  With a view to optimising the design of carbon-nanotube (CNT) windmills and
to maximising the internal magnetic field generated by chiral currents, we
present analytical results for the group velocity components of an electron
flux through chiral carbon nanotubes. Chiral currents are shown to exhibit a
rich behaviour and can even change sign and oscillate as the energy of the
electrons is increased. We find that the transverse velocity and associated
angular momentum of electrons is a maximum for non-metallic CNTs with a chiral
angle of 18$^o$. Such CNTs are therefore the optimal choice for CNT windmills
and also generate the largest internal magnetic field for a given longitudinal
current. For a longitudinal current of order $10^{-4}$ amps, this field can be
of order $10^{-1}$Teslas, which is sufficient to produce interesting spintronic
effects and a significant contribution to the self inductance.
