SUMMARY
In this paper, we have studied numerically thermo-convective characteristics between a heat transfer fluid (HTF) and phase change material (PCM) in shell and tube thermal energy storage (TES) unit. The paraffin wax is considered as a PCM, filled in a shell which is thermally isolated with the external environment, while the water plays a role of a HTF and flows inside the tube at the moment of charging and discharging cycle. The heat transfer between HTF and PCM is performed by conduction and forced convection, this transfer allows to change the physical state of PCM solid-liquid to obtain a quantity of storable heat in order to create a thermal battery. Enthalpy formulation is used to analyze the heat transfer during melting and solidification process. A good agreement was found between our numerical predictions and the results of the literature. On the other hand, we have investigated the effect of geometrical parameters (tube length and shell diameter) and Reynolds number on the charging and discharging cycles. The obtained results reveal that the tube length and the shell diameter are the most influential parameters on the time of storage system. Similarly, the Reynolds number has much impact on the HTF outlet temperature and the time of solidification and melting process. Furthermore, we have proposed a new thermal storage unit containing the Paraffin wax and RT60 that it gives us a good rate and time of storage compared to the first unit that has only the paraffin wax.