The Impact of Tube Arrangement in Latent Heat Thermal Energy Storage on the Melting Rate of Phase Change Material

This paper analyses the impact of tube arrangement in a latent heat thermal energy storage (LHTES) system on the melting rate of phase change material (PCM). Numerical model was created in ANSYS Fluent 2023 R2, considering natural convection, to investigate the PCM melting process in LHTES. To validate the numerical model, a simulation of the PCM melting process around a single tube was conducted, and the obtained results were compared with experimental findings from other researchers. The validation showed good agreement, confirming the model's accuracy. Next, the melting process of PCM in a latent heat thermal energy storage system constructed of 9 tubes arranged inline was examined. The effect of the distance between the axes of the heating tubes and the distance from the axis of the tubes in the lower row to the bottom edge of the LHTES was investigated to understand the impact of these parameters on the melting dynamics of the PCM. The study showed that lowering the tubes in the LHTES improves natural convection in the PCM, thereby accelerating the melting process, especially in the final stage. For the exchanger with lowered tubes, charging times were reduced by up to 53.7%, and the heat flux was more than twice as high compared to the classic inline tube arrangement. Within the tested range of tube distances, increasing the spacing between the tubes in the inline arrangement decreases the average heat flux, whereas for the lowered tube arrangements, increasing the distance between the tubes does not affect the average heat flux. The conclusions drawn from this research can be used to optimize LHTES designs, contributing to the enhanced performance of thermal energy storage systems. These findings are particularly relevant for applications in renewable energy systems, where efficient thermal management is crucial for overall system performance.