The
displacement characteristics of gas–liquid systems in
capillary media under nonisothermal and nonisobaric conditions are
controlled by capillarity as phase alteration (specifically vaporization)
starts earlier in smaller (nano)capillaries compared to the larger
ones. For an accurate modeling of these types of natural and engineered
processes, this thermodynamically dictated displacement process should
be well understood. With this aim, the capillarity effect on phase
change and the displacement dynamics of hydrocarbon liquids in homogeneous
and heterogenous silicate microfluidics chips was studied. It was
observed that the boiling temperatures of pentane, a pentane–heptane
mixture, and a pentane–heptane–octane mixture were 1.6–6.9%
lower than bulk measurements due to confinement effects, and the early
vaporization had a significant influence on the vapor displacement
process. In homogeneous (uniform capillary pressure distribution)
porous media, the consistency of capillary pressure resulted in a
uniform and quicker propagation/displacement of vapor. However, in
the media with variable capillary pressure (heterogeneous pore structure),
the vapor’s flow tended to take place nonuniformly along the
system, thus leading to a major gas fingering and gas-flow restriction.
The presence of otherheaviercomponents (liquid phase)
in the porous medium developed an excessive barrier against the vapor’s
flow throughout the pore channels that was specifically caused by
the viscous forces of the liquids. Moreover, it was observed that
the existence of liquids with high boiling points contribute to slowing
the vapor propagation of the lighter components, and the gas displacement
becomes slower as the density and viscosity of the liquid-phase components
increases.