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The present investigation presents numerically the thermo-hydraulic performance of annular curved tubes in the turbulent flow region. The three-dimensional (3D) computational fluid dynamic (CFD) model was developed by using a commercial ANSYS 14.5 package to get additional insights on the thermo-hydraulic performance on a level of detail that is not always available in experiment results. The turbulent k-ε realize model was employed to examine the effect of Al2O3-water and CuO-water nanofluids on the heat transfer and fluid flow characteristics at different key design parameters. Three coil geometry shapes (including helical, spiral, and conical), five annular cross-section shapes (including circular, elliptical, square, rectangular, and triangular), and three cross-section areas were also investigated in this study. The numerical simulations were carried out at Reynolds numbers of 4700 to 26,700 and nanofluid volume concentrations, φ of 1%, 3%, and 5%, with constant wall temperature (CWT) heat transfer boundary conditions. The result showed that the addition of Al2O3 (45 nm) and CuO (29 nm) nanoparticles to water improves the heat transfer coefficient by 48.8%, 25.7%, and 8.4% and 37.1%, 20%, and 8.7%, respectively, at φ of 5%, 3%, and 1%, while the penalty of pressure drop is approximately negligible. The heat transfer rate per unit pumping power for helical design achieved 21.6% and 5.34% higher than conical and spiral designs, respectively, for the same curvature ratio, cross-section area, and coil length. Also, the circular shape achieved a higher heat transfer enhancement than elliptical, square, rectangular, and triangular shapes by 4%, 14.6%, 17.8%, and 30.1%, respectively. The maximum thermo-hydraulic performance index reached 1.68 and 1.58 for both Al2O3-water and CuO-water nanofluids, respectively, at φ of 5%. Highlights: • Thermo-hydraulic performance of annular curved tubes was examined. • Three dimensional CFD numerical investigations were evaluated in the turbulent flow region. • Impact of tube geometry designs, cross-section area and (Al2O3 and CuO) nanoparticle was achieved. • Nusselt number, friction factor, rate of heat transfer per pumping power unit and thermo-hydraulic performance index were the main points. [ABSTRACT FROM AUTHOR]