Direct Air Cooling System
Direct air cooling system is to distribute the waste steam exhausted by the steam turbine directly to the steam condensers in different row and unit through pipes, while the large axial-flow fan intakes air and sweeps over the tube bundle externally to carry away the heat, waste steam is condensed into water in the tube bundle and is collected in the condensate tank through the header under the tube bundle.
The evacuation system ensures the whole air cooling system is in a vacuum, which guarantees the normal operation of the steam turbine and the efficiency of the electric generation. The steam condenser is divided into parallel flow and counter flow tube bundle, most of the steam is condensed in parallel flow tube bundle, while the non-condensing gas is extracted in counter flow tube bundle, the parallel flow and counter flow tube bundle are connected through the condensate tank at the bottom. Direct air-cooled condenser has the advantages of less floor area occupation, numerous anti-freeze means and flexible arrangement manner.
Indirect Dry Cooling System
In thermal power plant, the steam turbine uses pressurized hot steam from boiler to drive the generator. The waste steam exhausted from the rear end of the steam turbine flows into the air cooled condenser for the first heat exchange process. The waste steam, after transfering heat with the cooling water and condenses into water which returns to the boiler by feed pump, to start the next thermodynamical process. Then the condensate is purged by water pump to the boiler, and start the next thermodynamically cycle.
The cooling water is heated in condenser, and enters into the indirect air-cooled radiator by circulation water pump for seconf heat exchange process. The cooling water exchanges heat with cooling air from finned tubes of the natural draught cooling tower. After the heat exhange, the cooling water decreases in temperature, and then returns to condenser for the next thermodynamically cycle.
The cooling water is heated in condenser, and enters into the indirect air-cooled radiator by circulation water pump to exchange heat with cooling air from finned tubes under the natural draught of cooling tower. This is second heat exchange. The cooling water transfers heat to air and decrease temperature, and then returns to condenser to start the next thermodynamically cycle.