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Heat transfer augmentation in nanofluids via nanofins.

Vadasz P - Nanoscale Res Lett (2011)

Bottom Line: Theoretical results derived in this article are combined with experimental data to conclude that, while there is no improvement in the effective thermal conductivity of nanofluids beyond the Maxwell's effective medium theory (J.C.Maxwell, Treatise on Electricity and Magnetism, 1891), there is substantial heat transfer augmentation via nanofins.The latter are formed as attachments on the hot wire surface by yet an unknown mechanism, which could be related to electrophoresis, but there is no conclusive evidence yet to prove this proposed mechanism.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Mechanical Engineering, Northern Arizona University, P, O, Box 15600, Flagstaff, AZ 86011-5600, USA. peter.vadasz@nau.edu.

ABSTRACT
Theoretical results derived in this article are combined with experimental data to conclude that, while there is no improvement in the effective thermal conductivity of nanofluids beyond the Maxwell's effective medium theory (J.C. Maxwell, Treatise on Electricity and Magnetism, 1891), there is substantial heat transfer augmentation via nanofins. The latter are formed as attachments on the hot wire surface by yet an unknown mechanism, which could be related to electrophoresis, but there is no conclusive evidence yet to prove this proposed mechanism.

No MeSH data available.


Related in: MedlinePlus

Comparison of the present theory with experimental data of Liu et al. [23] (here redrawn from published data) of the effective thermal conductivity ratio for conditions compatible with specimen No. 4, leading to a Fourier number of Foq = 1.45 × 10-2 and a solid particles to total wire area ratio of as = 0.45.
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Figure 4: Comparison of the present theory with experimental data of Liu et al. [23] (here redrawn from published data) of the effective thermal conductivity ratio for conditions compatible with specimen No. 4, leading to a Fourier number of Foq = 1.45 × 10-2 and a solid particles to total wire area ratio of as = 0.45.

Mentions: The comparison between the theoretical results presented in this article with the experimental data [23] is presented in Figures 4, 5 and 6. The separation of these results into three different figures aims to better distinguish between the different curves and avoid overlapping as well as presenting the results on their appropriate scales. Figure 4 presents the results that are applicable to specimen No. 4 in Liu et al. [23] and corresponding to values of Foq = 1.45 × 10-2 and as = 0.45 in the theoretical model. Evaluating Maxwell's [4] effective thermal conductivity for specimen No. 4 leads to a value of 0.6018 W/mK, which is higher by 0.3% than that of the base fluid (water), i.e. . From the figure, it is evident that the theoretical results match very well with the digitized experimental data. Furthermore, the steady-state result for the ratio between the effective thermal conductivity and that of the base fluid was estimated from the digitized data to be clearly validating Maxwell's [4] predicted value. The results applicable to specimen No. 5 in Liu et al. [23] and corresponding to values of Foq = 1.1 × 10-2 and as = 0.55 in the theoretical model are presented in Figure 5. The very good match between the theory and the digitized experimental data is again evident. In addition, the ratio between the effective thermal conductivity and that of the base fluid was estimated from the digitized data to be again validating Maxwell's [4] predicted value of . The last result is presented in Figure 6, which corresponds to specimen No. 9 in Liu et al. [23] and to values of Foq = 6 × 10-3 and as = 0.35 in the theoretical model. The results are presented on an appropriately scaled vertical axis and show again a very good match between the theory presented in this article, and the experimental data as digitized from Liu et al. [23]. Since the volumetric solid fraction for this specimen was 0.2%, its corresponding Maxwell's [4] effective thermal conductivity for this specimen leads to a value of 0.6036 W/mK, which is higher by 0.6% than that of the base fluid (water), i.e. . The steady-state result for the ratio between the effective thermal conductivity and that of the base fluid was estimated from the digitized data to be validating again Maxwell's [4] predicted value.


Heat transfer augmentation in nanofluids via nanofins.

Vadasz P - Nanoscale Res Lett (2011)

Comparison of the present theory with experimental data of Liu et al. [23] (here redrawn from published data) of the effective thermal conductivity ratio for conditions compatible with specimen No. 4, leading to a Fourier number of Foq = 1.45 × 10-2 and a solid particles to total wire area ratio of as = 0.45.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211205&req=5

Figure 4: Comparison of the present theory with experimental data of Liu et al. [23] (here redrawn from published data) of the effective thermal conductivity ratio for conditions compatible with specimen No. 4, leading to a Fourier number of Foq = 1.45 × 10-2 and a solid particles to total wire area ratio of as = 0.45.
Mentions: The comparison between the theoretical results presented in this article with the experimental data [23] is presented in Figures 4, 5 and 6. The separation of these results into three different figures aims to better distinguish between the different curves and avoid overlapping as well as presenting the results on their appropriate scales. Figure 4 presents the results that are applicable to specimen No. 4 in Liu et al. [23] and corresponding to values of Foq = 1.45 × 10-2 and as = 0.45 in the theoretical model. Evaluating Maxwell's [4] effective thermal conductivity for specimen No. 4 leads to a value of 0.6018 W/mK, which is higher by 0.3% than that of the base fluid (water), i.e. . From the figure, it is evident that the theoretical results match very well with the digitized experimental data. Furthermore, the steady-state result for the ratio between the effective thermal conductivity and that of the base fluid was estimated from the digitized data to be clearly validating Maxwell's [4] predicted value. The results applicable to specimen No. 5 in Liu et al. [23] and corresponding to values of Foq = 1.1 × 10-2 and as = 0.55 in the theoretical model are presented in Figure 5. The very good match between the theory and the digitized experimental data is again evident. In addition, the ratio between the effective thermal conductivity and that of the base fluid was estimated from the digitized data to be again validating Maxwell's [4] predicted value of . The last result is presented in Figure 6, which corresponds to specimen No. 9 in Liu et al. [23] and to values of Foq = 6 × 10-3 and as = 0.35 in the theoretical model. The results are presented on an appropriately scaled vertical axis and show again a very good match between the theory presented in this article, and the experimental data as digitized from Liu et al. [23]. Since the volumetric solid fraction for this specimen was 0.2%, its corresponding Maxwell's [4] effective thermal conductivity for this specimen leads to a value of 0.6036 W/mK, which is higher by 0.6% than that of the base fluid (water), i.e. . The steady-state result for the ratio between the effective thermal conductivity and that of the base fluid was estimated from the digitized data to be validating again Maxwell's [4] predicted value.

Bottom Line: Theoretical results derived in this article are combined with experimental data to conclude that, while there is no improvement in the effective thermal conductivity of nanofluids beyond the Maxwell's effective medium theory (J.C.Maxwell, Treatise on Electricity and Magnetism, 1891), there is substantial heat transfer augmentation via nanofins.The latter are formed as attachments on the hot wire surface by yet an unknown mechanism, which could be related to electrophoresis, but there is no conclusive evidence yet to prove this proposed mechanism.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Mechanical Engineering, Northern Arizona University, P, O, Box 15600, Flagstaff, AZ 86011-5600, USA. peter.vadasz@nau.edu.

ABSTRACT
Theoretical results derived in this article are combined with experimental data to conclude that, while there is no improvement in the effective thermal conductivity of nanofluids beyond the Maxwell's effective medium theory (J.C. Maxwell, Treatise on Electricity and Magnetism, 1891), there is substantial heat transfer augmentation via nanofins. The latter are formed as attachments on the hot wire surface by yet an unknown mechanism, which could be related to electrophoresis, but there is no conclusive evidence yet to prove this proposed mechanism.

No MeSH data available.


Related in: MedlinePlus