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Natural heat convection of water-based alumina (Al 2 O 3 /water) nanofluids (with volume fraction 1% and 4%) in a horizontal cylinder is numerically investigated. The whole three-dimensional computational fluid dynamics (CFD) procedure is performed in a completely open-source way. Blender, enGrid, OpenFOAM and ParaView are employed for geometry creation, mesh generation, case simulation and post process, respectively. Original solver ‘buoyantBoussinesqSimpleFoam’ is selected for the present study, and a temperature-dependent solver ‘buoyantBoussinesqSimpleTDFoam’ is developed to ensure the simulation is more realistic. The two solvers are used for same cases and compared to corresponding experimental results. The flow regime in these cases is laminar (Reynolds number is 150) and the Rayleigh number range is 0.7 × 10 7  ~ 5 × 10 7 . By comparison, the average natural Nusselt numbers of water and Al 2 O 3 /water nanofluids are found to increase with the Rayleigh number. At the same Rayleigh number, the Nusselt number is found to decrease with nanofluid volume fraction. The temperature-dependent solver is found better for water and 1% Al 2 O 3 /water nanofluid cases, while the original solver is better for 4% Al 2 O 3 /water nanofluid cases. Furthermore, due to strong three-dimensional flow features in the horizontal cylinder, three-dimensional CFD simulation is recommended instead of two-dimensional simplifications.   Electronic supplementary material  The online version of this article (doi:10.1186/s11671-015-0847-x) contains supplementary material, which is available to authorized users.

Numerical study of natural convection in a horizontal cylinder filled with water-based alumina nanofluid