Thermal rectification in bulk materials with asymmetric shape

Abstract

We investigate thermal rectification in a bulk material with a pyramid shape to elucidate shape dependence of the thermal rectification, and find that rectifying coefficient R is 1.35 for this shape, which is smaller than R = 1.43 for a rectangular shape. This result is fully duplicated by our numerical calculation based on Fourier's law. We also apply this calculation to a given shape, and show a possible way to increase R depending on the shape.

From Thermal Rectifiers to Thermoelectric Devices

“…3.1 were systematically exploited to build rectifiers [77], using two cobalt oxides with different thermal conductivities. The vicinity of a structural phase transition could be used to enhance the tempera-ture dependence of the thermal conductivity [78] and the asymmetry of the shape has been exploited to vary the spatial dependence of κ(x, T ) [128]. The measurements show a good quantitative agreement with the results of Sec.…”

Inhomogeneous thermal conductivity enhances thermoelectric cooling

“…For example, the inhomogeneous nanotube, 22 thin diamond film in which the inhomogeneity is due to spatially varying disorder associated with nucleation and grain coalescence, 29 and thermal rectifier with pyramid shaped LaCoO 3 /La 0.7 Sr 0.3 CoO 3 . 30 We expect that our investigation will inspire many follow-up works in realizing inhomogeneous thermal conductivity and wide-spread applications of thermal rectifiers.…”

Heat transport by phonons and the generation of heat by fast phonon processes in ferroelastic materials

“…Passive thermal rectification has been also demonstrated in bulk materials made of two oxides with different thermal conductivities, 14 but κ high /κ low = 1.46 as an optimum case. 15 Li et al 18 have argued that as the thermal conductivity is proportional to the mean free path of phonons as κ = ΛCv/3 (Λ is the mean free path, C is the heat capacity, v is the acoustic velocity). The mean free path is determined by two different phonon scattering events, namely (a) phonon-phonon collision and (b) interactions of phonons and twin boundaries(TBs).…”

“…[13][14][15][16][17] So far, the rectification coefficients κ high /κ low are too small for applications. Inhomogeneously mass-loaded carbon and boron nitride nanotubes 13 display values of κ high /κ low ∼ 1 (1.02 for carbon nanotubes, 1.07 for boron nitride nanotubes), whereas few-layer ).…”