Direct contact condensers allow exhaust steam and cooling water to mix directly, condensing the steam quickly to the temperature of the cooling water. There are three main types: spray condensers, barometric condensers, and ejector or jet condensers. Advantages include more efficient heat exchange requiring less water, simpler construction making them less costly, and requiring less space. Disadvantages include inability to reuse condensate if impure and lower vacuum efficiency making them unsuitable for larger plants. Spray condensers spray water into steam and circulate cooling water. Barometric condensers rely on static head to compress mixtures. Ejector condensers use kinetic energy of steam to drain mixtures.

1. Direct Contact or Open Condensers
A presentation by:
Farooq Ahmad Shah

2. What are Direct Contact Condensers?
• Exhaust steam and cooling water come in direct contact
and mix together.
• Steam condenses suddenly achieving the temperature of
cooling water.
• Condensate and cooling water are continuously taken
out.
• Used in special cases
▫ When dry cooling towers are used
▫ Geothermal power plants
▫ Plants that use temperature differences in ocean waters
• Mainly three types
▫ Spray condenser
▫ Barometric condenser
▫ Ejector or jet condenser

3. Advantages vs. Disadvantages
• Advantages
▫ Heat exchange through direct contact, thus less water
quantity required.
▫ Construction is simpler thus less costly.
▫ Maintenance is simple and cheap.
▫ Requires small floor space.
• Disadvantages
▫ If condensate contains impurities cannot be reused.
▫ Low vacuum efficiency hence not suitable for larger
plants.
▫ More power required for air pump.

4. Spray Condenser
• Modern direct contact condenser.
• Water is sprayed into the steam.
• Part of the condensate , equal to the turbine
exhaust flow, is sent back as feedwater.
• Rest is cooled in a cooling tower. Cooled water is
sprayed into the turbine exhaust, process is
repeated.
• Continuously circulated cooling water must be
pure.

5. • Mass balance
• Energy balance
• Cooling water to steam ratio
• h2-h3 is larger since large latent heat of
vaporization where as h3-h5 is much smaller.
Spray Condenser

6. • Early type of Direct–Contact Condenser.
• The vacuum is obtained by an air pump that sucks air
out from the top.
• Baffles are used which increases the surface to volume
ratio.
• Has a long vertical tale pipe (at least 10.23m) making it
difficult to access.
• The outlet of the tail pipe must be at least 6” below the
minimum level of the water in the hot valve.
• The condensate cannot be reused in boiler since it is
contaminated by cooling water.
• No need of condensate pump.
Barometric Condenser

7. • The cooling water is made to
cascade down a series of baffles in
the form of water curtains or
sheets.
• The static head compresses the
mixture to atmospheric pressure
and thus replaces the pump.
• The steam condenses and the
mixture goes down a tail pipe to the
hot well.
• The larger the H the easier it is for
the condensate to flow down to the
hot well.
Barometric Condenser

8. Jet or Ejector Condenser
• A kind of direct contact
condenser in which cooling
water and steam mix in a
series of combining cones.
• Kinetic energy of steam is
expended to drain off the
condensate and cooling water
from the condenser.
• It reduces the tail pipe height
in barometric condenser.
• Removes the need of air pump.
• The condensate cannot be
reused in boiler since it is
contaminated by cooling
water.
Parallel flow
Counter flow

9. • Water enters from the top through nozzles. Its is
surrounded by guide cones.
• Steam entering from the side is guided on to the
surface of water through guiding cones.
• Due to decreasing area of guide cones, potential
energy is converted into kinetic energy.
• Decrease in potential energy causes pressure drop
resulting in suction.
• Suction pulls more and more steam for
condensation.
• Water and condensate then enter diverging section. Here velocity decreases and
pressure increases.
• Built up pressure enable the mixture of condensate and water to discharged
automatically in the hot well.
• A non return valve prevents sudden rush of water from hot well into the turbine
in event of a failure in supply of injection.
Jet or Ejector Condenser

10. Thank you.