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Stability of stratified flow and slugging in horizontal gas-liquid flow

Progress in Natural Science:Materials International 2005年第11期15卷 1026-1034页

作者： GU Hanyang and GUO Liejin (state key laboratory of multiphase flow in power engineering, Xi’an Jiaotong University, Xi’an 710049, China) State Key Laboratory of Multiphase Flow in Power Engineering Xi''an Jiaotong University Xi''an 710049 China

A transient one-dimensional two-fluid model is proposed to investigate numerically the interfacial instability and the onset of slugging for liquid-gas flow in a horizontal duct. In the present model, the effects of surface tension and transverse variations in dynamic pressure are taken into account. The evolution of interfacial disturbances is displayed and compared with the linear viscous Kelvin-Helmholtz stability analyses. It shows that interfacial wave is more instable due to the non-linear effect. The model predicts well the stability limit of stratified flow in comparison with the experimental data, and also automatically tracks the onset of slugging. The results show that the initiation of hydrodynamic slugging is related to local interfacial instability. Based on the cycle of slugging, a model for slug frequency is presented, which predicts the trends of slug frequencies with gas/liquid flow rate well in comparison with the available data. The effects of physical properties on slugging have been examined. It is found that with the increase in the gas viscosity and liquid density the slugging would be inhibited, whereas, with the increase in liquid viscosity and gas density, the slugging can be promoted.

关键词： two-fluid model Kelvin-Helmholtz stability interfacial instability onset of slugging gas-liquid stratified flow.

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Study on the heat transfer of cross flow in vertical upward tubes

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Journal of Zhejiang University-Science A(Applied Physics & engineering) 2005年第10期6卷 1128-1131页

作者：胡志华杨燕华周芳德 School of Mechanical Engineering Shanghai Jiao Tong University Shanghai 200030 China State Key Laboratory of Multiphase Flow Xi’an Jiaotong Univeristy Xi’an 710049 China

A special device was designed to measure temperature difference in this study of heat transfer of water and oil cross flow inside vertical upward tubes. A new heat transfer correlation was obtained for cross flow. The experimental results showed that the dependence of heat transfer on Reynolds is much smaller in a narrow space than that in a wide space. It was found that the heat transfer correlation of cross flow in a narrow space is obviously different from that in a wide space, and that the heat transfer correlation obtained in a wide space may not be applicable to the cross-flow heat transfer in a narrow space. Further, the single-phase heat transfer capability of water cross flow was compared with that of oil cross flow. The experimental results showed that the average heat transfer coefficient of water is about 2～3 times that ofoil when they have the same superficial velocity.

关键词： Heat transfer Cross flow Upward

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Thermal boundary condition for the thermal lattice Boltzmann equation

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Physical Review E 2005年第1期72卷 016703-016703页

作者： G. H. Tang W. Q. Tao Y. L. He State Key Laboratory of Multiphase Flow School of Energy and Power Engineering Xi’an Jiaotong University Xi’an Shaanxi 710049 China

A thermal boundary condition for a double-population thermal lattice Boltzmann equation (TLBE) is introduced and numerically demonstrated. The unknown distribution population at the boundary node is decomposed into its equilibrium part and nonequilibrium parts, and then the nonequilibrium part is approximated with a first-order extrapolation of the nonequilibrium part of the populations at the neighboring fluid nodes. Numerical tests with Dirichlet and Neumann boundary constraints show that the numerical results of the TLBE together with the present boundary schemes agree well with the analytical solutions and those of the finite-volume method.

关键词： NAVIER-STOKES EQUATION BGK MODEL HEAT-TRANSFER GAS AUTOMATA flowS SIMULATION PRESSURE VELOCITY

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Gas slippage effect on microscale porous flow using the lattice Boltzmann method

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Physical Review E 2005年第5期72卷 056301-056301页

作者： G. H. Tang W. Q. Tao Y. L. He State Key Laboratory of Multiphase Flow School of Energy and Power Engineering Xi’an Jiaotong University Xi’an Shaanxi 710049 China

A lattice Boltzmann method is developed for gaseous slip flow at the pore scale in microscale porous geometries. flow characteristics through various porous structures are studied for different Knudsen numbers and inlet to outlet pressure ratios. It is found that the gas permeability is larger than the absolute permeability of porous media due to the gas slippage effect. Furthermore, the rarefaction influence on the gas permeability is more evident for porous structures with low porosity. The Klinkenberg equation is confirmed for the simulated porous structures. However, the second-order term of the Knudsen number (Kn2) cannot be neglected for gaseous flow with relatively high Knudsen numbers. A model for predicting the pressure drop of the flow through microscale porous media is presented based on the Ergun equation and the Carman-Kozeny equation by taking into account the effects of gas rarefaction and compressibility.

关键词： MEDIA PERMEABILITY SIMULATION FLUIDS MODEL MICROCHANNELS EQUATION

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Economic performance analysis and heat exchange calculating in the system of storage ice by spraying water in winter

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Yingyong Jichu yu Gongcheng Kexue Xuebao/Journal of Basic Science and engineering 2005年第SUPPL.期13卷 177-183页

作者： Liu, Weimin Bi, Qincheng Guo, Yajun Dong, Mingxiao Zhang, Linhua Gao, Feng State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China School of Environmental and Municipal Eng. Xi'an University of Architecture and Technology Xi'an 710049 China Shandong Institute of Architecture and Engineering Jinan 250014 China

The system of ice-making by spraying water in winter and utilizing the ice in summer is pollution-free and economizes the first investment, operating cost, and reduces the peak of electric power in summer. Through establishing the energy equilibrium equation of sprayed water drop, the relation between the diameter of water droplet and the time of icing at different ambient temperature and coefficient of performance of the system of ice-making by spraying water has been obtained. The errors between the numerical solution and the experimental data lie in a range of 7% to 10%, indicating that the model is reasonable. The method of the ice making is promising in the exercisable region to substitute the mechanical refrigeration system.

关键词： Cold storage

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Study on dryout point in vertical narrow annuli

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Nuclear Science and Techniques/Hewuli 2005年第1期000卷

作者： TIAN Wen-xi AYE Myint QIU Sui-zheng JIA Dou-nan State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong UniversityXi'an710049

Prediction of dryout point is experimentally investigated with deionized water upflowing through narrow annular channel with 1.0 mm and 1.5 mm gap respectively. The annulus with narrow gap is bilaterally heated by AC current power supply. The experimental conditions covered a range of pressure from 0.8 to 3.5 MPa, mass flux of 26.6 to 68.8 kg·m-2·s-1 and wall heat flux of 5 to 50 kW·m-2. The location of dryout is obtained by observing a sudden rise in surface temperature. Kutateladze correlation is cited and modified to predict the location of dryout and proved to be not a proper one. Considering in detail the effects of geometry of annuli, pressure, mass flux and heat flux on dryout, an empirical correction is finally developed to predict dryout point in narrow annular gap under low flow condition, which has a good agreement with experimental data.

关键词： Narrow annular channel Bilaterally heating Dryout point Critical quality Annular flow

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A mathematical model and numerical simulation of pressure wave in horizontal gas-liquid bubbly flow

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自然科学进展（英文版） 2004年第4期14卷 344-349页

作者： HUANG Fei BAI Bofeng Guo Liejin State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong UniversityXi'an 710049China

By using an ensemble-averaged two-fluid model,with valid closure conditions of interfacial momentum exchange due to virtual mass force,viscous shear stress and drag force,a model for pressure wave propagation in a horizontal gas-liquid bubbly flow is *** to the small perturbation theory and solvable condition of one-order linear uniform equations,a dispersion equation of pressure wave is *** pressure wave speed calculated from the model is compared and in good agreement with existing *** to the dispersion equation,the propagation and attenuation of pressure wave are investigated *** factors affecting pressure wave,such as void fraction,pressure,wall shear stress,perturbation frequency,virtual mass force and drag force,are *** result shows that the decrease in system pressure,the increase in void fraction and the existence of wall shear stress,will cause a decrease in pressure wave speed and an increase in the attenuation coefficient in the horizontal gas-liquid bubbly *** effects of perturbation frequency,virtual mass and drag force on pressure wave in the horizontal gas-liquid bubbly flow at low perturbation frequency are different from that at high perturbation frequency.

关键词： pressure wave two-fluid model gas-liquid bubbly flow dispersion speed attenuation

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Dryout point prediction model for bilaterally heated vertical narrow annuli under low flow conditions

Dryout point prediction model for bilaterally heated vertica...

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25th Annual CNS Conference - Nuclear Energy: Meeting the Challenges

作者： Myint, Aye Tian, Wenxi Li, Zhihui Hao, Li Jia, Dounan State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi'an Jiaotong University No.28 Xianning West Road Xi'an City 710049 China

ISBN: (纸本)0919784798

Prediction of dryout point was experimentally investigated with deionized water upflowing through narrow annular channel with 1.0 mm and 1.5 mm gap respectively. The annular with narrow gap was bilaterally heated by AC current power supply. The experimental conditions covered a range of pressure from 0.8 to 3.5 MPa, mass flux of 60.39 to 135.6 kg/m2 and heat flux of 5 to 50 kW/m2 This paper presents a new analytical model for the prediction of dryout point for steam- water flow in narrow annular gap and bilaterally and uniformly heated tubes. The prediction of dryout point for bilaterally heated annuli was based on the droplet-diffusion model for internally heated annuli by Kirillov and Smogalev (1969, 1972). The dryout model prediction values are compared with a experimental data, showing a good agreement in accuracy for the above mentioned parametric range.

关键词： Nuclear power plants

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Experimental study on dryout point in vertical narrow annulus under low flow conditions

Experimental study on dryout point in vertical narrow annulu...

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12th International Conference on Nuclear engineering (ICONE12) - 2004

作者： Tian, Wenxi Myint, Aye Li, Zhihui Qiu, Suizheng Su, G.H. Jia, Dounan State Key Lab. Multiphase Flow P.E. 710049 Xi'an China State Key Lab. Multiphase Flow P.E. Sch. of Energy and Power Engineering Xi'An Jiaotong University 710049 Xi'an China

Prediction of dryout point is experimentally investigated with deionized water upflowing through narrow annular channel with 1.0 mm and 1.5 mm gap respectively. The annular with narrow gap is bilaterally heated by AC current power supply. The experimental conditions covered a range of pressure from 0.8 to 3.5 MPa, mass flux from 26.6 to 68.8 kg/m2 s and wall heat flux from 5.0 to 50.0 kW/m2. The location of dryout is obtained by observing a sudden rise in surface temperature, Kutateladze correlations is cited, however proved to be not a proper one for annuli gap and modified to predict the location of dryout. Considering in detail the effects of the geometry of annuli, pressure, mass flux and heat flux on dryout, an empirical correction is finally developed to predict dryout point in narrow annular gap under low flow condition which has a good agreement with experimental data.

关键词： Two phase flow

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Mathematical model and numerical simulation of helical baffles heat exchanger

Mathematical model and numerical simulation of helical baffl...

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作者： Shen, Renjie Feng, Xiao Gao, Xiaodong Department of Chemical Engineering State Key Laboratory of Multi-Phase Flow in Power Engineering Xi'An Jiaotong University Xi'an China

With the theory of the Reynolds stress model applied, a mathematical model of the flow and heat transfer of the helical baffles heat exchanger is established. The commercial software FLUENT is used to simulate the influence of helical baffles on heat transfer capability and flow resistance of helical baffle heat exchangers by unstructured grid. The numerical simulation results at the 35° helix inclination angle are compared with those of experiment. © 2004 by Begell House, Inc.

关键词： Heat exchangers

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