Conductive thermal diode based on the thermal hysteresis of VO2 and nitinol

We theoretically demonstrate that the junction between a phase-change material with a phase-invariant one can efficiently function as a conductive thermal diode. Analytical expressions for the heat flux and optimal rectification factor are derived and analyzed for junctions whose operations are driven by the thermal conductivity hysteresis of both VO2 and nitinol. It is shown that phase-change materials with higher thermal conductivity contrast, smaller thermal hysteresis, and faster phase transitions yield a conductive thermal diode with higher rectification of heat currents. Rectification factors of up to 19.7% and 18.8% are found for thermal diodes based on VO2 and nitinol, operating with a temperature difference between their terminals of 369.5 − 300 = 69.5 K and 388.2 − 273 = 115.2 K, respectively. These similar rectification factors could be enhanced by increasing the thermal conductivity variations of the diode terminals, and hence, the results obtained will be useful for guiding the development of phase-change materials capable of optimizing the rectification of conductive heat fluxes.