This paper illustrates how practical application of nanofluids as working fluid to enhance solar flat plate collector efficiency. A numerical investigation of laminar convective heat transfer flow throw a solar collector is conducted, by using CuO-water nanofluids. The effectiveness of these nanofluids is compared to conventional working fluid (water), wherein Reynolds number and nanoparticle volume concentration in the ranges of 25-900 and 0-10 % respectively. The effects of Reynolds number and nanoparticles concentration on the skin-friction and heat transfer coefficients are presented and discussed later in this paper. Results show that the heat transfer increases with increasing both nanoparticles concentration and Reynolds number, where nanofluid CuO-water gives best improvement in terms of heat transfer.