Suppose I put water in a closed vessel and heat it, so the vessel becomes pressurized above ambient pressure. Now, there should be liquid and gaseous water inside the vessel. Since it's under pressure, when I open the vessel at the bottom, the liquid starts to flow out. If I wait until all liquid is expelled, and close the opening before the water vapor exits too, what state do I have in the vessel? Specifically:
- Releasing pressure from a system usually means it cools down. What does that mean for the vessel's inside? If I want the vessel to stay at the temperature it was, do I have to reheat (if we ignore ordinary heat dissipation for now)?
- The pressure inside the vessel now is lower, does that mean water vapor will condense and the system moves toward a new equilibrium? If I keep the temperature constant, will it be the same pressure as before?
- Does it matter for this question to what extent the vessel is filled at the beginning? If I understood vapor pressure correctly, the contents will reach an equilibrium of liquid and gaseous such that the pressure reaches a point which is solely dependent on temperature.
- Does it matter for the purpose of this question how quickly I expel the liquid phase?
- I'm not sure what influence the ambient pressure has on this question.
If you need sample values, assume 100 kPa (i. e., normal atmosphere) for the ambient pressure, 200 °C for the water and 1.555 MPa inside the vessel when I open the valve.