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Investigation on the flow distribution characteristics of a water-wall intermediate header at a supercritical pressure

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Reneng Dongli Gongcheng/Journal of engineering for Thermal Energy and Power 2006年第3期21卷 299-302页

作者： Zhu, Yu-Qin Bi, Qin-Cheng Chen, Ting-Kuan State Key Laboratory of Power Engineering Multi-Phase Flow Xi'an Jiaotong University Xi'an 710049 China

An investigation was conducted of the flow distribution characteristics of distribution header water-wall tubes under a supercritical pressure for a home-made 600 MW once-through boiler. The test parameters can be listed as follows: pressure p=23-25 MPa, mass flow rate G=400-1200 kg/(m2·s), working medium temperature t=10-400°C. An experimental study has been conducted of the impact of working medium pressure, mass flow rate and working medium temperature on the vertical water-wall tube flow distribution characteristics of the distribution header. The test results show that with an increase in mass flow rate, the uniformity of flow distribution among the vertical water-wall tubes could be enhanced. The non-uniformity of flow distribution will undergo a step increase near the quasi-critical points. Moreover, with an increasing pressure, the above-mentioned step increase will become weaker. By employing a discrete model of the parallel-connected branch tubes of the distribution header, the flow distribution among the distribution header vertical water-wall tubes was calculated and the calculation results are in good agreement with the test ones.

关键词： Distribution header Once-through boiler Supercritical pressure Vertical water-wall tubes

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Pressure-velocity coupling algorithm on non-orthogonal non-staggered grid

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Jisuan Lixue Xuebao/Chinese Journal of Computational Mechanics 2006年第1期23卷 93-96页

作者： Xie, Gong-Nan Wang, Qiu-Wang Zhang, Dong-Sheng Tao, Wen-Quan State Key Laboratory of Multi-phase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

In this paper, a new numerical procedure is proposed for the steady flow of a viscous, incompressible fluid based on SIMPLER algorithm on a non-orthogonal non-staggered grid, together with Cartesian velocity components as dependent variables in the momentum equations. The main feature of the algorithm is that the pressure and pressure correction equations are obtained by explicitly treating pressure cross-derivatives terms in interface contravariant velocities. A collocated arrangement of variables is introduced on numerical grids, and the cell face velocities are calculated by the momentum interpolation. It is proved that this algorithm can be effectively used to simulate fluid flow and heat transfer in complex geometry, by the validation calculation of flow inside branching channel.

关键词： Incompressible flow

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

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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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Fabrication of silica colloidal crystal multilayer with controlled thicknesses by vertical deposition

Fabrication of silica colloidal crystal multilayer with cont...

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作者： Li, Qunyan Gao, Weimin Chen, Yunfa Dong, Peng Wu, Zhenjiang Multiphase Reaction Laboratory Institute of Process Engineering Chinese Academy of Sciences Beijing 100080 China State Key Laboratory of Heavy Oil Processing University of Petroleum Beijing 102200 China

The silica colloidal crystal multilayers were deposited from ethanol suspensions with different particle concentrations by vertical deposition method. The microstructures and thicknesses of silica colloidal multilayers were characterized by scanning electron micrography. The thicknesses of colloidal crystal multilayers increased with the particle concentration increasing within a certain range of particles concentrations. When the particle concentration exceeded 2.48wt%, the thicknesses of colloidal crystal multilayers didn't increased with the concentration increasing. Colloidal crystal multilayers with few defects could be deposited from the suspensions with the particle concentration 2.48wt%. The optical properties of the silica colloidal multilayers were investigated by a UV-Vis scanning spectrophotometer in normal incidence. They corresponded well to the microstructure obtained by SEM images.

关键词： Silica

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Experimental study of the hydrogen production from coal/CMC gasified in super critical water by continuous flow thermal-catalytic reaction system

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Taiyangneng Xuebao/Acta Energiae Solaris Sinica 2005年第6期26卷 874-877页

作者： Yan, Qiuhui Guo, Liejin Liang, Xing Zhang, Ximin Hao, Xiaohong Ma, Lijing State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

As coal was transported homogeneously at high pressure by adding the sodium carboxymethylcellulose (CMC), the hydrogen production from catalytic gasification of coal/CMC in supercritical water (SCW) was investigated. The experimental results showed that the molar fraction of hydrogen is higher than that in conventional gasification. H2, CO2 and CH4 are the main product gases, the higher pressure and higher CMC content is advantage of hydrogen production. Longer residence time is favorite to gasification of coal/CMC, but it is not advantage of hydrogen production from coal/CMC gasified in SCW at 20-25 MPa, 15-30 s and 650°C.

关键词： Hydrogen

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Probabilistic distribution of initial ejection state of particles in equilibrium sand transport

引用

Kung Cheng Je Wu Li Hsueh Pao/Journal of engineering Thermophysics 2005年第4期26卷 613-616页

作者： Xing, Mao Guo, Lie-Jin State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

The equilibrium sand transport is simulated by Lagrange model combined with the probabilistic distributions of initial speed and angle of ejection sand grain in this paper. Five forms of the possible distributions are summarized from the previous study results published in literature. Since the macro-quantities simulated by rational distribution should be coincident well with experimental result, the rationality of the distributions can be tested by comparing the quantities simulated from these distributions with the experimental quantities. Detailed analysis indicates that the distribution of initial speed and angle of ejected grains in equilibrium sand transport should be a monotonous decline function. According to the experimental data a segmented function comprised by an exponential distribution and a normal distribution is suggested in this paper. This distributions is confirmed by further comparison with experimental data.

关键词： Distribution Ejection Equilibrium transport Sand

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Investigation on heat transfer characteristics of spiral wall with internal rib in supercritical sliding-pressure operation once-through boiler

引用

Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical engineering 2005年第16期25卷 90-95页

作者： Tang, Ren-Hu Yin, Fei Chen, Ting-Kuan National Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

Within the range of pressures from 9 to 28 MPa, mass velocities from 600 to 1200 kg/(m2s), and heat fluxes from 200 to 500 kW/m2, experiments have been performed to investigate the heat transfer to water in the inclined upward internally ribbed tube with the inclined angle of 19.5 degree, the maximum outer diameter of 38.1 mm, and the thickness of 7.5 mm. Based on the experiments, it was found that heat transfer enhancement of the internally ribbed tube could postpone departure from nucleate boiling at the sub-critical pressure. However, the heat transfer enhancement decreased near the critical pressure. At supercritical pressure, the temperature difference between the wall and fluid increased near the pseudo-critical temperature, but the increasing of wall temperature was less than that of departure from nucleate boiling at sub-critical pressure. When pressure was close to the critical pressure, the temperature difference between the wall and fluid greatly increased near the pseudo-critical temperature. Heat transfer to supercritical water in the inclined upward internally ribbed tube was enhanced or deteriorated near the pseudo-critical temperature with the variety of ratio between the mass velocity and the heat flux. Due to the rotational flow of the internal groove reducing the effect of nature convection, the internal wall temperature of the inclined upward internally ribbed tube uniformly distributed along the circumference. The maximum internal wall temperature difference of the inclined upward internally ribbed tube along the circumference was only 10 degree Centigrade when the fluid enthalpy exceeds 2000 kJ/kg. Considering the effect of acute variety of the fluid property on heat transfer, the correlation of heat transfer coefficient on the top of the inclined upward internally ribbed tube have been provided.

关键词： Boilers

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