The hydrodynamic study of nanofluids in microchannel is carried out. For this, three microchannels of hydraulic diameters of 130, 211 and 300 μm are fabricated by photolithographic and wet etching processes on silicon wafers. Alumina nanofluids with concentrations 0.25. vol.%, 0.5. vol.% and 1.0. vol.% with particle sizes 45. nm and 150. nm are prepared, stabilized and characterized by standard methods like sonication, pH variation, Transmission Electron Microscope (TEM) and Dynamic Light Scattering (DLS) measurements. The base fluids used are water and Ethylene Glycol. The effect of volume fraction, channel size, particle size and base fluids are presented and analyzed. It is shown that there is an early transition to turbulence for 211 and 301 μm channels. In addition, numerical modeling is carried out by using mixture rule and discrete phase modeling approach. This approach is found to be more suitable at higher Reynolds numbers whereas at lower Reynolds numbers the conventional mixture model can be used. Shear induced particle migration is identified to be an important phenomenon at higher Reynolds number and hence the reason for difference between these two models. © 2012 Elsevier Inc.