accepted kinetic mechanisms and the results show that only NUIG Aramco Mech 1.3 agrees well with the measurements under all test conditions. Sensitivity analysis was made to interpret the poor prediction of the other two mechanisms. Furthermore, the effect of ethane blending ratio on the ignition delay times of the mixtures was analyzed and the results show that ethane blending ratio gives a non-linear effect on the auto-ignition of hydrogen. Finally, chemical interpretations on this non-linear effect were made from the reaction pathway analysis and normalized H radical consumption analysis. © 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

关键词： Shock tubes

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Experimental and kinetic study on ignition delay times of iso -butanol

Experimental and kinetic study on ignition delay times of is...

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作者： Pan, Lun Zhang, Yingjia Tian, Zemin Yang, Feiyu Huang, Zuohua State Key Laboratory of Multiphase Flows in Power Engineering Xi'An Jiaotong University Xi'an 710049 China

Ignition delay times of iso-butanol with fuel concentration of 0.5-1.0% were measured behind reflected shock waves. The experiments were conducted in the temperature range of 900-1700 K, at pressures of 1.2-10.0 atm and equivalence ratios of 0.5-2.0. The measured ignition delay times were compared with previous data under the same conditions and were correlated through multiple linear regression. Using the correlation, the ignition delay times of iso-butanol were compared to those of n-butanol. It was found that iso-butanol presented longer ignition delay time than that of n-butanol. Three available models were used to simulate the ignition delay times. Results showed that Sarathy model exhibited the best predictions at high temperature, but none of these models could well reproduce the measured ignition delay times at intermediate-low temperature. Reaction pathway analysis was performed to chemically interpret the observed difference in ignition delay times of n-butanol and iso-butanol. In addition, sensitivity analysis was made to ascertain the key reactions that control the intermediate-low temperature ignition in the Sarathy model. © 2014 American Chemical Society.

关键词： Temperature

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Numerical study on annular-mist flow in V-Cone meter for wet gas metering

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AIP Conference Proceedings 2014年第1期1592卷 121-129页

作者： Bofeng Bai Denghui He Rifeng Zhou State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

Increasing attention is paid on wet gas flow measurement with V-Cone meter in the production of natural gas. Annular-mist flow is a common flow regime in the wet gas flow metering. Knowledge of the annular-mist flow such as the distributions of the pressure, the droplet and the liquid film in the V-Cone meter is critical to improve the wet gas measurement model. In this paper, a numerical method based on a three-fluid closure model of film, droplet and gas was developed to simulate the annular-mist wet gas flow in the V-Cone meter. The method agreed well with the existing correlation and the relative error of simulation data is less than ±2.5%. The distributions of the droplet, liquid film and static pressure in a V-cone meter and the results on different flow conditions were simulated with the present method. The simulations showed that under the adjustment of the V-Cone element, the droplets moved in a straight path close to the wall after the throat section and a liquid jet was formed. It continues through the diffuser and reattaches to the wall. Some droplets will re-coalescence in the downstream of the V-Cone. It was found that little droplet was entrained in the back of the V-Cone, which was benefit for obtaining the low pressure. The results of the liquid film distribution showed that the liquid film thickness on the pipe wall and the cone body was affected by both the geometry of the V-Cone and the area and strength of the low pressure domain. The pressure in the low pressure domain decreased with the liquid and gas velocity increasing, and the gas-to-liquid viscosity ratio had little effects on the pressure distribution. The downstream low pressure port justifiably locates at six or more pipe diameters downstream of the cone back face for the present V-Cone meter.

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A three-dimensional geometric Monte-Carlo method for the simulation of light propagation in bio-tissue 3rd

A three-dimensional geometric Monte-Carlo method for the sim...

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International Conference on Computational Methods for Thermal Problems, ThermaComp 2014

作者： Zhang, Yong Chen, Bin Li, Dong Wang, Guo-Xiang State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an Shaanxi710049 China Department of Mechanical Engineering The University of Akron AkronOH44325-3903 United States

ISBN: (纸本)9788874317271

A geometric Monte-Carlo (GMC) algorithm is proposed based on accurate calculation of optical transmission on the material interface for the simulation of light propagation in turbid media (e.g. bio-tissue). Grid is not necessary for the computation of photons' motion and the memory of optical parameters can be saved. Optical transmission is exactly simulated at material interfaces with curved boundary according to the principles of geometric optics, while energy deposition in different structures can be precisely counted. The validity of GMC method is confirmed by the comparison with voxels based Monte-Carlo method. Time consumed by GMC method is dramatically shortened compared with the hexahedral voxels based Monte-Carlo (VMC) method: about 25 times faster than VMC with a grid of 140× 140× 100 cells. In addition, the present GMC method shows better portability when raising the geometric complexity.

关键词： Monte Carlo methods

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Novel method for simultaneous measurement of film thickness and mass fraction of urea–water solution

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Chinese Optics Letters 2014年第12期12卷 133-136页

作者：杨荟楠郭晓龙苏明旭蔡小舒 School of Energy and Power Engineering University of Shanghai for Science and Technology Shanghai Key Laboratory of Multiphase Flow and Heat transfer in Power Engineering University of Shanghai for Science and Technology

Quantitative knowledge of the film thickness and mass fraction of the urea-water solution is very crucial in many practical applications. Film thickness or mass fraction can only be determined individually by conventional measurement techniques. We develop a novel measurement method to measure the film thickness and mass fraction of ure^water solution simultaneously. The absorption coefficients of urea-water solution （5 50 wt%） are measured, a pair of optimized wavelengths is then chosen to achieve high measurement sensitivity. Cross validation is also performed and uncertainties of the technique are smaller than 0.68% for thickness measurements and 1.86% for mass fractions.

关键词： Film thickness Metabolism Thickness measurement Uncertainty analysis Urea Water absorption

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Theoretical investigation on thermal responses of blood vessels to 595nm and 1064nm laser 3rd

Theoretical investigation on thermal responses of blood vess...

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International Conference on Computational Methods for Thermal Problems, ThermaComp 2014

作者： Li, Dong Chen, Bin Wu, WenJuan He, YaLing Wang, Guo-Xiang State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an Shaanxi710049 China Department of Mechanical Engineering University of Akron AkronOH44325-3903 United States

ISBN: (纸本)9788874317271

As a kind of congenital vascular malformations, port wine stain is composed of ectatic venular capillary blood vessels buried within healthy dermis. In clinic, pulsed dye laser in visible band (e.g. 595nm) together with cryogen spray cooling have become the golden standard for treatment of PWS. However, due to the limited energy deposition of the PDL in blood, large blood vessels are likely to survive from the laser irradiation and complete clearance of the lesions is rarely achieved. Nd:YAG laser in near infrared 1064nm has deeper penetration depth in tissue, which has great potential in laser treatment of PWS. In this study, a multi-component bio-heat transfer model is developed to demonstrate the blood vessel thermal responses to two lasers. The results show that large and deeply buried blood vessels, which are likely to survive from 595nm laser irradiation, can be coagulated by 1064 nm laser. Meanwhile, the heating patterns within the vessel lumen for two lasers are also different. The 595 nm laser heated the superior portions of large blood vessels more than the inferior portions, while the 1064 nm laser produced uniform heating.

关键词： Blood vessels

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Secondary side flow field of steam generator with coupled heat transfer from primary to secondary side fluid

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Yuanzineng Kexue Jishu/Atomic Energy Science and Technology 2014年第8期48卷 1398-1405页

作者： Cong, Teng-Long Tian, Wen-Xi Qiu, Sui-Zheng Su, Guang-Hui Department of Nuclear Science and Technology State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China

The 3D flow characteristics in SG can provide input for the analysis of flow induced vibration (FIV). The secondary side flow field was simulated based on the porous media model with FLUENT solver. The flow resistances of flow along and cross tubes as well as flow resistances of downcomer, support plates and separators were added to the momentum equation. The 3D heat transfer from primary to secondary side fluid was calculated during iteration and set as the energy source of secondary side fluid, and the calculation results agree well with the design values. Meanwhile, the results show that the resultant localized thermal-hydraulic characteristics were unevenly distributed. The maximum and minimum flow vapor qualities flowing into the primary separators are 0.75 and 0.07, respectively. The average heat transfer coefficients of primary and secondary sides are 15 856.5 and 63 623.0 W/(m2·K), respectively. The maximum heat transfer coefficient of secondary side is 122 862.9 W/(m2·K). The average heat flux of U-tube is 149.9 kW/m2. The maximum cross flow velocity and cross flow energy (ρu2) through the U-bend region are 4.06 m/s and 1 145 J/m3, respectively.

关键词： Porous materials

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