Cooling tower selection with favorable ambient air: When the ambient air temperature and humidity are both low, which type of cooling tower draft is typically preferred?

Introduction / Context:
Cooling towers reject heat by evaporative cooling, drawing ambient air into contact with warm water. The air can be moved by natural buoyancy (natural draft) or by fans (forced or induced draft). Ambient conditions influence which configuration is most practical and efficient.

Given Data / Assumptions:

• Ambient air is cool and dry, creating a strong driving force for evaporation.
• Large installations where a hyperbolic natural-draft tower is feasible.
• No special plume abatement or high turn-down requirements.

Concept / Approach:
Low temperature and low humidity increase the wet-bulb depression, enhancing buoyancy of the warm, moist exit air. Natural-draft towers capitalize on this density difference to move large air volumes without fans, reducing mechanical complexity and power consumption.

Step-by-Step Solution:
Identify favorable ambient conditions (cool, dry) → strong natural buoyancy.Natural draft uses a tall chimney/hyperbolic shell to sustain airflow.Therefore, when conditions are favorable, natural draft is typically preferred.Select 'Natural draft'.

Verification / Alternative check:
Power plants in temperate climates often employ natural-draft towers to avoid fan energy; under hot/humid conditions, mechanical draft is chosen to guarantee airflow.

Why Other Options Are Wrong:
Forced and induced draft rely on fans and are favored when ambient conditions are less favorable or when precise airflow control is needed; not necessary here.

'None' is inappropriate because a tower type is indeed applicable.

Common Pitfalls:

• Assuming natural draft suits all climates; high humidity or high ambient temperatures weaken buoyancy.
• Ignoring site constraints that may necessitate mechanical draft despite favorable weather.

Final Answer:
Natural draft