Buoyancy-Driven Heat Transfer Performance of Pure and Hybrid Nanofluids in Minienclosure

The buoyancy-driven heat transfer performance of nanofluids in a square minienclosure has been investigated in the present numerical study. A two-dimensional two-phase mixture model has been developed, validated, and then used for the investigation. Pure water, aluminum oxide, copper, aluminum, and single-walled carbon nanotube nanofluids with base-fluid hybridization (water plus methanol) were used in analyzing the heat transfer performance. The flow as well as the heat transfer characteristics of nanofluids with different particle volume concentrations, particle diameters, and base-fluid hybridizations at different Grashof numbers Gr were reported. A significant enhancement in the average Nusselt number was observed at high Grashof numbers, high particle volume concentrations, low particle diameters, and low methanol percentage in the base fluid. Two equivalent nanofluid pairs of 1vol. % aluminum oxide (d(p)=30nm) and 1vol. % copper (d(p)=100nm) as well as 1vol. % single-walled carbon nanotube and 3vol. % copper (d(p)=100nm) with similar heat transfer characteristics were observed in the present study. This provided a better switching option in choosing an efficient working fluid with minimum cost based on the cooling requirement. It was also observed that, by dispersing single-walled carbon nanotube nanoparticles, one could enhance the heat transfer characteristics of the base fluid containing methanol as antifreeze.