In order to maximize the efficiency of the steam turbine, the pressure and temperature of the outlet steam must be as low as possible. For this purpose steam which leaves the low-pressure turbine is routed to the condenser where it is cooled and becomes water. The condensate can then be immediately reused as feed water. Feed water pumps return it to the steam generator where the new water-steam cycle is renewed: it is a closed circuit.


Cooling in a closed circuit

The condenser is a heat exchanger with thousands of tubes through which cooling water flows from the tertiary cooling circuit. The steam flows over the tubes and condenses when it comes into contact with them. The water from the tertiary circuit then removes the heat contained.

The water needed for this cooling process is taken from the heat sink (river, ...).

Cooling towers enable cooling to be performed in a virtually closed circuit. Most of the cooling water is reused for a new cooling process.

How does a cooling tower work

The cooling water absorbs heat in the condenser and is pumped to the cooling towers where the water is spread over a horizontal grid, it pours down in a shower. Due to contact with an upward airflow (natural draught chimney effect), it cools off. A small fraction of the cooling water (1.5%) evaporates and escapes as a vapour plume above the tower. A minor part of the cold cooling water flows back into the river. The majority is collected in a pool at the base of the tower and - now cooled - is mixed with fresh water from the river and once more routed to the condenser.