Proximity effects in radiative heat transfer

Though the dependence of near-field radiative transfer on the gap between two planar objects is well understood, that between curved objects is still unclear. We show unequivocally that the surface polariton mediated radiative transfer between two spheres of equal radii R and minimum gap d scales as R/d as the nondimensional gap d/R -> 0. We discuss the proximity approximation form that is being used at present to compare with experimental observations and suggest a modified form in order to satisfy the continuity requirement between far-field and near-field radiative transfer between the spheres.