Evaluation of variable rotation on enhancing thermal performance of phase change heat storage tank

The rotation mechanism can effectively enhance convective heat transfer. Previous studies have been conducted to explore the potential application of its enhancement effect for melting process. It is of importance to highlight that the variable speed strategy offers more significant advantages for phase change heat storage devices with non-uniform melting characteristics. This study aimed to explore the impact of variable speed duration on the melting process. Firstly, the impact of different rotational speeds on the positive effect was investigated. Subsequently, the effectiveness of a variable speed scheme based on two rotational speeds in enhancing the thermal energy storage process was discussed. The effect of variable speed duration on the charging process, temperature distribution, heat transfer performance, and heat storage rate were qualitatively and quantitatively compared. The results indicate that selecting a rotational speed shifting time of 2000 s yielded the best melting performance for phase change heat storage, leading to a 17.37 % decrease in heat storage time and a 21.02 % improvement in the average variation rate of the liquid fraction and a significant 22.72 % enhancement in average thermal energy storage rate of TES tube compared to constant velocity. The optimized speed shifting time achieved quicker temperature response and higher thermal charging efficiency. This work provides valuable insights for the future application of rotation operating mechanisms with variable speed in optimization of thermal energy storage.