In this work we present results of direct numerical simulations (DNS) of the flow in a circular
pipe at moderate Reynolds numbers, where a uniform heat flux is imposed on the walls. The
simulations are performed by varying the Reynolds number (Re) and the Prandtl number (P r),
which allows studying the statistics of the turbulent variables in all observed cases. We compare the
non-dimensional heat transfer coefficient Nu (Nusselt number) with the experimental correlations
producing very accurate results.