Hydrothermal characteristics and irreversibility behavior of microchannel heat sink operated with hybrid nanofluids: A critical assessment

Abstract

Recently, hybrid nanofluids have been outlined to enhance the cooling performance of microchannel heat sinks (MCHSs) and increase the heat dissipation rate in electronic devices. However, comparative assessments of hybrid nanofluids (HNFs) and water as coolants for MCHSs in terms of their hydrothermal performance and irreversibility characteristics are scarce. The present study aims to numerically assess the hydrothermal performance and entropy generation characteristics of various hybrid nanofluids in an MCHS for cooling a central processing unit (CPU). COMSOL Multiphysics software is used to solve the governing equations of a three-dimensional conjugate heat transfer model using the finite element method. The reduced graphene oxide decorated with cobalt oxide nanocomposite (rGO–Co3O4) and Fe3O4-coated MWCNT (MWCNT–Fe3O4) HNFs with temperature-dependent thermophysical properties and wide range of concentrations (0% ≤ φ ≤ 0.2%) are considered. The simulations are performed under constant Reynolds number (300 ≤ Re ≤ 1500) and constant flow rate (5.42 cm3/s ≤ Q ≤ 27.12 cm3/s) conditions. The results show that increasing the values of φ at a fixed Re significantly enhances the heat transfer coefficient; reduces the CPU temperature, thermal resistance, and total entropy generation; and improves temperature uniformity. However, the pressure drop and pumping power increase significantly. No significant enhancement is achieved when the HNFs are used instead of water at a constant flow rate, and a noticeable pumping power is obtained under all studied conditions. In conclusion, MWCNT–Fe3O4 HNF exhibited better combined thermohydraulic performance than the rGO–Co3O4 HNF.

Keywords

• Microchannel heat sink
• Thermohydraulic performance
• Hybrid nanofluids
• Entropy generation