I. Direct Air-Cooled Condenser System (Direct Air Cooling System)

Exhaust steam from the turbine is transported through large steam pipes to the finned tubes of the air-cooled heat exchanger. Cold air absorbs the heat released during the condensation of steam on the inner walls of the finned tubes in the power plant air-cooled system and directly dissipates the heat into the surrounding atmosphere. In this way, the low-pressure steam is condensed in the finned tubes, and under the action of gravity, this condensate flows into the condensate tank. Then, a pump draws it back into the power plant system from the condensate tank. Due to the different ventilation methods used on the air side, power plant air cooling systems are further divided into forced-draft direct air cooling systems and natural-draft direct air cooling systems.

The main characteristics of the direct air cooling system are:

1) High backpressure;

2) High power consumption due to forced ventilation fans;

3) High noise level from forced ventilation fans;

4) Smaller land occupation of the steel platform compared to reinforced concrete towers;

5) Approximately 30% higher efficiency and 30% smaller heat dissipation area compared to indirect cooling systems;

6) Relatively economical construction cost.

II. Indirect Air Cooling System

Due to the different condensers used in indirect air cooling systems, indirect air cooling systems are further divided into surface condenser indirect cooling systems and mixed condenser indirect cooling systems. Commonly used surface and jet condensers are usually installed directly below the turbine. The water heated by the turbine exhaust steam is pumped into the cooling tower, where it exchanges heat with the air flowing through the numerous finned tubes in the air-cooled heat exchanger and is cooled by the surrounding air before flowing back into the condenser. Because it does not require blowers, substances in the cooling water, or top water pumps, this system demonstrates its superiority in these aspects.

III. Wet Cooling System and Dry/Wet Cooling Hybrid System

The cooling circulation system of a power plant wet cooling unit consists of a commonly used surface condenser and lake water or river water, or a surface condenser and a natural draft wet cooling tower. Surface condenser (lake/river) water cooling systems are increasingly restricted by environmental protection departments due to serious thermal pollution. As a replacement, the more common form is the surface condenser natural draft wet cooling system. However, because hot water is exposed to the air in this system, the evaporation rate is high, resulting in a large demand for supplementary water. In water-scarce areas, the supply of supplementary water becomes an insurmountable defect of this system. In some cases, designers also use dry/wet hybrid systems to compensate for the shortcomings of wet cooling systems, but water quality issues still require expensive water treatment equipment.