近场和远场下金属纳米颗粒团簇间的辐射换热
Radiative heat transfer between metallic nanoparticle clusters in both near field and far field
摘要：
微-纳米体系在热科学与技术中有着广泛的应用。在稠密颗粒系统中，颗粒间距可能小于特征热波长，近场效应将显著，成为影响系统热辐射传递的关键因素。在这项研究中，两个金属纳米粒子团簇之间的辐射传热（RHT）进行了探索，使用多体辐射传热理论实现的耦合电和磁偶极子（CEMD）的方法，有效地考虑到金属纳米粒子的磁极化对热交换的贡献。重点分析了磁极化和多体相互作用对RHT的影响。分析了团簇的分形维数和相对取向对团簇结构的影响。结果表明，磁极化涡流焦耳耗散的贡献占主导地位的银纳米粒子团簇之间的RHT。如果只考虑电极化的强度（EP方法），与CEMD方法相比，在近场和远场区域的热导率将被低估。在室温下，MBI对Ag纳米颗粒团簇之间的RHT的影响不明显，这与SiC纳米颗粒团簇有很大不同。对于后者，MBI倾向于显著抑制RHT。对于具有花边结构的团簇，当团簇间距在近场时，相对取向对团簇的辐射热流有显著影响。而在远场，相对方位和分维对辐射热流的影响都很小。这一工作将有助于对稠密颗粒体系热输运的理解。
英文摘要：
Micro-nanoparticle systems have wide applications in thermal science and technology. In dense particulate system, the particle separation distance may be less than the characteristic thermal wavelength and near field effect will be significant and become a key factor to influence thermal radiation transfer in the system. In this study, radiative heat transfer (RHT) between two metallic nanoparticles clusters are explored using many-body radiative heat transfer theory implemented with the coupled electric and magnetic dipole (CEMD) approach, which effectively takes into account the contribution of magnetic polarization of metallic nanoparticles on heat exchange. As the focus, the effects of magnetic polarization and many-body interaction (MBI) on RHT were analyzed. The effects of fractal dimension and relative orientation of the clusters were also analyzed. Results show that the contribution of magnetically polarized eddy-current Joule dissipation dominates the RHT between Ag nanoparticle clusters. If only electric polarization (EP approach) is considered, the heat conductance will be underestimated as compared with the CEMD approach in both near field and far field regime. The effect of MBI on the RHT between Ag nanoparticle clusters is unobvious at room temperature, which is quite different from the SiC nanoparticle clusters. For the latter, MBI tends to suppress RHT significantly. The relative orientation has remarkable effect on radiative heat flux for clusters with lacy structure when the separation distance is in the near field. While for the separation distance in far field, both the relative orientation and the fractal dimension has a weak influence on radiative heat flux. This work will help the understanding of thermal transport in dense particulate system.
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