Three dimensional numerical study on a trapezoidal microchannel heat sink with different inlet/outlet arrangements utilizing variable properties nanofluid

Nowadays, microchannels as closed circuits channels for fluid flow and heat removal are an integral part of the silicon-based electronic microsystems. Most of previous numerical studies on microchannel heat sinks (MCHS) have been performed for a two-dimensional domain using constant properties of the working fluid. In this study, laminar fluid flow and heat transfer of variable properties Al2O3-water nanofluid in a trapezoidal MCHS, consisted of five trapezoidal microchannels have been studied. The three dimensional solution domains include the whole flow field and the complete MCHS solid parts. Four inlet/outlet arrangements, three pressure drops of 5, 10 and 15 kPa and nanoparticles volume fractions between 0 and 4% are assumed and the effects of these arrangements, properties variations and the Brownian motion on the heat sink performance quantified. The results indicate that the A-type heat sink, for which the inlet and outlet are placed horizontally at the center of the north and the south walls, has a better heat transfer performance, smaller thermal resistance and provides more uniform substrate temperature distribution. Temperature-dependent properties increases the heat transfer between 2.7% and 3.39%, decreases the thermal resistance between 3.49% and 6.29 % and decreases the ratio of difference between the maximum and minimum substrate temperatures to the heat flux between 3.3% and 7.19%. Presence of the Brownian motion showed a similar trend but with a slighter importance.