Theory for Enhanced Thermal Concentrators: Thermal Conductivity Coupling

Abstract

In this chapter, we propose the theory of conductivity coupling to solve the problem that the concentrating efficiency of a thermal concentrator is restricted by its geometric configuration. We first discuss a monolayer scheme with an isotropic thermal conductivity, which can break the upper limit but is still restricted by the geometric structure. We further explore another degree of freedom by considering the monolayer scheme with an anisotropic thermal conductivity or adding the second shell with an isotropic thermal conductivity, thereby freeing the concentrating efficiency from the geometric configuration. Finite-element simulations are performed to confirm the theoretical predictions, and experimental suggestions are also provided to improve feasibility. These results may have potential applications for thermal camouflage and provide insights into other diffusive systems such as static magnetic fields and DC fields for achieving similar behaviors.