Scale effects on fluid flow and heat transfer in microchannels

Many investigators have recently experimentally established that fluid flow and heat transfer characteristics in microchannels, used to cool electroni c chips, deviate from those of normally sized channels. Deviations increase as the channel size decreases, Many hypotheses were advanced to explain so me of the observed deviations. However, they were usually in contradiction with other observed deviations, Hence, no conclusive explanation has been g iven so far for these phenomena. In this work, observed deviations will be listed, different hypotheses advanced to interpret these deviations will be critically revised, Finally, a new hypothesis will be advanced based on th e increased role of surface roughness on flow and heat transfer in microcha nnels, Simple models will be built capable of reproducing observed trends f or both friction and heat transfer coefficient in the laminar region, as we ll as giving an improved prediction for the laminar turbulent transition.