Nuclear fuel elements generally consists of cladding rods containing the fuel pellets, with the coolant flowing axially through them. The thermal design of such elements only can be carried out if information about the heat transfer process to the coolant be avaiable, wich demmands a detailed description of the velocity field of flow. In the present work a zero equation model of turbulence and a wall law to energy transfer are applied to compute the velocity and temperature fields, and also the angular distribution of local wall sheat stress and nusselt number in the wall of a typical subchannel of nuclear fuel elements, for turbulents and fully developed flows,steady state, with incompressible, temperature independent fluids, flowing axially through triangular arrays of rods in differents aspect rations (P/D) and Reynods number (Re). The results are compared with experimental data of others authors, obtained from literature and show agreement.