Heat transfer behaviour of thermal energy storage components using composite phase change materials

The work reported in this paper concerns the heat transfer behaviour of thermal energy storage components using composite phase change materials. Components with a single and a concentric configuration are designed and investigated. The composite materials consist of a molten salt based phase change material (PCM), a thermal conductivity enhancer material (TCEM) and a ceramic skeleton material (CSM). A mathematical model is established for the transient heat transfer in the composite materials and the components. The model is first compared with experimental data, showing a reasonably good agreement, and indicating the validity of the numerical model. Extensive modelling is then carried out to study the heat transfer behaviour under different conditions, particularly the influences of materials properties and geometrical design of the composite material module as well as heat transfer fluid velocity. The results show that an increase in the mass fraction of the TCEM, the thickness of the composite material module, or the velocity of the heat transfer fluid enhances the heat storage and release rate and improves the heat transfer performance of thermal energy storage components. The concentric tube configuration offers a better performance than the single tube configuration.