Near-field thermal electromagnetic transport: An overview

Abstract

A general near-field thermal electromagnetic transport formalism that is independent of the size, shape and number of heat sources is derived. The formalism is based on fluctuational electrodynamics, where fluctuating currents due to thermal agitation are added to Maxwell's curl equations, and is thus valid for heat sources in local thermodynamic equilibrium. Using a volume integral formulation, it is shown that the proposed formalism is a generalization of the classical electromagnetic scattering framework in which thermal emission is implicitly assumed to be negligible. The near-field thermal electromagnetic transport formalism is afterwards applied to a problem involving three spheres with size comparable to the wavelength, where all multipolar interactions are taken into account. Using the thermal discrete dipole approximation, it is shown that depending on the dielectric function, the presence of a third sphere slightly affects the spatial distribution of power absorbed compared to the two-sphere case. A transient analysis shows that despite a non-uniform spatial distribution of power absorbed, the sphere temperature remains spatially uniform at any instant due to the fact that the thermal resistance by conduction is much smaller than the resistance by radiation. The formalism proposed in this paper is general, and † Corresponding authors. Tel.: +1 801 581 5721, Fax: +1 801 585 9825 E-mail addresses: mfrancoeur@mech.utah.edu (M. Francoeur), sheila.edalatpour@utah.edu (S. Edalatpour) 2 could be used as a starting point for adapting solution methods employed in traditional electromagnetic scattering problems to near-field thermal electromagnetic transport.

Near-field radiative heat transfer between arbitrarily shaped objects and a surface

“…The formalism, based on fluctuational electrodynamics [30], is independent of the size, shape and number of objects. The volume integral equation for the electric field derived from fluctuational electrodynamics is discretized using the thermal discrete dipole approximation (T-DDA) [18,27,31]. The interactions between the objects and the surface are treated analytically using Sommerfeld's theory of electric dipole radiation above an infinite plane [32].…”

Thermal radiative energy exchange between a closely-spaced linear chain of spheres and its environment

“…The smallest subvolumes were concentrated at locations nearest to other spheres, to achieve high resolution in the volumes which absorb most heavily. Although it is not mentioned in Edalatpour et al [38], the authors have stated in other works that T-DDA computation time can be lengthy [15]. Time, of course, is the price paid for the ability to simulate any geometry.…”

“…Dipole Approximation Edalatpour et al [38] used T-DDA to simulate the NFRHT between three spheres in a chain. In the notation of this work, Edalatpour et al simulated three identical spheres with ρ = 0.8 µm and D = 100 nm.…”

“…Comparison of results from current work (DGF) and the thermal discrete dipole approximation (T-DDA) for a three sphere chain using a resonant value of dielectric function. Values from T-DDA are taken from Edalatpour et al[38].…”

Phonon-Polariton Mediated Thermal Radiation and Heat Transfer among Molecules and Macroscopic Bodies: Nonlocal Electromagnetic Response at Mesoscopic Scales

“…If z > ξ, the heat transfer begins to saturate for d 10 nm due to charge smearing. The situation becomes more complicated when both d, z ξ [70] due to the interplay of object sizes and nonlocality, with the finite and elongated one-dimensional geometry of the parallel wires also playing a significant role. In this regime, the nonlocal response of the wires begins to have an effect on their images in the conducting surface, which are themselves affected by the shapes of the molecules, leading to even more complicated behavior and illustrating the need to treat both atomistic and long-range many-body EM effects at these scales [71].…”