This paper presents a numerical study on the heat transfer characteristics and cooling performance of a microchannel heat sink with water-γAl2O3 nanofluids having different nanoparticle volume fraction. In view of the small dimensions of the microstructures, the microchannel heat sink is modeled as a fluid-saturated porous medium in the simulation. The Forchheimer-Brinkman-extended Darcy equation is used to describe the fluid flow and the two-equation model with thermal dispersion is utilized for heat transfer. Typical results for the temperature distributions of the fin and fluid phase are presented for various values of the inertial force parameter. It is found that the fin temperature distribution is practically not sensitive to the inertial effect, while the fluid temperature distribution and the total thermal resistance change significantly due to the inertial force effect. In general, the effect of fluid inertia is to reduce the total thermal resistance and the temperature difference between the fin and the fluid phase. The total thermal resistances obtained from the present model with inertial effect match well with the available experimental results, whereas the thermal resistance is overestimated as the inertial effect is neglected.

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