  Intense heat-mass transfer in a gas flow to a condensation surface is studied
with the consistent atomistic and kinetic theory methods. The simple moment
method is utilized for solving the Boltzmann kinetic equation (BKE) for the
nonequilibrium gas flow and its condensation, while molecular dynamics (MD)
simulation of a similar flow is used for verification of BKE results. We
demonstrate that BKE can provide the steady flow profiles close to those
obtained from MD simulations in both subsonic and supersonic regimes of steady
gas flows. Surprisingly, the elementary theory of condensation is shown with
BKE results to have a good accuracy in a wide range of gas flow parameters.
  MD confirms that a steady supersonic gas flow condensates on a surface at the
distinctive temperature after formation of a standing shock front in reference
to this surface, which can be interpreted as a permeable condensating piston.
The last produces the shock compression but completely absorbs incoming gas
flow in contrast to a common impermeable piston. The shock front divides the
vapor flow on the supersonic and subsonic zones, and condensation of compressed
gas happens in the subsonic regime. The complete and partial condensation
regimes are discussed. It is shown that above the certain surface temperatures
determined by the shock Hugoniot the runaway shock front stops an inflow gas
and condensation is ceased.
