The article reports the results of heat transfer experimental tests on water-based TiO2 (9wt%) and SiC (3, 6, 9wt%) nanofluids. Measurements were performed in a two-loop test rig for immediate comparison of the thermal performances of the nanofluid with the base fluid. The convective heat transfer is evaluated in a circular pipe heated with uniform heat flux (from 20 to 240 kW/m2) and flow regimes from laminar to turbulent. Tests have been performed to compare the heat transfer of nanofluids and water at the same velocity (from 0.7 to 1.6m/s) or Reynolds number (from 300 to 6000), and they have also been compared with values calculated from some of the most widely used correlations. The analysis of the experimental data shows a strong dependence on the parameter used, while both the nanofluid and water data have the same agreement with the calculated values. Nanofluids were manufactured through a two-step procedure: laser synthesis of nanoparticles followed by dispersion in water.