In this study, a concentric tube heat exchanger with coiled wire turbulators were analysised numerically by a CFD code namely ANSYS FLUENT using RNG k-ε Turbulent Model in order to be reduced heat exchanger sizes and increased heat transfer enhancement. Figure A. The changing of numerical Nu number according to Re numberPurpose: In this study, it is aimed to compare numerical models with an experimental system previously study in literature by using passive method one of heat transfer enhancement of a concentric tube heat exchanger with coiled wire turbulators. Theory and Methods:The analyses were done in a range of Reynolds (Re) number from 3000 to 18000. The numerical simulations were done by using a CFD code namely ANSYS FLUENT, using finite volume method. In numerical analysis, three main turbulence models of RNG k-ε were employed in the simulations such as Model ➀ (RNG-Standard wall function), Model ➁ (RNG-Non-Equilibrium wall function) and Model ➂ (RNG-Enhanced wall treatment). Results:The numerical analyses carried out to compare with the experimental results in order to determine the best fitting model using each three main turbulence models of RNG k-ε model, Model ➀ has given the best fitting result. Conclusion:When turbulence models are compared with experimental results; Model ➀ has given more fitting result than Model ➁. Model ➂ is far from experimental results compared to other solutions. No k-ε model is not fitting with the data obtained from the experiment results in the Re Number range of 3000 ≤ Re ≤ 7000. When close to Re number value of 7000, the Nu number values obtained by Model ➂ have been far from experimental results.