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一维非线性功能梯度材料的热整流反转 被引量:1
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作者 黄桂芳 詹斯琦 黄维清 《湖南大学学报(自然科学版)》 EI CAS CSCD 北大核心 2015年第10期102-106,共5页
采用非平衡分子动力学方法,研究了一维非线性功能梯度材料的不对称热传导性质.通过耦合两段Frenkel-Kontorova链,并引入线性质量梯度,研究平均温度、界面耦合强度及体系大小对热整流的影响.结果表明,当界面耦合强度较小,并在特定的体系... 采用非平衡分子动力学方法,研究了一维非线性功能梯度材料的不对称热传导性质.通过耦合两段Frenkel-Kontorova链,并引入线性质量梯度,研究平均温度、界面耦合强度及体系大小对热整流的影响.结果表明,当界面耦合强度较小,并在特定的体系中时,通过调节热浴温差来控制系统的热整流方向,无需进行结构重建,在原结构中就能进行热整流方向的控制.讨论了该系统在实验制备及应用方面的可能性. 展开更多
关键词 材料-热传导 热传导-热传导特性 非线性效应
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Design,progress and challenges of 3D carbon-based thermally conductive networks
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作者 JING Yuan LIU Han-qing +2 位作者 ZHOU Feng DAI Fang-na WU Zhong-shuai 《新型炭材料(中英文)》 SCIE EI CAS 2024年第5期844-871,共28页
The advent of the 5G era has stimulated the rapid development of high power electronics with dense integration.Three-dimensional(3D)thermally conductive networks,possessing high thermal and electrical conductivities a... The advent of the 5G era has stimulated the rapid development of high power electronics with dense integration.Three-dimensional(3D)thermally conductive networks,possessing high thermal and electrical conductivities and many different structures,are regarded as key materials to improve the performance of electronic devices.We provide a critical overview of carbonbased 3D thermally conductive networks,emphasizing their preparation-structure-property relationships and their applications in different scenarios.A detailed discussion of the microscopic principles of thermal conductivity is provided,which is crucial for increasing it.This is followed by an in-depth account of the construction of 3D networks using different carbon materials,such as graphene,carbon foam,and carbon nanotubes.Techniques for the assembly of two-dimensional graphene into 3D networks and their effects on thermal conductivity are emphasized.Finally,the existing challenges and future prospects for 3D carbon-based thermally conductive networks are discussed. 展开更多
关键词 Carbon material 3D network Graphene Thermal conductivity Heat transfer
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Microstructure and thermal conductivity of carbon/carbon composites made with different kinds of carbon fibers 被引量:2
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作者 陈洁 龙莹 +1 位作者 熊翔 肖鹏 《Journal of Central South University》 SCIE EI CAS 2012年第7期1780-1784,共5页
The microstructure and surface state of three kinds of polyacrylonitrile-based carbon fibers (T700, T300 and M40) before and after high temperature treatment were investigated. Also, the pyrocarbon and thermal condu... The microstructure and surface state of three kinds of polyacrylonitrile-based carbon fibers (T700, T300 and M40) before and after high temperature treatment were investigated. Also, the pyrocarbon and thermal conductivity of carbon/carbon composites with different carbon fibers as preform were studied. The results show that M40 carbon fiber has the largest crystallite size and the least d002, T300 follows, and TT00 the third. With the increase of heat treatment temperature, the surface state and crystal size of carbon fibers change correspondingly. M40 carbon fiber exhibits the best graphitization property, followed by T300 and then T700. The different microstructure and surface state of different carbon fibers lead to the different microstructures of pyrocarbon and then result in the different thermal conductivities of carbon/carbon composites. The carbon/carbon composite with M40 as preform has the best microstructure in pyrocarbon and the highest thermal conductivity. 展开更多
关键词 carbon fiber thermal conductivity PYROCARBON
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Optimization of volume to point conduction problem based on a novel thermal conductivity discretization algorithm
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作者 杜文静 王沛丽 +1 位作者 宋立鹏 程林 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2015年第7期1161-1168,共8页
A conduction heat transfer process is enhanced by filling prescribed quantity and optimized-shaped high thermal conductivity materials to the substrate. Numerical simulations and analyses are performed on a volume to ... A conduction heat transfer process is enhanced by filling prescribed quantity and optimized-shaped high thermal conductivity materials to the substrate. Numerical simulations and analyses are performed on a volume to point conduction problem based on the principle of minimum entropy generation. In the optimization, the arrangement of high thermal conductivity materials is variable, the quantity of high thermal-conductivity material is constrained, and the objective is to obtain the maximum heat conduction rate as the entropy is the minimum.A novel algorithm of thermal conductivity discretization is proposed based on large quantity of calculations.Compared with other algorithms in literature, the average temperature in the substrate by the new algorithm is lower, while the highest temperature in the substrate is in a reasonable range. Thus the new algorithm is feasible. The optimization of volume to point heat conduction is carried out in a rectangular model with radiation boundary condition and constant surface temperature boundary condition. The results demonstrate that the algorithm of thermal conductivity discretization is applicable for volume to point heat conduction problems. 展开更多
关键词 Volume to point conduction Principle of minimum entropy generation Algorithm of thermal conductivity discretization Optimization
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Material Data Used in TBM Safety Design
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作者 CHEN Zhi 《Southwestern Institute of Physics Annual Report》 2004年第1期95-97,共3页
In CH HCSB TBM(China Helium-Cooled Solider Breeder Test Blanket Module), the structural material (Eurofer), the neutron multiplier (Be), the breeder material(Li4SiO4), and the coolant(He) are used in the des... In CH HCSB TBM(China Helium-Cooled Solider Breeder Test Blanket Module), the structural material (Eurofer), the neutron multiplier (Be), the breeder material(Li4SiO4), and the coolant(He) are used in the design. The parameter selections of materials are very important to the safety design. This paper will provide some parameters of materials property(such as specific heat, thermal conductivity) through calculation. 展开更多
关键词 Specific heat Thermal conductivity
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The Moisturein Capillaries of Building Materials
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作者 Jan Skramlik Miloslav Novotny Karel Suhajda 《Journal of Civil Engineering and Architecture》 2012年第11期1536-1543,共8页
The behavior of building materials in constructions of civil structures is influenced by the surrounding moisture and it is a crucial for intensively examined field of the construction physics. Most standard building ... The behavior of building materials in constructions of civil structures is influenced by the surrounding moisture and it is a crucial for intensively examined field of the construction physics. Most standard building materials are characterized by a porous structure, which results in the ability to receive water in a liquid as well as gaseous form in the inner pores. The water fills the storage space of pores under certain conditions; it is transported and transferred back to the surroundings. Many technical studies show that the moisture monitoring is prevailingly based on experiments. Previous calculating methods introduced, e.g., by Glaser, which became the basis for the standard calculations in many European countries in the 1960s, are not always sufficient with respect to the demands of the civil structures. The moisture influences thermo-insulating properties of the material. By a change of the thermo insulation properties of the construction also the thermal and diffusion scheme of the construction is changed and its thermal resistance is decreasing. Faults in the thermo-technical projects occur when thermal conductivity coefficient L values for material in a dry state are substituted.The aim of the research is to determine the capillary conductivity coefficient as a characteristic material moisture parameter of the building materials by the means of a non-destructive method using the experimentally assembled apparatus developed at the Department of Civil Engineering, Brno University of Technology. Keywords: Capillary conductivity coefficient, moisture transfer, EMWR (electromagnetic microwave radiation), diffusion 展开更多
关键词 Capillary conductivity coefficient moisture transfer EMWR (electromagnetic microwave radiation) diffusion.
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One-Dimensional Analysis of Supersonic Two-Stage HVOF Process
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作者 Hiroshi KATANODA Junichi HAGI Minoru FUKUHARA 《Journal of Thermal Science》 SCIE EI CAS CSCD 2009年第4期332-337,共6页
The one-dimensional calculation of the gas/particle flows of a supersonic two-stage high-velocity oxy-fuel(HVOF) thermal spray process was performed. The internal gas flow was solved by numerically integrating theequa... The one-dimensional calculation of the gas/particle flows of a supersonic two-stage high-velocity oxy-fuel(HVOF) thermal spray process was performed. The internal gas flow was solved by numerically integrating theequations of the quasi-one-dimensional flow including the effects of pipe friction and heat transfer. As for the supersonicjet flow, semi-empirical equations were used to obtain the gas velocity and temperature along the centerline. The velocity and temperature of the particle were obtained by an one-way coupling method. The material ofthe spray particle selected in this study is ultra high molecular weight polyethylene (UHMWPE). The temperaturedistributions in the spherical UHMWPE particles of 50 and 150 m accelerated and heated by the supersonic gasflow was clarified. 展开更多
关键词 Compressible Flow Supersonic Flow Two-Stage HVOF Thermal Spray One-Dimensional Analysis UHMWPE
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Homogenization for Periodic Heterogeneous Materials with Arbitrary Position-Dependent Material Properties
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作者 徐志杰 《Communications in Theoretical Physics》 SCIE CAS CSCD 2012年第8期189-194,共6页
We present a rigorous homogenization approach for elcient computation of a class of physical problems in a one-dimensional periodic heterogeneous material. This material is represented by a spatially periodic array of... We present a rigorous homogenization approach for elcient computation of a class of physical problems in a one-dimensional periodic heterogeneous material. This material is represented by a spatially periodic array of unit cells with a length of More specifically, the method is applied to the diffusion, heat conduction, and wave propagation problems. Heterogeneous materials can have arbitrary position-dependent continuous or discontinuous materials properties (for example heat conductivity) within the unit cell. The final effective model includes both effective properties at the leading order and high-order contributions due to the microscopic heterogeneity. A dimensionless heterogeneity parameter ~ is defined to represent high-order contributions, shown to be in the range of [-1/12, 0], and has a universal expression for all three problems. Both effective properties and heterogeneity parameter 13 are independent oft, the microscopic scale of heterogeneity. The homogenized solution describing macroscopic variations can be obtained from the effective model. Solution with sub-unit-cell accuracy can be constructed based on the homogenized solution and its spatial derivatives. The paper represents a general approach to obtain the effective model for arbitrary periodic heterogeneous materials with position-dependent properties. 展开更多
关键词 DIFFUSION conduction wave HOMOGENIZATION MULTI-SCALE upscaling DISPERSIVE
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Thermal Radiative Properties of Xonotlite Insulation Material 被引量:5
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作者 Xinxin ZHANG Gaosheng WEI Fan YU 《Journal of Thermal Science》 SCIE EI CAS CSCD 2005年第3期281-283,253,共4页
This paper presents experimental results of thermal radiative properties of xonotlite-type calcium silicate insulation material. Transmittance spectra were first taken using Fourier transform infrared spectrometer (F... This paper presents experimental results of thermal radiative properties of xonotlite-type calcium silicate insulation material. Transmittance spectra were first taken using Fourier transform infrared spectrometer (FTIR) for the samples with p = 234 kg/m^3. Specific extinction coefficient spectra were then obtained by applying Beer's law. Finally, by using the diffusion approximation, the specific Rossland mean extinction coefficients and radiative thermal conductivities were obtained for various temperatures. The results show that the specific spectral extinction coefficient of xonotlite is larger than 7 m^2/kg in the whole measured spectra, and diffusion approximation equation is a reasonable description of radiative heat transfer in xonotlite insulation material. The specific Rossland mean extinction coefficient of xonotlite has a maximum value at 400 K and the radiative thermal conductivity is almost proportional to the cube of temperature. 展开更多
关键词 XONOTLITE INSULATION radiative properties extinction coefficient
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Inverse Radiation Problem of Boundary IncidentRadiation Heat Flux in Semitransparent Planar Slabwith Semitransparent Boundaries 被引量:1
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作者 LiunLinhua TanHeping 《Journal of Thermal Science》 SCIE EI CAS CSCD 1998年第2期131-138,共8页
An inverse method is presented for estimating the unknown boundary incident radiation heat flux onone side of one-dimensional semitransparent planar slab with semitransparent boundaries from theknowledge of the radiat... An inverse method is presented for estimating the unknown boundary incident radiation heat flux onone side of one-dimensional semitransparent planar slab with semitransparent boundaries from theknowledge of the radiation intensities exiting from the other side. The inverse problem is solved usingconjugate gradient method of minimization based on discrete ordinates method (DOM) of radiativetransfer equation. The equations of sensitivity coefficients are derived and easily solved by DOM, withthe result that the complicated numerical differentiation commonly used in solving sensitivity coefficients is avoided. The effects of anisotropic scattering, absorption coefficient, scattering coefficient,boundary reflectivity, fluid temperature outside the boundaries, convection heat transfer coefficients,conduction coefficient of semitransparent media and slab thickness on the accuracy of the inverse analysis are investigated. The results show that the boundary incident radiation heat flux can be estimatedaccurately, even with noisy data. 展开更多
关键词 inverse radiative problem radiation heat flux discrete ordinates method conjugate gradient method
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Controlling Thermal Conduction by Graded Materials 被引量:1
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作者 Qin Ji Ji-Ping Huang 《Communications in Theoretical Physics》 SCIE CAS CSCD 2018年第4期434-440,共7页
Manipulating thermal conductivities are fundamentally important for controlling the conduction of heat at will. Thermal cloaks and concentrators, which have been extensively studied recently, are actually graded mater... Manipulating thermal conductivities are fundamentally important for controlling the conduction of heat at will. Thermal cloaks and concentrators, which have been extensively studied recently, are actually graded materials designed according to coordinate transformation approaches, and their effective thermal conductivity is equal to that of the host medium outside the cloak or concentrator. Here we attempt to investigate a more general problem: what is the effective thermal conductivity of graded materials? In particular, we perform a first-principles approach to the analytic exact results of effective thermal conductivities of materials possessing either power-law or linear gradation profiles. On the other hand, by solving Laplace's equation, we derive a differential equation for calculating the effective thermal conductivity of a material whose thermal conductivity varies along the radius with arbitrary gradation profiles.The two methods agree with each other for both external and internal heat sources, as confirmed by simulation and experiment. This work provides different methods for designing new thermal metamaterials(including thermal cloaks and concentrators), in order to control or manipulate the transfer of heat. 展开更多
关键词 thermal metamaterials graded materials effective thermal conductivity
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Enhancing solar steam generation using a highly thermally conductive evaporator support 被引量:8
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作者 Yida Wang Xuan Wu +4 位作者 Pan Wu Jingyuan Zhao Xiaofei Yang Gary Owens Haolan Xu 《Science Bulletin》 SCIE EI CSCD 2021年第24期2479-2488,M0004,共11页
Interfacial solar steam generation is an efficient water evaporation technology which has promising applications in desalination,sterilization,water purification and treatment.A common component of evaporator design i... Interfacial solar steam generation is an efficient water evaporation technology which has promising applications in desalination,sterilization,water purification and treatment.A common component of evaporator design is a thermal-insulation support placed between the photothermal evaporation surface and bulk water.This configuration,common in 2-dimensional(2 D)evaporation systems,minimizes heat loss from evaporation surface to bulk water,thus localizing the heat on the evaporation surface for efficient evaporation.This design is subsequently directly adopted for 3-dimensional(3 D)evaporators without any consideration if it is appropriate.However,unlike 2 D solar evaporators,the 3 D evaporators can also harvest additional energy(other than solar light)from the air and bulk water to enhance evaporation rate.In this scenario,the use of thermal insulator support is not proper since it will hinder energy extraction from water.Here,the traditional 3 D evaporator configuration was completely redesigned by using a highly thermally conductive material,instead of a thermal insulator,to connect evaporation surfaces and the bulk water.Much higher evaporation rates were achieved by this strategy,owing to the rapid heat transfer from the bulk water to the evaporation surfaces.Indoor and outdoor tests both confirmed that evaporation performance could be significantly improved by substituting a thermal insulator with thermally conductive support.These findings will redirect the future design of 3 D photothermal evaporators. 展开更多
关键词 Solar steam generation Photothermal materials Heat conduction Reduced graphene oxide Water evaporation 3D evaporator
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Numerical study on solid–liquid phase change in paraffin as phase change material for battery thermal management 被引量:3
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作者 Qiannan Zhang Yutao Huo Zhonghao Rao 《Science Bulletin》 SCIE EI CAS CSCD 2016年第5期391-400,共10页
With the large latent heat and low cost, the paraffin has been widely used in battery thermal management(BTM) system to improve the efficiency and cycling life of power battery. The numerical model of paraffin melting... With the large latent heat and low cost, the paraffin has been widely used in battery thermal management(BTM) system to improve the efficiency and cycling life of power battery. The numerical model of paraffin melting in a cavity has been established, and the effects on the solid–liquid phase change process have been investigated for the purpose of enhancing the heat transfer performance of paraffin-based BTM system. The results showed that the location of the heating wall had great effects on the melting process. The paraffin in the cavity melted most quickly when the heating wall located at the bottom. Furthermore, the effects of thermal conductivity and the velocity of the slip wall have been considered. The gradient of liquid fraction increased with the increase in thermal conductivity, and the melting process could be accelerated or delayed by the slip wall with different velocity. 展开更多
关键词 Phase change material Battery thermal management Solid–liquid phase change Heat flux Thermal conductivity
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Homogenization and Upscaling for Diffusion,Heat Conduction,and Wave Propagation in Heterogeneous Materials
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作者 徐志杰 《Communications in Theoretical Physics》 SCIE CAS CSCD 2012年第3期348-354,共7页
We present a general homogenization method a periodic heterogeneous material with piecewise constants for diffusion, heat conduction, and wave propagation in The method is relevant to the frequently encountered upsca... We present a general homogenization method a periodic heterogeneous material with piecewise constants for diffusion, heat conduction, and wave propagation in The method is relevant to the frequently encountered upscaling issues for heterogeneous materials. The dispersion relation for each problem is first expressed in the general form where the frequency co (or wavenumber k) is expanded in terms of the wavenumber k (or frequency ω). A general homogenization model can be directly obtained with any given dispersion relation. Next step we study the unit cell of the heterogeneous material and derive the exact dispersion relation. The final homogenized equations include both leading order terms (effective properties) and high order contributions that represent the effect of the microscopic heterogeneity on the macroscopic behavior. That effect can be lumped into a single dimensionless heterogeneity parameter β, which is bounded between -1/12≤β≤ 0 and has a universal expression for all three problems. Numerical examples validate the proposed method and demonstrate a significant computational saving. 展开更多
关键词 DIFFUSION conduction wave HOMOGENIZATION MULTI-SCALE DISPERSION upscaling HETEROGENEOUS
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