  Observations reveal a correspondence between chromospheric type II spicules
and bright upwardly moving fronts in the corona observed in the EUV band.
However, theoretical considerations suggest that these flows are unlikely to be
the main source of heating in coronal magnetic loops. We investigate the
propagation of high-speed chromospheric flows into coronal magnetic flux tubes,
and the possible production of emission in the EUV band. We simulate the
propagation of a dense $10^4$ K chromospheric jet upwards along a coronal loop,
by means of a 2-D cylindrical MHD model, including gravity, radiative losses,
thermal conduction and magnetic induction. The jet propagates in a complete
atmosphere including the chromosphere and a tenuous cool ($\sim 0.8$ MK)
corona, linked through a steep transition region. In our reference model, the
jet's initial speed is 70 km/s, its initial density is $10^{11}$ cm$^{-3}$, and
the ambient uniform magnetic field is 10 G. We explore also other values of jet
speed and density in 1-D, and of magnetic field in 2-D, and the jet propagation
in a hotter ($\sim 1.5$ MK) background loop. While the initial speed of the jet
does not allow it to reach the loop apex, a hot shock front develops ahead of
it and travels to the other extreme of the loop. The shock front compresses the
coronal plasma and heats it to about $10^6$ K. As a result, a bright moving
front becomes visible in the 171 \AA\ channel of the SDO/AIA mission. This
result generally applies to all the other explored cases, except for the
propagation in the hotter loop. For a cool, low-density initial coronal loop,
the post-shock plasma ahead of upward chromospheric flows might explain at
least part of the observed correspondence between type II spicules and EUV
emission excess.
