Laminar forced convection of a water-based suspension of Al 2O 3 nanoparticles through in-line and staggered tube banks with constant wall temperature boundary condition have been investigated numerically. A two phase mixture model is employed to simulate the nanofluid convection, taking into account appropriate thermophysical properties. Nanoparticles are assumed spherical with a diameter equal to 50 nm. The effects of Reynolds number and nanoparticle volume concentration on the flow and heat transfer behavior are studied. Results show that convective heat transfer coefficient and pressure drop for nanofluids is greater than that of the base fluid. It is found that the heat transfer enhancement increases with increase in Reynolds number and nanoparticle volume concentration. In general, the heat transfer in a staggered array of tubes is found to be higher than that in an in-lined array of tubes.