2. What is a Natural Draft Cooling Tower
• What is a • A natural draft cooling tower is a means to remove waste
Natural Draft heat from a system and release it into the atmosphere.
Cooling • Typically used at oil refineries, chemical plants and power
Tower? plants to remove heat absorbed from circulating cool water
• A Few systems.
Important • A common shape is the hyperboloid (See Fig. 1)
Terms • Cooling towers have been around for over 100 years.
• Components However, in their early for were only about 20 meters high.
• How it Works Today, some can reach over 200 meters.
• Remarks • “As recently as 20 years ago, cooling towers were more the
exception than the rule in the industry because of their
severely high operating cost and the large amount of capital
required for construction. But with today's need for water
conservation and minimal environmental impact. industry is
turning more and more to recycling water.”(GC3)
4. Important Terms
• Wht is aa
What is • Wet Bulb Air Temperature - the temperature a volume of
Natural Draft
Natural Draft air would have if cooled adiabatically to saturation at
Cooling
Cooling constant pressure by evaporation of water into it, all latent
Tower? heat being supplied by the volume of air(Wiki 1). Also
Tower?
• A Few known as the dew point of ambient air.
• A Few
Important • Adiabatically - in meteorology, referred to also as adiabatic
Important
Terms cooling: when air cools or heats as it expands or contracts
• Terms
Components with pressure change without losing or gaining heat energy
•
• Components
How it Works
by radiation or to its surroundings. (Wiki 2)
• How it Works • Dry Bulb Air Temperature – The temperature at which a
thermometer reads freely in air but is shielded from
• Remarks radiation and moisture.
• Natural Draft or Stack Effect – When there is a large
pressure differential between the outside air and air within
a structure. Warm, moist air is less dense than dry air of the
same pressure thus causing the warm, moist air to rise.
5. Components
•
• What isis a
What a Natural • Supply Basin
Draft Cooling
Natural Draft • Tower Pumps
Tower? • Cooling Towers
• Cooling
A Few Important – Vertical Ribs
Tower?
Terms – Reinforced Concrete Shell
•
• Components
A Few – Internal Void
• How it Works – Diagonal Columns
Important
• Remarks
Terms • Hot Water Inlet
• Components • Fill
– Splash
• How it Works – Film
• Remarks • Hot Water Distribution System
• Cold Water Collection
• Drift Eliminators - Drift is water lost from cooling towers as liquid
droplets are entrained in the exhaust air. The drift loss is independent
of the water lost by evaporation. The drift loss may be expressed in
units of lb/hr or percentage of circulating water flow. Drift eliminators
are used to control this drift loss from the tower. (Mist)
6. Components
• What is a
Natural Draft
Cooling
Tower?
• A Few
Important
Terms
• Components
• How it Works
• Remarks
7. How it Works
• What is a
Natural Draft • Step 1 - As hot water enters the natural draft cooling
Cooling towers, through a series of pumps, to the warm water inlet
Tower?
• A Few
Important
Terms
• Components
• How it Works
• Remarks
8. How it Works
• What is a
Natural Draft • Step 2 - The warm water is then distributed into through a
Cooling packing or fill material inside the tower keeps the water
Tower? evenly distributed. This is plays a major role and contributes
• A Few heavily to the efficiency of the tower.
Important – (i.e. better the distribution allows for more contact time, and greater
Terms surface area, which allows for more heat removal)
• Components
• How it Works
• Remarks
9. How it Works
• What is a
Natural Draft • Step 3 - As the water is being distributed, the exposed
Cooling lower portion of the tower allows for air to pass over the
Tower? cold water basin. It’s this passing of the ambient air over
• A Few the cold water basin which actually creates the differential,
Important thus cause the natural draft or “Stack Effect.”
Terms
• Components
• How it Works
• Remarks
10. How it Works
• What is a
Natural Draft • Step 4 - As this differential is being produced the shape of
Cooling the tower itself, the hyperbolic shape, induces current
Tower? upwards.
• A Few
Important
Terms
• Components
• How it Works
• Remarks
11. Remarks
• What is a • This system is over all extremely efficient and typically
Natural Draft requires no fans or mechanical means to cool the water.
Cooling • Very common practice now due to the structures strength
Tower? and minimum required materials to construct.
• A Few • Efficiency of the tower depends on the ambient
Important temperature.
Terms
• Components
• How it Works
• Remarks
