Maximum thermal conductivity of aligned single wall carbon nanotubes
  I estimate maximum thermal conductivity $\kappa$ of a perfectly aligned bundle of single wall carbon nanotubes. Each row of aligned nanotubes has a discrete structure. It consists of segments of nanotubes with length $L$. The spacing between the segments block the phonon path through the row. Only the scattering due to the finite length of the segments is taken into account. The result is that the 'effective'' mean free path is of the order of $L/7$. For 1 micron tubes (10,10) we get maximum value of $\kappa\approx 300$W/m K at room temperature. This result is in a reasonable agreement with the experiment by Hone {\it et al.} assuming that in their samples $L\approx 1\mu{\rm m}$ 
A.L. Efros