Thermal near-field radiative transfer between two spheres

Arvind Narayanaswamy and Gang Chen
Phys. Rev. B 77, 075125 – Published 25 February 2008

Abstract

Radiative energy transfer between closely spaced bodies is known to be significantly larger than that predicted by classical radiative transfer because of tunneling due to evanescent waves. Theoretical analysis of near-field radiative transfer is mainly restricted to radiative transfer between two half-spaces or spheres treated in the dipole approximation (very small sphere) or proximity force approximation (radius of sphere much greater than the gap). Sphere-sphere or sphere-plane configurations beyond the dipole approximation or proximity force approximation have not been attempted. In this work, the radiative energy transfer between two adjacent non-overlapping spheres of arbitrary diameters and gaps is analyzed numerically. For spheres of small diameter (compared to the wavelength), the results coincide with the dipole approximation. We see that the proximity force approximation is not valid for spheres with diameters much larger than the gap, even though this approximation is well established for calculating forces. From the numerical results, a regime map is constructed based on two nondimensional length scales for the validity of different approximations.

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  • Received 3 August 2007

DOI:https://doi.org/10.1103/PhysRevB.77.075125

©2008 American Physical Society

Authors & Affiliations

Arvind Narayanaswamy*

  • Department of Mechanical Engineering, Columbia University, New York, New York 10027, USA

Gang Chen

  • Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA

  • *arvindn@alum.mit.edu
  • gchen2@mit.edu

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Vol. 77, Iss. 7 — 15 February 2008

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