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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

Dynamic and thermal fields in the case of classical natural convection (without particles and Soret effect, Pr = 0.71).
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Related In: Results  -  Collection

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Figure 2: Dynamic and thermal fields in the case of classical natural convection (without particles and Soret effect, Pr = 0.71).

Mentions: Primarily considered a restrictive case of such a model that is the classical natural convection case for which, both influence due to particle volume fraction and Soret effect are considered negligible. Figure 2 shows the thermal and flow structure as obtained for two particular Rayleigh numbers, RT = 104 and 105, the values of the stream function at the cavity centre are also given for comparison. Such a structure appears 'conventional' and similar to results reported in the literature [32,33].


Heterogeneous nanofluids: natural convection heat transfer enhancement.

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

Dynamic and thermal fields in the case of classical natural convection (without particles and Soret effect, Pr = 0.71).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 2: Dynamic and thermal fields in the case of classical natural convection (without particles and Soret effect, Pr = 0.71).
Mentions: Primarily considered a restrictive case of such a model that is the classical natural convection case for which, both influence due to particle volume fraction and Soret effect are considered negligible. Figure 2 shows the thermal and flow structure as obtained for two particular Rayleigh numbers, RT = 104 and 105, the values of the stream function at the cavity centre are also given for comparison. Such a structure appears 'conventional' and similar to results reported in the literature [32,33].

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