  Pecularities of isentropic expansion of warm dense matter (WDM) created by
intense energy fluxes are under discussion in situation when thermodynamic
trajectory of such expansion crosses binodal of liquid-gas phase transition and
expansion within two-phase region is going along equilibrium branch of the
isentrope for two-phase mixture . It is known for the case of plane geometry
(Anisimov, Inogamov et al. 1999) that because of sharp break of the expansion
isoentrope at boiling point there appears extended zone (liquid layer) of
uniformity for expanding material with constant thermodynamic and kinematic
parameters, which corresponds to the state on binodal. General properties of
such boiling (binodal) layer were claimed and discussed before for the cases of
isentropic expansion of infinite sample as well as for finite plane and
spherical samples (slab and ball) and for the system of well positioned slabs
(stuck target). Thermodynamic and kinematic parameters of discussed binodal
layer are studied in present paper with the use of simplest Van der Waals
equation of state (EOS). Advantage of VdW-EOS is possibility of demonstrable
and semi-analytical description of thermo- and hydrodynamics of the process.
Current work studies phenomenon in planar case of isentropic expansion of
finite sized layer (slab) of VdW-matter.
