壳核结构纳米颗粒消光效应与近场辐射传热数值研究
发布时间：2019-01-10 14:43
【摘要】：微尺度下辐射研究可采用数值与实验研究方法。实验研究常受限于实验设备与操作环境。数值研究物理概念清楚,理论研究比较充分,简化假设较少,能较准确的反映实际的物理过程,其结果可作为进一步实验研究的依据。因而本文主要采用数值研究的方法分析微尺度下的辐射换热问题。辐射换热属于传热领域的一个重要分支,根据不同温度物体间距离的不同,可以将辐射分成远场辐射与近场辐射。远场辐射可以通过斯蒂芬-波尔兹曼公式计算获得,结果与物体间的距离无关。而近场辐射却由于电磁波的耦合作用,随着物体间距离减小辐射换热量大大增加,并且与物体间距离呈六次方反比关系,同时可以通过改变物质结构、尺寸、材料等来改变物体间近场辐射换热的大小与换热的光谱区间。纳米颗粒群间的辐射换热属于微尺度换热范畴,在此,我们引入一种新型物质结构,即半导体内核金属外壳构成的复合结构纳米颗粒,通过改变物质的半径、体积分数、阵列间的距离来控制物质的辐射换热特性。纳米颗粒群的消光作用可以分为吸收作用和散射作用,依据颗粒尺寸和体积分数的不同,纳米颗粒间的散射可以分为独立散射与非独立散射,近场辐射为非独立散射情况下颗粒间的辐射耦合作用提供了一种解释。本文第一章介绍了本论文的研究背景以及国内外的研究现状。第二章引入辐射换热基础理论的介绍,包括Maxwell电磁理论与电介质函数模型,分析温度对介质电介质函数的影响以及不同电介质函数模型的区别,基于Maxwell原理的波动电动力学方法得到了两个平面间和两个颗粒间的辐射换热特性和光谱变化情况。第三章在第二章的基础上,得到了壳核结构纳米阵列间的近场辐射作用,包括壳核结构纳米颗粒阵列间的近场辐射和壳核结构纳米线阵列间的近场辐射,并依次计算了相应的近场辐射热传导。第四章则主要分析壳核结构颗粒群的消光效应,首先介绍颗粒辐射的散射与吸收理论,依次介绍与消光效应相关的Mie散射理论、基于射线追踪的蒙特卡洛方法、Quasi-static近似的Rayleigh散射方法,在以上理论研究的基础上,得到了不同尺度、体积分数、材料的纳米颗粒群的消光效应和辐射透射率。研究发现壳核结构的纳米线与纳米颗粒是一种很好的强化换热物质结构,相信相应的数值计算结果对微纳尺度下辐射换热的进一步研究有一定的参考意义。
[Abstract]:Numerical and experimental methods can be used to study radiation at microscale. Experimental research is often limited by experimental equipment and operating environment. The physical concept of numerical research is clear, the theoretical research is more adequate, the simplified hypothesis is less, and the actual physical process can be accurately reflected. The results can be used as the basis for further experimental research. Therefore, the numerical method is mainly used to analyze the radiation heat transfer problem in the micro scale. Radiation heat transfer is an important branch of heat transfer field. According to the distance between objects at different temperatures, radiation can be divided into far-field radiation and near-field radiation. The far-field radiation can be calculated by Steff-Boltzmann formula and the results are independent of the distance between the objects. However, the near-field radiation increases greatly with the decrease of the distance between the objects due to the coupling of electromagnetic waves, and is inversely proportional to the distance between the objects. At the same time, it can be changed by changing the structure and size of the matter. Materials, etc., to change the magnitude and spectral range of near-field radiation heat transfer between objects. The radiation heat transfer between nanoparticles belongs to the category of microscale heat transfer. In this case, we introduce a new kind of material structure, that is, the composite structure of the semiconductor core metal shell, by changing the radius and volume fraction of the matter. The distance between arrays controls the radiative heat transfer characteristics of matter. The extinction action of nanoparticles can be divided into absorption and scattering. According to the difference of particle size and volume fraction, the scattering between nanoparticles can be divided into independent scattering and non-independent scattering. Near-field radiation provides an explanation for the radiation coupling between particles in the case of non-independent scattering. The first chapter of this paper introduces the research background and domestic and foreign research status. The second chapter introduces the basic theory of radiation heat transfer, including Maxwell electromagnetic theory and dielectric function model, analyzes the influence of temperature on dielectric function and the difference between different dielectric function models. The radiative heat transfer characteristics and spectral variations between two planes and two particles are obtained by the wave electrodynamics method based on Maxwell principle. In chapter 3, based on the second chapter, we get the near field radiation between the shell core nanoarrays, including the near field radiation between the shell core structure nanoparticles array and the shell core structure nanowire array. The corresponding near field radiation heat conduction is calculated in turn. In the fourth chapter, the extinction effect of particle group in shell core structure is analyzed. Firstly, the scattering and absorption theory of particle radiation is introduced, and then the Mie scattering theory related to extinction effect is introduced, and the Monte Carlo method based on ray tracing is introduced. Based on the theoretical study above, the Quasi-static approximation Rayleigh scattering method is used to obtain the extinction effect and radiative transmittance of different scales, volume fraction, nano-particle groups of materials. It is found that the nanowires and nanoparticles of the shell core structure are a good enhancement of heat transfer material structure. It is believed that the corresponding numerical results are useful for the further study of radiation heat transfer at the micro- and nanoscale scale.
【学位授予单位】：华北电力大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB383.1
本文编号：2406432
[Abstract]:Numerical and experimental methods can be used to study radiation at microscale. Experimental research is often limited by experimental equipment and operating environment. The physical concept of numerical research is clear, the theoretical research is more adequate, the simplified hypothesis is less, and the actual physical process can be accurately reflected. The results can be used as the basis for further experimental research. Therefore, the numerical method is mainly used to analyze the radiation heat transfer problem in the micro scale. Radiation heat transfer is an important branch of heat transfer field. According to the distance between objects at different temperatures, radiation can be divided into far-field radiation and near-field radiation. The far-field radiation can be calculated by Steff-Boltzmann formula and the results are independent of the distance between the objects. However, the near-field radiation increases greatly with the decrease of the distance between the objects due to the coupling of electromagnetic waves, and is inversely proportional to the distance between the objects. At the same time, it can be changed by changing the structure and size of the matter. Materials, etc., to change the magnitude and spectral range of near-field radiation heat transfer between objects. The radiation heat transfer between nanoparticles belongs to the category of microscale heat transfer. In this case, we introduce a new kind of material structure, that is, the composite structure of the semiconductor core metal shell, by changing the radius and volume fraction of the matter. The distance between arrays controls the radiative heat transfer characteristics of matter. The extinction action of nanoparticles can be divided into absorption and scattering. According to the difference of particle size and volume fraction, the scattering between nanoparticles can be divided into independent scattering and non-independent scattering. Near-field radiation provides an explanation for the radiation coupling between particles in the case of non-independent scattering. The first chapter of this paper introduces the research background and domestic and foreign research status. The second chapter introduces the basic theory of radiation heat transfer, including Maxwell electromagnetic theory and dielectric function model, analyzes the influence of temperature on dielectric function and the difference between different dielectric function models. The radiative heat transfer characteristics and spectral variations between two planes and two particles are obtained by the wave electrodynamics method based on Maxwell principle. In chapter 3, based on the second chapter, we get the near field radiation between the shell core nanoarrays, including the near field radiation between the shell core structure nanoparticles array and the shell core structure nanowire array. The corresponding near field radiation heat conduction is calculated in turn. In the fourth chapter, the extinction effect of particle group in shell core structure is analyzed. Firstly, the scattering and absorption theory of particle radiation is introduced, and then the Mie scattering theory related to extinction effect is introduced, and the Monte Carlo method based on ray tracing is introduced. Based on the theoretical study above, the Quasi-static approximation Rayleigh scattering method is used to obtain the extinction effect and radiative transmittance of different scales, volume fraction, nano-particle groups of materials. It is found that the nanowires and nanoparticles of the shell core structure are a good enhancement of heat transfer material structure. It is believed that the corresponding numerical results are useful for the further study of radiation heat transfer at the micro- and nanoscale scale.
【学位授予单位】：华北电力大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB383.1
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