2. Definition
Condenser is a device in which steam is
condensed to water at a pressure less than
atmosphere.
Condensation can be done by removing heat
from exhaust steam using circulating cooling
water
A condenser is basically steam to water
exchanger in which heat from exhaust steam
is transferred to circulating cooling water
3. Function
To reduce the turbine exhaust pressure so as
to increase the specific output and hence
increase the plant efficiency and decrease the
specific steam consumption.
To condense the exhaust steam from the
turbine and reuse it as pure feed water in the
boiler. Thus only make up water is required
to compensate loss of water
4. Advantages of condensers in steam power plant
1) High pressure ratio provides larger enthalpy drop
2) Work output per kg of steam increases and hence
specific steam consumption decreases
3) Condensate can be reused as hot feed water to
the boiler. This reduces the time of evaporation
and hence fuel economy
4) No feed water treatment is required and hence
reduces the cost of the plant
5) The formation of deposits in the boiler surface
can be prevented with the use of condensate
instead of feed water from outer sources
5. Elements of steam condensing plant
1) Condenser
2) Air extraction pump
3) Condensate extraction pump
4) Circulating cooling water pump
5) Hot well
6) Cooling tower
7) Make up water pump
8) Boiler feed pump
7. Classification of condensers
1) Jet condensers (or) mixing type
a) Parallel flow type (Low level)
b)Counter flow type (High & Low levels)
c) Ejector type
2) Surface condensers (or) non-mixing type
a)Down flow type
b) Central flow type
c) Inverted type
d) Regenerative type
e) Evaporation type
9. Comparison of jet & surface condensers
Jet Condensers Surface Condensers
1) Cooling water and steam are mixed up
2) Low manufacturing cost
3) Requires small floor space
4) The condensate cannot be used as feed
water to boiler unless it is free from
impurities
5) More power is required for air pump
6) Less power is required for water pump
7) Requires less quantity of cooling water
8) The condensing plant is simple
9) Less suitable for high capacity plants
due to low vacuum efficiency
10)Lower upkeep
1) Cooling water & steam aren’t mixed up
2) High manufacturing cost
3) Requires large floor space
4) The condensate can be used as feed
water to boiler as it is not mixed with
cooling water
5) Less power is required for air pump
6) More power is required for water pump
7) Requires large quantity of cooling
water
8) The condensing plant is complicated
9) More suitable for high capacity plants
as vacuum efficiency is high
10)Higher upkeep
10. Jet condensers
Jet condensers are used in small capacity
units where clean fresh water is available in
plenty.
In jet condensers, water is in direct contact
with exhaust steam. Hence these are also
called direct contact type (or) mixed type
11. Advantages & disadvantages of Jet condensers
Advantages
1) As a result of effective mixing, it requires less circulating
cooling water
2) Equipment is simple and occupy less space
3) Maintenance is cheap
Disadvantages
1) Not suitable for higher capacities
2) Condensate cannot be used as feed water to boiler
3) Air leakages are more
4) Requires larger air pump
5) Less vacuum is maintained
12. Surface condensers
Surface condensers are used in large
capacity plants
In surface condensers, exhaust steam and
water do not mix together. Hence they are
also called indirect contact type (or) non-mixed
type
13. Advantages & disadvantages of surface condensers
Advantages
1) Can be used for large capacity plants
2) High vacuum can be created
3) Condensate is free from impurities and can be reused as
feed water to boiler
4) Impure water can also be used as cooling medium
5) Air leakage is comparatively less, hence less power is
required to operate air pump
Disadvantages
1) Design is complicated and costly
2) High maintenance cost
3) Occupies more space
4) Requires more circulating water
20. Inverted type Surface condenser
In this type of jet condensers, steam enters
at the bottom of the shell and flows
upwards.
Air extraction pump is placed at the top.
The condensate flows down and removed at
the bottom where condensate pump is
located.
21. Regenerative type Surface condenser
The condensers used in a regenerative method of heating
the condensate are called regenerative type condensers.
In this type of condensers, the condensate after leaving
the condenser is passed through the exhaust steam where
the temperature is increased.
The condensate at high temperature can be reused as
feed water to the boiler.
This increases the efficiency of the plant and minimise
the fuel consumption.
23. Sources of air in Condenser
1) Air leakage from atmosphere at the joints of
the parts which are internally under a
pressure less than atmosphere
2) Air accompanied with steam from the
boiler into which it enters dissolved with
feed water
3) In jet condensers, a little quantity of air
accompanies the injection of water in which
it is dissolved
24. Effects of air leakage in a condenser
1) Lowered thermal efficiency
2) Increased requirement of cooling water
3) Reduced heat transfer
4) Corrosion
25. Methods of obtaining maximum vacuum
1) Air pump
2) Steam air ejector
3) De-aerated feed water
4) Air tight joints
27. Vacuum Efficiency
It is defined as the ratio of actual
vacuum to the maximum obtainable
vacuum.
Vacuum efficiency = Actual vacuum
Maximum
obtainable
vacuum
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Vacuum efficiency = Actual Vacuum
Absolute
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pressure
of steam
Barometer
Pressure
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28. Condenser Efficiency
It is defined as the ratio of difference
between the outlet and inlet temperatures
of cooling water to the difference between
the temperature corresponding to the
vacuum in the condenser and inlet
temperature of cooling water
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Rise in temperature
of cooling water
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Inlet temperature
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Temperature
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of cooling water
corresponding
to vacuum
Condenser efficiency =
