Comparative analysis on the performance of MgO-based nanofluids in hexagonal and circular tube heat sink

This study presents an experimental evaluation of the thermal–hydraulic performance of MgO-based nanofluids at a nanoparticle volume concentration of 0.01vol% flowing through hexagonal and circular mini-channel heat sinks. The hexagonal mini-channel configuration exhibits a 15% enhancement in the heat transfer coefficient and a 10% increase in the Nusselt number compared with the circular tube geometry. These improvements are attributed to geometry-induced secondary flow formation, increased shear rates, and effective thinning of the thermal boundary layer, collectively intensifying convective heat transfer. The enhanced thermal performance is accompanied by a 10% increase in friction factor and 8% increase in pumping power due to elevated wall shear stress and intensified flow disturbances. Among the selected nanofluids, the MgO–DIW nanofluid showed a superior thermal performance compared to MgO–EG nanofluid, owing to its higher intrinsic thermal conductivity and more effective heat transfer characteristics. The combined effect of nanoparticle-enhanced thermal conductivity at low volume concentration and non-circular channel geometry confirms that hexagonal mini-channel heat sinks offer improved heat removal capability while maintaining acceptable hydraulic penalties, making them suitable for compact and high-performance thermal applications.