A cooling tower is a heat rejection device which extracts waste heat to the atmosphere through the cooling of a water stream to a lower temperature. A cooling tower is a heat rejection device which extracts waste heat to the atmosphere through the cooling of a water stream to a lower temperature. Cooling towers may either use the evaporation of water to remove process heat and cool the working fluid to near the wet-bulb air temperature or, in the case of closed circuit dry cooling towers, rely solely on air to cool the working fluid to near the dry-bulb air temperature. Common applications include cooling the circulating water used in oil refineries, petrochemical and other chemical plants, thermal power stations and HVAC systems for cooling buildings. The classification is based on the type of air induction into the tower: the main types of cooling towers are natural draft and induced draft cooling towers. Cooling towers vary in size from small roof-top units to very large hyperboloid structures (as in the adjacent image) that can be up to 200 metres (660 ft) tall and 100 metres (330 ft) in diameter, or rectangular structures that can be over 40 metres (130 ft) tall and 80 metres (260 ft) long. The hyperboloid cooling towers are often associated with nuclear power plants,[1] although they are also used to some extent in some large chemical and other industrial plants. Although these large towers are very prominent, the vast majority of cooling towers are much smaller, including many units installed on or near buildings to discharge heat from air conditioning.

1. COOLING TOWER
ASHIF A R
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Phone No. - 9745350127
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2. CONTENTS
• INTRODUCTION
• COOLING TOWER SYSTEM
• ASSESSMENT OF COOLING TOWER
• CONCLUSION
• REFERENCES
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3. INTRODUCTION
• Semi-enclosed device for evaporative cooling of water by contact with air
• Cooling towers vary in size from small roof-top units to very large
hyperboloid structures
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4. Classification by use
By use
• Heating, ventilation and air conditioning (HVAC)
• Industrial cooling towers
By build
• Package type
• Field erected type
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6. COOLING TOWER - BASICS
• Wooden, steel or concrete structure
and corrugated surfaces or baffles
or perforated
• Trays are provided inside the tower for
uniform distribution and better atomization
of water in the tower.
• The hot water coming out from the condenser is fed to the tower on the top
and allowed to tickle in form of thin drops.
• The air flows from bottom of the tower or perpendicular to the direction of
water flow and then exhausts to the atmosphere after effective cooling.
• To prevent the escape of water particles with air, draft eliminators are
provided at the top of the tower.
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7. COOLING TOWER SYSTEM
• The water pumped from the tower basin is the
cooling water routed through the process coolers
and condensers in an industrial facility.
• The cool water absorbs heat from the hot process
streams which need to be cooled or condensed
and the absorbed heat warms the circulating
water (C).
• The warm water returns to the top of the cooling
tower and trickles downward over the fill material
inside the tower.
• It comes in contact with ambient air rising up
through the tower either by natural draft or by
forced draft using large fans in the tower.
Where,
C = Circulating cooling water
E = Evaporated water
W = Windage or Drift loss
M = Make-up water
D = Draw-off or Blow down water
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8. COOLING TOWER SYSTEM…....
• Contact causes a small amount of the water to be lost as
wind age (W) and some of the water (E) to evaporate.
• The heat required to evaporate the water is derived from
the water itself, which cools the water back to the original
basin water temperature and the water is then ready to
recirculate.
• The evaporated water leaves its dissolved salts behind in
the bulk of the water which has not been evaporated, thus
raising the salt concentration in the circulating cooling
water.
• To prevent the salt concentration of the water from
becoming too high, a portion of the water is drawn off (D)
for disposal.
• Fresh make-up water (M) is supplied to the tower basin to
compensate for the loss of evaporated water, the wind age
loss water and the draw-off water.
Where,
C = Circulating cooling water
E = Evaporated water
W = Windage or Drift loss
M = Make-up water
D = Draw-off or Blow down water
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9. ASSESSMENT OF COOLING TOWER
RANGE
• This is the difference between the cooling tower water
inlet and outlet temperature.
• A high CT Range means that the cooling tower has been
able to reduce the water temperature effectively, and is
thus performing well
APPROACH
• This is the difference between the cooling tower outlet
cold water temperature and ambient wet bulb
temperature. Although, both range and approach should
be monitored, the `Approach’ is a better indicator of
cooling tower performance.
EFFECTIVENESS
• This is the ratio between the range and the ideal range (in
percentage), i.e. difference between cooling water inlet
temperature and ambient wet bulb temperature, or in
other words it is
= Range / (Range + Approach).
Range and Approach of cooling tower
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10. Structural stability
• Being very large structures, cooling towers are susceptible to wind damage, and several
spectacular failures have occurred in the past.
• At Ferry bridge power station on 1 November 1965, the station was the site of a major
structural failure, when three of the cooling towers collapsed owing to vibrations in 85 mph
(137 km/h) winds.
• Although the structures had been built to withstand higher wind speeds, the shape of the
cooling towers caused westerly winds to be funnelled into the towers themselves, creating
a vortex.
• Three out of the original eight cooling towers were destroyed, and the remaining five were
severely damaged.
• The towers were later rebuilt and all eight cooling towers were strengthened to tolerate
adverse weather conditions.
• Building codes were changed to include improved structural support, and wind tunnel tests
were introduced to check tower structures and configuration. 10

11. CONCLUSION
• The design of cooling tower is closely related to tower Characteristic and
different types of losses generated in cooling tower.
• Even though losses are generated in the cooling tower, the cooling is
achieved due to heat transfer between air and water.
• In ideal condition, the heat loss by water must be equal to heat gain by air.
• But in actual practice it is not possible because of some type of losses.
• Cooling tower performance increases with increase in air flow rate and
characteristic decreases with increase in water to air mass ratio.
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12. REFERENCES
1. Kai Wang, Feng - zhong Sun, Yuan-bin Zhao, Ming Gao, Lei Ruan,
Experimental research of the guiding channels effect on the thermal
performance of wet cooling towers subjected to crosswinds – Air guiding
effect on cooling tower, Applied Thermal Engineering 30 (2010) 533–538.
2. Z. Zhai, S. Fu, Improving cooling efficiency of drycooling towers under
cross-wind conditions by using wind-break methods, Applied Thermal
Engineering 26 (2006) 1008–1017.
3. Jameel - Ur - Rehman Khan, Bilal Ahmed Qureshi, Saiyed M. Zubair, A
comprehensive design and performance evaluation study of counter flow
wet cooling towers, Internal Journal of Refrigeration 27 (2004) 914-923.
4. Wikipedia(Images)
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