Thermal Rectification Under Transient Conditions: The Role of Thermal Capacitance and Thermal Conductivity

Abstract

A thermal rectifier transmits heat asymmetrically, transmitting heat in one direction and acting as an insulator in the opposite direction. For conduction at steady-state, thermal rectification can occur naturally in systems where the thermal conductivity of the material(s) varies in space and with temperature. However, in practical applications, rectification may often need to be controlled or understood under transient conditions. Using a bulk composite, specifically a two-slab composite, as a model system, we analyze transient rectifying behavior. We find that under some conditions transient rectification can be several times larger than steady-state rectification. Further, both the thermal diffusivity of the system and the temperature-dependent thermal conductivity or thermal capacitance play an important role in affecting the transient rectifying behavior of the system, with the nonlinearity of the system leading to unusual behavior where rectification is maximized.