The direct air cooling system is a steam exhausted from a steam turbine. The pipeline is introduced into a steel radiator called an air condenser. The ambient air directly cools it into condensed water, which reduces the intermediate required for conventional secondary heat exchange. The cooling medium has a large heat exchange temperature difference and the effect is good. In addition to this, other main features are:
The turbine back pressure has a large amplitude. Turbine exhaust is directly condensed by air, and its back pressure changes with the temperature of the air. The temperature difference between the four seasons and even the day and night in northern China is relatively large, so the turbine is required to have a wide back pressure operating range.
The vacuum system is huge. The steam exhaust of the steam turbine should be led out by a large-diameter pipe. The surface heat is exchanged by the steel radiator with air as the direct cooling medium. The condensing and exhausting requires a large cooling area, which leads to the huge vacuum system.
High energy consumption. The air required for the direct air cooling system is provided by a large diameter fan (there is also a natural ventilation scheme for cooling towers, but there is no practice). The fan needs energy consumption. According to foreign data, the direct air cooling system consumes 1.5 of the generating capacity of the unit. %about.