Why and how ? Vacuum is maintained in Condensers in Power Plants?

As we all know that the Pressurized steam is passed through High Pressure Turbine, Intermediate Turbine and Low Pressure Turbine. In each stage, Pressure is dropped. At last stage the Pressure is very low as steam has done all the work and lost most of the energy in doing this work.

Now since we have utilized the energy of the steam, what we can do further?

Answer is get our water back, so that we can reuse it, but heating it, pressurizing it and converting it back to High Pressure steam. Makes sense?

So we need to condense this Low Pressure steam into water. For this we have the Condenser below the Low Pressure Turbine.

Now two questions:

1.       Since the steam has lost the pressure, how it will flow from Low Pressure Turbine to Condenser?

2.       When the water will be condensed, it will take less space than the steam (simple concept, right?)?

So how these two things can be done?

Of course, by lowering the pressure in condenser of you can say by creating a vacuum (Pressure below the atmospheric pressure).

If a pressure below the atmospheric pressure can be created in Condenser, the Low pressure steam from the LP turbine will flow into it.

Now the Steam will be condensed (How, doesn’t matter for time being). But the water will take less space than the steam entered. Since condenser is air tight, a vacuum will be created for the space created by converting the water into steam so that more water can be accommodated.

So, to summarize: Remember what happens in a condenser? Energy is lost from the fluid stream. The fluid changes from a gas to a liquid (condenses). Since liquids take up less volume as the same mass of a gas at when the phase changes a vacuum must be created which will draw in more gas to be cooled