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Numerical simulation of upward microbubble-laden turbulent channel flow

Nanjing Hangkong Hangtian Daxue Xuebao/Journal of Nanjing University of Aeronautics and Astronautics 2007年第1期39卷 51-55页

作者： Xiong, Xianpeng Liu, Weihua Ang, Haisong Gao, Xiufeng Wei, Jinjia College of Aerospace Engineering Nanjing University of Aeronautics and Astronautics Nanjing 210016 China State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

To improve the predictive accuracy of bubble concentration distribution, numerical study of upward turbulent channel flows laden with microbubbles is carried out and the fluid-bubble two-way coupling interaction is considered. Direct numerical simulation is used for solving the Navier-Stokes equation and Lagrangian approach is used to track the bubble trajectories through the action of forces imposed by the fluid and the gravity. The forces acted on the bubbles are drag, virtual mass, lift, wall lift, pressure gradient, and gravity. Numerical results show that the bubble concentration distribution can be predicted by using the two-way coupling of the fluid and the bubble motion, and adding the wall lift force into the bubble motion equation, and the fluid velocity, turbulence intensity and shear stresses modified by the bubble motions can also be revealed.

关键词： Bubbles (in fluids)

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Heat transfer performance of a solar LiBr absorption refrigeration system

Heat transfer performance of a solar LiBr absorption refrige...

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5th International Energy Conversion engineering Conference

作者： Gu, Yaxiu Wu, Yuyuan Liu, Ting Chen, Liufang Zhang, Qinming Institute of Refrigerating and Cryogenic 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 Institute of Refrigerating and Cryogenic Engineering Xi'an Xianning West Road 28# China Department of Thermal Engineering Xi'an Xianning West Road 28#

ISBN: (纸本)1563479028

The utilization of solar heat and waste heat in order to energize absorption chillers is an important issue for increasing the energy efficiency of cooling machines. A compact pump-free LiBr absorption refrigeration system (without the generator-pump, the evaporator-pump and the absorber-pump) driven by solar energy is designed and reconstructed. The required minimum driving temperature of the heat source is only 68°C compared to above 100°C in traditional absorption refrigeration systems. This paper aims to present the effects of various running parameters on the heat transfer performance of a solar refrigeration system, and typical experimental data. The phase change heat transfer is intensified in both the lunate channel of the thermosiphon elevation tube and the second generator. In this way, the two-phase solution is elevated continuously without pumps with a low driving temperature. The structure of the overflow-type spray system is optimized to make the aqueous solution of LiBr be absorbed and to make the condensate be evaporated in a once-through spray. Therefore, the aqueous solution in the refrigeration system can be in steady continuous absorption and evaporation without the absorber pump and the evaporator pump. In a cross-flow horizontal falling film heat exchanger, the staggered coil is wrapped with the mesh screen to hold up more liquid film. The performance of the heat and mass transfer is improved due to an increase in the wet ratio of the surface. Based on the heat and mass transfer theory of falling film absorption, an experimental study is carried out to analyze the performance of the refrigeration system. An experimental investigation is undertaken to characterize the effects of the absorption pressure, the inlet temperature of the solution, and the inlet temperature of the cooling water on the heat and mass transfer in the absorption process. The implications of the data are discussed in detail.

关键词： Refrigerating machinery

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Gas‐Liquid Two‐Phase flows Inverse Analysis in An Aeration Tank

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AIP Conference Proceedings 2007年第1期914卷 877-882页

作者： Wen Cheng Zhang‐bin Wang Yuichi Murai Fujio Yamamoto 1State Key Laboratory of Multiphase Flow in Power Engineerig Xi’ann Jiaotong University Xi’an 710049 China 2Environment Research Institute Xian University of Technology Xian 710048 China 3Div. of Mec. Science Graduate School of Engineering Hokkaido University Japan 4Graduate School of Engineering University of Fukui Bunkyo 3‐9‐1 Fukui 910‐8507 Japan

In bubbly two‐phase flow, the gas phase and liquid phase have different flow fields. The mathematical expression for the motion of a small bubble at low Re number has been already established, the liquid velocity along the trajectory of the bubble is calculated inversely by using the motion equation. Whole field liquid flow structure has also estimated using a spatial and/or temporal interpolation method. This paper proposes an algorithm for estimating the liquid phase flow field based on measurement data on bubble data on bubble motion. The applicability of the algorithm is examined with Taylor‐Green vortex flow as an analytical test case. Meanwhile, The result, based on the theory, has been applied to reconstruct liquid phase velocity field by using the data of bubble velocity in an aeration tank.

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Experimental investigation of enhanced heat transfer for fined circular tube heat exchanger with rectangular fins

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Journal of Harbin Institute of Technology(New Series) 2006年第4期13卷 385-390页

作者：李永星杨冬陈听宽 State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University

Presents a set of data for flow and heat transfer of finned-tube bundle under the condition of high air flow velocity. Air flow and heat transfer over a 4 × 4 （ columns × rows） finned-tube heat exchanger with rectangular fins was investigated experimentally in a wind tunnel with constant wall temperatures condition. The air flow velocity based on the minimum flow cross-section area over flow channel ranged from 13.8 to 50. 2 m/s, the heal transfer rate ranged from 21.8 to47. 1 kW, and the air temperatures increase ranged from 10. 9 to 19. 8 ℃. The present results were compared with results calculated from correlations proposed by CSPE. For air flow velocity less than 25 m/s, these two results of heat transfer agreed well with each other, whereas for larger velocity, our test data disagreed with the CSPE correlations. For the friction factor, present data are much higher than the predicted results in the whole range. Finally, correlations for friction factors and heat transfer coefficients are DrODosed based on the experimental results.

关键词： haeat exchanger rectangular finned-tube enhanced heat transfer friction factor

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Prediction of Heat Transfer Rates for Shell-and-Tube Heat Exchangers by Artificial Neural Networks Approach

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Journal of Thermal Science 2006年第3期15卷 257-262页

作者： Qiuwang WANG Gongnan XIE Ming ZENG Laiqin LUO State Key Laboratory of Multiphase Flow in Power Engineering Xi＇an Jiaotong University Shaanxi Xi＇an710049 China

This work used artificial neural network(ANN)to predict the heat transfer rates of shell-and-tube heatexchangers with segmental baffles or continuous helical baffles,based on limited experimental *** BackPropagation (BP) algorithm was used in training the *** network configurations were *** deviation between the predicted results and experimental data was less than 2%.Comparison withcorrelation for prediction shows ANN *** is recommended that ANN can be easily used to predict theperformances of thermal systems in engineering applications,especially to model heat exchangers for heattransfer analysis.

关键词： heat transfer rate Artificial Neural Network shell-and-tube heat exchanger back propagation

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A Piv Measurement and Numerical Simulation of Gas‐Liquid Two‐Phrase flow in An Aeration Tank

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AIP Conference Proceedings 2007年第1期914卷 453-457页

作者： Wen Cheng Chun‐Di Yang Yuichi Murai Fujio Yamamoto 1State Key Laboratory of Multiphase Flow in Power Engineerig Xi’ann Jiaotong University Xi’an 710049 China 2Environment Research Institute Xian University of Technology Xian 710048 China 3Div. of Mec. Science Graduate School of Engineering Hokkaido University Japan 4Graduate School of Engineering University of Fukui Bunkyo 3‐9‐1 Fukui 910‐8507 Japan

Aeration plays an important role in the treatment of activated sludge. The aeration performance is deeply affected by the movement law of bubble liquid flow in aeration tank. In order to discuss the influence of gas‐phase, liquid‐phase motions in an aeration tank on the sewage disposal, three kinds of boundaries and initial conditions were applied in the experiment to study the law of two‐phase flow. A developed two‐equation turbulence model was employed in this paper. Results obtained by experiment are compared with those from the mathematical model. It is found that the results of measurement and simulation agree with each other.

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Theoretical investigation on the steady-state natural circulation characteristics of a new type of pressurized water reactor

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Nuclear Science and Techniques 2006年第5期17卷 314-320页

作者： GOU Jun-Li QIU Sui-Zheng SU Guang-Hui JIA Dou-Nan State Key Laboratory of Multiphase Flow in Power Engineering Xi＇an Jiaotong University Xi＇an 710049 China

This article presents a theoretical investigation on the steady-state natural circulation characteristics of a new type of pressurized water reactor. Through numerically solving the one-dimensional steady-state single-phase conservative equations for the primary circuit and the steady-state two-phase drift-flux conservative equations for the secondary side of the steam generator, the natural circulation characteristics were studied. On the basis of the pre- liminary calculation analysis, it was found that natural circulation mass flow rate was proportional to the exponential function of the power and that the value of the exponent is related to the operating conditions of the secondary side of the steam generator. The higher the outlet pressure of the secondary side of the steam generator, the higher the pri- mary natural circulation mass flow rate. The larger height difference between the core center and the steam generator center is favorable for the heat removal capacity of the natural circulation.

关键词：核反应堆压水堆稳态自然循环高度差理论研究

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Analysis of flow instabilities in forced-convection steam generator

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Nuclear Science and Techniques 2006年第3期17卷 185-192页

作者： WU Ge-Ping QIU Sui-Zheng SU Guang-Hui JIA Dou-Nan State Key Laboratory of Multiphase Flow in Power Engineering Xi＇an Jiaotong University Xi＇ an 710049 China

Because of the practical importance of two-phase instabilities, substantial efforts have been made to date to understand the physical phenomena governing such instabilities and to develop computational tools to model the dynamics. The purpose of this study is to present a numerical model for the analysis of flow-induced instabilities in forced-convection steam generator. The model is based on the assumption of homogeneous two-phase flow and ther- modynamic equilibrium of the phases. The thermal capacity of the heater wall has been included in the analysis. The model is used to analyze the flow instabilities in the steam generator and to study the effects of system pressure, mass flux, inlet temperature and inlet/outlet restriction, gap size, the ratio of do / di, and the ratio of qi / qo on the system be- havior.

关键词：蒸汽发生器强迫对流流动不稳定性双相不稳定性

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An investigation of flow characteristics and critical heat flux in vertical upward round tube

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Nuclear Science and Techniques 2006年第3期17卷 170-176页

作者： FAN Pu QIU Sui-Zheng JIA Dou-Nan State Key Laboratory of Multiphase Flow in Power Engineering Xi＇an Jiaotong University Xi＇an 710049 China

Prediction of critical heat flux (CHF) in annular flow is important for the safety of once - through steam generator and the reactor core under accident conditions. The dryout in annular flow occurs at the point where the film is depleted due to entrainment, deposition, and evaporation. The film thickness, film mass flow rate along axial distribution, and CHF are calculated in vertical upward round tube on the basis of a separated flow model of annular flow. The theoretical CHF values are higher than those derived from experimental data, with error being within 30%.

关键词：环流临界热通量沉积挟带核反应堆工程

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Experimental analysis on adjusting performance of vapor-liquid two-phase flow controller

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Journal of Harbin Institute of Technology(New Series) 2006年第5期13卷 525-530页

作者：李慧君屠珊 School of Energy and Power Engineering North China Electric Power UniversityBaoding 071003ChinaState Key Laboratory of Multiphase Flow in Power EngineeringXi'an Jiaotong UniversityXi'an 710049China State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong UniversityXi'an 710049China

The vapor-liquid self-adjusting controller is an innovative automatic regulating *** order to ensure adjusted objects run safely and economically,the controller automatically adjusts the liquid flux to keep liquid level at a required level according to physical properties of vapor-liquid two-phase *** adjusting mechanics,the controller’s performance and influencing factors of its stability have been analyzed in this *** theoretical analysis and successful applications have demonstrated this controller can keep the liquid level steady with good *** actual application in industry has shown that the controller can satisfactorily meet the requirement of industrial production and has wide application areas.

关键词： vapor-liquid two-phase flow adjusting performance liquid level controller

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