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Pool boiling heat transfer and bubble dynamics over micro-pin-finned surface under microgravity

Kung Cheng Je Wu Li Hsueh Pao/Journal of engineering Thermophysics 2013年第11期34卷 2112-2115页

作者： Zhang, Yong-Hai Xue, Yan-Fang Wei, Jin-Jia Zhao, Jian-Fu Long, Yan Qi, Bao-Jin State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China /CAS Institute of Mechanics Chinese Academy of Sciences Beijing 100190 China

For high-efficiently solving the power dissipation problem of electronic components on the spacecraft, experiments were performed using micro-pin-finned structure as heater surface in subcooled nucleate pool boiling of FC-72 under microgravity condition utilizing the drop tower Beijing. Micro-pin-fins with the dimensions of 50 μm×120 μm (thickness × height) were fabricated on the surface of square silicon by using the dry etching technique. The micro-pin-finned silicon chip was heated by means of controlling heating voltage for the desired heat flux. At the same time, video of the bubble behavior was obtained by using high speed camera. The results showed that micro-pin-fins can increase the effective nucleate boiling sites number and the heat transfer performance efficiently, which stems from the sufficient supply of fresh liquid to the heater surface due to the capillary force independent of gravity. The steady nucleate pool boiling heat transfer on micro-pin-finned surface can be obtained at high heat fluxes and is greatly enhanced compared with smooth surface in microgravity.

关键词： Microgravity

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An experimental study on the droplets dynamics of flashing spray with R134a

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Kung Cheng Je Wu Li Hsueh Pao/Journal of engineering Thermophysics 2013年第1期34卷 87-90页

作者： Zhou, Zhi-Fu Wu, Wei-Tao Wang, Guo-Xiang Chen, Bin Wang, Yue-She State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China Department of Mechanical Engineering University of Akron Akron Ohio 44325-3903 United States

Flashing spray is a common phenomenon which finds many applications in the industry, such as flash-spray internal combustion engine, distillation of salt water by flashing evaporation, cryogen spray cooling in dermatology. In order to improve the understanding of atomization mechanism, this paper presents an experimental investigation to the droplets dynamics in the R134a flashing spray including the variations of droplets diameter and velocities. The droplets diameter, droplets axial velocity and radial velocity at different locations are simultaneously measured by the PDPA system. The PDPA measurements data find that both the non-dimensional velocities show self-similar profile. Two empirical equations have been proposed to describe the non-dimensional velocities.

关键词： Velocity

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Calculation of the Critical Speed and Stability Analysis of Cryogenic Turboexpanders with Different Structures

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Plasma Science and Technology 2012年第10期14卷 919-926页

作者：陈双涛赵红利马斌侯予 State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University

A modularized code based on the Finite Element QZ （FEQZ） method is developed, for a better estimate of the critical speed and a more convenient method of rotor-dynamic stability analysis for a gas bearing high speed turboexpander rotor system with actual structure and application of a cryogenic turboexpander. This code is then validated by the experimental data of a gas bearing turboexpander, with a rotor diameter of 25 mm and a rated speed of 106,400 rpm. With this code, four rotors with different structures, available to the turboexpander, are parametrically analyzed by the available speed range, vibration modes and logarithmic attenuation rate. The results suggest that the rotor with a structure of two thrust collars on the system exhibits a better performance in the designed conditions.

关键词： critical speed gas bearing cryogenic turboexpander

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Simulation of hemodynamics in portal vein hypertension using CFD

Simulation of hemodynamics in portal vein hypertension using...

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第五届中美生物医学工程暨海内外生物力学学术研讨会

作者： Xiao Li Yansong Pu Peng Nie Zongfang Li Bin Chen State Key Laboratory of Multiphase Flow in Power Engineering.Xi'an Jiaotong University Second Affiliated Hospital.Xi'an Jiaotong University Department of Radiology Huaihe Hospital of Henan University State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University

＜正＞Introduction Liver cirrhosis generally occurs with the hemodynamic changes during the portal vein hypertension and finally leads to the atrophy of the right lobe of the liver and hepatic *** to the hemodynamic changes,a hypothesis has been proposed that the liver volume is related to the istribution of blood from the splenic vein（SV） that involves nutrition from spleen and pancreas The objective of the present paper is to simulate the blood flow in real models of portal vein hypertension and validate the hypothesis using computational fluid dynamics （CFD） method.

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Experimental studies on the enhanced flow boiling heat transfer and pressure drop of organic fluid with high saturation temperature in vertical porous coated tube

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AIP Conference Proceedings 2013年第1期1547卷 442-453页

作者： Dong Yang Zhi Shen Tingkuan Chen Chenn Q. Zhou State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University 710049 Xi'an China Department of Mechanical Engineering Purdue University Calumet Hammond IN 46323 USA

The characteristics of flow boiling heat transfer and pressure drop of organic fluid with high saturation temperature in a vertical porous coated tube are experimentally studied in this paper. The experiments are performed at evaporation pressure of 0.16-0.31MPa, mass flux of 390-790kg/m2s, and vapor quality of 0.06-0.58. The variations of heat transfer coefficient and pressure drop with vapor quality are measured and compared to the results of smooth tube. Boiling curves are generated at mass flux of 482 and 675kg/m2s. The experimental results indicate that the heat transfer coefficients of the porous tube are 1.8-3.5 times those of smooth tube, and that the frictional pressure drops of the porous tube are 1.1-2.9 times those of smooth tube. The correlations for heat transfer coefficient and frictional pressure drop are derived, in which the effect of fluid molecular weight is included. The experiments show that significant heat transfer enhancement is accompanied by a little pressure drop penalty, the application of the porous coated tube is promising in the process industries.

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Numerical simulation on inertia controlled steam bubble condensation using MPS

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AIP Conference Proceedings 2013年第1期1547卷 614-623页

作者： Daotong Chong Yuki Ishiwatari Yoshiaki Oka Junjie Yan Jiping Liu State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University 710049 Xi'an and Department of Nuclear Engineering &Management University of Tokyo Hongo Tokyo Japan Department of Nuclear Engineering &Management University of Tokyo Hongo Tokyo Japan Department of Nuclear Engineering Waseda University Okubo Tokyo Japan State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University 710049 Xi'an China

Bubble dynamics is quite complicated in the field of two-phase hydrodynamics because the interfacial heat and mass transfer is comprehensively affected by various influencing factors. Bubble condensation can be either thermally controlled or inertia controlled. Inertia controlled bubble condensation indicates that considerable pressure difference exists between the steam bubble and ambient liquid. In this paper, the inertia controlled steam bubble condensation was simulated using moving particle semi-implicit (MPS) method. The spherical bubble is located in the center of the cylindrical pool which makes the possibility of 2-D axisymmetric computation. The lateral and bottom wall are set to be rigid insulated boundaries and the top is free surface boundary. The pool volume must be large enough to eliminate the effects by pool wall. The initial bubble pressure ranges from 0.48 MPa to 3.98 MPa, and the initial bubble diameter ranges from 2 mm to 5 mm, and the ambient water pressure and temperature is 0.1 MPa and 70 °C, respectively. The bubble dynamics during condensation was investigated and the influences of initial bubble pressure and diameter were obtained. The bubble deformation during condensation is shown in figure 1, and the variations of bubble diameters and pressures during condensation are shown in figures 2 and 3, respectively.

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Theoretical analysis of the characteristics of the solid oxide fuel cells with a bi-layer electrolyte

Theoretical analysis of the characteristics of the solid oxi...

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作者： Shen, Shuanglin Guo, Liejin Liu, Hongtan International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power Engineering Xi'An Jiaotong University Xi'an Shaanxi 710049 China Clean Energy Research Institute Department of Mechanical and Aerospace Engineering University of Miami Coral Gables FL 33124 United States

From the analytical model derived earlier [17], analytical expressions for the relative thickness ratio rs of a bi-layer electrolyte and the maximum power density of a fuel cell are developed. Using these expressions, together with the other relationships from the analytical model, the characteristics of solid oxide fuel cells (SOFCs) with a bi-layer electrolyte are analyzed and theoretical analysis of the effect of the configuration of a bi-layer electrolyte on the SOFC performance is performed. The results show that the effectiveness of the bi-layer electrolyte depends strongly on its configuration. In the analyses, the variations of open circuit voltage and the maximum power density with the thickness ratio at different total electrolyte thicknesses and different operating temperatures are obtained. Furthermore, by taking into considerations of the oxygen partial pressure at the interface between the two layers of electrolytes, an analytical expression for the critical relative thickness ratio, above which, the electrolyte is stable, is obtained. © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

关键词： Open circuit voltage

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Study on flow-induced vibration in pipe conveying fluid with orifice plate

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Hedongli Gongcheng/Nuclear Power engineering 2013年第SUPPL.1期34卷 132-135+144页

作者： Liu, Xiang-Hong Luo, Yu-Shan Wang, Hai-Jun Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of China Chengdu 610041 China State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

Taking the vibration and noise in Reactor Cavity and Spent Fuel Pit Cooling and Treatment pipe line in nuclear power plant as an example, based on the actual experimental engineering parameters, the experimental studies on fluctuating pressure excitation and pipe vibration resulted from flow disturbance induced by single local resistance element-orifice plate are conducted under the condition of the different flow rate and the same back pressure. The pipe flow field and pressure field is numerically simulated, especially the flow station of orifice plate. The simulation results and experimental data are compared and analyzed. The research results show that the energy spectrum increases with the increasing of the degree of throttle of orifice plate. As the increasing of flow rate and fluid disturbance, the spectrum breadth of pressure fluctuate increases without the disturbance of other excitation source.

关键词： Nuclear power plants

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Performance analysis of conventional and sloped solar chimney power plants in China

Performance analysis of conventional and sloped solar chimne...

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作者： Cao, Fei Zhao, Liang Li, Huashan Guo, Liejin State Key Laboratory of Multiphase Flow in Power Engineering Xi'An Jiaotong University No. 28 West Xianning Rd Xi'an 710049 China Key Laboratory of Renewable Energy and Gas Hydrate Guangzhou Institute of Energy Conversion Chinese Academy of Sciences Guangzhou China Graduate University Chinese Academy of Sciences Beijing 100049 China

The solar chimney power plant (SCPP) has been accepted as one of the most promising approaches for future large-scale solar energy applications. This paper reports on a heat transfer model that is used to compare the performance of a conventional solar chimney power plant (CSCPP) and two sloped solar chimney power plants (SSCPPs) with the collector oriented at 30° and 60°, respectively. The power generation from SCPPs at different latitudes in China is also analyzed. Results indicate that the larger solar collector angle leads to improved performance in winter but results in lower performance in summer. It is found that the optimal collector angle to achieve the maximum power in Lanzhou, China, is around 60°. Main factors that influence the performance of SCPPs also include the system height and the air thermophysical characteristics. The ground energy loss, reflected solar radiation, and kinetic loss at the chimney outlet are the main energy losses in SCPPs. The studies also show SSCPPs are more suitable for high latitude regions in Northwest China, but CSCPPs are suggested to be built in southeastern and eastern parts of China with the combination to the local agriculture. © 2012 Elsevier Ltd. All rights reserved.

关键词： Solar chimneys

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Experimental investigation on phase change spray cooling with R22

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AIP Conference Proceedings 2013年第1期1547卷 531-536页

作者： Mengjing Li Jionghui Liu Xiufang Liu Yu Hou School of Energy and 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

Great quantities of experiments were performed to study the effects of two-phase spray cooling with high heat flux used R22 as refrigerant. A detailed research of the performance of spray cooling at different subcooling temperature was conducted. The experimental results show that the critical heat flux can reach 272.04W⋅cm−2 with R22 as the working medium, and the corresponding surface temperature is 21.11°C These figures prove that the spray cooling has the advantages of high heat flux as well as lower surface temperature. With increasing overcooling degree of refrigerant at the entrance of nozzle, CHF rises at first and goes to stable then. Which means the CHF can be developed by adding the overcooling of refrigerant. However, the development is limited to a certain degree according to the characteristics of the system; namely, the overmuch increment plays a little role to improve CHF value.

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