An innovative method to improve the convective heat transfer of cross airflow over a circular cylinder by the application of secondary air flow jet is introduced in this study to suppress the boundary layer growth. The two-dimensional numerical model consists of a hollow circular cylinder made of copper, with 5 cm outside diameter and 4 cm inside diameter. The cylinder is located in the middle of an air channel 1.6 m long. Heat flux of 2W/cm2 was applied to the inner boundary of the cylinder. A secondary air jet was applied, from 5 mm slit on the upper wall of the air channel, with different angles (θ) of 15 to 165 degree with a 15-degree increment. The position of application of the air jet was also varied from the point above the stagnation point to other positions downstream. The distance of the applied jet relative to the diameter of the cylinder (S/D) is 0, 0.2, 0.4, 0.6, 0.8 and 1. The height of the air channel relative to the diameter of the cylinder (H/D) is changed from 2 up to 16. At constant height, the total mass flow rate is kept constant in both cases, with and without jet. After validation, a comparison between Nusselt number in all cases and the case where there is no air jet was carried out. Results show that there is an enhancement of the average heat transfer coefficient of up to twelve times the case with no jet.