Heat transfer and flow characteristics of hybrid Al₂O₃/TiO₂–water nanofluid in a minichannel heat sink

Heat transfer enhancement in thermal systems has great importance in achieving better performances at decreased spaces. In the present work, by combining two passive enhancement methods of using miniaturized channels and utilizing nanofluid, the heat transfer from a heated surface is investigated. In this regard, the thermal performance of an Aluminum minichannel heat sink with rectangular cross-sections was experimentally investigated. The hydraulic diameter of the minichannels is 2 mm. Distilled water, TiO₂–water nanofluid, Al₂O₃-water nanofluid and hybrid Al₂O₃/TiO₂–water nanofluid were used with a volume fraction of 0.5% as coolants. Constant heat flux boundary condition was considered and maintained by a heater with the power of 36 W at the bottom of the heat sink. The effect of different Reynolds numbers ranged from 400 to 1000 on the thermal performance of the heat sink was evaluated. The experimental results indicated significant improvements in thermal characteristics by using nanofluids as a coolant instead of pure water. The convective heat transfer coefficient enhanced up to 16.97% compared to pure water. The wall temperature reduced up to 5 °C with using Al₂O₃/TiO₂–water hybrid nanofluid instead of pure water.