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Numerical Simulation of Natural Convection of a Nanofluid in an Inclined Heated Enclosure Using Two-Phase Lattice Boltzmann Method: Accurate Effects of Thermophoresis and Brownian Forces.

Ahmed M, Eslamian M - Nanoscale Res Lett (2015)

Bottom Line: The effects of thermophoresis and Brownian forces which create a relative drift or slip velocity between the particles and the base fluid are included in the simulation.The effect of thermophoresis is considered using an accurate and quantitative formula proposed by the authors.Some of the existing results on natural convection are erroneous due to using wrong thermophoresis models or simply ignoring the effect.

View Article: PubMed Central - PubMed

Affiliation: Department of Mechanical Engineering, Assiut University, Assiut, 71516, Egypt.

ABSTRACT
Laminar natural convection in differentially heated (β = 0°, where β is the inclination angle), inclined (β = 30° and 60°), and bottom-heated (β = 90°) square enclosures filled with a nanofluid is investigated, using a two-phase lattice Boltzmann simulation approach. The effects of the inclination angle on Nu number and convection heat transfer coefficient are studied. The effects of thermophoresis and Brownian forces which create a relative drift or slip velocity between the particles and the base fluid are included in the simulation. The effect of thermophoresis is considered using an accurate and quantitative formula proposed by the authors. Some of the existing results on natural convection are erroneous due to using wrong thermophoresis models or simply ignoring the effect. Here we show that thermophoresis has a considerable effect on heat transfer augmentation in laminar natural convection. Our non-homogenous modeling approach shows that heat transfer in nanofluids is a function of the inclination angle and Ra number. It also reveals some details of flow behavior which cannot be captured by single-phase models. The minimum heat transfer rate is associated with β = 90° (bottom-heated) and the maximum heat transfer rate occurs in an inclination angle which varies with the Ra number.

No MeSH data available.


Related in: MedlinePlus

Schematic of the physical domain with the thermal boundary conditions and the coordinate system. All flow velocities at the walls are zero
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Fig1: Schematic of the physical domain with the thermal boundary conditions and the coordinate system. All flow velocities at the walls are zero

Mentions: A differentially heated enclosure is considered as the starting position of the cell (inclination angle β = 0), where the left wall is kept at a higher temperature TH, the right wall at TL, and the bottom and top walls are kept insulated. When the enclosure is tilted 90°, the bottom-heated configuration is retrieved. Intermediate angles of 30° and 60° are studied as well. Fig. 1 shows the problem geometry and boundary conditions. This is a thermal boundary driven flow with all velocities zero on the walls.Fig. 1


Numerical Simulation of Natural Convection of a Nanofluid in an Inclined Heated Enclosure Using Two-Phase Lattice Boltzmann Method: Accurate Effects of Thermophoresis and Brownian Forces.

Ahmed M, Eslamian M - Nanoscale Res Lett (2015)

Schematic of the physical domain with the thermal boundary conditions and the coordinate system. All flow velocities at the walls are zero
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4508308&req=5

Fig1: Schematic of the physical domain with the thermal boundary conditions and the coordinate system. All flow velocities at the walls are zero
Mentions: A differentially heated enclosure is considered as the starting position of the cell (inclination angle β = 0), where the left wall is kept at a higher temperature TH, the right wall at TL, and the bottom and top walls are kept insulated. When the enclosure is tilted 90°, the bottom-heated configuration is retrieved. Intermediate angles of 30° and 60° are studied as well. Fig. 1 shows the problem geometry and boundary conditions. This is a thermal boundary driven flow with all velocities zero on the walls.Fig. 1

Bottom Line: The effects of thermophoresis and Brownian forces which create a relative drift or slip velocity between the particles and the base fluid are included in the simulation.The effect of thermophoresis is considered using an accurate and quantitative formula proposed by the authors.Some of the existing results on natural convection are erroneous due to using wrong thermophoresis models or simply ignoring the effect.

View Article: PubMed Central - PubMed

Affiliation: Department of Mechanical Engineering, Assiut University, Assiut, 71516, Egypt.

ABSTRACT
Laminar natural convection in differentially heated (β = 0°, where β is the inclination angle), inclined (β = 30° and 60°), and bottom-heated (β = 90°) square enclosures filled with a nanofluid is investigated, using a two-phase lattice Boltzmann simulation approach. The effects of the inclination angle on Nu number and convection heat transfer coefficient are studied. The effects of thermophoresis and Brownian forces which create a relative drift or slip velocity between the particles and the base fluid are included in the simulation. The effect of thermophoresis is considered using an accurate and quantitative formula proposed by the authors. Some of the existing results on natural convection are erroneous due to using wrong thermophoresis models or simply ignoring the effect. Here we show that thermophoresis has a considerable effect on heat transfer augmentation in laminar natural convection. Our non-homogenous modeling approach shows that heat transfer in nanofluids is a function of the inclination angle and Ra number. It also reveals some details of flow behavior which cannot be captured by single-phase models. The minimum heat transfer rate is associated with β = 90° (bottom-heated) and the maximum heat transfer rate occurs in an inclination angle which varies with the Ra number.

No MeSH data available.


Related in: MedlinePlus