Thermal diodes, regulators, and switches: Physical mechanisms and potential applications

Abstract

Interest in new thermal diodes, regulators, and switches has been rapidly growing because these components have the potential for rich transport phenomena that cannot be achieved using traditional thermal resistors and capacitors. Each of these thermal components has a signature functionality: Thermal diodes can rectify heat currents, thermal regulators can maintain a desired temperature, and thermal switches can actively control the heat transfer. Here, we review the fundamental physical mechanisms of switchable and nonlinear heat transfer which have been harnessed to make thermal diodes, switches, and regulators. The review focuses on experimental demonstrations, mainly near room temperature, and spans the fields of heat conduction, convection, and radiation. We emphasize the changes in thermal properties across phase transitions and thermal switching using electric and magnetic fields. After surveying fundamental mechanisms, we present various nonlinear and active thermal circuits that are based on analogies with well-known electrical circuits, and analyze potential applications in solid-state refrigeration and waste heat scavenging.

Nonlinear Heat Radiation Induces Thermal Rectifier in Asymmetric Holey Composites

“…Thus, there have been more theoretical studies of thermal rectification focusing on nonlinear systems (Wehmeyer et al, 2017). Nonlinearity can be provided in different ways to design a thermal rectifier, including one-dimensional nonlinear lattice (Terraneo et al, 2002;Li et al, 2004;Hu and Yang, 2005), nonlinear electron gas dispersion in conductors (Segal, 2008), nonlinear Schrödinger equation , nonlinear near-field radiation (Otey et al, 2010;Basu and Francoeur, 2011), and even a vapor generation rectifier (Ding et al, 2017).…”

Energy Applications of Magnetocaloric Materials

“…The last decade has witnessed a large amount of research in the field of thermal sciences, and this has resulted in the opening and revisiting of some thermal elements. The thermal elements are used to control the heat flux or thermal resistance on different size and time scales and are of four main types, namely, thermal switches, thermal diodes, thermal regulators, and thermal resistors. Conscientious research has led to new findings and substantially improved knowledge of the thermal sciences and transport phenomena, including on the macro‐, micro‐, and nano‐scale.…”

The Heat Conduction Renaissance

“…The ability to actively regulate heat flow at the nanoscale could have dramatic implications for thermal management of electronics [71]. Research in this area has seen a surge over the past ten years, concurrent with improvements in nano-thermal metrology techniques including in situ characterization capabilities.…”