This study investigates the impact of the central tube position (eccentricity) on the thermal and fluid characteristics of a solid-liquid phase change material (PCM) during its melting inside a triplex tube latent heat energy storage unit. Two flow directions for the heat transfer fluid (HTF) are considered in the proposed investigation: co-current and counter-current. The energy storage material, is sandwiched between the inner and outer tubes. During the energy storage process, the HTF flows through both tubes, transferring heat to the PCM across two surfaces. This design differs from traditional double tube systems, which only have one heat exchange surface. To investigate this system, a CFD model have been employed and validated against existing experimental data. We conducted a mesh independence study to determine the optimal mesh size, and tested various time steps to balance accuracy and computational efficiency. Using this validated numerical model, we performed numerical investigations of the storage unit’s thermal behavior and performance. We specifically analyzed how the central tube’s eccentricity and the HTF flow direction influence the system’s thermal characteristics and performance. Our results are presented through various visualizations, including: liquid fraction plots, PCM’s average temperature, PCM’s liquid fraction and the melting time of the PCM. These findings provide insights into optimizing the design of the proposed triplex tube latent heat energy storage systems.