An Experimental Study on Thermal–Hydraulic Performance of Oil-Based Nanofluids in Series and Parallel Sinusoidal Microchannel Heat Sinks

Efficient thermal management in compact systems such as microelectronic devices and aerospace modules demands advanced heat sink technologies. This study investigates the thermal–hydraulic behavior of SN500 oil-based nanofluids in sinusoidal microchannel heat sinks configured in both series and parallel layouts. Nanofluids were synthesized using SiO₂ and multi-walled carbon nanotube (MWCNT) nanoparticles at volume fractions of 0.05% and 0.1%. Experimental tests were conducted over a range of Reynolds numbers and operating temperatures (50°C to 60°C). The results showed that nanofluids enhanced convective heat transfer by 30–90% compared to base oil, with MWCNT-based fluids achieving the highest enhancement. The series configuration yielded superior heat transfer performance relative to the parallel configuration but at the cost of significantly increased pressure drops - up to 70% higher. Performance trends were validated against classical heat transfer correlations, and uncertainties were rigorously analyzed. These findings underscore the trade-off between thermal enhancement and flow resistance in microchannel heat sinks and offer design insights for optimized cooling systems using oil-based nanofluids in industrial applications.