A significant research has been done on the enhancement of thermal energy storage systems. This article details the numerical study conducted to understand the heat transfer and fluid flow characteristics of a concentric thermal energy storage subjected to different heat transfer fluid (HTF) velocities. Water is used as the working heat transfer fluid. The influence of flow parameter primarily the HTF velocity is studied in this article. Studies are conducted for concentric thermal energy storage diameter of 25 mm, and 10 mm inner diameter of concentric pipe, 200 mm length, and HTF velocity of 0.02, 0.1, 0.3, 0.5 m/s. It is found that the utilization of fins improves the heat transfer in tube in tank thermal storage system. Computational fluid dynamics (CFD) enables a more detailed study of the phase change thermal characteristics.