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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

Vectors of secondary flow and Contours of dimensionless temperature for different Ri and tube inclinations.
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Figure 5: Vectors of secondary flow and Contours of dimensionless temperature for different Ri and tube inclinations.

Mentions: For a given nanoparticle mean diameter and concentration (dp = 28 nm, Φ = 0.04) the effect of tube inclinations on the secondary flow vector and dimensionless temperature are shown in Figure 5 for two different Richardson numbers. As mentioned the tube is considered to be made of copper which is a high thermal conductive metal. This transfers the heating energy from the top half surface of tube to the bottom half. Thus, the fluid at the bottom section could also be warm. The latter generates the secondary flow if it would be enough temperature differences. Since the warmer fluid tends to move upward and the colder goes down. In the case of higher Richardson number, the secondary flow is well established and significantly affects the fluid flow. Hot flow from the near wall region goes up and then backs downward at the centreline region. While at the lower Ri, where the circumferential temperature variation is low the strength of secondary flow is low. By tube inclination the warmer fluid is more accumulated at the upper part of tube because of decreasing secondary flow strength. Increasing the tube inclination augments the near wall axial buoyancy force while the radial component decreases. Thus, the strongest secondary flow vector is seen in the case of horizontal tube.


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)

Vectors of secondary flow and Contours of dimensionless temperature for different Ri and tube inclinations.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 5: Vectors of secondary flow and Contours of dimensionless temperature for different Ri and tube inclinations.
Mentions: For a given nanoparticle mean diameter and concentration (dp = 28 nm, Φ = 0.04) the effect of tube inclinations on the secondary flow vector and dimensionless temperature are shown in Figure 5 for two different Richardson numbers. As mentioned the tube is considered to be made of copper which is a high thermal conductive metal. This transfers the heating energy from the top half surface of tube to the bottom half. Thus, the fluid at the bottom section could also be warm. The latter generates the secondary flow if it would be enough temperature differences. Since the warmer fluid tends to move upward and the colder goes down. In the case of higher Richardson number, the secondary flow is well established and significantly affects the fluid flow. Hot flow from the near wall region goes up and then backs downward at the centreline region. While at the lower Ri, where the circumferential temperature variation is low the strength of secondary flow is low. By tube inclination the warmer fluid is more accumulated at the upper part of tube because of decreasing secondary flow strength. Increasing the tube inclination augments the near wall axial buoyancy force while the radial component decreases. Thus, the strongest secondary flow vector is seen in the case of horizontal tube.

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