Air Flow Generation Methods
With respect to drawing air through the tower, there are three types of cooling towers:
- Natural draft — Utilizes buoyancy via a tall chimney. Warm, moist air naturally rises due to the density differential compared to the dry, cooler outside air. Warm moist air is less dense than drier air at the same pressure. This moist air buoyancy produces an upwards current of air through the tower.
- Mechanical draft — Uses power-driven fan motors to force or draw air through the tower.
- Induced draft — A mechanical draft tower with a fan at the discharge (at the top) which pulls air up through the tower. The fan induces hot moist air out the discharge. This produces low entering and high exiting air velocities, reducing the possibility of recirculation in which discharged air flows back into the air intake. This fan/fin arrangement is also known as draw-through. (see Image 3)
- Forced draft — A mechanical draft tower with a blower type fan at the intake. The fan forces air into the tower, creating high entering and low exiting air velocities. The low exiting velocity is much more susceptible to recirculation. With the fan on the air intake, the fan is more susceptible to complications due to freezing conditions. Another disadvantage is that a forced draft design typically requires more motor horsepower than an equivalent induced draft design. The benefit of the forced draft design is its ability to work with high static pressure. Such setups can be installed in more-confined spaces and even in some indoor situations. This fan/fill geometry is also known as blow-through. (see Image 4)
- Fan assisted natural draft — A hybrid type that appears like a natural draft setup, though airflow is assisted by a fan.
Hyperboloid (sometimes incorrectly known as hyperbolic) cooling towers (Image 1) have become the design standard for all natural-draft cooling towers because of their structural strength and minimum usage of material. The hyperboloid shape also aids in accelerating the upward convective air flow, improving cooling efficiency. These designs are popularly associated with nuclear power plants. However, this association is misleading, as the same kind of cooling towers are often used at large coal-fired power plants as well. Conversely, not all nuclear power plants have cooling towers, and some instead cool their heat exchangers with lake, river or ocean water.
Read more about this topic: Cooling Tower
Famous quotes containing the words air, flow, generation and/or methods:
“I moved like a lobster,
slower and slower.
The air was tiny.
The air would not do.”
—Anne Sexton (1928–1974)
“Though your views are in straight antagonism to theirs, assume an identity of sentiment, assume that you are saying precisely that which all think, and in the flow of wit and love roll out your paradoxes in solid column, with not the infirmity of a doubt.”
—Ralph Waldo Emerson (1803–1882)
“I call it our collective inheritance of isolation. We inherit isolation in the bones of our lives. It is passed on to us as sure as the shape of our noses and the length of our legs. When we are young, we are taught to keep to ourselves for reasons we may not yet understand. As we grow up we become the “men who never cry” and the “women who never complain.” We become another generation of people expected not to bother others with our problems.”
—Paula C. Lowe (20th century)
“The philosopher is in advance of his age even in the outward form of his life. He is not fed, sheltered, clothed, warmed, like his contemporaries. How can a man be a philosopher and not maintain his vital heat by better methods than other men?”
—Henry David Thoreau (1817–1862)