Evacuation of a liquid-vapor water mixture

[Est120]

TL;DR

evacuation of a liquid-vapor water mixture

suppose i have liquid and vapor water inside a vessel at say 3000kPa, then i suddenly open the valve, as the water (liquid) flows out the vessel (control volume) is water inside the cv evaporating at the same rate liquid flows out? so the volume of water inside the cv remains constant?

 

[Baluncore]

3000 kPa is the vapour pressure of water at that temperature.
The valve at the bottom drains liquid water only.
As the liquid is removed, the gas volume above rises.
Water must evaporate to maintain the partial pressure.