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Research on the Heat-Conduction Enhancement for Liquid with Nano-Particle Suspensions

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Journal of Thermal Science 2002年第3期11卷 214-219页

作者： B.x.Wang H.Li x.f.peng Department of Thermal Engineering Tsinghua University Beijing P.R. China

By measuring the effective thermal conductivity, taking photos of the distribution of the nano-particles in the fluids and photos that reflect the interfacial phenomena between nano-particles and fluids, we try to exp... 详细信息

关键词： Nano-particle suspension effective thermal conductivity Brownian motion affinity heat-conduction enhancement.

forced-flow Convection for Liquid Methanol flowing through Microchannels

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Journal of Thermal Science 1993年第3期2卷 180-189页

作者： x.f.peng B.x.Wang ThermalEngineeringDepartment TsinghuaUniversityBeijing100084China ThermalEngineeringDepartment Tsin

Experiments were conducted to investigate the single phase forced-flow convection of methanol flowing through microchannels with rectangular *** fully-developed turbulent convection regime was found to be initiated at about Re=1000-1500,The fully developed turbulent heat transfer can be predicted by the well-known Dittus-Boelter correlation with mere modification of the original empirical constant coefficient 0.023 to *** transition and laminar heat transfer behaviors in microchannels are highly peculiar and complicated,and heavily affected by liquid temperature,velocity and microchannel size.

关键词： forced convection heat transfer liquid flow microchannel

Dynamic Behavior of Bubble Interface During Boiling

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Journal of Thermal Science 2002年第4期11卷 308-319页

作者： x.f.peng Z.Wang D.J.Lee Department of Thermal Engineering Tsinghua UniversityDepartment of Thermal Engineering Tsinghua UniversityDepartment of Chemical Engineering Taiwan University Beijing 100084 China Beijing 100084 China Taipei 106 China

A brief review with discussions is conducted for some pertinent works, done and ongoing in the Laboratory of Phase-Change and Interfacial Phenomena at Tsinghua University, on interfacial behavior of vapor bubbles and interfacial transport phenomena during liquid nucleation boiling. from a sequence of experimental investigations, some new phenomena, particularly, the visually observed interfacial transport phenomena or processes including jet-like flows, bubble interaction and spatial scale effect, were described in this article. The interfacial effects and transport phenomena associated with surface tension gradients caused by temperature and concentration variations were theoretically analyzed to reveal the marked influence on bubble interfacial shape and dynamic behavior, the bubble dynamics including nucleation, bubble motion and coalescence. Several theoretical models and methods were proposed to describe the dynamic characteristics and explain the physics of interfacial phenomena/processes. The

关键词： boiling interfacial phenomena transport process phase change bubble.

Interface Shape and Marangoni Effect Around aBubble Within the Thermal Boundary Layer

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Journal of Thermal Science 1998年第1期7卷 54-60页

作者： x.f.peng J.M.Ochterbeck 等 ThermalEngineeringDepartment TsinghuaUniversityBeijing100084China MechanicalEngineeringDepartment C

The characteristics of a vapor bubble within the thermal boundary layer were theoretically *** physical models accounting for the variation of ioterfacial tension and nuid density with tempera-ture were proposed to investigate bubble interfaCe aspects and the fluid flow around the bubble. The analyses demonstrated that the variation in interfacial tension results in variations in the liquid-vapor interface shape and bubble dynamics, which may play a significant role in the departure process of a vapor bubble from a heated wall surface. Increasing temperature gradients in the boundary layer and the gravitational field induce a contact line contraction and correspondingly promotes bubble depar-ture. The simulation of liquid now around the bubble shows that natural convection dominates the flow for earth conditions; however, the thermocapillary forces provide the principal catalyst for bubble departure in a microgravity environment. The results indicate that both the vapor bubble contraction and the Marangoni flow may increase the heat transfer around the vapor bubble and may cause the bubble to mov away from the heating surface, further increasing heat transfer.

关键词： interfacial phenomenon marangoni effect bubble boiling

Relative Stability of Boiling of fC-72 and HfE-7100 with Applications toElectronic Device Cooling

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Journal of Thermal Science 2000年第4期9卷 352-355页

作者： Z.W.LIU x.f.peng 等 DepartmentofChemicalEngineering NationalTaiwanUniversityTaipei10617TaiwanChina DepartmentofThermalEngineering TsinghuaUniversityBeijing100084China

This paper investigates the relative stability between nucleate and film boiling modes of fC-72 and HfE-7100, which have potential to electronic device cooling applications. Equilibrium heat flux, qc, which refers to as an index for measuring the relative stability of boiling, was obtained at a liquid subcooling of 0-20 K. Experimental results reveal that (1) qc increases with liquid subcooling; (2) although the fC-72 exhibits a higher critical heat flux (CHf) than does the HfE-7100, somewhat unexpectedly, the equilibrium heat flux for the latter is greater than the former. Restated, at a prescribed heat flux, the risk to burnout for boiling of fC-72 is higher than that of HfE-7100. The shift in boiling curves interprets the experimental findings.

关键词： boiling relative stability fC-72 HfE-7100 subcooling.

Microstructure and mechanical properties of Mg-to-Al dissimilar welded joints with an Ag interlayer using ultrasonic spot welding

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Journal of Magnesium and Alloys 2020年第2期8卷 552-563页

作者： H.peng D.L.Chen x.f.Bai P.Q.Wang D.Y.Li x.Q.Jiang College of Engineering and Technology Southwest UniversityTiansheng Road 2Beibei DistrictChongqing 400715China Department of Mechanical and Industrial Engineering Ryerson University350 Victoria StreetTorontoOntario M5B 2K3Canada School of Materials and Energy Southwest UniversityTiansheng Road 2Beibei DistrictChongqing 400715China Department of Chemical and Materials Engineering University of AlbertaEdmontonAlberta T6G 1H9Canada

Lightweight ZEK100-0 Mg alloy and A16022-T43 Al alloy with an Ag interlayer were joined via ultrasonic spot welding(USW),focusing on the microstructural change and tensile lap shear strength of the welded joints in relation to welding ***/Al interface was superseded by Mg/Ag and Al/Ag interfaces,and unfavorable Mg门A-intermetallic compound was *** foil was observed to be intact in the nugget center,while it was broken or dissolved at the nugget edge at high welding energy *** diffusion layer at the Mg/Ag interface consisted of two distinctive sub-layers:Mg3Ag intermetallic compound adjoining Ag foil,and Mg3Ag-l-Mg eutectic structure adjacent to *** a thin diffusion layer consisting mainly of Ag3Al occurred al lhe Al/Ag *** tensile lap shear strength first increased,reached its peak value,and then decreased with increasing welding *** shear strength achieved in the present study was〜31%higher than that of the joint without *** failure occurred at all energy levels,with Ag foil particles or fragments being stuck on both Mg and Al sides due to its intense interaction with Mg and Al via accelerated diffusion during *** results obtained pave the way for the challenging dissimilar welding between Mg and Al alloys.

关键词： Magnesium alloy Aluminum alloy Ultrasonic spot welding Ag interlayer Microstructure Tensile lap shear strength

A STUDY Of TEMPERATURE-DEPENDENT VALENCE BOND STRUCTURE Of TITANIUM

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Acta Metallurgica Sinica(English Letters) 2007年第1期20卷 27-34页

作者： x.B. Li Y.Q. xie Y.Z. Nie H.J. peng H.J. Tao f.x. Yu College of Materials Science and Engineering Central South University Changsha 410083 China

On the basis of energy and shape method for the determination of the valence bond （ VB ） structures of crystal, the valence bond structure of titanium is redetermined at room temperature and calculated in the whole temperature range of 0-1943K. The outer shell electronic distribution of Ti is ec^29907. （sc^0.4980 ＋ dc^2.4927） ef^1.0098 in crystal. The temperature dependences of the VB structures of hcp and bcc phases are the same. The VB structures of hcp and bcc phases monotonically increase or decrease with the increase in temperature, but show discontinuous changes at the phase-transformation temperature 1155K.

关键词： valence bond structure temperature titanium

Competitive effect between roughness and mask pattern on charging phenomena during plasma etching

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Plasma Science and Technology 2022年第3期24卷 152-161页

作者： peng ZHANG Ruvarashe f DAMBIRE School of Electronic Information Engineering Yangtze Normal UniversityChongqing 408100People's Republic of China School of Chemistry and Chemical Engineering Yangtze Normal UniversityChongqing 408100People's Republic of China

In the plasma etching process,the edge roughness and mask pattern usually play a significant role in the deformation of holes under the influence of the charging *** competitive effect between these two factors has been investigated,focusing on the surface charging in a hexagonal array,with various values of roughness parameters(amplitude(A)and wavelength(W))and distances between holes(L).A series of classical particle dynamic simulations of surface charging,surface etching and profile evolution were used to investigate the effect of roughness and pattern on *** study showed that various roughness and patterns(represented by different values of L)can significantly influence surface distributions of the electric-field(Efield)and the etching rates on the mask *** simulations also showed that(1)the shape of the pattern array influences the mask hole profile during the etching process,i.e.a hexagonal array pattern tends to deform the profile of a circular mask hole into a hexagonal hole;(2)pattern roughness is aggravated during the etching *** factors were found to be significant only at a small feature pitch and may be ignored at a large feature *** mechanisms of these results during the etching process are *** work sheds light on the ways to maintain pattern integrity and further improve the quality of the pattern transfer onto the substrate.

关键词： plasma etching pattern roughness

Micro injection of metallic glasses parts under ultrasonic vibration

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Journal of Materials Science & Technology 2017年第7期33卷 703-707页

作者： x.Liang J.Ma x.Y.Wu B.xu f.Gong J.G.Lei T.J.peng R.Cheng Guangdong Provincial Key Laboratory ofMicro/Nano Optomechatronics Engineering College of Mechatronics and Control and Engineering Shenzhen University Shenzhen 518060 China Shenzhen ESUN Exhibition Company Limited Shenzhen 518048. China

This work investigates the evolution of structure and mechanical performance of metallic glasses（MGs）under a proposed rapid forming approach. Through the unique ultrasonic-assisted micro injection method, micro MGs parts with fine dimensional accuracy were successfully fabricated. The temperature during the micro injection is higher than the glass transition temperature and lower than the crystallization temperature. Differential scanning calorimeter curve and x-ray diffraction pattern show that the MGs micro parts keep the amorphous nature after the ultrasonic-assisted micro injection. Our results propose a novel route for the fast forming of MGs and have promising applications in the rapid fabrication of micro scale products and devices.

关键词： Metallic glasses Micro injection Ultrasonic vibration