The nanofluids are widely used for heat transfer applications in the various engineering applications. The nanoparticles dispersed uniformly in the base fluid on proper mixing. In the present study, Al 2 O 3 and CuO nanoparticles were selected and the changes in the heat transfer coefficient were investigated in the complete laminar and discrete points of transition fluid flow through a copper tube with constant heat flux. The heat transfer coefficient was investigated at different loading of Al 2 O 3 and CuO nanopowders ranging from 0.1% to 0.5% of volume concentration in each case for the laminar and transition fluid flow zones, which is then compared with the distilled water as a plain base fluid. It is found that the optimum enhancement in heat transfer is observed at relatively lower volume fraction of nanoparticles ranging between 0.2 to 0.3%. surface area, creating rough surface, or by changing system boundary conditions [1]. The active technique involves increasing the thermal conductivity of the base fluid itself is by addition of milli-sized metallic particles in the base fluid for heat augmentation. However addition of these particles suffers from high sedimentation time and more flow resistance, thereby requires higher pumping power. Further, these particles cause severe clogging and deposition at the corners and in pump valves creating malfunctioning of the system. The latest manufacturing process produces the ultra fine nanoparticles in metallic form, which has greatly influenced heat transfer methods. This forced to add further much finer grade particles, i. e. nano-sized particle to the base fluid in pure as well as an oxide form for the heat transfer enhancement. Such a fluid is often termed as nanofluids. This was first noted by Choi [2] in the year 1996 at the National Argonne Laboratory in U. S. A. The nanoparticles are produced by physical and chemical synthesis processes. The physical process involves mechanical grinding, mechanical milling, and inert gas condensation methods. Whereas chemical technique is associated with the chemical precipitation, chemical vapor deposition, spray pyrolysis band thermal spraying [2]. The single step and the two step technique facilitate the simultaneous production of nanopowders in crystalline, amorphous and disperse powders in the base fluid form. The nanofluids are the colloidal dilute dispersion of nanoparticles (a billionth of a meter) in small quantity of metals, oxides, carbides, or carbon nanotubes in the conventional base fluids such as water, ethylene glycol, or oil. The nanoparticle possesses superior thermal conductivity, lower specific heat, large surface area which makes nanofluids superior in an energy transport carrier.Since last few years, the research activities related to the nanofluids have increased drastically. The majority of the studies since last decade focused on the convective heat transfer enhancement in the laminar and the turbulent region of the fluid flow [3,4]. Suresh et al [3] experimentally studied the heat transfer and fric...
