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COOLING TOWER

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FUNCTION OF COOLING TOWER

The exhaust steam after power generation is passed through the surface

condenser where the steam is condensed to water causing a phase change

The latent heat of this phase change is transferred to the cooling water

circulated through the condenser

Hot water is fed to the cooling tower wherein the water is cooled and

collected in the cold water basin. The same water is again circulated through

the condenser continuously

During this process water is lost by drift and evaporation in the cooling

tower. Also some quantity of water is drained as blow down to maintain the

water quality. Make up water is added to compensate the above losses

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TYPES OF COOLING TOWER

Cooling Tower is of two types namely

Natural Draft Towers

Mechanical Draft Towers

Forced Draft

Induced draft

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NATURAL DRAFT TOWERS

Natural draft towers are also called as hyperbolic towers. They

utilize no fans to create air flow through the tower.

Natural draft towers use very large concrete chimneys to introduce

air through the media. The design of the chimney effect causes the

cold air at the bottom of the tower push the warmer air to the top.

Water is distributed as evenly as possible at the top of the tower and

allowed to drop through the air.

Packing or fills inside the tower keeps the water evenly distributed

and increases the surface area. Greater the surface area greater the

cooling efficiency.

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NATURAL DRAFT COOLING TOWER

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INDUCED DRAFT COOLING TOWER

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PERFORMANCE OF THE COOLING TOWER

"Range"is the difference between the cooling tower water inlet andoutlet temperature

"Approach"is the difference between the cooling tower outlet cold

water temperature and ambient wet bulb temperature.

Cooling tower effectiveness(in percentage) is the difference

between cooling water inlet temperature and ambient wet bulb

temperature or in other words it is = Range / (Range + Approach).

Cooling capacityis the heat rejected in kCal/hr or TR, given as

product of mass flow rate of water, specific heat and temperature

difference. Evaporation lossis the water quantity evaporated for cooling duty

Evaporation Loss (m3/hr) = 0.00085 x 1.8 x circulation rate

(m3/hr) x (T1-T2)