What happens when heating water in a pressure vessel? Suppose that I take a pressure vessel that can withstand up to 2000 PSI. Now I fill it with water (not completely, but around 90%) and start to heat it with a direct flame. What I want to know is, what will happen?

Although I don't know anything about it, here are some guesses that I think might happen:


The water will begin to convert into gas. But since the volume is limited, therefore the pressure would increase (and keep on increasing) and the vessel may burst after the internal pressure crosses 2000PSI.
The water won't convert into gas and would just take all the heat energy into itself. In other words, nothing would happen.


Those are my guesses and it would be great if you can help me out.
Look at the phase diagram of water to see what happens. Josiah Willard Gibbs invented these diagrams o help understand what happens as a substance is heated under pressure, and transitions from solid to liquid to gas and supercritical fluid (neither quite gas nor liquid).

Given sufficient heat, the vessel will burst. Above ~650 K, the water can no longer be liquefied by pressure, and behaves more like an ideal gas, so pressure continues to increase.