Effect of rotation control on thermal performance of phase change unit with annular fins

Thermal energy storage(TES) devices are critical for efficient energy utilization and stable supply in building-integrated solar energy systems. Previous studies on rotation-driven TES devices have overlooked the trade-off between energy consumption and heat storage performance. Numerical simulations were conducted in this study to systematically explore finned paraffin-based thermal energy storage devices. Key thermal performance parameters, including thermal charging behavior, temperature distribution, flow field characteristics, heat storage capacity, heat storage efficiency, and energy consumption, were analyzed to evaluate the impact of rotation on/off switching moments. Results indicate that rotation-driven enhancement significantly shortens the charging time of vertical finned thermal energy storage tubes, with the benefits of this enhancement most pronounced in the late melting stage. The "first fixed then rotated" strategy (activating rotation at a liquid fraction of approximately 0.6) outperforms continuous rotation: compared with continuously rotating vertical finned thermal storage tubes, this strategy increases the benefits of reduced melting time, improved melting rate, and enhanced temperature response by 40.47%, 43.52%, and 36.98% per unit energy consumption, respectively. This study fills the existing research gap in dynamic rotation control for finned PCM storage devices. It provides a theoretical basis and technical support for optimizing finned thermal energy storage units in building solar systems, thereby promoting higher energy efficiency and operational stability of such systems.