Determination of thermal conductivity and emissivity of electromagnetically levitated high-temperature droplet based on the periodic laser-heating method: Theory
Determination of thermal conductivity and emissivity of electromagnetically levitated high-temperature droplet based on the periodic laser-heating method: Theory
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DOI：
10.1016/j.ijheatmasstransfer.2006.12.026
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发表时间：
2007-07
影响因子：
5.2
通讯作者：
T. Tsukada;H. Fukuyama;H. Kobatake
中科院分区：
文献类型：
--
作者：
T. Tsukada;H. Fukuyama;H. Kobatake
近年来，利用电磁悬浮技术测量高温熔融材料的热物理性质，特别是导热系数的新方法已经由[H. Fukuyama，H.小武岛美娜多，K.高桥T. Tsukada，S. Awaji，使用固体铂球作为参考建立高温熔体的非接触AC量热法，在：第16届热物理性质研讨会论文集，CD-ROM，2006，p.937; H. Kobatake，H.福山岛美娜多，T. Tsukada，S. Awaji，Noncontact AC calorimetry of liquid silicon with suppressing convections in a static magnetic field，in：Proceedings of 16 th Symposium on Thermophysical Properties，CD-ROM，2006，p.625]，其中该方法基于周期性激光加热，并且叠加静态磁场以抑制电磁悬浮液滴中的对流。在本工作中，对周期性激光加热方法进行建模，以使用测量的参数（即，在调制光的不同频率ω下，调制光与高温计检测到的温度变化之间的相位滞后Δ Δ s。在此基础上，对液滴向环境辐射传热的非稳态热传导方程进行了简化，并转化为稳态线性方程组。用本文提出的数学模型拟合了Δ ε与ω之间的实验关系，可同时估算熔融硅的热导率和发射率。通过对电磁悬浮液滴在周期性激光加热下的非稳态热场进行数值模拟，验证了所提简化模型的有效性，并研究了热物性参数对Δ ε和ω之间关系的敏感性.
Recently, a novel method of measuring the thermophysical properties, especially thermal conductivity, of high-temperature molten materials using the electromagnetic levitation technique has been developed by [H. Fukuyama, H. Kobatake, I. Minato, K. Takahashi, T. Tsukada, S. Awaji, Establishment of noncontact AC calorimetry of high-temperature melts using solid platinum spheres as a reference, in: Proceedings of 16th Symposium on Thermophysical Properties, CD-ROM, 2006, p. 937; H. Kobatake, H. Fukuyama, I. Minato, T. Tsukada, S. Awaji, Noncontact AC calorimetry of liquid silicon with suppressing convections in a static magnetic field, in: Proceedings of 16th Symposium on Thermophysical Properties, CD-ROM, 2006, p. 625], where the method was based on periodic laser-heating, and a static magnetic field was superimposed to suppress convection in an electromagnetically levitated droplet. In the present work, the periodic laser-heating method was modeled to estimate the thermal conductivity and emissivity of the electromagnetically levitated droplet using a measured parameter, i.e., the phase lag between the modulated light and the temperature variations detected by a pyrometer, Δϕs, at various frequencies of the modulated light ω. Here, the unsteady-state heat conduction equation for the droplet accompanying radiative heat transfer to the ambient was simplified and transformed to steady-state linear equations. The experimental relation between Δϕsand ω was fitted by the mathematical model proposed here to estimate simultaneously the thermal conductivity and emissivity of molten silicon. Also, the numerical simulations for unsteady thermal field in the electromagnetically levitated droplet which was periodically laser-heated were carried out to demonstrate the validity of the proposed simplified model, and then to investigate the sensitivity of the thermophysical properties to the relation between Δϕsand ω.