Thermal diodes are materials that allow for the preferential directional transport of heat and are highly promising devices for energy conservation, energy harvesting, and information processing applications. One form of a thermal diode consists of the junction between a phase change and phase invariant material, with rectification ratios that scale with the square root of the ratio of thermal conductivities of the two phases. In this work, the authors introduce and analyse the concept of a Dual Phase Change Thermal Diode (DPCTD) as the junction of two phase change materials with similar phase boundary temperatures but opposite temperature coefficients of thermal conductivity. Such systems possess a significantly enhanced optimal scaling of the rectification ratio as the square root of the product of the thermal conductivity ratios. Furthermore, the authors experimentally design and fabricate an ambient DPCTD enabled by the junction of an octadecane-impregnated polystyrene foam, polymerized using a high internal phase emulsion template (PFH-O) and a poly(N-isopropylacrylamide) (PNIPAM) aqueous solution. The DPCTD shows a significantly enhanced thermal rectification ratio both experimentally (2.6) and theoretically (2.6) as compared with ideal thermal diodes composed only of the constituent materials.
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledged KAUST grant number(s): OSR-2015-Sensors-2700
Acknowledgements: A.L.C. and S.W. contributed equally to this work. The authors acknowledge the Office of Naval Research (ONR), under award N00014-16-1-2144, and King Abdullah University of Science and Technology (KAUST), under award OSR-2015-Sensors-2700, for their financial support regarding this project. The authors are also thankful for the support of Lin Guangzhao and Hu Guozan Graduate Education International Exchange Fund from Zhejiang University and the National Nature Science Foundation of China (grants 21376211 and 21420102008).
This publication acknowledges KAUST support, but has no KAUST affiliated authors.