TOPIC OF APPLIED THERMODYNAMICS: ANALYSIS OF CONDENSER OPERATION VACUUM CREATION DALTONS LAW OF PARTIAL PRESSURE, SOURCES OF AIR IN THE CONDENSER, EFFECT OF AIR LEAKAGE INTO CONDENSER,

1. ANALYSIS OF
CONDENSER
OPERATION
PRESENTED BY : SUMIT WADEWALE
: MECHANICAL ENGINEERING
: ROLL NO : 629
SUB: APPLIED THERMODYNAMICS -I
BAJAJ INSTITUTE OF TECHNOLOGY, WARDHA

2. VACUUM CREATION
 When steam condenses in a closed vessel, the
vapour phase of working substance (water)
changes to liquid phase, and thus its specific
volume reduces to more than one thousand
times. Due to change in specific volume, the
absolute pressure in the condenser falls below
the atmospheric pressure and high vacuum is
created.

3. This lower pressure in the condenser permits maximum
expansion of steam in the turbine, and more work is
developed. The minimum pressure that can be attained
depends on the temperature of condensate and air present
in the condenser.
The term vacuum means the pressures below the
atmospheric pressure. The vacuum in the condenser is
generally measured in mm of mercury (Hg). The vacuum is
the negative gauge pressure and is equal to the differences
of barometric pressure and absolute pressure in the
condenser.

5. The absolute pressure in the condenser
= atmospheric pressure – vacuum gauge pressure
= barometer reading – vacuum gauge reading
The vacuum is usually referred to a standard atmospheric
pressure as 101.325 kPa or 760 mm of Hg, i.e.

6. At any barometric reading other than standard reading of
760 mm of Hg, the vacuum gauge reading is corrected to
standard barometric reading as
corrected in mm of Hg =
Standard barometer reading –
(Actual barometer reading – vacuum gauge reading )
The absolute pressure in condenser can be determined as
Pabs = 760 mm – corrected vacuum in mm of
Hg

7. DALTONS LAW OF PARTIAL
PRESSURE
For a mixture of non reactive gases, the total
(mixture) is given by
Where Pi is the pressure of ith gas component at the mixture
temperature T and volume V.

8. According to Dalton’s law, the total pressure of a non-
reactive mixture is equal to sum of partial of its components, if
each component would occupy the same volume alone at the
mixture temperature.
the condenser has a mixture of wet steam and air. The
total pressure p in the condenser is the sum of partial pressure
of steam, Psat and air Pa.
The saturation pressure of steam Psat can be obtained from the
steam table at condensate (saturation) temperature.
According to Dalton’s law,
P = psat + pa
or pa = p - psat

9. With the help of partial pressure of air, the mass of air can be
determined as,
Where, V is the volume of condenser, Tsat is the
condensate temp and Ra is characteristic gas constant of
air which is equal to 287 J/KgK

10. In the steam condenser, a mixture of steam and air is
present. Therefore, the absolute pressure in the
condenser is the sum of partial pressures of steam and air.
The presence of air in the condenser disturbs the vacuum
is less than that could be attained in the condenser, if only
steam is present. If no airt is present in the condenser
then absolute pressure bin the condenser is the
saturation pressure of steam and thus the maximum
vacuum would be attained.

11. Where pg is the actual vacuum
= barometric pressure – absolute pressure in
condenser
= patm – p
Maximum possible vacuum
Pg, max = barometric pressure – sat. pressure of steam corresponding to
condensate temperature
= patm - psat
The vacuum efficiency is defined as the ratio of
actual vacuum to the maximum possible vacuum.

12. SOURCES OF AIR IN THE
CONDENSER
All types of condensers require air extraction pump to remove the air present in the
condenser. The main sources of air present in the condenser are the following:
 the ambient air leaks to the condenser chamber at the joints and glands
which are internally under pressure lower than that of ambient. It can be
reduced by taking utmost care while designing and making vacuum joints.
 another source of air is dissolved air with feed water. The dissolved air in
the feed water enters into the boiler and it travels with steam into the
condenser. Its quantity depends upon the quality of feed water.
 In case of jet condenser, some air comes in with the injected water in which
it is dissolved.

13. EFFECT OF AIR LEAKAGE INTO
CONDENSER
The presence of air in the condenser is a far serious concern. It affects
the performance of the condenser to a great extent, thereby, the
performance of steam power plant. The presence of air into the
condenser puts the following effects:
 the presence of air lowers the vacuum in the condenser.
Thus the back pressure of plant increases, and consequently,
the work output of the turbine reduces.

14. the presence of air also lowers the partial pressure of steam
and hence lower saturation temperature. The steam with lower
saturation temperature has higher latent heat. A large quantity
of cooling water is required to get the desired result in the
condenser.
 Air forms the film adjacent to the tube surface in the
condenser. Air has very poor thermal conductivity. Hence, the
rate of heat transfer from vapour to cooling medium is reduced.
The presence of air in the condenser corrodes to the metal
surfaces. Therefore, the life of condenser is reduced.

15. THANK YOU