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Conjugate heat transfer of laminar mixed convection of a nanofluid through an inclined tube with circumferentially non-uniform heating.

Allahyari S, Behzadmehr A, Sarvari SM - Nanoscale Res Lett (2011)

Bottom Line: Laminar mixed convection of a nanofluid consisting of water and Al2O3 in an inclined tube with heating at the top half surface of a copper tube has been studied numerically.The bottom half of the tube wall is assumed to be adiabatic (presenting a tube of a solar collector).Significant augmentation on the heat transfer coefficient as well as on the wall shear stress is seen.

View Article: PubMed Central - HTML - PubMed

Affiliation: Mechanical Engineering Department, University of Sistan and Baluchestan, P,O, Box 98164-161, Zahedan, Iran. amin.behzadmehr@eng.usb.ac.ir.

ABSTRACT
Laminar mixed convection of a nanofluid consisting of water and Al2O3 in an inclined tube with heating at the top half surface of a copper tube has been studied numerically. The bottom half of the tube wall is assumed to be adiabatic (presenting a tube of a solar collector). Heat conduction mechanism through the tube wall is considered. Three-dimensional governing equations with using two-phase mixture model have been solved to investigate hydrodynamic and thermal behaviours of the nanofluid over wide range of nanoparticle volume fractions. For a given nanoparticle mean diameter the effects of nanoparticle volume fractions on the hydrodynamics and thermal parameters are presented and discussed at different Richardson numbers and different tube inclinations. Significant augmentation on the heat transfer coefficient as well as on the wall shear stress is seen.

No MeSH data available.


Related in: MedlinePlus

Grid independence test: (a) centerline axial velocity, (b) fully developed temperature, (c) fully developed velocity and (d) distribution of nanoparticles volume fraction.
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Figure 2: Grid independence test: (a) centerline axial velocity, (b) fully developed temperature, (c) fully developed velocity and (d) distribution of nanoparticles volume fraction.

Mentions: This set of coupled non-linear differential equations was discretized with the finite volume technique. For the convective and diffusive terms a second order upwind method was used while the SIMPLEC procedure was introduced for the velocity-pressure coupling. The discretization grid is uniform in the circumferential direction and non-uniform in the other two directions. It is finer near the tube entrance and near the wall where the velocity and temperature gradients are important. Several different grid distributions have been tested to ensure that the calculated results are grid independent. The selected grid for the present calculations consists of 160, 32 and 36 nodes, respectively, in the axial, radial and circumferential directions. As shown in Figure 2 increasing the grid numbers does not significantly change the velocity and temperature of the nanofluid. The grid test on the nanoparticle volume fraction is shown in Figure 2d. It is seen that the nanoparticle concentration does not change with increasing the grid numbers in the radial direction. Other axial and radial profiles have also been verified to be sure the results are grid independent.


Conjugate heat transfer of laminar mixed convection of a nanofluid through an inclined tube with circumferentially non-uniform heating.

Allahyari S, Behzadmehr A, Sarvari SM - Nanoscale Res Lett (2011)

Grid independence test: (a) centerline axial velocity, (b) fully developed temperature, (c) fully developed velocity and (d) distribution of nanoparticles volume fraction.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211450&req=5

Figure 2: Grid independence test: (a) centerline axial velocity, (b) fully developed temperature, (c) fully developed velocity and (d) distribution of nanoparticles volume fraction.
Mentions: This set of coupled non-linear differential equations was discretized with the finite volume technique. For the convective and diffusive terms a second order upwind method was used while the SIMPLEC procedure was introduced for the velocity-pressure coupling. The discretization grid is uniform in the circumferential direction and non-uniform in the other two directions. It is finer near the tube entrance and near the wall where the velocity and temperature gradients are important. Several different grid distributions have been tested to ensure that the calculated results are grid independent. The selected grid for the present calculations consists of 160, 32 and 36 nodes, respectively, in the axial, radial and circumferential directions. As shown in Figure 2 increasing the grid numbers does not significantly change the velocity and temperature of the nanofluid. The grid test on the nanoparticle volume fraction is shown in Figure 2d. It is seen that the nanoparticle concentration does not change with increasing the grid numbers in the radial direction. Other axial and radial profiles have also been verified to be sure the results are grid independent.

Bottom Line: Laminar mixed convection of a nanofluid consisting of water and Al2O3 in an inclined tube with heating at the top half surface of a copper tube has been studied numerically.The bottom half of the tube wall is assumed to be adiabatic (presenting a tube of a solar collector).Significant augmentation on the heat transfer coefficient as well as on the wall shear stress is seen.

View Article: PubMed Central - HTML - PubMed

Affiliation: Mechanical Engineering Department, University of Sistan and Baluchestan, P,O, Box 98164-161, Zahedan, Iran. amin.behzadmehr@eng.usb.ac.ir.

ABSTRACT
Laminar mixed convection of a nanofluid consisting of water and Al2O3 in an inclined tube with heating at the top half surface of a copper tube has been studied numerically. The bottom half of the tube wall is assumed to be adiabatic (presenting a tube of a solar collector). Heat conduction mechanism through the tube wall is considered. Three-dimensional governing equations with using two-phase mixture model have been solved to investigate hydrodynamic and thermal behaviours of the nanofluid over wide range of nanoparticle volume fractions. For a given nanoparticle mean diameter the effects of nanoparticle volume fractions on the hydrodynamics and thermal parameters are presented and discussed at different Richardson numbers and different tube inclinations. Significant augmentation on the heat transfer coefficient as well as on the wall shear stress is seen.

No MeSH data available.


Related in: MedlinePlus