International Conference on Engineering Innovations and Solutions(ICEIS – 2016)
DESIGN AND ANALYSIS OF COOLING TOWER FOR THERMAL POWER PLANT
S.Satheesh1,G.Kumaresan2
1.P.G.Student,C.M.S College of engg,2.Asso.prof&Hod C.M.S College of engg
ABSTRACT
Cooling towers are heat removal devices used to transfer process waste heat to the atmosphere. 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,
chemical plants, power stations and building cooling. Industrial cooling towers can be used to remove heat from
various sources such as machinery or heated process material. The primary use of large, industrial cooling towers is to
remove the heat absorbed in the circulating cooling water systems used in power plants, petroleum refineries,
petrochemical plants, natural gas processing plants, food processing plants, semi-conductor plants, and for other
industrial facilities such as in condensers of distillation columns, for cooling liquid in crystallization, etc.
be up to 200 meters tall and 100 meters in diameter, or
1. INTRODUCTION
In comparison with most other industrial
equipments, the water cooling tower is a simple
rectangular structures that can be over 40 meters tall
and 80 meters long.
device, based on the direct contact of two of the
Smaller towers are normally factory-built,
earth’s most common substances: air and water; yet a
while larger ones are constructed on site. They are
surprising number of misconceptions on its design,
often associated with nuclear power plants in popular
operation and behavior prevail. Cooling basics and
culture, although cooling towers are constructed on
important misconceptions are discussed herein, with
many types of buildings.
the goal of helping to achieve the most economical
A hyperboloid cooling tower was patented by
and beneficial application, design, and operation of
Frederic van Iverson and Gerard Kuypers in 1918.
this important heat transfer device.
The first hyperboloid cooling towers were built in the
1.1 Cooling Tower
last 1920s in Liverpool, England to cool water used at
Cooling towers are heat removal devices
used to transfer process waste heat to the atmosphere.
Cooling towers may either use the evaporation of
a electrical power station that used coal
2. LITERATURE REVIEW
Sadik Kakak & Hongtan Lin, “Heat
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
Exchangers, Selection, rating, & Thermal
design” (II edition) , pp no 170- 181.
air to cool the working fluid to near the dry-bulb air
temperature.
Heat Exchangers or Radiators used in
Common applications include cooling the
automobiles/IC Engines are either rectangular or
circulating water used in oil refineries, chemical
square in shape, but the air blown/sucked by means of
plants, power stations and building cooling. The
the fan is in circular in area, developing low velocity
towers vary in size from small roof-top units to very
zones in the corners-hence it is proposed to eliminate
large hyperboloid structures (as in Image 1) that can
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corners and develop circular radiators. The object of
Performance analysis and optimal design
work is to have a circular radiator which is compact-
of
made
with
minimum
material-less
efficient-that will work with
costly-more
minimum power
consumption of fan and maximum utilization of air
heat
exchangers
used
in
high
temperature and high-pressure system
Author: tail sela
flow. It is proposed that the results of rectangular and
A computational study for the optimal design
circular radiators will be compared. Here results like
of heat exchangers (HX) used in a high temperature
velocity, flow rate of water, and temperature at
and high-pressure system is presented. Two types of
different points of the radiator are compared. After
air to air HX are considered in this study. One is a
validating the
actual
single-pass cross-flow type with straight plain tubes
manufacturing and mathematical calculations it can be
and the other is a two-pass cross-counter flow type
commercially applied
as
with plain U-tubes. These two types of HX have the
automobile radiators, IC Engine radiators, heat
staggered arrangement of tubes. The design models
exchangers used in refrigerators and air-conditioners
are formulated using the number of transfer units (ε-
etc.
NTU method) and optimized using a genetic
JP Yadavand ,Bharat Raj Singh,(2011)
algorithm. In order to design compact light weight HX
present
concept
to
through
applications
such
“Study on Performance Evaluation of
Automotive Radiator”,
with the minimum pressure loss and the maximum
heat exchange rate, the weight of HX core is chosen
as the object function. Dimensions and tube pitch ratio
Heat exchanger is a device designed to
of an HX is used as design variables. Demanded
transfer heat between two physically separated fluids;
performance such as the pressure loss (ΔP) and the
generally consists of a cylindrical shell with
temperature drop (ΔT) are used as constraints.
longitudinal tubes; one fluid flows on the inside, the
3. INDUSTRIAL, COMMERCIAL, AND
other on the outside. Any of several devices that
transfer heat from a hot to a cold fluid, in many
engineering applications, one fluid needs to be heated
INSTITUTIONAL BOILERS
3.1 Boiler
and another cooled, a requirement economically
Combustion boilers are designed to use the
accomplished by a heat exchanger. In double-pipe
chemical energy in fuel to raise the energy content of
exchangers, one fluid flows inside the inner pipe, and
water so that it can be used for heating and power
the other in the annular space between the two pipes.
applications. Many fossil and non-fossil fuels are fired
In shell-and-tube exchangers, many tubes are mounted
in boilers, but the most common types of fuel include
inside a shell; one fluid flows in the tubes and the
coal, oil, and natural gas. During the combustion
other flows in the shell, outside the tubes. Special-
process, oxygen reacts with carbon, hydrogen, and
purpose devices such as boilers, evaporators, super
other elements in the fuel to produce a flame and hot
heaters, condensers, and coolers are all heat
combustion gases. As these gases are drawn through
exchangers.
the boiler, they cool as heat is transferred to water.
Eventually the gases flow through a stack and into the
atmosphere.
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As long as fuel and air are both available to
institutions and for other industrial applications.
continue the combustion process, heat will be
Smaller boilers with less capacity are categorized as
generated. Boilers are manufactured in many different
ICI boilers. Industrial boilers are used extensively by
sizes
the chemical, food processing, paper, and petroleum
and
configurations
depending
on
the
characteristics of the fuel, the specified heating
industries.
output, and the required emissions controls. Some
They have heat input capacities up to and
boilers are only capable of producing hot water, while
sometimes more than 250 MBtu/h. Commercial and
others are designed to produce steam. Various studies
institutional
have been conducted to estimate the number of boilers
applications including commercial businesses, office
in the United States, but no data source provides a
buildings, apartments, hotels, restaurants, hospitals,
complete representation
schools,
of the existing boiler
population.1
boilers
museums,
are
used
government
in
many
buildings,
other
and
airports.
In the United States, boilers are typically
In the past when emissions were less
designed and constructed as either power or heating
regulated, choosing the right boiler and combustion
boilers in accordance with applicable requirements
equipment for a particular application generally
adopted by the American Society of Mechanical
involved matching the process requirements with the
Engineers (ASME). Rules for power boilers are
boiler’s output capacity. Proper sizing and selection
provided in Sect. I of the ASME Boiler and Pressure
required knowledge of the peak process requirements
Vessel Code.2 these rules apply to steam boilers that
and an understanding of the load profile. This boiler
operate above 15 psig and hot water boilers that
selection philosophy emphasized energy conversion at
operate above 160 psig or 250°F. Common design
the lowest possible cost. Reduced emphasis was
pressures are 150, 200, 250, and 300 psig, but higher
placed on controlling emissions.
pressures are possible. 3 For example, boilers for
Public concerns about air and water quality
certain pulp and paper industry applications are now
and enactment of federal, state, and local regulations
designed for pressures as high as 1,500 psig.
have shifted this emphasis. The current design
Corresponding rules for heating boilers are provided
objective is to provide low-cost energy with an
in Sect. IV.4 According to these rules, heating boilers
acceptable impact on the environment. Depending on
that produce hot water are not allowed to operate
construction
above 160 psig or at temperatures above 250°F at or
configured in
near the boiler outlet. Additional rules limit heating
arrangements. Because the design of fire tube boilers
boilers that produce steam to a maximum operating
is simple, they are easy to construct in a shop and can
pressure of 15 psig.
be shipped fully assembled as a package unit.
details,
these
boilers
one, two, three, or
have
four
tubes
pass
Many boilers with heat input capacities more
than 250 million British thermal units per hour
(MBtu/h) are classified as utility boilers because they
are used at power plants to produce electricity. Some
boilers of this size are also used at paper mills and
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facilities such as in condensers of distillation columns,
for cooling liquid in crystallization, etc.
Fig: No: 3.1 Configuration of HRT fire tube boiler
3.1.2 Water tube Boilers
Water tube boilers are designed to circulate
Fig: No: 3.2 Industrial Cooling Towers for a Power
hot combustion gases around the outside of a large
number of water-filled tubes. the tubes extend
between an upper header, called a steam drum, and
one or lower headers or drums. In older designs, the
tubes are either straight or bent into simple shapes.
Newer boilers have tubes with complex and diverse
Plant
4. AIR-TO-WATER FLOW
4.1.1 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
bends.
Because the pressure is confined inside the
tubes, water tube boilers can be fabricated in larger
sizes and used for higher-pressure applications. Small
water tube boilers, which have one and sometimes
two burners, are generally fabricated and supplied as
packaged units. Because of their size and weight,
large water tube boilers are often fabricated in pieces
and assembled in the field. Almost any solid, liquid,
or gaseous fuel can be burned in a water tube boiler.
3.1.3 Industrial Cooling Towers
Industrial cooling towers can be used to
remove heat from various sources such as machinery
or heated process material. The primary use of large,
industrial cooling towers is to remove the heat
absorbed in the circulating cooling water systems used
in power plants, petroleum refineries, petrochemical
faces of the cooling tower to meet the fill material.
Water flows (perpendicular to the air) through the fill
by gravity.
The air continues through the fill and thus
past the water flow into an open plenum area. A
distribution or hot water basin consisting of a deep
pan with holes or nozzles in the bottom is utilized in a
cross flow tower. Gravity distributes the water
through the nozzles uniformly across the fill material.
4.1.2 Counter flow:
In a counter flow design the air flow is
directly opposite to 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.
plants, natural gas processing plants, food processing
plants, semi-conductor plants, and for other industrial
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its surroundings. Note that the water evaporated in the
cooling process is "pure" water, in contrast to the very
small percentage of drift droplets or water blown out
of the air inlets.
5. TWO WAY COOLING TOWER
5.1 Major Components of The Two Way
Cooling Tower
 Top tank
 Heater
Fig no. 4.1 Counter Flow Type Design
4.2 Some Commonly Used Terms In The
 Partition plate
 bottom tank
 Recirculation pump
Cooling Tower Industry
 Blower
4.2.1 Drift
Water drop lets that are carried out of the
5.1.1 Top tank
It is made up of G.I sheet. It is assumed
cooling tower with the exhaust air. Drift droplets have
the same concentration of impurities as the water
entering the tower. The drift rate is typically reduced
by
employing baffle-like devices,
called drift
eliminators, through which the air must travel after
leaving the fill and spray zones of the tower. Drift can
also be reduced by using warmer entering cooling
boiler heat water collecting tank. After rotate the
turbine steam will enter the condenser and the steam
condensate to water. After that water goes to
regeneration plant. In this project water is heated
certain temperature. After that water goes to gradually
bottom tank through gravity force.
5.1.2 Electric heater
tower temperatures.
Electric heating is any process in which
4.2.2 Blow-out
Water drop let’s blown out of the cooling tower
by wind, generally at the air inlet openings. Water
may also be lost, in the absence of wind, through
splashing or misting. Devices such as wind screens,
louvers, splash deflectors and water diverters are used
electrical energy is converted to heat. Common
applications include space heating, cooking, and water
heating and industrial processes. An electric heater is
an electrical appliance that converts electrical energy
into heat. The heating element inside every electric
heater is simply an electrical resistor, and works on
to limit these losses.
the principle of Joule heating: an electric current
4.2.3 Plume –T
through a resistor converts electrical energy into heat
The steam of saturated exhaust air leaving
the cooling tower, the plume is visible when water
vapor it contains condenses in contact with cooler
ambient air, like the saturated air in one's breath fogs
on a cold day. Under certain conditions, a cooling
energy.
Alternatively, a heat pump uses an electric
motor to drive a refrigeration cycle, drawing energy
from a source such as the ground or outside air and
directing it into the space to be warmed. Some
tower plume may present fogging or icing hazards to
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systems can be reversed so that the interior space is
The element emits infrared radiation that travels
cooled and the warm air is discharged outside or into
through air or space until it hits an absorbing surface,
the ground. Heat pumps can deliver two or three units
where it is partially converted to heat and partially
of heating energy for every unit of electricity
reflected. This heat directly warms people and objects
purchased. For a detailed explanation of heat pumps
in the room, rather than warming the air. This style of
please see Carnot cycle.
heater is particularly useful in areas which unheated
5.1.3 Types of Heater
air flows through. They are also ideal for basements
(A) Space Heating:
and garages where spot heating is desired. More
generally, they are an excellent choice for taskspecific heating.
(C) Convection Heaters
In a convection heater, the heating element
heats the air next to it by convection. Hot air is less
dense than cool air, so it rises due to buoyancy,
allowing more cool air to flow in to take its place.
This sets up a constant current of hot air that leaves
the appliance through vent holes and heats up the
surrounding space.
(D) Fan Heaters
A fan heater, also called a forced convection
heater, is a variety of convection heater that includes
an electric fan to speed up the airflow. This reduces
the thermal resistance between the heating element
and the surroundings faster than passive convection,
Fig: No: 5.1 Electric Radioactive Space
Heaters
allowing heat to be transferred more quickly. They
operate with considerable noise caused by the fan.
They have a moderate risk of ignition hazard in the
Although they all use the same physical
event that they make unintended contact with
principle to generate heat, electric heaters differ in the
furnishings. This type of heater is a good choice for
way they deliver that hot air to the environment.
quick heating of enclosed spaces.
Several types are described in the sections below
(B) Radioactive Heaters
Radioactive
heaters
(E) Storage Heating
A storage heating system takes advantage of
heating
cheaper electricity prices, sold during low demand
element that reaches a high temperature. The element
periods such as overnight. In the United Kingdom,
is usually packaged inside a
glass envelope
this is branded as Economy 7. The storage heater
resembling a light bulb and with a reflector to direct
stores heat in clay bricks, then releases it during the
the energy output away from the body of the heater.
day when required.
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a
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(F) Domestic Electrical Under Floor
to minimize the temperature optimum level. In this
Heating
project we have used two numbers of partitions.
These systems are called radiant heating
systems, regardless of whether they include a heat
exchanger (also called a radiator) or are electrically
powered. When a home radiant heat system is turned
on, the current will flow through a conductive heating
So the entire temperature maximum decreased. Here
after two blower used in this project. So forced
circulation air is used to reduce the temperature
simultaneously.
5.1.4 Bottom tank
It is made up of G.I sheet. It is extreme bottom
material.
tank. After that water passes partition plate it comes to
(G) Heat Pumps
A heat pump uses an electrically-driven
compressor to operate a refrigeration cycle that
extracts heat energy from the outdoor air or from the
ground or ground water, and upgrades its temperature
to a level high enough to use for space heating. The
bottom tank. In this water maximum temperature
extracted by blower and falling top to bottom tank.
Here after the cooled water again pumped from
bottom to top tank through centrifugal pump. Thus the
water circulates from again and again.
working fluid boils at a low temperature, absorbing
5.1.5 Recirculation Pump (Centrifugal
heat in an outdoor heat exchanger, then the resulting
Pump)
vapor is compressed and condenses to liquid form in a
condenser inside the building.
A centrifugal pump is a roto dynamic pump
that uses a rotating impeller to create flow by the
addition of energy to a fluid. Centrifugal pumps are
(H) Electrode Heater
With an electrode heater, there is no wire-
commonly used to move liquids through piping. The
wound resistance and the liquid itself acts as the
fluid enters the pump impeller along or near to the
resistance. This has potential hazards so the
rotating axis and is accelerated by the impeller,
regulations governing electrode heaters are strict.
flowing racially outward into a diffuser or volute
(i)Water Heating
chamber (casing), from where it exits into the
Water heating by electricity is usually done
downstream piping.
by an immersion heater mounted in the top of the hot
water cylinder. The heater contains an insulated
electric resistance heater and a temperature sensor.
Domestic immersion heaters (usually rated at 3
kilowatts in the UK) run on the normal domestic
electricity supply.
5.1.4 Partition Plate
The partition plate has inserted between top
plate has several holes in this surface area. This hole
is used to decelerate the water velocity. So that time
Fig: No: 5.2 Cut away View of Centrifugal
taken is increased to flow water passing. This is used
Pump
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an air stream, and devices that take advantage of this,
such as anemometers and wind turbines, often have
designs similar to that of a fan.
In addition to their utilitarian function,
vintage or antique fans, and in particular electric fans
manufactured from the late 19th century through the
1950s, have become a recognized collectible category;
for example, in the U.S.A. there is the Antique Fan
Collectors Association.
Fig: No: 5.3 Impeller
A
centrifugal
pump
uses
a
spinning
"impeller," which normally has backward-swept
blades that directly push water outward. Like most
pumps, a centrifugal pump converts mechanical
energy from a motor to energy of a moving fluid;
some of the energy goes into kinetic energy of fluid
motion, and some into potential energy, represented
by a fluid pressure or by lifting the fluid against
gravity to a higher level.
Fig: No: 5.4 Fan Blower
6. GENERAL WORKING PRINCIPLES
OF THE COOLING TOWER
5.1.6 Fan Blower
The cooling tower is a piece of equipment
A mechanical fan is a machine used to create
designed to disperse a heat flux in atmospheric air. A
flow within a fluid, typically a gas such as air. A fan
heat flux is provided by cooling water. In a cooling
consists of a rotating arrangement of vanes or blades
tower, cooled water comes into direct contact with
which act on the air. Usually, it is contained within
atmospheric air.
some form of housing or case. This may direct the
airflow or increase safety by preventing objects from
contacting the fan blades. Most fans are powered by
electric motors, but other sources of power may be
used, including hydraulic motors and internal
combustion engines and solar power.
Fans produce air flows with high volume and
low pressure, as opposed to compressors which
Fig: No: 6.1 Working Principle Of Cooling
produce high pressures at a comparatively low
volume. A fan blade will often rotate when exposed to
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Hot water flows to the main sewer of the
designed in such a way to obtain desired cooling
water distribution system. Then, the water is
effect in the most unfavorable conditions (high
distributed through a pipe system to spray nozzles.
temperature, humidity along with the need to remove
Nozzles cause the dispersion of the water onto the wet
as much heat from the water as possible.) The power
deck surface, thus creating water film of large contact
of the fan is selected appropriately to these conditions.
surface. The water coming off the lower edges of the
When ambient temperature or amount of heat is
wet deck surface falls down in the form of droplets to
reduced some of the power installed becomes
the cooled water tank, from where it is pumped back
redundant. In order to reduce operating costs and to
to the cooled equipment.
improve operating safety, the fan can be equipped
The process of water cooling occurs mainly
with two-speed motors (optionally). Fans' RPM and
as the result of the evaporation of a small amount of
consequently their power consumption are determined
cooled water to the air stream (transport of mass),
based on the temperature of the cooled water.
making the use of the heat of phase transition (heat of
In order to ensure stable and safe operation
vaporization), which is collected from the water
of the cooling system, it is necessary to maintain
stream and to a lesser extent as the result of
adequate parameters of the cooling water, because of
convective heat transfer form water to air (heat
the fact that constant evaporation results in chemical
transfer) Counter-current air flow in the cooling tower
and mechanical pollution concentration in the cooling
is inducted by the suction produced by the axial fan
cycle. The desalination, de sludging and maintenance
with a capacity adapted to the required cooling
of the cooling system are one of the most important
parameters. The fan is mounted inside the enclosure
parameters affecting the durability of components and
on the roof of the cooling cell. The air is sucked into
other related equipment
the cell through inlet ports equipped with shutters,
which protect the system from sucking things such as
foliage and from splashing cooled water outside the
cooling tower.
Then, the sucked air flows through the rain
zone under the wet deck surface, through the fill,
splash zone above the wet deck surface and then it
undergoes the process of mist elimination, which
minimizes water loss resulting from dissipation of
droplets. The heated and moisten air flows through the
fan, and then it is blown away outside through the
upper section of the fan casing to the environment.
Water cooling level in the wet cooling tower depends
on the wet bulb temperature of ambient air, air volume
Fig No 6.2 Flow Diagram
(fan efficiency) and technical solutions used in a given
model of a cooling tower. Wet cooling towers are
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4.
SRINIVASAN.R (2004) “Hydraulic &
pneumatic controls”, Vijay Nicole imprints
private ltd.
Fig No 6.3 Block Diagram of Cooling Tower
7. FUTURE WORK
The project “DESIGN AND ANALYSIS
OF
COOLING
TOWER
FOR
THERMAL
POWER PLANT” carried out by us made design an
impressing task. Through this type of changes in Heat
transfer principle and its application etc. Therefore,
the main aim from the project is to reduce the time
taken and efficiency over the other system. Future
work of this project is analysis the cooling tower
properties.
8. REFERENCES
1.
GUPTA J.K and KHURUMI R.S (1981)
“Text book of Machine Design”, S.Chand &
comp
and
Parr.
ANDREW
(2003)
‘Hydraulic & Pneumatics’ Butterworth
Heimann Ltd
2.
Dr.D.K.AGGARVAL
SHARMA(2004)
&
“machine
Dr.P.C
design”,
S.K.Kataria and sons
3.
MAJUMDAR.S.R “Pneumatic systems”,
Tata mcgraw-hills company ltd.
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