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A new heat propagation velocity prevails over Brownian particle velocities in determining the thermal conductivities of nanofluids.

Kihm KD, Chon CH, Lee JS, Choi SU - Nanoscale Res Lett (2011)

Bottom Line: An alternative insight is presented concerning heat propagation velocity scales in predicting the effective thermal conductivities of nanofluids.The widely applied Brownian particle velocities in published literature are often found too slow to describe the relatively higher nanofluid conductivities.This novel model of effective thermal conductivities of nanofluids agrees well with an extended range of experimental data.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Mechanical, Aerospace, and Biomedical Engineering, University of Tennessee, Knoxville, Tennessee 37996, USA. kkihm@utk.edu.

ABSTRACT
An alternative insight is presented concerning heat propagation velocity scales in predicting the effective thermal conductivities of nanofluids. The widely applied Brownian particle velocities in published literature are often found too slow to describe the relatively higher nanofluid conductivities. In contrast, the present model proposes a faster heat transfer velocity at the same order as the speed of sound, rooted in a modified kinetic principle. In addition, this model accounts for both nanoparticle heat dissipation as well as coagulation effects. This novel model of effective thermal conductivities of nanofluids agrees well with an extended range of experimental data.

No MeSH data available.


Related in: MedlinePlus

Temperature dependence of Brownian velocities [26-28], speed of sound [43], phonon velocities [44,45], and the heat propagation velocity of the present model (Equation 5).
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Figure 1: Temperature dependence of Brownian velocities [26-28], speed of sound [43], phonon velocities [44,45], and the heat propagation velocity of the present model (Equation 5).

Mentions: Figure 1 compares different types of velocity scales that are considered relevant in describing nanofluid thermal conductivity models: (1) three differently defined Brownian velocities for 47-nm Al2O3 nanoparticles [26-28], (2) the Brownian velocity of the base fluid (water) molecules [26], (3) the heat propagation velocity based on the currently proposed model (Equation 5), (4) the sound velocity in water [43], and (5) phonon velocities for selected solid mediums of αalpha-Fe and silicons [44,45]. The phonon velocities are expected to be faster than the heat propagation velocity in liquid because of the relatively higher heat conductivities in solid mediums.


A new heat propagation velocity prevails over Brownian particle velocities in determining the thermal conductivities of nanofluids.

Kihm KD, Chon CH, Lee JS, Choi SU - Nanoscale Res Lett (2011)

Temperature dependence of Brownian velocities [26-28], speed of sound [43], phonon velocities [44,45], and the heat propagation velocity of the present model (Equation 5).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211451&req=5

Figure 1: Temperature dependence of Brownian velocities [26-28], speed of sound [43], phonon velocities [44,45], and the heat propagation velocity of the present model (Equation 5).
Mentions: Figure 1 compares different types of velocity scales that are considered relevant in describing nanofluid thermal conductivity models: (1) three differently defined Brownian velocities for 47-nm Al2O3 nanoparticles [26-28], (2) the Brownian velocity of the base fluid (water) molecules [26], (3) the heat propagation velocity based on the currently proposed model (Equation 5), (4) the sound velocity in water [43], and (5) phonon velocities for selected solid mediums of αalpha-Fe and silicons [44,45]. The phonon velocities are expected to be faster than the heat propagation velocity in liquid because of the relatively higher heat conductivities in solid mediums.

Bottom Line: An alternative insight is presented concerning heat propagation velocity scales in predicting the effective thermal conductivities of nanofluids.The widely applied Brownian particle velocities in published literature are often found too slow to describe the relatively higher nanofluid conductivities.This novel model of effective thermal conductivities of nanofluids agrees well with an extended range of experimental data.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Mechanical, Aerospace, and Biomedical Engineering, University of Tennessee, Knoxville, Tennessee 37996, USA. kkihm@utk.edu.

ABSTRACT
An alternative insight is presented concerning heat propagation velocity scales in predicting the effective thermal conductivities of nanofluids. The widely applied Brownian particle velocities in published literature are often found too slow to describe the relatively higher nanofluid conductivities. In contrast, the present model proposes a faster heat transfer velocity at the same order as the speed of sound, rooted in a modified kinetic principle. In addition, this model accounts for both nanoparticle heat dissipation as well as coagulation effects. This novel model of effective thermal conductivities of nanofluids agrees well with an extended range of experimental data.

No MeSH data available.


Related in: MedlinePlus