Optimization design of a composite cascaded shell-and-tube latent thermal energy storage

This study explores a novel cascaded phase change material (PCM) heat storage structure, utilizing symmetric division boards and an annular fin to create a non-uniform upper-and-lower (UAL) cascade PCM configuration combined with an equal-ratio front-and-rear (FAR) cascade PCM layout (Case 4). This design is based on a horizontal shell-and-tube latent thermal energy storage (LTES) unit (Case 1) and aims to achieve an all-around thermodynamic performance enhancement. The results are compared with those from single ‘annular fin + FAR cascade PCM’ LTES units (Case 2), ‘division boards + UAL cascade PCM’ LTES units (Case 3), and Case 1. The findings demonstrate that Case 4 successfully integrates the technical advantages of Case 2 and Case 3, addressing their respective limitations and achieving a more comprehensive thermodynamic performance improvement. Compared with Cases 1, 2, and 3, Case 4 achieves the optimum melting and temperature field uniformity in the annulus, shortening the complete melting time and increasing the heat storage rate. Besides, Case 4 has advantages in exergy performance. This research fills gaps in the combined application of FAR and UAL cascade PCM technologies, offering a novel design approach for LTES units with significant practical application potential.