Final answer:
The induced draft cooling tower is where the coolest water comes in contact with the driest air, due to a fan inducing air to move upward through the tower, promoting efficient evaporative cooling in power generation processes.
Step-by-step explanation:
In a mechanical draft cooling tower, the type where the coolest water at the bottom of the tower comes in contact with the driest air is known as the induced draft cooling tower. This system design allows for the coolest water to interact with the driest air because the air is pulled across the water flow by a fan at the top of the tower, which induces air to enter from the bottom and move upward, becoming more humid as it gains moisture from the evaporating water. Therefore, the driest air encounters the coolest water first before exiting the top of the tower, laden with evaporated water, thus facilitating efficient cooling and evaporation.
Cooling towers are essential in power plants, such as nuclear and coal-fired power stations, where they form a critical part of the heat rejection process. Through the phenomenon of evaporative cooling, excess heat (Qc) is expelled into the environment, which is evidenced by the plume of water vapor often seen above cooling towers. This efficient heat removal method serves to maintain operational temperatures within the power generation facility, ensuring the continuous production of electricity.