Enhancing the performance of latent heat storage systems is vital for optimizing energy conservation, reducing operational costs, and supporting the transition to a more resilient and sustainable energy infrastructure. In the current numerical research, the aim is to simultaneously use the rotation of the middle tube and the eccentricity of the inner hot tube to improve the melting performance of a triplex-tube latent heat energy storage system. In this system, the phase change material (PCM) is placed in the middle tube and the flow of hot water passes through the inner and outer tubes. The counterclockwise rotation speed of the middle tube is considered constant and equal to 1 rpm, while the eccentricity value ( ) and angle ( ) are changed in the ranges of 1–8 mm and 0–315°, respectively. Numerical simulations were conducted using Computational Fluid Dynamics (CFD) techniques implemented through Ansys Fluent 19.1 software. Examining the results of the numerical simulations revealed that the simultaneous use of the middle tube rotation and the eccentricity of inner wall does not always lead to an improvement of the melting performance of the system. Among the investigated cases, the lowest melting time, which is equal to 425.5 s and is 11.9 % lower than the value belonging to the concentric system, occurs in the case of =4 mm and =315°. Also, it was found that the PCM average temperature in this case is 3.55 K lower than the concentric system.
