I am asking about mixing 2 fluids (water & steam ) in the same place while making a flow simulation study.In pressurized water reactor a pressurizer is used for controlling the pressure of water in the primary loop.This pressurizer is filled with water to a certain level and the rest is steam. There are heaters in the lower botom of the pressurizer and spray nozzle in the upper head of it.these heaters and spray nozzle are used to mantain the pressure at a constant value, for example

If the pressurizer pressure increases to above the desired pressure, the spray valves open adding cool water (relatively) from the reactor cooling system cold legs into ,the steam space via a spray nozzle the cooler water condenses some of the steam, and lowers the pressure

when pressure is restored to below the desired pressure, the spray valves will close again.The problem now, i want to see the change in the level of water and steam (as a vedio ) if the spray nozzle is opened or the heater is in operation for a certain time.