Numerical assessment of the impacts of non-Newtonian nanofluid and hydrophobic surfaces on conjugate heat transfer and irreversibility in a silicon microchannel heat-sink

Abstract

BackgroundThe current investigation aims to examine the thermal and hydraulic performances and irreversibility of a non-Newtonian nanofluid including water-Carboxymethyl cellulose (CMC)/CuO in a silicon microchannel heat sink. MethodsThe finite volume method with SIMPLE algorithm and second-order upwind approach for discretizing the equations and power-law model for simulation of the viscosity of nanofluid were used in this numerical assessment. Hydrophobic and fully-hydrophobic surfaces are applied in this study by surface modification. Reynolds numbers in the range of 10 to 250, the volume fraction of nanoparticles between 0 and 1.5%, and slip coefficient of 0, 0.02, and 0.1 for ordinary, hydrophobic, and fully-hydrophobic surfaces, respectively, are employed in this numerical investigation to examine their effects on heat transfer and irreversibility under a constant heat flux of 50 W/cm2. The obtained results show that implementing the fully-hydrophobic surface, higher Reynolds number and nano-additives rate lead to considerable improvement in thermal characteristics of nanofluid flow, especially near the corner region of the rectangular microchannel. However, increasing the Reynolds number significantly boosts the pressure drop. Significant FindingsAnalyzing the related data to the second law of thermodynamics shows the least amount of total entropy generation belongs to the fully-hydrophobic surface, φ =1.5% and Re= 250.