natural draft cooling towers[1]

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Natural Draft Cooling Towers

By: Nicholas Berkholz

ENG 3060 Section 003



What is a Natural Draft Cooling Tower

� What is a

Natural Draft

Cooling

Tower?

� A Few

Important

Terms

� Components

� How it Works

� Remarks

� A natural draft cooling tower is a means to remove waste

heat from a system and release it into the atmosphere.

� Typically used at oil refineries, chemical plants and power

plants to remove heat absorbed from circulating cool water

systems.

� A common shape is the hyperboloid (See Fig. 1)

� Cooling towers have been around for over 100 years.

However, in their early for were only about 20 meters high.

Today, some can reach over 200 meters.

� As recently as 20 years ago, cooling towers were more the

exception than the rule in the industry because of theirseverely 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)



Fig. 1



Important Terms

� Wht is aNatural DraftCoolingTower?

� A Few

ImportantTerms

� Components

� How it Works

� Wet Bulb Air Temperature - the temperature a volume of air would have if cooled adiabatically to saturation atconstant pressure by evaporation of water into it, all latentheat being supplied by the volume of air(Wiki 1). Alsoknown as the dew point of ambient air.

�Adiabatically - in meteorology, referred to also as adiabaticcooling: when air cools or heats as it expands or contractswith pressure change without losing or gaining heat energyby radiation or to its surroundings. (Wiki 2)

� Dry Bulb Air Temperature The temperature at which athermometer reads freely in air but is shielded fromradiation and moisture.

� Natural Draft or Stack Effect When there is a largepressure differential between the outside air and air withina structure. Warm, moist air is less dense than dry air of thesame pressure thus causing the warm, moist air to rise.

� What is a

Natural Draft

Cooling

Tower?

� A Few

Important

Terms

� Components

� How it Works

� Remarks



Components

� What is aNatural DraftCooling Tower?

� A FewImportant Terms

� Components

� How it Works� Remarks

� Supply Basin

� Tower Pumps

� Cooling Towers

± Vertical Ribs

± Reinforced Concrete Shell

± Internal Void

±Diagonal Columns

� Hot Water Inlet

� Fill

± Splash

± Film

� Hot Water Distribution System

� Cold Water Collection

� Drift Eliminators - Drift is water lost from cooling towers as liquiddroplets are entrained in the exhaust air. The drift loss is independentof the water lost by evaporation. The drift loss may be expressed inunits of lb/hr or percentage of circulating water flow. Drift eliminatorsare used to control this drift loss from the tower. (Mist)

� What is a

Natural Draft

Cooling

Tower?

� A Few

Important

Terms

� Components

� How it Works

� Remarks



Components

� What is a

Natural Draft

Cooling

Tower?

� A Few

Important

Terms

� Components

� How it Works

� Remarks



How it Works

� What is a

Natural Draft

Cooling

Tower?

� A Few

Important

Terms

� Components

� How it Works

� Remarks

� Step 1 - As hot water enters the natural draft cooling

towers, through a series of pumps, to the warm water inlet



How it Works

� What is a

Natural Draft

Cooling

Tower?

� A Few

Important

Terms

� Components

� How it Works

� Remarks

� Step 2 - The warm water is then distributed into through a

packing or fill material inside the tower keeps the water

evenly distributed. This is plays a major role and contributes

heavily to the efficiency of the tower.

± (i.e. better the distribution allows for more contact time, and greater

surface area, which allows for more heat removal)



How it Works

� What is a

Natural Draft

Cooling

Tower?

� A Few

Important

Terms

� Components

� How it Works

� Remarks

� Step 3 - As the water is being distributed, the exposed

lower portion of the tower allows for air to pass over the

cold water basin. Its this passing of the ambient air over

the cold water basin which actually creates the differential,

thus cause the natural draft or Stack Effect.



How it Works

� What is a

Natural Draft

Cooling

Tower?

� A Few

Important

Terms

� Components

� How it Works

� Remarks

� Step 4 - As this differential is being produced the shape of

the tower itself, the hyperbolic shape, induces current

upwards.



Remarks

� What is a

Natural Draft

Cooling

Tower?

� A Few

Important

Terms

� Components

� How it Works

� Remarks

� This system is over all extremely efficient and typically

requires no fans or mechanical means to cool the water.

� Very common practice now due to the structures strength

and minimum required materials to construct.

� Efficiency of the tower depends on the ambient

temperature.

natural draft cooling towers[1]

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