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
