COOLING TOWERS

- Cooling towers is a equipment that passes air over the water to remove the system heat from the water.
- Cooling towers are broadly divided into two type:

(1) The natural-draft or atmospheric tower, in which the air movement through the tower depends upon natural wind movement.
(b) The mechanical-draft tower through which air is drawn by fans.

Natural-Draft

-It's designed to cool water by means of air moving through the tower at the low velocities usually existing in open spaces.
-For this reason the roof of a building is an excellent location.
-These cooling towers should be so located that sufficient space is available all around the tower for free movement of air.
-Water returning from the condenser is sprayed down the tower through nozzles.
-The heat transfer from water to air is dependent upon the surface of water exposed to the air stream.
-Therefore for a good spray pattern, to produce as many fine droplets of water as possible, it is essential for good performance of the cooling tower.
-So clean nozzles are a must.
-Worn-out nozzles, scale or dirt in nozzles and piping, clogged strainers and pump impellers, all these can cause a reduction in the capacity of the cooling tower.

Mechanical-Draft

-The difference between this tower and the atmospheric type is that the draft in the mechanical-draft cooling tower is mechanically created by a fan.
-These are further classified as forced-draft or induced-draft towers.
-In the forced-draft, a fan forces the air up through the tower, while in the induced-draft type, a fan sucks the air through the tower.
-The return water from a condenser is fed into trough/troughs at the top of the cooling tower.
-Water is spread over the cooling tower area through orifices on the trough.
- Spray nozzles are seldom used.
- The towers are generally filled with a network of staggered wooden slats, to break the fall of the water over a larger surface.
-This provides more intimate contact with the air that is forced up through the cooling tower.
-The condenser water is cooled while the air is warmed and its vapor content is increased.
- The air leaves the tower in a nearly saturated condition.
-Eliminators have to be used to minimize the carry-over of entrained water in the air stream.