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Evaporation characteristics of single R404a droplet in laser treatment of PWS in conjunction with cryogen spray cooling

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Zhongguo Jiguang/Chinese Journal of Lasers 2009年第10期36卷 2691-2695页

作者： Xin, Hui Zhou, Zhifu Wang, Guoxiang Chen, Bin Wang, Yueshe State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an Shaanxi 710049 China Department of Mechanical Engineering University of Akron Akron OH 44325 United States

Cryogen spray is an effective cooling technique for the laser treatment of port wine stain (PWS), which can protect the epidermis from the thermal injuries safely. However, cryogen R134a cannot supply enough cooling capacity for the laser surgery in patients with darker skin because of the absorption of laser energy by melanin. Cryogen R404a are expected to protect the darker skin well because of its lower boiling point. A theoretical model is proposed to describe the evaporation process of single droplet and its validation is confirmed by the agreement between numerical simulation with experimental result. With this model, the cooling effect of R404a droplet is compared with R134a droplet and it is found that R404a droplet can reach lower temperature. Then the influences of initial diameter and ambient mass faction of cryogen on the evaporation characteristics of R404a droplet are analyzed and the result is useful to guide the cryogen spray cooling for laser therapy of PWS patients with darker skin.

关键词： Drops

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PIV measurement of turbulent bubbly mixing layer flow with polymer additives

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Journal of Physics: Conference Series 2009年第1期147卷

作者： Ning, T. Guo, F. Chen, B. Zhang, X. State Key Laboratory of Multiphase Flow in Power Engineering Xi'An Jiaotong University Xi'an 710049 China

Based on experimental investigation of single-phase turbulent mixing layer flow with polymer additives, bubbly mixing layer was experimentally investigated by PIV. The velocity ratio between high and low speed is 4:1 and the Reynolds number based on the velocity difference of two steams and hydraulic diameter of the channel ranges is 73333. Gas bubbles with about 0.5% gas fraction were injected into pure water mixing layer with/without polymer additives from three different parts at the end of the splitter plate. The comparison between single phase and bubbly mixing layer shows clearly that the dynamic development of mixing layer is great influenced by the bubble injection. Similar with single phase, the Reynolds stress and vorticity still concentrate in a coniform area of central mixing flow field part and the width will increase with increasing the Reynolds number. Mean Reynolds stress will decrease with bubble injection in high Reynolds numbers and the decreasing of Reynolds stress with polymer additives is much more than pure water case. © 2009 IOP Publishing Ltd.

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Dynamic stability experiments of compliant foil thrust bearing with viscoelastic support

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Tribology International 2009年第5期42卷 662-665页

作者： Quan Zhou Yu Hou Chunzheng Chen School of Energy and Power Engineering Xi’an Jiaotong University Xi’an 710049 PR China State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an 710049 PR China

In order to reduce the complexity of machine construction and improve the mechanical efficiency, high speed rotation machineries usually implement self-acting gas bearings to substitute the traditional oil-lubricated bearings. This paper presents test results of a gas thrust bearing with viscoelastic support which is designed for high speed turbo-machinery. The gas bearing, which belongs to compliant foil bearings, consists of a top thin metal foil and a bottom thin rubber foil. Static and stability experiments are conducted on a high speed gas turbine test rig. The static results indicate that the structural stiffness of test bearing generally increases with the increase in axial load and the decrease in thickness of bottom foil. In the rotation tests, rotor runs stably with small vibration amplitude, which is dominant in waterfall plot during whole speed up procedure. It shows that test bearing has preferable stability characteristics for high speed gas turbines.

关键词： Foil thrust bearing Structural stiffness Bearing stability

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Investigation on surface wettability and surface structure of PTFE after remote oxygen plasma treatment

Investigation on surface wettability and surface structure o...

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IEEE International Conference on Plasma Science (ICOPS)

作者： H. X. Liu H. J. Zhang State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an China Department of Environmental Engineering Xi'an Jiaotong University Xi'an China

Summary form only given. In this paper, the surface wettability and surface structure of poly(tetrafluoroethylene) (PTFE) treated with remote oxygen plasma are studied. The contact angles of the samples are measured and the critical surface tensions (gamma c ) are determined on the basis of the Zisman's plots. Then the variation of contact angle to water (thetas H2O ) and the gamma c are as the functions of the sample positions, which are at the different distance from the center of oxygen plasma active discharge zone. Since the better surface wettability can be obtained at 0 cm and 40 cm from the center of oxygen plasma active discharge zone, respectively, the variation of thetas H2O and are farther as the functions of the plasma treatment time. Furthermore, the values of dispersion force gamma s d , dipole force gamma s p and hydrogen bonding force gamma s h to the surface free energy gamma s of treated PTFE are evaluated by the extended Fowkes equation. The analysis is carried out between the distribution of reactive species in remote oxygen plasma and the surface free energy as well as surface wettability. All the results show that the surface wettability of PTFE treated with oxygen plasma is only determined by the value of polar force (gamma s p + gamma s h ), especially the gamma s h . A mixed atmosphere constituted by all reactive species or super pure and high free radicals concentration in remote oxygen plasma are both propitious to the increasing of polar force (gamma s p + gamma s h ), but the surface free energy is influenced mainly by the concentration of charged particles. X-ray photoelectron spectroscopy (XPS) indicates that the C-F bonds on the PTFE surface are broken by the oxygen plasma treatment, and then the polar functional groups of C-O and C=0 are introduced effectively, the surface wettability increases.

关键词： Surface treatment Surface structures Plasma measurements Water Plasma x-ray sources Surface tension Surface discharges Hydrogen Bonding forces Equations

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Characteristics of heat transfer for narrow gap on horizontal heated surface with porous media

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Yuanzineng Kexue Jishu/Atomic Energy Science and Technology 2009年第5期43卷 431-434页

作者： Hu, Ben-Xue Xu, Yan-Feng Su, Guang-Hui Qiu, Sui-Zheng Zhao, Da-Wei Wu, Ying-Wei State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China School of Nuclear Science and Technology Xi'an Jiaotong University Xi'an 710049 China Nuclear Power Institute of China Chengdu 610041 China

Experiments were carried out to study the characteristics of heat transfer on a downward-facing heated surface with porous media in narrow horizontal gap at atmosphere pressure using water as working fluid. The boiling curves were obtained under different conditions. The heat transfer increases significantly with porous media in the gap especially under boiling condition. The heat transfer in narrow horizontal gap can be enhanced by increasing the gap size and by using porous media with high thermal conductivity and appropriate porosity. Based on the mechanism of heat transfer in porous media, the correlations for natural convection and nucleate boiling were proposed to predict the heat transfer under the present condition.

关键词： Facings

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Comparison of modeling options for delayed neutron precursor movement in a molten salt reactor

Comparison of modeling options for delayed neutron precursor...

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2009 ANS Annual Meeting and Embedded Topical Meeting: Nuclear and Emerging Technologies for Space, NETS 2009

作者： Zhang, Dalin Rineiski, Andrei Qiu, Suizheng State Key Laboratory Multiphase Flow in Power Engineering School of Nuclear Science and Technology Xi'an Jiaotong University 28 West Xian ning Road Xi'an 710049 China Institute for Nuclear and Energy Technologies Forschungszentrum Karlsruhe Hermann-von-Helmholtz-Platz 1 Eggenstein-Leopoldshafen D-76344 Germany

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Experimental study on the performance of an aircraft environmental control system

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Applied Thermal engineering 2009年第16期29卷 3284-3288页

作者： Hongli Zhao Yu Hou Yongfeng Zhu Liang Chen Shuangtao Chen State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an 710049 PR China The First Aircraft Institute of AVIC1 Xi’an 710089 PR China

In this paper, the experimental study on the off-design performance and dynamic response of an aircraft environmental control system (ECS) was presented. A bootstrap air cycle refrigeration system with high-pressure water separation was employed in the ECS. Both the static test and the dynamic test were conducted on the ECS. The performance of the key components including precooler, recuperator, compressor, and turbine was investigated. The test results show the performance of the tested ECS can meet the requirements of design. However, some parameters including outlet pressure, turbine efficiency, and rotational speed might vary obviously when the operation conditions changed. The outlet humidity ratio and outlet temperature might also fluctuate largely during the start-up process. It is necessary to take into account the off-design performance and the transient performance in the design of ECS.

关键词： Environmental control system Off-design performance Dynamic response Brayton cycle

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Application of opposed water spray cooling in an high-temperature entrained-flow coal gasifier

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Kung Cheng Je Wu Li Hsueh Pao/Journal of engineering Thermophysics 2009年第6期30卷 984-986页

作者： Liu, Pei-Yao Chen, Qiu-Yang Zeng, Min Wang, Qiu-Wang State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

A series of chemical reactions happen in the coal gasifier and as a result, high temperature syngas is obtained which contains a lot of solid granules. The high-temperature syngas must be cooled, because it can not be utilized directly. The opposed water spray cooling is not only effective, but also could dedust the syngas. In the present study, the CFD technique is used to investigate the effect of the opposed spray cooling in a gasifier. The Euler-Lagrange method is applied to deal with the syngas and the water droplets respectively. A non-dimensional parameter Temperature Non-uniform Factor (TNF) is defined to confirm the height of the cooling section. The simulated results match the designed data well. If water droplets with small diameters are used, the single-stage water spray cooling is more economic than the two-stage water spray cooling.

关键词： Computational fluid dynamics

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Clogging failure in microfilter for blood cell separation and Its novel improvements tao dong

Clogging failure in microfilter for blood cell separation an...

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2009 16th IEEE International Symposium on the Physical and Failure Analysis of Integrated Circuits, IPFA 2009

作者： Yang, Zhaochu Egeland, Eirik Bentzen Karlsen, Frank Jakobsen, Henrik Norwegian Center of Expertise on Micro- and Nanotechnology Vestfold University College I.M.S.T./R.I. Norway State Key Lab. of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an China NorChipTM A.S. Industriveien 8 N-3490 Klokkarstra Norway

ISBN: (纸本)9781424439102

Clogging failure is common for microfilter utilizing the flat membrane structure. To reduce clogging failure in microfilters, the turbine blade-like micropillar is introduced in microfilter design. Two improved cross-flow microfilter designs employing the blade-like micropillar barrier are presented, one with varied cross-section channels, and the other with Archimedes' spiral channels. Analogy experimental-data based simulations show that the two aforementioned novel microfilters have good filtrating efficiency and fantastic anti-clogging characteristics. and the commercial value of the turbine blade-like barriers is affirmed by the industry Partners. © 2009 IEEE.

关键词： Turbomachine blades

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Piv measurement of turbulent mixing layer flow with polymer additives

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Kung Cheng Je Wu Li Hsueh Pao/Journal of engineering Thermophysics 2009年第4期30卷 608-610页

作者： Ning, Tao Guo, Fu-De Chen, Bin State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

Turbulent mixing layer flow with 200 mg/kg polymer additives was measured by PIV and compared with pure water cause. The velocity ratio between high and low speed is 4:1 and the velocity difference ranges from 0.25 m/s to 1.25 m/s. It is showed that large vortex structures exist in flow field with/without polymer addictives, but the coherent structure is much clearer and the large eddy will roll up earlier when polymer is added. Similar with pure water case, the Reynolds stress is decreasing and the vorticity is increasing with increasing the velocity difference. However, the width and range of Reynolds shear stress and vorticity are wider and larger.

关键词： Turbulent flow

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