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Simulation of horizontal slug-flow pneumatic conveying with kinetic theory

中国高等学校学术文摘·能源与动力工程 2007年第3期1卷 336-340页

作者： GU Zhengmeng GUO Liejin State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong UniversityXi'an 710049China

Wavelike slug-flow is a representative flow type in horizontal pneumatic *** theory was introduced to establish a 3D kinetic numerical model for wavelike slug gas-solid flow in this *** motion of particulate slugs in horizontal pipes was numerically *** formation and motion process of slugs and settled layer were *** characteristics of the flow,such as pressure drop,air velocity distribution,slug length and settled layer thickness,and the detailed changing characteristics of slug length and settled layer thickness with air velocity were *** results indicate that kinetic theory can represent the physical characteristics of the non-suspension dense phase flow of wavelike slug pneumatic *** experiment in this paper introduced a new idea for the numerical calculation of slug-flow pneumatic conveying.

关键词： slug-flow pneumatic conveying kinetic theory simulation

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Experimental Study of Drop Deformation and Breakup in Simple Shear flows

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Chinese Journal of Chemical engineering 2007年第1期15卷 1-5页

作者：林长志郭烈锦 State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University

The experimental results of the deformation and breakup of a single drop immersed in a Newtonian liq-uid and subjected to a constant shear rate which generated by counter rotating Couette apparatus were presented in this paper. From experimental observations, the breakup occurred by three mechanisms, namely, necking, end pinching, and capillary instability. Quantitative results for the deformation and breakup of drop are presented. The maximum diameter and Sauter mean diameter of daughter drops and capillary thread radius are linearly related to the inverse shear rate and independent of the initial drop size, the dimensionless wavelength which is the wave-length divided by the thread width at breakup is independent of the shear rate and initial drop size, and the deforma-tion of threads follows a pseudo-affine deformation for Cai/Cac larger than 2.

关键词： drop deformation breakup Couette shear flow

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Numerical analysis on heat transfer enhancement by longitudinal vortex based on field synergy principle

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中国高等学校学术文摘·能源与动力工程 2007年第3期1卷 365-369页

作者： WU Junmei TAO Wenquan State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong UniversityXi'an 710049China School of Environment and Chemical Engineering Xi'an Polytechnic UniversityXi'an 710048China State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong UniversityXi'an 710049China

Three-dimensional numerical simulation results are presented for a fin-and-tube heat transfer surface with vortex *** effects of the Reynolds number (from 800 to 2 000) and the attack angle (30° and 45°) of a delta winglet vortex generator are *** numerical results are analyzed on the basis of the field synergy principle to explain the inherent mechanism of heat transfer enhancement by longitudinal *** secondary flow generated by the vortex generators causes the reduction of the intersection angle between the velocity and fluid temperature *** addition,the computational evaluations indicate that the heat transfer enhancement of delta winglet pairs for an aligned tube bank fin-and-tube surface is more significant than that for a staggered tube bank fin-and-tube *** heat transfer enhancement of the delta winglet pairs with an attack angle of 45° is larger than that with an angle of 30°.The delta winglet pair with an attack angle of 45° leads to an increase in pressure drop,while the delta winglet pair with the 30°angle results in a slight *** heat transfer enhancement under identical pumping power condition for the attack angle of 30° is larger than that for the attack angle of 45°either for staggered or for aligned tube bank arrangement.

关键词： longitudinal vortex heat transfer enhancement field synergy principle

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Numerical investigation on the dryout point of annular flow in the upward narrow annuli with bilateral heating

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中国高等学校学术文摘·能源与动力工程 2007年第3期1卷 264-272页

作者： SU Guanghui DUAN Feng QIU Suizheng XIAO Zejun HUANG Yanping State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong UniversityXi'an 710049China National Key Laboratory of Bubble and Natural Circulation Nuclear Power Insitute of ChinaChengdu 610041China

Based on the fundamental conservation principles-the mass,momentum,and energy conservation equtions of liquid films and the momentum conservation equation of vapor core,a theoretical three-fluid model has been developed to predict the dryout point of upward annular flow in vertical narrow annuli with bilateral *** range of the parameters are:pressure from 0.5 to 5.0 MPa;mass flow Through numerically solving the model,the relationships among the parameters of the critical quality (Xc),critical heat flux (QCHF),mass flow rate,system pressure,and the ratio of heat flux on the inner wall of the outer tube to that on the outer wall of the inner tube (qo/qi) are obtained and *** predicted results accurately match with the experimental *** a fixed qo,Xc will increase with the decreases in the gap size and the tube curvature when the dryout point occurs on the outer wall of the inner ***,for a fixed qi,when the dryout point occurs on the inner wall of the outer tube,the parametric trend is *** the dryout point on the inner and outer walls occurs simultaneously,Xc reaches a peak value,and the ratio of qo/qi at this position changes with the gap size and the tube curvature.

关键词： critical heat flux critical quality annular flow dryout numerical simulation

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Hydrogen production from co-gasification of coal and biomass in supercritical water by continuous flow thermal-catalytic reaction system

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中国高等学校学术文摘·能源与动力工程 2007年第3期1卷 327-330页

作者： YAN Qiuhui GUO Liejin LIANG Xing ZHANG Ximin State Key Lab of Multiphase Flow in Power and Engineering Xi'an Jiaotong UniversityXi'an 710049China School of Environmental and Municipal Engineering Xi'an University of Architecture and TechnologyXi'an 710055China State Key Lab of Multiphase Flow in Power and Engineering Xi'an Jiaotong UniversityXi'an 710049China

Hydrogen is a clean energy *** abundant coal sources and green biomass energy into hydrogen effectively and without any pollution promotes environmental *** co-gasification performance of coal and a model compound of biomass,carboxymethylcellulose (CMC)in supercritical water (SCW),were investigated *** influences of temperature,pressure and concentration on hydrogen production from co-gasification of coal and CMC in SCW under the given conditions (20-25 MPa,650℃,15-30 s) are discussed in *** experimental results show that H2,CO2 and CH4 are the main gas products,and the molar fraction of hydrogen reaches in excess of 60%.The higher pressure and higher CMC content facilitate hydrogen production;production is decreased remarkably given a longer residence time.

关键词： hydrogen production coal CMC supercritical water co-gasification

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Natural convection heat transfer of water in a horizontal circular gap

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中国高等学校学术文摘·能源与动力工程 2007年第2期1卷 167-173页

作者： SU Guanghui Kenichiro Sugiyama WU Yingwei State Key Laboratory of Multiphase Flow in Power Emgineering Xi'an jiaotong University Xi'an 710049China Faculty of Engineering Hoddaido University North Ward Sapporo 060-8628Japan

An experimental study on the natural convection heat transfer on a horizontal downward facing heated surface in a water gap was carried out under atmospheric pressure conditions. A total of 700 experimental data points were correlated using Rayleigh versus Nusselt number in various forms, based on different independent variables. The effects of different characteristic lengths and film temperatures were discussed. The results show that the buoyancy force acts as a resistance force for natural convecti on beat transfer ona downward facing horizontal heated surface in a confined space. For the estimation of the natural convection heat transfer under the present conditions, empirical correlations in which Nusselt number is expressed as a function of the Rayleigh number, or both Rayleigh and Prandtl numbers, may be used. When it is accurately predicted, the Nusselt number is expressed as a function of the Rayleigh and Prandtl numbers, as well as the gap width-to-heated surface diameter ratio; and uses the temperature difference between the heated surface and the ambient fluid in the definition of Rayleigh number. The characteristic length is the gap size and the film temperature is the average fluid temperature.

关键词： natural convection downward facing heated surface gap size buoyancy force

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Hydrogen production from sludge in supercritical water and its energy evaluation

Hydrogen production from sludge in supercritical water and i...

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5th International Energy Conversion engineering Conference

作者： Qinming, Zhang Shuzhong, Wang Liang, Wang Donghai, Xu Lingling, Lu State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China Department of Thermal Engineering Xi'an Jiaotong University AIAA

ISBN: (纸本)1563479028

Gasification of high moisture content biomass in supercritical water has been identified as a promising alternative system for producing renewable hydrogen. Supercritical water partial oxidation is the process by which an oxidant appears during the reaction. The key advantage of this process is the rapid heating of the gasification medium, resulting in less char formation and improved hydrogen yield. Many researchers have studied the supercritical water gasification of model compounds. However, real biomass which is of importance for large production of hydrogen has yet to be thoroughly examined. In this paper, gasification of high moisture content municipal sludge was studied in a continuous reactor employing hydrogen peroxide as an oxygen source. The reaction was tested across temperatures and pressures in the range of 673 to 873 K and 24 to 30 MPa, and across various residence times ranging from 3 to 15 minutes. We found that sludge at low concentrations can be completely gasified with no observable char or tar formation. The improvement of gasification efficiency by partial oxidation was accompanied with a high yield of hydrogen and carbon monoxide. Through this, we evaluated the energy efficiency of sludge gasification. Our thermodynamic calculations show that the energy efficiency reaches 50% when considering hydrogen, carbon monoxide, and methane as the valuable gases in the ideal case. Taking into account the energy recovery from the hot water at 30 MPa and 873 K and assuming the ideal scenario of no external heat loss, the overall energy yield potentially reaches 85%. Our results show that the key mechanism of the gasification process is energy recovery, as the chemical reaction is endothermic and requires high temperatures.

关键词： Hydrogen production

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Experimental study of heat transfer of ultra-supercritical pressure water in vertical upward internally ribbed tube

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High Technology Letters 2007年第1期13卷 17-22页

作者：王为术 Chen Tingkuan Luo Yushan　 Gu Hongfang Yin Fei National Key Laboratory of Multiphase Flow in Power Engineering Xi＇ an Jiaotong University Xi＇ an 710049 P.R. China School of Power Electric North China Institute of Water Conservancy and Hydroelectric Power Zhengzhou 450011 P.R. China

Under ultra-supercritical pressure, the heat transfer characteristics of water in vertical upward 4- head internally ribbed tubes with a diameter of 28.65mm and thickness of 8mm were experimentally studied. The experiments were performed at P = 25- 34MPa, G = 450- 1800kg/（m^2·s） and q = 200 600kW/m^2. The results show that the pressure has only a moderate effect on the heat transfer of uhra-supercritical water when the water temperature is below the pseudocritical point. Sharp rise of the wall temperature near the pesudocritical region occurs earlier at a higher pressure. Increasing the mass velocity improves the heat transfer with a much stronger effect below the pesudocritical point than that above the pesudocritical point. For given pressure and mass velocity, the inner wall heat flux also shows a significant effect on the inner wall temperature, with a higher inner wall heat flux leading to a higher inner wall temperature. Increasing of inner wall heat flux leads to an early occurrence of sharp rise of the wall temperature. Correlations of heat transfer coefficients are also presented for vertical upward internally ribbed tubes.

关键词： heat transfer supercritieal ultra-supereritieal vertical upward internally fibbed tube

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New revised correlation to predict pressure drop for oil-gas two-phase flow through horizontal pipe

New revised correlation to predict pressure drop for oil-gas...

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International Petroleum Technology Conference 2007, IPTC 2007

作者： Liu, Wenhong Guo, Liejin Zhang, Ximin Lin, Kai Yang, Long Feng, Yaorong Tubular Goods Research Center of CNPC Key Laboratory for Mechanical and Environmental Behavior of Tubular Goods China State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University China

ISBN: (纸本)9781615673360

An experimental investigation on oil-gas two-phase flow through a straight horizontal plexiglas pipe within 40mm inner diameter was conducted. The superficial velocity ranges of oil and air were 0.05-0.612m/s and 0.024-50.64m/s, respectively. The atmospheric temperature condition was maintained throughout the *** frictional pressure drop multiplier of two-phase flow was expressed using the Lockhart-Martinelli parameter correlation in accordance with typical flow pattern, but the modification factor C in the correlations was defined afresh according to flow conditions. New predict correlations for pressure gradient in accordance with typical flow patterns were proposed and the mechanisms of pressure drop production were analyzed for each flow patterns. The proposed models give a good agreement with the experimental data. Copyright 2007, International Petroleum Technology Conference.

关键词： Two phase flow

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New Method of Online Measurement of Oil and Suspended Material Concentration In flowing Waste Water

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AIP Conference Proceedings 2007年第1期914卷 215-220页

作者： Hongwei Liao Guobing Xu Xinqiang Xu Fangde Zhou Key State Laboratory of Multiphase Flow and Power engineering Xian Jiaotong University Xian China

At present, the most of the measurements of oil and suspended material concentration in waste water measuring are not online surveys. A new method of online measurement of oil and suspended material concentration in flowing waste water is presented. The room experiments and field tests showed that it is suitable to waste water treatment on line. After sampling, It needed to measure immediately the concentration in first time. Then let sample to be in still in 10 – 20 seconds. After that the bulk concentration was measured in second time. Because of the suspended solids having heavy density, they would be dropped from waster water. During ultrasonic operation, emulsify the oil in waster water, the oil and suspended solid would be depart. After that the third time measurement was done. In thus way the concentrations of oil and suspended solids can be measured. At present there are two on‐site equipments operating in the Changqing oilfield, and the results are pretty well.

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