Experimental investigation of melting and solidification characteristics in a vertical shell and tube latent heat thermal energy storage system with novel directional flow annular fins

In this study the impact of novel directional flow annular fins on the charging and discharging process in a vertical shell and tube latent heat thermal energy storage system (LHTES) with phase change materials (PCM) is examined. Consequently, the tube carrying heat transfer fluid (HTF) is surrounded by five annular fins. To examine the impact of directional flow fins on the thermal performance of LHTES, four novel directional flow fin configurations namely, 1 mm thick solid circular fin, 10 mm thick hollow circular fin - flow of HTF only through the central tube, 10 mm thick hollow circular fin - flow of HTF partially through the central tube and partially through the fin structure, 10 mm hollow circular fin - flow of HTF only through the fin structure were selected. In order to study the LTHES experimentally, three sections are chosen for the location of thermocouples at 0, 120 and 240°. At each sections five thermocouples are located to record the temperature distribution in the PCM. A detailed behavior of melting and solidification cycles are explained by observing temperature variation, accumulative energy and melting fraction during both melting and solidification. Results show that use of directional flow fins decreases melting time by 58.33 % in comparison with conventional fins and solidification time by 50 % of LHTES and allows heat to penetrate deeper through the volume of the PCM more uniformly. Additionally, the thermal efficiency of the LHTES system was found to be 67.4 % during charging and 53.85 % during discharging, validating the significant improvement in energy storage and retrieval performance with directional flow fins in latent heat thermal energy storage system.