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Use of improved cold-finger technique to assess effects of basicity on heat transfer through solidified mold flux

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Journal of Iron and Steel Research International 2019年第4期26卷 393-402页

作者： Karina Lara Santos Assis Petrus Christiaan Pistorius Department of Materials Science and Engineering Center for Iron and Steelmaking ResearchCarnegie Mellon UniversityPittsburgh 15213PAUSA

Cold-finger measurements were used to estimate the contact resistance and average thermal conductivity of mold flux films solidified on a water-cooled copper *** industrial mold fluxes,with basicities from low to high,were *** steady-state rate of convective heat transfer between the solid film and liquid flux was compared with calculations based on natural convection correlations;the comparison indicates that the surface of the solid film(in contact with molten flux)is approximately at its solidus *** roughness of the mold flux film in contact with copper was larger for films grown from higher-temperature mold flux and for higher-basicity mold *** glassy(low-basicity)film had an estimated thermal conductivity of 1.1 W/(m K).The crystalline or partially crystalline films had higher estimated thermal conductivities of 2.2-3.2 W/(m K).The measured values of thermal resistance were extrapolated to typical mold flux film thicknesses for industrial conditions;the extrapolations confirmed that the high contact resistance of higher-basicity mold fluxes can yield higher thermal resistances than the low-basicity *** morphology of the rough interface of higherbasicity mold flux films that gives the higher contact resistance is consistent with that observed in previous work and appears not to be directly related to crystallization.

关键词： Mold flux Heat transfer Conduction Contact resistance-Cold-finger technique

Targeted energy transfer of a parallel nonlinear energy sink

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Applied Mathematics and Mechanics(English Edition) 2019年第5期40卷 621-630页

作者： Yimin WEI Sha WEI Qianlong ZHANG Xinjian DONG Zhike PENG Wenming ZHANG State Key Laboratory of Mechanical System and Vibration Shanghai Jiao Tong University

A parallel nonlinear energy sink(NES) is proposed and analyzed. The parallel NES is composed of a vibro-impact(VI) NES and a cubic NES. The dynamical equation is given, and the essential analytical investigation is carried out to deal with the cubic nonlinearity and impact nonlinearity. Multiple time-scale expansion is introduced, and the zeroth order is derived to give a rough outline of the system. The underlying Hamilton dynamic equation is given, and then the optimal stiffness is expressed. The clearance is regarded as a critical factor for the VI. Based on the periodical impact treatment by analytical investigation, the relationships of the cubic stiffness, the clearance, and the zeroth-order attenuation amplitude of the linear primary oscillator(LPO) are obtained.A cubic NES under the optimal condition is compared with the parallel NES. Harmonic signals, harmonic signals with noises, and the excitation generated by a second-order?lter are considered as the potential excitation forces on the system. The targeted energy transfer(TET) in the designed parallel NES is shown to be more e?cient.

关键词： targeted energy transfer (TET) nonlinear energy sink (NES) nonlinear vibration absorber impact vibration reduction

Flow and heat transfer of liquid slag in a continuous casting mold

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Journal of Iron and Steel Research International 2019年第9期26卷 926-940页

作者： Hai-biao Lu Chang-gui Cheng Yang Li Xu-feng Qin Yan Jin The State Key Laboratory of Refractories and Metallurgy Wuhan University of Science and TechnologyWuhan 430081HubeiChina Hubei Provincial Key Laboratory for New Processes of Ironmaking and Steelmaking Wuhan University of Science and TechnologyWuhan 430081HubeiChina

A three-dimensional mathematical model for coupled liquid steel and liquid slag was established to study the flow and heat transfer behavior of liquid slag. Based on the volume of fluid method and the heat transfer model, the effect of different casting parameters on the flow and heat transfer of the liquid slag was investigated. The results show that there are two different size recirculation zones of the liquid slag layer on the liquid steel in the mold center plane, extending from the submerged entry nozzle to the mold narrow face. With the increase in the casting speed and the decrease in the viscosity of the mold flux, the overall velocity and the temperature of the liquid slag increase. With the increase in the inclination angle and the submergence depth of the submerged entry nozzle, the temperature of the liquid slag decreases, and the velocity decreases near the mold narrow face and increases in the vicinity of the submerged entry nozzle. The inactive flow field and the low temperature of liquid slag within 100 mm of the submerged entry nozzle may intensify the surface longitudinal cracking sensitivity of the slab. When the lubrication and heat transfer are well regulated between the surface of mold and the mold flux film, low casting speed, large inclination angle and submergence depth of the submerged entry nozzle are beneficial for reducing the possibility of a slab surface longitudinal crack.

关键词： Continuous casting Liquid slag Flow Heat transfer Surface longitudinal cracking sensitivity Mathematical simulation

Strong interfacial charge transfer between hausmannite manganese oxide and alumina for efficient photocatalysis

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Chinese Journal of Chemical Engineering 2021年第5期34卷 147-159页

作者： Aisha Kanwal Shamaila Sajjad Sajjad Ahmed Khan Leghari Muhammad Naeem Khan International Islamic University H-10 IslamabadPakistan Pakistan Institute of Engineering and Applied Sciences Islamabad 44000Pakistan Department of Chemistry Government College of ScienceLahorePakistan

Well crystalline manganese oxide(Mn_(3)O_(4))nanoparticles anchored on gamma alumina(γ-Al_(2)O_(3))have been successfully tailored via a proficient and cost effective chemical process as an efficient material for photo *** indicated the composite formation ofγ-Al_(2)O_(3) and hausmannite structure of Mn_(3)O_(4).SEM and TEM revealed that hetero structure of Mn_(3)O_(4)/γ-Al_(2)O_(3) exhibits an amalgam of aggregated nanoparticles and *** demonstrated the chemical states of binary *** band gap tuning has been performed withγ-Al_(2)O_(3) nanoparticles by assimilating hausmannite Mn_(3)O_(4) particles into flower like microstructure of Al_(2)O_(3).The photoluminescence spectra affirmed the enhancement in charge separation in Mn_(3)O_(4)/γ-Al_(2)O_(3) binary hybrid *** band gap becomes narrow with the increase in concentrations of Mn_(3)O_(4).The narrowing of band gap is concorded with crystalline domains of primary aggregated *** elucidate the mechanism of the photocatalytic activity linear sweep voltammetry was *** results showed that Mn_(3)O_(4)/γ-Al_(2)O_(3) nanocomposite revealed the enhancement in current density as compared to pureγ-Al_(2)O_(3) which confirmed the electron transfer from Mn_(3)O_(4) toγ-Al_(2)O_(3) through the interfacial potential gradient in conduction *** optimum concentration of 6.0%Mn_(3)O_(4)/γ-Al_(2)O_(3) for hybrid structure showed an excellent photocatalytic activity under visible light due to narrow band gap *** degree distribution of Mn_(3)O_(4) nano architects overlying onγ-Al_(2)O_(3) induces a significant synergic effect betweenγ-Al_(2)O_(3) and hausmannite phase of manganese oxide(Mn_(3)O_(4)).This strong interfacial contact betweenγ-Al_(2)O_(3) and Mn_(3)O_(4) endures the quick transfer of photo generated charge carriers across interface.

关键词： Hausmannite Mn_(3)O_(4) Alumina Band gap tuning Interfacial charge transfer Nanomaterials Catalysis

Experimental investigation on boiling heat transfer characteristics of Al_2O_3-water nanofluids in swirl microchannels subjected to an acceleration force

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Chinese Journal of Aeronautics 2019年第5期32卷 1136-1144页

作者： Sujun DONG Hongsheng JIANG Yongqi XIE Xiaoming WANG Zhongliang HU Jun WANG School of Aeronautic Science and Engineering Beihang University AVIC Chengdu Aircraft Design and Research Institute School of Chemical and Process Engineering University of Leeds

Experiments were carried out to investigate the boiling heat transfer characteristics of Al_2O_3-water nanofluids in swirl microchannels under terrestrial gravity and acceleration fields. A centrifuge with a two-meter long rotational arm was used to simulate the acceleration magnitude up to 9 g and three various acceleration directions. Three test sections with different geometric parameters were applied. The volume concentration of Al_2O_3 nanoparticles with an average diameter of 13 nm was varied from 0.07% to 0.1%. The mass flow rate and vapor quality were in ranges of 3–6 kg/h and 0.4–1.0%, respectively. The effects of the mass flow rate, microchannel aspect ratio,vapor quality, nanoparticle volume concentration, and acceleration direction and magnitude were analyzed in a systematic manner. Experimental results showed that the acceleration direction and magnitude had significant influences on the boiling heat transfer. The heat transfer under configuration C was found to be superior to that under configurations A and B. Moreover, the heat transfer coefficient increased with increases of the mass flow rate and the volume concentration and decreased with the aspect ratio.

关键词： Acceleration Boiling heat transfer Microchannel Nanofluid Swirl microchannels

transfer OF FOREIGN GENES BY ELECTROPORATION AND THEIR EXPRESSION IN MAMMALIAN CELLS

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Science China Chemistry 1989年第5期32卷 543-550页

作者：杨建涛王秀琴吴旻 Institute of Cancer Chinese Academy of Medical Sciences Beijing

Expression of foreign genes transferred into mammalian cells by electroporation has been studied. The pX1TK gene, pSV2Neo gene and pUCEJ oncogene have been introduced into MLTK-cells and NIH/3T3 cells, respectively. Stable transformation transient expression of TK gene by MLTK-cells as well as stable and malignant transformation of NIH/3T3 cells have been obtained. Transient expression frequency is about 80% and stable transformation frequency is about 10^(-4). Integration of foreign genes into the cellular genome was verified with molecular hybridization. Tumor development was observed after inoculation of transformed celts into nude mice.

关键词： gene transfer gene expression oncogene electroporation.

Sound Source Localisation for a High-Speed Train and Its transfer Path to Interior Noise

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Chinese Journal of Mechanical Engineering 2019年第4期32卷 168-183页

作者： Jie Zhang Xinbiao Xiao Xiaozhen Sheng Zhihui Li State Key Laboratory of Traction Power Southwest Jiaotong University

Noise is one of the key issues in the operation of high-speed railways, with sound source localisation and its transfer path as the two major aspects. This study investigates both the exterior and interior sound source distribution of a high-speed train and presents a method for performing the contribution analysis of airborne sound with regard to the interior noise. First, both exterior and interior sound source locations of the high-speed train are identified through in-situ measurements. Second, the sound source contribution for di erent regions of the train and the relationships between the exterior and interior noises are analysed. Third, a method for conducting the contribution analysis of airborne sound with regard to the interior noise of the high-speed train is described. Lastly, a case study on the sidewall area is carried out, and the contribution of airborne sound to the interior noise of this area is obtained. The results show that, when the high-speed train runs at 310 km/h, dominant exterior sound sources are located in the bogie and pantograph regions, while main interior sound sources are located at the sidewall and roof. The interior noise, the bogie area noise and the sound source at the middle of the coach exhibit very similar rates of increase with increasing train speed. For the selected sidewall area, structure-borne sound dominates in most of the 1/3 octave bands.

关键词： High-speed train Interior noise Sound transfer path Noise source identification Exterior noise Airborne sound

Study on Laminar Natural Convection Heat transfer from a Hemisphere with Uniform Heat Flux Surface

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Journal of Thermal Science 2019年第2期28卷 232-245页

作者： ZHANG Jian LIU Jie LU Wenqiang School of Engineering Science University of Chinese Academy of Sciences

By employing the modified model based on Bejan et al., laminar natural convection heat transfer from a hemisphere with uniform heat flux surface has been numerically investigated. Extensive results of two different surface boundary conditions are obtained for a wide range of Grashof numbers(10 ≤ Gr ≤ 10~7) and Prandlt number of 0.72. The characteristics of heat transfer and fluid flow are analyzed in terms of isotherm contours and streamline patterns, radial and tangential velocities, dimensionless temperature profiles, local friction and pressure drag coefficients, as well as local and average Nusselt numbers. Meanwhile, the effects of Grashof number and adiabatic surface on flow motion and heat transfer have been studied. No recirculation zone or flow separation generates over the top of the hemisphere compared to the isothermal sphere. Owing to the curvature effect, the maximum values of local friction and pressure drag coefficients appear at the corner point B. Comparisons with the previous results are also reported in detail. All the results are in good agreement with the numerical data. Moreover, both local and average Nusselt numbers show a positive dependence on Grashof number. The values of the non-adiabatic case are smaller than that of the adiabatic case due to the preheating effect. Finally, two precise and general correlations of average Nusselt number varying with Grashof numbers have been presented, which can provide an effective prediction for the heat transfer rate in engineering applications, and offer academic values for the future research.

关键词： numerical simulation natural convection hemisphere uniform heat flux heat transfer correlations

Radiative heat transfer and thermal characteristics of Fe-based oxides coated SiC and Alumina RPC structures as integrated solar thermochemical reactor

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Science China(Technological Sciences) 2018年第12期61卷 1788-1801页

作者： GUENE LOUGOU Bachirou SHUAI Yong PAN RuMing CHAFFA Gédéon AHOUANNOU Clément ZHANG Hao TAN HePing Key Laboratory of Aerospace Thermophysics of Ministry of Industry and Information Technology Harbin Institute of Technology School of Energy Science and Engineering Harbin Institute of Technology Laboratory of Energetics and Applied Mechanics (LEMA) Polytechnic College of Abomey-Calavi Abomey-Calavi University

This paper investigated radiative heat transfer and thermal characteristics of Fe-based oxides coated SiC and Alumina reticulated porous ceramic structures as integrated solar thermochemical ***-flux solar radiation absorption and axial temperature distribution in the ceramic foams reactor were analyzed by adopting surface-to-surface radiation model coupled to the P1approximation for radiation heat *** radiative heat transfer and thermal characteristics of different foam-type RPC structures,including SiC,CeO_2,FeAl_2O_4,NiFeAlO_4,Fe_3O_4/SiC,and NiFe_2O_4/SiC were *** mass flow rate and foam structural parameters,including the permeability,pore mean cell size,and extinction coefficients have significantly affected the axial temperature distribution,pressure drop,heat transfer,and fluid *** porous structure to the solar receiver could maximize the incorporation of redox powder in the reacting medium,lower the pressure drop,and enhance the thermal performance of the thermochemical reacting *** structure was the candidate materials in the case where more heat flux and high axial temperature distribution is ***,Fe-based oxide coated Al_2O_3structure could be considered regarding the heat transfer enhancement along with the catalyst activity of oxygen carriers for solar thermochemical reacting system performance.

关键词： solar thermochemical reactor reticulated porous ceramics heat transfer and fluid flow pore mean cell size permeability and pressure drop