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

Meng X, Li Y - Nanoscale Res Lett (2015)

Bottom Line: The two solvers are used for same cases and compared to corresponding experimental results.By comparison, the average natural Nusselt numbers of water and Al2O3/water nanofluids are found to increase with the Rayleigh number.The temperature-dependent solver is found better for water and 1% Al2O3/water nanofluid cases, while the original solver is better for 4% Al2O3/water nanofluid cases.

View Article: PubMed Central - PubMed

Affiliation: Research Group of Offshore Engineering, School of Marine Science and Technology, Armstrong Building, Newcastle University, Newcastle upon Tyne, England NE1 7RU UK.

ABSTRACT
Natural heat convection of water-based alumina (Al2O3/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 Al2O3/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% Al2O3/water nanofluid cases, while the original solver is better for 4% Al2O3/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.

No MeSH data available.


Related in: MedlinePlus

Grid independence check.
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Fig3: Grid independence check.

Mentions: Dimensionless temperature T* and location X* are defined in (16) and (17) for the grid independence check, respectively. Results of T* and X* on the cylinder longitudinal central line are compared to find the most appropriate mesh strategy. By the comparison in Figure 3, mesh strategies Δd = 2 mm and Δd = 1 mm are found to predict nearly exactly the same results. This indicates the mesh strategy Δd = 2 mm is good enough for the present study. However, the strategy Δd = 1 mm is eventually selected to capture even more detailed velocity and temperature features in near-wall regions. Compared to normal two-dimensional simulations, the cell amount is considerably increased in this work. Although non-uniform grid strategies are employed to reduce the total cell number, there are still about 0.4 million cells used in the present work (Figure 2D).Figure 3


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

Meng X, Li Y - Nanoscale Res Lett (2015)

Grid independence check.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4385295&req=5

Fig3: Grid independence check.
Mentions: Dimensionless temperature T* and location X* are defined in (16) and (17) for the grid independence check, respectively. Results of T* and X* on the cylinder longitudinal central line are compared to find the most appropriate mesh strategy. By the comparison in Figure 3, mesh strategies Δd = 2 mm and Δd = 1 mm are found to predict nearly exactly the same results. This indicates the mesh strategy Δd = 2 mm is good enough for the present study. However, the strategy Δd = 1 mm is eventually selected to capture even more detailed velocity and temperature features in near-wall regions. Compared to normal two-dimensional simulations, the cell amount is considerably increased in this work. Although non-uniform grid strategies are employed to reduce the total cell number, there are still about 0.4 million cells used in the present work (Figure 2D).Figure 3

Bottom Line: The two solvers are used for same cases and compared to corresponding experimental results.By comparison, the average natural Nusselt numbers of water and Al2O3/water nanofluids are found to increase with the Rayleigh number.The temperature-dependent solver is found better for water and 1% Al2O3/water nanofluid cases, while the original solver is better for 4% Al2O3/water nanofluid cases.

View Article: PubMed Central - PubMed

Affiliation: Research Group of Offshore Engineering, School of Marine Science and Technology, Armstrong Building, Newcastle University, Newcastle upon Tyne, England NE1 7RU UK.

ABSTRACT
Natural heat convection of water-based alumina (Al2O3/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 Al2O3/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% Al2O3/water nanofluid cases, while the original solver is better for 4% Al2O3/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.

No MeSH data available.


Related in: MedlinePlus