I was trying to find out what would happen to Supercritical Water (3200psi/374C) if the pressure was suddenly reduced to 1 atm (14.7 psi). [EDIT: My actual plan is to reduce it to 2000psi]. My guess is that the water would immediately flash to steam. But I've had many people tell me that "what happens" depends entirely on HOW the Supercritical Water was made. Was it heated in a boiler to supercritical state, compressed mechanically to supercritical state, found on the moon, etc. Does anyone know definitively what the answer is?
If it started out at the initial state you identified in your first post (basically the critical point), and you passed it passed it through an adiabatic porous plug down to atmospheric pressure of 14.7 psia, the water would emerge at 100 C, and as a combination of about 25% liquid water and 75% water vapor (steam).