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Experimental and theoretical studies of nanofluid thermal conductivity enhancement: a review.

Kleinstreuer C, Feng Y - Nanoscale Res Lett (2011)

Bottom Line: Such outcomes would validate new, minimally intrusive techniques and verify the reproducibility of experimental results.Dynamic knf models, assuming non-interacting metallic nano-spheres, postulate an enhancement above the classical Maxwell theory and thereby provide potentially additional physical insight.Clearly, it will be necessary to consider not only one possible mechanism but combine several mechanisms and compare predictive results to new benchmark experimental data sets.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Mechanical and Aerospace Engineering, NC State University, Raleigh, NC 27695-7910, USA. ck@eos.ncsu.edu.

ABSTRACT
Nanofluids, i.e., well-dispersed (metallic) nanoparticles at low- volume fractions in liquids, may enhance the mixture's thermal conductivity, knf, over the base-fluid values. Thus, they are potentially useful for advanced cooling of micro-systems. Focusing mainly on dilute suspensions of well-dispersed spherical nanoparticles in water or ethylene glycol, recent experimental observations, associated measurement techniques, and new theories as well as useful correlations have been reviewed.It is evident that key questions still linger concerning the best nanoparticle-and-liquid pairing and conditioning, reliable measurements of achievable knf values, and easy-to-use, physically sound computer models which fully describe the particle dynamics and heat transfer of nanofluids. At present, experimental data and measurement methods are lacking consistency. In fact, debates on whether the anomalous enhancement is real or not endure, as well as discussions on what are repeatable correlations between knf and temperature, nanoparticle size/shape, and aggregation state. Clearly, benchmark experiments are needed, using the same nanofluids subject to different measurement methods. Such outcomes would validate new, minimally intrusive techniques and verify the reproducibility of experimental results. Dynamic knf models, assuming non-interacting metallic nano-spheres, postulate an enhancement above the classical Maxwell theory and thereby provide potentially additional physical insight. Clearly, it will be necessary to consider not only one possible mechanism but combine several mechanisms and compare predictive results to new benchmark experimental data sets.

No MeSH data available.


Related in: MedlinePlus

Comparisons between Prasher's model [81], the F-K model [86], and benchmark experimental data [16,44,57].
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Figure 4: Comparisons between Prasher's model [81], the F-K model [86], and benchmark experimental data [16,44,57].

Mentions: Here, Re is defined by Eq. 7a, α = 2Rbkm/dp is the nanoparticle Biot number, and Rb = 0.77 × 10-8 Km2/W for water-based nanofluids which is the so-called thermal interface resistance, while A and m are empirical constants. As mentioned by Li [82] and Kleinstreuer and Li [80], the MSB model fails to predict the thermal conductivity enhancement trend when the particle are too small or too large. Also, because of the need for curve-fitting parameters A and m, Prasher's model lacks generality (Figure 4).


Experimental and theoretical studies of nanofluid thermal conductivity enhancement: a review.

Kleinstreuer C, Feng Y - Nanoscale Res Lett (2011)

Comparisons between Prasher's model [81], the F-K model [86], and benchmark experimental data [16,44,57].
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211287&req=5

Figure 4: Comparisons between Prasher's model [81], the F-K model [86], and benchmark experimental data [16,44,57].
Mentions: Here, Re is defined by Eq. 7a, α = 2Rbkm/dp is the nanoparticle Biot number, and Rb = 0.77 × 10-8 Km2/W for water-based nanofluids which is the so-called thermal interface resistance, while A and m are empirical constants. As mentioned by Li [82] and Kleinstreuer and Li [80], the MSB model fails to predict the thermal conductivity enhancement trend when the particle are too small or too large. Also, because of the need for curve-fitting parameters A and m, Prasher's model lacks generality (Figure 4).

Bottom Line: Such outcomes would validate new, minimally intrusive techniques and verify the reproducibility of experimental results.Dynamic knf models, assuming non-interacting metallic nano-spheres, postulate an enhancement above the classical Maxwell theory and thereby provide potentially additional physical insight.Clearly, it will be necessary to consider not only one possible mechanism but combine several mechanisms and compare predictive results to new benchmark experimental data sets.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Mechanical and Aerospace Engineering, NC State University, Raleigh, NC 27695-7910, USA. ck@eos.ncsu.edu.

ABSTRACT
Nanofluids, i.e., well-dispersed (metallic) nanoparticles at low- volume fractions in liquids, may enhance the mixture's thermal conductivity, knf, over the base-fluid values. Thus, they are potentially useful for advanced cooling of micro-systems. Focusing mainly on dilute suspensions of well-dispersed spherical nanoparticles in water or ethylene glycol, recent experimental observations, associated measurement techniques, and new theories as well as useful correlations have been reviewed.It is evident that key questions still linger concerning the best nanoparticle-and-liquid pairing and conditioning, reliable measurements of achievable knf values, and easy-to-use, physically sound computer models which fully describe the particle dynamics and heat transfer of nanofluids. At present, experimental data and measurement methods are lacking consistency. In fact, debates on whether the anomalous enhancement is real or not endure, as well as discussions on what are repeatable correlations between knf and temperature, nanoparticle size/shape, and aggregation state. Clearly, benchmark experiments are needed, using the same nanofluids subject to different measurement methods. Such outcomes would validate new, minimally intrusive techniques and verify the reproducibility of experimental results. Dynamic knf models, assuming non-interacting metallic nano-spheres, postulate an enhancement above the classical Maxwell theory and thereby provide potentially additional physical insight. Clearly, it will be necessary to consider not only one possible mechanism but combine several mechanisms and compare predictive results to new benchmark experimental data sets.

No MeSH data available.


Related in: MedlinePlus