ACKNOWLEDGEMENT
THERMODYNAMIC ANALYSIS OF STEAM CONDENSORWITH ON LINE TUBE
CLEANING SYSTEM
Project report submitted inPartial fulfillment of the
requirements forThe award of the degree of
BACHELOR OF TECHNOLOGY INMECHANICAL ENGINEERING
Submitted by ANAND MOHAN (11231A0346)
AMANULLAH SIDDIQUE (11231A0354) NIKHIL KUMAR (11231A0357)ASHISH
KUMAR GUPTA (11231A0303)
Under the esteemed guidance of
K.DURGA SUSHMITHA, M.TECH ASST.PROF.
DEPARTMENT OF MECHANICAL ENGINEERINGNIMRA COLLEGE OF ENGINEERING
AND TECHNOLOGY(AFFILIATED TO JAWAHARLAL NEHRU TECHNOLOGICAL
UNIVERSITY, KAKINADA)(APPROVED BY AICTE, NEW DELHI PERMITTED BY
GOVT.OF.AP)NIMRA NAGAR, JUPUDI, VIJAYAWADA, KRISHNA
DIST.-521456APRIL 2015
DECLARATION
We hereby declare that the project work Report entitled
THERMODYNAMICS ANALYSIS OF STEAM CONDENSOR WITH ON LINE TUBE
CLEANING SYSTEM which is being submitted to the Jawaharlal Nehru
Technological University Kakinada (JNTUK), in partial fulfillment
of the requirements for the award of the Degree of Bachelor of
Technology in the department of MECHANICAL ENGINEERING, is a
bonafide report of the work carried out by us. The material
contained in this project work Report has not been submitted to any
University or Institution for the award of any degree.
(Register Number) (Name) (Signature)
1. 11231A0346 ANAND MOHAN2. 11231A0354 AMANULLAH SIDDIQUE3.
11231A0357 NIKHIL KUMAR4. 11231A0303 ASHISH KUMAR GUPTA
Department of MECHANICAL ENIGINEERING.
Place: NCET, VijayawadaDate:
CERTIFICATE
This is to certify that the Project entitled THERMODYNAMICS
ANALYSIS OF STEAM CONDENSOR WITH ON LINE TUBE CLEANING SYSTEM
submitted by ANAND MOHAN (Register number 11231A0346); AMAMNULLAH
SIDDIQUE (Register number 11231A0354); NIKHIL KUMAR(Register number
11231A0357); ASHISH KUMAR GUPTA (Register number 11231A0303) is
accepted as the Project submission in partial fulfillment of the
requirements for the award of degree of BACHELOR OF TECHNOLOGY in
the Department of MECHANICAL ENGINEERING
INTERNAL GUIDE HOD ASST.PROF.K.DURGA SUSHMITHA ASST.PROF.K.DURGA
SUSHMITHA
PRINCIPAL
EXTERNAL GUIDE DR.Y.SUDHEER BABU
ACKNOWLEDGEMENT Behind every achievement there lies an
unfathomable sea of gratitude to those who actuated it, without
whom it could not have seen the light of the day. So we take great
pleasure in expressing our heartfelt acknowledgement to all those
who took part in our achievement. We also thank our beloved Head of
Department Mechanical EngineeringASST. Prof. K.DURGA SUSHMITHA for
his outstanding encouragement contributing to completion of this
project.
We are also thankful to the principal Dr. Y.SUDHEER BABU who has
given an opportunity for doing a study project at Dr. NTTPS.
It would be Endeavour to express our profound gratitude to Sri
G.SRINIVASA RAO ADE Stage-2, Turbine maintenance for their
motivating and exemplifying guidance that really helped in doing
this project.
Lastly we exchange a word of appreciation with each other
associates for stimulating discussions, cooperation in their
strenuous work to present this report.
Project Associates ANAND MOHAN (11231A0346)
AMANULLAH SIDDIQUE (11231A0354) NIKHIL KUMAR (11231A0357) ASHISH
KUMAR GUPTA (11231A0303)
ABSTRACTIn the operation and maintenance of a power plant, the
main steam surface condenser is virtually neglected compared with
other components. Efficient and reliable service from condensers
requires more care in both operations and maintenance than the care
that is being taken in current practice.
In the present project, those parameters, which directly or
indirectly influence the performance of a condenser, have been
studied. The factors include cleanliness factor, backpressure,
inlet temperature and saturation temperatures, Heat transfer
coefficients, LMTD, steam flow and seasonal variations. The
procedure for performance test and the subsequent calculations has
been studied in this book from the data collected from condenser of
stage2, Dr. NTTPS.
Performance optimization of steam surface condenser is directly
related to the problems that arise inevitably in any condenser like
fouling, tube leakage and air leakage. These problems along with
the remedial measures have been dealt with the processes of exact
identification and proper monitoring in online tube cleaning
system. Finally it is concluded with the optimum conditions of
inlet temperature and saturation temperature, Heat transfer
coefficients and LMTD for efficient condenser operation.
Dr. Narla Tatarao Thermal Power Station (Dr. NTTPS)
Dr. Narla Tatarao Thermal Power Station is one of the
prestigious power plants in India, which is located on the North
bank of river KRISHNA within a distance of 2KM from the river. The
Plant is located in between Ibrahimpatnam and Kondapalli villages
and 16KM of the north side of Vijayawada. The site lies at an
elevation of about 26.5mtrs above the mean sea level. Dr. Narla
Tatarao Thermal Power Station complex consists of four stages. Each
stage consists of two units, which are about 210MW capacity each.
The total capacity of the station is 1760MW. The first two (as
stage 1) being of Russian design and manually controlled. The next
four (as stage 2 & 3) are fully automated, with the boiler by
Suluzer, France and Turbo-generator set by KMU, Germany. The
boilers are of single pass tower type against the conventional two
pass type. The turbine is of thin wall section and blades. This
type of designing helped in the reduction of many subsystems used
in the first stage.
FIG: POWER PLANTBall mills were used in stage 2 & 3. This
facilitated the incorporation of finer fuel (coal) and input
controls.Stage , II, III units are commissioned as given below:
Stage Unit NoCapacity Date commissioning
1 210MW01/11/1979
2 210MW10/10/1980
3 210MW05/10/1989
4 210MW23/08/1990
5 210MW31/03/1994
6 210MW24/02/1995
IV7500 MW06/04/2009
At Dr. NTTPS we observe the absence of cooling towers as the
required water is drawn from Krishna River. The large reservoir
created by Prakasam barrage on Krishna River that is maintained at
minimum water level throughout the year provides an efficient
direct circulation of cooling water system and meets other water
requirements of the plant.
The stage1 of Dr. Narla Tatarao Thermal Power Station is linked
to Singareni Collieries Company Limited (S.C.C.L) for supply of
coal. Stages 2 &3 are linked to Talcher coalfields in Orissa to
meet the increased demand of fuel.
The complete line diagram of steam power plant is depicted in
the following figure
CONTENTSS.NO PAGE NOCHAPTER 1 INTRODUCTION 1-5 1.1 Working of
Basic steam power plant11.2 Need of a condenser 21.3 Classification
of steam condensers 3
CHAPTER 2 TROUBLE SHOOTING IN THE CONDENSER 6-14 2.1 Fouling in
condenser 62.2 Leaky tubes 112.3 Air leakage 12
CHAPTER 3 CONDENSER ONLINE TUBE CLEANING SYSTEM 15-20 3.1Brush
type cleaning system 153.2 Ball type cleaning system 16 CHAPTER 4
CONDENSER PERFORMANCE ANALYSIS 21-30 4.1Introduction to performance
analysis 214.2 Input data sheet for condenser 224.3 Formulae for
the performance analysis and sample calculations 24 CHAPTER 5
RESULTS AND DISCUSSIONS 31-395.1 The effects of condenser water
inlet temperature 315.2 The effects of steam saturation temperature
335.3 The effects of steam flow 36
CONCLUSION 40REFERENCES 41
LIST OF FIGURESS.NO PAGE NOFIG 1.1 RANKINE CYCLE 6FIG 3.1
CONDENSER VIEW 18FIG 5.1 EFFECT OF CONDENSER INLET TEMPERATURE 31
ON HEAT TRANSFER COEFFICIENTFIG 5.2 EFFECT OF CONDENSER INLET
TEMPERATURE 32 ON DEADLINE FACTORFIG 5.3 EFFECT OF CONDENSER INLET
TEMPERATURE 32 ON EFFECTIVENESS FIG 5.4 EFFECT OF SATURATION
TEMPERATURE 33 ON LMTD FIG 5.5 EFFECT OF SATURATION TEMPERATURE 34
ON HEAT TRANSFER COEFFICIENT FIG 5.6 EFFECT OF SATURATION
TEMPERATURE 34 ON DEADLINES FACTOR FIG 5.7 EFFECT OF SATURATION
TEMPERATURE 35 ON EFFECTIVENESS FIG 5.8 EFFECT OF REHEAT SPRAY 36
ON HEAT TRANSFER COEFFICIENT FIG 5.9 EFFECT OF REHEAT SPRAY 36 ON
CONDENSER DULGFIG 5.10 EFFECT OF REHEAT SPRAY 37 ON CW FLOW FIG
5.11 EFFECT OF REHEAT SPRAY ON VELOCITY 38 OF WATER IN THE
CONDENSER TUBES
NOMENCLATUREA condensing = Condensing surface areaBWG = British
wit worth gauge c d = Condenser dutyCf = Cleanliness factorCp =
specific heat of waterCW = condenser waterD = Density of waterFq =
Correction for condenser heat loadFt = Correction for c.w inlet
tempFw = Correction for c.w flowHcrh = Enthalpy of cold reheatHFW =
Enthalpy 0f feed waterHHRH = Enthalpy of hot reheatHMS = Enthalpy
of main steamHRH = Hot reheatLMTD = Log mean temp differenceMs =
Main steamM.W = Meter water column NT = Number of tubesPgen =
LoadR.H = Reheat sprayTout = Average c.w outlet temp Tin = Average
c.w inlet tempTsat = Saturation temp corresponding to backpressureU
= Uncorrected heat transfer coefficientU actual = Actual heat
transfer coefficient theoretical = Theoretical heat transfer
coefficientZ = constant
CHAPTER 1INTRODUCTION
1.1WORKING OF BASIC STEAM POWER PLANT
FIG 1.1 Rankine CycleSteam power plant operates on Rankine
cycle. It mainly consists of boiler, turbine, condenser and
pump.High pressure superheated steam leaves the boiler and enters
the turbine. The steam expands in the turbine. During this process
the steam does work, and this enables the turbine to drive the
electric generator. The low-pressure steam leaves the turbine and
enters the condenser. Heat is transferred from the steam to cooling
water passing through the condenser tubes, causing the steam to
condense.Since a large quantity of water is required, Power plants
are generally located near rivers or lakes. When the supply of
cooling water is limited, a cooling tower may be used. A pump
enables condensate to flow into the boiler and increases the
pressure of condensate leaving the condenser. In the boiler, the
heat energy of combustion gases is used for converting water to
vapour. In most of the boilers the steam is superheated and thus
high pressure, high temperature steam is supplied to the
turbine.1.2 THE NEED OF A CONDENSER
The maximum possible thermal efficiency of a heat engine is
given by (1) T1 T2 T1
Where T1 and T2 are the supply and exhaust temperatures.
This expression of efficiency show that the efficiency increases
with an increase in temperature T1 and with decrease in temperature
T2. The maximum value of temperature T1 of steam supplied to steam
prime mover is limited by the material consideration. The
temperature T2 at which heat is rejected can be reduced if the
exhaust of steam prime mover takes place below the atmospheric
pressure. Low exhaust pressure means low exhaust temperature.But
the steam cannot be released into the atmosphere if it is expanded
in the engine or turbine below atmospheric pressure. However this
can be made possible, if the steam is made to enter a vessel known
as condenser, where the pressure inside is maintained below the
atmospheric pressure by condensing the steam with the circulation
of cold water.Thus condenser improves the efficiency of the power
plant by decreasing the exhaust pressure of the steam below
atmospheric pressure, as it lowers the exhaust temperature T2.
Condenser provides a source of pure feed water to the boiler and
thus helps in reducing the burden on the water softening plant to a
great extent. So steam condenser is one of the most essential
components of a thermal power plant.
CONDENSERA condenser is defined as a closed vessel in which
exhaust steam from Steam turbine is condensed by cooling water, and
vacuum is maintained. This results in an increase in work done and
efficiency of the steam power plant and use of condensate as feed
water to the boiler.The elements of a water-cooled condensing unit
are:1. Closed vessel in which steam condenses.2. A dry air pump,
which removes air and other non-condensable materials.3. A
condensate extraction pump that extracts the condensed steam
collected in the hot well of the condenser and pumps it to the feed
pipe line.4. A cooling water pump to circulate the cooling water in
condenser.5. A feed water pump to condensate from hot well to the
boiler.
1.3 CLASSIFICATION OF STEAM CONDENSERS
The condensers are mainly classified into four types A. Mixing
or jet type condenserB. Non mixing type or surface condenserC. Non
conventional direct contact condenserD. Evaporative condenser
A. Mixing or jet type condenser
In mixing type condensers the exhaust steam from prime mover and
cooling water come in to direct contact with each other. The
condensate coming out of the mixing type condenser cannot be used
as boiler feed water because it is not free from salts and
pollutants. These types of condensers are generally preferred where
the good quality water is easily available in ample quantity.
Mixing condensers are seldom used in modern power plants. Instead
parallel flow and counter flow jet condensers are used. In a
parallel flow condenser, the steam and cooling water flow in the
same direction. They flow in opposite directions in counter flow
condenser.Mixing type condensers are mainly classified into three
categories depending upon the arrangement used for the removal of
condensate as low level, high level and ejector condensers. These
are rarely used in modern high capacity power plants.B. Non Mixing
type or surface condenserIn non-mixing type of condensers, steam
and cooling water do not come in direct contact with each other.
The cooling water passes through the number of tubes attached to
condenser shell and steam surrounds the tubes. These types of
condensers are universally used in all high capacity modern steam
power plants, as the condensate coming out from the condenser used
as feed for the boiler.These types of condensers are generally used
where large quantity of inferior water is available and better
quality of feed water to the boiler must be used most
economically.The condenser that we have selected for the present
study is a shell and tube type surface condenser. This condenses
the exhaust steam from low pressure turbine and maintains the
possible vacuum in order to increase the heat drop and the turbine
output, besides making it possible to reuse the condensate thus
obtained.
C. Non - Conventional direct contact condenserThis is a new
concept in power industry where condensate is used to condense the
exhaust steam in the condenser. In this arrangement external
condensate cooler cools part of the condensate coming out of
condenser and the same is used again in the condenser in the form
of spray and the condenser is of mixing type.
D. Evaporative condenserThe evaporative condensers are preferred
where acute shortage of cooling waterexists. In this type of
condensers water is sprayed through the nozzles over pipeCarrying
exhaust steam and forms a thin film over it. The air is drawn over
the surfaceof the coil with the help of induced fans.The
arrangement of this type of condenser is simple and cheap. It does
not require large quantity of water therefore needs a small
capacity cooling water pump. The vacuum maintained in this
condenser is not as high as in surface condenser. Therefore the
work done per kg of steam is less when compared to surface
condensers.The evaporative condensers are generally preferred for
small power plants and where there is acute shortage of cooling
water.
Constructional features of Surface condenser
A condenser is a rectangular vessel having suitably stiffened
dome, consisting of stiffening rods, welded on either side walls
and of the dome shell except tubes. The remaining construction is a
fabricated one. The tubes have been expanded into main tube plates
and are supported by the support plates at intermittent points to
prevent their sagging and to curb the flow induced vibrations.
Non-condensable gases are continuously extracted in order to
maintain vacuum in the condenser.Optimum utilization of steam space
by providing rectangular cross-section of tube nest is an added
feature of this condenser. For ensuring equitable loading of
condenser tubes in the bottom rows incurring appreciable steam side
pressure drop - tubes have been segregated in small bunches leaving
wide lanes between them. Tube bundles have been half degree
inclined towards front water box side for its self draining during
cooling water pump tripping. The condenser front water chamber has
provision for the isolation of half of the condenser for on load
leak detection. Water boxes incorporate hinge arrangement to
facilitate the removal of covers for enabling rubbing and cleaning
of tubes. Water boxes and circulating water side of steel main tube
plates have been protected against corrosion by the application of
protective coating over the surface in contact with cooling water.
Provision for sacrificial anodes has also been made for additional
protection against corrosion.
InstallationCondenser has been floated over the springs, which
take empty weight of condenser along with the partial operating
weight while remaining operating weight is taken by the turbine
foundation. Tube installation is tested by filling water into steam
space up to one meter above the top tube row. Prior to filling
water into condenser steam space for above testing screws provided
with spring support should be used for ensuring water weight being
passed on to them, to avoid over stressing of turbine
foundation.
CHAPTER 2TROUBLE SHOOTINGS IN THE CONDENSER
Generally the following problems are faced in the operation of
condensers in Steam power plants.
1. Fouling2. Leaky tubes3. Air leakage
2.1 FOULING IN CONDENSER
When the heat transfer apparatus has been in service for some
time, dirt and scale deposits on inside and outside of the pipe. As
a result the thermal resistance in the path of the heat flow
increases, which reduces heat transfer rate. Thus during operation
condenser tubes become fouled with an accumulation of deposits of
one kind or another on heat transfer surface.
The dirt or scale formation is termed as fouling. This results
in increased resistance to heat transfer is called fouling factor.
This should be considered in calculating the overall heat transfer
coefficient. This additional resistance reduces the original value
of overall heat transfer coefficient.The economic penalty for
fouling can be attributed to,1. Higher capital expenditure through
over sized units.2. Energy losses due to thermal inefficiencies.3.
Costs associated with periodic cleaning of heat exchanges.4. Loss
of production during shut down for cleaning.
The magnitude of the fouling factor depends on nature of the
scale. Th scale is uniform in composition and structure, the
resistance is calculated by dividing the scale thickness by the
thermal conductivity of the scale material. Usually the scale is of
an unknown or complicated composition and structure and the fouling
factor must be known for analyzing the performance of condenser.
The fouling process is obviously a time function starting with zero
and proceeding along some pseudo asymptotic or linear relationship
but a constant value is generally used in design. This is then
interpreted as a value to be reached in some reasonable time
interval at which time the user of the equipment is willing to
clean it. Allocation of exaggerated large fouling resistance also
does not guarantee longer operating time. On the contrary in many
cases it can contributes to more rapid deterioration.
TYPES OF FOULING PROCESSScaling or precipitation foulingOne of
the common causes of fouling is due to crystallization of salts
having inverse solubility character than normal solubility.Unlike
normal salts certain salts exhibit decreasing solubility beyond a
certain temperature. Thus when they come in contact with the heated
surface crystalline deposits are formed. In water scaling, examples
for such salts are CaCO3 and CaSO4.
Sedimentation or particulate foulingThe accumulation of finely
divided solids like rust, dusts, clay, sand etc. on the heat
transfer surface is also known as fouling. When the settling of
particles due to gravity, the process of fouling is known as
sedimentation. Rust and dust are Generally caused by air, where as
sand and mud are carried by river water. The effects of these are
partly reduced by filtering methods before the use of water for
cooling.
Chemical reaction fouling or polymerizationDeposits formed at
the heat transfer surface by chemical reaction in the fluid itself
(in which the surface material is not a reactant) are referred to
as chemical reaction fouling. This type of fouling occurs in many
times in petroleum and chemical streams. Surface temperature is a
critical variable, since it determines the reaction rate. A special
type of chemical reaction fouling occurs in organic fluid moderated
nuclear reactors.
Corrosion foulingCorrosion products of the heat transfer surface
produced an additional thermal resistance. Corrosion creates
roughness, which will produce nucleation sites for crystallization
and particle sedimentation.
Biological foulingThe attachment of macro (clams, barnacles,
mussels) and micro (algae, fungi, bacteria) organisms to heat
transfer surface is known as biological fouling. This develops on
heat transfer surface in contact with untreated water such as sea,
river or lake water. Macro organisms pass through the intake of
condenser plant and settle on the hot heat transfer surface thus
impairing heat transfer.Sometimes the extent of bio fouling may be
so much leading to shutdown of power station due to cooling system
blockage. Cost of cleaning and lost output is extremely high. The
growing interest in controlling bio fouling is due to wide use of
seawater as cooling medium in power stations and OTEC plants.
Bacteria are very sensitive to temperatures below 0 to 20 and above
40 to 70 degrees Celsius will kill most of the marine bacteria.
Freeze fouling or solidification foulingThe crystallization of
pure liquid or one component from the liquid phase on a sub cooled
heat transfer surface falls under this category.
PARAMETERS AFFECTING FOULING
Velocity
Velocity affects the fouling process with respect to both
deposition and removal. The effect of velocity on removal is
characterized by the strength of the deposit. For inorganic type of
fouling, as the deposition rate is a controlling process the
fouling rate increases with velocity .For organic type of fouling
the residence time of particulates in the boundary layers decreases
with increased velocity and reduces the fouling rate.The allowable
velocity range is 1 to 3 m/s.
Temperature
The liquid bulk temperature, wall temperature and scale fluid
interface temperature are important in the fouling process.Under
constant heat flux conditions, there will be effect of temperature
on deposition rate. A portion of deposit will undergo additional
crystallization process as the temperature with in deposit
increases.For a fluid containing inverse solubility of salts the
deposition rate increases with increasing interface temperature.
The fouling resistance increases asymptotically with increase in
bulk temperature to a maximum, and then decreases. The decrease is
due to smaller temperature gradient and therefore less mass
transfer to the crystallizing surface if outlet water temperature
is greater than 50 deg c corrosion problems arises.
Water chemistry
Generally PH compositions of different salt components are used
to characterize the water chemistry the biological fouling mostly
depends on the PH value of water used in condenser.
Tube materialsThe effect of tube material is to add corrosion
products to the deposit on surface. The characteristics of tube
materials also have an effect on deposition.
PREVENTION OF FOULING
Fouling can pose serious problems in process plants and some
time lead to unplanned shutdowns and production losses. Fouling
always leads to higher-pressure drops and hence higher operating
costs. Thus fouling is an evil that must always be prevented.
Unfortunately complete prevention is neither possible nor
economically feasible. Therefore steps must be taken to keep
fouling at minimum. This can be done by method listed below.
Proper Design of condenser
The design of a condenser plays very important role in fouling
deposition.A. Velocity should kept sufficiently high (not too high
as it may cause erosion and excess loss) because low velocity would
not exert sufficient shear to remove fouling layer.
B. A wrong selection of material can cause corrosion and
increase the fouling rate. Some experiments tried with the Teflon
tubes to minimize fouling have been quite successful. They have a
lower fouling initiation tendency because of smooth surface.C.
Fluid with high fouling tendency should be preferably placed on
tube side for greater care of cleaning. However if chemical
cleaning is used, there is no preference between the tube or shell
side.D. For mechanical cleaning square pitch is preferred where as
for hydraulic cleaning on the shell side a large tube pitch must be
used.E. As polymerization fouling is particularly sensitive to tube
wall temperatures, concurrent flow is preferred in such cases that
maintain lower and uniform wall temperature.F. Stagnant region in
the shell side should be avoided by well proportioned baffles
spacing, baffles cut and multi-segmental baffles.Treatment of
process system A. Fluid system containing large amount of solid
particles should be filtered before entering the condenser. B.
Additive to suppress fouling or becoming increasingly popular.C.
Polymer formation can be prevented by addition of stabilizers.
Cleaning system
A toproge condenser tube cleaning system uses slightly oversized
abrasive sponge rubber balls, which are re-circulated through the
tubes. These balls remove all fouling and even hard deposits in the
tubes. This method reduces the down time lost which forms the major
part of the loss due to fouling.
Biocides and BiostatsThese are used for controlling the fouling.
Biocides kill the organisms where as Biostats reduce the growth of
organisms. Copper and its alloys have been used as biocides but
their use is too costly for use in sea thermal plant. In OTEC
plants where corrosion of surfaces under the biological growth is a
serious problem. Aluminum or plastic are suggested as the
materials.
Sacrificial anodesUse of sacrificial anodes in the case of cast
iron pipes decreases the corrosion rates and in a way prevents
fouling due to corrosion.2.2 LEAKY TUBESTubes leakage is one of the
major problems in condenser application. Tube may leak,1. At the
tube plate joint due to the improper attachment.2. Within the
length due the pealing of oxide layer.
EFFECTS DUE TO TUBE LEAKAGE 1. Condenser gets contaminated with
cooling water which effects the operation of boiler and turbine. 2.
Vacuum in the condenser decreases intern results in decreasing the
power output. If the leaks in tubes are few in number then they
just block at the both ends without shut downing the condenser. If
there are more in number effect in the operation of condenser then
the unit is to be shut down for replacing the leaky tubes.DETECTION
OF LEAKING TUBESWhen turbine is in operationCondenser has been
provided with the divided water chambers thus making it possible to
locate the leaky tube and plug its ends even when turbine is in
operation For locating the leaky tube concerned portion of water
chamber should be isolated on cooling water side and tube plate
should be dried commencing from top to bottom by the application of
dry air.Tube openings should be covered with a thin polythene sheet
that will get sucked in to failed tube end, alternatively tube ends
should be scanned through with a lighted candle stick/smoke
generator. The flame/smoke will get attracted into the leaky tube
end.Leaky tube can also be detected by the use of U-tube manometer.
Plug one end of tube with soft rubber and connect the other tube
end with U-tube manometer having color water. Color water will get
sucked into the tube in case of leaky tube; otherwise water level
will remain unchanged.
When the machine is under shutdown Drain the water boxes and
fill condenser steam space with water only up to one meter above
top row of tubes. Water comes from the leaky tubes.2.3 AIR
LEAKAGEThe sources of air leakage in the condenser are listed
below,The feed water contains air in dissolved condition. The
dissolved air gets liberated when the steam is formed and it is
carried with the steam into the condenser.Air leaks through the
joints, packing and glands into the condenser, where the pressure
is below the atmospheric pressure.
The effect of air leakage in condenser are listed below,It
increases the pressure in condenser or back pressure of the prime
mover and reduces the work done per kg of steam.The pressure of air
lowers the partial pressure of steam and its corresponding
temperature. The latent heat of steam increases at low pressure
.Therefore more quantity of water is required to condense one kg of
steam as the quantity of latent heat removed is more. These are
greater possibility of under cooling condensate with the reduction
in the partial pressure of steam due to the presence of air. This
phenomenon reduces the overall efficiency of the power producing
plant.The heat transfer rates are greatly reduced due to the
presents of air offers high resistance to heat flow. This further
necessitates the more quantity of cooling water to maintain the
heat transfer rates. Otherwise it reduces the rate of condensation
and further increases the back pressure of the prime
mover.Preventive measures should be taken to remove leaking air
from the condenser to avoid bad effects. The air from the condenser
is removed with the help of air pumps. The primary function of the
air pump is to extract the air from the condenser.
DETERMINATION OF BREAKUP OF CONDENSER BACK PRESSURE
DEVIATION
Corrosion Failures of Heat Exchanger Tubes
Corrosion is the unintended destructive interaction of a
metallic component with its environment leading to its
failure.Types of Corrosion Phenomena on the basis of their physical
manifestation Velocity affected corrosion (erosion corrosion)
Uniform corrosion Pitting corrosion Intergranular corrosion
Concentration cell corrosion Galvanic corrosion Bacterial or
Bio-Fouling corrosion
Factors that determine the type of corrosion process Presence of
crevices in metal parts or assemblies Relative motion between the
metal parts and environment Presence of dissimilar metal parts in
an electrically conducting environment Temperature gradients at
metal environment interface
Metals Research Laboratory (MRL) of BHEL Haridwar, who recently
carried the investigations to determine the cause of these
failures.
There are mainly two types of failure due to corrosion according
to their report1. Dealloying Corrosion Failures2. Velocity Effected
Corrosion (Erosion Corrosion) Failures
To know about these failures they had mainly done three types of
tests as follows Visual Examination for both internal and external
surfaces. Hardness testing. Metallographic examination.On Admiralty
Brass oil cooler tubes of Dr. Narla Tatarao TPS, Srisailam HPS,
Ropar TPS, Nagarjuna HPS and Admiralty Brass condenser of Ukai HPS,
Cupro- Nickel condenser tubes of Kolaghat TPS.
Conclusion given by BHEL Haridwar isFailure of Heat exchanger
tubes is a normal phenomenon and generally occurs either by
selective leaching or velocity-effected corrosion. Preventive
measures include a change in the tube material to more resistant
alloys such as stainless steel or titanium but economics of this
change largely dictates the feasibility of changeover. Other
measures include a strict control of the water composition,
periodic cleaning of the tubes to prevent deposition of muddy
deposits and ensuring proper operational conditions.
However, despite the best operational practices, failures are
not totally avoidable through the occurrences can be significantly
reduced. However, as the above examples show, determination of the
cause of failure does not require sophisticated tools and can
frequently be done at the site itself, thus leading to fast
corrective actions.
CHAPTER 3CONDENSER ONLINE TUBE CLEANING SYSTEM
3.1 BRUSH TYPE CLEANING SYSTEM
The Problem Corrosion and fouling of Condenser & Heat
Exchanger Tubes are major factors affecting the performance of a
plant. The SolutionOn Line Tube Cleaning System facilitates
cleaning of the Condenser Tubes up with the Plant in operation,
continuously every day without effort thus improving efficiency and
wasting no downtime on shutdowns. Your equipment essentially
becomes self-cleaning. The systems automatically maintain a fouling
factor below the manufacturers design specification.The online tube
cleaning system is actually three different variations on a similar
concept, each engineered specifically for a given application. All
systems require no special operator effort and no interruption in
day-to-day equipment performance.
Nylon Brush TypeIn low temperature systems, each tube is fitted
with a specially developed and fabricated nylon brush and special
catch baskets. As the brushes travel back and forth through the
tubing, they scrub the interior walls without interrupting the
systems operation.
Steel Brush TypeHigh temperature process systems use stainless
steel brush and steel baskets for scrubbing tubing walls.
Sponge Ball TypeSome special applications cleaning is
accomplished by injecting slightly oversized sponge rubber balls
which into the supply line, then recirculated in a closed loop
system of their own. These re-circulating balls clean interior
tubing surfaces just as efficiently as the scrubber brushes and,
like the brushes, may be timed through the control panel for
periodic cleaning passes.BRUSH TYPE
Brush type on-line tube cleaning systems consists of catch
basket at either end of each condenser tube. A free floating brush
inserted into each tube; an automatic, programmable control panel;
and a four-way, flow-reversing diverter.
Propelled by liquid flow, the small brushes travel back and
forth periodically through your heat exchanger or condenser tubing,
scrubbing the inner walls and keeping heat flow unrestricted.
The easily installed flow diverters reverse the flow tube-side
water or process fluid automatically at preset intervals. In fact,
by programming the control panel to reverse the tube-side flow
several times a day, the cleaning brushes are shuttled back and
forth automatically and your tubing system is scrubbed to function
near pack efficiency at all times.At the heart of this effortless
maintenance system is the four-way diverter, controlled by a
programmable control panel, which periodically shuttles the
cleaning brushes to and fro within the system at certain
predetermined intervals.This diverter may be timed, through the
control panel, to reverse the flow of fluids at virtually any
interval settings.
3.2 BALL TYPE CLEANING SYSTEM
Elastomeric rubber balls are injected into the supply line and
forced through the condenser/heat exchanger tubes by the cooling
water flow. Proper ball distribution is achieved by special
injection method and the ball type used.Being slightly larger than
the inside diameter of the tubes, balls actually wipe the tubes
clean. The balls are separated from the cooling water by a strainer
section, extracted by a pump, passed through a ball collector, and
recirculated into the cooling water supplying closed
manner.Patented vortex and turbulence promoters are installed at
the strainer outlet point to enhance ball recovery. Provisions are
made to turn the screens to the backwash position to clear
accumulated debris. A differential pressure monitor displays the
pressure drop across the strainer section. Options of continuous,
intermittent, or manual cycles are provided. Optional features are
also available to monitor the number of balls in circulation and
indicate the quality of worn balls
Major Components and Auxiliary Equipment Of sponge ball type on
line tube cleaning system are as shown in the below figure.a.
Universal Debris filterb. Ball Separatorc. Ball Recirculating
Skidd. Measuring and Control Systeme. Ball Monitoring Systemf. Ball
charger and feederg. Ball injection Nozzles
GEA India supplies a wide range of cleaning balls to suit every
application Sponge Rubber - Hardness selected to suit service
conditions. High Temperature Balls - For application up to 1400 C.
Abbrasive Balls - Ring/Fully coated for removal of hard deposits.
Granulate Coated Balls - For use in Titanium tubes. "V"-TYPE DEBRIS
SEPARATOR
The Debris Filter installed in the C.W. Inlet Line is an
important secondary filtering equipment. The design and the
internal construction of the Debris Filter is based on the Water
flow, type, size and quantity of the Debris and the Cooling Water
inlet Pressure. The Debris is collected at the inner surface of the
screen, housed inside the filter. Monitoring the Differential
Pressure across the Screen indicates the level of debris fouling on
the filter screen. When it reaches a preset limit, the control
system initiates the debris removal operation, till the screen is
cleared off the debris. Debris accumulated on the inside surface of
the screen is sucked by the debris extraction assembly which routes
the extracted debris into the Debris Discharge Pipe connected to
the main condenser outlet pipe or drain.An Electric Gear drive
mounted outside the Filter housing facilitates the rotation of the
Flushing Assembly. The cleaning operation ceases once the screen is
clean. The salient feature of the GEA filter is that at no time is
there any significant reduction of water flow during the screen
cleaning operation.Many a times the extraction technique alone is
inadequate to dislodge all the Debris from the screen. To
effectively solve this problem the GEA Filter incorporates a
special patented Rotating High Pressure Water Injecting Arm on the
rear side of the screen. However, it is an optional item.
The basic principle of operations and the construction is
similar to Debris Filter. It is only for our own convenience that
we are calling the debris filter of size DN 200 to DN 900 as Self
Cleaning Strainers. Otherwise even Debris Filters are also Self
Cleaning type filters only.
FIG 3.1 CONDENSER VIEW
Design features --Easy maintainability--Flexible design to
accommodate varied customer requirements.--Design standards to
ASME/DIN/BS/BIS/IIS--Installation can be Horizontal/Vertical
--Filter basket ranging from 900 - 3500 mm--Filter basket
perforations ranging from 1 - 10 mm--Normal flushing cycle of 3
min. and adjustable as per site conditions.--Low backwash flow
shall be as low as 3% of total cooling water as an additional
feature--Construction in Carbon Steel, Carbon Steel Rubber lined
Stainless Steel (SS 316, 316L, 317LN) and Cu Ni, to suit
application.
The savings
- Keep fouling deposits from forming inside tubes.- Increase
heat transfer coefficient.- Maintains constant high heat transfer
rate meet design specifications.- Increases energy efficiency and
heat recovery by as much as 25%.- Increase Production.- System is
automatic, easy to operate and easy to maintain.- Reduces
maintenance and downtime cost for your condenser/chiller or process
exchanger.- Reduces the amount of chemicals needed to treat your
system.- Easily installed in new or existing systems.- System pays
for itself, sometimes in as little as six months
CONDENSER PERFORMANCE TESTING AND MONITORINGEfficient, reliable
service from condenser requires considerably more care in both
operational and maintenance that has been current practice.
Generally acceptance tests and routine operational tests are
conducted to have an idea about the performance of the
condenser.
Condenser performance tests are carried out for two reasons
A. Acceptance tests are conducted to establish whether a
condenser meets its specified performance, and whether it is
capable of producing the desired condenser backpressure when
operating under specified conditions. This test will also form a
benchmark for future comparison.
B. Routine operational tests are conducted to monitor the
condenser performance periodically, and to verify that the
condenser performance is not being adversely affected by
deterioration in the condenser parameters.
In both the acceptance tests and routine tests high standard of
instrumentation is required, particularly in the measurement of the
condenser back pressure and the cooling water temperatures. Routine
tests generally use less instrumentation than acceptance tests.
CHAPTER 4CONDENSER PERFORMANCE ANALYSIS4.1 INTRODUCTIONAfter
steam has surrendered its useful heat to the turbine, it passes
onto the condenser. The work obtained by the turbine from the steam
will increase as the backpressure is reduced, so it is always
desirable to keep the backpressure at minimum achievable level. In
fact, condenser backpressure is the most important operating
parameter of a unit; therefore, the factors, which worsen
backpressure, must be clearly identified so that effective remedial
measures can be taken.There are various controllable parameters to
improve/maintain the condenser performance such as cleanliness
factor, air-ingress, cooling water (CW) flow etc.
In view of this it is recommended to carryout simplified routine
performance test on condenser at certain frequency to identify the
level of deviations and trending of performance. Objective and
ScopeThe scope is limited to condenser. This test procedure shall
determine the condenser performance with regard to one or more
performance indices as follows.Evaluation of testIn this
performance test we have taken readings of load, flow of feed water
and main steam, main steam temperature (temp) and pressure(pr),
Cold Reheat (CRH) steam pressure and temperature at High Pressure
Turbine (HPT) exhaust, Hot Reheat (HRH) steam pressure and
temperature at Intermediate Pressure Turbine (IPT) inlet,
saturation temperature , HPH6 feed water inlet and outlet
temperature and pressure, Economizer and HPH5 inlet feed water
temperature, steam pressure at ejector nozzle, No extraction steam
pressure and temperature , Input casing exhaust steam pressure and
temperature and HPH6 drip temperature are taken for this test. The
Condenser Duty, CW flow, Tube Velocity, LMTD, U-actual,
U-theoretical, Cleanliness Factor, Expected values of LMTD and Tsat
are calculated.
4.2 INPUT DATA SHEET FOR CONDENSER
1. Design cooling water temperature - 36 0c
2. Cooling water temp raise - 8.1 0c
3. Cooling water flow quantity - 30600 m3/hr
4. Condenser backpressure - 89mm of Hg abs
5. Cooling waterside pressure drop - 3.1 Mwc
6. No. of cooling water passes - 1
7. No. of tubes - 23934
8. Tube dimensions Outside diameter - 19 mm Thickness - 1 mm
Ordering length - 9.9 m
9. Tube material - 90/10 copper/nickel
The following table denotes the input parameters required for
the performance analysis of condenser.
LoadMW210.00209.8
Feed water flow hourly averageTPH649.00665.2
R.H. SprayTPH8.0013.5
Main steam flowTPH641.00651.5
M.S.Pressure after strainer (L/R)Kg/Cm2151.00147.5
M.S temp. before E.S V1/E.S V2 Degree. C532.00535.5
H.P.Turbine I-st blading PressureKg/cm2132.8135.00
C.R.H. Steam Pr.at H.P.T. ExhaustKg/cm237.236.75
C.R.H Steam temp.at H.P.T. Exhaust Degree. C352.5354.5
H.R.H Steam Pr.at IPT.I n let.Kg/cm23533.9
H.R.H Steam temp. at IPT.I n let Degree. C537.3538.5
L.P. Turbine Exhaust hood temp (Tsat). Degree. C45.845.7
Number of Ejectors in service Nos.22
H.p.heater 5 in let Feed water temp.Hz.168169.4
H.p.heater 6 O/L Feed water temp. Degree. C246.6257.5
H.p.heater 6 in let Feed water temp. Degree. C201.5202
H.p.heater 6 in let Feed water Pr...Kg/cm2172172
H.p.heater 6 out let Feed water Pr...Kg/cm2171171
Economizer inlet Feed water temp(L/R) Degree. C242.5239
C.W. Temp.at condenser I / L -O/L(L/R) Degree.
C29.9/3932/39.55
Steam pressure at ejector nozzleKg/Cm28.28.3
No.6 Extraction steam Pr...Kg/cm23736.8
No.6 Extraction steam temp Degree. C352.3354.7
IP casing Exhaust steam temp.(L/R) Degree. C337.6337.8
H.P. Heater -6 Drip temp Degree. C228227.5
IP casing Exhaust steam Pr(L/R)Kg/cm277.1
Steam temp. at ejector nozzle Degree. C201203.00
4.3 FORMULAE FOR THE CONDENSER PERFORMANCE ANALYSIS AND SAMPLE
CALCULATION
1. Determination of Condenser DutyThe amount of heat to be
removed by the condenser from the steam in a given time is the
Condenser Duty.
Condenser Duty = {(Heat Added MS + Heat Added HRH + Heat added
spray) 860 (Pgen + Pgen losses + Heat Loss rad)} * (4.18/3600) =
{(356502.103 + 58343.885 + 7797.492) 860 (209.8 + 20.98 +
2.098)}*(4.18/3600) = 258.315 KJ/S Where Condenser Duty = KJ/Sec
Heat Added MS = Flow MS (HMS hFW) = 651.5 (815.164 267.9) =
356502.103 Kcal/Hr Flow MS = 651.5 Kg/Hr HMS = 815.164 Kcal/Kg HFW
= 267.9 Kcal/Kg
Heat Added HRH = Flow HRH (hHRH hcrh) = 565.286 (845.554
742.342) = 58343.885 Kcal/Hr
Flow HRH = 565.286Kg/Hr HHRH = 845.554 Kcal/Kg Hcrh = 742.342
Kcal/Kg
Heat added spray = Rh spray (hHRH hFW) = 13.5 (845.554 267.962)
= 7797.492 Kcal/Hr Pgen = 209.8 KW (Gross Generator Output) Heat
Loss rad = 0.1% of Pgen (Radiation Losses) KW Pgen Losses = (Mech
Losses + Iron Losses Stator Current Losses) Generally Pgen Losses
are taken as 0.01% of Pgen.
2. Determination of Condenser Flow
The volume rate of flow of cooling water required to attain the
condenser duty is given by CW flow.
Condenser DutyCW Flow = --------------------- Cp (Tout Tin) * D=
258.315 * 1000 / (4.18 * (39.55 32) * 1000) = 8.185 m3/Sec
WhereCondenser Duty = 258.315 KJ/hr.Cp = 4.18 KJ/kg deg. CD = 1000
Kg/cubic meterT out = 39.55 deg. C T in = 32 deg. C
3. Water Velocity in Condenser Tube
C.W. Flow rate * 106Tube Velocity =
----------------------------------------------------------------
Tube Area * (Number of Tubes - Number Of Tubes Plugged) = 8.185*
106 / ( ( /4 * 172) * (23934 0 ) = 1.507 m/sec.WhereTube Velocity =
m/secC.W. Flow Rate = m3/SecTube Area = mm2
4. Computation of Log Mean Temperature Difference (LMTD)
(Tout Tin)LMTD = ------------------------ (Tsat Tin) Ln
------------- (Tsat Tout) = (39.55 32) / Ln ((45.7 32) / (45.7
39.55)) = 9.42 deg. C
WhereLMTD = deg. CTsat = 45.7 deg. C (Saturation temperature
corresponding to Back pressure)
5. Determination of Cleanliness Factor
It is the ratio of actual heat transfer coefficient to that of
theoretical heat transfer coefficient, which is commonly used in
diagnostics as an indicator of thermal fouling of the heat
exchanger surface.
U actual (Actual heat transfer coefficient) Cf (cleanliness
factor) = ---------------------------------------------------- U
theoretical (Theoretical heat transfer Coefficient)
= (1685.794 / 2940.440) * 100 = 57.33 %
Condenser Flow * Cp * ( Tout Tin ) * Density of waterU actual =
-----------------------------------------------------------------------A
condensing * LMTD
= (8.185* 4.18 * (39.55 32) * 1000) / (14000 * 9.426 ) = 1.9574
KJ/Sec m2 0C WhereU actual = Kcal/hr m2 0CDensity of water = 1000
Kg/m3 A condensing = m2 (condensing surface area)
U theoretical = U * Tin correction factor * tube correction
factor *4.882428
= (593.5 * 1.0739 * 0.945 * 4.882428) * (4.18/3600) = 3.41
KJ/sec m2 0C
Fw - INLET WATER TEMPERATURE CORRECTION FACTOR
Inlet Water 0FFwInlet Water 0FFwInlet Water
0FFw300.650600.923901.075310.659610.932911.078320.669620.941921.080330.678630.950931.083340.687640.959941.085350.696650.968951.088360.706660.975961.090370.715670.982971.092380.724680.989981.095390.733690.994991.097400.743701.0001001.100410.752711.0051011.103420.761721.0101021.105430.770731.0151031.108440.780741.0201041.110450.789751.0251051.113460.798761.0291061.115480.816781.0371081.119490.825791.0411091.121500.834801.0451101.123510.843811.0481111.125520.852821.0511121.127530.861831.0541131.129540.870841.0571141.131550.879851.0601151.133560.888861.0631161.135570.897871.0661171.137580.905881.0691181.139590.914891.0721191.141
WhereU theoretical = KJ/sec m2 0CU = heat transfer coefficient in
Btu/hrs qft Tin correction factor = Correction factor for actual
C.W. inlet temperature.Tube correction factor = Correction factor
for tube material and Tube wall gauge.
6. Determination of expected LMTD for Deviation from Design
Value
Correction for C.W. Inlet temperature (ft)
| Saturation temp test LMTD test | 1/4ft =
|------------------------------------------------- | | Saturation
temp design LMTD design |
= ((45.7 9.426) / (49.2 8.4)) (1/4) = 0.943. Correction for C.W.
Flow (fw)
| Tube velocity test | 1/2Fw = |-------------------------- | |
Tube velocity design | = (1.507 / 1.565) (1/2) = 0.981.
Correction for condenser heat load (fq):
Condenser duty design Fq =
---------------------------------Condenser duty test
= (280.68 / 258.31) = 1.087 Expected LMTDLMTD expected = LMTD
test * ft * fw * fq = 9.426 * 0.943 * 0.981 * 1.087 = 9.476 deg.
C
7. Determination of Expected Saturation Temperature (Taking into
considerations deviation in opening value from design values)
[ Tin Tout * Expo (z ) ]Sat Temp Expected =
--------------------------------- deg. C [ 1 Expo (z) ]
= (32 ( 39.55 * Expo (0.797))) / (1-Expo (0.797)= 45.74 degree C
WhereTin = C.W. inlet tempTout = C.W. outlet temp
Tout - TinZ = -------------------- = (39.55 32) / 9.426 Expected
LMTD = 0.797.
CHAPTER 5RESULT AND DISCUSSION
5.1 Effects of condenser inlet temperature
FIG 5.1 Effect of condenser inlet temperature on Heat transfer
coefficients
Tin2627282930313233
Uthe2805.292823.422837.892852.422866.862880.892893.572901.77
Uact1234.531338.21461.51611.641798.082037.392358.462819.12
The Theoretical Heat Transfer Coefficients increasing with the
increase in CW inlet temperature as shown. Because heat transfer
coefficient mainly depends on LMTD, as the LMTD decreases the heat
transfer coefficients gradually increases.
FIG 5.2 Effect of condenser inlet temperature on cleanliness
factor
Tin2627282930313233
Cf4447.3951.556.562.770.281.5297.15
The cleanliness factor is increasing with the inlet temperature
increasing, the reason for it is the increasing u-actual
comparatively more than u-theoretical in the formula Cf = U-actual
/ U-theoretical.
FIG 5.3 Effect of condenser inlet temperature on
Effectiveness
Tin2627282930313233
0.4550.4820.5130.5400.5870.6330.68640.75
The temperature difference of water outlet temperature and inlet
temperature are fixed and only the water inlet temperature is
increasing, so the effectiveness is increasing. = (Tout Tin)/ (Tsat
Tin).
5.2 THE EFFECTS OF STEAM SATURATION TEMPERATURE
FIG 5.4 Effect of saturation temperature on LMTD
Tsat4041424344454647
LMTD6.8727.779.05210.11511.16412.20513.23914.264
Both the sides of the condenser the temperature difference is
increasing so the LMTD is increasing.
FIG 5.5 Effect of saturation temperature on Heat transfer
coefficients
Tsat4041424344454647
Uthe2842.132842.132842.132842.132842.132842.132842.13284.13
Uact239620651819.281628.441475.381349.511244.141154.4
With the increasing saturation temperature the actual heat
transfer coefficient decreases as the LMTD is increasing. But the
theoretical heat transfer coefficient remains constant as the tube
velocity is not changing.
FIG 5.6 Effect of saturation temperature on Cleanliness
Factor
Tsat4041424344454647
Cf84.33872.666457.29651.29147.4843.77940.617
Cleanliness factor depend on the heat transfer coefficients.
With the increasing saturation temperature the actual heat transfer
coefficient is decreasing remaining theoretical heat transfer
coefficient constant automatically the cleanliness factor
decreases. This means due the dirty tubes saturation temperature of
condenser water increases.
FIG 5.7 Effect of saturation temperature on Effectiveness
Tsat4041424344454647
0.690.6390.5910.5510.5150.4850.4570.433
The temperature difference between the water inlet and outlet
temperatures is fixed and the saturation temperature is increasing,
so there is gradual decrease in effectiveness.
5.3 EFFECT OF STEAM FLOW
FIG 5.8 Effect of Reheat Spray on Heat transfer coefficients
Rh68101214161820
Uth2818.492825.952833.242840.372847.392854.302861.142867.93
Uac1477.651485.621493.581501.551509.541517.471525.441533.41
Whenever heated spray is increasing heat transfer is also
increasing, so heat transfer coefficients are also increasing.Q =
Ms (L) = Mw * Cw * (Tout Tin).
FIG 5.9 Effect of Reheat spray on Condenser Duty.
Reheat spray681012
Condenser Duty226636.46227858.04229079.62230301.211
14161820
231522.79232744.37233965.95723518.739
With the increase in steam flow the heat gained from the steam
increases resulting in condenser duty increase.
FIG 5.10 Effect of Reheat sprays on CW Flow.
Rh6810121416
Cwf27979.8128130.6228281.4328432.2528583.0628733.87
1820
28884.6829035.41
The steam and water consumption for condenser is directly
proportional to each other, so the water flow increases with the
steam flow.
FIG 5.11 Effect of Reheat spray on the velocity of cooling water
in the condenser t tubes
Rh68101214161820
V1.43061.4381.4461.45381.46151.46951.47691.484
The tube velocity increases with the steam flow, because of the
increase in cooling water flow.
RESULT
The following table shows the comparison between the design
values (BHEL) and calculated values. Comparison between design
values and calculated values
S.NOPARAMETERSDESIGNCALCULATED VALUE
1C.W inlet temp36 0C32 0C
2C.W temp rise 8.1 0c7.55 0C
3T sat49.2 0C45.7 0C
4Load210 MW209.8 MW
5Condenser duty280.68 KJ/Sec258.315 KJ/Sec
6C.W flow8.5 m3/Sec8.185 m3/Sec
7Velocity of tube1.565 m/s1.507 m/s
8LMTD8.4 0C9.42 0C
9Cleanliness factor72.5%57.33%
10Back pressure89 mm75.473 mm
Since it is more convenient to express enormous amount of
results obtained through c-programme in graphical form, the results
are represented through various graphs
CONCLUSIONIn this book the need of main steam surface condenser
performance analysis in a power plant is discussed.
How the various factor like condenser duty, flow of cooling
water and its velocity, heat transfer coefficients, cleanliness
factor, back pressure and temperatures effect the condenser
performance changes have been seen. For this we have taken the
readings from Dr. NTTPS, stage 2 and drawn various graphs.
In results and discussions how the cleanliness factor and back
pressure of condenser vary with time duration is seen. Next the
effects of inlet temperature, saturation temperature and main steam
on the cleanliness factor, effectiveness, LMTD and heat transfer
coefficients are discussed. From all these results the optimal
conditions for the operation of a condenser are taken. We can also
extend this to know how the calculated values vary from design or
theoretical values.
For condenser performance main problem is fouling and corrosion
when compared to other like tube leakage and air leakage. So to
overcome this problem the online tube cleaning system with the help
of sponge balls is suggested and the working of it is
discussed.
Finally concluding with optimum values for Tin 310C, Tout 390C,
Tsat 420C for getting cleanliness factor around 71%, effectiveness
64% and MTD 8 0C and heat transfer coefficients theoretical 2050
and actual 2850 Kcal/ Hr m2 0C.
REFERENCES
1. POWER PLANT ENGINEERING - P.K.NAG,
2. POWER PLANT ENGINEERING - ARORA & DOMKUNDWAR
3. PERORMANCE AND EFFICIENCY MONITORING - NTPC MANNUAL
4. BHEL MANNUAL
5 WWW. BGRCORP.CO