Radiative heat transfer in fractal structures

Systems of many nanoparticles or volume-discretized bodies exhibit collective radiative properties that could be used for enhanced, guided, or tunable thermal radiation. These are commonly treated as assemblies of point dipoles with interactions described by Maxwell's equations and thermal fluctuations correlated by the fluctuation-dissipation theorem. Here, we unify different theoretical descriptions of these systems and provide a complete derivation of many-dipole thermal radiation, showing that the correct use of the fluctuation-dissipation theorem depends on the definitions of fluctuating and induced dipole moments. We formulate a method to calculate the diffusive radiative thermal conductivity of arbitrary collections of nanoparticles; this allows the comparison of thermal radiation to other heat transfer modes and across different material systems. We calculate the radiative thermal conductivity of ordered and disordered arrays of SiC and SiO2 nanoparticles and show that thermal radiation can significantly contribute to thermal transport in these systems. We validate our calculations by comparison to the exact solution for a one-dimensional particle chain, and we demonstrate that the dipolar approximation significantly underpredicts the exact results at separation distances less than the particle radius.

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“…where is the Kronecker delta function. Inserting Equation (13) into Equation (1) gives us an expression for the local fields:…”

Section: B Expressions For Total Dipole Moments and Electric Fieldsmentioning

confidence: 99%

“…where is the temperature of the th dipole, and the angled brackets represent the ensemble average. Focusing on this correlation function and inserting Equations (13) and (15) yields…”

Section: Energy Exchange and The Fluctuation-dissipation Theoremmentioning

confidence: 99%

Thermal radiation in systems of many dipoles

et al. 2019

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“…The net exchanged RHT power between two nanoparticles clusters considering many-body interaction obtained from CEMD is calculated from 11 Ne Na ji ji P      (28) where Ne is the number of particles in emitting cluster, and Na is the number of particles in absorbing cluster. A definition of thermal conductance (G) between the two nanoparticles clusters is…”

Section: Theoretical Aspectmentioning

confidence: 99%

“…When MBI is not considered, namely, the existence of all other particles does not change the 'system Green function', hence the system Green function is just the Green function in vacuum, and the transmission coefficient between particle i and j is calculated from (30) Then by omitting the MBI, the RHT power exchanged between two particles (P 0 ji ), the net exchanged RHT power between two clusters (0), and the thermal conductance without MBI (G0) can be calculated using Eqs. (27), (28) and (29)…”

Section: Theoretical Aspectmentioning

confidence: 99%

Radiative heat transfer between metallic nanoparticle clusters in both near field and far field

et al. 2019

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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.Recently, there were some notable theoretical development to deal with NFRHT in

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“…The heat transfer between two CSNP is modeled by the interaction of simple fluctuating dipoles and the coupled electric-electric and magneticmagnetic dipole approach 36 is used to calculate the contribution of electric and magnetic dipole moments to the radiative heat flux. The associated net heat flux can be described using the many-body radiative heat transfer theory 16,[36][37][38] , from which the mutual conductance at small temperature mismatch (…”

Section: Modelmentioning

confidence: 99%

Radiative heat transfer between core-shell nanoparticles

Nikbakht

2018

Journal of Quantitative Spectroscopy and Radiative Transfer

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Radiative heat transfer in systems with core-shell nanoparticles may exhibit not only a combination of disparate physical properties of its components but also further enhanced properties that arise from the synergistic properties of the core and shell components. We study the thermal conductance between two core-shell nanoparticles (CSNPs). The contribution of electric and magnetic dipole moments to the thermal conductance depend sensitively on the core and shell materials, and adjustable by core size and shell thickness. We predict that the radiative heat transfer in a dimer of Au@SiO2 CSNPs (i.e., silica-coated gold nanoparticles) could be enhanced several order of magnitude compared to bare Au nanoparticles. However, the reduction of several orders of magnitude in the heat transfer is possible between SiO2@Au CSNPs (i.e., silica as a core and gold as a shell) than that of uncoated SiO2 nanoparticles.

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Radiative heat transfer in fractal structures

Cited by 43 publications

References 44 publications

Thermal radiation in systems of many dipoles

Thermal radiation in systems of many dipoles

Radiative heat transfer between metallic nanoparticle clusters in both near field and far field

Radiative heat transfer between core-shell nanoparticles

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