Improving the performance of latent heat storage systems is essential because it can help to increase energy efficiency and reduce the consumption of fuel resources. These improvements will ultimately lead to more sustainable development of thermal systems and reduction of environmental impacts. In this study, a numerical investigation is conducted to determine whether a triple-tube latent heat storage system with a counter-clockwise rotating middle tube containing PCM performs better with a stationary or rotating interior tube containing hot water flow. The effect of the interior tube rotation speed (ranging from − 2 to 2 rad/s in increments of 0.25 rad/s) on the time variation of overall and local values of the liquid fraction and temperature of the PCM was analyzed. The results showed that the system with a stationary interior tube outperformed those with a rotating interior tube in terms of melting efficiency. The PCM melting time for the system with a stationary interior tube was 481.8 s, while the shortest melting time among the rotating systems (486.6 s) occurred when the interior tube rotated clockwise at a speed of 2 rad/s. Conversely, the longest melting time (789 s) was observed when the interior tube rotated at 2 rad/s clockwise.
