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Nanotubes in liquids: Effective thermal conductivity
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10.1063/1.2360147
/content/aip/journal/jap/100/8/10.1063/1.2360147
http://aip.metastore.ingenta.com/content/aip/journal/jap/100/8/10.1063/1.2360147

Figures

Image of FIG. 1.
FIG. 1.

Data of the thermal conductivity of carbon nanotubes in oil, see Refs. 1 and 2. The standard models in (a) of mixtures of nanotubes in liquids show very little increase and vastly underestimate the data as shown. Models by Nan et al. in (b) significantly overestimate the data when the correct thermal conductivities are used.

Image of FIG. 2.
FIG. 2.

Models from Chen et al. (Ref. 11) along with data, see Ref. 1. These models do not capture the magnitude or the shape of the experimental data.

Image of FIG. 3.
FIG. 3.

The sphere swept out by a nanotube rotating on its axis has a diameter equal to the length of the nanotube.

Image of FIG. 4.
FIG. 4.

Nanotubes shown on square and hexagonal lattices and a cylindrical approximation. The surface-to-surface spacing for the nearest neighbors is denoted by , and for next nearest neighbors.

Image of FIG. 5.
FIG. 5.

Surface-to-surface spacing for cylindrical nanotubes on square and hexagonal lattices and a cylindrical approximation as a function of volume fraction. The aspect ratio used is 2000.

Image of FIG. 6.
FIG. 6.

Schematic of parallel and series conductivities between plates kept at temperatures and with conductivities for the fluid and the nanotube .

Image of FIG. 7.
FIG. 7.

Pure series (a) and pure parallel (b) thermal conductivity models graphed with data for carbon nanotubes in oil. The series model underestimates and the parallel model overestimates the measured data.

Image of FIG. 8.
FIG. 8.

The composite can be broken into regions parallel to the direction of the thermal gradient. There are layers containing pure liquid in parallel with layers with both nanotubes and liquid.

Image of FIG. 9.
FIG. 9.

The normalized effective thermal conductivity along different directions as a function of volume fraction, plotted with data, see Ref. 1. The aspect ratio is 2000, the liquid thermal conductivity is , the nanotube thermal conductivity is , and there is no boundary resistance. Even if magnified as in the insert, all the nearest and next nearest neighbor models overlap and show very little increase in thermal conductivity.

Image of FIG. 10.
FIG. 10.

Interface resistance changes the model results only slightly. The calculations with and without resistance overlap one another. The nanotube diameter used was and the value for was , the largest reported in the literature. Other parameter values used are the same as in Fig. 9.

Image of FIG. 11.
FIG. 11.

The orientation average thermal conductivity, normalized by the thermal conductivity of the liquid, shown for both the square and hexagonal lattice approximations.

Image of FIG. 12.
FIG. 12.

Data for three different liquids, see Ref. 2, compared with the orientation average model, showing that the model (square lattice) overestimates the thermal conductivity by a large margin for all three liquids.

Image of FIG. 13.
FIG. 13.

Data, see Ref. 2, compared with the orientation model using an aspect ratio of 200, much lower than the reported value of 2000.

Image of FIG. 14.
FIG. 14.

Data, see Ref. 2, with orientation average model using a carbon nanotube thermal conductivity of , the value for graphite perpendicular to the basal plane.

Image of FIG. 15.
FIG. 15.

Data, see Ref. 2, with orientation average model using a carbon nanotube thermal conductivity of , the value for graphite perpendicular to the basal plane, and no interface thermal resistance. This lower bound on the interface resistance shows a slightly better fit with the data.

Tables

Generic image for table
Table I.

Effective volume fractions.

Generic image for table
Table II.

.

Generic image for table
Table III.

Experimental Parameters.

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/content/aip/journal/jap/100/8/10.1063/1.2360147
2006-10-31
2014-04-23
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Nanotubes in liquids: Effective thermal conductivity
http://aip.metastore.ingenta.com/content/aip/journal/jap/100/8/10.1063/1.2360147
10.1063/1.2360147
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