Many-body heat radiation and heat transfer in the presence of a nonabsorbing background medium

Abstract

Heat radiation and near-field radiative heat transfer can be strongly manipulated by adjusting geometrical shapes, optical properties, or the relative positions of the objects involved. Typically, these objects are considered as embedded in vacuum. By applying the methods of fluctuational electrodynamics, we derive general closed-form expressions for heat radiation and heat transfer in a system of N arbitrary objects embedded in a passive nonabsorbing background medium. Taking into account the principle of reciprocity, we explicitly prove the symmetry and positivity of transfer in any such system. Regarding applications, we find that the heat radiation of a sphere as well as the heat transfer between two parallel plates is strongly enhanced by the presence of a background medium. Regarding near-and far-field transfer through a gas like air, we show that a microscopic model (based on gas particles) and a macroscopic model (using a dielectric contrast) yield identical results. We also compare the radiative transfer through a medium like air and the energy transfer found from kinetic gas theory.

Heat radiation and transfer for point particles in arbitrary geometries

“…In this section, we briefly discuss the setup under study and give general expressions for HR and HT in a manybody system composed of arbitrary objects [31]. For detailed theories of HR and HT in arbitrary systems, we refer the reader to Refs.…”

“…For detailed theories of HR and HT in arbitrary systems, we refer the reader to Refs. [18,[25][26][27][28][29][30][31]. A description of the relevant EM operators can be found in Appendix A.…”

“…II, we repeat the exact expressions for heat radiation and transfer in many-body systems from Ref. [31]. These are then used in Sec.…”

“…Starting from exact expressions given in Ref. [31] and deriving an explicit form of the scattering operator of a small sphere, we obtain compact, physically insightful formulas for HR and HT. These involve only the Green's function of the surrounding objects and polarizabilities of the particles [see Eqs.…”

“…Numerical scattering techniques were applied to study HT in complex systems with analytically unknown scattering properties, e.g., in systems with periodic structures, cones, finite cylinders, or cubes [21][22][23][24]. General formalisms for HR, HT, and nonequilibrium Casimir forces in many-body systems have been recently presented and applied [18,[25][26][27][28][29][30][31][32]. HT in systems, where objects are * asheichyk@is.mpg.de small compared to all other length scales, can be relatively easily studied numerically, because all the particles can be modeled by dipole polarizabilities [33][34][35][36][37][38][39].…”