In this report paper, the influence an electrically circular tube with annulus circular-ring (A-CR) inserts on heat transfer rate (Nu) and friction factor (f) behaviors were carried out. The main aim of this article is to study the heat transfer enhancement in a circular tube equipped with A-CRs which were used as re-circulating flow generator to improve heat transfer rate. In the experiments, the A-CRs were placed in tandem arrangement at three different annulus diameter ratios of d/Do = 0.1, 0.15, and 0.2, respectively. The experiments were taken place at the tube with uniform wall heat flux conditions in the range of Reynolds number between 6000 and 20,000.