Thermal performance of a high temperature flat plate thermal energy storage unit with multiple phase change materials

In this study, a numerical investigation was conducted on the performance of a high temperature flat plate thermal energy storage with three phase change materials (PCMs). Based on a one-dimensional model, both the thermal conduction and phase change within the PCMs plate in the direction normal to the flow direction of heat transfer fluid (HTF) are taken into consideration in this study. The model was utilized to examine the influence of the cut-off values, mass flow rate of the HTF, and the flat plate thickness on the thermal storage efficiency and the melting process of the PCMs. The results indicated that both the thermal storage efficiency and the charging time increased with an increase in the cut-off values. Enhancing the mass flow rate of the HTF or reducing the thickness of the plate was found to be beneficial in improving the charging speed of the PCMs. Furthermore, at a cut-off value of 0.5, reducing the mass flow rate of the HTF or the flat plate thickness could improve the thermal storage efficiency, although the impact was not significant. •The thermal performance of a high temperature flat plate thermal energy storage unit with multi-PCMs was simulated.•The heat accumulator is composed of shape-stable phase change material and has no encapsulation structure.•Practical storage capacity depends on the threshold temperature to stop the operation.