Steam Condensers , How does it work and it's types with some technical details .

1. STEAM CONDENSERS
Mohamed MahmoudBY :
Department : Mechanical power
Eng : Mohamed Hamed

2. Introduction :
• If the pressure of the exhaust steam reduced below the
atmospheric pressure and hence its energy, partially of fully, can not
be reutilized, than this phenomenon is called Steam
Condensation.
• The heat transfer device or unit used to condense a substance
from its gaseous to its liquid states called Steam Condenser.
• The condensed Steam is called Condensate and can be again
returned to Boiler. It saves the cost of water.
Eng : Mohamed Hamed

3. About Condenser :
• The latent heat is given up by the substance, and will transfer to the
condenser coolant.
• Condensers are typically heat exchangers which have various designs
and come in many sizes ranging from rather small (hand-held) to very
large industrial scale units used in plant processes. For example,a
refrigerator uses a Condenser to get rid of heat extracted from the
interior of the unit to the outside air. Condensers are used in air
conditioning, industrial chemical processes .
• Such as distillation, steam power plants and other heat-exchange
systems. Use of cooling water or surrounding air as the coolant is
common in many condensers. The main use of a condenser is to receive
exhausted steam from a steam engine or turbine and condense the steam.
The benefit being that the energy which would be exhausted to the
atmosphere is utilized .
• A steam condenser generally condenses the steam to a pressure
significantly below atmospheric. This allows the turbine or engine to do
more work.The condenser also converts the discharge steam back to feed
water which is returned to the steam generator or boiler. In the condenser
Eng : Mohamed Hamed

4. The main objectives of The
condenser :
A. To maintain low pressure (below
atmospheric pressure) at the outlet of the
steam turbine so as to obtain the
maximum possible energy.
B. To supply pure feed water to the hot well
and from hot well the water is again
pumped to the boiler with the help of boiler
feed pump.
Eng : Mohamed Hamed

5. Eng : Mohamed Hamed

6. Working :
• The steam condenser receives the exhaust steam from
one end and comes in contact with the cooling water
circulated within it form the cooling tower. As the low
pressure steam comes in contact with the cooling water,
it condenses and converts into water. It is connected to
the air extraction pump and condensate extraction
pump. After the condensation of steam, the condensate
is pumped to the hot well with the help of condensate
extraction pump. The air extraction pump extracts the air
from the condenser and creates the vacuum inside it.
The vacuum created helps in the circulation of cooling
water and flow of condensate downward.
Eng : Mohamed Hamed

7. Factors affecting Condenser
Performance :
o Condensate Sub cooling
o Air In-Leakage
o Circulating Water Temperature
o Pressure Drop
Eng : Mohamed Hamed

8. Elements of Steam Condensing Plant :
The principle requirements of steam condensing
plant :
Eng : Mohamed Hamed

9. Elements of a steam condensing
plant :
1. Condenser: It is a closed vessel used to condense the steam. The low pressure
steam gives off its heat to the coolant (here water from cooling tower) and gets
converted into water during the process of condensation.
2. Condensate Extraction Pump: It is a pump which is installed in between the
condenser and hot well. It transfers the condensate from the condenser to the hot
well.
3. Hot Well: It is a sump that lies in between the condenser and boiler. It receives the
condensate from the condenser by condensate pump. The feed water is
transferred from the hot well to the boiler.
4. Boiler Feed Pump: It is a pump installed in between the hot well and boiler. It
pumps the feed water from the hot well to the boiler. And this is done by increasing
the pressure of condensate above boiler pressure.
5. Air Extraction Pump: It is a pump used to extracts or removes the air from the
steam condenser.
6. Cooling Tower: It is a tower which contains the cold water and this water is made
to circulate within the condenser for cooling of steam.
7. Cooling Water Pump: It is a pump lies in between the cooling tower and
condenser. It circulates the cooling water through the condenser.Eng : Mohamed Hamed

10. Advantages and Disadvantages of
Steam Condensers :
o Advantages :
1) It increases the efficiency of the plant.
2) It reduces the back pressure of the steam and as a result of this, more work can
be done.
3) It reduces the temperature of the exhaust steam and this allows to obtain more
work.
4) It allows the reuse of condensate for the feed water and hence reduces the cost of
power generation.
5) The temperature of the condensate is more than the feed water. This reduces the
supply of heat per kg of steam.
o Disadvantages :
1) Require large quantity of cooling water.
2) System is complicated, costly and requires high maintenance cost.
3) Require large floor space since it is bulky.
Eng : Mohamed Hamed

11. Classification of Steam Condenser
:
o According to the Cooling Action:
1. Jet condensers or mixing type condenser
.
2. Surface condenser or non-mixing type
condenser .
o According to the type of flow:
1. Parallel flow
2. Counter flow
3. Cross flow Eng : Mohamed Hamed

12. Classification of Steam Condenser
:
Eng : Mohamed Hamed

13. COMPARISION :
1) Cooling water and steam are mixed up
2) Requires small floor space
3) The condensate cannot be used as feed
water to boiler unless it is free from
impurities
4) More power is required for air pump
5) Less power is required for water pump
6) Requires less quantity of cooling water
7) The condensing plant is simple
8) Less suitable for high capacity plants due
to low vacuum efficiency
1) Cooling water & steam aren’t mixed up
2) Requires large floor space
3) The condensate can be used as feed
water to boiler as it is not mixed with
cooling water
4) Less power is required for air pump
5) More power is required for water pump
6) Requires large quantity of cooling water
7) The condensing plant is complicated
8) More suitable for high capacity plants as
vacuum efficiency is high
Jet condensers
`
Surface
condensers
Eng : Mohamed Hamed

14. (1) Jet Condenser :
Jet condenser is a condenser in which the condensate
gets mixed with the cooling water. That’s why it is also
called as mixing type condenser .
This type of condenser is used sometime because it lost
some of the condensate and requires high power for the
pump during the process of condensation .
In jet condenser, as the condensate is not free from the
salt, so it cannot be used as feed water for the boiler. It can
be used at the place where sufficient amount of good
quality water is available.
The jet condensers may be classified as follows:Eng : Mohamed Hamed

15. (i) Low level jet condensers (Parallel
flow type) :
o In this condenser water is sprayed
through jets and it mixes with steam. The
air is removed at the top by an air pump.
In counter flow type of condenser the
cooling water flows in the downward
direction and the steam to be condensed
moves upward
Eng : Mohamed Hamed

16. (i) Low level jet condensers
(Parallel flow type) :
Eng : Mohamed Hamed

17. (ii) High level or Barometric
condenser :
o a high-level jet condenser. The condenser
shell is placed at a height of 10.33 m
(barometric height) above the hot well. As
compared to low
level jet condenser. This condenser does not
flood the engine if the water extraction pump
fails. A
separate air pump is used to remove the air.
Eng : Mohamed Hamed

18. (ii) Barometric condenser :
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19. (iii) EJECTOR JET CONDENSER :
In this condenser cold water is discharged under
a head of about 5 to 6 m through a series of
convergent nozzles. The steam and air enter the
condenser through a non-return valve. Mixing with
water condenses steam. Pressure energy is partly
convert into kinetic energy at the converging
cones. In the diverging come the kinetic energy is
partly converted into pressure energy and a
pressure higher than atmospheric pressure is
achieved so as to discharge the condensate to the
hot well.
Eng : Mohamed Hamed

20. (iii) EJECTOR JET
CONDENSER :
Eng : Mohamed Hamed

21. Advantages and disadvantages of jet
condensers:
o Advantages:
1. Less quantity of cooling water is required to condense the steam.
2. Simple in construction and low cost.
3. Does not required cooling water pump.
4. Less space is required.
5. Low maintenance cost.
o Disadvantages :
1. The condensate is a wet.
2. Less suitable for high capacity plants.
3. Large length of pipes required, hence piping cost is high.
4. Loss of vacuum due to leakage of air from long piping.
Eng : Mohamed Hamed

22. (2) Surface condenser :
o In surface condensers there is no direct contact
between the steam and cooling water and the
condensate can be re-used in the boiler: In such
condenser even impure water can be used for cooling
purpose whereas the cooling water must be pure in jet
condensers. Although the capital cost and the space
needed is more in surface condensers but it is justified
by the saving in running cost and increase in efficiency
of plant achieved by using this condenser. Depending
upon the position of condensate extraction pump, flow of
condensate and arrangement of tubes the surface
condensers may be classified as follows:
Eng : Mohamed Hamed

23. Surface condenser :
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24. (i) Down flow type :
o In Down flow surface condenser, the steam enters
at the top of the condenser and flows downwards
over the tubes due to the gravity and air extraction
pumps. The condensate gets collected at the
bottom and then pumped with the help of
condensate extraction pump. The pipe of dry air
extraction pump is provided near the bottom and
ita is covered by baffle plates so as to prevent the
entry of the condensate into it.
The steam in down flow condenser flows
perpendicular to the direction of flow of cooling
water, so it is also called as cross-surface
condenser.
Eng : Mohamed Hamed

25. (i) Down flow type :
Eng : Mohamed Hamed

26. (ii) Central flow condenser :
o In central flow condenser, the steam enters at the
top of the condenser and flows in downward
direction. In this the suction pipe of the air
extraction pump is provided in the center of the
tube nest as shown in the figure. Due to this
placement of the suction pipe in the center of the
tube nest, the exhaust steam flows radially inward
over the tubes towards the suction pipe. The
condensate is collected at the bottom of the
condenser and pumped to the hot well.
We can say that it is the improved form of the
down flow surface condenser.
Eng : Mohamed Hamed

27. (ii) Central flow condenser :
Eng : Mohamed Hamed

28. (iii) Evaporative :
o In evaporative surface condensers, the steam
enters at the top of the condenser in a series of
pipes over which a film of cold water is falling. At
the same time, current of air is made to circulate
over the film of water. As the air circulates over
the water film, it evaporates some of the cooling
water. As a result of this rapid evaporation, the
steam circulating inside the series of pipes gets
condensed. Remaining cooling water that left is
collected at an increased temperature and
reused. It is brought to the original temperature
by adding required quantity of cold water.
Eng : Mohamed Hamed

29. (iii) Evaporative :
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30. (iv) Regenerative :
o In regenerative surface condensers, the
condensate is heated by the use of
regenerative method. In that the condensate is
passed through the exhaust steam coming out
from the turbine or engine. This raises its
temperature and it is used as the feed water
for the boiler.
Eng : Mohamed Hamed

31. (vi) Inverted Flow Type :
o This type of condenser has the air suction
at the top; the steam after entering at the
bottom rises up and then again flows down to
the bottom of the condenser, by following a
path near the outer surface of the condenser.
The condensate extraction pump is at the
bottom.
Eng : Mohamed Hamed

32. ADVANTAGES AND DISADVANTAGES OF
A SURFACE CONDENSER:
o The various advantages of a surface condenser are as
follows:
1. The condensate can be used as boiler feed water.
2. Cooling water of even poor quality can be used because the
cooling water does not come indirect contact with steam.
3. High vacuum (about 73.5 cm of Hg) can be obtained in the
surface condenser. This increasesthe thermal efficiency of
the plant.
• The various disadvantages of' the surface condenser are
as follows:
1. The capital cost is more.
2. The maintenance cost and running cost of this condenser
is high.
3. It is bulky and requires more space.
Eng : Mohamed Hamed

33. REQUIREMENTS OF A MODERN
SURFACE CONDENSER:
o The requirements of ideal surface condenser used
for power plants are as follows:
1. The steam entering the condenser should be evenly
distributed over the whole cooling surface of the
condenser vessel with minimum pressure loss.
2. The amount of cooling water being circulated in the
condenser should be so regulated that
thetemperature of cooling water leaving the
condenser is equivalent to saturation temperature of
steam corresponding to steam pressure in the
condenser. This will help in preventing under cooling
of condensate.
3. The deposition of dirt on the outer surface of tubes
should be prevented.
Eng : Mohamed Hamed

34. 4. There should be no air leakage into the
condenser because presence of air destroys
the vacuumin the condenser and thus
reduces the work obtained per kg of steam. If
there is leakage of air into the condenser air
extraction pump should be used to remove
air as rapidly as possible.
Eng : Mohamed Hamed

35. Condenser Efficiency :
1. It is defined as the ratio of the difference
between the outlet and inlet temperatures
of cooling
2. water to the difference between the
temperature corresponding to the vacuum in
the condenser
3. and inlet temperature of cooling water, i.e.,
Eng : Mohamed Hamed

36. Effects of Air Leakage :
1) It reduces the vacuum pressure in the
condenser.
2) Since air is a poor heat conductor,
particularly at low densities, it reduces the
rate of heat transmission.
3) It requires a larger air pump. Moreover, an
increased power is required to drive the
pump.
Eng : Mohamed Hamed

37. AIR PUMPS :
Used to remove both
condensate and the air
from the condenser.
These may be of type:
i) Reciprocating
ii) Rotary
Used only to
remove moist air.
These may be of
type:
i) Reciprocating
ii) Rotary
WET AIR PUMP DRY AIR PUMP
Eng : Mohamed Hamed