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Paraffin as a phase change material (PCM) has a great potential to be applied in many energy-related applications due to its appropriate melting temperature and large latent heat. The heat transfer characteristics during phase change of paraffin play a very key role in determining the thermo-fluidic performance. However, the drawback of low thermal conductivity will hamper the broaden application. In this study, we use copper foam to enhance the thermal conductivity of paraffin, and an experimental setup is built to study the phase change heat transfer characteristics. A two-temperature energy equation is used to describe the heat transfer characteristics of the paraffin/copper foam composite. The evolvement of solid-liquid interface and temperature variation during the melting process are experimentally measured and compared with the numerical results. It is found that there is a quite large temperature difference between the paraffin and ligament of copper foam, which is due to the thermal non-equilibrium effect in heat transfer between two phases. The good agreement between the experimental and numerical results indicates that heat transfer characteristics can be well depicted by two-temperature energy equation, which can be further used to depict the heat transfer in thermal energy storage or temperature control using composite PCM. [ABSTRACT FROM AUTHOR]

• A high-performance solid-liquid phase change thermal diode is presented. • Thermal rectification ratio of around 3.0 has been achieved. • Theoretical and experimental results find a great agreement. 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. [ABSTRACT FROM AUTHOR]