Nanoparticle fluids are considered to offer significant advantages over conventional heat transfer fluids. In the present work the governing continuity, momentum and energy equations has been solved for pure water and water based Al2O3 nanofluid flowing on a semiinfinite slab, applying finite element by Ritz-Galerkin approach. The results showed that compared with water, the heat transfer behavior of nanofluid presents a considerable enhancement in convective heat transfer with increasing particle volume fraction of nanofluid. Moreover, increasing the particle volume fraction to 5%, results in increasing the rate of heat transfer 9% compared with that of pure water, which is in good agreement with numerical solutions