The correct answer is C because flashing of liquids is fundamentally an energy-driven thermodynamic process , as described in CCPS consequence analysis and dispersion modeling guidance. When a pressurized liquid is suddenly released to a lower pressure, a portion of the liquid rapidly vaporizes (flashes). The energy required for this phase change comes from the internal energy (enthalpy) of the liquid itself , not from an external heat source.
As the liquid flashes, it cools because energy is consumed in vaporization. The fraction that flashes depends on factors such as initial temperature, pressure, heat capacity, and latent heat of vaporization—not fixed percentages.
Option A and B are incorrect because the fraction flashed is not constant ; it can vary widely depending on thermodynamic conditions.
Option D is incorrect because flashing is actually more likely when a liquid is above its normal boiling point under pressure . When pressure is suddenly reduced, the liquid is in a superheated state and can rapidly flash.
CCPS emphasizes understanding flashing behavior in hazard analysis because it significantly affects release rates, vapor cloud formation, and potential consequences such as toxic exposure or vapor cloud explosions.
