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.
Moist, warm air out
Hot water
Heat rejection device
(cooling tower)
Dry air in
Cold water
Remove heat from the water discharged from the
condenser so that the water can be discharged to the river
or recirculated and reused.
Cross flow
Cross flow is a design
in which the air flow
is directed
perpendicular to the
water flow (see
diagram below). Air
flow enters one or
more vertical faces of
the cooling tower to
meet the fill material.
Water flows
(perpendicular to the
air) through the fill by
gravity.
Counter flow
In a counter flow design
the air flow is directly
opposite of the water flow
(see diagram below). Air
flow first enters an open
area beneath the fill media
and is then drawn up
vertically. The water is
sprayed through
pressurized nozzles and
flows downward through
the fill, opposite to the air
flow.
1-Mechanical cooling tower.
2-natural draft cooling tower.
3-Induced draft cooling tower.
4-Forced draft cooling tower.
basic components:
1-Frame and casing:
Most towers have structural
frames that support the exterior
enclosures (casings), motors,
fans, and other components.
With some smaller designs,
such as some glass fiber units,
the casing may essentially be
the frame.
Fill:
Most towers employ fills (made of
plastic or wood) to facilitate heat
transfer by maximizing water and
air contact. Fill can either be
splash or film type.
With splash fill, water falls over
successive layers of horizontal
splash bars, continuously breaking
into smaller droplets, while also
wetting the fill surface. Plastic
splash fill promotes better heat
transfer than the wood splash fill.
Film fill consists of thin, closely
spaced plastic surfaces over which
the water spreads, forming a thin
film in contact with the air. These
surfaces may be flat, corrugated,
honeycombed, or other patterns.
The film type of fill is the more
efficient and provides same heat
transfer in a smaller volume than
the splash fill.
Nozzles:
These provide the water sprays to
wet the fill. Uniform water distribution
at the top of the fill is essential to
achieve proper wetting of the entire
fill surface. Nozzles can either be
fixed in place and have either round
or square spray patterns or can be
part of a rotating assembly as found
in some circular cross-section
towers.
FAN:
The fan is directly driven, axial flow
type fans are specially designed to
ensure AEROFOIL Section
throughout the blade length, this
ensure energy saving and
generates maximum air flow at
minimum pitch angle of blades in
the cooling towers. Fans are
electronically balanced made of light
weight Aluminum casting. Fans are
durable, corrosion resistant and low
noise delivering high flow.
Motor and gear reducer system
FAN MOTOR:
The motor is totally
weatherproof in IP:55
construction, suitable for
heated and humid
atmosphere. Special low
RPM totally enclosed motor
of vertical, flange type with
enlarged threaded shaft and
sealed top is supplied with
the cooling tower.
Drift eliminators:
These capture water droplets
entrapped in the air stream that
otherwise would be lost to the
atmosphere.
Cold
water basin:
Louvers:
The
cold water
basin, towers
located at
Generally,
cross-flow
or
near
thelouvers.
bottom The
of the tower,
have
inlet
receives
thelouvers
coolediswater
purpose of
to that
flows
down
equalize
air through
flow intothe
thetower
fill
and
Thethe
basin
usually
and fill.
retain
water
withinhas
the a
sump
low counter
point forflow
the cold
tower. or
Many
water
tower discharge
designs doconnection.
not require In
many
tower designs, the cold
louvers.
water basin is beneath the entire
fill.
Pumps of cooling tower:
Loop Pumps
Cooling Tower Spray Pumps
Natural draft, which utilizes
buoyancy via a tall chimney.
Warm, moist air naturally rises
The
paths
show how
duegreen
to theflow
density
differential
to
the
is taken
from aair.
river
thewater
dry, cooler
outside
Warm
(yellow)
intake
supply
moist airtoisan
less
dense
than drier
basin
that
the Circ Water
air at (green)
the same
temperature
and
Pumps
take
suction
pressure.
This
moistfrom.
air The
water
is then
pumpedato
the of
buoyancy
produces
current
Condenser
the water is
air throughwhere
the tower.
heated.
This photo shows a single
The
water
is then
senttower
to an as
exit
natural
draft
cooling
distribution
basin where
the
used at a European
plant.
water
then
cantowers
be returned
to
Natural
draft
are typically
the
river
and/or
pumped
by the
about
400
ft (120
m) high,
Cooling
Tower
to the
depending
on Pumps
the differential
Cooling
Towers
then
the
water
pressure
between
the
cold
returned
to the
supply
outside air
andintake
the hot
humid air
basin
can as
be the
on thewhere
insidethe
of water
the tower
reused.
driving force. No fans are used.
Cooling towers with malfunctions can freeze during very
cold weather. Typically, freezing starts at the corners of a
cooling tower with a reduced or absent heat load.
Increased freezing conditions can create growing
volumes of ice, resulting in increased structural loads.
During the winter, some sites continuously operate
cooling towers with 40 °F water leaving the tower. Basin
heaters, tower drain down, and other freeze protection
methods are often employed in cold climates.
A mechanical draft tower with a fan at the discharge
which pulls air through tower. The fan induces hot moist
air out the discharge. This produces low entering and
high exiting air velocities, reducing the possibility of
recirculation in which discharged air flows back into the
air intake. This fan/fill arrangement is also known as
draw-through.
A mechanical draft tower with a blower
type fan at the intake. The fan forces air
into the tower, creating high entering
and low exiting air velocities. The low
exiting velocity is much more
susceptible to recirculation. With the
fan on the air intake, the fan is more
susceptible to complications due to
freezing conditions. Another
disadvantage is that a forced draft
design typically requires more motor
horsepower than an equivalent induced
draft design. The forced draft benefit is
its ability to work with high static
pressure. They can be installed in more
confined spaces and even in some
indoor situations. This fan/fill geometry
is also known as blow-through.
SÉRIE 1800
(90 a 1.800m3/h)
SÉRIE 6000
(200 a 1000m3/h)