Optimization of the rectification factor of radiative thermal diodes based on two phase-change materials

Suraju Olawale Kasali (1, 2) , Jose Ordonez-Miranda (2) , Karl Joulain (2)

1 AE-FUNAI - Alex Ekwueme Federal University Ndufu-Alike, Ikwo
2 TNR - Thermique aux Nano échelles et Rayonnement [Institut Pprime]

We have theoretically studied and optimized the thermal rectification of plane, cylindrical and spherical radiative thermal diodes operating with terminals of two phase-change materials, whose emissivities significantly change within a narrow interval of temperatures. Analytical expressions for the optimal rectification factors of these three diodes are derived and analyzed comparatively. Optimal rectification factors of 82%, 86% and 90.5% are obtained for the plane, cylindrical and spherical diodes made up with terminals of Ge 2 Sb 2 Te 5 and VO 2 operating with a temperature difference of 450 − 300 = 150 K, respectively. The spherical geometry thus represents a suitable shape to optimize the rectification of radiative heat currents. Furthermore, it is shown that higher rectification factors can potentially be achieved by using phase-change materials with emissivities contrasts higher than those of Ge 2 Sb 2 Te 5 and VO 2. We demonstrate that radiative thermal diodes based on two phase-change materials are able to operate with rectification factors higher than the corresponding ones of diodes involving a single phase-change material. The obtained results thus shed light on the phase-change materials required for optimizing the rectification factor of radiative thermal diodes with different geometries.

Mots clés: Thermal rectification; heat flows; rectification factor; emissivities; radiative thermal diodes; phase-change materials

Domaines: Science non linéaire [physics]; Thermique [physics.class-ph]; Electronique

Suraju Olawale Kasali, Jose Ordonez-Miranda, Karl Joulain. Optimization of the rectification factor of radiative thermal diodes based on two phase-change materials. International Journal of Heat and Mass Transfer, 2020, 154, pp.119739. ⟨10.1016/j.ijheatmasstransfer.2020.119739⟩. ⟨hal-03017599⟩