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Enhancing surface heat transfer by carbon nanofins: towards an alternative to nanofluids?

Chiavazzo E, Asinari P - Nanoscale Res Lett (2011)

Bottom Line: Nanofluids are suspensions of nanoparticles and fibers which have recently attracted much attention because of their superior thermal properties.As a result, particles are only needed in a small region of the fluid, while dispersion can be controlled in advance through design and manufacturing processes.Numerical evidences suggest a pretty favorable thermal boundary conductance (order of 107 W·m-2·K-1) which makes carbon nanotubes potential candidates for constructing nanofinned surfaces.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Energetics, Politecnico di Torino, Corso Duca degli Abruzzi, 10129 Torino, Italy. pietro.asinari@polito.it.

ABSTRACT

Background: Nanofluids are suspensions of nanoparticles and fibers which have recently attracted much attention because of their superior thermal properties. Nevertheless, it was proven that, due to modest dispersion of nanoparticles, such high expectations often remain unmet. In this article, by introducing the notion of nanofin, a possible solution is envisioned, where nanostructures with high aspect-ratio are sparsely attached to a solid surface (to avoid a significant disturbance on the fluid dynamic structures), and act as efficient thermal bridges within the boundary layer. As a result, particles are only needed in a small region of the fluid, while dispersion can be controlled in advance through design and manufacturing processes.

Results: Toward the end of implementing the above idea, we focus on single carbon nanotubes to enhance heat transfer between a surface and a fluid in contact with it. First, we investigate the thermal conductivity of the latter nanostructures by means of classical non-equilibrium molecular dynamics simulations. Next, thermal conductance at the interface between a single wall carbon nanotube (nanofin) and water molecules is assessed by means of both steady-state and transient numerical experiments.

Conclusions: Numerical evidences suggest a pretty favorable thermal boundary conductance (order of 107 W·m-2·K-1) which makes carbon nanotubes potential candidates for constructing nanofinned surfaces.

No MeSH data available.


Related in: MedlinePlus

Color online. Pictorial representation of a single nanofin: end-points are maintained at fixed temperature by Nosé-Hoover thermostats. During numerical experiments for evaluating thermal conductivity, simulations are conducted in a vacuum. On the contrary, thermal boundary conductances are evaluated with the nanofin surrounded by a fluid. The latter setup can be studied by a one-dimensional continuous model, where all fields are assumed to vary only along the x-axis.
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Figure 7: Color online. Pictorial representation of a single nanofin: end-points are maintained at fixed temperature by Nosé-Hoover thermostats. During numerical experiments for evaluating thermal conductivity, simulations are conducted in a vacuum. On the contrary, thermal boundary conductances are evaluated with the nanofin surrounded by a fluid. The latter setup can be studied by a one-dimensional continuous model, where all fields are assumed to vary only along the x-axis.

Mentions: We notice that, the latter is a classical problem of heat transfer (pictorially shown in Figure 7), where a single fin (heated at the ends) is immersed in a fluid maintained at a fixed temperature. This system can be conveniently treated using a continuous approach under the assumptions of homogeneous material, constant cross section S, and one-dimensionality (no temperature gradients within a given cross section) [44]. In this case, both temperature field and heat flux only depend on the spatial coordinate x, and the analytic solution of the energy conservation equation yields, at the steady state, the following relationship:(14)


Enhancing surface heat transfer by carbon nanofins: towards an alternative to nanofluids?

Chiavazzo E, Asinari P - Nanoscale Res Lett (2011)

Color online. Pictorial representation of a single nanofin: end-points are maintained at fixed temperature by Nosé-Hoover thermostats. During numerical experiments for evaluating thermal conductivity, simulations are conducted in a vacuum. On the contrary, thermal boundary conductances are evaluated with the nanofin surrounded by a fluid. The latter setup can be studied by a one-dimensional continuous model, where all fields are assumed to vary only along the x-axis.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211310&req=5

Figure 7: Color online. Pictorial representation of a single nanofin: end-points are maintained at fixed temperature by Nosé-Hoover thermostats. During numerical experiments for evaluating thermal conductivity, simulations are conducted in a vacuum. On the contrary, thermal boundary conductances are evaluated with the nanofin surrounded by a fluid. The latter setup can be studied by a one-dimensional continuous model, where all fields are assumed to vary only along the x-axis.
Mentions: We notice that, the latter is a classical problem of heat transfer (pictorially shown in Figure 7), where a single fin (heated at the ends) is immersed in a fluid maintained at a fixed temperature. This system can be conveniently treated using a continuous approach under the assumptions of homogeneous material, constant cross section S, and one-dimensionality (no temperature gradients within a given cross section) [44]. In this case, both temperature field and heat flux only depend on the spatial coordinate x, and the analytic solution of the energy conservation equation yields, at the steady state, the following relationship:(14)

Bottom Line: Nanofluids are suspensions of nanoparticles and fibers which have recently attracted much attention because of their superior thermal properties.As a result, particles are only needed in a small region of the fluid, while dispersion can be controlled in advance through design and manufacturing processes.Numerical evidences suggest a pretty favorable thermal boundary conductance (order of 107 W·m-2·K-1) which makes carbon nanotubes potential candidates for constructing nanofinned surfaces.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Energetics, Politecnico di Torino, Corso Duca degli Abruzzi, 10129 Torino, Italy. pietro.asinari@polito.it.

ABSTRACT

Background: Nanofluids are suspensions of nanoparticles and fibers which have recently attracted much attention because of their superior thermal properties. Nevertheless, it was proven that, due to modest dispersion of nanoparticles, such high expectations often remain unmet. In this article, by introducing the notion of nanofin, a possible solution is envisioned, where nanostructures with high aspect-ratio are sparsely attached to a solid surface (to avoid a significant disturbance on the fluid dynamic structures), and act as efficient thermal bridges within the boundary layer. As a result, particles are only needed in a small region of the fluid, while dispersion can be controlled in advance through design and manufacturing processes.

Results: Toward the end of implementing the above idea, we focus on single carbon nanotubes to enhance heat transfer between a surface and a fluid in contact with it. First, we investigate the thermal conductivity of the latter nanostructures by means of classical non-equilibrium molecular dynamics simulations. Next, thermal conductance at the interface between a single wall carbon nanotube (nanofin) and water molecules is assessed by means of both steady-state and transient numerical experiments.

Conclusions: Numerical evidences suggest a pretty favorable thermal boundary conductance (order of 107 W·m-2·K-1) which makes carbon nanotubes potential candidates for constructing nanofinned surfaces.

No MeSH data available.


Related in: MedlinePlus