In this work, forced convection heat transfer through a horizontal pipe built-in with/without twisted tape-inserts is numerically studied under a uniform heat flux condition. Water is used as a working fluid. The governing equations are numerically solved in the domain by a finite volume method (FVM) using the Realizable κ–ε (RKE) model. The computational results are performed for a range of the Reynolds number (4000 ≤ Re ≤ 9000), the twisted ratio (4.0 ≤ TR ≤ 6.0), and heat flux (5000 ≤ q ≤ 1000 W/m²). Two type of twisted tape which inserts across a circular pipe (P-TT) and (V-cut) are carried out. The influence of these parameters on the local, average Nusselt Number and the thermal performances were examined and compared with a plain pipe under similar conditions. The results show that the average Nusselt number and friction factor raise as the twisted ratio rise for any value of Reynolds number. Furthermore, thermal performance factor tended to increase with increasing Re and decreasing tape twist ratio. Obviously, the (V-cut) twisted- tape and (P-TT) twisted tape with TR = 4 gave a higher mean thermal performance factor (4.45, and 4.19) than that with TR = 6, respectively. Finally, the present study can offer some useful results to select optimum geometrical parameters for use in shell and tube heat exchangers with a twisted tape inserted based on their specific applications.