Which of the following methods could be used to circulate air in a cooling tower?

The correct response is that all of the listed methods can be utilized to circulate air in a cooling tower.

Induced draft fans are mechanical devices that pull air through the cooling tower, enhancing the cooling process by increasing airflow rates. This method is particularly effective in counterflow cooling towers, where air is drawn in from the bottom and passes upward while water flows downward.

Natural draft relies on the buoyancy of warm air. In this case, the difference in density between the warm, moist air inside the cooling tower and the cooler outside air creates a natural upward airflow. This method is often seen in taller cooling towers and capitalizes on the natural convection phenomenon without the need for mechanical assistance.

Convection currents occur as a result of temperature differences within the cooling tower. Warmer, lighter air rises, allowing cooler air to be drawn in from below. This process aids in the cooling of the water as it facilitates continuous air movement.

Since all three methods—induced draft fans, natural draft, and convection currents—effectively contribute to airflow in cooling towers, the comprehensive answer acknowledges that multiple mechanisms can be employed to promote air circulation, enhancing the cooling capability of the system.