18 research outputs found
Heat conduction in graphene flakes with inhomogeneous mass interface
Using nonequilibrium molecular dynamics simulations, we study the heat
conduction in graphene flakes composed by two regions. One region is
mass-loaded and the other one is intact. It is found that the mass interface
between the two regions greatly decreases the thermal conductivity, but it
would not bring thermal rectification effect. The dependence of thermal
conductivity upon the heat flux and the mass difference ratio are studied to
confirm the generality of the result. The interfacial scattering of solitons is
studied to explain the absence of rectification effect.Comment: 5 pages, 4 figure
Thermal rectification in asymmetric U-shaped graphene flakes
In this paper, we study the thermal rectification in asymmetric U-shaped
graphene flakes by using nonequilibrium molecular dynamics simulations. The
graphene flakes are composed by a beam and two arms. It is found that the heat
flux runs preferentially from the wide arm to the narrow arm which indicates a
strong rectification effect. The dependence of the rectification ratio upon the
heat flux, the length and the width of the beam, the length and width of the
two arms are studied. The result suggests a possible route to manage heat
dissipation in U-shaped graphene based nanoelectronic devices.Comment: 3 pages, 4 figure
Enhancing surface heat transfer by carbon nanofins: towards an alternative to nanofluids?
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 surface
Low thermal conductivity of peanut-shaped carbon nanotube and its insensitive response to uniaxial strain
Maximal rectification ratios for idealized bi-segment thermal rectifiers
Thermal rectifiers whose forward heat fluxes are greater than reverse counterparts have been extensively studied. Here we have discovered, idealized, and derived the ultimate limit of such rectification ratios, which are partially validated by numerical simulations, experiments, and micro-scale Hamiltonian-oscillator analyses. For rectifiers whose thermal conductivities (κ) are linear with the temperature, this limit is simply a numerical value of 3. For those whose conductivities are nonlinear with temperatures, the maxima equal κ(max)/κ(min), where two extremes denote values of the solid segment materials that can be possibly found or fabricated within a reasonable temperature range. Recommendations for manufacturing high-ratio rectifiers are also given with examples. Under idealized assumptions, these proposed rectification limits cannot be defied by any bi-segment thermal rectifiers