Experimental investigation of conjugate heat transfer in nanofluid-cooled microchannel heat sink to mitigate back axial conduction at low Reynolds numbers

This study investigates the conjugate heat transfer performance of microchannel heat sinks (MCHS) cooled by alumina nanofluids, with a focus on mitigating back axial conduction at low Reynolds numbers (10 <= Re <= 50). Back axial conduction, a critical issue in laminar flows, impairs the cooling efficiency of microchannel systems. In this experimental work, a stainless steel heat sink with 18 circular microchannels was tested for alumina nanofluid efficacy under heat fluxes of 3750 and 6875 W m-2 at the top surface. Experimental results reveal that alumina nanofluids reduced back conduction by 51.54% compared to DI water, resulting in a 29% reduction in surface temperatures. Nanofluid concentrations ranging from 1 to 4% (m/m) improved the convective heat transfer performance by enhancing the bulk fluid temperature profiles along the microchannel. The study further explores the influence of Maranzana and Reynolds numbers, finding that increasing Re reduces back conduction while higher Maranzana numbers amplify axial conduction effects. Transient experiments revealed that nanofluids limit the inlet temperature rise to 86% compared to 140% for DI water at Re = 10, validating their superior thermal performance. Comprehensive experimental data validated the superior heat dissipation capabilities of nanofluids, highlighting their effectiveness in enhancing thermal performance. The findings demonstrate the viability of using alumina nanofluids for advanced thermal management in microelectronics, providing a scalable solution to improve cooling efficiency in high-heat-flux applications under low-Reynolds-number conditions.