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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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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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Study on the Radiation Distribution in A Fluidized Tubular Reactor for Heterogeneous Photocatalytic Hydrogen Production

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Procedia Environmental Sciences 2012年 12卷 285-292页

作者： Zhao Liang Fan Liangliang Jing Dengwei Liu Wenxu Cao Fei Zhu Xule Yang Junyin Zhang Hailong State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an P.R.China

Radiation distribution study is of importance for the design and the optimization of fluidized photocatalytic tubular reactor which has been developed for photocatalytic hydrogen production under direct solar light. In the present study, the radiation distribution in such reactor was successfully simulated by adopting Monte Carlo method and the six-flux radiation absorption-scattering models. Both the incident angles of light around the reactor and the concentration distribution of photocatalyst were taken into account. Our analysis indicates that the angles and the intensity of the incident rays significantly affect the radiation distribution. Moreover, it was also found that the equilibrium radiation distribution has a close relationship with the density distribution of the photocatalysts. The simulated results are expected to be helpful for obtaining the optimal operating parameters for solar photocatalytic hydrogen production.

关键词： Radiation distribution Fluidized tubular reactor Nanometer catalyst Compound parabolic concentrators

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Experimental study on condensation heat transfer of ethanol-water mixtures on a vertical mini-tube

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AIP Conference Proceedings 2012年第1期1428卷 35-42页

作者： XiPing Chen JunJie Yan RongHai Huang JiPing Liu State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiao tong University Xi'an City 710049 China

Experiments were carried out to investigate condensation of ethanol-water vapor mixtures on a vertical mini-tube with outer diameter of 1.032mm. The length, inter diameter of the tube was 110mm, 0.727mm, respectively. The tests were performed at a wide range of ethanol concentrations (Cv=0%, 1%, 2%,5%) and varied velocity of vapor (Uv=2m/s, 4m/s, 6m/s) and pressure (Pv=31.2kPa, 47.4kPa, 84.5kPa). With the change of the vapor-to-surface temperature difference, the heat transfer coefficients revealed nonlinear characteristics with the peak values under all ethanol mass fractions of vapor. The heat transfer coefficients decreased with increasing ethanol mass fraction of vapor.

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Surfactant’s Effect on the Photoactivity of Fe-doped TiO2

Surfactant’s Effect on the Photoactivity of Fe-doped TiO2

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中国材料大会2012

作者： Qingyun Chen Chao Xue Xianglin Li Yunhai Wang State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiao tong University

ISBN: (纸本)9783037856062

Ti(OC4H9)4 was used as the Ti precursor and titanium dioxide (TiO2 ) was prepared by sol-gel method. During the preparation process, Fe3+ was doped and different surfactants, such as SDS, PEG, CTAB, were added to improve the photocatalytic activity of TiO2 . The effect of the different type of surfactants on the structure of Fe-doped TiO2 was discussed. The photocatalysts were characterized by thermogravimetric thermal analysis, X-ray diffraction, scanning electron microscopy and UV-Vis spectrophotometer. The red shift of the absorption edge of the Fe-doped TiO2 prepared by using different surfactants was observed. Methyl orange (MO) solution was degraded under sunlight irradiation to evaluate the photocatalytic performance. The results indicated that the photocatalyst prepared with PEG addition had the highest activity and MO degradation ratio could reach 90% after 4 hours irradiation with the best photocatalyst.

关键词： Sol-gel, Iron-doped titania, Photocatalytic activity, Surfactant.

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Experimental Study on Condensation heat transfer of Ethanol-Water Mixtures on a Vertical Mini-tube

Experimental Study on Condensation heat transfer of Ethanol-...

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The 7th International Symposium on Measurement Techniques for multiphase flows

作者： Chen XiPing Yan JunJie Huang RongHai Liu JiPing State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiao tong University

Experiments were carried out to investigate condensation of ethanol-water vapor mixtures on a vertical mini-tube with outer diameter of 1.032 *** length,inter diameter of the tube was 110 mm,0.727 mm,*** tests were performed at a wide range of ethanol concentrations(Cv=0%,1%,2%,5%) and varied velocity of vapor(Uv=2m/s,4m/s,6m/s) and pressure(Pv=31.2kPa,47.4kPa,84.5kPa).With the change of the vapor-to-surface temperature difference,the heat transfer coefficients revealed nonlinear characteristics with the peak values under all ethanol mass fractions of *** heat transfer coefficients decreased with increasing ethanol mass fraction of vapor.

关键词： Condensation Drop Heat transfer mini-tube

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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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Validation analysis of different mass transfer formula in single droplet evaporation model

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Huagong Xuebao/CIESC Journal 2012年第6期63卷 1704-1708页

作者： Xin, Juanjuan Zhou, Zhifu Xin, Hui Chen, Bin Wang, Guoxiang Guo, Liejin State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 Shaanxi China Department of Mechanical Engineering University of Akron Akron OH44325 United States

Droplet evaporation is one of the important physical processes in liquid spray. Various models have been formulated in literature to compute the mass flow rate of droplet evaporation. It is found that all these models can be written in a single formulation, with various models represented by different expressions in the driving force HM, which can be classified into three kinds, namely, classical model, mass analogy model and drift-flux model. In this paper, we perform an analysis of the assumptions involved in the derivation of the three kinds of models, and find that the drift-flux model, which takes into account the effects of Stefan flow and corrective mass transfer, is the correct expression, while the classical model ignores Stefan flow effect and the mass analogy model ignores transient effect. Then the influence of mass driving force HM on droplet evaporation is analyzed, and it is concluded that both the classical model and the mass analogy model underestimate the effect of evaporation especially at high evaporate rates.

关键词： Mass transfer

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A Comprehensive Performance Evaluation Index for Metal Hydrides Reactor

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Energy Procedia 2012年 29卷 421-430页

作者： Xiangyu Meng Zewei Bao Zhen Wu Fusheng Yang Zaoxiao Zhang Key Laboratory for Thermal Science and Power Engineering of Ministry of Education Department of Engineering Mechanics Tsinghua University Beijing 100084 PR China State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an 710049 PR China

A comprehensive performance evaluation index that reflects the heat transfer capacity of the metal hydrides reactor was introduced, and some advantages of this index were discussed. A mathematical model of hydrogen adsorption and desorption was set up, and the validity of the model was confirmed by experimental data reported in literatures. Numerical simulations about working processes of two types of classical reactors (tubular and disc reactor) were performed. The results of comparative study show that the new index can be used in a quantitative evaluation of the reactor performance, and it is more reasonable than traditional ones.

关键词： Index Performance Reactor Metal hydrides Heat transfer

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Heat Transfer Characteristics flow-Jet Combined Boiling over Micro-Pin-Finned Surfaces

Heat Transfer Characteristics Flow-Jet Combined Boiling over...

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第七届天地应用两相系统国际研讨会

作者： Y.H.Zhang J.J.Wei D.Guo State Key Laboratory of Multiphase Flow in Power Engineering Xi＇an Jiaotong University28 Xianning XiluXi＇an 710049China

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