In the present study the effect of adding MgO nanoparticles to the water on the turbulent flow thermal properties in a counter-flow heat exchanger is investigated experimentally. Experiments have been done in Reynolds number of 6,000 to 32,000 and nanoparticles volume fraction of 0.005 to 0.02. In this investigation convective heat transfer coefficient, pressure drop, friction factor and Nusselt number are measured and discussed. According to experimental data convective heat transfer coefficient, average Nusselt number, and pressure drop have direct mathematical relation with nanoparticles volume fraction and Reynolds number (with maximum enhancement of 31.96% in nanoparticles volume fraction of 2%). However, at certain nanoparticle volume fractions and Reynolds numbers, increasing nanoparticle volume fraction led to a reduction of the flow friction factor (1.63% when φ=0.5%). Also, irrespective of the nanoparticle volume fraction, increasing the Reynolds numbers caused decreases of the flow friction factor. Considering high cost of experimental studies as a problem, a new mathematical and statistical based correlation is presented to predict the Nusselt number with independent variables of φ, Pr and Re.