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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. Steady-state MD simulations. Dimensionless temperature computed by MD (symbols) versus temperature profile predicted by continuous model (line), Equation (17). Best fitting is achieved by choosing mL/2 = 0.28. Case with computational box 2.5 × 2.5 × 14 nm3.
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Figure 8: Color online. Steady-state MD simulations. Dimensionless temperature computed by MD (symbols) versus temperature profile predicted by continuous model (line), Equation (17). Best fitting is achieved by choosing mL/2 = 0.28. Case with computational box 2.5 × 2.5 × 14 nm3.

Mentions: In the setup illustrated in Figures 7 and 6, periodic boundary conditions are applied in the x, y, and z directions, and all the simulations are carried out with a fixed time step dt = 1 fs upon energy minimization. First of all, the whole system is led to thermal equilibrium at T = 300 by Nosé-Hoover thermostatting implemented for 0.8 ns with a relaxation time τT = 0.1 ns. Next, the simulation is continued for 15 ns where Nosé-Hoover temperature coupling is applied only at the tips of the nanofin (here, the outermost 16 carbon atom rings at each end) with Thot = 360 K, and in water with Tw = 300 K until, at the steady state, the temperature profile in Figure 8 is developed. Moreover, pressure is set to 1 bar by Parrinello-Rahman barostat during both thermal equilibration and subsequent non-equilibrium computation. We notice that the above MD results are in a good agreement with the continuous model for single fins if mL/2 = 0.28 (see also Figure 8). Hence, this enables us to estimate the thermal boundary conductance αst between SWNT and water with the help of Equation (15):(19)


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

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

Color online. Steady-state MD simulations. Dimensionless temperature computed by MD (symbols) versus temperature profile predicted by continuous model (line), Equation (17). Best fitting is achieved by choosing mL/2 = 0.28. Case with computational box 2.5 × 2.5 × 14 nm3.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 8: Color online. Steady-state MD simulations. Dimensionless temperature computed by MD (symbols) versus temperature profile predicted by continuous model (line), Equation (17). Best fitting is achieved by choosing mL/2 = 0.28. Case with computational box 2.5 × 2.5 × 14 nm3.
Mentions: In the setup illustrated in Figures 7 and 6, periodic boundary conditions are applied in the x, y, and z directions, and all the simulations are carried out with a fixed time step dt = 1 fs upon energy minimization. First of all, the whole system is led to thermal equilibrium at T = 300 by Nosé-Hoover thermostatting implemented for 0.8 ns with a relaxation time τT = 0.1 ns. Next, the simulation is continued for 15 ns where Nosé-Hoover temperature coupling is applied only at the tips of the nanofin (here, the outermost 16 carbon atom rings at each end) with Thot = 360 K, and in water with Tw = 300 K until, at the steady state, the temperature profile in Figure 8 is developed. Moreover, pressure is set to 1 bar by Parrinello-Rahman barostat during both thermal equilibration and subsequent non-equilibrium computation. We notice that the above MD results are in a good agreement with the continuous model for single fins if mL/2 = 0.28 (see also Figure 8). Hence, this enables us to estimate the thermal boundary conductance αst between SWNT and water with the help of Equation (15):(19)

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