科创中国

Metallic nanowires are widely used in energy conversion and storage, especially in the thermal management area, because of their high specific surface area, rich active sites, and high thermal conductivity. Metallic nanowires, such as copper or silver nanowires, are extensively applied to prepare the next-generation thermal interface materials with excellent thermal conductivity, light weight, high strength and ductility. Metallic hollow nanowires, which hold the typical one-dimension hollow nanostructures, have high axial thermal conductivity to prepare advanced thermal interface materials applied in thermal management and waste heat recovery of high-power microelectronic devices. Thermal conductivity is one of the most important indicators to assess the thermal performance of thermal interface materials. Over the past decades, many studies in both theory and experiment have been carried out to evaluate the thermal conductivity of solid nanowires. Molecular dynamics (MD) simulation has been applied to calculate the thermal conductivity of single nanowires, single core-shell nanowires and super-lattice nanowires. Meanwhile, advanced measuring techniques, including 3ω method, Raman spectroscopy and T-type method, have been invented and developed to measure the thermal conductivity of single nanowires. However, investigations on the thermal conductivity of metallic hollow nanowires are limited. Considering the difficulty in the fabrication and thermal conductivity measurement of single hollow metallic nanowires, creating a theoretical thermal conductivity model is urgently required. This work developed the electrical thermal conductivity model, phonon thermal conductivity model and phonon specific heat model of metallic nanowires to study the size effect on the mean free path, group velocity and specific heat capacity of the material. This study also proposed the effective thermal conductivity model of metallic hollow nanowire. These models have been used to study the effect of the both length and thickness of the metallic hollow nanowire on the effective thermal conductivity as well as the influence of the wall thickness on the electronic and phonon thermal conductivity. Finally, the mechanism of size effect on the thermal conductivity was discussed, and a reasonable interpretation based on the developed model was also proposed. Results show that an exact thermal conductivity model, validated by the experimental data from open-reported literature, was established with a correlation coefficient high than 90%. The size effect on the thermal conductivity of both hollow copper nanowire and solid copper nanowire was observed with the increased length and thickness. The thermal conductivity of solid copper nanowire was about 1.2 times higher than that of the hollow copper nanowire with the same length of 800 nm. In detail, the electronic thermal conductivity of solid copper nanowire was nearly 18.7% higher than that of hollow copper nanowire, while their phonon thermal conductivities almost remained unchanged. The size effect on the specific heat of hollow copper nanowire was also observed. The thermal conductivity of the hollow copper nanowire was 1.6 times higher than that of bulk copper and 1.2 times higher than that of a solid copper nanowire with the similar thickness.

Zizhen Lin;雅玲 何;印实 李

Kexue Tongbao/Chinese Science Bulletin

2019-2-15

Chao Xu;雅玲 何;文铨 陶

Shanghai Ligong Daxue Xuebao/Journal of University of Shanghai for Science and Technology

2003-12

A numerical study was performed to investigate the liquid film cooling in a rocket combustion chamber. The finite volume method was employed to solve simultaneously the respective governing equations for the liquid film and gas stream. The standard turbulence k-ε model was used to simulate the turbulence gas flow and a modified Van Driest model was adopted to simulate the turbulent liquid film flow. Radiation of gas stream was also considered and simulated with the FLUX model. Downstream of the liquid film dryout point the gaseous film cooling was numerically studied. Mass, momentum, and heat transfer characteristics at the interface were investigated. The results show that heat transfer at the gas-liquid interface in a rocket combustion chamber with insulated wall is mainly dominated by the convection of the free stream and transport of latent heat associated with the evaporation of the liquid film. In addition, the effects of the radiation and sensible heat transfer cannot be ignored Various effects on the liquid film length were also examined. The numerical predictions agree well with the experimental data for the liquid film length.

Hongwei Zhang;文铨 陶;雅玲 何;Zhenping Feng

Hsi-An Chiao Tung Ta Hsueh/Journal of Xi'an Jiaotong University

2006-7

The oscillatory ow field at the end of the parallel-stacks is visualized using Particle Image Velocimetry (PIV) measurement. The vortex shedding at the end of parallel-stacks in the engines was measured. The velocity distributions along the x-axis in the center of the channels are exhibited. The results show that the vortex influence area expands and the symmetrical vertex becomes non- symmetrical, as the increasing of the drive ratio (Dr is the ratio of the pressure amplitude and the mean pressure). The plate end shape has evident influence on the vortex configuration. The vortex is circular around the circular end and is attached close to the plate at the triangular end. This work will be favor for the understanding of interaction between the oscillatory flow and the heat transfer at the end of the stacks.

Dong Wei Zhang;雅玲 何;Yong Wang;文铨 陶

Kung Cheng Je Wu Li Hsueh Pao/Journal of Engineering Thermophysics

2012-3

Numerical studies are presented for two-dimensional Rayleigh-Bénard convection in a large scope of Ra number using a lattice Boltzmann method based on interpolation. In the simulation, various ratios of interpolation are adopted for corresponding Ra numbers. Numerical results such as the maximal time dependent vertical velocities of the system, steady-state streamlines and isotherms, Nu numbers as a function of Ra numbers, and the profiles of the average temperature of the horizontal sections near the walls are presented. Such results are consistent with those from previous references.

Yong Wang;雅玲 何;Chang Qing Tong;Ying Wen Liu

Kung Cheng Je Wu Li Hsueh Pao/Journal of Engineering Thermophysics

2007-3

During the operation of alkaline direct liquid fuel cells, the alkaline electrolyte is usually needed in the anode electrode to accelerate the electrochemical reaction kinetics of the liquid fuel. However, the crossover of the alkaline solution in the anode through the anion exchange membrane to the cathode can increase the transfer resistance of the oxygen in the cathode. In order to reduce the crossover of the alkaline solution, the diffusion process of the alkaline solution in the anion exchange membrane needs to be fully understood. In this work, interface models of anion exchange membrane-alkaline electrolytes are established based on the cell structure of the quaternary ammonium polysulfone (QAPS) membrane to simulate the dynamic process of the alkaline solution in the membrane. The effect of the type and the concentration of the alkaline solution on the transportation of the metal ions and OH⁻ in the membrane are studied. The results show that the agglomeration of Na⁺ is formed more easily than K⁺ in the interface model. Because of the strong interaction of Na⁺ on OH⁻, OH⁻ ions appear to be concentrated, resulting in that the diffusion coefficients of the metal ion and OH⁻ in the in Na⁺ solution are lower than those in the K⁺ solution. In addition, with the raised concentration of electrolyte solution, the aggregation degrees of the metal ions and OH⁻ can be increased, which means an enlarged mass transfer resistance of the components. Furthermore, by adding a polytetrafluoroethylene (PTFE) layer on the QAPS membrane, the distribution of metal ions tends to be concentrated, and the number of hydrophilic channels in the QAPS membrane is reduced, which significantly increases the alkali resistance of the anion exchange membrane.

Bing Ye Song;Dong Li;雅玲 何;Dong Huang;Zi Xiang Tong

Science China Technological Sciences

2020

In this paper, a comprehensive thermo-hydraulic performance evaluation for air flow across the hexagon-like and circular-like staggered pin finned tube bundle heat transfer surfaces has been numerically carried out by adopting the performance evaluation plot of enhanced heat transfer techniques oriented for energy-saving. In addition, the simulation results have also been analyzed from the viewpoints of field synergy principle and entransy dissipation extreme principle. The results indicate that the heat transfers are all enhanced based on identical pressure drop for the hexagon-like and circular-like pin finned tube bundles within the inlet velocity range from 1 m/s to 10 m/s studied. Moreover, the circular-like pin finned tube bundle offers the lowest friction factor increase ratio for the same Nusselt number increase ratio. Furthermore, the synergy between velocity and fluid temperature gradient has been proved again, having inherent consistency with the dissipation of entransy.

En Tian;雅玲 何;文铨 陶

Heat Transfer Engineering

2018-8-27

In this paper, the Lattice Boltzmann method (LBM) is adopted to simulate the incompressible flow in porous media on non-uniform grids. The flow through porous media was simulated by including the porosity into the equilibrium distribution function and adding a force term to the evolution equation to account for the linear and non-linear drag forces of the porous medium. Besides, non-uniform grids are adopted by using the interpolation-supplemented Lattice Boltzmann equation. Numerical simulations of lid-driven cavity flow, flow in a 2D symmetric sudden expansion channel, and cavity flow in polar coordinates are carried out. The results agree well with benchmark solutions, experimental data or traditional computational fluid dynamics method solutions. The present results demonstrate the potential of the Lattice Boltzmann algorithm for numerical simulation of fluid through porous media.

H. R. Wu;雅玲 何;G. H. Tang;文铨 陶

Progress in Computational Fluid Dynamics

2005

The effect of erosion speed on the interaction between erosion and corrosion of the Fe-3.5 wt% B alloy in a flowing zinc bath has been investigated using a rotating-disk technique. The total erosion-corrosion rate increases rapidly, whereas the pure erosion rate tends to increase linearly with an increase in erosion speed and with low damage. The increase in total erosion-corrosion rate is strongly dependent on erosion-corrosion interaction. During the erosion-corrosion process, the severe corrosion reaction roughens the surface by forming a loose corrosion layer and cracks in the anticaustic Fe₂B skeleton, which eventually facilitates erosion. The micromechanical scouring effect of liquid zinc worsens corrosion by accelerating the removal of corrosion products and causing spallation of anticaustic Fe₂B. An increase in erosion speed intensifies the micromechanical scouring effect of flowing zinc significantly. A strong erosion-corrosion interaction occurs at high erosion speed, which leads to a greater material loss rate.

Yong Wang;建东 邢;Shengqiang Ma;Guangzhu Liu;雅玲 何;Sen Jia;Yaping Bai

Journal of Materials Research

2015-11-17

The amount and isosteric heat of CO₂ adsorption in copper benzene-1,3,5-tricarboxylate (Cu-BTC) metal organic framework are synchronously experimentally studied with the combined PCTProE&E and Calvet Calorimeter under the ambient temperature of 35 °C and pressure range 0-1200 kPa. A grand canonical Monte Carlo numerical model is proposed to predict the CO₂ adsorption amount combined with isosteric heat. The numerical model is validated with experimental data, and the obtained adsorption snapshots can provide a deep insight for the adsorption structure at molecular level. The CO₂ adsorption amount and heat have three contributions: the Lennard-Jones potential, electrostatic interactions between CO₂ and Cu-BTC, and electrostatic interactions between CO₂ and CO₂. The contribution rate ranges for the adsorption amount of the three mechanisms are 48.45-69.66%, 28.43-48.41%, and 1.91-3.14%, respectively. The third contribution can be ignored. The L-J potential controls the adsorbed CO₂ molecules in the tetrahedron-shaped pockets of Cu-BTC, whereas the electrostatic interactions between CO₂ and Cu-BTC control the adsorbed CO₂ molecules in the larger square-shaped channels of Cu-BTC.

H. Wang;治国 屈;W. Zhang;Q. N. Yu;雅玲 何

International Journal of Heat and Mass Transfer

2016-1-1