2007 PROJECT DOCUMENT ON EXERGY

Exergy Analysis of Thermal Power Plant
Department of Mechanical Engg, SVIST, Kadapa. Page 1
NOMENCLATURE
HPT : High pressure turbine
IPT : Intermediate pressure turbine
LPT : Low pressure turbine
BFP : Boiler feed pump
LPH : Low pressure heater
HPH : High pressure heater
FRS : Feed water regulating station
GSC : Gland steam cooler
P.L.F : Plant load factor
CEP : Condensate extraction pump
Ψ : Exergy
ηI : First law efficiency
ήII : Second law efficiency
W : Work done in kw
I destroyd = To ˙Sgen : Irreversibility destroyed or exergy l
∑n
k=1 (1 – (÷ Tk))Qk : Exergy summation supplied through heat transfer
Tk : Temperature of heat source/sink at which
heat is transferred or rejected
Qk : Heat transfer rate in kW
Ψw : Work done by the system
Sgen : Entropy generated in kW/K
.m : Mass inlet or exit rate in kg/s
.s : Entropy inlet or exit rate in kW/K
p : Pressure in bar
h : enthalpy in kJ/kg

H : enthalpy in MW
s : entropy in kJ/kg-K
S : entropy in MW/K
To : atmospheric temperature in K
mg : mass of gases in kg/s
gi : gas inlet
go : gas outlet
ms : mass of steam in kg/s
mw : mass of water in kg/s
SH : super-heater
mb : mass of boiler in kg/s
bi : boiler inlet
bo : boiler outlet

CONTENTS
ABSTRACT ............................................................................................................................................................................................................................................................................................8
CHAPTER 1............................................................................................................................................................................................................................................................................................9
1.0 INTRODUCTION TO RTPP...............................................................................................................................................................................................................................................9
1.1 GENERAL………………………………………………………………………………………………………………………………………………………….9
1.2 LOCATION……………………………………………………………………………………………………………………………………… …………….…..9
1.3 RAWMATERIAL……………………………………………………………………………………………………………………………………...…...……..11
1.4 COMBUSTION PROCESS………………………………………………………………………………………………………… …………………………….11
1.5 OPERATIONAL DATA…………………………………………………………………………………………………………………......................................11
CHAPTER 2.........................................................................................................................................................................................................................................................................................13
2.1 RANKINE CYCLE..............................................................................................................................................................................................................................................................13
2.2 REGENERATIVE CYCLE ...............................................................................................................................................................................................................................................15
2.3 .REHEAT CYCLE ...............................................................................................................................................................................................................................................................17
2.4 TYPICAL VALUES OF EFFICIENCIES....................................................................................................................................................................................................................20
2.5 FACTORS INCREASING THE THERMAL CYCLE EFFICIENCY..................................................................................................................................................................20
2.6 PLANT LOSSES..................................................................................................................................................................................................................................................................22
CHAPTER 3.........................................................................................................................................................................................................................................................................................23
3.0 INTRODUCTION TO EXERGY ....................................................................................................................................................................................................................................23
3.1 ENERGY................................................................................................................................................................................................................................................................................23
3.2 EXERGY.…………………………………………….…………………………………………………………………………………………… ………………24
3.3 APPLICATIONS OF THE SECOND LAW OF THERMO DYNAMICS……………………………………………………………………….…..…………..28
3.4 WORK DONE……………………………………………………………………………………………………………………..………………….…………..30
3.5 LAWS OF THERMO DYNAMICS…………………………………………………………………………………………..……………………….…………..32
3.6 LAW OF DEGRADIATION ENERGY…………………………………………………………………… ………..……………………………………………33
CHAPTER 4.........................................................................................................................................................................................................................................................................................34
4.0 DATA COLLECTION........................................................................................................................................................................................................................................................34
4.1TECHNICAL DATA............................................................................................................................................................................................................................................................34
4.2 GENERAL DATA………………………………………………………….…………………………………………………………………………………….34
4.3 HEAT RATE VALUES……………………………………………….…………………………………………………………………………………………..37
CHAPTER 5.........................................................................................................................................................................................................................................................................................40
5.0 COMPONENTS ON WHICH ANALYSIS IS MADE .............................................................................................................................................................................................40
5.1 BOILER..................................................................................................................................................................................................................................................................................40
5.2 TYPES OF BOILERS.........................................................................................................................................................................................................................................................40
5.3 SUPER HEATER.................................................................................................................................................................................................................................................................41
5.4 CONDENSER.......................................................................................................................................................................................................................................................................42
5.5 TYPES OF CONDENSERS…………………………………………………………………………………………………………………………………...….44
5.6 COOLING TOWER……………………………….……………………………………………………………………………………… ………………...……45
5.7 TYPES OF COOLING TOWERS…………………………………………………………………………………………………………………………...…….46
5.8 CONDENSATE EXTRACTION PUMP……………………………………………………………………………………………… …..………………………48
5.9 EJECTORS…………………………………………………………………………………………………………………………………..…………..…………48

5.10 FEED WATER HEATER…………………………………………………………………………………………………………………………………...……49
5.11 DEAREATOR…………………………………………………………………………………...………………………………………………………..………50
5.12 BOOSTER PUMP…………………………………………………………………………………………………………………....………………………….. 51
5.13 BOILER FEED WATER PUMP……………………………………………………………………… ……………………….………………………………...51
5.14 ECONOMISER………………………………………………………………………………………………….……………………………………………….52
5.15 ELECTRO STATIC PRECIPITATORS……………………..…………………………………………………………………………………………………..53
5.16 BOILER REHEATER…………………………………………………… ……………………..………………………………………………………………...54
CHAPTER6..........................................................................................................................................................................................................................................................................................56
6.0 TABLES AND CALCULATIONS.................................................................................................................................................................................................................................56
6.1 ENTHALPY AND ENTROPY OF THE COMPONENTS......................................................................................................................................................................................56
6.2 THERMO DYNAMIC EXTRACTION OF STEAM AT TURBINES………………………………………………………………………………..…… 79
6.3 TABULATED VALUES OF TURBINE………………………………………………………………………………………………………………………….81
CHAPTER 7…………………………………………………………………………………………………………………………………………..…………………...83
7.0 EXERGY AND ENERGY ANALYSIS ON THE COMPONENTS…………………………………………………………………………………….………...83
7.1 EXERGY ANALYSIS……………………………………………………………………………………………………… …………………..………………….83
7.2 ENERGY ANALYSIS………………………………………………………………………………………………………………………...……………………90
7.3 TABLES OF THE EXERGY, ENERGY EFFICIENCIES AND LOSSES…………………………………………………… …………………………………..95
CHAPTER 8…………………………………………………………………………………………………………………………… ……………….…………………97
8.0 COMPARISONOF GRAPHS BETWEEN EXERGY AND ENERGY…………………………………………………………………..………………………97
8.1 EXERGY DESTRUCTION GRAPH………………………………………………………………………………………… ……………………………….…. 97
8.2 TURBINE EFFICIENCY AND DESTRUCTION GRAPH…………………………………………………………………… ………………………………... 97
8.3 EXERGY VS ENERGY GRAPH………………………………………………………………………………………………………....................................….98
8.4 COMPARISON GRAPH………………………………………………………………………………………………………………..…………….…………....98
CHAPTER 9………………………………………………………………………………………………………………………………………………………………99
9.0 CONCLUSION…………………………………………………………………………………………………………………………….……………...……….99
9.1 RECOMMENDATIONS FOR FURTHER STUDIES………………………………………………………………………………………………….….....….100
CHAPTER 10 ………………………………………………………………………………………………………………………………………………………..…101
10.0 BIBLOGRAPHY……………………………………………………………………………………………………………………………………..…………..101

LIST OF FIGURES
Figure 1 : Layout of Thermal power plant
Figure 2.1( a) : Rankine cycle
Figure 2.1(b) : T-S diagram
Figure 2.1 (c) : P-V diagram
Figure 2.2 (a) : Regenerative cycle
Figure 2.2 (b) : T-S diagram
Figure 2.3 (a) : Reheat cycle
Figure 2.3 (b) : T-S diagram
Figure 2.3.2 : Line diagram of 210 MW thermal power plant
Figure 2 .6(a) : Single steam cycle diagram
Figure 2.6 (b) : Heat balance diagram
Figure 3.1 (a) : Thermal energy
Figure 5.2.1 : Fire tube boiler
Figure 5.2.2 : Water tube boiler
Figure 5.3 : Super-heater
Figure 5.4.1.3 : Condenser
Figure 5.5.1 : Jet condenser
Figure 5.6.2 : Cooling water operation
Figure 5.7.1 : Natural draught cooling tower
Figure 5.7.2 : Induced draught cooling tower
Figure 5.7.3 : Dry cooling tower system

Figure 5.9 (a) : Ejector line diagram
Figure 5.9(b) : Ejector
Figure 5.10.1 : Low pressure feed-heaters
Figure 5.13(a) : Boiler feed pump
Figure 5.14(a) : Economizer line diagram
Figure 5.14 (b) : Economizer
Figure 5.16 : Boiler Re-heater

LIST OF TABLES
Table 1.5.1 : Power generation data
Table 4.3 : Heat rate values
Table 6.1.1 : Enthalpy and entropy values of components
Table 6.2.1 : Thermodynamic extractions at turbines
Table 6.3 : High pressure Turbine
Table 6.4 : Intermediate pressure turbine
Table 6.5 : Low pressure turbine
Table 7.3.1 : First law and second law efficiencies
Table 7.3.2 : Energy and exergy losses
LIST OF GRAPHS
Graph 8.1 : Exergy destruction
Graph 8.2 : Turbine exergy efficiency and destruction
Graph 8.3 : Exergy vs energy efficiency
Graph 8.4 : Comparison charts

ABSTRACT
EXERGY ANALYSIS OF THERMAL POWER PLANT (RTPP)
The energy supply to the demand narrowing down day by
day around the world, the growing demand of the power has made the power plants of scientific
interest, but most of the power plants are designed by the energetic performance criteria based on
the first law of thermodynamics only. The real useful energy loss cannot be identified by the first
law of thermodynamics, because it does not differentiate between the quality and quantity of
energy. The project on Exergy Analysis was undertaken on Rayalaseema Thermal Power
Project located in Kadapa, Andhra Pradesh. The capacity of the plant is 5×210 MW.
Energy analysis presents only quantities results while
Exergy analysis presents qualitative results about actual energy consumption. The main objective
is to analyze the system components separately and to identify and quantify sites having largest
energy and exergy efficiency losses . It also presents major losses of available energy at super-
heater, boiler and turbine section. Exergy destruction and energy loss comparison charts are
drawn for different components. The results are tabulated and graphs are plotted to show
correlation between various parameters. This project would also throw light on the scope for
further research and recommendations for improvement in the further existing plant.

CHAPTER-1
1.0 INTRODUCTION TO R.T.P.P
1.1 General
Rayalaseema thermal power project (R.T.P.P),is one of the major generation
unit, developed in A.P., to meet the growing demand for power, the project envisaged the
installation of 2×210MW coal based thermal generation units under stage I. The first 210MW
unit for commercial operation was started on 25 Nov1994 and the second unit on 30 Mar 1995.
The plant has another 2 × 210MW coal based thermal generation units under stage II. In the
stage 2, the third Unit was started on 24 Jan 2007 and the fourth unit is under construction.
1.2 Location
The R.T.P.P. project is located at a distance of 8km from Muddunur railway
station of south central railway on Chennai-Mumbai railway line. The site is selected at an
adequate distance from the residential areas and it has an area of 2600 Acres. The water
requirements for the project are met from Mylavaram reservoir across river Penna, which is 23
KM away from the power plant.

1.2.1 LAYOUT OF THERMAL POWER PLANT
Figure 1.0 Layout of Thermal power plant

1.3 Raw material
1.3.1 Coal:
The project gets its coal from singareni collieries by wagons. The coal used
in R.T.P.P. is bituminous coal. It is similar to lignite and contains 50% less moisture than lignite.
It also contains less ash than lignite and it is used either in the form of pulverized or briquettes
state. The coal from singareni is of inferior quality with ash average content varying between
45%-50%. The uncrushed coal is stocked in stockyard and crushed coal in separate yard.
1.3.2 Furnace oil and diesel oil:
Light diesel oil is used for firing and heavy furnace oil is used for flame
support and stabilization. Storage capacity: Heavy furnace oil: two tanks of 4150 kilo liter each.
Light diesel oil: two tanks of 800 kilo liter each.
1.3.3 Water:
The water requirement of the project is met from Mylavaram reservoir and
Brahma sagar dam across Penna River situated at a distance of 23 KM. A gravity pipeline is laid
to draw 25 cusecs of water from the reservoir.
1.4 Combustion Process
Pulverized coal after burning in furnace generates ash, out of which 20%
ash will be bottom ash and 80%will be fly ash. The combustion product of furnace is let into the
electro static precipitators to entrap dust and gases emission is let into the atmosphere through
220mt chimney.
1.5 Operational Data
The project has faced some troubles during construction, testing and
commissioning. After some modification and alterations, tremendous improvement in
availability and plant load factor was achieved during the last three years at R.T.P.P. The year
wise operations from 1995 onwards show the performance details of the plant and are given in
table below.

1.5.1 POWER GENERATION DATA:
Year Generation(MW) P.L.F (%) Achievements
1994-1995
1995-1996
1996-1997
1997-1998
1998-1999
1999-2000
2000-2001
2001-2002
2002-2003
2003-2004
2004-2005
2005-2006
2006-2007
2007-2008
2008-2009
2009-2010
2010-2011
2011-2012
2012-2013(feb)
1327.5041
2436.5355
2982.5728
3365.0559
3500.3542
3475.3821
3400.8030
3488.8235
3401.5830
3353.782
3095.562
3300.568
3293.670
3146.896
3357.265
3365.0559
3466.0559
3293.670
2436.5355
53.25
66.2
81.07
91.46
94.88
94.46
92.43
94.83
92.20
91.16
84.45
90.98
89.52
85.30
91.25
87.83
93.02
90.32
93.45
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Gold medal
Gold medal
Gold medal
All India first
All India first
Gold medal
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−
_
Silver medal
_
−
−
−

CHAPTER-2
2.0 WORKING CYCLES
The fundamental forms of energy with which thermal stations are
principally concerned are heat and work. Heat produces work and this work is further converted
into electrical energy through a medium .i.e. electrical generator. For the purpose of
understanding of thermal plants, the phenomenon of thermodynamics vapor power cycles is
explained here under:
1. Rankine cycle
2. Regenerative cycle
3. Reheat cycle
2.1 Rankine cycle:
Rankine cycle is theoretical cycle on which steam turbine (or engine)
works.
Fig.2.1(a) Rankine cycle

Fig.2.1(b) T-S Diagram Fig.2.1(c) P-V Diagram
It comprises of following process:
Process1-2: Reversible adiabatic or isentropic expansion in the turbine
Process2-3: Constant pressure condensation or heat rejection process
Process3-4: Isentropic pumping process in the feed pump.
Proces4-5: Constant pressure heat supplied in the boiler.
2.1.1 Effect of operating conditions on Rankine cycle efficiency
The Rankine cycle efficiency can be improved by increasing average
temperature at which heat is supplied, decreasing or reducing the temperature at which heat is
rejected. This can be achieved by making suitable changes in the condition of steam generation
or condensation, as discussed below:
2.1.2 Increasing boiler pressure
By increasing the boiler pressure the cycle tends to raise and reach
maximum value at a boiler pressure about 166bar.
2.1.3 Super heating
If the steam is superheated before allowing it to expand, the Rankine
cycle efficiency may be increased. The use of superheated steam also ensures longer turbine
blade life because of the absence of erosion from high velocity water particles that are suspended
in wet vapor.

2.1.4 Reducing condenser pressure
The thermal efficiency of the cycle can be improved by reducing the
condenser pressure, especially in high vacuum. But the increase in efficiency is obtained at the
increased cost of condensation apparatus. The thermal efficiency of the Rankine cycle is
improved by the following methods.
1 By regenerative feed heating.
2. By reheating of steam.
3. By water extraction.
4. By using binary vapor.
2.2 REGENERATIVE CYCLE
In the Rankine cycle it is observed that the condensate, which is fairly
at low temperature, has an irreversible mixing with hot boiler water and this result in decrease of
cycle efficiency. Methods are therefore adopted to heat the feed water from the hot well of
condenser irreversibly by interchanging of heat with in the system and thus improving the cycle
efficiency. This heating method is called regenerative feed heat and the cycle is called
regenerative cycle.
The principle of regeneration can be practically utilized by extracting
steam from turbine at several locations and supply it to the regenerative heater. The most
advantageous condensate heating temperature is selected depending on the throttle conditions
and this determines the number of heaters to be used. Figure shows the layout of condensing
steam power plant in which a surface condenser is used to condense all the steam that is not
extracted for feed water heating. The turbine is double extracting and boiler is equipped with a
super heater.

. Fig.2.2(a) Regenerative cycle
Fig:2.2(b) T-S DIAGRAM
M1=mass of high pressure steam extracted for HP heater per kg of steam flow
M2= mass of low pressure steam extracted for LP heater per kg of steam flow
1-M1-M2=mass of steam entering into the condenser per kg of steam flow.
2.2.1 Advantages of regenerative cycle
 The heating process in the boiler tends to become reversible.
 The thermal stresses set up in the boiler are minimized this is due to the fact that
temperature ranges in the boiler are reduced.
 The thermal efficiency is improved because the average temperature of heat addition to
the cycle is increased.

2.3 REHEAT CYCLE
Fig:2.3(a) REHEAT CYCLE
The efficiency of the ordinary Rankine cycle can be improved by increasing
the pressure and temperature of the steam entering into the turbine. As the initial pressure
increases, the expansion ratio in the turbine also increase and the steam become quite wet at the
end of expansion. This is not desirable because the increased moisture content of steam causes
corrosion of turbine blades and increases losses. This reduces the efficiency.
In reheat cycle the steam is extracted from a suitable point in the turbine
and is reheated it with the support of flue gases in the boiler furnace. The main purpose of
reheating to increase the dryness fraction of steam passing through the lower stages of the
turbine. The increase in thermal efficiency due to reheat depends upon the ratio of reheat
pressure to the original pressure of steam. The main advantage of the reheat cycle is to reduce the
specific steam consumption and consequently reduces the size of the boiler and auxiliaries for
the same output.
Fig.2.3(b).T-S Diagram

Process 1-2: Expansion of steam in high –pressure turbine
2-3: Reheating of steam in a boiler
3-4: Expansion of steam in low –pressure turbine
4-5: Condensation process in the condenser
5-6: Pump wok
6-1: Heat supplied to the boiler
2.3.1 Advantages of reheating
 There is an increased output of the turbine
 Erosion and corrosion problems in the steam turbine are eliminated.
 There is an improvement in the thermal efficiency of the turbines.
 Final dryness fraction of the steam is improved.
 There is an increase in the nozzle and blade efficiency.

2.3.2 LINE DIAGRAM OF 210 MW THERMAL POWER PLANT
Figure 2.3.2 Line Diagram of 210 MW Thermal power plant

2.4 Typical values of efficiency
Thermal efficiency = 30 to 40 %
Steam generator (boiler) efficiency = 75 to 90 %
Thermal cycle efficiency = 35 to 50 %
Internal efficiency of the turbine = 85 to 94 %
Mechanical efficiency of turbine = 99 to 99.5%
Generator efficiency = 68 to 98.5%
2.5 FACTORS FOR INCREASING THE THERMAL CYCLE EFFICIENCY
Thermal cycle efficiency is affected by following factors
 Initial steam pressure
 Initial temperature
 Whether reheat is used or not ,and if used reheat pressure and temperature
 Regenerative feed water- heating
2.5.1 INITIAL STEAM PRESSURE
At constant initial steam temperature, increase in initial steam
pressure ,means increase in saturation temperature of feed water or increase in mean temperature
at which heat is added to cycle .this will result in increase in thermal cycle efficiency. With
increase in the initial steam pressure at constant temperature and constant condenser pressure,
wetness of steam in the last stage of turbine increases, there by reducing internal efficiency of
these stages. Usually 1% moisture in the steam in particular stage results in 0.9 to 1.2%
reduction. Erosion becomes so severe that life of turbine is endangered .With increase in initial
steam pressure, blade height of initial stages gets reduced. If blade height of initial stage blades
are less than 25mm, this stage becomes very inefficient due to three dimensional flow and vortex
formation etc.some times this problem is overcome by partial admission in first or first few
stages.
2.5.2 INITIAL STEAM TEMPERATURE
As initial temperature increases, the thermal cycle efficiency
increases and hence from thermodynamics there is no upper limit for initial temperature.
Material considerations do restrict the initial steam temperature up to 400oC plain carbon steel
can be used and up to 480 oC low alloy steels can be used.

Above 480 oC and up to 600 oC heat resistant ferritic steels can be used
.It gives limiting value of initial steam temperature to be 565 oC .
During operation of power plants, it was found that plant outages due to boiler failure with initial
steam temperature 565 oC were enormous as compared with initial steam temperature 535 oC.
Now-a-days, practical limit for initial steam temperature is 535 oC to 540 oC. Above 540 oC
temperature, austenitic steels could be used, which have coefficient of thermal expansion and
lower thermal conductivity but poor machinability and weldability as compared to ferritic steels.
For these reasons use of austenitic steels is not preferred.
2.5.3 REHEAT
Reheating the steam after it as partially expanded, improves the
thermal cycle efficiency by 4% to5% as a more efficient cycle is added to original cycle. Reheat
reduces moisture in the last stage of turbine, the re by improving the internal efficiency of the
turbine. Reheating invariably complicates design of turbine, steam generators and their controls.
If the pressure drop in re-heater is more than 12-15%, almost all increase in efficiency is offset
by it.
2.5.4 CONDENSER PRESSURE
Condenser has a triple function in Rankine cycle, first is providing
heat sink, second is to provide very low vacuum and third is to preserve working fluid. Lower
condenser pressure implies lower mean temperature at which heat is rejected to sink, thereby
increasing the thermal efficiency cycle.
Condenser pressure is dependent on cooling water temperature and
to certain extent on cooling water flow rate. Since cooling water is usually taken from river, lake
or sea whichever is near by to thermal plant, we do not really have control on cooling water
temperature and hence on condenser pressure. In India, cooling water temperature usually ranges
between 24 oC to 36 oC giving condenser pressure of 0.06 to 0.12.ata
2.5.5 REGENERATIVE FEED WATER HEATING
In regenerative feed water heating part of steam is extracted after
partial expansion in the turbine and is used to heat up the feed water going to steam generator
(boiler). In this process the latent heat of liquidification of extracted steam is also utilized in
heating feed water, which otherwise would have been dumped in to the condenser, there by
increasing the cycle efficiency.

2.6 PLANT LOSSES
By fact the largest turbine house loss is the heat carried away in the
circulating water passing through the condenser .Figure shows a heat balance diagram for the
complete process of generation in the power generation in the power station .this simplified form
of heat balance in practice, when a test is carried out the losses are subdivided and circulated in
much greater detail than shown in the diagram. It does, however, show where the principle losses
occur and enable the question of efficiency to be studied more closely. The aim is to keep the
losses as small as possible by good operation.
Fig.2.6(a) Simple Steam Cycle Diagram
Fig.2.6(b) Heat Balance diagram

CHAPTER-3
3.0 INTRODUCTION TO EXERGY
3.1 Energy
The word energy derives from the Greek ἐνέργεια energeia, which possibly
appears for the first time in the work of Aristotle in the 4th century BCE.
Energy is defined as the ability to do work.
In the context of chemistry, energy is an attribute of a substance as a consequence of its atomic,
molecular or aggregate structure.
In biology, energy is an attribute of all biological systems from the biosphere to the smallest
living organism.
Internal energy is the sum of all microscopic forms of energy of a system.
Heat, a form of energy, is partly potential energy and partly kinetic energy. In the context of
physical sciences, several forms of energy have been defined. These include
 Chemical energy
 Electric energy
 Radiant energy, the energy of electromagnetic
radiation
 Nuclear energy
 Magnetic energy
 Elastic energy
 Sound energy Fig: 3.1(a) THERMAL ENERGY
 Thermal energy
 Mechanical energy
 Luminous energy
 Mass (E=mc²)
These forms of energy may be divided into two main groups; kinetic
energy and potential energy. Other familiar types of energy are a varying mix of both
potential and kinetic energy, Energy may be transformed between different forms at
various efficiencies.

3.1.1Unit of Measure:
The energy is a scalar physical quantity. Joule is the (SI) unit of
measurement for energy. It is a derived unit of energy, work, or amount of heat. It is equal to the
energy expended (or work done) in applying a force of one newton through a distance of one
meter. However energy is also expressed in many other units such as ergs, calories, British
Thermal Units, kilowatt-hours and kilocalories for instance. There is always a conversion factor
for these to the SI unit; for instance; one kWh is equivalent to 3.6 million joules.
3.2 Exergy:
The term availability was made popular in the united states by the M.I.T.
school of engineering the 1940’s. Today, an equivalent term, exergy, introduced in Europe in the
1950’s, has found global acceptance partly because it is shorter, it rhymes with energy and
entropy, and it can be adapted without requiring translation. In this text the preferred term is
exergy. Exergy is now recognized that it is an extremely fruitful theory. Exergy accounting is the
only way to accurately calculate the thermodynamic losses of a given process and to
unambiguously define a thermodynamic efficiency expressing its level of perfection. It also
allows for the evaluation of the thermodynamic quality of an energy system when considering
energy policies and economics, independent of the size, complexity and the nature of the
phenomena being looked at. That is why we devote particular care to exergy theory and to its
generalization.
. The quantity exergy is defined as:
The amount of work which can be received from an energy carrier in a process that:

 takes place in an open system with stationary flow.

 th the environment at the end of the process.
The property exergy is the work potential of a system in a specified
environment and the maximum amount of useful work that can be obtained as the system is
brought to equilibrium with the environment. Unlike energy, the value of exergy depends on the
state of the environment as well as the state of the system. Therefore, exergy is a combination
property. The exergy of a system that is in equilibrium with its environment is zero. The state of
the environment is referred to as the “dead state” since the system is practically “dead” from a
thermodynamic point of view when it reaches that state. A system must go to the dead state at

the end of the process to maximize the work output can be explained as follows: if the system
temperature at final state is greater than (or less than) the temperature of the environment it is
in, we can always produce additional work by running a heat engine between these two levels.
If the final pressure is greater than the pressure of environment, we can
still obtain work by letting the system expand to the pressure of environment. If the final
velocity of the system is zero. We can catch that extra kinetic energy by a turbine and convert it
to rotating shaft work, and so on. No work can be produced from a system that is initially at the
dead state. The atmosphere around us contains a tremendous amount of energy. However, the
atmosphere is in the dead state, and the energy it contains has no work potential. Therefore, we
conclude that a system delivers the maximum possible work as it undergoes a reversible process
from the specified initial state to the state of its environment, that is, the dead state. This
represents the useful work potential of the system at the specified state and is called exergy. It is
important to realize that exergy does not represent the amount of work that a work-producing
device will actually deliver up on installation. Rather, it represents the upper limit on the amount
of work a device can deliver without violating any thermodynamic laws. There will always be a
difference, larger or small, between exergy and the actual work delivered by a device.
At a time weighted with increasing concerns about the present and future
energetic, environmental and geopolitical challenges, it is particularly vital to prioritize our
technological choices towards a more rational use of our non-renewable as well as our renewable
resources. This implies improvements of both our methodological and technological tools. From
the methodological viewpoint a more rational and sustainable use of the available resources is
only possible if engineers, architects, industrialists and decision makers can rely on coherent
indicators among which the exergy efficiency is bound to play a major role. It is rather
disappointing that in this beginning of the 21st century a major part of the practitioners are still
using only performance indicators based exclusively on the First Law of thermodynamics. For
example, simple boilers for house heating are labelled with efficiencies very close to 100%
(apparent perfection!), while it is technologically possible, with each same unit of fuel, to
provide about twice as much heat. Conversely, the exergy efficiency allows a coherent ranking
of the technical options, with values always below 100%, independent of the domain and the
energy service supplied. From a technological standpoint, the notion of exergy also allows a

better characterization of the sources of internal losses, and therefore leads to better target
designs and retrofitted projects.
Exergy analysis is a tool for identifying the types, locations and
magnitudes of thermal losses. Identification and quantification of these losses allows us to
evaluate and improve the design of thermodynamic systems. Although the amount of energy
remains constant, our ability to use the energy decreases with time. In other words, the energy in
the system at the initial state has a greater potential for use than at the final state. Due to the
irreversibility’s occurring during this process, the energy's potential for use or the system's
exergy is reduced. Exergy is defined as the maximum theoretical work obtainable as the system
interacts with its surroundings and comes to equilibrium. Once a system is in equilibrium with its
surroundings, it is not possible to use the energy within the system to produce work. At this
point, the exergy of the system has been completely destroyed. The state in which the system is
in equilibrium with its surroundings is known as the dead state.
Recall that the exergy of a system is maximum amount of work that can
be obtained from a system. In order to quantify the exergy of a system, we must specify both the
system and the surroundings. The exergy reference environment is used to standardize the
quantification of exergy. The exergy reference environment or simply the environment is
assumed to be a large, simple compressible system. The temperature of the environment is
assumed to be uniform at to, and the pressure is assumed to be uniform at Po. Also, it is assumed
that the intensive properties of the environment are not significantly changed by any process.
Therefore, the environment is modeled as a thermal reservoir at To.
The work produced by a system cannot all be used for the desired
purpose. For example, when the gas in the piston cylinder device is expanding, some of the work
is required to compress the environment. We define environment work as the work done on or by
the environment. Since the environment is a simple compressible system and the pressure of the
environment is constant.
In thermodynamics, the exergy of a system is the maximum useful
work possible during a process that brings the system into equilibrium with a heat reservoir.
When the surroundings are the reservoir, exergy is the potential of a system to cause a change as
it achieves equilibrium with its environment. Exergy is the energy that is available to be used.
After the system and surroundings reach equilibrium, the exergy is zero. Energy is never

destroyed during a process; it changes from one form to another (see First Law of
Thermodynamics). In contrast, exergy accounts for the irreversibility of a process due to increase
in entropy (see Second Law of Thermodynamics). Exergy is always destroyed when a process
involves a temperature change. This destruction is proportional to the entropy increase of the
system together with its surroundings. The destroyed exergy has been called anergy For an
isothermal process, exergy and energy are interchangeable terms, and there is no anergy.
Exergy analysis is performed in the field of industrial ecology to use
energy more efficiently. The term was coined by Zoran Rant in 1956, but the concept was
developed by J. Willard Gibbs in 1873. Ecologists and design engineers often choose a reference
state for the reservoir that may be different from the actual surroundings of the system. Exergy is
a combination property of a system and its environment because unlike energy it depends on the
state of both the system and environment. The exergy of a system in equilibrium with the
environment is zero. Exergy is neither a thermodynamic property of matter nor a thermodynamic
potential of a system.
Exergy and energy both have units of joules. The Internal Energy of a
system is always measured from a fixed reference state and is therefore always a state function.
Some authors define the exergy of the system to be changed when the environment changes, in
which case it is not a state function. Other writers prefer a slightly alternate definition of the
available energy or exergy of a system where the environment is firmly defined, as an
unchangeable absolute reference state, and in this alternate definition exergy becomes a property
of the state of the system alone. The term exergy is also used, by analogy with its physical
definition, in information theory related to reversible computing. Exergy is also synonymous
with: availability, available energy, exergic energy, essergy (considered archaic), utilizable
energy, available useful work, maximum (or minimum) work, maximum (or minimum) work
content, reversible work, and ideal work.
The exergy destruction of a cycle is the sum of the exergy destruction
of the processes that compose that cycle. The exergy destruction of a cycle can also be
determined without tracing the individual processed by considering the entire cycle as a single
process and using one of the exergy destruction equations. ---Information found in
thermodynamics by Yunus A. Cengel

3.3 Application of the second law of thermodynamics
Exergy uses system boundaries in a way that is unfamiliar to many.
We imagine the presence of a Carnot engine between the system and its reference environment
even though this engine does not exist in the real world. Its only purpose is to measure the results
of a "what-if" scenario to represent the most efficient work interaction possible between the
system and its surroundings.
If a real-world reference environment is chosen that behaves like an
unlimited reservoir that remains unaltered by the system, then Carnot's speculation about the
consequences of a system heading towards equilibrium with time is addressed by two equivalent
mathematical statements. Let B, the exergy or available work, decrease with time, and Stotal, the
entropy of the system and its reference environment enclosed together in a larger isolated
system, increase with time.
3.3.1 Engineering applications
Application of exergy to unit operations in chemical plants was
partially responsible for the huge growth of the chemical industry during the 20th century.
During this time it was usually called availability or available work. As a simple example of
exergy, air at atmospheric conditions of temperature, pressure, and composition contains energy
but no exergy when it is chosen as the thermodynamic reference state known as ambient.
Individual processes on Earth like combustion in a power plant often eventually result in
products that are incorporated into a large atmosphere, so defining this reference state for exergy
is useful even though the atmosphere itself is not at equilibrium and is full of long and short term
variations.
If standard ambient conditions are used for calculations during plant
operation when the actual weather is very cold or hot, then certain parts of a chemical plant
might seem to have an exergy efficiency of greater than 100% and appear on paper to be a
perpetual motion machine! Using actual conditions will give actual values, but standard ambient
conditions are useful for initial design calculations .One goal of energy and exergy methods in
engineering is to compute what comes into and out of several possible designs before a factory is
built. Energy input and output will always balance according to the First Law of
Thermodynamics or the energy conservation principle.

Exergy output will not balance the exergy input for real processes
since a part of the exergy input is always destroyed according to the Second Law of
Thermodynamics for real processes. After the input and output are completed, the engineer will
often want to select the most efficient process. An energy efficiency or first law efficiency will
determine the most efficient process based on wasting as little energy as possible relative to
energy inputs. An exergy efficiency or second-law efficiency will determine the most efficient
process based on wasting and destroying as little available work as possible from a given input
of available work. Design engineers have recognized that a higher exergy efficiency involves
building a more expensive plant, and a balance between capital investment and operating
efficiency must be determined in the context of economic competition.
3.3.2 Quality of energy types
The ratio of exergy to energy in a substance can be considered a
measure of energy quality. Forms of energy such as macroscopic kinetic energy, electrical
energy, and chemical Gibbs free energy are 100% recoverable as work, and therefore have an
exergy equal to their energy. However, forms of energy such as radiation and thermal energy can
not be converted completely to work, and have exergy content less than their energy content. The
exact proportion of exergy in a substance depends on the amount of entropy relative to the
surrounding environment as determined by the Second Law of Thermodynamics. Exergy is
useful when measuring the efficiency of an energy conversion process. The exergetic, or
2nd Law, efficiency is a ratio of the exergy output divided by the exergy input. This formulation
takes into account the quality of the energy, often offering a more accurate and useful analysis
than efficiency estimates only using the First Law of Thermodynamics.
Work can be extracted also from bodies colder than the
surroundings. When the flow of energy is coming into the body, work is performed by this
energy obtained from the large reservoir, the surrounding. A quantitative treatment of the notion
of energy quality rests on the definition of energy. According to the standard definition, Energy
is a measure of the ability to do work. Work can involve the movement of a mass by a force that
results from a transformation of energy. If there is an energy transformation, the second principle
of energy flow transformations says that this process must involve the dissipation of some energy
as heat. Measuring the amount of heat released is one way of quantifying the energy, or ability to
do work and apply a force over a distance.

However, it appears that the ability to do work is relative to the
energy transforming mechanism that applies a force. This is to say that some forms of energy
perform no work with respects to some mechanisms, but perform work with respects to others.
For example, water does not have a propensity to combust in an internal combustion engine,
whereas gasoline does. Relative to the internal combustion engine, water has little ability to do
work that provides a motive force.
If “energy” is defined as the ability to do work then a consequence
of this simple example is that water has no energy — according to this definition. Nevertheless,
water, raised to a height, does have the ability to do work like driving a turbine, and so does have
energy.
This example means to demonstrate that the ability to do work can be
considered relative to the mechanism that transforms energy, and through such a conversion
applies a force. From this observation we might wish to use the word “quality”, and the term
“energy quality” to characterize the energetic differences between substances and their
propensities to perform work given a specific mechanism. That is the abilities of different energy
forms to flow and be transformed in certain mechanisms. With this lexicon, we can say that
energy quality is mechanism-relative, and the energy efficiency of a mechanism is energy
quality-relative – an internal combustion engine running on water has nearly 0% efficiency since
it has the propensity to transform little or no water-energy into thermal-energy. In order to clarify
things here we might think of this as the “water-efficiency”. The mechanism of interest is also
our system of reference, such that the choice of energy quality specifies a certain system of
reference. Thus with respects to the internal combustion system of reference, it has a low “water-
efficiency”.
3.4 WORKDONE
Work done during a process depends on its initial state, final state, and
the process itself. That is, work = f(initial state, process, final state)If the initial state has been
specified, then work is only a function of process and the final state. Previously, it was shown
that reversible process between two selected states gives the maximum work output.
System exchanges work, heat, and mass with its surroundings during a process. If the system
reaches a state which is in equilibrium with its surroundings, then the system can not exchanges
work, heat, and mass with its surroundings. This state is called a dead state and its properties are

denoted by subscript 0, such as pressure P0 and temperature T0. At the dead state: A system is at
the same temperature and pressure of its surroundings. It has no kinetic or potential energy
relative to its surroundings. It does not react with the surroundings. There are no unbalanced
magnetic, electrical and surface tension effects between the system and its surroundings.
For example, gas expands in a cylinder to do work on its surroundings. If
the pressure in the cylinder reaches the pressure in its surroundings, no more work can be done
by the cylinder. That means the cylinder reaches its dead state, and the work done by this
cylinder reaches its maximum value. Therefore, a system will deliver the maximum possible
work if it undergoes a reversible process from the specified initial state to its dead state. This
work represents the useful work potential of the system at the specified initial state and is called
exergy of the specified initial state.
3.4.1 REVERSIBLE WORK
Wrev (reversible work): the maximum amount of useful work that
can be produced (or the minimum work that needs to be supplied) as a system undergoes a
process between the specified initial and final states. This is the useful work output obtained,
when the process between the initial and final states is executed in a totally reversible
manner. When the final state is the dead state, the reversible work equals exergy.
3.4.2 IRREVERSIBLE WORK
Irreversible work or Irreversibility is defined as the difference
between the reversible work and the useful work. It is expressed as
I = Wrev,out - Wu, out or I = Wu, in - Wrev,in
Where Wrev is the reversible work and Wu is the useful work. The
definitions of reversible work and the usefully work are given below. When gas expands in a
cylinder to do work, it needs to expend some work on pushing the atmospheric air out of the
way. This part of work cannot be recovered and utilized, and is called surrounding work, which
is the work done by or against the surroundings during a process.
Reversible work is defined as the maximum amount of useful work that
can be produced (or the minimum work consumed) as a system undergoes a process between the
specified initial and final states. A system can contain energy in numerous forms such as kinetic
energy, potential energy, internal energy, flow work and enthalpy.

Exergy is the useful work potential of energy, and the exergy of a system is
the sum of the exergies of different forms of energy it contains.
3.5 THE LAWS OF THERMODYNAMICS
Energy can neither be created nor destroyed, In all energy
transformations, energy quality will be consumed .These are Natural Laws, i.e. they are
fundamental and cannot be negotiated. On the other hand, if somebody find out something that
might falsify them, they will cease to be fundamental.
The First Law tells us that energy can be neither created nor
destroyed.(The production or consumption of energy is impossible. Anyone who speaks about
'energy production’ or 'energy consumption' is probably ignorant about the First Law). This
means that the amount of energy in the universe is constant. So, the First Law tells us something
about the state of the universe and all processes in it.
The Second Law tells us that the quality of a particular amount of
energy i.e. the amount of work, or action, that it can do, diminishes for each time this energy is
used. This is true for all instances of energy use, physical, metabolic, interactive, and so on.
This means that the quality of energy in the universe as a whole, is constantly diminishing. All
real processes are irreversible, since the quality of the energy driving them is lowered for all
times.
Thus, the Second Law tells us about the direction of the universe and all
processes, namely towards a decreasing exergy content of the universe. Processes that follow this
general principle will be preferred. Some people seem to think that this law should be revoked...
But perhaps they are misled by their notion of entropy. The usable energy in a system is called
exergy, and can be measured as the total of the free energies in the system. Unlike energy,
exergy can be consumed.
To more easily understand the concept
of exergy, you can consider this picture as an analogy:
Likewise we can’t extract paste completely from a
tube we can’t utilize energy completely from a source
means there must be some losses during the process
or a work being done and most of the losses is due to entropy which we can’t avoid completely.

Furthermore, it is not defined in far-from-equilibrium systems, as living
systems and other organized systems. The first law of thermodynamics was stated in terms of
cycles first and it was shown that the cyclic integral of heat is equal to the cyclic integral of
work. When the first law was applied for thermodynamic process, the existence of a property,
the internal energy was found. Similarly, the second law was also first stated in terms of cycles
executed by systems. When applied to process, the second law also leads to the definition of a
new property, known as entropy. If first law is said to be the law of internal energy, then second
law may be stated to be the law of entropy. In fact, thermodynamics is the study of three E’s,
namely, energy, equilibrium and entropy.
3.6 LAW OF DEGRADATION OF ENERGY
The available energy of a system decreases as its temperature or
pressure decreases and approaches that of the surroundings. When heat is transferred from a
system, its temperature decreases and hence the quality of its energy deteriorates.
The degradations more for energy loss at a higher temperature than that at a lower temperature.
Quantity wise the energy loss may be the same, but quality wise the losses are different. While
the first law states that energy is always conserved quantity wise , the second law emphasizes
that energy always degrades quality wise. When a gas is throttled adiabatically from a high to a
low pressure , the enthalpy(or energy per unit mass) remain the same, but there is a degradation
of energy or available work.
The same holds good for pressure drop due to friction of a fluid
flowing through an insulated pipe. If the first law is the law of conservation of energy, the
second law is called the law of degradation of energy. Energy is always conserved, but its
quality is always degraded.

CHAPTER-4
4.0 DATA COLLECTION
The following data is collected for calculation of heat rate and
performance of steam turbine and heat balance of regenerative cycles.
4.1 Technical data of 210 MW Turbine
Main steam pressure = 150 kg/cm2
Main steam temperature = 535 oC
Reheat steam temperature = 535 oC
Full load steam flow = 641 TPH
Back pressure range = 0.03 ata to 0.12 ata
No. of extractions = 6
No. of stages High Pressure Turbine = 1X25
Intermediate Pressure Turbine = 2X20
Low Pressure Turbine = 2X8
Last stage blade height = 661.4 mm
Over all length = 16.175 meter
Width = 10.6 meter
Weight of the turbine = 480 tons
Frequency band = 47.5 to 51.5 HZ
Pressure & Temp variations AS per IEC recommendations
4.2 GENERAL DATA
4.2.1 CONSTRUCTION
Three-cylinder reheat condensing turbine
Single-flow HP turbine with 25 reaction stages Type H30-25-2
Double –flow IP turbine with 20 reaction stages per flow Type M30-20
Double –flow LP turbine with 8 reaction stages per flow Type N30-2×5
2 Main stop and control valve Type EV 160

2 Reheat stop and control valves Type IV320
2swing check valves in cold reheat line DN450
2Bypass stop and control valves DN200
Extraction swing check valves
Extraction 1: No valve
Extraction 2: swing check valve with auxiliary actuator, 1 swing check valve
Extraction 6: No valve
4.2.3 SPEED CYCLE/SEC
Rated speed 50cycles/s ~ 3000 RPM
4.2.4 STEAM PRESSURES: In bar
Initial steam 147
Before 1st HP drum stage 132.6
HP cylinder exhausts 39.23
IP cylinder stop valve inlet 34.13
Extraction 6(HPH-6) 39.23
Extraction 5(HPH-5) 16.75
Extraction 4(D/A) 7.06
Extraction 3(LPH-3) 2.37
LP cylinder exhausts 0.1187

4.2.5 STEAM TEMPERATURES: In oC
Initial steam 535
IP cylinder stop value inlet 535
HP cylinder exhausts 343
Extraction 6 343
Extraction 5 433
Extraction 4 316
Extraction 3 200
Extraction 2 107
Extraction 1 62
LP cylinder exhausts 49

4.3 HEAT RATE VALUES
S.
N
O
DESCRIPTION UNIT DESI
GN
VAL
UES
UNIT
-1
FULL
LOA
D
UNIT-1
PART
LOAD
UNIT
-2
FULL
LOA
D
UNIT
-2
PAR
T
LOA
D
1 Load MW 210 212.0 197.3 215.5 180
2 Feed water flow(Hr avg) TPH 636.7
4
703.1 656.7 718.8 628.6
3 RH spray TPH 0 9.6 0.0 18.1 1.8
4 Main steam flow TPH 636.7
4
670.6 642.4 672.2 562.1
5 Main steam pressure before
strain
Kg/c
m2
150 152.1 148 152.1 153.1
6 Main steam temp before
Esv1/Esv2
oC 535 537.6 536.2 536.5 537.4
7 HP turbine 1.stage balding
pressure
Kg/c
m2
134.2
3
133.2 125.9 132.6 114.9
8 CRH steam pressure at HPT
exhaust
Kg/c
m2
38.56 37.2 34.7 38.6 33.5
9 CRH steam temperature At HPT
exhaust
oC 342.4 342.8 339.3 345.2 333.5
1
0
HRH steam pressure at IPT inlet Kg/c
m2
35/36 36.1 33.7 37.5 32.6
1
1
HRH steam temperature at IPT
inlet
oC 535 540.7 535.4 536.4 536.6
1
2
LP turbine exhaust hood
temperature
oC 42.1 48.6 47.7 49.7 47.1

1
3
HPH 5 inlet feed water
temperature
oC 168 170.6 167.4 169.6 162.8
1
4
HPH 6 outlet feed water
temperature
oC 244.8 233.1 232.8 235.3 234.8
1
5
HPH 6 inlet feed water
temperature
oC 201.2 200.1 196.7 200.6 194.6
1
6
HPH 6 inlet feed water pressure Kg/c
m2
185.4
2
181.3 181.6 185.8 181.4
1
7
HPH 6 outlet feed water pressure Kg/c
m2
184.5
6
185.1 177.8 184.5 180.2
1
8
Economizer inlet feed water
temp(L/R)
oC 244.8 233.1 233.3 233.9 233.5
1
9
CW temp at condenser I/L-
O/L(L/R)
oC 27/36 29/39 29.2/38.
9
31.1/4
0
32/39.
4
2
0
Steam pressure at ejector nozzle Kg/c
m2
7.5 10.0 10.0 10.2 11
2
1
No 6 extraction steam pressure Kg/c
m2
36.91 37.1 34.6 34.7 33.6
2
2
No 6 extraction steam
temperature
oC 340.7 346.9 343.6 350.5 340.7
2
3
IP casing exhaust steam
temperature
oC 314.8 336.8 332.3 342.6 325.9
2
4
HPH 6 drip temperature oC 206 205.5 201.9 207.4 199.8
2
5
IP casing exhaust steam pressure Kg/c
m2
7.2 7.7 7.2 7.8 7.4

2
6
Steam temperature at ejector
nozzle
oC 200 199.8 198.7 266.7 217

CHAPTER-5
5.0 COMPONENTS ON WHICH ANALYSIS IS MADE
5.1 Boiler
A boiler is a closed vessel in which water or other fluid is heated. The
pressure vessel in a boiler is usually made of steel (or alloy steel), or historically of wrought iron.
Stainless steel is virtually prohibited (by the ASME Boiler Code) for use in wetted parts of
modern boilers, but is used often in super-heater sections that will not be exposed to liquid boiler
water. The source of heat for a boiler is combustion of any of several fuels, such as wood, coal,
oil, or natural gas. Electric steam boilers use resistance- or immersion-type heating elements.
Nuclear fission is also used as a heat source for generating steam, either directly (BWR) or, in
most cases, in specialized heat exchangers called "steam generators" (PWR). Heat recovery
steam generators (HRSGs) use the heat rejected from other processes such as gas turbines.
5.2 Types of Boilers inlet conditions
5.2.1 Fire Tube Boiler
In fire tube boiler, hot gases pass through
the tubes and boiler feed water in the shell side is converted into
steam. Fire tube boilers are generally used for relatively small
steam capacities and low to medium steam pressures. As a
guideline, fire tube boilers are competitive for steam rates up to
12,000 kg/hour and pressures up to 18 kg/cm2. Fire tube boilers
are available for operation with oil, gas or solid fuels. For
economic reasons, most fire tube boilers are nowadays of
“packaged” construction (i.e. manufacturers shop erected) for
all fuels.
Outlet conditions
Fig:5.2.1 FIRE TUBE BOILER

5.2.2 Water Tube Boiler
In water tube boiler, boiler feed water
flows through the tubes and enters the boiler drum. The circulated
water is heated by the combustion gases and converted into steam
at the vapor space in the drum. These boilers are selected when the
steam demand as well as steam pressure requirements are high as
in the case of process cum power boiler / power boilers.
5.3 Super heater
A super heater is a Fig:5.2.2WATER TUBE BOILER
device used to convert saturated steam or
wet steam into dry steam used in steam
engines or in processes, such as steam
reforming. A component of a boiler system
that heats the steam produced above its
saturation temperature to prevent it
condensing, and in case of a steam engine Fig: 5.3 SUPER HEATER
to improve its efficiency.
Superheated steam is steam at a temperature that is higher than its
vaporization (boiling) point at the absolute pressure where the temperature measurement is
taken; Saturated steam is, in contrast to superheated steam, steam that is in equilibrium with
heated water at the same pressure, i.e., it has not been heated past the boiling point for that
pressure. The main advantages of using a super heater are reduced fuel and water consumption
but there is a price to pay in increased maintenance costs. In most cases the benefits outweighed
the costs and super heaters were widely used. Without careful maintenance super-heaters are
prone to a particular type of hazardous failure in the tube bursting at the U-shaped turns in the
super-heater tube.

5.4 CONDENSER
When the steam has completed its work in the turbine and before it can
be returned to the boiler, it must be changed back into water. This is the duty the condenser must
perform as efficiency as possible and, for this reason, it is the largest and most important of the
heat exchangers in a power station. The heat in the exhaust steam cannot be converted into
mechanical energy and must be transferred from the steam to the cooling water. The way in
which the condenser carries describe in this lesson.
5.4.1 Principle of condenser:
5.4.1.1 Volume of steam:
If water is put into a closed and heated, a quantity of heat known as
sensible heat is required to bring the water to boiling point and if further heat is added to convert
the water into steam this is known as latent heat. The volume of the steam formed is far greater
than that of the water and consequently the pressure in the vessel rises. Thus the application of
the latent heat has caused an increase in pressure.
5.4.1.2 Removal of heat:
Now reverse the process and remove some heat by cooling the vessel.
During this cooling the latent heat is removed from the steam from which is reduced to water
with a consequently fall in pressure. This removal of latent heat happens on a very large scale in
a turbine condenser. Inlet conditions
5.4.1.3 Condenser pressure:
The condenser is an
airtight vessel where the steam exhaust from the
turbine is cooled and condenser. The
condensation is so complete that the pressure
inside the condenser is reduced below that of the
atmosphere and this condition is referred to as
vacuum in the condenser Fig: 5.4.1.3 Condenser

To maintain this low pressure condition it is essential that any air or
other incondensable gases, passing into the condenser with the steam must be continuously
removed and, in addition to condensing the steam, the condenser must separate these gases from
the steam for discharge by an ejected or air pump.
5.4.2 Purpose of condenser:
5.4.2.1 Saving of steam:
By using a condenser there is a big reduction in the amount of a steam
required to generate each unit of electricity. In a turbine without a condenser the lowest pressure
to which the steam can be expanded is that of the atmosphere. It can be said that in this case the
back pressure against which the steam is exhausted is atmospheric pressure. Atmospheric
pressure is equivalent to the pressure which would support a column of mercury approximately
30 inches high. This is usually abbreviated to 30 inches Hg. being the chemical symbol for
mercury.
If the last stage of the turbine were under vacuum and the back pressure
reduced by a condenser to 2 inches Hg. Then the steam would be able to continue its expansion
from 30 inches Hg. Down to 2 inches Hg during this expansion each pound of steam is capable,
in a 9000lb/in2 turbine with a back pressure of 1.5 inches Hg the steam dose nearly 30% of its
work as it expand below atmospheric pressure. Thus the use of a condenser brings a considerable
saving.
5.4.2.2 Conservation of pure feed water:
Very large quantities of steam pass through a turbine, for example, a
500 MW machine on full load uses over 3,000,000 lbs/hr. it would, of course, be not only very
wasteful but impracticable to allow this vast amount of steam to be exhausted to a atmosphere.
By using a condenser the exhaust steam is changed back to water which is removed from the
condenser for continuous use in the power station heat cycle. This water is known as condensate
5.4.2.3 Deaeration of make-up water:
Due to leakage and necessary blowing down of boilers some of the
water used in the power station heat cycle is lost and must be replaced. This water, which is
known as make-up water, is generally supplied from reserve feed water tanks and, being in
contact with the air, contains dissolved oxygen. If this oxygen were not removed it would cause
corrosion in boilers and pipe work. The best way of releasing this oxygen is to bring the water to

boiling point and for this purpose the condenser can be employed. The make-up water is
introduced into the condenser where it is brought to boiling point and the dissolved oxygen
released ready for removal together with any air and other gases which may be in the condenser.
5.5 Types of condensers:
Steam can be condensate by using either the jet or the surface type of condenser.
1. Jet condenser
2. Surface condenser
5.5.1 Jet condenser:
The simplest method is to mix the
steam with a spray of water in a closed vessel. The water
will remove the heat from the steam by direct contact and
the steam will condense. This method is used in the jet
condenser which is illustrated in figure.
In a power station the condensate is
returned to the boiler and must be absolute pure. If a jet
condenser were used the cooling water, which is mixed
with the condensate would have to be equally pure.
Because very large quantities of cooling water required,
this type of Condenser is not a practical proposition for
power plant. It was, however, the first type of condenser
ever to be fitted to a steam turbine. A new development for
jet type condenser is in conjunction with the dry cooling Fig:5.5.1 Jet condenser
tower installation at rudely power station, where the
cooling tower becomes a tube heat exchanger instead
of the condenser.
5.5.2 Surface condenser:
Where water is available in
large quantities it is usually very impure, for example,
sea water and river water, but such impurities have
little effect upon its cooling properties.

This suggests a condenser with two entirely separate water system, steam
being condensed on the outside of surface which is kept cool by an abundant supply of water
flowing on the inside. Such an arrangement is known as a surface condenser and the cooling
surface consist of small diameter tubes as shown in figure. In this case the purity of the cooling
water does not matter because apart from any leakages which may occur it is never in contact
with the condensate.
5.6 COOLING TOWER
5.6.1 Cooling water:
When power station are built beside river which cannot supply
sufficient water to condense the turbine exhaust steam by using a once through system, cooling
tower are used in conjunction with a closed circuit system to cool the circulating water.
5.6.2 Principles of operation:
Cooling water is pumped from
the turbine condenser by the tower pump to the
cooling tower. Inside the tower the water passes
through sprinklers, and sprays out in fine drops. The
water than fall as droplets, passing over pickings
where it is made to present a greater surface area to the
cooling air. The water then falls into the cooling tower
pond. Air is drawn in near the bottom of the tower,
either by natural draught or by a fan. The air passes up
the tower and cools the water as it does so. Any water
droplets which have been carried up by the air are Fig: 5.6.2 Cooling water operation
removed by the water droplet eliminator screen.
5.6.3 The theory of cooling:
As a water droplet fall through the tower, air flows past it and cooling
takes place in three ways:
 A small proportion of heat is lost from the droplet by radiation of heat from its
surface.

 Approximately a quarter to one third of the heat transferred is by conduction and
convection between the water and the air; the amount of heat transferred depends
on the temperature of water and air.
 The remainder of the great transfer is by evaporation. As the air evaporates some
of the water into vapor, the remaining water therefore has a lower heat content
than it had originally, and is also at a lower temperature.
The amount of evaporation which takes place depends on a number of
factors; these include the total surface area the water present to the air, and the amount of air
flowing. The greater the air flow, the greater the cooling achieved.
5.7 Types of cooling towers:
There are several types of cooling tower based on two air and water
system. They can be natural or forced draught cooled, and can be wet towers or dry tower. Figure
illustrates two of these types.
5.7.1 Natural drought cooling tower
The modern natural draught tower is
usually of the concrete hyperbolic pattern. The term
hyperbolic refers to the fact that the side of the tower has
the form of a hyperbola. In this type of tower, air moves
upwards, because of the chimney effect created by the
difference in density between the warm moist air inside
the tower and the colder, denser sir outside. Hyperbolic
towers are best suited to regions with high Fig: 5.7.1 Natural drought cooling tower
humidity, populated areas, and where land prices are high.
The height of the exhaust from these tower supports to
prevent the formation of fog along the ground.

5.7.2 Induced drought cooling tower
Induced draught towers, using fans either to force or to induce the
movement of air, first came into use in the 1930s. In a forced
draught tower, the fan is at the bottom and pushes the air up through
the tower. In an induced draught tower the fan is at top and pulls the
air up. One of the main problems with forced draught towers is
recirculation; vapor leaving the tower at low velocity tends to re
enter the tower, with the result that the wet bulb temperature of
entering air is increased and performance of the tower is impaired.
A combination of natural and mechanical Draught cooling can be
seen in the assisted draught tower. The fans, in this case, support to
increase the air flow. With this arrangement it is estimated that a Fig: 5.7.2Induced drought
single tower will provide the cooling for at least 660MW of plant cooling tower
and, although its base diameter will be about 140 m, its appearance from a distance will be little
different from a single natural draught tower with a capacity of 250MW. Compare this with a
500MW unit which requires two natural draught tower 115 m high by 90 m diameter.
5.7.3Dry cooling tower system
Dry cooling tower first made their
appearance in hungry during the 1950s, but it was not
until 1962that the CEGB brought one of these towers
into operation, on a 120MW unit. Figure shows a
schematic layout of a dry cooling tower system. In
principle, it is simply a water to air surface heat
exchanger, like a motor car radiator, the air being
induced to flow through the radiator by the tower
chimney effect. Fig:5.7.3Dry cooling tower system
In the closed circuit, cooled water after passing through the water
turbine from the heat exchanger in the cooling tower is sprayed through nozzle into the direct
contact condenser, where exhaust steam from the turbine is condensed by direct contact. The
cooling water and condensate mixture passes to the CW pump, which delivers most of it through
the discharge culvert to the heat exchangers. The remainder is taken by the extraction pumps and

delivered through the feed heating system to the boiler. As you will appreciate, all the water used
is of condensate quality.
5.8 Condensate Extraction Pump
The condensate water is drawn from the condenser by the extraction pump
and sent to the low pressure feed heaters. This is how we begin to get the water back to the boiler
so that the whole process can start again. The pump which removes the water from the hot-well,
called condensate at this point, is the pump you are referring to. It is a high volume, low pressure
pump and it may have one or more stages. It only raises the pressure enough to get the water out
of the condenser and into the system which pipes it to the feed pump.
5.9 Ejectors
Operation of Ejectors is based upon Bernoulli’s Principle which states: -
‘When the speed of a fluid increases its pressure decreases and vice versa’. The principle is
demonstrated by air moving over the top of a piece of paper is moving quicker than the air
underneath. Thus, the local pressure on the top surface of the paper is less than on the underside.
The resulting pressure imbalance causes the paper to rise. An ejector or steam ejector, is a type
of pump that uses the Venturi effect of a converging-diverging nozzle to convert the pressure
energy of a motive fluid to velocity energy which creates a low pressure zone that draws in and
entrains a suction fluid. After passing through the throat of the injector, the mixed fluid expands
and the velocity is reduced which results in recompressing the mixed fluids by converting
velocity energy back into pressure energy. The motive fluid may be a liquid, steam or any other
gas. The entrained suction fluid may be a gas, a liquid, slurry, or a dust-laden gas stream. The
adjacent diagram depicts a typical modern ejector. It consists of a motive fluid inlet nozzle and a
converging-diverging outlet nozzle. Water, air, steam, or any other fluid at high pressure
provides the motive force at the inlet.
The Venturi effect, a particular case of Bernoulli's principle, applies to the
operation of this device. Fluid under high pressure is converted into a high-velocity jet at the
throat of the convergent-divergent nozzle which creates a low pressure at that point. The low
pressure draws the suction fluid into the convergent-divergent nozzle where it mixes with the
motive fluid.
The seals around the rotating shaft on steam turbines are many in several
ways but all leak a small amount of steam to the atmosphere. To capture this steam, many of the

Inlet Pressure 18.63bar Temperature 320K
Outlet Pressure 17.65 bar Temperature
325K
seals have small condensers to capture this steam. mall
heat exchanger used to condense the steam that leaks past
the first section of seals on
the shaft of a steam turbine. Specifically, if the turbine
exhausts into a vacuum system, it is necessary to inject
sealing steam into the seals in order to keep the low
pressure end of the turbine from drawing in atmospheric
air. Fig: 5.9(a)EjectorLine diagram
This sealing steam
from the low pressure end and the normal leakage
from the high pressure end would tend to leak out and
blow toward the bearing housing. In order to reduce
the chance of this leakage causing an accumulation of
water in the lube oil system, we use a gland steam
condenser to draw a very slight vacuum (typically 2 or
3 in-Hg) at the outer section of the shaft seals. The
gland condenser uses cooling water to condense this Fig: 5.9(b) Ejectors
steam to water which is usually lost to sewer.
5.10 Feed water heater
Feed water heaters are used within a power plants thermal cycle to
improve overall efficiency. The number and placement of feed water heaters are determined
during the original plant design and are highly integrated with the overall performance of the
steam turbine. Feed water heaters preheat the boiler feed water prior to it entering the boiler for
steam generation. The heat used to increase the feed water temperature comes directly from the
thermal cycle, as steam extracted from various turbine sections. The feed water heaters in a
power plant are either LP or HP shell and tube heat exchangers. From an efficiency standpoint,
the primary means of improving the operation of such heat exchangers is to maintain their
operational effectiveness. Feed water heating surface could be added to improve efficiency.
However, the costs associated with either increasing the heat transfer surfaces of existing heaters,

or adding additional heaters for efficiency purposes only, is prohibitive due to the small
incremental reductions in heat rate that would be obtained.
5.10.1 Low Pressure Feed Heaters
Feed-water from the condensate extraction pumps passes through five
low pressure feed heaters. Steam is used to heat the feed-water. After the fifth feed-heater, the
feed-water is at around 160°C. A feed-water heater is a power plant component used to pre-heat
water delivered to a steam generating boiler In a steam power plant, feed-water heaters allow
the feed-water to be brought up to the saturation temperature very gradually.
These feed heaters are increasing the water temperature before this
water returns to the boiler. Low Pressure Heater: A heater located between the condensate pump
and either the boiler feed pump . It normally extracts steam from the low pressure turbine. High
Pressure Heater: A heater located downstream of the boiler feed pump. Typically, the tube side
design pressure is at least 100 kg/cm2, and the steam source is the high pressure turbine.
The heating process by means of extraction steam is referred to as
being regenerative. The feed- heaters are an integral portion of the
power plant thermodynamic cycle. Normally, there are multiple
stages of feed-water heating. Each stage corresponds to a turbine
extraction point. These extraction points occur at various stages of
the expansion of steam through the turbines. The presence of the
heaters in the cycle enhances the thermal efficiency of the power
plant; the greater the number of extraction stages, the lower the
amount of thermal energy required to generate a given amount of
electrical energy. Fig: 5.10.1 Low Pressure Feed Heaters
5.11 De-aerator
From the low pressure feed heaters the water passes through the de-
aerator before going to the high pressure feed heaters. A de-aerator is a device that is widely used
for the removal of oxygen and other dissolved gases from the feed water to steam-generating
boilers. In particular, dissolved oxygen in boiler feed waters will cause serious corrosion damage
in steam systems by attaching to the walls of metal piping and other metallic equipment and

forming oxides (rust). Dissolved carbon dioxide combines with water to form carbonic acid that
causes further corrosion. Most de-aerators are designed to remove oxygen down to levels of 7
ppb by weight (0.005 cm³/L) or less as well as essentially eliminating carbon. In the de-aerator,
the gases are removed from the water to limit corrosion or rusting of the steel tubing that carries
the water back to the boiler and lines the boiler.
5.12 Boosterpump
A Booster pump is a machine which will increase the pressure of a
gas. It is similar to a gas compressor, but generally a simpler mechanism which often has only a
single stage of compression, and is used to increase pressure of an already pressurized gas.
Booster pumps are designed to smooth out water pressure in areas where the flows are highly
variable. Booster pumps are usually piston or plunger type compressors. A single-acting, single-
stage booster is the simplest configuration, and comprises a cylinder, designed to withstand the
operating pressures, with a piston which is driven back and forth inside the cylinder. The
cylinder head is fitted with supply and is charge ports, to which the supply and discharge hoses
or pipes are connected, with a non-return valve on each, constraining flow in one direction from
supply to discharge. When the booster is inactive, and the piston is stationary, gas will flow from
the inlet hose, through the inlet valve into the space between the cylinder head and the piston. If
the pressure in the outlet hose is lower, it will then flow out and to whatever the outlet hose is
connected to. This flow will stop when the pressure is equalized, taking valve opening pressures
into account.
5.13 Boiler Feed Pump
A boiler feed-water pump is a specific
type of pump used to pump feed water into a steam boiler. The
water may be freshly supplied or returning condensate produced
as a result of the condensation of the steam produced by the
boiler. These pumps are normally high pressure units that take
suction from a condensate return system and can be of the Fig: 5.13(a) Boiler Feed Pump
centrifugal pump type or positive displacement type.

The boiler feed pump pumps water into the boiler, overcoming the boiler
pressure of 160 bar to achieve it. The pump is driven by a steam turbine and runs at 7,500
revolutions per minute. The boiler feed pumps consume a
large fraction of the auxiliary power used internally within a
power plant. Boiler feed pumps pressurize and force feed
water through the HP feed water heaters and boiler. Boiler
feed pumps can require power in excess of 10 Mon a 500-
MW power plant, therefore the maintenance on these pumps Fig: 5.13(b) Boiler Feed Pump
should be rigorous to ensure both reliability and high-efficiency operation.
Boiler feed pumps wear over time and subsequently operate below the original design
efficiency. The most pragmatic remedy is to rebuild a boiler feed pump in an overhaul or
upgrade. The overhaul of the pumps is justifiable in the industry and can yield heat rate
reductions estimated to be in the of range 25-50 Btu/kWh.
5.14 Economizer
Fig: 5.14(a) Economizer line diagram Fig: 5.14(b) Economizer
Flue gases leaving the super-heater and re-heater still contain useful
energy. Water from the high pressure feed heaters is heated in the economizer from 252°C to
292°C before it continues to the steam drum. Having given up its last heat in the boiler, the flue
gases move on to the air heater. The economizer makes use of the heat energy that is still in the
flue gas to increase the temperature of the feed water further before it goes to the steam drum. In
boilers, economizers are heat exchange devices that heat fluids, usually water, up to but not
normally beyond the boiling point of that fluid. Economizers are so named because they make
use of the enthalpy in fluid streams that are hot, but not hot enough to be used in a boiler, thereby

recovering more useful enthalpy and improving the boiler's efficiency. They are a device fitted to
a boiler which saves energy by using the exhaust gases from the boiler to preheat the cold water
used to fill it.
An economizer is employed to utilize the waste heat generated from the
combustion process to improve overall efficiency in the boiler. Flue gas exiting the combustion
chamber is still very hot and can be used as a pre- heater for the feed water. The economizer used
for these boilers is a horizontal counter current shell and tube heat exchanger. Feed water enters
finned tubes while hot flue gases pass over the outside. This allows for the recovery of energy
which would otherwise be wasted.
5.15 ELECTROSTATIC PRECIPITATORS
5.15.1 Introduction to ESP
A device which separates particles from a gas stream by passing the carrier
gas between pairs of electrodes across which a unidirectional, high-voltage potential is placed.
The particles are charged before passing through the field and migrate to an oppositely charged
electrode. These devices are very efficient collectors of small particles, and their use in removing
particles from power plant plumes and in other industrial applications are widespread. An
electrostatic precipitator (ESP) is a particle control device that uses electrical forces to move the
particles out of the flowing gas stream and onto collector plates. The particles are given an
electrical charge by forcing them to pass through a corona, a region in which gaseous ions flow.
The electrical field that forces the charged particles to the walls comes from
electrodes maintained at high voltage in the center of the flow lane. Once the particles are
collected on the plates, they must be removed from the plates without re entraining them into the
gas stream. This is usually accomplished by knocking them loose from the plates, allowing the
collected layer of particles to slide down into a hopper from which they are evacuated. Some
precipitators remove the particles by intermittent or continuous washing with water.

5.16 Boiler Re-heater
Power plant furnaces may have a re-
heater section containing tubes heated by hot flue gases
outside the tubes. Exhaust steam from the high pressure
turbine is passed through these heated tubes to collect
more energy before driving the intermediate and then low
pressure turbines. After expanding through the high
pressure turbine the exhaust steam is returned to the boiler
at 360°C and 42 bar pressure for reheating before being
used in the intermediate pressure turbine. The re-heater
reheats the steam from a temperature of 360°C back to 568°C. Fig: 5.16 Boiler Re-heater
5.17 STEAM TURBINES
5.17.1 INTRODUCTION
Steam turbine is a rotating machine which converts heat energy of steam to mechanical
energy. In India, steam turbines of different capacities varying from 15MW to 500MW are
employed in the field of thermal power generation. The design, material, auxiliary systems etc
vary widely from each other depending on the capacity of the sets
.
5.17.2 Development of steam turbines
Historically, first steam turbine was produced by Hero, a Greek philosopher, in 120 B.C.
In 1629, an Italian named Bean actually anticipated the boiler-steam turbine combination that is
a major source of power today. Charles Parsons introduced first practical steam turbine in 1884,
which was also of the reaction type. Just after the five years, in 1889, Gustav de Laval produced
the first practical impulse turbine.
5.17.3 Working principle of steam turbine
When the steam is allowed to expand through a narrow orifice, it assumes kinetic energy
at the expense of enthalpy (heat energy). This kinetic energy of steam is charged to mechanical
(rotational) energy through the impact (impulse) a reaction of steam against the blades. It should
be realized that the blade of the turbine obtains no moving force from the static pressure of the

steam or from any impact of the steam jet. The blades are designed in such a way, that the steam
will guide on and off the blade without any tendency to strike it.
As the steam moves over the blade, its direction is continuously changing and centrifugal
pressure exerted as the result is normal to the blade surface at all points. The total motive force
acting on the blades is thus the resultant of all the centrifugal forces plus change of momentum.
This causes the rotational motion of blades.

2007 PROJECT DOCUMENT ON EXERGY

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