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Acta Metallurgica Sinica(English Letters) 2018年第1期31卷 1-18页

作者： Saad B.Aziz Mohammad W.Dewan Daniel J.Huggett Muhammad A.Wahab Ayman M.Okeil T.Warren Liao Department of Mechanical and Industrial Engineering Louisiana State University Department of Civil and Environmental Engineering Louisiana State University

This paper presents a new thermomechanical model of friction stir welding which is capable of simulating the three major steps of friction stir welding （FSW） process, i.e., plunge, dwell, and travel stages. A rate-dependent Johnson- Cook constitutive model is chosen to capture elasto-plastic work deformations during FSW. Two different weld schedules （i.e., plunge rate, rotational speed, and weld speed） are validated by comparing simulated temperature profiles with experimental results. Based on this model, the influences of various welding parameters on temperatures and energy generation during the welding process are investigated. Numerical results show that maximum temperature in FSW process increases with the decrease in plunge rate, and the frictional energy increases almost linearly with respect to time for different rotational speeds. Furthermore, low rotational speeds cause inadequate temperature distribution due to low frictional and plastic dissipation energy which eventually results in weld defects. When both the weld speed and rotational speed are increased, the contribution of plastic dissipation energy increases significantly and improved weld quality can be expected.

关键词： Aluminum alloy Friction stir welding temperature distribution Plastic energy Frictional energy Rate-dependent model Friction modeling

CFD simulation of thermal hydraulic characteristics in a typical upper plenum of RPV

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Frontiers in Energy 2021年第4期15卷 930-945页

作者： Mingjun WANG Lianfa WANG Yingjie WANG Wenxi TIAN Jian DENG Guanghui SU Suizheng QI State Key Laboratory of Multiphase Flow in Power Engineering Department of Nuclear Science and TechnologyXi’an Jiaotong UniversityXi’an 710049China Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of ChinaChengdu 610213China

A comparative computational fluid dynamics(CFD)study was conducted on the three different types of pressurized water reactor(PWR)upper plenum,named TYPE 1(support columns(SCs)and control rod guide tubes(CRGTs)with two large windows),TYPE 2(SCs and CRGTs without windows),and TYPE 3(two parallel perforated barrel shells and CRGTs).First,three types of upper plenum geometry information were collected,simplified,and adopted into the BORA facility,which is a 1/5 scale system of the four-loop PWR reactor.Then,the geometry,including the upper half core,upper plenum region,and hot legs,was built using the Salome platform.After that,an unsteady calculation to simulate the reactor balance operation at hot full power scenario was performed.Finally,the differences of flowrate distribution at the core outlet and temperature distribution and transverse velocity inside the hot legs with different upper plenum internals were compared.The results suggest that TYPE 1 upper plenum internals cause the largest flowrate difference at the core outlet while TYPE 3 leads to the most even distributed flowrate.The distribution and evolution pattern of the tangential velocity inside hot legs is highly dependent on the upper plenum internals.Two counter-rotating swirls exist inside the TYPE 1 hot leg and only one swirl revolving around the hog leg axis exist inside the TYPE 2 hot leg.For TYPE 3,two swirls like that of TYPE 1 rotating around the hot leg axis significantly increase the temperature homogenization speed.This research provides meaningful guidelines for the future optimization and design of advanced PWR upper plenum internal structures.

关键词： pressurized water reactor(PWR) upper plenum internal structures temperature distribution computational fluid dynamics(CFD)

Thermal and induced flow characteristics of radio frequency surface dielectric barrier discharge plasma actuation at atmospheric pressure

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Chinese Physics B 2017年第1期26卷 320-325页

作者：王蔚龙李军宋慧敏金迪贾敏吴云 Science and Technology on Plasma Dynamics Laboratory Air Force Engineering University Xi'an 710038 China

Thermal and induced flow velocity characteristics of radio frequency（RF） surface dielectric barrier discharge（SDBD）plasma actuation are experimentally investigated in this paper. The spatial and temporal distributions of the dielectric surface temperature are measured with the infrared thermography at atmospheric pressure. In the spanwise direction, the highest dielectric surface temperature is acquired at the center of the high voltage electrode, while it reduces gradually along the chordwise direction. The maximum temperature of the dielectric surface raises rapidly once discharge begins.After several seconds（typically 100 s）, the temperature reaches equilibrium among the actuator＇s surface, plasma, and surrounding air. The maximum dielectric surface temperature is higher than that powered by an AC power supply in dozens of k Hz. Influences of the duty cycle and the input frequency on the thermal characteristics are analyzed. When the duty cycle increases, the maximum dielectric surface temperature increases linearly. However, the maximum dielectric surface temperature increases nonlinearly when the input frequency varies from 0.47 MHz to 1.61 MHz. The induced flow velocity of the RF SDBD actuator is 0.25 m/s.

关键词： radio frequency discharge temperature distribution induced flow velocity plasma aerodynamic actuation

Reconstruction model for temperature and concentration profiles of soot and metal-oxide nanoparticles in a nanofluid fuel flame by using a CCD camera

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Chinese Physics B 2018年第5期27卷 334-343页

作者：刘冠楠刘冬 MIIT Key Laboratory of Thermal Control of Electronic Equipment School of Energy and Power EngineeringNanjing University of Science and Technology Advanced Combustion Laboratory School of Energy and Power EngineeringNanjing University of Science and Technology

This paper presents a numerical study on the simultaneous reconstruction of temperature and volume fraction fields of soot and metal-oxide nanoparticles in an axisymmetric nanofluid fuel sooting flame based on the radiative energy images captured by a charge-coupled device（CCD） camera. The least squares QR decomposition method was introduced to deal with the reconstruction inverse problem. The effects of ray numbers and measurement errors on the reconstruction accuracy were investigated. It was found that the reconstruction accuracies for volume fraction fields of soot and metaloxide nanoparticles were easily affected by the measurement errors for radiation intensity, whereas only the metal-oxide volume fraction field reconstruction was more sensitive to the measurement error for the volume fraction ratio of metaloxide nanoparticles to soot. The results show that the temperature, soot volume fraction, and metal-oxide nanoparticles volume fraction fields can be simultaneously and accurately retrieved for exact and noisy data using a single CCD camera.

关键词： simultaneous reconstruction temperature distribution soot and metal-oxide volume fraction nanofluid fuel flame

Comparison of space cooling/heating load under non-uniform indoor environment with convective heat gain/loss from envelope

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Building Simulation 2021年第3期14卷 565-578页

作者： Shuai Yan Xianting Li Department of Building Science Beijing Key Laboratory of Indoor Air Quality Evaluation and ControlTsinghua UniversityBeijingChina

The indoor parameters are generally non-uniform distributed.Consequently,it is important to study the space cooling/heating load oriented to local requirements.Though the influence of indoor set point,heat sources,and ambient temperature of convective thermal boundary on cooling/heating load has been investigated in the uniform environment in previous research,the influence of these factors,particularly the convective heat gain/loss through a building envelope,on cooling/heating load of non-uniform environment has not yet been investigated.Therefore,based on the explicit expression of indoor temperature under the convective boundary condition,the expression of space cooling/heating load with convective heat transfer from the building envelope is derived and compared through case studies.The results can be summarized as follows.(1)The convective heat transferred through the building envelope is significantly related to the airflow patterns:the heating load in the case with ceiling supply air,where the supply air has a smaller contribution to the local zone,is 24%higher than that in the case with bottom supply air.(2)The degree of influence from each thermal boundary to the local zone of space cooling cases is close to that of a uniform environment,while the influence of each factor,particularly that of supply air,is non-uniformly distributed in space heating.(3)It is possible to enhance the influence of supply air and heat source with a reasonable airflow pattern to reduce the space heating load.In general,the findings of this study can be used to guide the energy savings of rooms with non-uniform environments for space cooling/heating.

关键词： cooling/heating load non-uniform environment space cooling/heating temperature distribution building envelope

Two-dimensional thermal illusion device with arbitrary shape based on complementary media

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Chinese Physics B 2017年第10期26卷 289-294页

作者：夏舸寇蔚杨立杜永成 Department of Power Engineering Naval University of Engineering

On the basis of transformation thermodynamics and compensation medium theory, we develop a method to design a two-dimensional thermal illusion device with arbitrary shape, and the general expression of thermal conductivity in the each region is obtained. Simulation results show that when an object is covered with the thermal illusion device, it will accurately perform the same temperature distribution signature as another object we have predetermined. Owing to the property of deceiving and interfering with the observer, the thermal illusion device can achieve generalized thermal stealth by using thermal metamaterials, which may have a potential application in military field.

关键词： transformation thermodynamics compensation medium thermal illusion device temperature distribution

A novel analytical thermal model for multilevel nano-scale interconnects considering the via effect

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Chinese Physics B 2009年第11期18卷 4995-5000页

作者：朱樟明李儒郝报田杨银堂 Microelectronics Institute Xidian University

Based on the heat diffusion equation of multilevel interconnects, a novel analytical thermal model for multilevel nano-scale interconnects considering the via effect is presented, which can compute quickly the temperature of multilevel interconnects, with substrate temperature given. Based on the proposed model and the 65 nm complementary metal oxide semiconductor （CMOS） process parameter, the temperature of nano-scale interconnects is computed. The computed results show that the via effect has a great effect on local interconnects, but the reduction of thermal conductivity has little effect on local interconnects. With the reduction of thermal conductivity or the increase of current density, however, the temperature of global interconnects rises greatly, which can result in a great deterioration in their performance. The proposed model can be applied to computer aided design （CAD） of very large-scale integrated circuits （VLSIs） in nano-scale technologies.

关键词： multilevel interconnects temperature distribution self-heating via effect

Influence of plasma on the densification mechanism of SPS under multi-field effect

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International Journal of Minerals,Metallurgy and Materials 2014年第9期21卷 906-912页

作者： Yu-hong Chang Di Huang Cheng-chang Jia Zhao-wen Cui Cong-cong Wang Dong Liang School of Materials Science and Engineering University of Science and Technology Beijing

The densification mechanism of an Fe-based alloy powder containing tiny oxide particles under the synergic multi-field effect of spark plasma sintering （SPS） was investigated. Metallographic microscopy and scanning electron microscopy were used to observe the morphology of samples sintered at different temperatures, and the temperature dislribution in an individual spherical powder particle during sintering was calculated in consideration of the influence of plasma, which was qualified and quantified through the analysis of the U-Icurve. The plasma was observed to play a substantial role in activating and heating the samples at the very early stage of sintering, whereas the joule-heat effect played a dominant role during sintering. Moreover, the plasma also facilitated the diffusion and migration of materials for neck formation.

关键词： iron alloys spark plasma sintering plasma temperature distribution densification diffusion

The use of phase-change cooling strategy in proton exchange membrane fuel cells:A numerical study

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Science China(Technological Sciences) 2021年第12期64卷 2762-2770页

作者： YAN XiaoHui PENG YiMeng SHEN YuanTing SHEN ShuiYun WEI GuangHua YIN JieWei ZHANG JunLiang Institute of Fuel Cells School of Mechanical EngineeringShanghai Jiao Tong UniversityShanghai 200240China MOE Key Laboratory of Power Machinery and Engineering Shanghai Jiao Tong UniversityShanghai 200240China SJTU-Paris Tech Elite Institute of Technology Shanghai Jiao Tong UniversityShanghai 200240China

Thermal management is considered a critical issue in proton exchange membrane fuel cells(PEMFCs),since it not only influences the cell performance but also impacts PEMFC’s reliability and durability.With the ever-increasing power density of PEMFC,traditional cooling approaches including air cooling and water cooling become difficult to meet the demand for highpower heat dissipation.Therefore,phase-change cooling is proposed for fuel cell application in this work,and the potential advantages are discussed and demonstrated via a mathematical model incorporating phase-change heat transfer.The thermal management performance is evaluated by temperature uniformity,maximum temperature difference,and the cooling capacity to compare the difference between phase-change cooling and traditional methods,which demonstrates that phase-change cooling owns a greatly improved thermal management performance.In addition,a simple method to broaden the operating temperature of phase-change cooling based on one certain coolant is offered,which is pressurizing in the coolant channel to regulate the boiling temperature that could further improve the application feasibility of phase-change cooling strategy in fuel cells.

关键词： PEMFC thermal management cooling method temperature distribution phase-change cooling

Investigation of self-adaptive algebraic tomography for gas reconstruction in larger temperature range by multiple wavelengths absorption spectroscopy

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Chinese Optics Letters 2014年第12期12卷 52-58页

作者：李宁吕晓静翁春生 National Key Laboratory of Transient Physics Nanjing University of Science and Technology

We develop a self-adaptive algebraic tomography algorithm （SAATA） to investigate the simultaneons reconstruction of concentration and temperature distributions in larger temperature range from two views. The simplified optical arrangement with fewer projections is realized by extension of spectral information at multiple wavelengths, resulting in great potential in applications of practical combustion diagnosis. Tile results show SAATA can perform much better reconstructions in 300 3000 K temperature range than genetic simulated annealing algorithm and least-square orthogonal-triangular decomposition method with two- wavelength scheme. More phantoms are created to demonstrate the capability of SAATA to capture the peaks and adapt for both flat and sharp temperature distributions. Meanwhile, the advantage of high stability ensures better reconstruction performance at noise levels from 0.1% to 10% in projections.

关键词： Absorption spectroscopy Algebra Algorithms Least squares approximations Simulated annealing temperature distribution Tomography