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Experiment of flow boiling heat transfer on micro-pin-finned chips with jet impingement

Hsi-An Chiao Tung Ta Hsueh/Journal of Xi'an Jiaotong University 2011年第1期45卷 31-37页

作者： Guo, Dong Wei, Jinjia Zhang, Yonghai State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

The experiment of flow boiling heat transfer on micro-pin-finned chips in FC-72 with jet impingement was *** experimental conditions consisted of two different liquid subcooling degrees (25,35°C),three different cross flow velocities (Vc=0.5,1,1.5 m/s) and three different jet velocities (Vj=0,1,2 m/s).The dimensions of the silicon chips were 10 mm×10 mm×0.5 mm (length×width×thickness) on which two kinds of micro-pin-fins with the dimensions of 30 μm×120 μm,50 μm×120 μm (thickness×height) were fabricated by the dry etching technique. A smooth surface was also tested for comparison. The correlations for nucleate boiling curves and the maximum allowable heat flux curves were obtained. The results show that the heat transfer performance was improved with increasing liquid subcooling and flow velocity. All micro-pin-finned surfaces displayed a considerable heat transfer enhancement. The addition of jet impingement further enhanced the heat transfer at a high heat flux and increased the CHF. At a certain cross flow velocity, the enhancement was more significant as the jet velocity increased, especially for Vc=0.5 m/s, Vj=2 m/s. For the micro-pin-finned chips, the CHF increased by more than 93% while the subcooling was 35°C compared with Vc=0.5 m/s, Vj=0 m/s. As the cross velocity increased, the intensification degree of jet impingement decreased and the increase of CHF also decreased.

关键词： flow velocity

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Supersonic ejector to boost production from low pressure natural gas field

Supersonic ejector to boost production from low pressure nat...

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International Conference on Computer Distributed Control and Intelligent Environmental Monitoring

作者： Wu, Gesheng Chong, Daotong Chen, Weixiong Yan, Junjie State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation Southwest Petroleum University Chendu China State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an China

ISBN: (纸本)9780769543505

An effective way to boost natural gas production from low pressure gas field was introduced in the paper. The supersonic ejector used the energ off high pressure gas wells, which was generally wasted through the choke valve, as its power supply to boost the low pressure gas production. The field experiment of the natural gas ejector was carried out, and the performance of the ejector was also presented. Moreover, the production of low pressure natural gas well was compared when the natural gas ejector was used or not. The economic analysis shows that the recovery period of the capital was less than several months. © 2011 IEEE.

关键词： Natural gas

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The effect of substrates and anodes on microbial fuel cell performance

The effect of substrates and anodes on microbial fuel cell p...

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International Symposium on Water Resource and Environmental Protection (ISWREP)

作者： Wang, Yun-Hai Xi, Huan Lin, Feng-Jiao Wang, Bai-Shi Chen, Qing-Yun State Key Laboratory of Multiphase Flow Department of Environmental Science and Engineering Xi'an Jiaotong University Xi'an China

ISBN: (纸本)9781612843377

In a single chamber microbial fuel cell (MFC), the gas diffusion electrode was employed as cathode. Different organic substrates including starch, glucose and drainage from a hotel were used as fuel to generate electricity. Glucose resulted the best electricity production and the highest COD removal ratio. Nickel foam and carbon cloth were employed as anodes and their effect on MFC performance was discussed. The results indicated that nickel foam could enhance the electricity generation, but suffered an anodic corrosion to form nickel phosphate. The MFC internal resistance was 940 Ω with nickel foam as anode while 640 Ω with carbon cloth as anode. The maximum power output on nickel foam is 190 mW m-2. The coulomb efficiency reached up to 90%. The possible mechanism was discussed based on the anodes characterization results. © 2011 IEEE.

关键词： Anodes

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Kinetic study of the isomerization for endo-tetrahydrodicyclopentadiene over AlCl3 catalyst

Kinetic study of the isomerization for endo-tetrahydrodicycl...

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2011 2nd International Conference on Mechanic Automation and Control engineering, MACE 2011

作者： Hao, Miaoli Wu, Weitao Qi, Suitao Yang, Bolun Yang, Jianming Zhang, Wei Lv, Jian Department of Chemical Engineering State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an China Xi'an Modern Chemistry Research Institute Xi'an China

ISBN: (纸本)9781424494392

The isomerization of endo-tetrahydrodicyclopentadiene (THDCPD) to exo-THDCPD over AlCl3 catalyst has been studied in a batch reactor. The effects of temperature, catalyst loading, and the type and amount of solvent on the isomerization rate were investigated. Under the conditions of removing both internal and external diffusion effects, a kinetic model was established and the model parameters were developed. The results showed that the endo- to exo- isomerization of THDCPD can be treated as a first-order reaction. The activation energy E0 and pre-exponential factor obtained from Arrhenius plot are 116 kJ /mol and 3.39×1013 respectively. The simulation results agreed well with the experimental data. © 2011 IEEE.

关键词： Isomerization

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MPS simulation of primary thrombus formation in capillary

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Kung Cheng Je Wu Li Hsueh Pao/Journal of engineering Thermophysics 2011年第2期32卷 227-229页

作者： Rong, Shao-Shan Chen, Bin State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

The adhesion, activation and aggregation of platelets play an important role in the primary thrombus formation. In present paper, platelets, plasma, normal and injured endodermis of the vessel are modeled as particles with different characteristics and simulated by the Moving Particle Semi-implicit (MPS) method. In order to simulate the aggregation and adhesion of platelets on the injured endodermis of the vessel, a mechanical adhesion force model is introduced according to the inter-molecular force and physiological interaction between platelets and endodermis is modeled by the stretch and rotation of a spring. By this method, the formation of primary thrombus at the injured endodermis of horizontal and bending vessel is numerically reproduced. Results show that the thrombus forms quickly and the number of adhered platelets will not increase if thrombus has been formed. Through the analysis of flow field, the platelets go through the vibration, steady and potential break free process. Compared with horizontal vessel, the thrombus formation at the bending vessel is slower.

关键词： Platelets

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Performance comparison and analysis of typical energy conversion cycle

Performance comparison and analysis of typical energy conver...

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International Conference on Computer Distributed Control and Intelligent Environmental Monitoring

作者： Wang, Yuqi Zheng, Lan Yang, Fusheng Meng, Xiangyu Zhang, Zaoxiao School of Chemical Engineering Northwest University Xi'an Shaanxi 710069 China State Key Laboratory of Multiphase Flow in Power Engineering Xi'An Jiaotong University Xi'an Shaanxi 710049 China

ISBN: (纸本)9780769543505

The performance of 3 types of energy utilization cycles including the organic Rankine cycle, the single stage static hydrogen compression cycle, and the new multistage continuous hydrogen compression cycle were analyzed. A multi-element valued model was used to evaluate the performance holistically, and the result showed that the integrated superiority achieved 0.721, which indicated the continuous hydrogen compression cycle is considered the best option among the typical compression energy utilization cycles and deserves thorough studying. © 2011 IEEE.

关键词： Energy utilization

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Performance enhancement for nanofluid-cooled microchannel heat sink

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Yingyong Jichu yu Gongcheng Kexue Xuebao/Journal of Basic Science and engineering 2012年第SUPPL.期20卷 169-180页

作者： Lin, Lin Wang, Xiaodong Wang, Zhenhua Department of Thermal Engineering University of Science and Technology Beijing Beijing 100083 China State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources North China Electric Power University Beijing 102206 China Beijing Key Laboratory of Multiphase Flow and Heat Transfer for Low Grade Energy North China Electric Power University Beijing 102206 China Xi'an Shaangu Power Co. LTD Xi'an 710075 China

Based on selecting the proper formulas of thermal conductivity and viscosity for nanofluids, a three-dimensional fluid-solid conjugated model was developed to analyze the effect of the heat sink structure, the nanoparticle kind, diameter and volume fraction, and the base fluid kind on the cooling performance of microchannel heat sink. The results showed that: (1) thermal dispersion effect caused by nanoparticle random motion enhanced the thermal convection of nanofluid thus enhances significantly the cooling performance of heat sink;(2) the enhancement of nanofluids was closely dependent on the heat sink structure and the dependence was distinct from the pure fluid, hence the heat sink structure was needed to be optimized for nanofluids as coolants;(3) as the nanoparticle volume fraction increases, the thermal resistance reduced and the pressure increased, the water-based Al2O3 nanofluid with 0.5% volume fraction was the optimal coolant which caused 10.1% decrease in the thermal resistance and only 0.38% increased in the pressure drop;(4) although the nanoparticle size had a small effect on the thermal resistance, nanoparticles with small diameter were recommended with consideration of stability of nanofluids;(5) Al2O3 nanoparticle was superior to TiO2 and CuO, and water was the better base fluid than ethylene glycol and engine oil.

关键词： Nanoparticles

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Anomalous enhancement in thermal conductivity of nanofluid induced by solid walls in a nanochannel

Anomalous enhancement in thermal conductivity of nanofluid i...

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作者： Sun, Chengzhen Lu, Wen-Qiang Bai, Bofeng Liu, Jie State Key Laboratory of Multiphase Flow in Power Engineering Xi'An Jiaotong University Xi'an 710049 China College of Physical Sciences Graduate University Chinese Academy of Sciences Beijing 100049 China

Thermal conductivity of Ar-Cu nanofluid confined between two parallel walls (in a nanochannel) is calculated by equilibrium-molecular-dynamics (EMD) simulation through Green-Kubo formula. The results show that the vibration of nanoparticle in the channel height direction (z-direction) is inhibited due to the presence of solid boundaries and accordingly the thermal conductivity of the confined nanofluid is obviously anisotropic. Anomalous enhancement in the thermal conductivity perpendicular to the z-direction (λ) appears as a result of the strong coupling interactions between the fluid atoms, especially the nanoparticle atoms, and the wall atoms. The thermal conductivity λ of the nanofluid confined in the channel of width h = 5.148 nm increases with the increase of the nanoparticle diameter for the strengthened couplings. The nanoparticle volume fraction effect on the thermal conductivity of the confined nanofluid is more obvious than that in macroscale. In addition, the thermal conductivity λ of the nanofluid with diameter of nanoparticle d = 1.370 nm decreases with the channel width increasing owing to the weakened couplings resulted by a longer interacting distance. © 2011 Elsevier Ltd. All rights reserved.

关键词： Molecular dynamics

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Study on the Radiation Distribution in A Fluidized Tubular Reactor for Heterogeneous Photocatalytic Hydrogen Production

Study on the Radiation Distribution in A Fluidized Tubular R...

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2011 International Conference on Energy and Environment(ICEE 2011)

作者： Zhao Liang Fan Liangliang Jing Dengwei Liu Wenxu Cao Fei Zhu Xule Yang Junyin Zhang Hailong State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University

Radiation distribution study is of importance for the design and the optimization of fluidized photocatalytic tubular reactor which has been developed for photocatalytic hydrogen production under direct solar light. In the present study, the radiation distribution in such reactor was successfully simulated by adopting Monte Carlo method and the six-flux radiation absorption-scattering models. Both the incident angles of light around the reactor and the concentration distribution of photocatalyst were taken into account. Our analysis indicates that the angles and the intensity of the incident rays significantly affect the radiation distribution. Moreover, it was also found that the equilibrium radiation distribution has a close relationship with the density distribution of the photocatalysts. The simulated results are expected to be helpful for obtaining the optimal operating parameters for solar photocatalytic hydrogen production.

关键词： radiation distribution,fluidized tubular reactor,nanometer catalyst,compound parabolic concentrators

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Surface modification of α-Fe2O3 nanorod array photoanodes for improved light-induced water splitting

Surface modification of α-Fe2O3 nanorod array photoanodes f...

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2011 MRS Spring Meeting

作者： Shen, Shaohua Kronawitter, Coleman X. Jiang, Jiangang Guo, Liejin Mao, Samuel S. State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an Shaanxi 710049 China Environmental Energy Technologies Division Lawrence Berkeley National Laboratory Berkeley CA 94720 United States

ISBN: (纸本)9781618395238

α-Fe2O3 nanorod arrays were fabricated by a low-temperature aqueous chemical growth (ACG) technique and followed by an annealing process. For the surface doping of α-Fe2O3 nanorods, β-FeOOH nanorods obtained via ACG were coated with a thin layer of Cr3+ precursor solution by spin coating, and then underwent the annealing treatment in air. Conducting polymer polypyrrole (PPy) decorated α-Fe2O3 nanorods were prepared by electrodeposition method using malic acid contained pyrrole aqueous solution. Primary results showed that the photocurrents of α-Fe2O3 nanorod array photoanodes were greatly enhanced by surface doping of Cr3+, as well as PPy decoration. This might be due to the retarded charge recombination and promoted surface reaction rate of photogenerated holes with water. Further investigation on surface modification of α-Fe2O3 nanorod array photoanodes is currently conducted in our group. © 2011 Materials Research Society.

关键词： Nanorods

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