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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

Axial evolution of the peripheral average convective heat transfer coefficient.
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Figure 9: Axial evolution of the peripheral average convective heat transfer coefficient.

Mentions: Axial evolution of the average peripheral convective heat transfer coefficient along the tube length is shown in Figure 9. In general h decreases and monotonically goes to its asymptotic value. Buoyancy forces components (axial and radial) significantly affected the variations of heat transfer coefficient. At the lower Ri for which the effect of buoyancy force is weak, maximum heat transfer coefficient could be seen in the case of horizontal tube (pure radial buoyancy force). While at the higher Richardson number the buoyancy forces augments and so both axial and radial components become considerable. Based on the value of the axial and radial components of the buoyancy force, the best tube inclination for which the highest heat transfer coefficient is achieved could be determined. For instance, at the low Ri, horizontal configuration gives the best heat transfer coefficient (among the other angle in Figure 9) while for the higher Richardson number (Ri = 5) it appears at tube inclination of α = 30. This behaviour is also seen for different nanofluids. However, using nanofluid enhances heat transfer coefficient. This enhancement becomes more important at the higher Richardson number.


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)

Axial evolution of the peripheral average convective heat transfer coefficient.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 9: Axial evolution of the peripheral average convective heat transfer coefficient.
Mentions: Axial evolution of the average peripheral convective heat transfer coefficient along the tube length is shown in Figure 9. In general h decreases and monotonically goes to its asymptotic value. Buoyancy forces components (axial and radial) significantly affected the variations of heat transfer coefficient. At the lower Ri for which the effect of buoyancy force is weak, maximum heat transfer coefficient could be seen in the case of horizontal tube (pure radial buoyancy force). While at the higher Richardson number the buoyancy forces augments and so both axial and radial components become considerable. Based on the value of the axial and radial components of the buoyancy force, the best tube inclination for which the highest heat transfer coefficient is achieved could be determined. For instance, at the low Ri, horizontal configuration gives the best heat transfer coefficient (among the other angle in Figure 9) while for the higher Richardson number (Ri = 5) it appears at tube inclination of α = 30. This behaviour is also seen for different nanofluids. However, using nanofluid enhances heat transfer coefficient. This enhancement becomes more important at the higher Richardson number.

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