Natural Convection Cooling Towers:

Natural convection cooling towers, described in Figure, use the principle of convective flow to give air circulation. Since the air within the tower is heated, it rises through the tower. That procedure draws more air in, creating a natural air flow to gives cooling of the water. A basin at the bottom of the tower is open to the atmosphere. A cooler, denser air outside the tower will flow in at the bottom and contribute to the air circulation inside the tower. The air circulation will be self perpetuating because of the density difference among the warmer air within and the cooler air outside.

Figure: Natural Convection Cooling Tower

The incoming water is sprayed around the circumference of the cascades and tower to the bottom. A natural convection cooling towers are much larger than the forced draft cooling towers and cost much more to construct. Since, of space considerations and cost, natural convection cooling towers are established less frequently than other categories.