Charging load-dependent geometric optimization of a shell-and-tube LHTES unit: A numerical study on the effects of aspect ratio and tilt angle

This study presents a geometric optimization of shell-and-tube latent heat thermal energy storage systems to address the challenges of low thermal conductivity and non-uniform melting of phase change materials. To better represent practical operation, the optimization is conducted under both full and partial thermal load conditions, explicitly accounting for the interactions among multiple geometric parameters. A coupled computational fluid dynamics (CFD) and response surface methodology (RSM) framework is employed to quantify the effects of key geometric variables, including the aspect ratios and inclination angles of the inner tube and outer shell, on melting dynamics and heat transfer performance. The results indicate that the relative influence of these parameters varies significantly with the thermal storage load. Under partial-load conditions, system performance is primarily governed by the aspect ratios of the inner and outer tubes, while under full-load conditions, the inclination angle of the outer shell becomes the dominant factor. Geometry optimization based on these insights yielded designs that reduced charging time by 35.6 %, 30.5 %, and 58.4 % at 50 %, 75 %, and 100 % load levels, respectively. Overall, the study elucidates the coupled relationship between geometric configuration and thermal behavior and provides guidance for the development of efficient and adaptive latent heat storage systems.