Heat diffusion in nanoparticle systems via near-field thermal photons

Abstract

Near-field radiative heat transfer (NFRHT) in system of nanoparticles is significantly different from that in the far field regime due to the photon tunneling effect and the complex many body interactions, which is not well understood yet till now. The existing particle-scale NFRHT theory cannot be applied to systems of large number of particles directly, due to the enormous computational efforts. To fill the gap, we derived a continuum-scale normal-diffusion type governing equation starting from the particle-scale fluctuational electrodynamics formulation. The radiative thermal conductivity tensor is rigorously derived as a coefficient of the diffusion term. An additional convection-like term appears naturally in the governing equation for system with asymmetric distribution of particles, indicating a violation of the Fourier's law. The derived new formula of radiative thermal conductivity tensor is demonstrated to be useful and powerful in calculating the radiative thermal conductivity in arbitrary multi-dimensional particulate systems with many-body interactions.