Heat transfer performance of thermal energy storage components containing composite phase change materials

This study concerns about the heat transfer behaviour of composite phase change materials (CPCMs) based thermal energy storage components. Two types of components, a single tube and a concentric tube component, are designed and investigated. The CPCMs consist of a molten salt based phase change material, a thermal conductivity enhancement material (TCEM) and a ceramic skeleton material. A mathematical model was established to model the heat transfer behaviour. The modelling results were first compared with experiments and reasonably good agreement with the experimental data was obtained, demonstrating the reliability of the model. Extensive modelling studies were then carried out under different conditions. The influence of thermoproperties, surface roughness and size of the CPCMs as well as heat transfer fluid (HTF) velocity were examined. The results show that the thermal contact resistance between the CPCMs should be considered. Increasing the mass fraction of TCEMs and thickness of CPCMs as well as the HTF velocity intensifies the heat transfer behaviour of component. The concentric tube based component offers a better heat transfer performance compared with the single tube based component, with the total heat storage and release time similar to 10 and 15% shorter, respectively, for a given set of conditions.