variavel0=<b>Carlos Enrique Pico</b> - capico@mecanica.ufu.br Universidade Federal de Uberlāndia
<b>Oscar Saul Hernandez</b> - oscarhm@mecanica.ufu.br Universidade Federal de Uberlāndia
<b>Aristeu Silveira Neto</b> - aristeus@mecanica.ufu.br Universidade Federal de Uberlāndia
<b>Jaime Vilela Resende</b> -  Universidade Federal de Uberlāndia
<b>Abstract.</b> With the aim of develop a computational tool for thermodynamic optimization of heat exchangers, a code was implemented to solve the Navier-Stokes equations in an axisymmetric domain using the finite volume method and central differencing with Runge- Kutta explicit temporal advance and pressure-velocity coupling of fractional step type. This work present results of the numeric simulation of the fully developed flow with heat transfer in a tube of circular section with ribs or obstacles periodically spaced in the flow direction. The simulations are made in two regimes, laminar and turbulent out of the completely rough area and four different geometries. In the cases with high Reynolds number, the Smagorinsky subgrid model with damping function was used to include the effects of the quasi-two-dimensional scales not solved. In both cases the primitive variables were decomposed to use periodic boundary conditions in the flow direction and non slip in the walls. The results obtained in laminar regime are satisfactory and in turbulent regime they show the deficiency of the Smagorinsky subgrid model when it is applied in two-dimensional domains
<b>Keywords.</b> Forced Convection, Finite Volume, Subgrid Model, Enhanced Surfaces.