Flow structure and heat transfer of non-Newtonian fluids in microchannel heat sinks with dimples and protrusions

The flow structures and heat transfer of non-Newtonian fluids in a novel kind of microchannel heat sinks with dimples and protrusions were numerically investigated. The dimples and protrusions with a relative depth of 0.2 were vertically aligned to arrange on the opposite walls of the microchannel. The flow rate ranged from 3.72E-5 kg.s(-1) to 8.69E-5 kg.s(-1). The Fanning friction factor, form drag, frictional resistance, Nusselt number and thermal performance were analyzed to evaluate the overall thermal performance. Moreover, limiting streamlines and temperature distributions on the dimpled and protruded walls, as well as streamlines and dynamic viscosity distributions on the stream-wise middle sections, were used to investigate the effects of different parameters on the flow structure and heat transfer. New correlations of relative Fanning friction factor and Nusselt number were also proposed. It is shown that the heat transfer is enhanced, and the concentration of non-Newtonian fluids, flow rate and dimple protrusion geometry have obvious combined effects on the flow structures and heat transfer. For the proposed microchannels, working substances with concentrations of 500 ppm and 2000 ppm are preferred. (C) 2015 Elsevier Ltd. All rights reserved.