Numerical and experimental study of the thermal rectification of a solid-liquid phase change thermal diode

Abstract Phase change materials (PCMs) are highly effective to enhance the sustainability of thermal energy storage, management and control systems. The quest to find other novel applications of PCMs diverts attention towards phase change thermal diodes. However particularly, solid-liquid phase change thermal diodes (SL-PCTDs) suffer from fairly low thermal rectification ratio, hampering their implementation as thermal management and temperature control units. Herein, a SL-PCTD prototype is reported that is capable to access thermal rectification ratio of 3.0, being the highest in the family of SL-PCTDs. With the help of a theoretical model, the design was optimized in terms of bi-terminal length, providing the guideline to physically fabricate and experimentally execute the SL-PCTD. Paraffin wax and calcium chloride hexahydrate have been employed to assemble phase change bi-terminals. In operation, the heat flux was manipulated within a wide temperature bias of 10–40 °C, in both the forward and reverse directions. Also, theoretical model includes the natural convection and liquid-height-dependent effective thermal conductivity of calcium chloride hexahydrate, helping to meet the prerequisites of a high-performance design.