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Heterogeneous nanofluids: natural convection heat transfer enhancement.

Oueslati FS, Bennacer R - Nanoscale Res Lett (2011)

Bottom Line: Owing to the pronounced Soret effect of these materials in combination with a considerable solutal expansion, the resulting solutal buoyancy forces could be significant and interact with the initial thermal convection.The obtained results, by solving numerically the full governing equations, are found to be in good agreement with the developed solution based on the scale analysis approach.The resulting convective flows are found to be dependent on the local particle concentration φ and the corresponding solutal to thermal buoyancy ratio N.

View Article: PubMed Central - HTML - PubMed

Affiliation: ENS-Cachan Dpt GC/LMT, 61, Av du Président Wilson 94235 Cachan Cedex, France. rachid.bennacer@dgc.ens-cachan.fr.

ABSTRACT
Convective heat transfer using different nanofluid types is investigated. The domain is differentially heated and nanofluids are treated as heterogeneous mixtures with weak solutal diffusivity and possible Soret separation. Owing to the pronounced Soret effect of these materials in combination with a considerable solutal expansion, the resulting solutal buoyancy forces could be significant and interact with the initial thermal convection. A modified formulation taking into account the thermal conductivity, viscosity versus nanofluids type and concentration and the spatial heterogeneous concentration induced by the Soret effect is presented. The obtained results, by solving numerically the full governing equations, are found to be in good agreement with the developed solution based on the scale analysis approach. The resulting convective flows are found to be dependent on the local particle concentration φ and the corresponding solutal to thermal buoyancy ratio N. The induced nanofluid heterogeneity showed a significant heat transfer modification. The heat transfer in natural convection increases with nanoparticle concentration but remains less than the enhancement previously underlined in forced convection case.

No MeSH data available.


Related in: MedlinePlus

Specific heat capacity versus nanoparticle concentration (Al2O3).
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Figure 3: Specific heat capacity versus nanoparticle concentration (Al2O3).

Mentions: In this article, despite the lack of experimental results, we use the relative specific heat capacity (ρCp)r, which is the most realistic in the physical sense that the relative density, which multiplies the relative specific heat (ρr)(Cp)r which is used by several authors. Indeed, this differentiation is crucial since it greatly affects the results, which is illustrated in Figure 3a. Indeed, the comparison clearly shows that the relative specific heat capacity (ρr)(Cp)r continues to grow with the particle fraction of nanofluid, in the case of classical formulation, when it decreases slightly for (ρCp)r.


Heterogeneous nanofluids: natural convection heat transfer enhancement.

Oueslati FS, Bennacer R - Nanoscale Res Lett (2011)

Specific heat capacity versus nanoparticle concentration (Al2O3).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211280&req=5

Figure 3: Specific heat capacity versus nanoparticle concentration (Al2O3).
Mentions: In this article, despite the lack of experimental results, we use the relative specific heat capacity (ρCp)r, which is the most realistic in the physical sense that the relative density, which multiplies the relative specific heat (ρr)(Cp)r which is used by several authors. Indeed, this differentiation is crucial since it greatly affects the results, which is illustrated in Figure 3a. Indeed, the comparison clearly shows that the relative specific heat capacity (ρr)(Cp)r continues to grow with the particle fraction of nanofluid, in the case of classical formulation, when it decreases slightly for (ρCp)r.

Bottom Line: Owing to the pronounced Soret effect of these materials in combination with a considerable solutal expansion, the resulting solutal buoyancy forces could be significant and interact with the initial thermal convection.The obtained results, by solving numerically the full governing equations, are found to be in good agreement with the developed solution based on the scale analysis approach.The resulting convective flows are found to be dependent on the local particle concentration φ and the corresponding solutal to thermal buoyancy ratio N.

View Article: PubMed Central - HTML - PubMed

Affiliation: ENS-Cachan Dpt GC/LMT, 61, Av du Président Wilson 94235 Cachan Cedex, France. rachid.bennacer@dgc.ens-cachan.fr.

ABSTRACT
Convective heat transfer using different nanofluid types is investigated. The domain is differentially heated and nanofluids are treated as heterogeneous mixtures with weak solutal diffusivity and possible Soret separation. Owing to the pronounced Soret effect of these materials in combination with a considerable solutal expansion, the resulting solutal buoyancy forces could be significant and interact with the initial thermal convection. A modified formulation taking into account the thermal conductivity, viscosity versus nanofluids type and concentration and the spatial heterogeneous concentration induced by the Soret effect is presented. The obtained results, by solving numerically the full governing equations, are found to be in good agreement with the developed solution based on the scale analysis approach. The resulting convective flows are found to be dependent on the local particle concentration φ and the corresponding solutal to thermal buoyancy ratio N. The induced nanofluid heterogeneity showed a significant heat transfer modification. The heat transfer in natural convection increases with nanoparticle concentration but remains less than the enhancement previously underlined in forced convection case.

No MeSH data available.


Related in: MedlinePlus