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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. Transient simulations: temperature evolution as predicted by NVE molecular dynamics. Best fitting of exponential decay of the temperature difference TCNT - Tw is achieved by choosing τd = 41 ps.
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Figure 9: Color online. Transient simulations: temperature evolution as predicted by NVE molecular dynamics. Best fitting of exponential decay of the temperature difference TCNT - Tw is achieved by choosing τd = 41 ps.

Mentions: The value of thermal boundary conductance between water and a SW-CNT has been assessed by transient simulations as well. Results by the latter methodology are denoted as αtr to distinguish them from the same quantities (αst ) in the above section. In this study, the nanotube was initially heated to a predetermined temperature Thot while water was kept at Tw < Thot (using in both cases Nosé-Hoover thermostatting for 0.6 ns). Next, an NVE MD (ensemble where number of particle N, system volume V and energy E are conserved) were performed, where the entire system (SWNT plus water) was allowed to relax without any temperature and pressure coupling. Under the assumption of a uniform temperature field TCNT (t) within the nanotube at any time instant t (i.e., Biot number Bi < 0.1), the above phenomenon can be modeled by an exponential decay of the temperature difference (TCNT - Tw ) in time, where the time constant τd depends on the nanotube heat capacity cT and the thermal heat conductance αtr at the nanotube-water interface as follows (see Figure 9):(22)


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

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

Color online. Transient simulations: temperature evolution as predicted by NVE molecular dynamics. Best fitting of exponential decay of the temperature difference TCNT - Tw is achieved by choosing τd = 41 ps.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 9: Color online. Transient simulations: temperature evolution as predicted by NVE molecular dynamics. Best fitting of exponential decay of the temperature difference TCNT - Tw is achieved by choosing τd = 41 ps.
Mentions: The value of thermal boundary conductance between water and a SW-CNT has been assessed by transient simulations as well. Results by the latter methodology are denoted as αtr to distinguish them from the same quantities (αst ) in the above section. In this study, the nanotube was initially heated to a predetermined temperature Thot while water was kept at Tw < Thot (using in both cases Nosé-Hoover thermostatting for 0.6 ns). Next, an NVE MD (ensemble where number of particle N, system volume V and energy E are conserved) were performed, where the entire system (SWNT plus water) was allowed to relax without any temperature and pressure coupling. Under the assumption of a uniform temperature field TCNT (t) within the nanotube at any time instant t (i.e., Biot number Bi < 0.1), the above phenomenon can be modeled by an exponential decay of the temperature difference (TCNT - Tw ) in time, where the time constant τd depends on the nanotube heat capacity cT and the thermal heat conductance αtr at the nanotube-water interface as follows (see Figure 9):(22)

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