Heat transfer for cooling is essential in maintaining the desired performance and reliability over a very huge variety of products like electronic devices, computer, automobiles, high power laser system etc. Apart from the heat load amplification and heat fluxes caused by many industrial products, cooling is one of the major technical challenges encountered by the industries like manufacturing sectors, transportation, microelectronics, etc. Normally water, ethylene glycol and oil are being used as the fluid to carry away the heat in these devices. The development of nanofluid generally shows a better heat transfer characteristic than the water. A nanofluid is the suspension of nanoparticles in a base fluid. Nanofluids are promising fluids for heat transfer enhancement due to their anomalously high thermal conductivity. At present, there is significant discrepancy in nanofluid thermal conductivity data in the literature. On the other hand, thermal conductivity enhancement mechanisms of nanofluids have not been fully understood yet. The heat transfer coefficient of the nanofluid increases with an increase in the mass flow rate, also the heat transfer coefficient increases with the increase of the volume concentration of the nanofluid.