Numerical Investigation of Two-Phase Thermal-Hydraulic Characteristics and Entropy Generation of Water-Based Al₂O₃-Cu Hybrid Nanofluids in Microchannel Heat Sink

Abstract

This study employs numerical simulations to investigate the impact of water-based hybrid nanofluid containing copper-alumina nanoparticles using two-phase Eulerian-Eulerian model and finite volume approach to solve the conjugate heat transfer problem in a three-dimensional microchannel heat sink. The aim is to numerically evaluate the thermal behaviour and performance criteria of the microchannel heat sink using Ansys workbench, while determining the influence of volume concentration and Reynolds number (Re) on Nusselt number, friction factor and entropy generation. Generally, the heat sink consists of a silicon cylindrical structure block forming a microchannel heat sink with an internal heat generation of 10⁸ W/m^3. The study involves varying the Reynolds number across a range of 100 to 500. This variation applies to distinct volume concentrations of alumina-copper nanoparticles, specifically alternating between 0.25%, 0.50%, and 0.75% for a volume fraction of 1%. Additionally, the volume concentration was further adjusted within the range of 1% to 4%. The verification of the numerical models shows excellent agreement with literature. The results reveal that higher relative concentrations of copper nanoparticles lead to improved thermal enhancement of the hybridized nanofluid. An increase in both the Reynolds number (Re) and the concentration of Cu in the hybrid nanofluids caused a reduction in total entropy generation and thermal entropy generation. For Re = 500 and volume concentration of 4% in relation to the base fluid, the friction factor increases by less than 1%, the Nusselt number experienced an increase of 8.73% while the total entropy generation rate experiences 4.9% increase. At a concentration of 4.0% volume, the maximum figure of merit corresponds to a Reynolds number of 100 with 9.10% shift from 1.0% volume of hybrid nanofluid.