Near-field radiative transfer between two spheres can be computed using Rytov’s theory of fluctuational electrodynamics in which the strength of electromagnetic sources is related to temperature through the fluctuation-dissipation theorem, and the resultant energy transfer is described using an expansion of the dyadic Green’s function of the vector Helmholtz equation in a series of vector spherical waves. We show that when electromagnetic surface waves are active at a frequency the number of vector spherical waves required for convergence is proportional to Rmax/d when d/Rmax → 0, where Rmax is the radius of the larger sphere, and d is the smallest gap between the two spheres. Using this criterion, we show that the surface polariton mediated near–field thermal radiative conductance between two spheres of equal radii R scales as R/d as d/R → 0. We also propose a modified form of the proximity approximation to predict near–field radiative transfer between curved objects from simulations of radiative transfer between parallel surfaces.
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Effect of Curvature on Near-Field Radiative Transfer: The Modified Proximity Approximation
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Sasihithlu, K, & Narayanaswamy, A. "Effect of Curvature on Near-Field Radiative Transfer: The Modified Proximity Approximation." Proceedings of the ASME 2012 Third International Conference on Micro/Nanoscale Heat and Mass Transfer. ASME 2012 Third International Conference on Micro/Nanoscale Heat and Mass Transfer. Atlanta, Georgia, USA. March 3–6, 2012. pp. 491-501. ASME. https://doi.org/10.1115/MNHMT2012-75163
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