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采用激光光热透射技术测量材料的热扩散率 总被引:2,自引:0,他引:2
介绍利用激光光热透射技术测量材料热扩散率的方法,用该方法测量黄铜,纯铁、铝、纯铜及锗的热扩散率,其结果与能常采用的检测手段一致。 相似文献
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宏观碳纳米管(Carbon nanotube,CNT)薄膜的成功制备是发展有机热电材料的一个重要方向。由于CNT薄膜厚度仅为200 nm且多孔、粗糙度大,对其热学特性表征极为困难。本文提出应用3ω技术测量由单壁(Single-walled,SW)CNT薄膜卷曲成的宏观纤维的热导率和热扩散率,讨论了卷曲层数对结果的影响及估算薄膜面向热导率和热扩散率的思路。所研究的两个SWCNT薄膜的面向热导率为3.4 W/(m·K)和2.0 W/(m·K),热扩散率为24 mm~2/s和21mm~2/s。结果表明SWCNT薄膜将为发展低成本有机热电材料领域做出贡献。 相似文献
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在周期加热下薄膜二维导热分析的基础上,探讨了复合股非稳态导热的数值分析方法,并计算了使用周期热流法测量复合膜面向热扩散车时试样上温度波相位和幅值的分布.指出复合膜各膜层导热性质相差很大时,膜材料面向导热与基于一线导热分析的结果是不同的,为复合膜的测量提供了理论基础. 相似文献
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如何灵活地控制和操纵热流是目前研究的热点.本文根据变换热力学方法,导出了具有任意横截面形状热集中器的材料参数表达式,并在此基础上设计了具有圆形、椭圆形、正五边形等规则横截面形状的热集中器和具有共形、非共形任意横截面形状的热集中器.全波仿真结果表明,这些热集中器使等温线和热通量向其压缩区弯曲,靠近热源的一侧热扩散加快而相反的一侧热扩散减慢,在很小的区域内表现出对热量的集中作用,这一特点在热能工程中有潜在应用.此外,研究了圆柱形热集中器的层化实现方法.结果显示,热集中器可通过将同性材料沿角向分层交替填充来实现.这项工作对热集中器的设计及制备具有指导意义. 相似文献
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S.D. George P. Radhakrishnan V.P.N. Nampoori C.P.G. Vallabhan 《Applied physics. B, Lasers and optics》2003,77(6-7):633-637
Laser induced transverse photothermal deflection technique has been employed to determine the thermal parameters of InP doped with Sn, S and Fe as well as intrinsic InP. The thermal diffusivity values of these various samples are evaluated from the slope of the curve plotted between the phase of photothermal deflection signal and pump-probe offset. Analysis of the data shows that heat transport and hence the thermal diffusivity value, is greatly affected by the introduction of dopant. It is also seen that the direction of heat flow with respect to the plane of cleavage of semiconductor wafers influences the thermal diffusivity value. The results are explained in terms of dominating phonon assisted heat transfer mechanism in semiconductors . PACS 78.20.Nv; 66.30.Xj; 61.72.Vv 相似文献
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在充满二元混合气体的声波谐振管中,振荡的气体会在径向上建立振荡的温度梯度,径向的温度梯度会引起两种组分的分子沿着不同方向进行扩散,在这种热扩散效应和热声效应的共同作用下,声波能够把混合气体中的两种组分分别带向谐振腔的速度节点和压力节点,使得混合气体在声波传播方向上逐渐分离。为了研究热声分离过程的机理,本文对一个半波长的声波谐振管进行了二维的建模,并基于可压缩的SIMPLE算法,通过求解He-Ar混合气体的速度场、温度场和一种组分的浓度场,对谐振腔内的传热传质过程进行了详细的数值模拟研究。数值模拟结果与文献的理论计算值进行了比较,结果符合良好。随后,通过研究一个周期内径向上的温度、速度和Ar的摩尔分数分布,揭示了径向上的热扩散过程,以及中间气体与边界层内气体之间的热质交换过程,完整地解释了热声分离过程的发生机理。 相似文献
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�Ա��������Ƿ����ߴ�������ƽ�������岨��������������� 《核聚变与等离子体物理》2013,33(3):283-288
Thermal diffusivity of reduced activation ferritic/martensitic (RAFM) steel CLF-1 has been determined by the modified photoacoustic piezoelectric (PAPE) technique. Firstly, the modified PAPE theoretical model is introduced and the experimental condition with high measurement precision are identified; Secondly, the experimental system is set up and calibrated by investigating the thermal diffusivity of nickel; Finally, the thermal diffusivity of RAFM steel CLF-1 is measured by the modified PAPE method. The results show that the RAFM steel CLF-1 has good thermal diffusion properties and is a fusion reactor structural material with excellent heat conductivity. The modified PAPE technique can determine the thermal diffusivity of RAFM steel CLF-1effectively, and provides an effective way to investigate the thermal-physical property of fusion reactor structural material. 相似文献
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Santhi Ani Joseph Misha Hari Gaurav Sharma V.M. Hadiya V.P.N. Nampoori 《Optics Communications》2010,283(2):313-581
Dual beam mode-matched thermal lens method has been employed to measure the heat diffusion in nanofluid of silver with various volumes of rhodamine 6G, both dispersed in water. The important observation is an indication of temperature dependent diffusivity and that the overall heat diffusion is slower in the chemically prepared Ag sol compared to that of water. The experimental results can be explained assuming that Brownian motion is the main mechanism of heat transfer under the present experimental conditions. Light induced aggregation of the nanoparticles can also result in an anomalous diffusion behavior. 相似文献
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César San Martin Carlos Torres Daniela Esparza Daniela Bonilla 《Infrared Physics & Technology》2012,55(6):469-474
This work presents a method for measuring the thermal diffusivity of spherical samples using active infrared thermography. The principal novelty of this method lies in the deduction of an analytical model to obtain the spatial and temporal distribution of temperature in spherical samples. The model is obtained from the classical theory of heat conduction or the 3D heat diffusion equation. In order to analyze the behavior of the model, an active infrared thermography is used in order to monitor the spatial and temporal temperature distribution. Three different materials are used as spherical samples and they are heated by radiation increasing this way its temperature. The recorded data is fitted to the model by adjusting the diffusivity parameter. The results of the diffusivity values obtained using this model are consistent with those obtained from a standard thermal properties analyzer. 相似文献
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In the present work, conjugate heat transfer in a rectangular cavity with a heated moving lid is investigated using the lattice Boltzmann method (LBM). The simulations are performed for incompressible flow, with Reynolds numbers ranging from 100 to 500, thermal diffusivity ratios ranging from 1 to 100, and Prandtl numbers ranging from 0.7 to 7. A uniform heat flux through the top of the lid is assumed. Results show that LBM is suitable for the study of heat transfer in conjugate problems. Effects of the Reynolds number, the Prandtl number and the thermal diffusivity ratio on hydrodynamic and thermal characteristics are investigated and discussed. The streamlines and temperature distribution in flow field, dimensionless temperature and Nusselt number along the hot wall are illustrated. The results indicate that increase of thermal diffusivity yields the removal of a higher quantity of energy from lid and its temperature decreases when increasing the Reynolds and the Prandtl numbers. 相似文献
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Liujun Xu Chaoran Jiang Jiping Huang 《The European Physical Journal B - Condensed Matter and Complex Systems》2018,91(7):166
All objects in nature are essentially heat sources due to their non-zero temperatures, but the control of them are seldom explored in the theory of transformation thermotics, which largely results from the complicated and uncontrollable parameters given by this theory. Here we put forward an equivalence operation to overcome this challenge, and then show analytical, simulation and experimental evidence for boundary-independent conduction and all-directional replication. The former represents the counterintuitive boundary-independent behavior of thermal conduction surrounded by arbitrary boundaries; the latter denotes a thermal copy of arbitrary shaped objects, which has the accurate shape of isotherms of the objects along all directions. The equivalence operation could be an applicable method for achieving uniform heating, boundary-independent cloaking, all-directional camouflaging, etc. Our results could also give hints for both freely controlling heat transfer and delicately designing similar conduction and replication in other disciplines like electrostatics and particle diffusion. 相似文献
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采用分子动力学方法模拟了固态氩的纳米变截面结构的导热性质,研究发现纳米变截面材料的热阻和热流的大小与方向都相关:当纳米结构沿热流的方向为渐缩时,纳米结构的热阻随热流的增加而增大,而当纳米结构沿热流的方向为渐扩时,纳米结构的热阻随热流的增加呈减小的趋势;当热流较大时,热流沿渐缩方向时的热阻明显大于热流沿渐扩方向时的热阻,但当热流较小时纳米变截面结构的热阻和热流方向的关系不大.最后依据热质的运动和传递理论的动能效应对该现象进行了分析解释. 相似文献