CFD-based numerical investigation of convective heat transfer in multi-channel micro-exchangers using MWCNT–water nanofluid

Efficient cooling is a key factor influencing the performance of compact electronic systems, which requires advanced thermal management. Microchannel Heat Exchangers (MCHEs) are increasingly becoming popular due to their high surface area-to-volume ratio and ability to dissipate high heat flux. The current study aims to explore the performance of MCHEs using a water-based, multiwalled carbon nanotube-blended nanofluid as coolant under different channel counts and geometries. A 3D CFD model was developed in ANSYS Fluent using the finite volume method, assuming constant thermophysical properties and steady-state, laminar flow, with uniform heat flux boundary conditions. An aluminum MCHE of dimensions 45 mm × 45 mm × 7 mm was analyzed with five channel geometries (square, circular, sawtooth, cross, and curved sawtooth) at three channel counts (5, 8, and 11). Two concentrations of multi-walled carbon nanotube (MWCNT)–water nanofluid (0.1 and 0.2%) were considered. Results exhibited that the baseline configuration (Square channel, 5 channels, water as coolant) achieved a convective heat transfer coefficient of 2008.24 W/m²K, overall heat transfer coefficient (U) of 1258.75 W/m²K, and thermal effectiveness (ε) of 0.102. The optimum configuration, curved sawtooth geometry with 5 channels and 0.2% MWCNT nanofluid, yielded h = 8271 W/m²K, U = 6590 W/m²K, and ε = 0.4765. ANOVA analysis confirmed channel geometry as the most influential factor, contributing 70.6% to effectiveness and 78.2% to the overall heat transfer coefficient.